Spraying fuel directly into a gasoline engine’s combustion chambers instead of its intake ports isn’t a new idea—the World War II

ME109 German fighter plane used it. The Japanese-market Mitsubishi Galant was the

first car to combine direct injection with computer-controlled injectors in 1996. Direct injection (DI) costs more than port injection because the fuel is sprayed at 1500–3000 psi

rather than 50–100 psi, and the injectors must withstand the pressure and heat of

combustion.

But DI has a key benefit: By injecting fuel directly into the cylinder during the

compression stroke, the cooling effect of the

vaporizing fuel doesn’t dissipate before the spark plug fires. As a result, the engine is more resistant to detonation—a premature

and near-explosive burning of the fuel, producing a knocking sound and pounding

the pistons with pressure and heat—and can therefore operate with a higher compression

ratio—about 12:1 instead of 10.5:1. That alone improves fuel economy by two to three

percent.

And DI also offers the possibility of lean combustion because the fuel spray can be

oriented so that there is always a combustible mixture near the spark plug.

That could yield five percent more efficiency.

Several European carmakers are already using this lean-burn strategy. Unfortunately,

lean combustion causes higher tailpipe emissions of NOx (oxides of nitrogen), which

run afoul of America’s tighter limits. Catalysts that can solve this problem don’t

like the high sulfur content in American gasoline. New catalysts promise to reduce

emissions. Meanwhile, expect direct injection to become universal by 2020.

Modern engines achieve power levels that we could only dream about 20 years ago. The

downside is that during routine driving, most engines are loafing—and 300-hp engines are inefficient when they’re only putting out the 30 ponies needed to push an average sedan

down the highway. When an engine’s throttle is barely cracked open, there’s a strong

vacuum in the intake manifold. During the

intake stroke, as the pistons suck against this vacuum, efficiency suffers.

The classic solution to this problem is to make an engine smaller. A small engine

works harder, running with less vacuum, and is consequently more efficient. But small engines make less power than big ones.

To make big-engine power with small-engine fuel economy, many companies are turning to

smaller engines with turbochargers, direct fuel injection, and variable valve timing.

These three technologies work together to their combined benefit.

Forcing additional air into an engine’s combustion chambers with a turbocharger definitely boosts power; car manufacturers have been doing this for years. But in the past, in order to avoid harmful detonation,

turbocharged engines needed lower compression ratios, which compromised

efficiency.

As we’ve seen, direct fuel injection helps solve this problem by cooling the intake

charge to minimize detonation. Second, if the variable valve timing extends the time when

both the intake and the exhaust valves are open, the turbocharger can blow fresh air through the cylinder to completely remove

the hot leftover gases from the previous combustion cycle. And since the injectors

squirt fuel only after the valves close, none of it escapes through the exhaust valve.

The first engine in America with all three of these elements was the base 2.0-liter four-

cylinder in the 2006 Audi A4. It had a 10.5:1 compression ratio—as high as many naturally

aspirated engines—despite a peak boost pressure of 11.6 psi. It produced 200

horsepower and 207 pound-feet of torque.

Ford’s EcoBoost system is nothing more than direct injection and turbocharging. Dan

Kapp, Ford’s director of advanced powertrain engineering, says that this technology will

spread across the company’s cars and trucks. “Nothing else delivers double-digit improvements in fuel efficiency at a

reasonable cost.”

In the future, Ford expects to replace its 5.4-liter V-8 with a 3.5-liter EcoBoost V-6; its 3.5-liter V-6 with a 2.2-liter EcoBoost inline-four;

and its 2.5-liter inline-four with a 1.6-liter

EcoBoost inline-four. In each downsizing, peak power should be similar, low-end torque should be about 30 percent greater, and fuel economy should be 10-to-20 percent higher.

The only downside will be an added charge of $1000 or so to the price of DI-turbo vehicles

to pay for the additional hardware. BMW, Mercedes, Toyota, and Volkswagen are planning similar engines—some using

superchargers instead of turbochargers. Turbocharging with direct injection will

continue to expand. Later in the decade, we will see a second generation of these engines, using higher boost pressures. This will allow

further engine downsizing to achieve an additional 10-percent efficiency

improvement. Making this happen will require cooled exhaust-gas recirculation to

control detonation and either staged or variable-geometry turbos to limit customary lag. Those technologies are already in use on

diesel engines, but a gas engine’s higher exhaust temperatures pose durability problems that must be solved before

carmakers can deploy these technologies.

Another way to improve the efficiency of a big engine is to turn off some of its cylinders. Since the throttle must be opened farther to

get the same power from the remaining cylinders, intake-manifold vacuum goes down

and efficiency goes up.

In real-world driving, this can produce a fuel-economy improvement of five percent, at a

fairly low cost. The technology is particularly cost effective on pushrod, two-valve engines,

which is why we’ve seen variable displacement on GM and Chrysler V-8s.

Honda uses variable displacement on its 24-valve V-6 engines, but the additional

hardware to close the multiplicity of valves adds cost. Moreover, shutting off some

cylinders on a V-6 generates more vibration and noise problems than it does with a V-8 because V-6s have coarser firing impulses and poorer inherent balance. The active

engine mounts and variable intake manifolds needed to solve these problems add further

costs.

The simplest implementation of variable valve timing started about 25 years ago, using a two-position advance or retard of

either an engine’s intake or exhaust camshaft to better match the engine’s operating

conditions. Today, most four-valve-per-cylinder DOHC engines have continuously

variable phasing on both the intake and the exhaust camshafts.

About 20 years ago, Honda introduced a more elaborate approach with its VTEC system, which shifted between two (and

later, three) separate sets of cam lobes—one for high-speed operation and one for low.

VTEC can also simply turn off one of a cylinder’s two intake valves under light loads.

In 2001, BMW went a step further with its Valvetronic system, which can continuously vary the opening stroke of the intake valves

to optimize engine power and efficiency. Furthermore, this extensive control of the intake valves serves to replace a throttle

plate, which eliminates vacuum and therefore reduces pumping losses.

Though they provide efficiency benefits, variable-lift systems are complex and

expensive. Development continues on purely electronic systems that could replace

camshafts and simply open and close an engine’s valves according to a computer. But electronic valve-opening mechanisms are also

costly and consume significant power. GM Powertrain VP Dan Hancock suggests that a

two-stage valve-lift mechanism can deliver 90 percent of the benefits of fully variable lift.

Moreover, Ford’s Kapp says that the benefits of variable valve lift are limited when combined with EcoBoost (DI turbo).

On the other hand, BMW, with its latest single-turbo, direct-injection 3.0-liter inline-

six (N55) that’s replacing the twin-turbo (N54) across the lineup, has done just that by

adding Valvetronic to its DI-turbo configuration. Combined with the move from a six-speed automatic to an eight-speed, the change is said to provide 10 percent more

miles per gallon.

Perhaps the answer will be Fiat’s Multiair system, a hydraulically operated variable-lift

design that is far less complex than mechanical systems such as BMW’s. Expect to soon see Multiair on upcoming Chrysler

vehicles.

This technology, abbreviated as HCCI, is essentially a combination of the operating

principles of a gas engine and a diesel. When high power is required, an HCCI engine

operates like a conventional gasoline engine, with combustion initiated by a spark plug. At more modest loads, it operates more like a diesel, with combustion initiated simply by

the pressure and heat of compression.

In a diesel engine, combustion starts when the fuel is injected with the piston near the

top of the compression stroke, and the combustion is controlled by the speed at

which the fuel is injected. With HCCI, however, the fuel has already been injected

and mixed with the air before the compression stroke begins.

Since compression alone initiates combustion, it’s more of a big bang than even

a diesel’s hard-edged power stroke. Making the engine sturdy enough to avoid blowing apart makes an HCCI at least as heavy as a

diesel. The key is achieving sufficient combustion control so that the HCCI cycle can be used over as wide a speed and load

range as possible to reap the efficiency benefits.

One way to extend the HCCI mode is to employ a variable compression ratio, which is what Mercedes has done on its experimental Dies-Otto engine. But other engineers, such as GM’s Hancock, would like to avoid that

complication. “To make HCCI work, we need very good control of the combustion process with a faster engine-control computer and

combustion-pressure feedback.”

It all sounds complicated, but the payoff can be a 20-percent improvement in fuel economy

without the particulate traps and the NOx catalysts that diesels need. That’s enough to

sustain interest among the major players. Hancock guesses that HCCI might make it into production by the end of this decade, perhaps as an efficient engine for a plug-in

hybrid because it only needs to run over a small rpm band to power a generator.

Turning off an engine when stopped at a light can definitely save fuel. It’s easy to program an engine-control computer to shut down an engine when the vehicle speed drops to zero and restart it when the driver removes his foot from the brake pedal. The starter and the battery might need to be beefed up to withstand more frequent use, but that’s no

technical challenge.

Mazda has come up with a simpler method of accomplishing the stop-start feat. In its

system, called i-stop, the computer stops the engine when one piston is just past the top of

the compression stroke. To restart, fuel is injected into the cylinder, the spark plug is

fired, and the engine is instantly running again.

Unfortunately, while these systems might save as much as five percent of fuel

consumption in an urban setting, the EPA’s test cycles demonstrate only a one-percent

benefit, due to limited idle times. As a result, most manufacturers are reluctant to invest in

a technology that doesn’t do much to help them meet their CAFE goals, no matter the

real-world benefit.

One of the downsides of corn-based ethanol is that current flex-fuel engines generally aren’t taking full advantage of E85’s 95- octane rating. But it’s easy to envision a

second-generation DI turbo engine that runs higher boost pressure when burning E85.

Such an engine could be half the size of a current naturally aspirated powerplant, with substantially higher fuel economy. And when

fueled with pure gasoline, the computer would simply dial back the boost. The engine

would lose some power but without compromising durability or fuel efficiency.

A more radical way to harness ethanol’s higher octane rating is the “ethanol boosting system” (EBS) being worked on by several

MIT professors as well as Neil Ressler, Ford’s former top technology executive.

The concept is simple. Start with a DI-turbo engine and add a conventional port-fuel-injection system to it. Then add a second, small fuel tank and fill that one with E85. During modest loads, the engine runs on

gasoline and port injection. But when you call for more power and the boost comes up, the

DI system injects E85. Not only does E85 have a higher octane rating than gasoline, it also has more cooling effect. This allows safe

operation above 20 psi of boost.

Ford has shown serious interest in the project. For a pickup application, a twin-

turbo 5.0-liter EBS engine might replace the

6.7-liter diesel in the Super Duty truck. It would develop the same power and torque,

achieve similar fuel efficiency, and be cheaper to build because it doesn’t need any

of the diesel’s expensive exhaust after-treatment.

In normal use, E85 consumption would be less than 10 percent of the gasoline

consumption. Therefore, you save a lot of gas while consuming only a little ethanol. The

EBS engine seems technically sound and has already survived preliminary tests. We expect

that it will make it into production in some form within the next five years.

Imaginative new engine concepts are a dime a dozen. Our technical director usually keeps

a fat file full of them labeled “crackpot engines.” Most never even reach the

prototype stage. And even the ones that do get built generally flame out due to problems involving durability, construction complexity, or efficiency. The very few that get beyond

that stage face an uphill battle with automakers who have billions invested in building conventional engines of proven

reliability and performance.

One of the few new engine concepts that looks promising is the OPOC two-stroke from

EcoMotors. OPOC stands for “opposed piston opposed cylinder.” To visualize the engine,

start with a horizontally opposed four-cylinder like the Subaru Legacy’s. Then

extend the cylinders and lose the cylinder heads to make room for a second set of pistons within each cylinder that move

opposite of the conventional pistons. Long connecting rods transfer the motion of these

additional pistons to throws on the crankshaft.

As in a typical two-stroke, breathing occurs through ports in the sides of the cylinders.

But in the OPOC engine, the intake and exhaust ports are at opposite ends of the

cylinders. As the pistons move, the exhausts are uncovered before the intakes and

turbochargers blow air through the cylinders to push out the exhaust gas and fill them with

clean air. Since the engine needs positive pressure to do this, the turbochargers have electric motors to power them at low rpm

when exhaust energy is low.

Though the first OPOC engines are Âdiesels, the concept can also work with gasoline.

Either way, the direct-fuel injector is in the

middle of the cylinder where the two Âpiston crowns almost meet, and that’s where a

spark plug would be in a gas version.

If the OPOC’s design seems radical, it has solid people backing it. The engine designer

is Peter Hofbauer, Volkswagen’s former chief engine engineer. The EcoÂMotors CEO is

Don Runkle, a former top executive at Delphi and GM. The president is John Coletti, the

legendary former boss of Ford’s SVT division.

And exhaust-maker extraordinaire, Alex Borla, is on the board of directors. Much of the company’s funding comes from Vinod

Khosla, a Silicon Valley mega-investor.

Thus far, prototypes of the OPOC engine have delivered 12-to-15-percent better

efficiency than conventional piston engines, due primarily to the absence of cylinder

heads, eliminating a large surface through which the heat of combustion is lost to the coolant, and the absence of the valvetrain, which reduces friction by some 40 percent.

Furthermore, because each two- cylinder, four-piston module is perfectly balanced, it is

possible with a four-cylinder version of the engine to completely decouple one cylinder pair under light loads. This not only reduces

pumping losses but also completely eliminates the friction from the disabled cylinder, improving fuel efficiency by an

additional 15 percent.

Thus far, Coletti says that there are no obvious problems: “Emissions look good, and so does oil consumption. There’s nothing that has me worried.” Runkle adds that due to the

fewer parts—no heads or valvetrain—the

engine should be 20-percent cheaper to build than a modern V-6. “We’re working on two

engine families. The EM100d is a diesel with a 100-millimeter bore developing 325 horsepower, and the EM65ff has a 65-millimeter bore and makes about 75 horsepower in two-cylinder form on

gasoline.”

The engine is years away from production. For a small, growing company without a huge

investment in conventional engines—think Chinese or Indian—the OPOC engine is

attractive. A military contract would also pave the way toward civilian acceptability.

As mentioned, being able to change a running engine’s compression ratio would

help to make HCCI work. Most such schemes involve somehow changing either the stroke

of an engine’s piston or the distance from the crankshaft to the combustion chamber. Both approaches are mechanically problematic.

The clever engineers at Lotus have come up with a simpler way to change an engine’s

compression. They’ve created a cylinder head that has a movable section—they call it a

puck—that can extend into the combustion chamber. With the puck fully retracted, the compression ratio is 10:1. When extended into the head, it reduces the combustion-

chamber volume, thereby increasing the ratio to as high as 40:1. There’s room for this puck

because the engine, which Lotus calls

“Omnivore,” is a two-stroke without any valves. Instead, intake and exhaust flows occur through ports in the cylinder walls.

Fuel injection occurs directly into the cylinder via an air-assisted system developed by Orbital for a different two-stroke engine the company has been working on for about

30 years. Lotus claims that the Omnivore engine can operate extensively in HCCI mode and achieves a 10-percent fuel-efficiency gain over current DI-gasoline engines. Due to the

variable compression ratio, it can also operate on a variety of fuels, hence its name.

At this point, the engine is only a single-cylinder research project. Clever, but

whether it will advance further remains to be seen.

Fiat's Multiair Valve-Lift System Explained

Fiat's Valve-lift system boosts power and saves fuel.

Surging gas prices and impending regulations are causing automakers to hunt

for ways to increase the efficiency of gasoline engines. One of the chief inefficiencies of

these engines is the restriction that’s created by the throttle plate in the intake passage,

which is used to regulate how much air feeds the cylinders. Referred to as “pumping

losses,” this bottleneck caused by a partially open throttle forces an engine to squander

about 10 percent of energy that could otherwise be used for propulsion.

BMW, Nissan/Infiniti, and Fiat have overcome much of these pumping losses by

instead throttling their engines via the intake valves—varying their lift and the amount of

time the valves are open to control the engine. BMW was first, with its Valvetronic technology, which was launched on various models in 2001. It’s a complex system that uses an additional electronically actuated

camshaft to vary valve lift.

The beauty of Fiat’s “Multiair” system is its simplicity; it essentially achieves what

Valvetronic does by using hydraulic fluid running through narrow passages connecting the intake valves and the camshaft so the two can be decoupled. This system is modulated by an electronically controlled solenoid, and there are effectively two modes: When the

solenoid is closed, the incompressible hydraulic fluid transmits the intake-cam

lobe’s motion to the valve, as in a traditional engine. When the solenoid is open, the oil

bypasses the passage, decoupling the valve, which then closes conventionally via spring pressure. For example, to shut the valves

early, as in a part-load situation, the solenoid would be closed initially and

then open partway through the intake cycle. The tricky business is correctly timing the

switching of the solenoid, and Fiat has painstakingly optimized the responsiveness of the electronic controls. Aside from the fuel-economy and emissions benefits, Fiat claims

Multiair can also enable a 10-percent horsepower boost. This technology will go

into production in Europe later this year on a 1.4-liter turbo and will also be used on

naturally aspirated engines as it spreads throughout Fiat’s lineup. View Photo Gallery

Camshafts Internal Combustion Engine - Three-Way Cam Lobe ShootoutAre Roller Cams Worth It? Should You Just Run

A Flat Tappet? We'll Show You In Our Shootout.

Camshafts are one of the most confusing

components in an internal combustion engine. What

makes those lumpy bumpsticks even more

confounding is the sheer number of grinds available,

and then multiply that by flat-tappet hydraulic,

hydraulic roller, and mechanical roller. With all those

choices, how do you go about choosing a cam?

While you could use the dartboard approach, in this

age of computer simulators there's just no excuse

for not arming yourself with the right information.

That's what we're going to dive into here. To play out

our dartboard analogy, consider that once you've

read this story, that ancient finned dart has just

become a laser-guided missile that will home right in

on your next cam selection.

We chose three cams with almost identical duration numbers to use as our test mules to com

It seems there is plenty of misinformation when it

comes to comparing and contrasting a hydraulic flat-

tappet cam with a hydraulic or mechanical roller. All

three offer different valve lift potential, yet there

should be a way to compare them on a level playing

field. We huddled up with Comp Cams' chief cam

designer, Billy Godbold, and came up with a

camshaft from each of those different follower

families that all share a very close kinship with

duration at 0.050 inch, so that's what we chose as

our common denominator. Now right away, you're

going to look at the cam specs box and think we're

off our rocker arms because the numbers don't

match up. See, that's where it gets complicated.

You're gonna have to read all the solid tech stuff to

understand what we're doing here. Don't skip over

the details or you'll miss something important. And

while you're at it, eat your vegetables too.

Cam Basics

Since there are readers new to this magazine every

month, let's quickly roll through some camshaft

basics to bring everybody up to speed. There are

several ways to evaluate any camshaft, so we'll start

with the simplest: lift. A cam lobe is nothing more

than an eccentric on a shaft that rotates to create

lifter movement. Lift is created when the lobe moves

off its base circle, pushing up on the lifter. This lobe

lift is multiplied by the rocker ratio to create total

valve lift. As an example, with 0.330 inch of lobe lift

multiplied by a 1.5:1 rocker ratio, the valve lift would

be 0.495 inch.

Perhaps the most informative portion of lobe specs

is duration, which is expressed in terms of

crankshaft degrees. Duration is also most often

delivered in terms of either advertised duration or

duration at 0.050 inch of tappet lift. To be totally

accurate, any duration spec should be accompanied

by the amount of tappet lift where the duration is

measured. This rarely happens with advertised

duration, but we can tell you that Comp Cams

measures both its hydraulic flat-tappet and roller

camshafts at 0.006 inch of tappet lift.

Setting lash on any engine is relatively easy. The best procedure is to warm the engine an

Where all this information can get confusing is when

we move to mechanical lifter camshafts, either flat-

tappet or mechanical roller, and talk about valve

lash. Published cam specs are based on the

numbers generated by the cam lobes and their

effect on the valve. All mechanical lifter camshafts

require a clearance between the rocker arm and the

valve to account for expansion as the engine warms

up. In the case of our XR286R roller cam, the intake

lash or clearance is 0.016 inch with the engine hot.

Lash affects most of the published cam specs. The

0.576-inch gross intake valve lift figure on the cam

card does not take into account the lash. This

means we must use the equation 0.576 - 0.016 =

0.560 inch to come up with our actual net valve lift

number. It's a small point, but worth noting for

accuracy.

Lash also has an effect on duration. According to Comp Cams, the net change is that 0.001 inch of lash

shortens the actual cam duration by 0.5 degree. So with a 0.016-inch lash on the intake, this effectively

shortens the intake duration at 0.050 inch checking height by 8 degrees, creating a net duration of 240

degrees at 0.050 inch tappet lift. This explains why we chose a 248 at 0.050 roller cam, because the net

duration after lash is actually 240 degrees.

CAM SPECSCam Adv. Duration Lift Lobe   Duration @ 0.050   SeparationXE284 flat hyd., int.

284 240 0.507 110

PN 12-250-3, exh.

296 246 0.510  

XR294HR, hyd. roller, int.

294 242 0.540 110

PN 12-43-8, exh.

300 248 0.562  

XR286R mech. roller, int.

286 248 0.576 110

PN 12-772-8, exh.

292 252 0.582  

Lash: 0.016 int., 0.018 exh.

Why Roller Cams Are Better

This is some serious stuff, so you'll need to get rid of

your normal distractions for a few minutes. It is

possible to accurately compare a hydraulic flat-

tappet cam with a hydraulic roller or even with a

mechanical roller cam, but there are some important

stepping stones to getting there. To begin with, all

cams are rated for duration, based on the lobe

profile and expressed in crankshaft degrees. For

example, lift is expressed on the cam card in terms

of valve lift using the stock rocker ratio. But what we

should really be looking at with any style camshaft is

the duration of valve opening. According to Comp

Cams, the best way to rate a hydraulic lifter cam at

the valve is to assume 0.004 inch of lifter piston

bleed-down before the lifter begins to move the

valve through the rocker arm ratio. In our chart the

duration number 283 degrees indicates that the XE

flat-tappet cam measures cam lobe duration at

0.006 inch of lifter rise (advertised duration), while

the second column indicates that after 0.004 inch of

tappet bleed-down and the lobe multiplied by the

1.5:1 rocker ratio, the duration at the valve is

actually 282 degrees at 0.006-inch tappet lift.

You can't tell much about a cam by looking at it. Even the two roller cams look much the s

We can use that same 0.004-inch lifter deflection

figure to rate hydraulic roller cams. Notice that

despite the fact that the flat-tappet and the hydraulic

roller cams are only 2 degrees apart at 0.050 inch of

lobe lift (240 versus 242), the hydraulic roller offers 5

more degrees of duration at the valve at 0.200 inch

of lobe lift and an impressive 16 more degrees of

duration at the valve at 0.400-inch lobe lift (from 107

to 123 degrees). This indicates the higher lifter

speed capability of the hydraulic roller design over

the hydraulic flat tappet. So while at 0.050 these

cams appear the same, this number by itself is

deceiving. Looking at a basic lift curve, the hydraulic

roller achieves a given lobe lift such as 0.200 inch

much more quickly and therefore creates more area

under the valve lift curve. This means more air and

fuel will enter the cylinder to make more power. Now

let's look at the mechanical roller lobe.

Mechanical lifter camshafts are more difficult to evaluate because you should not use advertised

duration as an indicator for several reasons. First, because of 0.016 inch of lash (clearance between the

rocker arm and the valve), a lobe duration number measured at 0.006-inch tappet lift is meaningless

because at a rocker ratio of 1.5:1, that 0.006-inch lobe lift number is worth 0.009 inch of movement at

the rocker tip, which is still short of taking up the 0.016 inch of clearance. Even at 0.050 inch of lobe lift

(duration at 0.050), this calculated number of 253 degrees of duration does not take into account the

lash. Going back to Godbold's rule of thumb, every 0.001 inch of tappet lift is worth roughly half a

degree of duration. In order to account for our rated 0.016 inch of lash, we must remove 8 degrees from

the 0.050-inch duration figures, which means the 248 degrees at 0.050 is really 240 degrees and

therefore exactly the same lobe duration at 0.050-inch tappet lift as the flat-tappet hydraulic camshaft.

But notice the tremendous velocity the mechanical roller cam can generate throughout the entire lift

curve, offering up a serious 197 degrees at 0.200-inch lobe lift. Compared to the hydraulic roller and flat-

tappet cams, you can see why the mechanical roller is superior. At the extreme, the mechanical roller

offers a staggering 21 more degrees of duration at 0.400-inch lobe lift than the hydraulic flat-tappet

cam, and 5 more degrees than even the hydraulic roller (123 versus 128). What this means is that the

intake valve is held open at the same valve lift for a much longer period of time within the cycle from

when the valve first opens until it closes. This is why the mechanical roller cam can make more power

than the hydraulic flat-tappet. Because of additional duration and greater lift, the mechanical roller lifter

is traveling faster than its more conservative hydraulic counterparts, which is why lighter components

and stiffer valvesprings must be part of the overall package.

  284XE Hyd. Flat

294XE Hyd.

286XER

     

RollerMech. Roller

Lobe Lift

Lobe Dur. Valve Dur.

Lobe Dur. Valve Dur.

Lobe Dur.

Valve Dur.

   

  @ 1.5:1 @ 1.5:1  @ 1.5:1

   

 (w/ 0.004

(w/ 0.004

 (0.016 lash)

   

 deflection)

deflection)

       

0.006

283 282 294292 (+10)

309

285 (+3)

0.015

268 271 276280 (+9)

285

276 (+5)

0.050

240 250 242253 (+3)

248

253 (+3)

0.200

153 190 164195 (+5)

170

197 (+7)

0.400

- 107 -123 (+16)

-128 (+21)

The numbers in parentheses for valve duration at

1.5:1 for both the 294XE hydraulic and the 286 XER

are the number of degrees of difference compared

to the 284XE hydraulic flat-tappet cam.

Valvesprings need to be carefully matched to the specific camshaft in order to obtain maxi

Why You Need To Upgrade The Valvesprings

This chart is easy to understand once you know a

little bit about valvesprings. Load at installed height

refers to the amount of pressure in pounds created

by the spring with the valve closed at a given

installed height. The installed height is the distance

from the bottom of the retainer to the spring seat

location on the cylinder head. Load at maximum lift

is the pressure created by the spring across the

nose of the cam at its greatest valve opening. The

spring rate is the amount of load in pounds created

for every inch of travel the spring is compressed. If

you know the load at both the closed and open

points, you can determine the rate. Subtract the

installed load from the open load and then multiply

by the lift ratio (lift ratio = 1 divided by the max valve

lift). Using the 939 spring as an example: 420 - 167

= 253 x 1.85 [1 1/4 0.540 lift = 1.85] = 468 pounds

per inch (lb/in) spring rate. Coil-bind refers to the

height of the spring when it is fully compressed. It's

critical that the engine builder allow a minimum of

0.060 inch of clearance to coil-bind. We chose

spring pressures higher than Comp's

recommendations to ensure that the valvetrain

would not go into valve float during testing.

Note the radical increase in seat pressure for the mechanical roller spring application. The hydraulic flat-

tappet and roller springs both use a seat load of roughly 160 pounds. But when we get to the

mechanical roller springs, the seat pressure jumps to 240 pounds at the same installed height. That's a

50 percent increase in seat pressure and a 59 percent increase in load at max lift. This is necessary in

order to fully control the much higher acceleration rate and valve velocities achieved by the mechanical

roller lobe working on the valves. As these opening and closing rates increase, they create much larger

forces on the valve that must be controlled by the valvesprings.

ValvespringLoad @installed ht.

Load @ max lift

Rate (lbs./in.)

Coil-bind(in.)

Comp PN 928, dual

153 @ 1.900

330 @ 0.500

354 1.160

Comp PN 939, dual

167 @ 1.900

420 @ 0.540

468 1.225

Comp PN 943, dual 240 @ 1.900

557 @ 0.575 551

1.150    

Each cam required a spring change to allow us to get the most performance out of each cams

Three Springs for Three Cams

It would be nice if all the moons and stars aligned in

the engine-building world so that one valvespring

would work for all applications. Perhaps back in the

'20s that was the case, but not now. Because we

have three completely different cam designs in a

flat-tappet, a hydraulic roller, and a mechanical

roller, all three require their own design valvespring.

Spring pressure is critical to ensure that the valve is

always controlled by the camshaft. Valve float is a

common term referring to a loss of control, but for

most engines the first sign of trouble is when the

intake valve bounces off the seat on the closing

portion of the lift curve. This allows cylinder pressure

to escape back into the intake manifold, reducing

power. Eventually the engine will begin to pop and

bang, sounding like an ignition misfire, when in

reality it is the valvesprings that have failed.

Increasing the spring rate is the most popular

solution to this problem, but another fix is to either

reduce the rocker arm ratio or reduce the weight of

the rocker arm side of the valvetrain, as with titanium

retainers. Another excellent investment is thicker-

walled pushrods. For small-block Chevys, 0.080-

inch-wall-thickness, 51/416-inch-diameter pushrods

are very common, but they do cost more. Stronger

pushrods tend to deflect less, which reduces the

pole-vault effect that can occur at high rpm when the

pushrod bends and then launches the lifter over the

nose of the cam.

The problem with increasing spring pressure with a

flat-tappet camshaft is that too much pressure can

literally wipe the lobe right off the cam. This is

especially critical during camshaft break-in. For our

engine, using the 928 dual springs required us to

remove the inner spring for break-in and then install

the inner springs after the cam had established its

wear pattern. Even then we added extra insurance

by using Comp Cams' break-in lubricant, which

offers a higher zinc additive package to reduce initial

wear on the new cam. When it comes to longer-

duration hydraulic, flat- tappet, and hydraulic roller

camshafts, the valvespring question becomes a

delicate balancing act between maintaining sufficient

spring pressure to control the valves at higher

engine speeds and avoiding excessive spring

pressures that can cause problems.

We also checked pushrod length with each cam change to maintain valvetrain geometry accura

The beauty of a mechanical roller cam is that it

allows the luxury of higher spring pressures, but

there are difficulties here as well. Increased spring

pressures place higher loads on the valvetrain,

causing increased wear, not to mention abuse on

those tiny roller bearings in the lifters. One reason

for increased spring pressure is the higher engine

speed that is part of the equation for a long-duration

mechanical roller camshaft. We've included a short

spring-pressure chart created with help from

Westech's Steve Brul that we used to help us

determine the best springs for each of the three

different camshafts. These are numbers that Brul

has found works for him.

An interesting question surfaced during this testing relative to how much spring pressure a hydraulic

roller cam combination could withstand. Keeping this explanation short and simple, too much spring

pressure does not really force the hydraulic lifter piston down, as is commonly thought. What really

happens is that higher spring pressures tend to deflect the pushrod, which causes valvetrain separation

at higher engine speeds when the pushrod pole vaults the valve past the nose of the cam. This clearance

in the valvetrain allows the lifter piston to pump up. When the cam lobe returns to the base circle, the

pumped-up lifter holds the intake valve open and causes the engine to lose power. Reducing hydraulic

roller valvespring pressures to more manageable levels reduces pushrod flex and minimizes lifter pump-

up.

SPRING PRESSURE CHART

Lifter Style  Seat Pressure

Open Pressure

    (lbs.) (lbs.)Hydraulic flat tappet

150*   350*

Hydraulic roller   200 400Mechanical roller

220   575

*After cam break-in. It is advisable to remove the

inner spring on any dual-spring package when

breaking in a new flat-tappet camshaft. This is not

necessary with roller cams.

Test Time

With all this background tech information jammed

into our heads, now it was finally time to put down

the theory books and get our hands dirty. The small-

block we decided to beat on was the healthy 383ci

we used last month for the giant "Speed Parts

Tested" cover story. The engine configuration for

this test is a little different but includes 10.5:1

compression from a complete Lunati rotator

assembly, a set of Dart CNC 227 heads, a Holley

Keith Dorton single-plane intake manifold, and a

Barry Grant 850 Mighty Demon carburetor. We

started the test with the smallest cam, the Comp

Xtreme Energy 284 hydraulic flat-tappet version

matched up with a dual-spring package, titanium

retainer, and the appropriate-length pushrods. The

flat-tappet cam made respectable peak power at 507

hp at 6,200 rpm and 489 lb-ft of torque at 5,000. The

beauty of a flat tappet is its decent power and great

torque, all delivered at an affordable price. But now

we were looking forward to ramping up the power

numbers with the roller cams.

The hydraulic roller slid right in along with the taller

Comp Cams hydraulic roller lifters. The taller lifters

also demand shorter pushrods and, of course, a

swap to a stronger set of Comp dual springs, which

increase the spring load in order to help control the

valves. As we expected, the hydraulic roller made

more peak power than the flat tappet along with

slightly more torque due to its more aggressive roller

lobe design. This helps justify its increased cost. The

hydraulic roller jumped the power up to 530 at 6,200

rpm while the torque also grew from 489 to 502 at

5,200. That's a solid 13 lb-ft increase of torque and

23 hp. Also note that both hydraulic cams peaked at

almost the same rpm for both torque and

horsepower. But all this did was motivate us to bolt

in the mechanical roller.

Our 383 small-block Chevy test mule consisted of a 383 with a Lunati forged crank, rod, an

By now we were getting good at swapping cams,

and the motor had barely cooled down before the

new mechanical roller was in place and the springs

and pushrods swapped once again. With 0.016-inch

lash dialed in on the intake, the duration at the valve

was exactly the same as the flat-tappet hydraulic

cam, yet this mechanical roller setup rocked when it

came to peak horsepower. Once we pulled the

throttle handle, however, it quickly became apparent

that while the peak horsepower was up over the

hydraulic roller, the mechanical and hydraulic roller

cam torque curves in the middle were almost

identical, something we didn't expect. The

mechanical roller's torque peak was actually down 6

lb-ft to 496 at 5,200 compared to the hydraulic roller,

but made up the difference at peak horsepower with

an impressive 539 at 6,600, which is up 9 hp over

the hydraulic roller.

The best way to evaluate this test is to look at the

power averages for all three cams. Because all three

cams were chosen with the same duration at 0.050,

there's not a huge difference in power averages

between the three. The mechanical roller clearly

owns the peak horsepower title with a stout 32hp

advantage over the flat tappet. The mechanical roller

also is up 12 hp and 11 lb-ft of torque average,

which is a significant difference. But let's not

overlook how well the flat-tappet cam performed,

especially if we factor in the additional cost of either

roller cam package. Of course, there's also the

hassle factor of the flat-tappet cam, with both break-

in and longevity concerns with current engine

lubricants. But the power difference clearly points to

the best power-per-dollar choice being with the flat-

tappet cam. Looking at all the data, it would have

been interesting to see how a flat-tappet mechanical

cam would have fared in this test.

If you look at the graph of the three power curves,

this may help with the concept of which lifter style

cam is the correct one to use. Remember that the

easiest way to make normally aspirated horsepower

is to make the same torque at a higher engine

speed. If you look at the flat-tappet hydraulic

horsepower curve, it tends to flatten out at 5,200

rpm, while the two roller cam curves extend peak

horsepower well past 6,000. If you plan to only shift

your engine at 5,500 rpm or below, there's no

reason to spend the extra money for a roller

camshaft since all three cam torque curves up

through around 5,200 rpm are very similar. The

roller cams deliver far more valve control and rpm

potential to make more horsepower. Also notice how

the hydraulic roller tends to drop off at around 6,200

while the mechanical roller cam continues to make

power up through 6,600. We think that this slight dip

in the hydraulic roller curve is probably due to

pushrod deflection. Since the price difference

between a hydraulic roller and a mechanical roller

cam is relatively small, there are opportunities for

both styles of cam, especially if your plans include a

shorter-duration roller cam that is not going to spin

as high an rpm as these 240-degrees-at-0.050-

duration camshafts.

What this test does illustrate is how critical duration

is to the power curve since all three cams,

regardless of lifter design, are very close in terms of

peak torque. Peak horsepower changed the most

between the three cams, but most of that was the

change the mechanical roller made by pushing the

peak horsepower up to 6,600 rpm. This is also of

concern because to take full advantage of a 6,600-

rpm peak horsepower point, it's generally required to

spin the engine another 400 to 500 rpm past peak

power to get the most acceleration advantage out of

the engine. This means twisting this small-block to

around 7,000 rpm. You'd better have a good steel

crank, rods, and strong forged pistons if you're

gonna spin a small-block 383 to 7,000 rpm!

Power By The NumbersTest 1 consisted of the 383

small-block Chevy with the flat-tappet hydraulic

Comp XE284 cam. All other components for this test

remained the same for all three tests.

Test 2 changed to the XEHR294 hydraulic roller cam

and dual valvesprings.

Test 3 swapped to the XR286 mechanical roller cam

and to a third, higher-load set of dual valvesprings

with titanium retainers.

Before bolting the engine on the dyno, we also took the time to check for roller cam endpl

The DIFF column represents the difference in power between Test 1 and Test 3.

  TEST 1 TEST 2 TEST 3 DIFFRPM TQ HP TQ HP TQ HP TQ HP3,000 420 240 421 241 425 243 +5 +33,200 429 262 429 262 431 263 +2 +13,400 430 279 430 278 434 281 +4 +23,600 436 299 438 300 437 300 + 1 +13,800 441 319 445 322 445 322 +4 +34,000 448 341 446 340 446 340 - 2 - 14,200 460 368 460 368 462 370 +2 +24,400 465 390 467 391 472 395 +7 +54,600 477 418 476 417 481 422 +4 +44,800 487 446 491 449 489 447 +2 +1

5,000 489 466 500 476 494 470 +5 +45,200 489 485 502 497 496 491 +7 +65,400 482 495 496 510 493 507 +11+125,600 467 498 487 519 486 518 +19+205,800 456 503 478 528 476 526 +20+236,000 443 506 463 529 464 530 +21+246,200 429 507 449 530 452 534 +23+276,400 409 499 431 525 442 539 +33+406,600 378 475 415 522 429 539+51+64Avg. 450.7 412 460.7 423 461.7 424 +11+12Peak 489 507 502 530 496 539 +7 +32

Note: The average columns take into account power

numbers every 100 rpm, which are not listed in this

chart.

Power CurvesNote how all three camshafts create almost identical power curves through 5,000 rpm. By 5,200 rpm,

you can see the hydraulic flat-tappet cam begin to nose over while both rollers continue to make similar

power up to 6,000, where the mechanical roller takes over to make the most peak horsepower.

PARTS LISTCOMPONENT PN SOURCE PRICEComp XE 284 hyd. flat

12-250-3

Summit Racing

115.95

Comp XR 294HR hyd. roller

12-443-8

Summit Racing

255.95

Comp XR286R mech. roller

12-772-8

Summit Racing

255.95

Comp hydraulic lifters

858-16Summit Racing

92.95

Comp hydraulic roller lifters

885-16Summit Racing

509.95

Comp mechanical roller lifters

888-16Summit Racing

516.99

Comp rocker, Pro Magnum 1.5:1

1104-16Summit Racing

430.69

Comp springs, dual for flat hyd.

928Summit Racing

139.95

Comp retainer, for 928, titanium

732-16Summit Racing

299.95

Comp 10-degree keepers

611-16Summit Racing

22.88

Comp dual spring, 943-16 Summit 299.95

mech. roller RacingComp retainer, dual spring, titan

731-16Summit Racing

299.95

Comp springs, dual hyd. roller

939-16Summit Racing

137.39

Comp retainer, titanium for dual

732-16Summit Racing

299.95

Comp pushrods, hydraulic roller

7949-16Summit Racing

145.95

Comp pushrods, std. length

7992-16Summit Racing

168.69

Comp pushrods, hyd. flat, + 0.100

7993-16Summit Racing

125.95

Comp pushrods, mech. roller

7995-16Summit Racing

135.95

Comp timing set 3100KTSummit Racing

176.69

Comp roller button 211Summit Racing

22.39

Comp 3-pc. timing cover

210Summit Racing

229.95

Comp shim package

4757Summit Racing

25.69

Moroso stud mount spring tool

62370Summit Racing

79.95

With the lifters, it's a little

easier to tell a flat-tappet hydraulic (right) from the

hy We used titanium retainers on

all the springs in this test because of the rather

high engiPiezo Fuel Injectors Explained

The Tower of Piezo: The smartest

injectors you’ll ever meet. February 2011

BY CSABA CSERE

If you’ve ever seen the sparks created by someone munching Wint-O-Green Life Savers

in a darkened room, you’ll have witnessed this phenomenon: Certain crystalline

materials, such as sugar, produce minute

amounts of electricity when you squeeze them. There’s even a word for it:

“piezoelectric,” which describes electricity resulting from pressure. But the process is

also reversible, in that these same materials expand slightly when electricity is applied to

them. There are numerous places in a car where piezoelectric expansion can come in

handy.

Take, for example, the precise metering necessary for modern-day fuel delivery. Bosch, Continental, and Delphi, among

others, have harnessed this peculiar property of expanding piezo material—rather than the

usual electromagnet—to open the fuel-injector nozzle and precisely spray fuel into both gasoline and diesel engines. Making these devices work, however, isn’t easy.

One reason is that the expansion of the piezo crystals is minuscule. A slice of piezo material two-hundredths of an inch thick expands only about 0.00002 inch when it gets hit with roughly 140 volts of electricity. That two-hundred-thousandths of an inch is not nearly enough to move an injector’s pintle,

which is the part that seals the nozzle and must open to inject fuel.

The Continental injector has hundreds of little piezo slices stacked on top of each other so that the combined expansion increases the total motion. The stack produces 0.004 inch of movement—enough to move the pintle far

enough to inject fuel. But because this motion is in the wrong direction—down, not up—the

addition of two tiny levers allows the expansion of  the piezo stack to cause the

pintle to be lifted and the fuel spray to begin. When the injection is complete, the voltage

cuts off, the piezo stack shrinks, and a spring closes the pintle.

Piezo injectors have a few key benefits that justify all of this bother. For one thing, they

open and close much faster than conventional injectors. That makes for more precise control of the injection interval, which

determines how much fuel is sprayed into the engine. Piezo units also provide feedback by

producing minute fluctuations in the electricity used to activate them. For

example, if the engine-control computer calls for an injector-opening time of 0.5 second,

and the injector response shows that it opened for only 0.496 second, the computer

can add a tiny bit of time to the next injection

cycle to compensate. Such precise fuel metering makes for improved combustion,

which leads to better fuel economy and reduced emissions.

Not only are piezo injectors more accurate than conventional solid injectors, they also

can perform some tricks that are completely beyond the capabilities of their predecessors.

For one thing, by applying a little less electricity, the piezo crystals expand less so the injectors can open partway. A smaller

opening means a longer injection time, which is beneficial when trying to accurately inject a tiny amount of fuel, such as when a car is

nearly coasting. Because they act so quickly, piezo injectors also can inject several times (as many as seven in some diesels) during a single combustion cycle. This flexibility can reduce emissions in all engines as well as

limit soot in diesels.

These benefits have secured a home for piezo injectors in many of the latest diesel and

direct-injection gasoline engines. And Continental, for one, says that its piezo units

don’t cost more than the less capable conventional equivalents. Piezo injectors are

one of the key devices that will keep internal combustions competitive against these pesky

electric upstarts for years to come.

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Mazda Skyactiv-G and Skyactiv-D Engines in Detail - Car News

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Mazda Skyactiv-G and Skyactiv-D Engines in Detail

A deep dive into Mazda's new gas and diesel four-cylinders reveals huge fuel-

economy gains.

August 2010 BY DAVE VANDERWERP

Around the world, automakers are grappling with the changes necessary to meet

escalating fuel-economy regulations. To this end, Mazda is launching a new family of four-

cylinder engines—fours power the vast majority of Mazda’s cars—called Sky-G

(gasoline) and Sky-D (diesel). We drove both in prototypes of the next-gen Mazda 6 and, thankfully, either engine can be paired with the latest version of Mazda’s snick-snick six-

speed manual.

We got the deep dive on the 2.0-liter version of the Sky-G, which will launch next year in the U.S., likely as part of a midcycle face lift of the Mazda 6. (A completely new 6 is a few years out yet and will be about 140 pounds

lighter than the current car, thanks to meticulous optimization of material

thicknesses and mounting points.) In the future, there also will be variations in the 1.3-

to 2.5-liter realm, and Mazda has already signed a deal to license Toyota’s hybrid

technology for a future Sky-based hybrid. Starting from the ground up, Mazda has impressively leapfrogged its previous gas engine, to the tune of estimated EPA fuel-

economy ratings in a Sky-equipped Mazda 3 of 30 mpg city and 39 to 40 highway. That’s

nearly on par with VW’s Golf and Jetta diesels as well as best-in-class cars one segment

smaller, such as the Ford Fiesta and Chevrolet Cruze. Here’s how they did it.

The Big Squeeze

Increasing the compression ratio—in this case, to a staggering 14:1 from 11:1 in the

current 2.0-liter (the U.S. version is 10:1)—is a classic way to squeeze more work out of the

piston’s power stroke. But it creates problems, too, because compressing the

air/fuel mixture this much causes excess heat build-up in the cylinder, which leads to

premature auto-ignition, or knock. To keep the temperatures down, Mazda employs a

seriously lengthy 4-2-1 exhaust header, designed so that the hot exhaust gases don’t

get pulled back into the next cylinder’s intake stroke. As it stands today, it doesn’t appear

that the Sky could fit in a longitudinal application such as the Miata—the huge header likely would poke

through a front fender.

Further improvements include the addition of direct injection and a reduction of heat loss—

too much heat can be problematic, but temperature is a necessary byproduct of

burning fuel, and squelching it all is

inefficient. The heat-loss reduction comes from a smaller bore and a much more

complex piston shape that features a cavity directly in the piston’s center, the hot area

where the spark plug fires. Friction also has been reduced in the pistons, rods, and

crankshaft (which is now forged steel instead of cast iron), and roller finger followers

reduce it in the valvetrain. The engine uses 0W20 oil, which looks frighteningly like colored water. The Sky also gets dual

variable valve timing, electronically varied (as opposed to using oil pressure) on the

intake side, so that rapid adjustments can be made even during cold starts. Overall weight

has been reduced by about 15 pounds, including 10 saved by thinning out the block

where additional strength wasn’t needed.

Premium Fuel, Mid-Grade Output

Premium, 91-octane fuel is required for the Sky’s not-so-staggering 163 hp at 6000 rpm and 155 lb-ft at 4000, but Mazda is proud of

its exceptionally wide torque band for enhanced real-world drivability. To enable

running on regular gas, the U.S. version will have a compression ratio of 13:1, which

means fuel economy and torque will diminish by about 3 to 5 percent, according to Mazda.

The premium-fueled Sky we drove was perfectly adequate in the Mazda 6

prototypes, although acceleration was rather leisurely—far slower than the current Mazda 6 with its 168-hp, 2.5-liter—giving us plenty of time to wish for a bit more smoothness

during the extended time in each gear. But being in the lighter Mazda 3 would help, and

the tradeoff for near-diesel levels of fuel economy is probably worth it.

Surprisingly, Mazda is passing on today’s popular trend of downsized, turbocharged engines—say, a 1.4-liter turbo instead of this 2.0-liter. The company says the next generation of gasoline engines, which will

employ HCCI (Homogenous Charge Compression Ignition)—essentially firing a gasoline engine like a diesel, without using the spark plugs—will erode the benefits of downsized engines. Smaller engines reduce pumping losses by operating at a higher load (the throttle is open further) more often. In the

same way, HCCI engines will have to flow more air to realize the fuel-saving, lean-combustion benefits of that cycle. Mazda claims that if it downsized the Sky family of engines they wouldn’t be able to flow

enough air for HCCI without upsizing once again. Plus, as Mazda rightly points out, adding a turbocharger and an intercooler is quite a pricey proposition.

Oil-Burner Exposé

On the diesel side, Mazda has pulled off an even more impressive feat. The 2.2-liter Sky-

D (again, other sizes are likely to follow) boosts fuel economy by 20 percent over the

current, 2.2-liter diesel and meets Euro 6 and U.S. Tier 2 Bin 5 emissions standards without

using any NOx aftertreatment such as urea injection. You catch that? It meets U.S.

emissions standards. That’s because Mazda is planning to bring this engine here sometime

in 2012.

With the diesel, Mazda moved in the opposite direction, decreasing the compression ratio

from 16.3:1 down to 14:1. That’s the same as the gas-burning Sky-G, and a value that’s the lowest in the world among diesels, according

to Mazda. Doing so reduces cylinder pressures, and therefore temperatures, which reduces NOx production and also

allows the fuel to mix better, avoiding locally rich areas that produce soot. Mazda claims that the lessened friction from the reduced cylinder pressure alone is worth a 4- to 5-

percent gain in fuel economy. And the reduced internal forces also allow

components such as the rods and pistons to be substantially lighter. Here, too, a forged steel crankshaft replaces a cast-iron unit. Overall weight savings is a whopping 55

pounds.

The downside to lowering the compression ratio of a diesel is that, during warm-up, the engine temperature can be too low to support proper combustion, and misfires result. To get around this,

Mazda added a two-stage variable valve-lift system on the exhaust side in order to be able to create additional valve overlap. This causes the hot exhaust gases to be drawn back into the next cylinder to

warm it up.

Eat It, Hybrids

Other new features are a sequential twin-turbo arrangement—one small and one large—which outperforms the old single, variable-geometry unit; 12-hole piezo injectors that disperse fuel into the cylinder in exacting quantities during two to eight separate

injections per cycle at pressures up to 2900

psi; and an exhaust manifold that’s completely integrated into the block. Here, too, fuel-economy claims are impressive: 31

to 33 mpg city and 43 mpg highway for a Mazda 6 with the 2.2-liter diesel. Does an over-40-mpg family sedan sound good to

anyone else?

Output beats the gas engine in both regards: 173 hp at 4500 rpm and 310 lb-ft at 2000.

Redline has been raised to a screaming (for a diesel) 5200 rpm, versus its predecessor’s 4500. And it felt notably quicker than the

gas-engined car, pulling strongly throughout the rev range and exhibiting none of the run-out-of-breath feeling that afflicts some diesels

as they wind toward the upper end of the tach. It’s exceptionally responsive, and quiet,

too, with very little clatter, even when accelerating from engine speeds below 1500

rpm.

Automatic Anxiety

In addition to the sweet-shifting six-speed manual, we drove each engine with Mazda’s

new Sky-drive six-speed automatic, which boasts a more aggressive lock-up clutch for the torque converter, leading to a 4- to 7-

percent improvement in fuel economy. Although the calibration was admittedly early in development, the automatic was distinctly

less impressive than either of the new engines. In terms of feel, which Mazda claims

is much more direct than before, it doesn’t seem to stand out from the current crop of

high-tech automatics. The wide-open-throttle upshifts struck us as a bit lazy, too, although the downshifts were quite prompt. We’ll stick with the manual, thank you very much. Few buyers do, however, which could mean bad

things for Mazda’s sales.

Perhaps the best thing in all of this, though, is that Mazda’s impressive engineering work proves that the internal-combustion engine

still has plenty of legs in our ever-more-regulated world.View Photo Gallery

Ethanol-Injection Systems Explained

Driving Under the Influence: Ethanol-injection systems aim to use alcohol

responsibly.

December 2011 BY DON SHERMAN

ILLUSTRATION BY PETE SUCHESKI

Thanks to the adoption of direct fuel injection, teaming gas and ethanol has the

potential to beat diesel efficiency.

We can hear your groans already: Our federal government’s effort to curb oil imports by

lacing gasoline with ethanol has been a boon to American farmers but a bust to the driving

public. The problem is simple economics—pumping E85 (85-percent ethanol and 15-

percent gasoline) into today’s flex-fuel cars costs more per mile than fueling the same car

with regular gas. We’re suffering from ethanol’s detriments without exploiting its

advantages.

Ethanol’s balance sheet has been well understood for decades. Because ethanol’s energy density is roughly 66 percent that of

gasoline, mpg suffers when ethanol is used as a straight substitute. On the opposite side of the ledger, ethanol has an octane rating of

100, versus 85 to 100 for gasoline, enabling much higher compression ratios. (Unleaded, 100-octane racing gas is expensive and not

widely distributed. Readily available premium gas tops out at 94 octane.) And when ethanol

changes from liquid to gas on the way to combustion, it absorbs 2.6 times more heat than gasoline, a highly beneficial cooling

effect. So how do we take advantage of those attributes to optimize ethanol’s role in

modern transportation? The history books are a good place to start.

During World War II, BMW and Daimler-Benz sprayed methanol and water mixtures into

their supercharged aircraft engines to forestall detonation (premature ignition of the fuel-air charge). In the U.S., a postwar

GM applied similar research in its 1951 LeSabre dream car, which was powered by a supercharged V-8 capable of running on gas

or methanol. That paved the way for the 1962 Oldsmobile F-85 Jetfire, the world’s first turbocharged production car, which used

“Turbo-Rocket Fluid”—a mix of  water, methanol, and rust inhibitor—to skirt

detonation with a then-ambitious 10.25:1 compression ratio and 5.0 psi of boost.

Today’s racers use all manner of fluids—water, alcohol, nitromethane, lead

substitutes, and nitrous oxide—in pursuit of power. There’s also a government-backed experiment at Chrysler aimed at running both gasoline and diesel fuels through the

same engine. But the most sensible approach for the public at large is to use technology

now in hand to achieve significant mpg gains. The tech? Gasoline, E85, and direct fuel

injection.

British-based Ricardo and Ethanol Boosting Systems (EBS) of Cambridge, Massachusetts, both have E85-fueled engines under test that deliver diesel efficiency—at least 30-percent better than a typical gas engine—without the

need for cumbersome, ultra-high-pressure fuel-injection and exhaust-treatment

equipment.

Both firms propose aggressive turbocharging, a 12.0:1 or higher compression ratio, and

about half the normal piston displacement. Ricardo uses an octane sensor, variable valve

lift, and variations in valve and ignition timing to take maximum advantage of any

ethanol pumped into the fuel tank. EBS adds a second complete fuel system that enables an engine to run on port-injected gas during cruising and direct-injected E85 only during full-load conditions to spare its consumption.

Heavy-duty pickups are the first candidates for this technology. Both EBS and Ricardo pitch their ethanol-based systems as diesel fighters capable of delivering 600 or more pound-feet of

torque at low rpm from a 3.0-liter engine. Assuming that manufacturers agree with these ethanol boosters, the dual-fuel strategy could be handy for meeting the 35.5-mpg CAFE standard for 2016. By then, four-cylinder performance cars will be commonplace, and they’ll definitely be

thirsty for all the Turbo-Rocket Fluid they can get.

Drinking in the ’60s

As noted, the 1962 Oldsmobile F-85 Jetfire’s V-8 (right) tried this whole multifuel thing a while back. The turbocharged 3.5-liter engine, eating five pounds of boost, made 215 horsepower and 300 pound-feet of torque. If the reservoir of “Turbo-Rocket Fluid” ran out, a mechanical system would automatically reduce the amount of boost to avoid detonation. In our test of a 1963 F-85 Jetfire, we recorded a 0-to-60 time of 8.5 seconds, with the quarter-mile falling in 16.8 seconds. The system proved problematic, and over two years GM put fewer than 10,000 of these engines on the road.

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Ricardo Announces a Better Way to Use Ethanol

Ricardo’s high-boost, 400-hp V-6 may replace massive diesels in heavy-duty

pickups.

February 2009

BY DAVE VANDERWERP

A couple years back, there was a big marketing push for E85 fuel—85 percent ethanol, 15 percent gasoline—but little

reason why anyone would want to use it.

E85 currently costs about 10 percent less than regular gasoline in most areas, but

because of its lower energy content delivers a 30-percent reduction in fuel economy. It’s no

wonder the vast majority of the millions of E85-capable, flex-fuel vehicles on the road never burn the stuff. The reason these flex-fuel vehicles exist is a regulatory loophole that allows the automakers to boost their

fleet fuel-economy average (CAFE) because the government only counts the 15 percent

gasoline content when calculating mileage. A flex-fuel Chevy Tahoe, for example, received an absurd 97-mpg E85 rating, which boosts

that all-important CAFE number.

Engineering firm Ricardo—the company responsible for the seven-speed dual-clutch automated manual in the 1001-hp Bugatti

Veyron—has somewhat loftier goals for ethanol. It’s working on a 3.2-liter V-6 engine

that could replace a large turbo-diesel V-8 in a heavy-duty truck application.

Ricardo calls its concept Ethanol Boosted Direct Injection (EBDI) and it’s intended to enable what the company calls “extreme downsizing.” The idea is to use a wildly

smaller-displacement engine and make big power by turbocharging the bejeesus out of it—about 30 psi in this case—and thereby fully exploit E85’s higher, 100-plus-octane rating.

Using E85, Ricardo’s super V-6 makes a heady 400 hp and—get this—664 lb-ft of

torque. That matches GM’s 6.6-liter Duramax diesel V-8, although the EBDI’s torque peak

is higher, at 3200 rpm. Running on pure gasoline drops the output by about 100 hp.

But it’s not as simple as adding boost. “The engine internals have to be nearly as strong

as those in a modern diesel,” says chief engineer Luke Cruff, and just about every piece in Ricardo’s running prototype has

been swapped out for a heftier replacement. The twin-turbo EBDI engine has a 10.5:1 compression ratio and uses two air-to-gas

EGR coolers to chill the high-pressure charge, improve thermal efficiency, and to

ensure there’s no overfueling of the engine under high boost.

An added benefit is that a spark-ignited engine such as this can meet emissions laws

without the expensive exhaust after-treatment (particulate filter, SCR injection) of

diesels. That, along with a less-expensive fuel-injection system—Ricardo’s engine

injects fuel at about 2200 psi versus nearly 30,000 in diesels—saves $2000 to $3000 per

engine.

This particular 3.2-liter V-6 is expected to see duty in an 8000-pound, full-size, heavy-duty pickup truck (18,000-pound GVW) in as soon as three years, and would replace the current

large gasoline or turbo-diesel V-8 options. View Photo Gallery

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Alternative Fuels for America - Feature

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Alternative Fuels for America

Altfuelapalooza: Are any gasoline alternatives ready for the American

mainstream?

August 2010 BY CSABA CSERE

ILLUSTRATION BY MICHAEL DEFORGE

Instead of a wholesale switch to electric cars, with all their inherent range and charging

problems, a seemingly easier way to wean ourselves off gasoline is to find alternate fuel

that could be used in slightly modified internal-combustion engines. Unfortunately,

there are some very real reasons—never mind what conspiracy theorists might tell you about oil companies and corrupt government officials—why most alternative fuels are not

ready for prime time yet. Here’s a look at the current status and near-term future outlook

of the major alternatives to gasoline.

Modern turbo-diesels get about 30 percent better fuel economy than their gasoline

counterparts, have gutsy low-rpm torque, and work well in vehicles with automatics and for towing; they’re a seemingly perfect solution

for the U.S.

Unfortunately, diesel emissions are far dirtier than gas emissions. Removing diesel’s

pollutants requires costly pieces of emissions equipment. Diesel also requires

approximately 30,000-psi fuel-injection systems. These costs make diesels more pricey than even turbocharged, direct-

injection gasoline engines, and those gas engines have the potential to achieve about

two-thirds of diesel’s fuel-economy advantage.

While diesel costs about the same as gas today, it has run as much as 30 percent

higher—and it is taxed at a higher rate than gas. There’s no easy fix to keep diesel prices

low, relative to gas, because American refineries, in general, produce about 19.5

gallons of gasoline and 10.3 gallons of diesel from each barrel of oil. That means a gas-powered vehicle getting 20 mpg can drive about 390 miles on a barrel of oil, while a diesel, at 26 mpg, can go only 270 miles.

Since a barrel of oil doesn’t go as far in a diesel car, a wholesale conversion to diesels

is unlikely in America unless we suddenly figure out how to make diesel fuel from

something other than petroleum. European refineries produce more diesel and less

gasoline from each barrel of oil, but making that switch would essentially require building brand-new refineries. Don’t hold your breath.

One approach is to transform animal fat or vegetable oil, via a transesterification

process, into what is called “biodiesel.” The resulting fuel doesn’t contain sulfur and can be used in pure form, though many vehicle

manufacturers recommend that it be blended with petroleum diesel in proportions between 5 and 20 percent. Biodiesel contains about 9 percent less energy than petroleum diesel,

but it has a higher cetane rating (which promotes more-efficient combustion) and

better lubrication properties.

Despite America’s appetite for french fries, there isn’t enough used cooking oil to make

very much biodiesel. In fact, it has been suggested that to replace all of our petroleum

needs with biodiesel would require the planting of soybeans on all of the arable land

in the United States. New approaches for making biodiesel from algae are being

explored, but they are likely decades away from mass production. Until then, biodiesel’s limited availability and higher cost will keep

it a bit player.

Another diesel alternative is synthetic diesel, made by a variety of chemical conversion

processes that transform natural gas, methanol, or coal into diesel. The resulting fuel is usually sulfur-free and has a higher energy content than petroleum diesel, plus

cleaner exhaust emissions. Converting natural gas to diesel fuel, also known as “gas-

to-liquid,” makes it easier to transport because it requires no refrigeration or

compression.

The cost of synthetic diesel is also reasonable, although the environmental and energy-independence benefits are minimal.

Converting coal to diesel creates much more carbon-dioxide emissions than simply using

petroleum diesel. In fact, this is a problem, in varying degrees, with any of the synthetic-

fuel processes. However, North America has plentiful natural-gas reserves, and this could be a simple way to convert it into an easy-to-

use motor fuel.

The use of E85, which mixes 85 percent corn-based ethanol with 15 percent gasoline, has

stalled due to the fuel’s limited availability, high price (no thanks to our government’s

tariff on E85 imports), the roughly 30 percent fewer miles to the gallon it gets, and the

understanding that its use provides little in the way of carbon reduction if the energy required to grow the corn and turn it into

ethanol is factored in.

Brazil, a country that achieved energy independence by using home-grown ethanol, makes the fuel from sugar. Starting with corn is a much more complex and energy-intensive

process. In the U.S., sugar-based ethanol would be challenging because most of our

land is unsuitable for sugar production.

If we could produce ethanol efficiently from easier-to-grow plants, ethanol would be a good solution. Dubbed “grassoline,” this

ethanol is produced from tall prairie grass or even algae. Several projects to develop a

workable process are under way, but commercial quantities won’t appear before

2020.

A more readily available alternative fuel is compressed natural gas (CNG). Converting a gasoline engine to run on the same stuff most of us use to heat our homes is an easy, low-

cost approach. Natural gas is also cheap, and America has a lot of it. And natural gas

contains far less carbon than gasoline. In fact, a normal engine running on CNG almost

matches a plug-in hybrid for its carbon-dioxide emissions. The price of CNG for the energy equivalent of a gallon of gasoline is

less than a dollar (before taxes).

Still, automakers are reluctant to embrace CNG because it emits some pollutants, while

a hydrogen car or an electric vehicle does not. Also, since it must be compressed to 3500 psi to get enough of it into a tank to

provide a decent range, CNG requires cylindrical Kevlar tanks that are heavier,

more expensive, and harder to package than normal gas tanks.

Hydrogen is the holy grail of synthetic alternative fuels. Whether burned in an

internal-combustion engine or used to power

a fuel cell, its primary byproduct is water. And with that emitted water, you can

produce more hydrogen. Of course, it’s not as easy as it sounds.

Most commercial hydrogen produced today

is made by stripping carbon atoms from

natural gas—a fossil fuel. The removed carbon

atoms then hook up with oxygen to release carbon

dioxide into the atmosphere. If you work through the losses in the process, it would be cleaner, easier, and

cheaper to simply burn natural gas in an internal-combustion engine.

Hydrogen, in its gaseous or liquid form, isn’t easy to store or transport. The network of pipelines that currently moves natural gas

around the country is too porous to keep the tiny hydrogen molecules from escaping. In automobiles, hydrogen has to be stored in stout cylindrical tanks and compressed to

between 5000 and 10,000 psi.

Creating hydrogen using solar, hydroelectric, or wind power are pollution-free solutions,

but solar cells, wind turbines, and hydroelectric dams aren’t free. Until we come up with a cheap, large-scale, and

pollution-free method of generating electricity so that we can produce hydrogen from water, the widespread use of hydrogen

as a fuel seems unlikely.

How To: Convert Your Diesel to Run on Vegetable Oil

This month’s featured ratcheting wrenches helped us turn our project ambulance into a mobile deep-fryer.

February 2010

We first looked at waste vegetable oil (WVO) conversions in March 2004, when we wrote

about Justin Carven and his kits (www.greasecar.com). We recently bought a

used 1996 Ford E-350 ambulance for a future project and decided to find out how hard it is to install a Greasecar kit. Carven counseled against trying to convert a van because its cramped engine compartment makes it ill-

suited for accommodating his kit’s hardware (other companies make more van-friendly conversions). We went ahead anyway, as it

promised to be a good way to test our sampling of ratcheting wrenches, which we found to cut down on skinned knuckles and

toiling time.

To make a diesel vehicle able to cope with WVO, you essentially install a parallel fuel

system with hardware that is resistant to the specific corrosive qualities of vegetable oil. This system also needs to be heated to keep

the oil’s viscosity low. Here’s the basic procedure, although some applications might

require extra parts or steps.

1. Install a second tank for the veggie oil. The engine will start on diesel, and once warmed

up, lines from the engine’s cooling system provide heat to warm the WVO. (Local veg-oil mechanic Joe McEachern prefers to switch to

a 205-degree engine thermostat for better heating, but the Greasecar fuel line runs

inside one of the coolant lines from the tank and, therefore, won’t hold up to that amount

of heat.)

2. Install the switching hardware for the fuel lines. This allows you to alternate between diesel and WVO to both run the engine and

backwash the veg-oil lines with diesel to prevent them from gumming up when cold. For the Ford, we had to remove the diesel-

fuel-filter assembly, which sits in the valley of the engine’s vee. The GearWrench Flex

works well to swivel its way around the van’s cramped packaging.

3. Install an aftermarket pump to move the WVO from its tank. Some vehicles, like our Ford, can use the stock fuel pump for both fuels, but McEachern tells us the factory

units won’t last long when pumping vegetable oil.

4. Run the WVO fuel lines from the tank to the switching hardware, including a water-separating fuel filter with a heat exchanger. Clean, warm oil is essential, so you may have

to install extra heat exchangers or filters. Wherever you mount this extra hardware will

probably be cramped, so, once again, the ratcheting wrenches save a lot of time

normally wasted on realigning a wrench after each fraction of a turn.

5. Wire an automated controller or manual switch to manage fuel selection. You’ll also want gauges for fuel pressure, WVO temp,

and fuel level if the controller does not come thus equipped. Bleed the air from both fuel

systems and the coolant system; test the WVO lines first with diesel fuel.