Copyright Nistune Developments 2014-2017 rev4

Boost Sensor Register Nissan has added an additional boost sensor to the Nissan ECU: Boost pressure sensor. Uses a vaccum/boost equipped MAP sensor capable of measuring up to 5.12 volts at 18psi. To view the boost pressure enable this consult register. Nistune will display the value in volts and PSI on the gauges. The ECU will raise a DTC fault at 4.84 volts (4840mv) when it reaches approximately 16 PSI. This limit can be increased to 5120mV (the maximum boost sensor reported voltage is 5080mV) to avoid DTC codes from being reported.

TP Load Register BFuel Schedule (Theoretical Pulsewidth) is the replacement TP (load) parameter used with NEO ECUs. This parameter used for maptracing the columns on the fuel and timing maps and is a preliminary calculation used for final injection

Consult Register Selection

Boost Sensor Usage NEO equipped ECUs use the boost sensor for several purposes: (a) MAF compensation Resizing MAFs using the NEO ECU can result in mismatched atmospheric pressure compared to expected measured ECU load measured by the MAF sensor. MAF sensors convert airflow to voltage and the Voltage Quantifer converts this into a value used to calculate TP = (VQ airflow value / RPM) x K constant

Upgrading to a larger flowing MAF sensor will subsequently increase the total theoretical pulsewidth (TP) since K constant (TP injection multiplier) is increased. The boost sensor compensation for MAF voltage can have a temporary effect at initial acceleration, sometimes resulting in delayed acceleration. Resolution : Retain factory load (TP) scales Fuel load scales range from 24 .. 160

Ignition load scales range from 16 .. 208

Some further analysis of the ignition map shows the last two columns contain safety timing numbers (located at TP columns 192, 208) with timing values 13 and then 6. This is to cover the event of over boosting. If making fuel and load scales the same scale values, we recommend copying the fuel scales (24..160) to the ignition load scales and still using safety timing numbers in the last column (now column 160) After resizing for MAF and injectors, adjust K constant so that the TP cursor operates within these scales (eg upto TP = 144) and adjust the Total Injection Multiplier (or Total Injection Divisor for non-FP firmware ECUs) so that you have stoich mixtures with near 0% trim (STFT/LTFT) at cruise when closed loop is enabled.

If you still encounter issues with acceleration enrichment when accelerating, then look further at adjusting the volumetric efficiency map where adjustments based on TPS and boost sensor input are necessary Important Update: Electrical or hose disconnection of MAP sensor Previously this document has suggested that disconnecting the MAP sensor electrically will remove the effects of acceleration enrichment problems. However this raises a fault code and will result in problems

After this it was necessary to untick the DTC fault filters for the boost sensor to remove the DTC fault and check engine light. It has been found that disconnecting the MAP sensor hose results in using a default voltage of 2.70 volts and will not raise fault codes, but still will result in problems. Factory Nissan ECU code will trigger a sharp drop in TP when the MAP sensor does not report valid boost readings, including when there is a decrease throttle position (TPS) voltage. Example:

With a steady RPM (red) and increasing MAF (blue) but the slight decrease in throttle position (green) we notice the Nissan ECU has dropped the TP load (purple) As a result of this the injection time (yellow) has gone lean and timing (green) higher under these conditions, which may depending on scaling of the maps, result in engine damage if gone unnoticed. Ensure the boost sensor remains connected, and operates as normal to avoid lean cuts due to a drop in TP occuring. In vehicles without boost sensor connected, add a line to the boost sensor from the ECU and install a sensor.

(b) Over boost limitation The boost sensor is used for over boost fuel cut operations performed by the ECU. These tables have replaced the 'TP load limit' tables used in older Nissan ECUs The tables are specified in millivolts which is the measurement of the boost sensor 5100mV = 18 psi 4340mV = 12 psi When using the factor boost sensor, when the boost reaches the limit in the table the ECU will start a counter and once the counter has reached the specified value (default value of 10), the ECU will perform a fuel cut (boost cut)

Increasing the values of these tables to a maximum of 5100 millivolts will work upto 18psi for safely limiting boost levels. Above 18 psi to avoid the fuel cut increase the counter to increase the time at over 18psi before cutting fuel (maximum of 255 will effectively disable the cut completely)

Important note: When the boost sensor is disconnected, and there is a Boost Sensor DTC fault code, the ECU will instead use the TP limit tables and counter

These tables work similar to earlier ECUs when there is no boost sensor available. The current Theoretical Pulse width (TP) load is compared against the table value for the given RPM. A counter increases upto the limit and then a fuel cut is performed by the ECU Increase the values in the limit table to remove the injection cut when the boost sensor is not used.

(c) Reporting current boost level Nissan consult will report the current boost level as a voltage (which can be converted to PSI and is displayed in Nistune from version 1.2.14 upwards)

Boost Pressure Sensor Gauges (view from Knock Warning panel)

If the boost sensor voltage exceeds the specified max voltage the Boost Sensor DTC code will be raised. This is about 16-17psi

Below 60mv the DTC is raised (primarily for detecting a disconnected boost sensor). Note setting to 0 will not clear the DTC code if the boost sensor is disconnected Above 4840mv the DTC is raised. Increase this to 5120mv to increase to 18psi before the DTC code is raised. If you are going above 18psi then disable the boost sensor filter flags

Fuel maps NEO equipped ECUs now use two separate fuel maps. These function differently to earlier Nissan ECUs

The primary fuel map no longer uses the 'O2' feedback flag overlay over the map like used with earlier Nissan ECU implementation Values equal 128 indicate the closed loop area of the fuel map Values above 128 command adjustment to the base fuel mixture. Increased values result in additional fueling

AlphaN/Increase Fuel (vs TPS) The Alpha/N table functions the same as with earlier ECUs. The TPS voltage is compared against the table value for the current engine RPMs If the throttle position exceeds the current table value then the last column of the fuel map is used instead of the map traced cursor position.

Take note of the current TPS cursor value and the maptraced cells in the Volumetric Efficiency (VE) map (covered next page) Note: Take care whilst making adjustments to the fuel map. Any adjustments not affecting the ‘injection time’ and subsequent AFRs should be observed, where the TPS is higher than values in this table Either:

(a) Increase the TPS voltage levels in this table to use the full fuel map. Then tune the fuel map accordingly, keeping in mind the VE map may reference values below the threshold in this table

(b) Adjust the fueling using the last column value of the fuel map. This column is used when TPS exceeds the voltage values in this table (Tune for safest AFRs in the event of high/full throttle and maximum boost)

Volumetric efficiency Table is used in addition to the fuel map to trim mixtures based on TPS vs RPM scaling. VE maps are used adjust enrichment based on TPS position for all later model Nissan ECUs TPS Voltage Quantifier TPS is calculated firstly by converting TPS raw voltage to a TPS reference position

The TPS reference position is then divided by RPM and used to reference the VE map index table. VE Map Index table Boost sensor available: The value in this table is then multiplied against the boost sensor table Boost sensor not available: Value is divided by two The calculated value is used to index the VE map

VE Map Boost Index table The values in this table are a percentage multiplier against the values in the VE map index table. For example this table is indexed with current boost voltage of 3840mV (3.8V) Take 110 from the previous table x 76.5% = TPS VE index value of 83. So as boost increases the reference to the VE table increases to the right.

Fuel Volumetric Efficiency Map These maps are used in conjunction with the fuel (and effectively Alpha/N tables where TPS value exceeds the table value and uses the last column of the fuel map)

Horizontal indexing takes the TPS index table value and multiplies against the boost multiplier value. For example, the TPS index table value (above) of 110 determined then divided by 50% and used to reference column 96-112 in the VE map. The TPS position is correctly traced from Nistune 1.2.10 versions upwards by direct reading internal ECU memory. The trace is subsequently not available in normal consult (stream mode) and will update slower then other gauges. To enable the TPS position in stream mode, Nistune 1.2.54 versions upwards must be used. This will add an extra parameter to the factory consult table 'Adjusted TPS VE index' at consult register location 0x19 (Reserved by Nissan). To add the parameter, connect to consult which will add then register. Then disconnect and reconnect to see the parameter added to the list. Tick this item to get tracing in stream mode.

Tracing display shown below as VE/TPS:

ABS / TCS Disabling Functionality When using NEO ECUs in other vehicles without the supporting ABS and TCS equipment, fault codes will be raised and vehicle operation may be affected

It has been found during recent investigation into the NEO ECU program code that disabling filter flags for these features will prevent the ECU code from calling those functions

Unticking both of these items will disable the Code 44 (ABS/TCS comms circuit DTC error)

Unticking both of the motor throttle circuit will remove the Code 46 (Throttle Motor Sensor DTC error)

Feedback Control Flags Feedback control flags have changed for this ECU. These are available from version 1.2.14 onwards Knock analysis can still be disabled and disabling closed loop short term uses a different register (not tested at this time). Internal Nissan diagnostics (not recommended for customer usage) have been added for completeness only

Fan Control Table This table is available in the 'Misc tables' section of Nistune

There are different settings depending if the Air Conditioner switch is on / off Right Click the table to view as 'FILTERED' values 96 = Fans on Adjustment of Fan Control speed 2 (middle band) can be made using this parameter: