This feature has been deprecated and is no longer able to be adjusted in the software. Most tables are marked FEATURE DISABLED to let you know those tables are not valid any longer. In most instances the tables are no longer able to be edited in any way and are defaulted to standard values. In other cases the table values can be edited but are disabled and won't impact vehicle operation. |
If you are new to engine management system tuning, we suggest gaining general knowledge and understanding of both calibration and engine dynamics before proceeding at your own risk.
This second of the tuning guide is to be used for speed density based tuning. Much of the logic and tables are the same for MAF or speed density so much of this second section of the tuning guide is a duplicate. However, there are critically different fuel and load calculation differences across these two tuning types and this section focuses on SD tuning strategies.
GT-R Accesstuner software for SD integrates custom logic and new tables to allow SD based tuning. Once you have selected the appropriate year and world region of the car the proper base parameters are automatically loaded to allow SD tuning. There are a few key parameter that need to be set up in order to create a base Speed density tuning calibrations.
Speed density based airflow calculations and fueling commands require an accurate measure of air temperature. The best place to measure air temperature is after the intercooler and just before the manifold. It is the temperature of the air entering the motor that is most important. The standard SD air temperature correction table is set up to produce fueling offsets consistent with this sensor placement. It is highly advised to move the stock MAF and air temperature sensors to a location just before the throttle body. Configured in a boost tube after the intercoolers the MAF sensors along with their associated Air Temperature Sensor are in a “blow through” configuration.
The ideal air to fuel ratio depends upon fuel quality. Higher octane fuels are more detonation resistant and therefore can be run at leaner air to fuel ratios. Leaner Air to Fuel ratios produce higher power but also create more heat. Excessive heat can lead to detonation. Lower octane fuels such as 91 octane or 95 RON are more prone to detonation and therefor require a richer air to fuel ratio. Rich air to fuel ratio combustion produces less heat and therefore less detonation. We have found that the GT-R engine can run mid to high 11 Air to Fuel Ratios (AFR) when running quality fuels. Lower quality fuels require mid to low 11 air to fuel ratios.
SD based tunes DO NOT directly measure Air Flow through the MAF sensor. Instead Air Flow is calculated based upon the ideal gas law. Air flow estimated based upon the manifold air pressure and air temperature. These two measures combined with an underlying estimate of engine volumetric efficiency (VE) allow the GTR to be calibrate using manifold absolute pressure as the primary load reference.
SD based tuning utilizes a slightly larger collection of tables to tune for proper AF. Some of these tables are common to MAF based tuning strategies. Tables and values that impact fueling for SD based tuning are:1) injector scalar 2) injector latency multiplier and offset 3) Fuel multiplier (leave this STOCK) 4) MAF curve A and B ) 5Primary fuel and ) 6volumetirc efficiency
MAF based tuning the GTR references AF ration at all times and adjusts fueling with Sort and long term fuel trims.
Set up the calibration for SD. Open a default SD calibration in the software and set up for the configuration of the car. Set up injectors, FM, MAF, and Primary Fuel table to best match the configuration of the car as well as the fuel type. The default VE table is a good starting point for mildly modified cars.
Run the car under low load conditions and adjust the primary fuel and VE map to create the smallest possible short and long term fuel trims. As in MAF based tuning, The R-35 GT-R uses two internal wide-band oxygen sensors to monitor fuel mixtures on left and right engine banks. The ECU will constantly adjust fuel to reach this air to fuel target. As a result, the values in Fuel-Low Det are a closed loop target that the ECU will always work to achieve. The active adjustments made by the ECU are monitored at STFT (ALPHA) B1 and STFT (ALPHA) B2. These short-term fuel trims will gradually enter a long-term learned state that can also be monitored - LTFT (KBLRC) B1 and LTFT (KBLRC) B2.
Step 3: Run the car at increasing higher manifold pressures until the VE map is tuned over the full range of pressures at which the motor will be operated.
Step 4: Adjust the Speed Density – Air Temperature Correction: The default Air Temperature fuel correction works well when the air temperature sensors are placed in the boost tubes just before the manifold. Air Temperature based fuel correction can be adjusted for specific vehicle/air temperature sensor location. Below is an example of a fully tuned Volumetric Efficiency table for a GTR with larger turbochargers. Note the VE compensations are slightly higher for this car than those indicated in the default table for use with more stock like components
Below is an example of a fully tuned Volumetric Efficiency table for a GTR with larger turbochargers. Note the VE compensations are slightly higher for this car than those indicated in the default table for use with more stock like components
Fully Tuned VE table for 2009 GTR with larger turbochargers. Note higher than default values and the generally smooth shape of the VE relationship as manifold pressure increases.