In this article we tackle the Nissan OEM method for defining the injector latency for the modern Nissan Port injection engines i.e. GTR and 370z.  If you were looking for RaceROM injector scaling info for GT-R visit GT-R RaceROM GTR Injector ScalingCalibration.  The Nissan strategy varies dignificantly from the typical aftermarket injector latency definition but still gives good results when tuned correctly.  We tackle that using the following 1D and 2D maps.

• Injector Flow Scaling (OEM and RaceROM)
• Injector Lag Time Multiplier
• Injector Lag Time Offset
• Injector Minimum Open Time

They can all be found under the "Injectors" section of the "Fuelling" maps.

Injector Flow Scaling and Minimum Open Time

Injector flow scaling is a simple concept and the injector scaling used should be close to advertised size, however we do tend to see that aftermarket injectors generally need to be lower than the advertised flow rate. Keep in mind that the ECU does not know the actual injector size but instead uses a multiplier value scaled to match the stock injector size. We find that our own EcuTek 1050cc injectors are best represented by a flow scaling of 975cc.

There is an OEM value in all ROMs which we DO NOT recommend using as it is limited to 800cc. Instead we recommend you use the Injector Flow Scaling (RaceROM) map. With this map you can select Injector scaling values for each of the 4 Map Switch modes. This is useful if alternate fuels are used, for example if using E85 you can simply reduce the Injector scaling size by 30% and the ECU will deliver +30% more injection volume. The top value is for mapswitch MODE 1 the bottom value is MODE 4.

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EcuTek can supply high-quality Bosch Motorsport injectors that have a rated flow of 1050cc, (enough for 1000+bhp on a GT-R) they are tried and tested and they do not suffer from some of the idle and black smoke issues that some other well known brands do. See the webstore and Nissan GT-R Fuel Injector Installation for more information.

The other Basic map is the Injector Minimum Open Time value which is simply a minimum time that the injectors will be open for. If you have larger injectors this should be reduced to avoid over-rich mixtures at idle and low loads/engine speed.

Injector Latency (Lag Time)

From what we understand Nissan do not use a standard injector curve because the IPDM (Intelligent Power Distribution Module) constantly maintains injector voltage very close to 14V (unlike other manufactures), for low voltage cranking they use the cranking injection table to compensate for battery voltage drops.

Nissan use two values to calculate the physical lag time of the injectors, these are the Injector Lag Time Offset and Injector Lag Time Multiplier. Because the injector voltage is accurately maintained at 14V by the IPDM The most important latency value is the Injector Lag Time Offset value which is the time take for the injector to open at the standard fuel pressure and an injector voltage of 14.0V. This value should be set to the injector latency value of the aftermarket injector at 14V (at operating fuel pressure).

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The Injector Lag time multiplier is used on the rare occasion that the lag time needs to be estimated when the IPDM is not maintaining 14V correctly. It does this by applying a multiplier to the latency at 14V giving a final lag time value (see the image below), while this is not as accurate as other methods it does give repeatable results. You shouldn’t need to adjust the Injector Lag Time Multiplier as it will be close for most injector sets.

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If you do need to calculate this value, "the slope" at 13.67V you could use the latency Time (T) in milliseconds (ms) at the specified voltage (V) values to calculate the slope of the curve

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and this should be close enough. (choose 13V (V₁) and 14V (V₂) if available in the injector data).

Hopefully this will give you enough information to set up larger injectors in Nissan vehicles with great results.