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# Compensation

### Tech Articles

Discussion and questions related to the course EFI Tuning Fundamentals

I have some questions in regards of fuel compensation etc.

Following the seminar we have the rule of 2,5% average , setting at 20 deg 0 and then below that we increase or if lower we decrease . But does this rule apply also for base maps ? For example if the ecu that we are using has a base map in it and has example :

-17=6.9

0=3.8

17deg= 1.1

44deg=0

75deg=-0.5

And so on . Should in this case replace even the deg with closer temp and also set 20deg=0 ?

Also does the rule of 2.5% apply also for medium load and high load or is another approach for it ?

My suggested guide of 2.5% per 10 degrees IAT shift has always worked pretty well in my experience. Of course you may find some situations where the comp table can benefit from tweaking but this is a pretty good starting point. If you have a 3D compensation table then I generally reduce the amount of adjustment at lower loads to reduce the effect of heat soak after a hot restart. If you're tuning an ECU on a turbocharged car where the IAT sensor is fitted in the MAF sensor (pre turbo), then this isn't necessarily going to be indicative of the actual intake charge temperature, and hence you may find my suggested comp table is less effective - Of course in this situation the best option would be to fit an IAT sensor in the inlet manifold of IC pipe pre throttle body though.

Thank you for the info .

So I should change it , regardless that the figures that I used in my example was from a base map . I do understand that the base maps is to get the car to start and saving you some time in tuning or as guide line . As I understand it , I assume the compensations are to cover a wide range of temp that would get the car started almost anywhere on the planet , so we should adjust those also , am I correct ?

Also seeing other seminars on the Link and most likely on other standalone ECU's you can set up a 3D axis , with TPS % . So that keeps a constant 20deg=0 regardless of TPS % , but does that apply for the other deg also?

For example 30deg=-2.5 regardless %TPS and 40deg=-5.0 regardless %TPS ?

Also does this also apply when we are tuning the car in hot or cold weather ? For example if we tune a car when it's 28/30deg , do we still set up 20deg=0 .

Also is there anything similar for water temp comp. ?

I would always start a fresh tune with the recommended trims for IAT comp.

If you have a 3D comp table then I will usually reduce the amount of control the comp has at high temp and low TPS/load to reduce the affect of heat soak. If you use a 2D table then you may find the comp is a little aggressive after a hot restart and the result is the engine runs lean for a couple minutes.

Regardless of the actual temperature you're tuning at, I always set the 20 deg row as the zero reference point.

Coolant temp comp is all about maintaining your target AFR when the engine is cold as this will require a larger volume of fuel compared to when the engine is at operating temperature.

Thank you for the clarification .

In terms of the coolant temp comp , do we set up the whole map on and then go from there ? Set 90deg=0 and then do some cold start ups to to see where afr is sitting and start adding 2-3% until we see the afr that we want on cold start up and then wait till we get higher etc. ?

Have a look in the webinar archive as we did a webinar covering cold start tuning. Essentially you want to ensure the coolant comp map is zero in the normal operating temperature zones. Tune your main fuel table at operating temp, then perform some cold starts and adjust the warm up zones.

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