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UpRev: When to adjust K factor vs MAF tables

Practical Reflash Tuning

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Discussion and questions related to the course Practical Reflash Tuning

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Background:

I've recently swapped from one OEM ECU to another on my Nissan VQ37VHR (have gone from a 2009 auto to 2011 manual ECU). The new ECU seems to run richer than the old for what ever reason. To establish this I've got a zero'ed out fuel compensation table and fuel trims, and am targetting a fixed AFR so the ECU operates in open loop at everything outside of idle.

With the above setup in place the logged AFR's from the 2x OEM wide bands are approx 10.x against targetted 12.x. With the old ECU it was fairly well spot on.

Questions:

What are the considerations around MAP table alterations vs K factor change to bring the AFR's inline (target vs measured when in open loop) ? Is it preferable to use one method over the other and if so why ?

What knock on effects are there to be careful of when going with one method over the other ?

Your K value is a Constant for multiplications in relation to the injectors. If you've not changed the injectors then I'd be looking at the MAF calibrations with the fuel compensations zero'd out.

Are you sure the OE widebands are reading correctly?

Here's the updated Uprev tuning guide (V2) :

UPREV Tuning guide V2

The ECU is the only thing which has been changed. Fair to say that they should not be reading any less accurately now than prior... But I have nothing to validate this claim against.

I have had the car on the dyno with external wide band and did not note it being inaccurate.

have you got a comparison of the of the two tunes? K-Values, MAF Values ETC?

I do yes, the K values are the same and the MAF tables do vary but only by up to about 0.5% at the high flow end.

I'd hunt deeper for a root cause first.

Have you verified whether those 2 vehicles use the same part numbers for critical engine sensors like the front o2 sensors, MAP sensor, water temp, air temp, etc. I'm wondering if there's a discrepancy caused by differing sensor scaling.

If sensor scaling for all critical sensors is visible in your tuning software, and the same between the two ECUs, then this likely is not the issue.

Is the injector data all the same?

This is the same car, same engine etc ... no changes other than swapping out one ECU (JDM 2009 Skyline 370GT Automatic) for another (USDM 2011 370Z Manual). Both cars were equipped with the same VQ37VHR engine.

From data logging in UpRev all of the 'general' sensor readings look to be as expected.

Have checked the injector parameters and they are all the same between ECU's / ROM's

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