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afr changing after tune/drive


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fitted a link g4+ atom the other night went out and did some light load tuning all afrs were very ner my target on light load , I left the car Idling for some time at my buddys house then drive home rite away I could see afr was much richer as u can see in data log , after a long drive it will lean out again , its going as rich as 12.8 when it was tuned for 14.7 ish ,


ecu is wired to batch fire injectors 2 per out put (only using out put 1&2) injectors are rx8 yellows , map sensor is cheap but looks to work ok altho calibration was not liner when I set it up with mityvac , dead times are left to default but I have looked and the battery v dose not same to be the issue

other notes on the car , ive no tps fitted and no air inlet temp sensor tho I doubt this is a problem as Ive don't this before with out faults


thanks for any help  

Edited by mi16chris
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I've had a look at your log file. I can see how the lambda reading is leaner as the log goes on. When I check the Fuel Table 1 reading at the same points it is even. To me this indicates that either the ECU is applying a trim of some sort (which I do not see in the log file), or something like temperature is effecting the tune. We do highly recommend running an IAT sensor. Can you also please supply your base-map?


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Hi mi16chris,

I haven't looked at your files but it is just a known, that when air temps rise the air is less dense and you require less fuel.

You state you have no IAT sensor, then you can not apply any heat soak or reverse cold air corrections to your tune.

You said cruising your tune was good, but then you left the engine running at your friends house without driving air flow, the latent heat build up in the engine bay and components would go through the roof.

So with heat soaked inlet manifolds etc the air is less dense but your ecu is still applying the same amount of fuel, hence for the rich mixtures.

Now if you look at it from the opposite perspective in winter the air is cooler and more dense.

This means you will require more fuel and you will find your AFR will trend LEAN.

Your call but I advise fitting a TPS sensor so you can employ throttle enrichment settings, for smooth responsive acceleration, also the ability to use TPS input settings to activate Auxillaries etc.

I also obviously strongly recommend the fitment of an IAT also.

Your choice what you decide to do as it is your car, but the precision of your ECU will never function at it's true potential without setting it up properly.




Edited by Dave Kriedeman
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Thanks for the input , today I wired up the stock Toyota iat sensor even tho it's mega slow I could see it was a small part of my problem , I could see as the iat went up the afr getting richer , i also found out my map sensor was going +- 10kpa after a drive, I've a new gm iat sensor ordered and gm 3 bar map sensor 


Thanks again for ur input 

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