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Thread: tuning for changes

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    Forum Newbie Array fastow's Avatar
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    tuning for changes

    lookin for opinions sure i will get some.. i am new to this tuning stuff i have dealt with carbs and such so i pretty much understand fuel air ratio rich lean and all that put optimum timing in there to ... so lets say i have a NA engine few mods open exhaust aftermarket intake and go get a tune they move the rpm limiter up tune to optimum performance so they say i dont see it unless i see dyno stats who is to say. so then i add maybe a header of some kind maybe cam change or like a le5 intake can the computer compensate my thinking is would that be any different than lets say a air filter just about needing cleaned on a super hot day making the engine shy on air VS: nice cool day dense air and nice clean filter letting that engine really get a gulp of air would think the ecm should be able to compensate for some but how much ???

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    Let's use cam swap for this example for the ECU "compensating". If you install a different cam it can enrich you in some parts of your maps, lean you in others. If the ECU you have doesn't use a MAF sensor, then the ECU estimates the airflow through the motor based on a combination of IAT, MAP, TPS, and RPM and then calculates the proper amount of fuel to add to that. If it's wrong (because of new parts and non-tuned) then it will sense that with the O2 sensor (if the car is running in closed loop) and learn its deviation and store it in the Lt/St trims. As you operate the motor through its range and trim blocks it will adjust itself in each block, but it is slow and clunky and not precise. If the vehicle is MAF controlled, it will have less of an impact on the running fuel calculation (since MAF combines with IAT to read air flow rather than calculate an estimate) but many ECU's revert to speed density type tables to calculate the fuel adjustment for acceleration/deceleration, idle, and fail safe if the MAF fails.

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    Forum Newbie Array fastow's Avatar
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    Whoa you just about goin over my head lol so i have a ecm that was done with a vehicle on a dyno i done a engine swap into another vehicle we are talking jbodys but using same ecm with the engine i don't know if he had a header or not or open exhaust i am sure that would make a difference on how much cfm is goin though the engine i have had different air intakes exhaust even swapped cams i have watched the plugs they have good color when i have checked them. any way i would like to know more about engine management on these engines thanks again

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