Understanding Air/Fuel Ratio
07-02-2003, 03:19 PM
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Understanding Air/Fuel Ratio I am an altitude of 5200 feet. A friend has an ATI S/C on his Vette that was PCM tuned by Ed Wright. Anyways, Ed came out here to put the final touch on the tune and said that he made the AFR richer in case my friend "drives off of the mountain" and he doesn't want him to be too lean at sea level.
My understanding is that the AFR is a RATIO, and the PCM will adjust for it as the altitude changes. At higher places, the PCM will add less air to maintain the same ratio, and lower altitudes would get more to keep that RATIO.
Why would Ed Wright make it richer here so that it would not be too lean at lower altitudes? What am I missing?
My understanding is that the AFR is a RATIO, and the PCM will adjust for it as the altitude changes. At higher places, the PCM will add less air to maintain the same ratio, and lower altitudes would get more to keep that RATIO.
Why would Ed Wright make it richer here so that it would not be too lean at lower altitudes? What am I missing?
07-02-2003, 09:59 PM
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Re: Understanding Air/Fuel Ratio Seems kooky since you have a MAF (_Mass_ airflow
meter, which tells you true air quantity with no
regard to density / pressure / elevation) backed
up by MAP (true intake pressure, ditto).
Sounds like somebody's mixing (heh) carburetor
lore with EFI.
meter, which tells you true air quantity with no
regard to density / pressure / elevation) backed
up by MAP (true intake pressure, ditto).
Sounds like somebody's mixing (heh) carburetor
lore with EFI.
07-03-2003, 04:18 AM
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Re: Understanding Air/Fuel Ratio ditto on that I thought that that was one of the things that the MAF was designed to do, make the car be able to go to almost any altitude with no problem......
07-03-2003, 03:37 PM
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Re: Understanding Air/Fuel Ratio The computer can compensate for some changes but not all. If that was the case you wouldn't need to tune it.
You can buy an EFI system that will handle the tuning for you and it will even optimize its own tune but that costs $9K last time I checked.
If its richer it will compensate for what the ECM can't for the conditions at low altitudes.
You can buy an EFI system that will handle the tuning for you and it will even optimize its own tune but that costs $9K last time I checked.
If its richer it will compensate for what the ECM can't for the conditions at low altitudes.
