I did a search on A.S., and read alot of intresting stuff. About 100% of the information stated that A.S. will change driveability after several hundred miles etc., etc. What I did not find was exactly what is being changed?

A/F?
Shift?
MAF?
Other?

Alot of folks stated that their vehicles seemed more "tame" (my word) after A.S. kicked in. Yet Mike at TP has stated that power will increase after A.S. settles in.

So I am just wondering exactly what things A.S. modifies over time?

thanks in adavance for your insights.

 

Fuel trims and trans shift schedules mostly.

 

I actually did datalog my Exp and am awaiting the review from TP. I know I logged fuel trim, but I really have no idea what that means.

Thanks for your prompt reply on the A.S. adjustments.

 

There's short and long term fuel trims. Both are adjustments the PCM makes to add or remove fuel accordingly.

Think of short term fuel trims as fast adjustments made on the fly. The primary purpose of short term fuel trim is to make the upstream O2s switch from lean to rich. If the upstream O2s start reading lean, short term fuel trim will gradually increase, injector pulse will increase, fuel pump duty cycle will increase, to add more fuel, whatever it takes to make the O2s start switching again. Conversely, if the O2s start reading rich, fuel trims go down, injector pulse goes down, etc. Typical short term values should vary no more than about 5% positive or negative, the closer to 0, the better.

Long term fuel trims are adjustments made based on what the short terms are doing. If the PCM sees that the short term fuel trim is adjusting further out of normal limits (roughly more than 5% either way), it'll step up long term fuel trims to try to keep the short terms as close to zero as it can. Typical long term trims can be 10% positive or negative. Anymore than 10% correction either way, something's wrong. Once the fuel trims hit their limit either way (15% or more, typically), the check engine light will come on with lean or rich codes depending on what the trims are.

 

Quintin, you guys have to know too much now. I used to adjust my timing by twisting till it sounded peppy, and adjust the old holley till it smoothed out. It has changed a bit.

 

Thanks for the textbook explanation! Now I have some idea of what I'm looking at

 

And who says you dont learn something new everyday. Thanks for the great info

 

This long term trim also makes it possible to account for cylinder and general wear (within limits) affecting power as time goes by.
The PCM records the time it takes the crank to react to a single cylinder's power contributuon.
As the time gets longer, the tables adjust until their limits has been reached..

 

Drive it like a grandpa (like my grandfather), she runs slow. I had his truck for a few weeks and she was like a different truck when I gave it back to him.

Adrianspeeder