Quote:
Originally Posted by Ron
Hey guys, looking for some advise, here's what happening.
1) At idle when I blip the throttle (up to 2.5k - 3k) AFR goes a little rich as expected and then it leans out to high 15's - 16s as rpms are coming down before stabilizing to 14s.
2) While cruising and BARELY on the gas, AFRs go crazy and change from 13s to high 16s back and forth really fast. Again, gas pedal is BARELY depressed, almost disengaged when this happens. You can feel the engine stutter.
3) While cruising and letting off the gas completely, AFR gauge is supposed to go full lean immediately correct? Before it does that and right after I release the throttle, it hangs at 16s-17s for about 2-3seconds and it then goes full lean as expected... OR... it will go full lean when releasing throttle, jump back to 17s for a second or two and then go full lean again as expected.
I assume these are all being caused by the same thing.. any ideas on what needs to be adjusted on the map or do you guys think something other than the tune could be causing it.
Thanks!
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1) This is common. The car adds fuel as necessary for throttle tip-in, but on engine deceleration it turns off the injectors and the car acts as a big air pump.
2)It is common for the AFR to jump around during part throttle driving. This is because a MAF based car is going to constantly be making adjustments to target 14.7AFR which is ideal for pump gas. The choppiness could be a result of a erratic fueling map, but most of the time its from having choppy timing tables.
3)In my opinion this most likely has to do with the way the transmission computer controls the throttle for the synchromesh shifting. I do not tune the cars personally here just trying to jump in with some useful info. Todd our tuner might have a different opinion, he is out tuning currently so I didnt have him around to ask.
Thanks,
Alex Goodwin
AlexG@motionlabtuning.com