Lean spike at shifts, auto tranny
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Car: 1991 Firebird
Engine: 350,Dart Heads,Weiand In,Roller Cam
Transmission: 2400-Stall, 700R4 w/ Kit
Axle/Gears: 4th Gen 3.42 disc (I wish)
Lean spike at shifts, auto tranny
I am in the process of tuning my TBI engine with an Innovate WBO2 I just aquired. It is amazing how far off the tuning was (excessively rich). 454 TBI speed density 8746
Here is a log from a WOT run. You can see the MAP changing when the car shifts, looks like first gear had some tire spin. I am having issues logging RPM, so that sucks. Anyways does anybody know where these lean spikes are coming from? Also I have a super rich condition at the beginning of the WOT, but that maybe to much AE.
Thanks in advance!
Here is a log from a WOT run. You can see the MAP changing when the car shifts, looks like first gear had some tire spin. I am having issues logging RPM, so that sucks. Anyways does anybody know where these lean spikes are coming from? Also I have a super rich condition at the beginning of the WOT, but that maybe to much AE.
Thanks in advance!
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Car: check
Engine: check
Transmission: check
Re: Lean spike at shifts, auto tranny
I didn't look at the image, bmp's are too large.
However, the lean spikes on the shifts are typically due to the rapid change in airflow. At high RPM the airflow strips the fuel from the runner walls. As the RPM drops fuel is deposited back onto the runners, causing a quick lean spike.
I've been able to reduce (sometimes eliminate) the lean spike by increasing the VE at the shift point. Along with some additional VE at the point where the RPM falls after the shift.
RBob.
However, the lean spikes on the shifts are typically due to the rapid change in airflow. At high RPM the airflow strips the fuel from the runner walls. As the RPM drops fuel is deposited back onto the runners, causing a quick lean spike.
I've been able to reduce (sometimes eliminate) the lean spike by increasing the VE at the shift point. Along with some additional VE at the point where the RPM falls after the shift.
RBob.
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