Lean spikes commanded vs actual AFR

[billyjo]

First let me start by saying I'm using EFI Live with COS3. I've been working on setting up my VE table but I noticed some cells that are way out of wack with the rest.

I then started looking VERY closely at my logs and noticed that everytime I step on the gas and go into a KPA above 95 I get these lean spikes when my commanded AFR goes to 11.7. Is this lean tip in that people talk about? How can I make it go away or is it just normal and I shouldn't be worried about it?

Thanks,

Bill

[Tordne]

That spike is actually enriching, going richer. AFR's < 14.63:1 are rich, and AFR's > 14.63:1 are lean.

When you step on the gas one of many things (PE, B3647 in COS etc.). It richens the fuel mixture to protect against knock.

[billyjo]

I understand that, the spike I'm talking about is where it rises to 16+ before it drops down to the commanded 11.7.

Thanks,

Bill

[Tordne]

Doh! I was looking at the wrong PID

[joecar]

Billyjo,

Is your MAF disabled/disconnected (should throw DTC P0103)...?

After doing AutoVE, what are you BEN's...?
After filtering/averaging, they shouldbe 1.00 +/- 0.02 for all cells hit.

If that is the case, then look at the OLFA table and PE vs RPM table and see what AFR's are being commanded (the richer of these 2 tables wins);

In the scan tool position the cursor on the lean spike, and you should see the cell(s) highlighted in the OLFA/PE/VE tables...

Sorry I don't have the ids for those tables, I'm on a different PC right now...

Joe

[dc_justin]

Billyjo,

This is unfortunately a common occurance for us roots-blower guys. These things seem to build boost faster than the PCM can adjust for it.

One thing you can do to help get it to drop your commanded AFR faster (and reduce lean spike duration) is to make sure your PE settings are similar to the the following:

B3608 = 0
B3643 = 1.0
B3644 = 0
B3645 = 0.1 <-- Delays the transition out of PE. Will prevent knock from occuring when you quickly pop off the throttle while in boost.
B3609 = 0 for all values

[joecar]

...Radixed LQ4 with 3.2 pulley...

ah... that failed to register in my mind...

[Whippled 496]

Billyjo,

This is unfortunately a common occurance for us roots-blower guys. These things seem to build boost faster than the PCM can adjust for it.

One thing you can do to help get it to drop your commanded AFR faster (and reduce lean spike duration) is to make sure your PE settings are similar to the the following:

B3608 = 0
B3643 = 1.0
B3644 = 0
B3645 = 0.1 <-- Delays the transition out of PE. Will prevent knock from occuring when you quickly pop off the throttle while in boost.
B3609 = 0 for all values

Hey Justin, why not have something like 0.1 or 0.01 in cell B3643? You want the transition to be as fast as possible right? Can you explain what you mean, i probably just dont understand it well enough.

[dc_justin]

Hey Justin, why not have something like 0.1 or 0.01 in cell B3643? You want the transition to be as fast as possible right? Can you explain what you mean, i probably just dont understand it well enough.

B3643 is the size of the step in the transition of the commanded fuel.

If your current commanded EQ ratio is 1.0 and your target is 1.25, if you have a step size of 0.01, it will take 25 steps to go from 1.0 to 1.25. According to the description, there are approx 20 steps a second, so it would take more than a full second to reach target.

With a step size of 1.0, it will hit target with the first step.

[Whippled 496]

B3643 is the size of the step in the transition of the commanded fuel.

If your current commanded EQ ratio is 1.0 and your target is 1.25, if you have a step size of 0.01, it will take 25 steps to go from 1.0 to 1.25. According to the description, there are approx 20 steps a second, so it would take more than a full second to reach target.

With a step size of 1.0, it will hit target with the first step.

Ahhh, got it. That description for table B3643 takes a little reading into to completely understand it. Thanks man, by the way....you better to get to work on redirecting that domain name, still says its for sale...LOL