felpro A/F ratio - erratic

[John Snyder]

I have installed felpro unit on relatively stock 86 T/R and the only problem I seem to not be able to "tune" is a very erratic A/F ratio that seems to run based on where I put the VE table, but I get several Dips to 9.19 (lowest the O2 will read) and then spikes back up to 12.5 (normal). I have tried to prevent this by selectively leaning out cells but have had no/little luck...I am afraid to get too lean under full boost (17psi).

Thanks for any help.......

 

[Bobo]

So if you've tried to change ve values and not had any luck, maybe you're getting a false signal? There's a test to check if the O2's ok, I can't think of it now but you can look at some other posts here and see where to look for it at. It's a V reading you can see from the dashboard. Does the car feel rich (spit and sputter)? I've had my ve #'s too high and bottomed out the a/f and I knew it before I even looked at the data log just by how it cut out. Is there just a certain rpm/kpa cell or few cells it happens in? Good luck.

 

[Mike Edwards]

Are you just changing one cell or a group of cells. In the VE table the VE for a given RPM and MAP is interpolated from not only the cell, but the surrounding cells. Try changing a group of cells. You may already be doing this, but if not give it a try. HTH

 

[Bobo]

Mike's got a good point there, I made that same mistake at 1st. Are you making big changes? I had to change my ve #'s quit a bit when it was way rich.

 

[TurboTR]

The erratic readings- are they happening while the throttle is steady or while the throttle is moving around?

TurboTR

 

[John Snyder]

This is the first time I have tried this board, I want to thank you guys for your suggestions, I probably need to try making my "path" of cells that I adjust wider. The A/F seems to wander regardless of rpm or kpa, I only notice it at WOT though, the car seemed a little sluggish and this is the only thing I can figure that is causing it. I have not seen any other data logs with a felpro so I think you answered my first question...is this normal?.. I am guessing it is not.

Thanks for the help.....

 

[bobc455]

Have you adjusted your VE tables?

It sounds like all you need to do is record a run, overlay the playback on the VE table, and make some adjustments. Two or three iterations and you should be within about 5-6% O2 correction.

As you're probably aware, the VE table is what the ECU uses to figure out how much fuel to inject so that it can hit your target A/F ratio. If the target A/F does not equal actual A/F, then chances are your VE (volumetric efficiency) numbers are probably a bit off. If your VE numbers are not accurate, then the ECU won't be able to make your actual A/F = your target A/F. Play with the VE table until your actual A/F = your target A/F.

-Bob Cunningham
bobc@gnttype.org