Hey, folks! We continue to make progress with the Jetta. The next time we go out we will have 13" wheels with the locked diff tranny. The last time out we were competitive, so we really feel like we are going to have "something" for folks one of these days. Things are certainly getting "fun."

As readers of this forum know, we have bypassed the knock box/O2 sensor so that we control the A/F ratio. We are also using the Autotech fuel module to enrich the fuel at WOT. This all seems to be working fine. We set the A/F mixture using the 3mm adjustment by the fuel distributor. We monitor the A/F mixture with a nice digital wideband sensor. But, it's not working perfectly. Here is how it goes . . .

During testing or qualifying we set the A/F ratio at idle in the paddock/pits. We usually set it at about 11.3/1. Then we watch the A/F ratio on the track. If we find the A/F ratio is where we want it at WOT (about 12.5/1) then we are happy and leave it alone. If not, we continue to adjust the A/F mixture with the 3mm adjustment in the pits until we have what we want on the track. The problem is, over the course of the weekend as temperature and humidity change, the A/F ratio changes. So, we can have things exactly where we want them during qualifying in the morning, then go out in the heat of the afternoon and everything is out of whack again. And, to complicate things, the starting point varies depending on the conditions. We can't always start at 11.3 because sometimes you end up where you want at WOT, sometimes you don't. I should mention that the variance is what one would likely expect as conditions change, so we do think that everything is working fine. We just want to have this stuff REALLY under control.

So, we know that some of you control your A/F mixture from inside the car with a potentiometer. This seems different to us than enrichening the fuel at WOT.

The schematics that we find seem to be for fuel enrichment, not for controlling the A/F ratio.

So, is enrichment different than controlling the A/F ratio?

If so, how do you control the A/F with a potentiometer from within the car?

Is there a schematic or some instructions for how to set this up?

As always, thanks!!