A/F reads 15.96 all the time?


New Member
I am working on tuning my SpeedPro, and for some reason it keeps a reading of 15.96 or so... The target A/F is 14.7 I think, but it wont get there. Also, I keep loosing communications btwn the laptop and the ECU and at that time, the RPMs go up and back down again. Man, this is just confusing the hell outta me.

Regarding WBO2: Is the ECU recognizing the O2 sensor? Does the little lambda symbol show up in the status bar at the upper left of screen (C-Com DOS) or lower right (C-Com WP)? Is the O2 heater working/getting hot?

Regarding communication problems: Are you using DOS or Windows C-Com? If using DOS C-Com, try making a boot disk and booting from it then running C-Com. Make sure that serial port related features are turned off in the CMOS setup too. Things like Infrared, wake on serial interrupt, auto port power-down, etc. can cause problems with some laptops. Some of the same things apply to windows C-Com too. Make sure there are no serial port interrupt conflicts also.
I'm assuming ya upped the ve #'s to get the a/f readings down? I believe 15.96 is the leanest the O2 will read. Is this 14.7 target a/f for a sc'd 408? I hope not :) I don't know about the rpm deal, but the only time I've lost signal is when I kinked the cable between the ecu and laptop and had to remake the connections inside. Good luck.
yes, the 14.7 is for a supercharged 408 AT idle, definatly not under load. The sensor is not doing that anymore, looks like the laptop I was using had some software problems actualy. Right now, I havent even gotten to the point where I can drive on the Speed Pro, just starting my tuning.

Don't think...

Don't think 14.7 is a good A/F for idle. That's near mis-firing. You should be in the 12.5 to 13.0 range.
Hmm, thats just wierd... on the stock computer, it idles way leaner than 14.7 and it doesnt misfire at all, smooth as ice. But I am gonna try richening it up cus this felpro thing is VERRY different, probably since it is bank to bank and not sequntial like the stock setup was.

The stock system with a switching O2 sensor will probably try to idle the car near stoich a/f in closed loop, about 14.6:1 for gasoline. Remember there's likely a catalyst on the stock engine too and it has to be kept happy :)

FWIW I idle and cruise mine at 14.6:1 with the FAST ecu too, but not everyone gets good results there for whatever reasons. It's a pretty mild engine off the boost though. Some find that idling theirs a bit richer works best. Nobody I know tries to idle it leaner than stoich :)

From my experience

I've tried to idle my Supercharged SBC at leaner A/F's (14 to 14.5). The results were not good. I've since fattened it up to approx 12.8:1 and it smoothed things out quite abit. Alot of this depends greatly on camshaft design. Many larger duration cams will tend to put some of the extra fuel right into the exhaust during overlap. Turbo cams generally are milder and can take less fuel becuase of this. Again...every setup is different, and therfore requires its own settings. Good Luck