On the dyno the other week, at cruise my 88 turbo had a mix of 14.8, then progressed in linear fashion to about 13.1, at full throttle with plenty of revs. Would this be normal, or lean? It sounds like most of you guys think 12 is a good mix at full throttle...

Charlie

 

13.1 is way to lean under boost / WOT!! should be around 11.7-11.9

14.7 is normal for cruise

 

hmmm even for a stocker hey...
anybody got any suggestions for what I should check? The car appears to run perfectly in it's current form...

Charlie

 

come on folks... any useful input??

Charlie

 

The first time I dynoed my car, I just about **** myself when I saw the AFRs - they were just about the same as yours - they looked WAY lean until about 4000 RPM. Then I remembered that I both had cats, and was using a tailpipe sniffer wideband O2 sensor.

In short, yours sound just about right.

Brandon

 

Got an AFR number for idle?


-Ted

 

hm don't remember exactly. certainly wasn't richer than 14.8, but am pretty certain it wasn't much leaner either. between 14.8 and low 15's I'd say. I wanted the place to give me one of them afr graphs, but they couldn't do it, so I just sat in the car and watched the screen...

Charlie

 

AFR at idle on my turbo is 13.4. Adjustable with the variable resistor, but 13.4 is where its happiest at.

At full throttle, I see low to mid elevens. Nothing special about the fuel system. Just a half hearted fuel pump resistor rewire. See 14.6's at cruising. Sensor is a wideband located about a inch below the stock 02 sensor. OZ sensor/wideband.

 

I never ran my car with a wideband and the stock ECu, I didn't have the wideband 02 till I got my haltech, but I did run with an autometer a/f guage with the stock ecu, and still run the autometer as a closed loop indicator with the haltech along with the wideband, I know where the stock ecu ran on the autometer so I can pretty much say where it would have run by comparing what the wideband says now for an a/f ratio and what the autometer is saying.
By memory , an S4 TII with stock injectors, tid mod, downpipe, FCD, and no air pump, on a relatively ok motor with a psuedo streetport, and 3mm seals ran like this.
idle would be about 12.5-13:1
cruise would have been 14.0:1, I have tuned it for a deeper switch over into lean, to achieve a 14.7:1 on the wideband, I achieve 30 mpg highway, far better than I ever got on the stock ecu.
I was running around 10 psi of boost on the stock ecu, it sat down about 3-4 bars into the green on the autometer on boost which now equates to about 12.2-12.5:1 on the wideband, not horribly rich by any stretch of the imagination. the autometer is completly pegged rich at 12:1....
I really wish I had someway of knowing what the stock ecu did with the ignition, it would make tuning the haltech a bit less of hair whitening chore...Max