BismoFunyuns

My car has ***** thumpr, long tube headers, catless x pipe and slp loudmouths. Cold air intake and 4.10 gears, (automatic)

I made 320rwhp/325rwtq @5700rpm on a mustang dyno.. My AFR sensor #2 says I'm at 14.0 on the max run, 13.0 average, and 12.5 minimum. I've read that 14.0 WOT is dangerously lean. I added 2% richer WOT A/F ratio, and increased the timing in all RPM ranges +2deg . I'm not sure if this will put me around where I need to be, I don't have money to put it on a dyno or buy anything to measure my a/f ratio with.

Any thoughts? I originally thought to leave the timing at 0deg, and just add 4% richer but I figured I'd get about the same results either way.

Any other opinions on this?

jpplaw

Since you have cams and a CAI, I assume you are tuned for those. Why are you playing with the tune? 320/325 is pretty good for the limited mods you have. Keep playing with the timing and your 320 rwhp will turn into 0 rwhp because of a hole in a piston.

Where did you get the "AFR" readings from?

BismoFunyuns

Yes I'm tuned for the stuff I have done.. The only reason I'm playing with tthe tune is because of the car running so lean, 14.0 is supposed to be very dangerous and 15.0 and above you're about guaranteed to blow up. The afr reading came from my most recent dyno sheet.

EDIT: I'm looking at my previous dyno sheet, and theres an afr sensor #1 and #2, apparently sensor #2 reads a lot more leaner than #1.

My dyno sheet with only headers/exhaust, afr #1 was 10.3 on max run, and #2 is 13.7 on max run. But the dyno sheet I got after the cams only showed sensor #2.

breathegood

I'm still not clear where you're getting your AFR information. Did the dyno op actually attach a wideband to your exhaust (if so, what kind and where? Was it properly calibrated? ), or are you relying on the lambda singnal from the factory sensors? They are not exactly the same thing. Who did your tune? Have you data logged and discussed it with them? I would start there before getting too crazy with adjusting timing and fuel myself with no wideband. It is important to understand where the data is coming from before making conclusions about the "apparent" results. Without a genuine wideband (which the factory sensors are not) measuring ahead of the catalytic converter, I would not put too much faith in any AFR readings posted on your dyno sheet.

Assuming the AFR results are good...The AFR is constantly changing. If you had experience with a wideband, you would see that even at idle where you would expect a constant 14.7, it will vary between ~14.2-15.0 (at least my car does), but it's always trying to get back to 14.7 while in closed loop. At the very beginning of a WOT pull, while making the transition from closed loop to open loop, it may very briefly spike lean, but very quickly richens up as soon as the open loop fuel/timing map takes over. You didn't specify the conditions under which you are seeing 14.0 AFR. Is it 14.0 throughout the pull, or does it gradually richen up as the rpm climbs? Was it in open loop or closed loop? What are your short term and long term fuel trims? These are questions you should answer BEFORE messing with a tune provided by a professional.

15.0 isn't a guaranteed anything, and 10.3 is richer than I would run even with FI.

Simon1

I didn't think 14.0 NA was bad at all. Just saying...

sactown

Seems a little lean to me, I would think it is safe to add a little fuel (2%), but I would not add any timing until you get the car back on the dyno.