Running Lean, will I hurt numbers by fattening my A/F out?

Blakers01GT

Master of the Clubhead
Founding Member
Sep 21, 2001
2,110
0
0
Brown Deer, WI
I am running 11:1 on real low rpms, once it gets to 2k and up, my A/F jumps to 14:1 - 14.5:1 and then once the rpms gets to 5k, it jumps to 15 and rises to 15.5.... NOT GOOD!, and NOT SAFE, especially at high rpms! shouldn't it rich out a little at high rpm's? is my lean condition hurting numbers, or helping? so if I get my A/F down to 12.5:1 or something ,will that hurt my numbers and become safer or help my numbers because it will bring some more fuel then air?

by the way, dyno numbers are 257.8 RWHP, 301.8 RWTQ...
 
  • Sponsors (?)


Blk03GT said:
Thats about right, your NA correct. You should be around 14.1 or so.

12.5 is if your running a power adder.

huh? I disagree, 12.5 is too lean for a blown application, you wanna be 11.5-12 at the leanest. I just talked to tim, he's gonna fatten it out for me, he said it was way too lean.

but my question is, am I gonna lose some power going down to about 12.5-13?'
 
11:1 on Power Adder in the RPM's, and 12.5:1 at idle should be fine.....


But also, if you're N/A, then you're A/F doesn't look that bad IMO. IF the car runs fine, dont worry w/ it...

If you throw more gas at it, you're gonna lose a couple ponies, b/c when you're N/A, LEAN IS MEAN

-Will
 
TARZAN said:
11:1 on Power Adder in the RPM's, and 12.5:1 at idle should be fine.....


But also, if you're N/A, then you're A/F doesn't look that bad IMO. IF the car runs fine, dont worry w/ it...

If you throw more gas at it, you're gonna lose a couple ponies, b/c when you're N/A, LEAN IS MEAN

-Will


I hear ya, Will. But what worries me is when I get to about 5krpms, my A/F jumps to 15:1, then 15.3:1 at about 5800 rpms, thats when you start flirting with disaster, wouldn't you agree?
 
lean

Bro your not lean for a NA car.

Your number are fine; even the 15.5.

Your times are better with a lean condition.

Yes 12.2 is to lean for a blown or sprayed car. The extra fuel is used to keep the cylinder temps down because it difficult to retard the timimg.
 
I had my a/f tuned to a 13.0ish:1 ratio because it was running like 11:1 before the tune. The tweaks to my a/f and engine timing netted some small gains across the entire two curves. This was all done on a dyno of course.

My tuners did not want to push my a/f up any higher than the low 13's for fear of my engine pinging. We did do one dyno pull with a slightly leaner mixture and my car did produce slightly better gains. However, for fear that my car would ping on hot summer days, we backed it down a bit. I was happy with 250 rwhp./292 rwtq. SAE corrected in the end.

For the comment regarding tuning at idle, I have never heard of that. My understanding is that all tuning is done at WOT. The car attempts to maintain a 14.7:1 ratio at idle and part-throttle (i.e. normal driving). I believe it's also referred to closed loop mode. At WOT, the car goes into open loop and uses the fuel mapping your tuner programed into your chip or computer if you had a reflash.
 
2000GT said:
For the comment regarding tuning at idle, I have never heard of that. My understanding is that all tuning is done at WOT. The car attempts to maintain a 14.7:1 ratio at idle and part-throttle (i.e. normal driving). I believe it's also referred to closed loop mode. At WOT, the car goes into open loop and uses the fuel mapping your tuner programed into your chip or computer if you had a reflash.
I was referring to the 14.1 AF at high rpms not tuning.

On these cars NA staying around 12.5-13.0 all the way to redline will build you the most power if you are FI keeping it 11.5 or richer may not get the most power but it is safer. If you do nothing to the timing you can get away with a lean mix but the first hot summer day you will get some detonation. With a richer mix you can get some more timing in it up top.
When I had mine tuned we tried just about everything and settled on a 12.9 and bumped the timing. I left with 241.5 hp and 283 tq from 228hp and 277tq. The biggest difference was from 5200 to 6000 the curves flattened and I gained 20hp and 20tq at 6000.

BTW I have a headswapped 97GT
 
billyfe390 said:
I was referring to the 14.1 AF at high rpms not tuning.

On these cars NA staying around 12.5-13.0 all the way to redline will build you the most power if you are FI keeping it 11.5 or richer may not get the most power but it is safer. If you do nothing to the timing you can get away with a lean mix but the first hot summer day you will get some detonation. With a richer mix you can get some more timing in it up top.
When I had mine tuned we tried just about everything and settled on a 12.9 and bumped the timing. I left with 241.5 hp and 283 tq from 228hp and 277tq. The biggest difference was from 5200 to 6000 the curves flattened and I gained 20hp and 20tq at 6000.

BTW I have a headswapped 97GT

I thought you might have meant that, but I just wanted to clarify for the original post.

I also noticed the largest gains to be after 5000 rpms. on my graphs. Big difference. My peak gains only went from 241 to 250 rwhp. and 285 - 292 rwtq.

Chips are awesome. Not only did my car gain power, but I also saved money by not having to purchase MIL eliminators or a Speedcal. We also programed my engine fan to turn on 5 degrees earlier. You can fiddle with just about anything depending on the software your tuner has.
 
2000GT said:
I thought you might have meant that, but I just wanted to clarify for the original post.

I also noticed the largest gains to be after 5000 rpms. on my graphs. Big difference. My peak gains only went from 241 to 250 rwhp. and 285 - 292 rwtq.

Chips are awesome. Not only did my car gain power, but I also saved money by not having to purchase MIL eliminators or a Speedcal. We also programed my engine fan to turn on 5 degrees earlier. You can fiddle with just about anything depending on the software your tuner has.

I made out like a theif on mine.
Diablo revolutions chip $0
95 dyno runs $0
He had done chevy's for years but just got into fords so my car became a test mule for him and the dyno. I had my fan turned on at 180 low and 190 high god what a difference that made.
 
Blakers01GT said:
huh? I disagree, 12.5 is too lean for a blown application, you wanna be 11.5-12 at the leanest. I just talked to tim, he's gonna fatten it out for me, he said it was way too lean.

but my question is, am I gonna lose some power going down to about 12.5-13?'

Well it doesn't say your blown in your sig. And if you are then your numbers are incorrect. :rolleyes: