Pontiac GTO Forum banner
1 - 11 of 11 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter · #1 · (Edited)
Finally got my GTO dynod for the first time. It is completely stock except for the Lingenfelter CAI. I also went with a friend of mine who had an auto 06 that was totally stock. My best numbers were 342.8 rwhp and 373.9 ft/lbs. His best at the time was 329 rwhp and 350 ft/lbs. SAE corrected. Both of our air fuel ratios are of course too rich, looking at my graph, mine dips almost to 9 which is extremely rich. The dyno guy said we should be running in the high 12's, like 12.8, and that we should pick up almost 20-30 rwhp by adjusting the air fuel ratio. Does this sound reasonable? We are both getting our cars tuned next week, so hopefully we can get some more power to the wheels!!!!
 

·
Registered
Joined
·
456 Posts
03xtreme said:
LEAN is faster than richer until you get detonation etc.

I'm not sure I understand... Lean is faster - Until you get detonation (and then richer is faster?)

Did I read that right or am I being a nob :confused
 

·
Registered
Joined
·
98 Posts
When you lean out, the cylinder temp goes up and you get a bigger explosion. the problem is that when the temp gets too high, the available air/fuel mix ignited before it is supposed to (spark plug igniting) and the car detonates. Very bad.
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #5 · (Edited)
jacobyb said:
When you lean out, the cylinder temp goes up and you get a bigger explosion. the problem is that when the temp gets too high, the available air/fuel mix ignited before it is supposed to (spark plug igniting) and the car detonates. Very bad.
Shouldnt the proper air/fuel ratio be about 12.8?? Both of our air fuel ratios looks like the ENRON stock charts. They are up and down all over the place instead of a steady line. We pulled up my 02 WS6 dyno run while we were there and notice it had a nice steady line about 12.8. I was down in the 9's which the guy responded that he had never seen a fuel injected car running like that. I will post pics of the sheet when I get an email from the guy with my results.

The guy I dynod with said one of the guys he knows had his LS2 caddy dynod and had the same problem until they tuned it, now he's running just shy of 13. Any thoughts???
 

·
Registered
Joined
·
456 Posts
jimmysws6 said:
.... had his LS2 caddy dynod and had the same problem until they tuned it, now he's running just shy of 13. Any thoughts???

Ya. I think I'm gonna get dyno'd :D
 

·
Registered
Joined
·
40 Posts
13.0 if it'll do it with out knocking.....

if you can advance the timing enough and run it hot enough with out getting detonation you will get better numbers, but you are playing with fire so to speak. and the wives tale about lower T-Stats like a 160 tstat is a hoax if you didn't already know that. the obdII can practically learn out everything you do to it unless you hack closed loop, i don't know anybody who can do that so we end up tuning WOT which is only affective at WOT.... so you fix that with piggy back modules to over ride the ecu and put a wide band O2 sensor/s on to control A/F ratios with a laptop.

You don't want to go crazy adjusting timing and a/f because it will change the combustion rate in the chamber and possibly do some crazy stuff like detonate or burn faster or slower than the original design of the chamber then you have to deal with spark plug temps, etc.

in reality the a/f ratio should go from "lean" to "rich" and bounce back and forth, i don't know what GM set the oem ECU to accept as lean or rich. You could get that by averaging all of the O2 readings from a scanner or asking somebody here or from GM. I'm not sure of that number but 12.8-13.1 some reason 13.1 sounds familiar?
 

·
Registered
Joined
·
40 Posts
a lot of guys seem to run an O2 simulator, jack up the A/F ratio to rich all the time don't get the ses because the O2 sims gives the ecu a false reading.

edit: then run it rich for protection and safety

the thing to do really is have 2 ecu's. One that is a total hack performance ECU running custom A/F maps and timing maps etc and then have an OEM plug and play.
 

·
Registered
Joined
·
95 Posts
jimmysws6 said:
Finally got my GTO dynod for the first time. It is completely stock except for the Lingenfelter CAI. I also went with a friend of mine who had an auto 06 that was totally stock. My best numbers were 342.8 rwhp and 373.9 ft/lbs. His best at the time was 329 rwhp and 350 ft/lbs. SAE corrected. Both of our air fuel ratios are of course too rich, looking at my graph, mine dips almost to 9 which is extremely rich. The dyno guy said we should be running in the high 12's, like 12.8, and that we should pick up almost 20-30 rwhp by adjusting the air fuel ratio. Does this sound reasonable? We are both getting our cars tuned next week, so hopefully we can get some more power to the wheels!!!!
I tend to keep my cars at the safe a/f ratios are 12.5-12.8 provided there is no knocking. The optimal is higher 13.2-13.5 but I set mine lower because I have little control over the gas that goes into my car. So your dyno guy is right that ~12.8 should work and still be save from knocking or if you get bad gas. In your case, I am skeptical about the 9's a/f ratio by your dyno guy. The richest an LS2 runs is normally commanded stock is at 10.9 about ~4000 RPM. Even if you were running into converter overtemp protection that richens a/f to cool the cats, I do not believe the a/f ratio goes that low to show 9's. I'd have him check his readings because if his meter is off and he sets it at 12.8, you may be at 13.8 or higher and causing problems.
 

·
Registered
Joined
·
71 Posts
This is some seriously good info fellas. I was thinking about installing an exhaust and CAI system but I think I'm just going to leave my car bone stock because it seems like I will just be causing more problems than anything.
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top