Lean Engine damage
- Thread starter dvernst
- Start date
3.8TransAM
Member
- Joined
- Apr 8, 2004
Verify it with a wideband or your wasting your time.
The stock 02 at best could be used to note trends, but if your trying to tune by it or take it at its word, especially at WOT your grasping at straws.
Myself and many others have datalogged runs on many GM single wire sensors and they could be at 800 or 0 while the wideband reads 12 or richer.
later
Jeremy
The stock 02 at best could be used to note trends, but if your trying to tune by it or take it at its word, especially at WOT your grasping at straws.
Myself and many others have datalogged runs on many GM single wire sensors and they could be at 800 or 0 while the wideband reads 12 or richer.
later
Jeremy
I agree, you'd have to verify what the actual afr is before you know weather your really lean or not. Not all cars or 02's respond the same at WOT.
As for possible damage, running lean means running hot and from personal experience can crack the heads over time, or real quick if you detonate it. One of my heads is in the machine shop for this reason cause my fuel pump took a dump, ran lean and detonated around 1000ft. I lifted quick(under .5 seconds on directscan)but #3 has been showing water scince then.
HTH,
Steve
As for possible damage, running lean means running hot and from personal experience can crack the heads over time, or real quick if you detonate it. One of my heads is in the machine shop for this reason cause my fuel pump took a dump, ran lean and detonated around 1000ft. I lifted quick(under .5 seconds on directscan)but #3 has been showing water scince then.
HTH,
Steve
Having pulled my hair out on this one this might help you. I agree you really need to go to wideband O2 to be accurate. After that, minimum burn time is a mixture around 12.5-13.0, which is why you get max power at this AFR. Above or below that burns slower, regardless of AFR. When you are outside the fast burn AFR's and you think you can run more timing and it detonates, most people add more fuel which is not the problem (still burns slower but cools the mixture). Max cylinder pressure is happening too quickly due to too much timing (talk about damage...). Adding boost speeds up the burn also so the game you must play is this. Dial in the AFR you wish (which is why you need the wideband) and then find max timing (for most burn time) that you can get away with per load. The sweet spot I have found to be around 23 degrees for 12 lbs. at approx. 12.6-12.8 AFR. This makes a huge amount of power. Then, take more timing out under more load and add back in for more RPM's.
89 TTA #162, 38K miles. Built motor (3k miles), frame connectors, 70mm TB, twin pumps, 3" DP with Aero-turbine, massive intercooler, 3.42 rear, non-lock art carr tc, FAST B2B wide band O2, 75 lb. injectors, T67, RJC power plate... **RIPNAIR PROJECT - 10 second car that gets 30 MPG on the road**
89 TTA #162, 38K miles. Built motor (3k miles), frame connectors, 70mm TB, twin pumps, 3" DP with Aero-turbine, massive intercooler, 3.42 rear, non-lock art carr tc, FAST B2B wide band O2, 75 lb. injectors, T67, RJC power plate... **RIPNAIR PROJECT - 10 second car that gets 30 MPG on the road**
Tune to 12.6-12.8 on a turbo buick engine and you will burn a huge hole through it. Nobody tunes that lean. Its a forced induction motor.. not an NA motor. Huge difference.
11.0 is the target on most racing Buick engines. Leanest is 11.5.
I dunno bout leanest being 11.5, I know alot of guys that target afr as high as 11.9:1
My typical target afr is 11.7 when bracket racing, a little leaner when going for a number(11.9-12.0). No knock and the motor has been together for 6 years, 30K miles, and 600+ passes still going strong, except for that fuel pump problem I mentioned before which lead to a cracked head
That woulda happened regardless of my target afr though.Things go wrong and not all cars act the same so I dont belive there is a hard and fast rule about air fuel ratios
Similar threads
