What is the highest anybody's seen on a naturally aspirated engine, meanning the leanest?

Shawn

 

The Honda Insight lean-burn engine operates at about 22:1 at low loads.

Or do you mean what's the leanest A/F ratio anyone has seen at peak torque/power with a NA LT1?

 

Yeah sorry I meant NA LT1.
Anybody?

 

Nothing sticks in my mind as far as n/a, but i've seen a blown LT1 survive at 18:1 on a dyno

 

18:1

 

My buddy is claiming 20:1 . I say And he's been driving it it.

 

sounds like a recipe for toasty valves and torched pistons.

 

Most people these days are tuning for right around 13 to 1. I just spent the whole afternoon on the dyno and frankly there wasn't a lot of difference in power on anything from 12.9 to 1 up to 13.5 to 1. Ended up in the 12.9 to 13.3 area.

Of course the air quality today in Dallas sucked and I stopped tuning because the car was down 10lbs of torque from normal. Red Ozone alert and 105 degree temps in the dyno room made it easy go go home early.

The jest is going no leaner isn't going to help make more power. Dutwiller (sp) gave a presentation at the SAE meeting a couple of years ago and said 12.8 to 1 was best for making max power. This is a little controversial.

 

Yeah I would think my buddy would be losing a ton of power running that lean. But I just didn't think it was possible to run that lean and not have melt down right away. Anybody have one melt down cause of a lean condition.

 

Anybody seen anything that crazy?

 

There was an article here a while back.... was a 455 powered Pontiac Firebird built by Norm Brandes (Westech) called The Historian. I think they called themselves the "Clean Team Project" or something like that. The goal was to run 11's in the quarter mile and pass the IM240 emissions test for later model cars (this was ~90'-92) using dual cats, no air pump.... it'd fail the visual. Static compression was pretty darned high at over 12:1 (don't remember exactly) but it sported a pretty good sized solid roller cam.

To make a long story short, the car passed all the requirements with flying colors running high 11's. The A/F tune was somewhere in the 17:1 range from what I remember and it went from the track (hood sealed) to the dyno with no tuning adjustments once there! Now that was on old Pontiac Ram-air castings. Pretty amazing stuff. Not to mention, the car was "very responsive and drivable".

I'll try to dig up the article if anyone wants specifics.

-Mindgame

 

can you dig that article up if you have it mg?
sounds like it'd be an interesting read