A/F mixture question
Thread Starter
Burning Brakes
Joined: Feb 2006
Posts: 1,223
Likes: 4
From: Regina Saskatchewan
A/F mixture question
I've recently bought an AEM a/f gauge . Carb was running rich at 11.3
With a little tuning the carb runs about 13.5 to 14.0
I understand I can hurt the engine by running it to lean , but how much is that. Perfect is 14.7
Will I damage things at 15.0 ? Or can I continue to lean things out until the engine pings , and then richen it up? I read somewhere that optimum fuel mileage can be found at 15.4 If it doesn't ping there will I be fine?
With a little tuning the carb runs about 13.5 to 14.0
I understand I can hurt the engine by running it to lean , but how much is that. Perfect is 14.7
Will I damage things at 15.0 ? Or can I continue to lean things out until the engine pings , and then richen it up? I read somewhere that optimum fuel mileage can be found at 15.4 If it doesn't ping there will I be fine?
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
Running lean at cruise will not damage anything. There's not enough going on in the engine to develop the heat to burn a valve or piston. If you go too lean at cruise you'll notice a misfire or surging. Some engines will cruise happily at 16:1. Typically your cruise ends up somewhere between 14-15 (depending on cam, intake etc).
Trick is to lean cruise out to whatever is optimal for your engine without leaning WOT. At WOT you need to keep it in the mid-12s.
Trick is to lean cruise out to whatever is optimal for your engine without leaning WOT. At WOT you need to keep it in the mid-12s.
