I hear this a lot. Why is lean supposedly mean?

 

The ideal air/fuel mixture for the internal combustion engine is 14.7:1......14.7 parts of air for every 1 part of fuel. anytime the ratio is above 14.7, the mixture is considered "lean". below, is considered "rich"

 

You certainly don't want your engine to run lean. That would be "mean" to piston tops and valves, and possible aluminum heads. Lean mixture males for excessively hot combustion and tends to cause detonation. There's nothing better for holing out a piston than getting it really hot, then hitting it with a "gas hammer".

Beyond that, I'm not sure what it might mean in terms of a vehicle, other than taking out extra weight can make the car more responsive.

 

I agree with Vader! I also have heard that you want an A/F ratio around 12.5/1 for a supercharged engine or about 13.5/1 on a NA engine at wot. I think the term lean is mean also represents the desire of burning a chip so at WOT is with in these prameters. The stock chips give aprox 11/1 A/F ratio @ wot, get closer to 12.5\13.5/1 and more hp. I've heard it said on the prom board that it's cheaper for GM to replace spark plugs than engines

 

I've heard that but it always meant something else. example:

Light is right, lean is mean.

That is the phrase I remember.

 

I have heard the expression used when tuning cars. I think by lean it is meant to be as lean as possible without causing detonation. Assuming no detonation at the lean level a car will run quicker lean than it would with the same mods and circumstances at a 'richer' level. When tunign my GN the ideal O2 millivolts is around 780-790 I believe. Assuming no detonation at this level it will be quicker than if the O2 millivolts were reading say 830. If I am wrong I apologize but this is the way it was explained to me when I had my scantool installed. Hope it helps you out.

 

1987GN, That is what i was trying to say! You want to get as lean as possible; For a SC car 12.2-12.5/1 is theory max and NA 13.5/1

 

1987 GN hit the nail on the head as to what I was talking about. I've heard this term used by mechanics, all who are over 40 years old, and they were referring to air/fuel mixture. Is there any benefit to running a hotter combustion? I don't plan on running my Iroc any leaner than it already is. On my VW I've gained 75 degrees of cylinder head temp just by having a cylinder too lean.