[nonsensez9]

Can someone explain to me the benefits and drawbacks of running a lean fuel mixture vs. a rich fuel mixture. thanks

[tw0scoops123]

Lean vs rich? The V-8 runs on 87 octance(regular). You shouldn't run it on anytihng else cuz that is what it is made for. On occasion you can run some high octane, but I wouldn't do that on a weekly basis. Not good for the engine.

[kj_cinci]

Originally Posted by nonsensez9

Can someone explain to me the benefits and drawbacks of running a lean fuel mixture vs. a rich fuel mixture. thanks

Well, you should try to have it PERFECT, not rich nor lean. Hence a professional tune (where they analyse your exhaust etc.)

Higher octane gives some more forgivness regarding the mixture and add some throttle reponse if you tune for it.

Lean might (will?) result in engine damage in the long run as the fuel helps to lube and cool your engine (cylinders and valves). You do have a alu block and the one (lonely) exhaust valve gets it pretty hot as it is!

Rich will waste fuel, make your engine sluggish and in the long run leave residue on valves, sparkplugs etc. reducing effectivness and might lead to repairs (not as expensive ones as running it lean though)...

My .02 Euro Cents, now you gear-heads shoot me down...

[xxp]

Ok, I'm not a gasoline expert, but I gotta ask: What does octane have to do with a/f ratio on an EFI motor? It's my understanding that higher octanes only provided a higher burn temperature on a fuel injected motor.

Running too rich a mixture will mean that all the fuel won't burn during detonation leaving power in the cylinder. Too lean and your engine runs hot, and can cause damage to the internals (pistons) and also leaves power in the cylinder.

To completely burn gas, you need a mixture of 14.7:1. Search for Stoichiometry on Google.

Again, not an expert here, but I think the only time you would want to increase octane is if you had a higher compression ratio, somewhere near 10.5:1, or if you start fiddling with timing. The ECU modifies your a/f ratio.

My $0.02 -- And you get what you pay for

[green91]

actually, running a little on the lean side is more correct for a gas motor. (and anyways, perfect stoichiometric is very hard to accomplish) but when it runs a little lean it will run hot which will reduce NOX gases (oxides of nitrogen)(only a very lean condition will cause detonation and cause internal engine failure) which reduce emissions. and while running a little lean helps make sure most of the hydocarbons get burned in the combustion, reducing emissions. and yes XXP is correct about the octane rating, it has nothing to do with running rich or lean.

[xxp]

I know the ECU is constantly modifying a/f mixture around stoichiometric, and wouldn't argue that running a bit lean is better for emissions....but....and I'm just taking a poke at this, I bet it gets pretty rich at WOT. You gain power by richening the mixture to a point...13.5, 12.7, somewhere in there. My only point about a stoichiometric mixture is that's where you completely burn a gasoline/air mixture.

[nonsensez9]

so the ECU is monitoring the a/f mix... why is a tune necessary for a CAI? Someone had mentioned that the ECU has top and bottom limits on how much air flow it will recognize, and thus the amount of fuel it will deliver. sounds kinda odd as Ford must know that one of the first products of aftermarket is CAI. Hard to imagine them not taking that into consideration.

But I digress.... I'd really like to know exactly what the tune is doing. Is it something as simple as removing the upper/lower limits? is it altering the a/f mixture that Ford supplied? altering the ignition timing? so many things that it could be doing to gain the extra hp I wonder if the CAI is actually doing anything.

there's additional parameters I'd like to mess with, too. namely the slow throttle response.

[xxp]

The more air you flow, the more fuel you can add which means the more power you can make. And, the cooler the air the better. I have some ideas on what the tune does, but nothing firm, so I'd prefer not to speculate, but it's more than just mixture. It handles fuel and timing curves.