how is lean fuel ratio good for FE ?

[Christ]

Originally Posted by basslover911

I am planning on doing this to my car sometime, and I will add a multi firing spark plug module (MSD) so that I can ensure that the flame completley burns.

Other than that, you have to be sure the air and fuel mix THOROUGHLY (aka homogeneous) otherwise you start developing knock.

No concerns here, other than there are two differing schools of thought (that I know of) on running super-lean.

One - Run two separate mixture profiles (see Honda CVCC engine) Basically, the idea is to run a very small rich mixture that will be easy to ignite, and the rest should be extremely lean, easy/quick to burn. When the two come in contact, you want the rich mixture close to the spark, and you want the flame front from the rich mixture to ignite the lean mixture.
This idea reminds me of Pulse and Glide driving... you're burning more gas in your pulse, but saving it because of long glides... thus saving overall.

Two - Multi-layered homogenous mixture, with richer portions on top, and leaner "layers" on bottom... normally created by means of "swirl" induction. Swirl induction requires that one intake event happens before the other in engines with 2 intake valves... in engines with only one intake valve, it requires some kind of flow restriction on one side of the valve (shrouding, etc.) to force the entire mixture in one direction, where centripetal force will cause it to swirl around the combustion chamber while it's being pulled in.

Those are the only two I know of, that will allow you to run super-lean (20:1 overall or better) and they're both iffy in most engines that haven't been worked over for the cause.

Originally Posted by cfg83

Christ -



Thanks. That agrees with something I read recently on saturnfans. A fellow was driving 90 MPH with 93 octane, and he burned a hole in his piston :

Picture of Hole in Piston

This is a response he got from a wise old Saturn Fan :

SaturnFans Forums - View Single Post - What would cause a hole in the piston?



CarloSW2

No Problem. And that guy is right... detonation causes piston slap, which wrecks the ring lands... ask turbo guys. (Piston slap is also caused by pistons which aren't hyper-eutectic being used in engines, when the engine isn't warmed up.. makes a metal on metal "slapping" noise.)

I could show you what running lean does to stuff OUTSIDE the engine too... if I can find the pic again, but I'll PM that to you, to keep this one on topic.

[basslover911]

Originally Posted by Christ

No concerns here, other than there are two differing schools of thought (that I know of) on running super-lean.

One - Run two separate mixture profiles (see Honda CVCC engine) Basically, the idea is to run a very small rich mixture that will be easy to ignite, and the rest should be extremely lean, easy/quick to burn. When the two come in contact, you want the rich mixture close to the spark, and you want the flame front from the rich mixture to ignite the lean mixture.
This idea reminds me of Pulse and Glide driving... you're burning more gas in your pulse, but saving it because of long glides... thus saving overall.

Two - Multi-layered homogenous mixture, with richer portions on top, and leaner "layers" on bottom... normally created by means of "swirl" induction. Swirl induction requires that one intake event happens before the other in engines with 2 intake valves... in engines with only one intake valve, it requires some kind of flow restriction on one side of the valve (shrouding, etc.) to force the entire mixture in one direction, where centripetal force will cause it to swirl around the combustion chamber while it's being pulled in.

Those are the only two I know of, that will allow you to run super-lean (20:1 overall or better) and they're both iffy in most engines that haven't been worked over for the cause.

OR

A homogeneous mixture of the fuel with the air WAY before it enters the combustion chamber so no swirling or any other fancy rich lean mixture thing has to occur.

I don't see how hard it can be, inject vaporized fuel into the intake tract before the throttle body (about 12 inches before) and with that distance it should mix thoroughly with the air. Simple and effective. Of course, return to normal MPFI for acceleration or spirited drives since it woun't have lag.