A/F Ratio

[VVT-i Owns]

What is a good ratio that tuners aim for in a NA setup?

[zoni]

you should always aim for 14.7:1

thats desired in most cases. only in some cases people tune the engine to be lean or rich... if the engine can handle it and it will help them in some way...

[alltrac165]

^that there is the chemical ideal stochiometric(sp?).
Best power at wot will be richer, as in lower number like around 12 or 13:1 and best cruise will be a bit leaner, generally around 15.5:1 or 16:1 I think.

[VVT-i Owns]

Ya I thought it was around 15:1 from auto shop back in highschool.

Why I am asking is because I am looking at some Dynos for Mazda 3s and the guys says hes running lean....???????????

A/F is like less than 11:1.

[zoni]

ouch... someone needs to run fuel management and bigger injectors...

[VVT-i Owns]

bigger injectors?

THe car that Dynoed that has a CAI, thats it. The rest is stock.

DOn't you think that number is too rich?

[88 LE]

^ 11:1 is rich.

Hell thats even rich for a boosted car.

[gcs118]

For some reason Mazdas, at least the Protege, and its successor the Mazda3, run rich. I drive a Mazda Protege and it's widely known the system runs pretty rich from the factory. It's gotta be some Mazda way of thinking, perhaps too rich is safer than too lean? I dunno...

[silverstreakin]

too rich is just as bad as too lean. ive seen many a car have gas washed cyls. perfect way to ruin a block

[gcs118]

Originally posted by silverstreakin
too rich is just as bad as too lean. ive seen many a car have gas washed cyls. perfect way to ruin a block

Too lean may result in hot spots, detonation, etc., or even melting, right? What does too rich lead to? I have not heard of gas washed cylinder walls before.

[88 LE]

Originally posted by gcs118
Too lean may result in hot spots, detonation, etc., or even melting, right?

Yup.

What does too rich lead to?

Fouled plugs, bad fuel economy, etc..

I have not heard of gas washed cylinder walls before.

The cylinder walls get lubricated by oil. If theres to much fuel in the cylinder, the fuel washes away the oil.

[VVT-i Owns]

Haha, I knew that number was rich, that dude didn't know what he was talking about.

It may run rich but I average 7.4L/100KM or about a good 34 MPG

[K2e2vin]

you should try to get it as lean as you can without detonation and stuff...like 15.* might wanna go richer if you have higher compression pistons.

[sv21 wagon]

fuel washed cylinder walls are real, more ring bore and skirt wear, bad thing, also rich mixture causes cat con to run very hot and may melt internals blocking exhaust. O2 sensor should keep mixture around 14.5:1 (+/- 0.5:1)

[Marvelicious]

Buy and read this book:
http://www.buy.com/retail/product.as...ok&dcaid=17379

Optimum power is at 12.6:1 Rich
Optimum fuel efficiency is at 15.4:1 Lean
Best compromise is stoichiometric 14.7:1