The Barst

What is a safe a/f for street driven 93 octane turbo cars? is 12:1 too lean on the daily? What are people running? Is that tuned with knock sensor, egt, or just a wideband?

Also if somebody tuned on the dyno safely and then later turned up the boost, would it lean out more or would the ecu accomodate for the extra airflow?

I know that just throwing on a high flow filter (on my car) will lean it out, but I don't understand why if the maf reads more air the ecu doesn't add fuel. Is it because the maps stay constant at WOT?

Greaser

how do you know that throwing an air filter on it leans it out. dont rely upon other users and internet information. test it out yourself on the dyno with a wideband.

i tune to 12:1 at redline on the pump gas maps. 12:1 is lean for a factory released vehicle. leave it where its at. usually they are 12:1 for the first 10-20 seconds of WOT then richen to 11 or 10:1 for piston cooling.

The Barst

I took the filter element out and left the top of the airbox off and the car ran .3 leaner. I'm thinking that since I didn't reset the ecu, before the pull, that the ecu didn't have time to adjust to extra air.

My real question is if the ecu will adjust for the extra boost if I turn it up a bit, or will it run leaner.

Stock, the evo's a/f runs so rich it's off the scale by 5-6k rpm. I was just wondering if I ever did lean it out a bit what most people run on the street.

Greaser

you had it running on a wideband when you did that?

being a MAFS controlled fuel system, if raising the boost does increase the airflow through the motor it should add fuel. but if raising the boost doesnt increase the airflow no additional enrichment should occur. But theres no way we can know. you have to look at the ECU and its maps to find the answer to your questions.

i usually run 12:1 at redline and 13:1 to 13.5:1 at torque peak. but i wont do any high speed runs because of the way i have it tuned.

Josepi

11.5->12.0 full boost. Cruise ~13.0. Idle ~13.5.

EGTs and narrow band O2 tuning is playing with fire...both don't react fast enough to see what's going on. WBO2 is the way to go.

Typically speaking most ECUs will handle higher boost levels than stock. Some ECUs (stock) will have some form of limit in the form of a fuel/ignition cut when a certain level of pressure is met.

Since I don't know the limitations of your ECU, I can't say.

If you plan on dumping some cash into the car, spend the money now on a nice EMS. You'll only thank yourself down the road (you can spend just as much money into band-aid fixes).

Greaser

Theres no reason to run 13:1 at cruise and 13.5:1 at idle. its a waste of gas and additional emissions.

cruise and idle; personally i run in the 14.7-15 range.

The Barst

Yep, it was on an AWD dynojet at the time. Like I said, I'm betting that the ecu just didn't react quick enough to the removal of the air filter. I wish there was a AWD dyno locally, so I could do some more tuning.

cruise and idle? what's that? Haha this car gets 6mpg on the track....not much better around town cause I can't stay outa the boost.....itsa drug...but you guys know that! I have no idea what the a/f is when cruising. Not gonna waste my dyno dollars on that.

Greaser

get a autometer guage for around town diagnostics. narrow band 02's with this gauge are perfectly fine for monitoring a/f's.

dont let anyone tell you that you need a wideband all the time. only when you sway away from 14.7:1 do you need a wideband. and 14.7:1 is where you should be at for almost all engine running conditions from idle to about 5psi boost (on a low compression high boost setup like a EVO)

The Barst

Thanks, that is good info.....I guess I just always hear people say negative things about narrow bands and never really thought about them beyond being useless for WOT tuning purposes. What you said completely makes sense to me though.

MKNTRAXX

For a daily driven car I would like to see my WOT around 11.5.. 11.7 at the max.. Because unless you have a wideband how often are you going to dyno tune the car. And i like to have room for any kind of mistake that could happen with the ecu or air metering stytem. and i always rather like to be safe than sorry.. thats just me though..