What's an acceptable air/fuel ratio for my T2? Here is what I boost: 7.35psi in 1st, 9.5 in second, 11.7 in 3rd, and 13.2 in 4th. That boost in 4th is pretty scary, and when I installed my air/fuel guage today I got a peak of 10.5 in 4th gear! In 3rd it was about 11.5, and below that it was around 12s. I'm just wondering what is considered lean, somewhat lean, somewhat rich, and rich, on the guage =). I have a feeling I'm leaning out alot, but it doesn't much matter b/c the car is going into storage... engine will be pulled and rebuilt, upgraded turbo... blah blah... thanks in advance for the replies

-Brian

 

If anything it looks like you are running too rich. The 10.5 you are getting in 4th gear is very rich. Your third gear A/F ratio is probably about where you want to aim for all gears to play it safe. Anything more than a 12.0 and you are starting to get a bit too lean for WOT. IMHO.

The other thing to remember is that unless the sensor is EUGO or something similar these numbers should only be used as a guide to what you are actually running because even if it is a wide band sensor it won't react quickly enough to give you a figure by which you can tune the car.

 

Thanks for your help. Kinda wierd that my fuel is running the opposite of what it should? You're saying it's running leaner in the gears I'm making less boost... why is that? My IC is most effiecient at high speeds anyways so it will be dumping a cooler intake charge as well. I'll do some more tests tonight. BTW, it's the greddy guage w/ 4-wire 02 sensor. Thanks,

-Brian

 

i would never tune a car by a greddy a/r gauge. You need a wide band O2 sensor. Or get a Motec A/R Meter.

 

Yes, that is what the O2 meter is saying! It is getting richer the more boost you run. I have no explanation for this without knowing more detais about the mods to your car.

As for the meter that you are using, I have heard that the Greddy O2 meters are pretty good and being a wide band O2 meter it should be giving you a fair indication of your actual A/F ratio. BUT, like enzo250 said, don't tune your car using it! This is because as far as I know, any 02 sensor other than the Autronic (EUGO) or the MoTeC sensor does not react fast enough to tune a car by.

 

LOL! My only "power" mods are a racing beat turbo-back w/fuel cut defenser. The racing beat exhaust comes with a 3.7" downpipe, and with a stock wastegate, no wonder I'm boosting so high. I just don't understand why I'd be leaning out when I'm boosting less.... hmm, I don't really care, as soon as I get the new clutch broken in, it's going in storage!

Appreciate your help!

-Brian

 

No worries Brian.

Looking at what you have done to your car I can't really think of a logical explanation for why you are running so rich with more boost. Maybe the stock computer is over compensating for the higher than stock boost levels?? Your guess is as good as mine.

 

what ecu are you running?
you should run richer as boost increasese especially with the stock turbo cause the intake temps go thru the roof as you go up the boost range and you need the extra fuel going in to work as a heat absorbing thing