I have a 2001 Firebird WS6 Automatic
Mods:cam,LT headers,SLP MAF and Cold Air Intake.
Today i took the car back to the dyno to be sure about the AF ratio.
LAs time the guy told me that at full throttle it was 14.3. But when today we check, when the car is not at full throtlle the ratio is 12.3 but when i put the foot douwn to go full throttle the AF ratio just right to 14.3 but then it goes dow again to 12.1( cant tell you how much it last, but not to much, maybe a few secos or a range of 1000 rpm, like from 3000-3700).
IS THAT NORMAL, OR DO THA RATIO SHOULNT CHANGE NEVER?
rwhp350 rwtorq407

 

at full throttle or WOT ( Wide Open Throttle) your A/F ratio is 14.3 and the A/F ratio is 12.3 below that. tell the dyno operator to make your A/F ratio at 13.0 at WOT for maximum power (WOT or open loop is full throttle) and to tune the closed loop by tunning LTFT's and STFT's and VE tables(closed loop is part throttle) to get better gas milage.

 

Okay, but what i am saying is the at WOT the ratio jump to 14.3 but drop down rapidly, like if the car is adapting, that is normal?

 

do you mean when you press the gas pedal full throttle you get first 14.3 then when still at full throttle the A/F ratio drops to 12.3?

 

Sounds like the car is lean in the lower rpm's and a tad rich in the upper rpm's.. it needs more WOT tuning for sure.

You really want a steady ratio across the rpm band, generally speaking.

 

I second that.

 

Yes that is what i am saying, that when i push the pedal at 3000rpm aproximately, the ratio goes to 14.3 but still at WOT it goes down rapidly to 12.3
Just to know, okay the ideal AF ratio is 13, that is what will give you the more HP at dyno, but when you are cruising in the road the care does get a lot much air and tends to raise the AF ratio, or thats wrong? just to learn, Because at the dyno they only put a fan, but in the street, lets say, at 50mph a lot more air enters, since i have the hood scoops(ram air) and also the cold air intake piece that takes air from the bottom of the car.
What you think??
Just asking to learn

 

Other question. that raise in AF ratio spontaniesly can be cause by some bad MAF or leak on my intake system?
Like some air that is not measuring the sensor is pasing?

 

I don't quite understand ur last question but I can answer ur second to last. crusing a/f is 14.7. u do not need much fuel when ur foot is not on the pedal.

 

okay
But if you cruise at 14.7, then at that point you are loosing some hp or not?
So the point is not to optain the highest numbers in the dyno, because if you set up in the dyno, lets say at AF ratio of 13 ( there you have the highest hp on the dyno), BUT when you go to the street to race, the extra(more) air that your car will receive will raise the AF ratio,lets say to 14.7, so now you are not optaining the highes HP that the car can give, because that ratio is to lean and you will loose some HP. Am i right, just trying to use a lite logic to see these things. But remember i am new, just learning.

 

When i mention the AF ration #s i am always refering when you are at full throttle

 

crusing a/f and WOT (full throttle) are 2 totally different settings in the computer.

ur a/f will be set in the computer no matter how much air comes in the engine from the dyno or on the street.

 

okay, now i am undestanding, lot of thanks for that man.
So no matter how much air your car takes, if in the PCM you set that at WOT the AF ratio will be 13, it will remain that all the way, even if you are at 120mph and it is entering twice the air it normally enters.
Thats help me a lot

 

So right know if i am at 12.3 at WOT, my car is running a bit rich at WOT, right?

 

yes even if you are at 120 mph and at WOT (full throttle) the air fuel ratio will still be 13.0 if it was tuned to be 13.0 at all engine rpm's no matter how much air is entering the engine. air/fuel ratio of 13.0 mean for each 13 parts of air there is 1 part of fuel will be added to it to get that Air/fuel mix to burn in the combusion chamber. so it related to parts not how much air, for 13 big parts of air you get one big part of fuel, for 13 small parts of air you get 1 small part of fuel. that is what A/F ratio means.

 

okay, thanks for all your help guys
And another question.
WHy my car at the dyno marked 349rwhp and 407rwtq, and that was consistent. I think that is a big diference between hp and torq. My car is A4

 

maybe it is related to your current A/F ratio, i don't know maybe this is the reason. maybe once it is tuned well the hp/torque numbers will be closer to each other.

some one can chime in and explain.

 

You need to find out what your commanded fueling is set to, it may not be running lean or rich in relavence to commanded, it may be doing exactly what it is beeing told to do.

cruising A/F should be commanded 14.7, actual should follow right with it when the VE is dialed in correctly, so you should see 14.7 at everything below the PE threshold. ( i assume your using PE for wot fuel control)

At wot 13.0 is not a magic number, your commanded fuel ratio should be adjusted for what makes the best power in YOUR car, which is generally between 12.7 and 13.1 on a N/A setup.

What you need to first figure out is when you nail the throttle, is it actually commanding 14.7 for that first couple seconds, that will determine how to fix it.

If it is commanding 14.7 then youll need to change your PE threshold, if it is not commanding 14.7, then youll need to re-adjust your VE and MAF tables to get your fueling back inline.

 

Or can the MAF be damage and no reading right, because my car when into a flood, we had to open the engine and rebiult it and there was when i upgraded a few parts and bought most sensors new, but not the MAF.
How can i chack my PE?

 

a dirty or uncalibrated maf could cause this,

Your tuner can check your PE, this car has been tuned right?