Is there any other way to get A/F numbers other then from a dyno

[WeezieMarion]

Can you get it through pluging into the OBDII while driving?

Maybe the computer does not monitor A/F

[FordMan]

The computer reads voltage from the O2 sensors but you would need some way to convert that to a numeric A/F ratio. The best and only way I know of to determine your A/F ratio accurately outside of a dyno shop is to install a wideband O2 monitor in you vehicle with the sensor mounted upstream of the cats. Costs some $$$ though.

[WeezieMarion]

FM,
Maybe you don’t need the A/F numbers to tune for proper mixture. Assuming that the voltage changes the same way the A/F ratio, would it be possible to tune if you know what the voltage range should be and lean or richen the mach to fall in that range after the mods are added? What should a stock Machs voltage read?

[FordMan]

I don't know what the voltages would correspond to with respect to A/F ratio. If there is a correlation you would need to monitor the values from the upstream sensors only as opposed to the ones after the cats. You would also need to datalog them at WOT in fourth gear (if you have a 5-spd) up to redline, and that isn't necessarily easy to do on public roads.

[WeezieMarion]

You would also need to datalog them at WOT in fourth gear (if you have a 5-spd) up to redline, and that isn't necessarily easy to do on public roads.

Yeah, you're right that would be hard to do. Plus the software would Probably
cost a mint anyways.
Thanks

[FordMan]

Look inyo the SCT Pro Racer Package. It allows the user to do nearly everything a professional tuner can do and I don't think it's prohibitively expensive.

[Voodoo96743]

Originally Posted by FordMan

I don't know what the voltages would correspond to with respect to A/F ratio. If there is a correlation you would need to monitor the values from the upstream sensors only as opposed to the ones after the cats. You would also need to datalog them at WOT in fourth gear (if you have a 5-spd) up to redline, and that isn't necessarily easy to do on public roads.

Wha? No, you don't need to be in 4th to datalog, only to get dyno hp/tq numbers. The engine is running the same at 3,000rpm in 2nd as 3,000 rpm in 3rd.

As for monitoring A/F from your O2 sensors, they're called narrow band for a reason. To understand that, you need to understand A/F basics. 14.7:1 is stoichiometric, meaning air and fuel are equal. Above 14.7:1 is lean, more air than fuel. Below 14.7 is rich, more fuel than air. IN A PERFECT WORLD YOU WANT 14.7. In real life we're looking at running in the 12-13:1 range If you're at WOT and you're at 14.7, you could be in trouble. So someone might say that they were running lean at 13.5:1. Supercharged/turbo'd engines need to run richer than N/A to keep cool. A wideband O2 sensor will tell you exactly where you are. I think most can read between 10-18:1. A narrow band like the stock O2 sensors will only tell you if you are at, above, or below 14.7.

[jchambers]

Originally Posted by Voodoo96743

Wha? No, you don't need to be in 4th to datalog, only to get dyno hp/tq numbers. The engine is running the same at 3,000rpm in 2nd as 3,000 rpm in 3rd.

Load will be different in the different gears though. Fuel and spark are dependent on load (along with many other parameters). When you're datalogging, be sure to capture the calculted load so that you can determine just where you're running compared to the commanded lambda. Lambda at 3000 and 10% load can be 1.0 while at 3000 and 100% load you'll want it significantly richer.

[Voodoo96743]

Originally Posted by jchambers

Load will be different in the different gears though. Fuel and spark are dependent on load (along with many other parameters). When you're datalogging, be sure to capture the calculted load so that you can determine just where you're running compared to the commanded lambda. Lambda at 3000 and 10% load can be 1.0 while at 3000 and 100% load you'll want it significantly richer.

If you're caputuring the calculated load, is there any reason you need the 1:1 of 4th to capture it?

[jchambers]

Nope, 1:1 really becomes meaningless out on the road. If you're datalogging, capture some of the following to really give some insight into how the car is tuned:

Engine speed (rpm)
load
maf counts
ACT
ECT
Spark
Spark source
knock sensor retard
STFT & LTFT (both banks)
pressure drop across injectors

I also log idle air integrator and desired idle rpm for idle tuning. There are plenty more that become important in the full tuning of the car, but if you can capture these and show them to your tuner, he should be able to decipher what's going on.

[WeezieMarion]

Excellent stuff Thanks! Do you guys know of a web site that explains datalogging and wide band O2? How to also