548chevelle

When I put on an Airaid intake the LTFTs increased by 5. I assume the extra airflow leaned the A/F and the ECM compensated by enriching the A/F ratio. I'm now adding Kooks long tube headers. I'll also be putting in a wide band O2 sensor that I had from a previous car. I'm also using a canned tune right now. I know that's not as a good as a dyno tune but until I can get it to a dyno shop I can use my handheld to dial in the A/F ratio should it be out of wack. Question is what are good A/F ratios with these bolt on mods? Also have a 160 thermostat and Magnaflows mufflers.

Mark2009

There is no extra airflow. Most CAI's 'work' by misreporting MAF to the ECM/PCM, tricking it into leaning out the A/F ratio (which increases WOT power).

12.5 open loop.

Z0-SICK

Some CAI's require adjusting your fuel trims but most do not. Halltech makes a Killer Bee version that does primarily due to the position of the MAF sensor.

Ideal AF ratio is Stoich or 14.7 to 1 during normal driving and anywhere from 12.5 to 13.8 I believe during WOT. Your vehicle is preprogrammed to always reach Stoich.

You always want your LTFT as close to 0 as possible. So if your seeing an increase it is likely due to your ECM compensating for more airflow. Your tuner can fine tune both of these when you have all your bolt on's. All he will be doing is simulating all driving conditions and taking the adjustment your STFT's are making and pasting them to a MAF table that automatically tells your ECM the amount of fuel to add by RPM and other factors. This speeds up the process and helps your car run more efficient and avoids KR.

548chevelle

There has to be more airflow. The IAT reading went from 105 to 80 degrees. That has to mean denser air. Also the vacuum reading between the air filter and the air meter was cut in half.

Unreal

" Ideal AF ratio is Stoich or 14.7 to 1 during normal driving and anywhere from 12.5 to 13.8 I believe during WOT. Your vehicle is preprogrammed to always reach Stoich. "

14.7 for pure gas but most places are blends. E10 is more like 14.2-14.1.

WOT depends, 12.5 is a good place to shoot for on a n/a car. Some cars like a bit richer, some a bit leaner. If you aren't tuning on a dyno then that is a good number to go for.

Car is not programmed to always reach stoich. In closed loop, it will use fuel trims to attempt to get close, but WOT is open loop only and car does not adjust (besides applying positive fuel trims) at WOT. So saying it always trys to reach stoich isn't accurate. During some parts of part throttle low load driving, it does. Cold Starts, Warm up, other times, and WOT it does not.

And a good tuner should be doing a hell of a lot more than just adjusting fuel trims and maf tables. VE needs to be addressed too. Timing, IAT tables, ECT tables, Tq MGT, etc etc etc.

Z0-SICK

I wasn't trying to get too technical here and when I said "normal driving conditions" I meant closed loop.

The OP's question was: What is an ideal AF ratio for his bolt on's? There is no simple answer to that question. My answer was to, as simple as possible, make him understand the process.

The entire process I described was referring the VE tuning by the way........

Jesus Christ!