MAF Tuning for WOT

[hook]

My LTFT are dialed in very close to 0 with no KR. I started to work on MAF table at WOT but have a quick question. I've disabled COT and LTFT set my PE and did a test run from 2nd. Of course it was off by close to 10%. I'm using an AFR error histogram. Do I just copy the entire row of data (from 0 to 15,000Hz) and paste special over the same cells in the MAF Calibration table? This is the same table I used on my LTFT's. I'm worried that the lower Hz data here will screw with my LTFT's when I enable them. Or do I start my copy in say the 5150 Hz cell and copy and paste only after that?

Also should I be seeing KR at WOT? If I am is my PE set too low or will it correct itself as I bring the MAF table closer to 0?

[mowton]

The reality of it is whether you are commanding Lambda 1.0 (14.2) or PE of say Lambda .87 (12.35), the MAF values should be the same. PE ( or other enrichments schemes) merely are adding to the Stoich values you set. The plan is to get the MAF dialed in across the board, then you can manipulate the PE values and feel confident of the target Lambda (AFR) to manage torque or knock.

The only thing that will disrupt this from what I have seen is the moment the PE is enabled there is a bit of lag for the fueling to catch up so you see a lean event for say 200 ms. or so. Filter this out and your steady state MAF values developed from your LTFT/STFT should be very close to any overlap developed from the WB in OL/WOT tuning sessions.

There should be no KR, if you are lean than that may be contributing to your results. Set PE vales for NA to say .85/87 and FI to .75/.77 to start and tune accordingly. sometimes Header/Cam?blower installs develop acoustics which exceed the stock/OEM settings and can trigger false knock. If you set the fueling correct and remove the knock values from your Spark table and it is still there, then you need to desensitize the knock sensors a bit.

Also 3 reminders...1) don't forget to reset your fuel trims before each tuning session 2) keep your data collection as close to steady state as possible, even/slow pedal increases and filter enough of the decal etc events out to arrive at the most accurate values and 3) don't forget to touchup your VE table in the 0-4000 (or where ever your blended mode break is) rpm area's before reverting back to Closed Loop.

Ed M

[ingsteve]

Filter your maf histogram for commanded afr <14 and you will see the maf data only from higher f....

[hook]

thanks, make much more sense now

[mowton]

Filter your maf histogram for commanded afr <14 and you will see the maf data only from higher f....

Agree for lower frequencies (non-WOT/PE data) and Wideband will be needed for WOT/PE (<1.0 Lambda/14 AFR) tuning. The LTFT/STFT are disabled during wot.

Ed M

[hook]

Agree for lower frequencies (non-WOT/PE data) and Wideband will be needed for WOT/PE (<1.0 Lambda/14 AFR) tuning. The LTFT/STFT are disabled during wot.

Ed M

thx, I'm using a Wego IV Wideband. I set up a Histogram for AFR High Freq and found out I was a tad lean. Adjusted
PE to 1.176 and walla! no KR.

[mowton]

thx, I'm using a Wego IV Wideband. I set up a Histogram for AFR High Freq and found out I was a tad lean. Adjusted
PE to 1.176 and walla! no KR.

Just make sure you are not increasing PE to compensate for lean MAF settings in the WOT area. As I said, you should tune the MAF to reach the PE target value. When you changed to 1.176 to correct lean condition, what was the commanded PE prior to that? I work in Lambda so 1.0 is stoich and target PE would be .85 which is equivalent to your EQ Ration of 1.176.

At this PE, what was you AFR error? If close to 0% then perfect job. If not, you have just "rapped" your first PE :-)

Ed M

[hook]

Just make sure you are not increasing PE to compensate for lean MAF settings in the WOT area. As I said, you should tune the MAF to reach the PE target value. When you changed to 1.176 to correct lean condition, what was the commanded PE prior to that? I work in Lambda so 1.0 is stoich and target PE would be .85 which is equivalent to your EQ Ration of 1.176.

At this PE, what was you AFR error? If close to 0% then perfect job. If not, you have just "rapped" your first PE :-)

Ed M

good question. I'll double check today. my maf was relatively close to be dialed in at wot, it was just the kr and i believe there was some afr error. when i get back to my laptop ill check. i see you have a vette also. im working on an LS3 and noticed my maf Hz never get past say 9000Hz even at wot. is that normal? just currious.....

[Bluemamba]

I've been wondering about that as well. 9000Hz is all I get at WOT.(2011 LS7)

[MikeOD]

I've been wondering about that as well. 9000Hz is all I get at WOT.(2011 LS7)

Depends on the size of the tube the MAF is in, the location of the MAF, and how much power you're making.

Look at the shape of the MAF curve...as airflow goes up more and more, frequency goes up less and less (it's a polynomial curve)...the difference in airflow from say 4000-5000hz is a LOT LESS than the difference from 9000-10000.

[hook]

Depends on the size of the tube the MAF is in, the location of the MAF, and how much power you're making.

Look at the shape of the MAF curve...as airflow goes up more and more, frequency goes up less and less (it's a polynomial curve)...the difference in airflow from say 4000-5000hz is a LOT LESS than the difference from 9000-10000.

ahhh haa!