MAF Calibration (No Spreadsheets!)

OK that was interesting:Eyecrazy:

I made the mistake of trying to MAF calibrate using CL and I guess the trims were messing me up. Seems like I was chasing them and getting nowhere, the bens were 1.04-1.05 I would make apply the ben to the MAF table and I chased (again they were 1.04-1.05) them til I threw the Fuel Trim Rich codes, then I came back and reread the thread.

So I did a couple of logs yesterday OL with MAF enabled (using the stock MAF table) what I was expecting to see was Bens of 1.00 or so since thats where OL (no MAF) had them and what I ended up with was Bens that were .85 on the MAF Freq MAP. I averaged the readings from the two logs, and applied the .8X bens (copy w labels, paste and multiply w labels) to the MAF table. Seems like the MAF has a huge part in CL (I thought it was used 4000 RPM and higher).

I am hoping that my MAF Bens start doing what I think the should and be closer to 1.00

Am I on the right track now?

You can tune the MAF in open or closed loop. Closed loop, you use the trims assuming your NBO2's are somewhat accurate around stoich. But, you are limited to CL operation for tuning accuracy. Outside of CL, I don't trust the NBO2's at all. The trick is to disable LTFTs and tune off of the averages of the STFT percentages. Filter out fuel trim cells above 19 to get rid of open loop/decel, fuel trims where STFT's=0 (-0.01%<STFT's<0.01%) to get rid of laziness, and cells where TP% is changing too much. This will at least get you close.

If you want to tune with the WBO2 and BEN's, then you need to command open loop, log the appropriate pids, and again use the right filters.

Either way will work assuming two things...
1) You're doing it right...no user error.
2) Everything mechanical is working right....WBO2 or NBO2's, no intake/exhaust leaks, etc.

If your car suffers from the side effects seen on many C5's with LT headers, tuning the MAF in CL might become troublesome and cause you to chase your tail a little. If not, I'd say the tail chasing you were doing is more related to user error (maybe you didn't use your filters right?).

Using the VE filters in the tutorial, but I am accepting less than 50 hits (I think 10) because my test circuit is limited in what I can do traffic and time wise (limited laptop battery life). No headers, pretty much stock, have a new LS6 intake vice the LS1 and catbacks. Using an LC-1 WB for logging.

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Originally Posted by Beer99C5

Using the VE filters in the tutorial, but I am accepting less than 50 hits (I think 10) because my test circuit is limited in what I can do traffic and time wise (limited laptop battery life). No headers, pretty much stock, have a new LS6 intake vice the LS1 and catbacks. Using an LC-1 WB for logging.

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What I did for those is look at what the surrounding cells are doing. Data points with 10 hits are useless. The stock MAF curve is fairly accurate and does well when progressively scaled. If you use the compare feature to look at your current calibrations vs. the stock table, you can see the delta %. If 3000Hz is roughly 3% over stock and 3500Hz is 3.5% over stock but you don't have that many readings for the 3125~3375Hz range inbetween....increasing them 3.25% over stock is a relatively good educated guess and will get you close. If you use the spreadsheet I built, it's easier to see the percentage change and make adjustments for the cells you didn't quite hit enough times. Ironic I push the spreadsheet given the title of this thread??? Yes...but it's extremely easy to use and it's virtually dummy proof.

My MAF table increases at .5% intervals over stock starting at 3000Hz until it reaches 6.5% over stock at 4500Hz (ie 3000 has a .5% increase, 3125 has a 1% increase, 3250 has a 1.5% increase, and so on until I get to 6.5% at 4500). Above 4500Hz, I carry the 6.5% increase all the way to the top because that's what I know the car likes at WOT. I used these settings based on watching the trims and using the WBO2 for WOT. Now my fuel trims fall into a -5%~-2% range. It's not 100% perfect nor will it ever be....but they're in a good spot. That, IMO, is the trick to tuning. If you drive yourself nuts sweating the details trying to get everything in line 110%, you'll never be able to enjoy the vehicle. In my case, the -5% LTFT's are well within the limits of the PCM for adjust during CL operation and WOT is right where I want it...so, I'm done with this tune until the next mod. :)