Easy Way to Adjust Fuel Trims With Hptuners
- #1
I am near the end of may MAF (Mass Air Flow) tuning, and took the time to compare the stock 2006 Cobalt SS Supercharged MAF tune to the Goblin MAF tune.
The only difference is the shorter DF Goblin intake, with the DF supplied Edelbrock air filter, and the shorter 2.5" DF exhaust with the catalytic converter deleted.
But boy, do those changes make a difference! Or is the difference related to something else? Maybe a 13 year old MAF sensor? Do they wear?
The chart shows "MAF Frequency" in bold along the top. (spreadsheet line 3) The MAF freq. basically follows the engine RPM, with higher freq. at higher revs.
Then for yesterdays tune, the pounds per hour of measured airflow for a given MAF Freq. (line 5)
Then for the stock tune, the pounds per hour of measured airflow for a given MAF Freq. (line 8)
The stock tune is 22% lean at idle... then gets pretty close in the mid RPM range, then gets real lean again when the supercharger is screaming.
Now a stock engine will learn the LTFT (Long Term Fuel Trims) up to 20% richer, as needed... but the first while when I started driving my goblin, I was running lean.
And even after the LTFT table get filled out, the engine will still be lean in places, until the STFT (Short Term Fuel Trims) adjust... which is forgotten every time you start your car.
After I finish the MAF tuning, I am moving on to the VE (Volumetric Efficiency) tuning.
I'm really hoping this makes the throttle easier to drive a supercharged goblin.
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- #2
I just had mine dyno tuned at ZZperformance. Before tuning, I had codes showing lean idle. The first dyno pull showed AIr/Fuel ratios in the low 20s at idle... at the top end it was way lean and the power fell off like crazy. It wouldn't pull past 6000 rpm. You could hear it fall flat.
- #7
ZZPerf kept my files. I do not have HP Tuners so it was meaningless at the moment. They have the final tune saved off if I should ever need it. They said I could purchase HP tuners and tweak I should like in the future. I don't think they locked it down...
I know the DF intake and exhaust definitely changed the tune from stock.
It is also so much quieter, smoother and well behaved now. My wife even noticed how much quieter it is now during normal driving.
- #11
Yeah, and then in the next tune I was sent it was dropped to 1200 RPM and ran worse.
It's my understanding that parameter controls when it switches from SD to MAF. So you are not using MAF tune until over 5800 RPM?
And I just checked the OEM value for my car, 7000RPM??
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- #17
My settings for VCM Editor in order to start VE Tuning.
In VCM Editor, if you open the file "20191104 VE tuning.hpt"
then go to Compare, and open this compare file: "Goblin LSJ MAF tune 205F fan -4MIL.hpt"
To see the changes, go to Compare, View comparison log.
The first change, Primary VE vs RPM vs MAP: Richen up the mixture (say 10%, all cells), so that the engine doesn't run lean while logging VE errors in open loop.
2nd change, Closed Loop Enable... : set the temp so high that the engine will never enable closed loop.
one change at a time you can see my settings.
The last difference doesn't count, as I played with my fan temperatures, which is not related to VE tuning.
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- #18
Looking at your VE tuning setup; I noticed that you are zeroing out the open loop adders. I was going to do this next but the Goat Rope never said anything about it in how to set up VE tuning. I have COT permanently disable since we don't have one anymore. Also you have Piston Protection turned off during tuning, I may try that also to see if that is causing issues. This helps me a lot. I will try some of these additional settings to see if I can get a better scan data.
You VE table is much more smooth than mine other than the huge spike at 46 kPa in the middle of the RPM range. 4096??!!
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Source: https://dfkitcar.com/forum/index.php?threads%2Fhp-tuners-maf-ve-tuning.1388%2F
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