Tony@NefMoto
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2001.5 Audi S4 Stage 3
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« Reply #30 on: September 16, 2011, 05:17:22 PM »
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The temperature correction of the MAF voltage is done by the sensor itself if I recall. I don't think the ECU has any involvement in temperature correcting the MAF voltage. I agree that it is possible the high intake temperature could be an issue with the stock MAF sensor in a blow through setup.
In case it hasn't been mentioned before be sure to check KFMLDMN, FWMLHFMMN, and MLOFS. They may give you some hints about your MAF readings at idle.
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Snow Trooper
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« Reply #31 on: September 16, 2011, 05:28:03 PM »
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I am going to try a rs4 style scale of the bosch maf with a large scale on positive voltage and a minor scale on negative... also, I dont have FWMLHFMMN and have never seen it in my stuff, FR says "Weighting factor fu ¨ r minimum threshold HFM-air masses in, reliance d.Ho · He"  |
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nyet
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« Reply #32 on: September 16, 2011, 05:45:19 PM »
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Why would you do that?
if your problems are temp related, it wont help to dick with the MAF curve regardless.
if they aren't temp related, why not start with a stock curve, and start logging stfts at various operating points and tweak kfkhfm, NOT MLHFM
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« Last Edit: September 16, 2011, 05:46:57 PM by nyet »
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ME7.1 tuning guideECUx PlotME7Sum checksumTrim heatmap toolPlease do not ask me for tunes. I'm here to help people make their own. Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your ex
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Tony@NefMoto
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2001.5 Audi S4 Stage 3
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« Reply #33 on: September 16, 2011, 05:51:30 PM »
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FWMLHFMMN is the scale factor for KFMLDMN
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Snow Trooper
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« Reply #34 on: September 16, 2011, 06:05:03 PM »
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who said the issues are temp related Nye?
I dont think they are at all. atleast not at these boost levels and ambient temps.
I previously used kfkhfm to fix all this, I am trying to get to the root of why blow through reacts this way and know how to make it work without a bunch of correction map intervention.
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nyet
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« Reply #35 on: September 16, 2011, 06:07:50 PM »
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Could it be flow related? Perhaps the flow is not well developed, depending on speed.
Do you have a flow straightener post compressor outlet?
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ME7.1 tuning guideECUx PlotME7Sum checksumTrim heatmap toolPlease do not ask me for tunes. I'm here to help people make their own. Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your ex
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Snow Trooper
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« Reply #36 on: September 16, 2011, 06:20:28 PM »
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yes, the maf is an oem housing with straightener and screen. its about 18 inches post turbo
i will try and get a new log or two tonight
I am starting with the biggest issue, the low maf readings. I can still get data even with idle on the 10s afr wise. id rather waste fuel then melt down.
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Tony@NefMoto
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2001.5 Audi S4 Stage 3
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« Reply #37 on: September 17, 2011, 01:57:49 PM »
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So just a quick summary, you moved your MAF from after the air filter to after the turbo. And the problems you now have are, at idle your MAF readings are too high and under high load your MAF readings are too low?
Looking at the pictures you posted earlier, it looks like you have a coupler hose going from a smaller diameter to a larger diameter immediately before the MAF sensor. I am wondering if the change in diameter could cause air turbulence dependent on air velocity which is skewing your MAF readings.
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Snow Trooper
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« Reply #38 on: September 17, 2011, 02:32:39 PM »
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Your summary is correct. I agree on the coupler thing. I need to do post ic again with no transition.
I kinda picture the smaller id pointing air through the maf housing.
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Tony@NefMoto
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2001.5 Audi S4 Stage 3
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« Reply #39 on: September 17, 2011, 03:32:16 PM »
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As far as I know, changing diameter or direction introduces turbulence. And if I recall correctly, turbulence will increase the cooling effect on the MAF hot wire, which will cause the reading to be higher.
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silentbob
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« Reply #40 on: September 18, 2011, 08:15:13 AM »
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I didn't read all this but are you aware of the fact that the Bosch and Hitachi MAF sensors are only speced to see a max temp of 120°C? At 6000ft with a AMP of ~ 810hPa and 18PSI boost you are at a absolute PR of ~ 2.7 which will easily exceed this temperature no matter how efficient the compressor is and how low the ambient temps are.
Stock cars are limited to a temp post compressor of ~150°C just to give you an idea.
I have never tried this but I can't imagine it's a good idea to place a MAF sensor in such a harsh enviroment.
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TTQS
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« Reply #41 on: September 18, 2011, 08:52:30 AM »
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you moved your MAF from after the air filter to after the turbo.  You moved your MAF from after the air filter to after the turbo? Sorry, I didn't appreciate that just by scanning your original post. I'm not surprised that you're having difficulties on grounds of temperature, pulsations, return air flow on overrun, air density, etc. I have never come across such a thing. Motronic ME7.x seems to have quite enough compensations for the usual pre-turbo MAF setup that I would expect putting it after the turbo would introduce so many more that it would be too difficult to deal with. I admire you greatly for trying it. Not particularly helpful comments though. I apologize. Doug |
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« Last Edit: September 18, 2011, 09:35:48 AM by TTQS »
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Snow Trooper
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« Reply #42 on: September 18, 2011, 10:10:41 AM »
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I think I solved it for the most part.
I am now getting proper readings, I will need to drive and log some more then I will post up results. For starters, you have to massively scale mlhfm.
Bob, thanks for the info, that is why I have always intended to go to an aftermarket maf that is designed for this style operation.
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Snow Trooper
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« Reply #43 on: September 18, 2011, 12:19:52 PM »
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progress...  need to do some big kfkhfm tuning. at least its following BTS again. I am also thinking about putting a temp probe post compressor. fwiw I never see IAT post IC higher than 110 F or so. |
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nyet
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« Reply #44 on: September 18, 2011, 01:31:23 PM »
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Looking decent! You could still use quite a bit more load/MAF... see if you can get it near 190 at peak torque and g/sec maybe around 300 at redline.. (and pull back KRKTE accordingly). maybe another 10-12% MLHFM and you should be gtg.
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ME7.1 tuning guideECUx PlotME7Sum checksumTrim heatmap toolPlease do not ask me for tunes. I'm here to help people make their own. Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your ex
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