Air intake and maf needs a tune?
08-29-2011, 05:44 PM
#2
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If you picked a non-stock-calibration MAF, then, yeah. And for an
extra bonus, you picked one that the manufacturer provides no
support data for. Double the fun, at shop rates.
See if you can find a tuner who's got the GMAF table figured out.
Learning on the job is not what you want to be paying for.
extra bonus, you picked one that the manufacturer provides no
support data for. Double the fun, at shop rates.
See if you can find a tuner who's got the GMAF table figured out.
Learning on the job is not what you want to be paying for.
08-29-2011, 07:58 PM
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I would bet that the curves are qualitatively similar, but the scaling and
whether it's linear or not, are "an exercise for the student" since the
teacher has cashed the check and doesn't return your calls.
whether it's linear or not, are "an exercise for the student" since the
teacher has cashed the check and doesn't return your calls.
08-29-2011, 08:16 PM
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Ahh gotcha.. Just different scaling all together. Could you almost find "close" numbers, correlate from the stock scale and then interpolate between odd ones, burn the tune, run it and find a correction factor, go back and correct for the percentage??
08-29-2011, 10:02 PM
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The only "shade tree" way I've thought up, is to do some pulls from idle
to redline with first the GM stocker, and then the new piece, and then
get both datalogs into Excel where you'd plot the MAF Hz against
(RPM*MAP). You can go from GM Hz to g/sec for a given MAP*RPM,
and then for the same MAP*RPM apply that g/zec to the GMAF Hz
cell, whatever it is.
Tedious, and you'd want the screen out which introduces potential
error itself (or not).
I have set up before a couple of MAFs in a tandem tube and taken
same-air Hz readings, back when I hogged an 85mm Delphi to get the
same high-flow reading as a stock 75mm. But the result was a very
unstable low-flow reading on-car, so it was basically pointless fun.
So there's ways to do it. Just none I'd pay a tuner shop $150 an hour
to try.
to redline with first the GM stocker, and then the new piece, and then
get both datalogs into Excel where you'd plot the MAF Hz against
(RPM*MAP). You can go from GM Hz to g/sec for a given MAP*RPM,
and then for the same MAP*RPM apply that g/zec to the GMAF Hz
cell, whatever it is.
Tedious, and you'd want the screen out which introduces potential
error itself (or not).
I have set up before a couple of MAFs in a tandem tube and taken
same-air Hz readings, back when I hogged an 85mm Delphi to get the
same high-flow reading as a stock 75mm. But the result was a very
unstable low-flow reading on-car, so it was basically pointless fun.
So there's ways to do it. Just none I'd pay a tuner shop $150 an hour
to try.
08-30-2011, 01:43 AM
#7
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So... I know someone with ls1 edit.... could he get a good tune on the street for it or not? I have never tuned a car myself but he sounds confident about it. He had a 402 stroker trans am and he tuned another friends car that had a big cam and both run/ran excellent.
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08-30-2011, 06:47 PM
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The only "shade tree" way I've thought up, is to do some pulls from idle
to redline with first the GM stocker, and then the new piece, and then
get both datalogs into Excel where you'd plot the MAF Hz against
(RPM*MAP). You can go from GM Hz to g/sec for a given MAP*RPM,
and then for the same MAP*RPM apply that g/zec to the GMAF Hz
cell, whatever it is.
Tedious, and you'd want the screen out which introduces potential
error itself (or not).
to redline with first the GM stocker, and then the new piece, and then
get both datalogs into Excel where you'd plot the MAF Hz against
(RPM*MAP). You can go from GM Hz to g/sec for a given MAP*RPM,
and then for the same MAP*RPM apply that g/zec to the GMAF Hz
cell, whatever it is.
Tedious, and you'd want the screen out which introduces potential
error itself (or not).
08-30-2011, 07:57 PM
#12
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No, closed loop will "learn" that the MAF is bogus lean, jack your
trims positive, and then you'll carry that baggage at WOT. So the
net result may be no "lean out for power" in the end, or it may be
even worse than nothing (over-enriched) if the error is larger at
the low end than the high end, -and- the trimming will vary by
what fuel trim cell you step off from into WOT making the thing
mighty hard to get consistent WOT fueling.
Best to not start with lying to the computer, and chase all the
bullshit out of the system before it has a chance to get ripe.
trims positive, and then you'll carry that baggage at WOT. So the
net result may be no "lean out for power" in the end, or it may be
even worse than nothing (over-enriched) if the error is larger at
the low end than the high end, -and- the trimming will vary by
what fuel trim cell you step off from into WOT making the thing
mighty hard to get consistent WOT fueling.
Best to not start with lying to the computer, and chase all the
bullshit out of the system before it has a chance to get ripe.
08-30-2011, 08:10 PM
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^^ I'm sorry but I am REALLY getting tired of this "It'll learn it" stuff... 
Fuel trims change, that's different.. A PCM cannot "learn" to correct a maf calibration itself. Unless it's a self-calibrating stand alone system. Even those, I think may require some bit of human interface to set "zero" or Lambda. And just because it runs and drives does not mean that you are running at stoich, MBT or peak VE.
Fuel trims change, that's different.. A PCM cannot "learn" to correct a maf calibration itself. Unless it's a self-calibrating stand alone system. Even those, I think may require some bit of human interface to set "zero" or Lambda. And just because it runs and drives does not mean that you are running at stoich, MBT or peak VE.
09-01-2011, 06:21 PM
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The only right way to do it is to tune the VE table in speed density first - using a wideband - and then tune the MAF table using the wideband... that way you are not guessing whatsoever for the entire curve...
09-02-2011, 07:46 AM
#17
I agree that it is necessary for a tune. I have seen several motors let loose from intakes that were just slapped on in forced induction applications with no tune. NA motors are the same. This is especially true the further you go from a stock motor.
Most aftermarket intakes are larger than stock, so more air is going by the MAF than it thinks is there making the air fuels leaner. This is exponential the higher the flow as more more air goes by at any given MAF signal.
Most aftermarket intakes are larger than stock, so more air is going by the MAF than it thinks is there making the air fuels leaner. This is exponential the higher the flow as more more air goes by at any given MAF signal.
09-03-2011, 03:04 PM
#19
Or you can use a narrow band that is on the car for most of the VE/MAF tuning that is not WOT or the area where PE is active. The mostly "around town" stuff. Then use a wideband for the rest WOT and PE.
