Topic: The magical gmpp tune

[Kelu]

shabby how much do you think the MAF relocation influenced this reading?

[Critterman]

elf,
Just buy the credits, Joe and I both have HPT, as does Kenny I believe

[Brazen17]

Wow, that is a fantastic change!  That is about a 40% change if my mental math is right!  (I have had a few sips of "American Forest" so who knows...)

If the same change were true of 0-60 times, you car would have gone from 5.5 seconds to 3.2 seconds!  That is super car numbers!  I know that the math is not representative of real life, but that is amazing % changes...

GJ

If we could only get it to hook up!

[kennysabarese]

30mph in 3rd gear is miserable. None of my logs even start that slow. Just lugging the engine. I usually start my logs from 45mph. Usually I have to log on the freeway so I can't go much slower than that since NJ is a pretty busy place

[shabby]

shabby how much do you think the MAF relocation influenced this reading?

I don't think it skewed the readings at all, the ID of the intake and my shabby pipe is 3" and virtually identical, plus my fuel trims are as close to 0 as can be.
I relocated the maf almost 2 years ago, so the 7.03 time was done with the maf relocated already.

30mph in 3rd gear is miserable.

Ya i know, but i want to get an idea of how fast the turbo spools at low rpm. I have some logs starting at 1500rpm, never doing those again.

[kennysabarese]

Air pressure will cause MAF sensors to give a different reading according to some reading I did on wikipedia and everything you read on the internet is true right?

[shabby]

Maf sensors read air mass not pressure, so sticking them in the ic pipe shouldn't affect them. And yes everything on the internet is true, im going to be a millionaire soon according to this prince that emailed me recently...

[kennysabarese]

I know it doesn't read pressure, but allegedly the pressure affects the density, which would affect the reading....

Trying to sort out from an unclear wikipedia article about it http://en.wikipedia.org/wiki/Mass_flow_sensor

[shabby]

If it does affect them its minimal at best, a lot of people run gm mafs in blowthrough without issues.

[kennysabarese]

We're just curious because it's unlikely you are making 390bhp

But if you are and can prove it on a dyno... I'll be using your tune parameters

[kennysabarese]

Ok one more thing about the MAF. Does the HPT correction table actually change the # you get for the MAF value? Or just change the amount of commanded fuel because the sensor is now showing a different number than it did before.

If it's the latter, that means your MAF numbers cannot be compared to other Kappas, and can no longer be used as an estimator of horsepower.

I'm trying to find out which type of MAF we have, vane, hotwire or coldwire.

[Uranium-238]

I think ours might be hot film...

[shabby]

Ok one more thing about the MAF. Does the HPT correction table actually change the # you get for the MAF value? Or just change the amount of commanded fuel because the sensor is now showing a different number than it did before.

The maf calibration table changes the curve of the maf and the maf correction table fine tunes it based on load/rpm. Since i relocated the maf i have to fiddle around with these, otherwise the car wouldn't run right. I use fuel trims to get the maf reading to as close to stock as possible, otherwise my stft would go off the chart under wot. If you're still skeptical forget about the maf readings and try to duplicate my 30-85mph 3rd gear pull.
I think its a hotwire maf too.

[kennysabarese]

I was skeptical until you explained to me how it worked. The way I assumed it worked was different. I'm just trying to learn.

I assumed 2 things, that the MAF reading comes directly off the MAF sensor in lbs/min so that it was impossible to modify it. I guess it actually just gives a voltage and the ECU does some math to give you the reading in lbs/min and the tables actually modify the calculations so your lbs/min number is accurate.

Second assumption was that it worked like how the temp tables adjust timing. If you see X value. Retard or Advance Y amount. In that case, if the MAF value was 60 instead of 30 you could just halve the values in the correction table and your fuel would be right on.

I guess the question I should have asked first was this. When you first relocated and calibrated the MAF without changing the boost level were the MAF numbers the same as they were in the stock position.

I'm shooting to do some logging tonight. I'll see what I can do.

[Kelu]

If you're still skeptical forget about the maf readings and try to duplicate my 30-85mph 3rd gear pull.

Can I try that downhill or pulled by my friend's 11s car? 

[shabby]

I guess the question I should have asked first was this. When you first relocated and calibrated the MAF without changing the boost level were the MAF numbers the same as they were in the stock position.

Once i got the maf dialed in they were identical. The maf spits out a hertz value, then the ecm manipulates that based on a whole bunch of algorithms to get a useable reading. The hertz value is pretty much steady a wot yet the airflow values change, im sure there's some rpm+ve calculations going on inside the ecm.

Can I try that downhill or pulled by my friend's 11s car? 

Try drafting behind a ferrari   

[kennysabarese]

Once i got the maf dialed in they were identical. The maf spits out a hertz value, then the ecm manipulates that based on a whole bunch of algorithms to get a useable reading. The hertz value is pretty much steady a wot yet the airflow values change, im sure there's some rpm+ve calculations going on inside the ecm.

Ok skepticism is gone. Now I just hate you because you have almost 370-400 crank horsepower with the stock turbo if the ~10hp per lbs/min is legit

[shabby]

I don't think its that high, to make 260hp the turbo is flowing 28lbs/min and its in the efficiency range, i'm nowhere near its efficiency island with the current tune.

[kennysabarese]

but you said in the other thread that the turbo is 73% efficient at 30psi. vs 78% max. that isn't too bad is it?

[kennysabarese]

I can't get down to 30mph on the freeway. but I did a few 40-85

my best for that was 5.7 when i started from dead on 40 it was about 5.9

since you are doing 30-85 in 5.4 seconds... that's pretty impressive.

[kennysabarese]

my IATs are hitting around 110 IAT2s are hitting 130 with ambient being around 90

Actually wtf. on some of my pulls the ambient air temp changes a lot across a 20 second long log. that's strange

but yeah so I really think i need an intercooler. Then I could run more advanced timing right?

Good news is that my MAFs are still ~35 and I have no knock in 3rd gear. Only a little in 4th when I am pulling really high load in low RPM. I think L reduced my timing a bit because I had a lot of KR.

[shabby]

but you said in the other thread that the turbo is 73% efficient at 30psi. vs 78% max. that isn't too bad is it?

Its 73% efficient at 30psi when its flowing 28lbs/min, you have to find the flow rate at the bottom of the graph and the pressure ratio at the left side and find the cross point on the graph. The turbo doesn't stay at 30psi for long, its mostly between 20-25psi.
My 40-85 mph was 4.2 seconds, after looking at the logs again starting it at 30mph really slows the run down since its starting at a mere 2000rpm, at 40mph its at a better 3000rpm.

[kennysabarese]

ah. well i gotta get my PSI meter working in HPT. My vmware got f'd up and I lost that config. ran out of time today to fix it and log again. packing for the track weekend