PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

Today I tested the difference between SD and MAF mode both in open loop (Dyno inside)

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Old May 23, 2006 | 05:00 AM
  #41  
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Originally Posted by Black02SS
I doubt it.
Hey I did. I just got really frustrated. Its hard to learn over the net when you dont understand something. But buy tuning my own car with help is night and day Glad to see youve stepped it up bro!
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Old May 25, 2006 | 06:57 PM
  #42  
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Originally Posted by txhorns281
This is where we start to get into trouble, using words like "feel." Most people can barely feel 20 horses, and b/w a good MAF or good VE table you're not going to have a 20 or even 10 horse disparity anywhere over the power band. "Feel" is such a subjective word, let's try to stay away from it since it holds no real evidence.
Hey, "feel" is all I've got.

And with part throttle, how else would you measure it?

It FELT like I was missing 30 lb/ft of tq every time I hooked the MAF back up. Even my wife noticed how much quicker the car FELT at low rpms.

The most significant place was right at 2k rpms. In 2nd gear at 2k, I punch it in SD, the car pulls.

With the MAF hooked up, I punch it at 2k in 2nd gear, the car kinda goes, almost seems like it waits..... then pulls finally at about 3500 rpm.

I don't have a wideband, the only measurement I've got is fuel trims.

Fuel trims were all -2 to 0 in cruise/part throttle areas. The only difference in trims between MAF and mafless modes for me was this wierd QUADRANT effect.

See this thread...... http://www.hptuners.com/forum/showthread.php?t=5564

The last few posts have my log/tune and explain what's happening.
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Old May 25, 2006 | 07:16 PM
  #43  
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Originally Posted by silverTA2002

I don't have a wideband, the only measurement I've got is fuel trims.
That is your problem right there. You need a wideband as I'll put money down your fueling is all jacked up, causing the car to feel "soft".

Tune the car with a wideband and don't pay any attention to the ltft's. Then do the test and let us know what you think as I'll bet you will be suprised.
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Old May 25, 2006 | 08:05 PM
  #44  
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Originally Posted by Black02SS
That is your problem right there. You need a wideband as I'll put money down your fueling is all jacked up, causing the car to feel "soft".

Tune the car with a wideband and don't pay any attention to the ltft's. Then do the test and let us know what you think as I'll bet you will be suprised.
I concur
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Old May 25, 2006 | 08:16 PM
  #45  
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I farted
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Old May 25, 2006 | 11:02 PM
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Originally Posted by txhorns281
I farted
You stink.
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Old May 26, 2006 | 07:45 AM
  #47  
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Originally Posted by silverTA2002
It FELT like I was missing 30 lb/ft of tq every time I hooked the MAF back up. Even my wife noticed how much quicker the car FELT at low rpms.

The most significant place was right at 2k rpms. In 2nd gear at 2k, I punch it in SD, the car pulls.

With the MAF hooked up, I punch it at 2k in 2nd gear, the car kinda goes, almost seems like it waits..... then pulls finally at about 3500 rpm.
With a cam that moderate, you shouldn't have any issues with using the MAF. I do think that bigger cammed cars have more driveability issues at low RPM with the MAF on, but that isn't your problem.
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Old May 26, 2006 | 08:04 AM
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Have you guys ever logged the A/F into a VE table with the MAF enabled? Its pretty interesting to say the least.....
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Old May 26, 2006 | 08:25 AM
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I think most of you guys are expecting the stock MAF tables to still be accurate on highly modified motors. This of course will not be the case. Intake mods change airflow characteristics. Heads, cam and exhaust mods change reversion. Not to mention it stands to reason that as VE table needs to be adjusted to correct fueling, the MAF would require the same changes.

If youre wondering why your car run so much slower with the MAF in place, its likely because of one of two reasons. First and foremost, your MAF simply isnt tuned accurately, which is throwing off your fueling / spark. Secondly, a stock MAF on a highly modified ls1 will be an intake restriction. Upgrade the MAF or port out the stocker and re-tune it.
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Old May 26, 2006 | 08:37 AM
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Originally Posted by Phil99vette
Have you guys ever logged the A/F into a VE table with the MAF enabled? Its pretty interesting to say the least.....
explain por favor
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Old May 26, 2006 | 09:03 AM
  #51  
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very very nice thread!! Thanks for taking the time! Phil, Im with Mike on this one..please..go into detail.
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Old May 26, 2006 | 09:35 AM
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Originally Posted by Phil99vette
Have you guys ever logged the A/F into a VE table with the MAF enabled? Its pretty interesting to say the least.....


Mine was the same as the MAF table. They follow each other
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Old May 26, 2006 | 09:48 AM
  #53  
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Originally Posted by HumpinSS
Mine was the same as the MAF table. They follow each other
As it should be if both airflow models are tuned correctly, your engine utilizes the same amount of ariflow despite what sort of model you build for it, the MAF curve and VE tables are just the physical representations and best estimation of combustive airflow we can derive based on A/F burn and it's error margin. If we're looking for 0% error, you might as well wish in one hand and **** in the other and see which one fills up first. But have a small enough error swing to where both modes allow the car to function within a driver's tolerations, there's no reason why the A/F produced with a well-tuned MAF vs VE should be all that different. Assuming both are calibrated and built based on A/F % error.

Of course there are slight variances b/w models, but it's like using F=M*A and then converting to figure out what someone weighs, or hopping on a scale and getting a readout. Both ways ought to be damn close, give or take a pound or two partially due to rounding, miscalibration, resolution loss or even crappy math! Yikes!
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Old May 26, 2006 | 10:12 AM
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Originally Posted by Phil99vette
Have you guys ever logged the A/F into a VE table with the MAF enabled? Its pretty interesting to say the least.....
Mine are like HumpinSS, they follow each other and are the same after it is dialed in.
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Old May 26, 2006 | 10:14 AM
  #55  
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Originally Posted by txhorns281
I wish the search would fully work so that we could reference even more threads over a year ago that prove the SD vs MAF expectations. I think there are those of us out there that are almost blue in the face from screaming that there is little difference b/w the two for 99% of the setups out there.
I'm bluer then most, I gave up telling people a couple years ago, all I heard was 'My SD tune feels awesome, it just HAS to be faster.'

Still on a stock descreened MAF here, still even on the stock VE table lol. MAF table is highly tweaked though, car drives like stock everywhere and 1.31 60's off the footbrake @ 3300lbs is acceptable IMO.

People still wont believe you, the MAF is evil and must be eliminated
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Old May 31, 2006 | 04:58 PM
  #56  
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DAMN 1.31 60's . hahahaha, the MAF. This reminds me of what a guy once was talkin to me about: You want have sex without a condom because it feels better but your afraid of the consequences...

well you want to take the MAF off cuz it FEELS better...and your
(*possibly) afraid of the consequences.

**I Will say that a tuned SD car would have no problems.

had to add that
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Old Jun 1, 2006 | 06:22 PM
  #57  
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Just put the MAF on my car and did 3 quick tunes (still have some issues but those are just the minor details). Bottom line is there isnt a damn bit of difference in how the car responds or anything. If I tap the throttle in 1st to about 25% it jumps and barks the tires just the same as it did in SD. WOT is a different story since I have about a 11:1 AFR right now lol.

The car also is not lean on start up like it was in SD, which is the whole reason I decided to attempt this. Thanks Steve for the MAF to try out lol
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Old Jun 2, 2006 | 07:51 AM
  #58  
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After two weeks of driving the car I am gonna conclude there is no damn difference you if there is its the tuner not the car
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Old Jun 2, 2006 | 08:32 AM
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exactly

by the way, does the car respond better to hot and cold changes?
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Old Jun 2, 2006 | 09:02 AM
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Originally Posted by HumpinSS
if there is its the tuner not the car
Agree with HumpinSS on this. I think most tuners just half *** tune a car and he say it is close enough and call it a day. Then the owner has driveability issues. Running a SD tune things need to be dialed in much better, so people could think a SD tune is better than running a maf. The maf can take a half done ve table and get things close but when you take a dialed in SD tune and then calibrate the maf I feel things will be right then. I am tired of tuning my car 24/7 running in open loop because of temperature changes so I am putting the maf back on just like HumpinSS.
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