ChevyNo1

I'm sure I've seen people mention here about the relationship between Autotap-reported MAF rate and HP. I seem to recall that if you take the rate and multiply by 10, that's your approximate HP. I also seem to remember that is at the rear wheels. Any comments?

- Dug

turbolx

Yes, airflow is directly proportional to horsepower. Generally speaking, forced induction cars will make in the neighborhood of 10 flywheel HP for every 1 lbm/min airflow. (You must convert from g/sec to lbm/min) HOWEVER, if you have tweaked the MAF curve in any way to get a certain fuel trim, all bets are almost surely off as far as accuracy. Every car is slightly different in volumetric efficiency, burn efficiency, etc., so don't take it as gospel, merely a "quick and dirty" guesstimate of power production to see if your dyno numbers jive.

ChevyNo1

OK, dumb question here then, but is Autotap reporting in lbs/min or g/sec? Because my reported rate peaked at 44. If that's lbs/min, then that's only about 375rwhp from a twin-turbo LS1, which is pathetic. I had 335rwhp with only free mods, 4.11 gears, ASP pulleys, and lid!!! Plus the car sure feels like it's pulling a lot harder than 375rwhp.

- Dug

Nickn20

my friends cammed car peaked at 51#s! <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> I cant wait to see what he dynos im guessing over 400 rwhp.

SS00Blue

Stick a crowbar in your wallet and spend the $60 for 3 dyno pulls. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

S-

ChevyNo1

Yea, I will be doing that soon. Just waiting to get LS1-Edit and alky injection before I go.

- Dug

smokinHawk

iTrader: (48)

Greg Do you remember what mine was off hand. I know the g/sec on one of my logs I ran was abound 12222 g/sec. what does that convert to lbs/min

smokin t/a 600

hey ss00blue, i live in walled lake also, i live in commerce township. maybe we could hang out somtime.

smokinHawk

iTrader: (48)

i think i got the wrong number when i did the calculation it was way off. ill have to go back and look at my logs.

turbolx

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by JAS:
<strong>Turbolx - That was said very well.

It is somewhat accurate ONLY with a stock MAF in stock position without a major induction change. Putting a cone filter on the end of a MAF will change the results, etc. If you edited you maf table, removed the screen, changed the induction, changed the maf, maft, etc.. etc.. well you get the point. Use a dyno. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Jas, thanks. Compliments like that make me actually feel good about signing the checks to still pay off those student loans from GMI. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> But yes, like you said (and it can't be repeated here enough) this ASSumes a stock MAF input to the PCM. Hence my original caveat. Too many poeple on here already have translators or have otherwise molested either the curve or the meter itself, so I would never expect it to work on every car.

Jon, I don't recall exactly where yours landed, but rest assured it was "in the ballpark" for the ~500+ rwhp the dyno showed. Your car should feel like every bit of ~58-62lbm/min. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

ChevyNo1

Jas, no, the MAF has not been touched. Of course, things have been moved around with the TT kit . . . all I know is that the car sure FEELS like it's pulling harder than what the MAF is reporting. I plan on getting it tuned with LS1-Edit on a WB sometime in November. I'm wondering if it's possible that it's not reporting it properly. This is at 5psi. It's running completely stock programming as well.

- Dug

Nickn20

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by smokinHawk:
<strong>Greg Do you remember what mine was off hand. I know the g/sec on one of my logs I ran was abound 12222 g/sec. what does that convert to lbs/min</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">is that one too many 2s? multiply by .1323 and you have your lbs/min which would be 1616.97 lbs/min

Nickn20

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by JAS:
<strong>Turbolx - That was said very well.

It is somewhat accurate ONLY with a stock MAF in stock position without a major induction change. Putting a cone filter on the end of a MAF will change the results, etc. If you edited you maf table, removed the screen, changed the induction, changed the maf, maft, etc.. etc.. well you get the point. Use a dyno. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

ChevyNo1 - Boy I hope you have that MAF tweaked or something because 44lb/min on a blown anything LS1 isn't doing so well. I see cam and header cars pull 41lbs at WOT. Hope you find the problem.

NickN20 - If he has a MAFT or program or anything that tweaked the MAF, all bests are off. 51lbs from a cam only car? Hmmm....</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">its a LS6 MAF calibrated for a LS1 and some LS1edit runing, for his Ltrims and I leaned it out a little in the PE vs RPM table, which doesnt really affect the maf.

red ws6 99

Dug are you still using the stage II Incon computer. If you are make sure you check where you have it set to clip the maf signal. Its changable so you might be getting a lot higher numbers but the pcm is only seeing the clip value.

Gary

ChevyNo1

Gary, it is still plugged in, but has all 0's in the fuel/timing. But I do remember changing something for the MAF . . . do you remember where it is set, and what I should set it to? Also, other than how the PCM sees it, would that affect performance?

- Dug

<small>[ October 18, 2002, 01:21 PM: Message edited by: ChevyNo1 ]</small>

smokinHawk

iTrader: (48)

On one of my log data poits it read MAF 12225 not sure what thats for. BUt one oter log poits read MAF 58, guess thats the number i wanted.
only 58 i want more!

Nickn20

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by smokinHawk:
<strong>On one of my log data poits it read MAF 12225 not sure what thats for. BUt one oter log poits read MAF 58, guess thats the number i wanted.
only 58 i want more!</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">58 lbs/min? not too bad. thats 438.4 g/sec

oh I just figured it out its your maf frequency raw data in Hz, I think that is the limit of the maf dude! hehe

<small>[ October 19, 2002, 02:11 PM: Message edited by: Nickn20 ]</small>

SJH

yeah right around 10hp per lb/min is your theoretical Hp at the crank.It will be a good guesstimate. You could make less hp than you think though and show good airflow numbers if your tune is way off.
If you want to get technical, usually for a well tuned motor it's around 9.45 lbs/min at the HP peak and 10.58 lbs/min at the Torque peak. That's why most guys split the difference and just use 10lbs/min.

44lbs/min is a bit low for a 5psi motor. I see more than that at 4500 rpm but that's with a 11psi top end.
Right now I am peaking at 63.2lbs/min. When I ran only 5psi I saw around 49-50lbs/min with a stock ls1.
Now that's a blower motor. Rev it up and the blower spins. Even if you kill off timing and totally goof on your fueling, you still have the airflow available. Although you could very well make a lot less power.

We spent a lot of time in getting the maf to report as it should on my motor.
You can verify how good your calibration is by using a wideband and looking at your commanded A-F ratio and seeing how close they match.
Then tweak the maf curve until they are very close.
Mine is about .1 to .2 points from matching a wideband.
I error on the side of rich.
Once you get this right, you won't need to run to a dyno everytime you make changes.
The MAF is extremely critical.
It had better be calibrated properly if you ever expect to have a good running motor.
Steve

ChevyNo1

OK, I made a couple of runs this morning . . . I'm still only seeing peak of 46 for the MAF. I've disconnected the Stage II computer to rule that out, so something is still not right. Can someone take a look at those logs? You can find them at:

1st Run
2nd Run

- Dug

<small>[ October 20, 2002, 01:10 PM: Message edited by: ChevyNo1 ]</small>

SJH

are you not a bit concerned about all that knock retard you are showing? <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> Geez I would be taking that VERY seriously.
Because if the engine is in any sort of detonation of course you'll be way down on power.

O2's also look to lean IMO.