Fire67

iTrader: (3)

I know alot of you LS1 guys are blowing through your MAF... My LT1 has always been run with the Procharger sucking through it. For the new motor I have several reasons why I would like to blow through the MAF, mostly for plumbing and packaging. But its not a neccessary step, I could go either way at this point.
My questions:
-Is there one way that is more stock PCM friendly than the other?
-Are there any tuning issues that come up when blowing through the MAF?
Aside from the fact that the MAF will max out at a relatively low boost level.
-Anyone have any problems when switching from a suck-through configuration to a blow-through?

2001WS6Vert

I picked up 2 lbs. boost going from suck to blow. Also better overall driveability.

white2001s10

iTrader: (4)

This reminds me of 'mega-maid' from Spaceballs.

Fire67

iTrader: (3)

2001 WS6vert - 2lbs and better driveability? Sounds good, but why did moving the MAF downstream of the blower get you better driveability?

white2001s10 - Spaceballs??? Damn, I almost forgot about mega-maid!

jyeager

If you will be using any type of intercooling then the distance between the MAF and the engine is great enough to cause driveability or mixture problems because the MAF sees a certain airflow long enough before it hits the motor.

I'm in favor of blowing through the MAF.

MIGHTYMOUSE

iTrader: (59)

"SUCK...SUCK...SUCK...SUCK"

ive run both i prefer blow thru.

Frost

iTrader: (45)

What has mega-maid done?

Fire67

iTrader: (3)

Thanks a bunch, thats exactly the kind of information I was looking for. Im running the procharger twin intercooler setup for LT1's, so yeah, theres ALOT of plumbing between the intake of the blower and the TB.
Could this be why the RPMs always seemed to hang when I would take it out of gear and coast(with the stock motor?)

Fire67

iTrader: (3)

She went from suck to blow! It's looking like my TA will be doing the same.
LMFAO!!!!!

jyeager

No the rpms hang like that by design. The computer keeps the idle up. Not exactly sure why, but it might be to help with driveability. Keeping the idle up during a slower shift will result in less reverse drivetrain stresses I suppose.

Fire67

iTrader: (3)

Well I dont think thats it. With the stock motor it would fall from whatever rpm I was at then start hanging at like 2K rpms... It all started when I installed the procharger and the M6 trans. We eventually got it to stop doing it most of the time with programming.
This time we'll be starting with a clean GM program for a M6 car, instead of my program for an A4 car that we made "work" for the manual trans. Then hopefully we wont have any programming related issues.
Is there any difference in the PCM calibrations if your blowing through instead of sucking through the MAF?

jyeager

Not that I'm aware of. The problem with the draw through MAF is simply that when you transition, the MAF doesn't reflect what's going on in the engine. Since you can't overcome that problem, it can't be said that you do something different, in that you had one approach for the draw through configuration and a different one for the blow through.

Now that being said, every 'tuning' effort is an effort to correlate the MAF reading with the actual air flow (via the feedback from a wide-band O2), but this isn't anything specific to a blow through system, it's always true for tuning with a MAF.

If you are asking if there will be a difference in the MAF readings vs. actual air flow between the two configurations I wouldn't be one bit surprised. So you simply need to go through the exercise of tuning like normal.

KAOS

iTrader: (5)

i had idle issues with pulling through the maf

Fire67

iTrader: (3)

Thanks for the input guys. I imagined it would read the airflow differently because the air it sees in a blow through config would be hotter... And the MAF reads airflow by how much the filaments get cooled down by the passing air.
The reason I asked is that Im just starting to learn LT1edit. I will be paying a professional to make a base tune for the new motor during break in and also to dyno tune it when all broken in. I just bought LT1edit, and will soon be buying data logging software and a wideband so I can keep tabs on things while I "tinker".
<------ I cant wait to be doing this again

jyeager

In theory the hotter air isn't as big an issue as you might think. That, in conjunction with the input from the intake air temp sensor allows the actual air flow to be determined, more or less, despite temp changes.
But I think that overall you are still right. In the 2 different places, the MAF is bound to see a somewhat different reading.

2001WS6Vert

It virtually eliminated a surge I would get when I let off the gas cruising on the highway (which was very annoying), the car also runs better when first started cold. The power gain was the big benefit. I would assume it's because your restricting airflow a lot more when you put a 75mm MAF in front of a 3 1/2" blower inlet vs after a 2 3/4 outlet.

Fire67

iTrader: (3)

Ah I see.. Well Im definitely gonna go "blow thru" when I put this thing back together.
Thanks again for all the input guys.
I have almost all parts for this project together... So maybe by the middle or end of next month I'll have some good dyno numbers to share.