blu00rdstr

Has MAF draw-through been tried with an ATI setup? I've always wondered why the MAF is in a pressurized section, since it's a stock component designed for draw-through setup.

The BOV could be piped to discharge between MAF and blower to maintain airflow accuracy.

boblackhardtop

It will be, result coming up soon. :D

QuickSilver2002

I would not think that it would make much of a difference, except it not being able to see IAT on the newer MAFs. It will still have the same metering limitations.

It would be intresting to try it.

H82BFST

Has been done years ago. Not on a vette but fbody LS1.

It help my idle tremendously and ltrims were predictable because the PVC wasn't being bypassed like in the blow through setup.

QuickSilver2002

Please explain what you mean by "PVC being bypassed".

SR71

My carroll kit draws through the maf.it is a much better set up than a blow through.a draw through maf will have nice laminar airflow instead of the turbulence associated with the blow through.when you blow through....everything that the air passes through or over creates turbulence.when you draw through....the air flows much more smoothly around everything.hence more total airflow through the maf.why do you think the fans on the car pull the air through the radiator?...because a puller fan set up is 25% more efficient than a pusher set up.


[Modified by SR71, 2:23 PM 8/24/2003]

QuickSilver2002

I think you guys are missing the point.

Our MAFs cannot read any real boost in the upper RPMs (4-5psi is about the limit), so worrying about how smooth the airflow is under boost is pointless. The blow through is better for part throttle when the blow off valve is open and therefore is a better setup for a centrifugal in my opinion.

BrainDrain_dx

edit: must read all of original post before opening mouth



[Modified by BrainDrain_dx, 12:55 PM 8/24/2003]

H82BFST

1) I used a 85mm MAF when it cam out and electronically calibrated to 512gms..~ 68lbs of flow... that's a little bit more than enough for most stock 8-9psi systems. ;)

2) On the Fbody, the MAF was before the TB, but the fresh air PCV was rerouted to the inlet hat of the blower. Thus, you have UNMETERED PCV air getting into the system since it's BEFORE the MAF. The car's idle and part throttle were horrible (I'm sure it could of been tuned for this leak). I put the MAF before the blower and the PCV is once again in the loop. Idle cleaned right up, and part throttle was no different than N/A. I DO NOT KNOW HOW THE VETTE SYSTEM IS. Vortech kits are pull throughs.

For a blow through, your BYPASS VALVE can vent to air, the ATI kit vented back to pre blower so even in pull through config it was all good.

What's your reasoning for saying that a blow through is better for part throttle?

I guess vendors have to consider packaging and I guess it's easier and maybe cheaper not to relocate the MAF from it's current position.

Each his own..

Mike Morgan

Our Supercharger System is a draw through design. We've found that blow through affects the MAF calibration tremendously. I've done a lot of data logging of blow through and draw through and the there is a much more stable and accurate MAF signal when drawing. Also the calibration of the meter when blowing through it changes significantly. Air flow recordings can be as much as 20% higher than what it actually is.
In addition drawing through provides a much more stable idle and low flow quality. Also it allows you to maintain a closed system. Part of the problem with a blow through is the PCV system pulls unmetered air into the system. Also the maf is located in such a position that it is subject to oil contamination. The Bypass system vents to atmosphere which creates pressure fluctuations.
On a drawthrough system, the pcv air is after the MAF metering also it is not exposed to oil contamination. The bypass system is also routed back into the inlet after the MAF resulting in a more stable and quieter system.

We spent a lot of time on this developing our kit and even though it provides a more restricted inlet, having the MAF on the atmosphere side has way more pluses and the restrictions are pretty much negligible unless you are pushing 600+ RWHP and at that point it helps reduce the tendency of a centrifugal of making too much boost near redline.

SleepieAce

Mike,

Does the draw through MAF come as part of the single intercooler kit, or can I just get a MAF relocation kit separately? :lurk:

Mike Morgan

Unfortunately, it's a bit more involved. The inlet on the Procharger kit is right against the radiator. Our FMIC upgrade kit puts the inlet in the passenger fenderwell. I'm sure with some creative fabbing you could setup a new inlet to attach a MAF, but I'm not sure what it would involve.

blu00rdstr

Theoretically if you have a laid-down radiator already, you could move the MAF to the right a foot and put a pipe in where the MAF was.

I suspect retuning would be involved as well.

boblackhardtop

Mike, I got your SIC & bracket setup, 8ribs, w/ a D1SC head running 12+lbs boost (3.7 pulley) it's currently getting tuned. I'm hoping for 650+rwhp, your comment above kinda concern me. Do you have a bigger intake in the works ? BO.

QuickSilver2002

I'm still confused by this
I don't see how the PCV could be pulling in new air that was not metered. I guess I don't understand it very well, but I always thought that air had already been metered once.

SleepieAce

Thanks for the answer Mike. :thumbs: It's no problem, I was planning on going with a single intercooler package and a D-S1C head eventually. I'm just saving up cash for a forged motor first. I was just curious if this was a mod I could do while I waited. :cheers:

Mike Morgan

The fresh air source that normally goes to the TB is moved to the inlet of the blower to prevent pressurization. But on blowthrough it is before the MAF so any air being sucked into the crankcase for ventilation is unmetered this air is inevetibly sucked into the engine through the PCV valve thus creating a vacuum leak.

Mike Morgan

We just made 640 RWHP 575 RWTQ on a 346 CI w/ a 3.85 pulley with the same inlet. The 3.70" pulley should be worth another 1-2 psi and 15-25 HP.

Sean@OCCorvette

Mike, Very impressive numbers . My Z06 is at Andy's right and will be over at your place in the next day or two. Hope you can get similar results with mine. It should have your SIC kit on it by now. Additionally Andy installed the LG Long Tubes on it, that should be worth something.






[Modified by MXRACER, 1:04 AM 8/28/2003]

boblackhardtop

Mike, I got your SIC & bracket setup, 8ribs, w/ a D1SC head running 12+lbs boost (3.7 pulley) it's currently getting tuned. I'm hoping for 650+rwhp, your comment above kinda concern me. Do you have a bigger intake in the works ? BO.

We just made 640 RWHP 575 RWTQ on a 346 CI w/ a 3.85 pulley with the same inlet. The 3.70" pulley should be worth another 1-2 psi and 15-25 HP.[/QUOTE]

Mike,
I was hoping to get some numbers tonight but having lots of problem w/ your bracket. Holes/mounting pattern does not match SC, have to grind to make it fit. Also found out for the first time you have to cut tab on water pump cover to clear idler pulley. After the bracket is on the pulleys is out of alignment. etc.. I told the shop doing the install to call you guys for tech. help. I wish you have instruction manual to go w/ these kit. Saves lotsa time & money...