Draw thru MAF for turbo

[malice10985]

I finished my turbo kit a few weeks ago. Blah blah blah hooray for me.

I remember reading a really long thread here about MAF tuning and blow thru vs draw thru.

My blow thru setup was working great, but deep down I didn't trust it, so I converted to a draw thru system with an LT1 MAF.

I haven't programmed the PCM for the new MAF yet, so the car runs funny.

Can someone get me an unaltered, unbiased, stone stock MAF table for a 94-97 F-BODY? (not corvette) I would like it in excell format.

Once I get the file, I will study how the different tunes affect engine performance and report back with my findings.

[mrbako]

i'm interested to see the results you get w/ this setup...but here's my opinion

don't worry about blowing through the MAF....it will work fine. btw, why don't you trust it?

there will be no benefit to drawing through, just a bunch of headaches. i've posted on this before and i don't know why ppl won't listen. you will need to recirc, or buy more electronics to compensate for an atmospheric blowoff. there is no way to compensate within the ecu, no matter which software you buy. when u blow off you will run too rich and choke the motor w/ fuel.

EDIT:-----------------------------

i would recommend to anyone with FI to NOT use the stock maf meter, which is just a sampling meter.

[ March 09, 2005, 10:06 PM: Message edited by: mrbako ]

[nocutt]

Originally posted by mrbako:
i'm interested to see the results you get w/ this setup...but here's my opinion

don't worry about blowing through the MAF....it will work fine

there will be no benefit to drawing through, just a bunch of headaches. i've posted on this before and i don't know why ppl won't listen. you will need to recirc, or buy more electronics to compensate for an atmospheric blowoff. there is no way to compensate within the ecu, no matter which software you buy. when u blow off you will run too rich and choke the motor w/ fuel.

I disagree...yes you can run a 'tru maf' blow thru. The pros are very good throttle response, you can blow-off into the atmosphere, you have less of a pressure drop when you start pushing +++HP...the cons, oil gets on the MAF no matter what (improper reading can ensue), if you pop the turbo chances are the parts can damage the MAF electronics, generally you tend to run rougher.
Draw thru pros, depends on how you look at it...a recirculated Blow-off actually helps the turbo in transient...meaning air it doesn't have to suck can help the unit keep spinning, generally idles better than a blow thru because air flow over MAF is less turbulent, oil from turbo unit never gets on MAF (less maintanance)...FOR EASE OF TUNNING AND DRIVABILITY SUCKing is the way to go...no pun intended
Cons...throttle reponse is slower than a blow-thru, when you get to +++hp it is much easier to blow thru

[malice10985]

OK, so I tried my new draw thru tonite. It was good... sorta.

The car pulled like a raped ape in prison. from a 15 roll, it broke my kuhmo tires loose in 1st gear and kept them loose all the way thru second. I hit 100 mph in less than a quarter mile. I know that is a bad way to judge power, but it's all I have right now.

ANyways, there were some down sides. It was super lean. I can't find an LT1 MAF table ( click me for $20!!!) so I just used an LS1 MAF table. It didn't like that I guess. My narrow band o2 readings were as low as 798. I think it was too lean for safety's sake. I didn't blow anything up, but I need to richen it up with the right table.

[mrbako]

the debate between which is better could go on forever... IMO leaving the system as a blow through w/ a LS1 style MAFS is easier, and more than sufficient.

[lord_gufi]

uhmm even on my dsm with the ls1 maf we use blow through setups. with my car when i tryed pull through i got ****ty ****TY idle problems. went to blow through and ive yet to have a problem. just make sure you leave the honey combs in, if you dont the maf will get impropoer readings from the mass amount of turbulent air in the system.

[nocutt]

MOST FACTORY TURBO CARS IF THEY USE MAF...will use it in a draw thru config...it isn't a big deal...it is just easier to tune that way and idle better than a blow thru setup...
IF you put a brick on the throttle the engine will care less how it needs to be read...most of the issues with each setups is off-boost and during transient operations...

whatever your engine was exhibiting is one problem with a draw-thru design...NO LEAKS AFTER THE hairdrier...absolutely none!!...because that air has been metered [img]graemlins/wavey.gif[/img]

[malice10985]

UPdate:

So far you blow thru guys are winning. The car idles like ****.

It also stalls when ever I shift under boost. The BOV lets out all that boosted air, and the fuel system is still dumping fuel into the cylinders. It drowns itself in fuel.

I haven't given up yet. I have some "secret" tricks up my sleeve to fix this problem. If they don't work, I will go back to blow thru.

[RedFrk13]

Your BOV needs to recirculate the air in a draw-through system.

[nocutt]

Originally posted by malice10985:
UPdate:

So far you blow thru guys are winning. The car idles like ****.

It also stalls when ever I shift under boost. The BOV lets out all that boosted air, and the fuel system is still dumping fuel into the cylinders. It drowns itself in fuel.

I haven't given up yet. I have some "secret" tricks up my sleeve to fix this problem. If they don't work, I will go back to blow thru.

There is no secret and no trick...if you are sucking thru the meter...you cannot have any 'UNCALIBRATED' leak...post turbo...pre throttlebody...

[Teufel Hunden]

Originally posted by malice10985:

The BOV lets out all that boosted air, and the fuel system is still dumping fuel into the cylinders. It drowns itself in fuel.

You need to recirculate the air back into the system. i.e. a bypass valve as opposed to a blow off valve. Like Nocutt said, you can't have any air escape after the mass air, because it has already been metered, which means fuel has been added for it.