Ok, I did some reading here on the forums and came across some vague statements about this, thus I couldn't really come to a conclusion. My question is, simply put, where or not I can safely place my MAF sensor on the post-compressor piping (blow through setup I think it is called)? I know this can be an issue if it is not designed to be used like this, but for my future turbo application, it would make my life much easier if I didn't need to have it pre-compressor (sucked through? lol). Any help some of the more knowledgeable members can offer is greatly appreciated, so thanks greatly in advance.

 

Most people see the best results on a blow through setup versus the DRAW through lol. You may want to get some 3" piping for that section though so you dont out flow the MAF sensor depending on your power goal. From what I have heard, its much easier to tune on the blow through setup as well. Good luck.

 

That is exactly what I wanted to hear. Definitely a relief to hear that I can use the blow through setup. Right now I'm just concerned about getting this beast boosted to any extent, but I'll be sure to see about going 3" on the piping. Thanks for the tips.

 

draw through= before the compressor in the intake piping.
blow through = after the compressor, generally after the intercooler as well.

typically and almost always on this car on a blow through setup it is after the intercooler with 18 inches of the throttlebody. on a draw through setup it is always in the intake piping, just like with hahns kit.

blow through is easiest to do on our cars. draw through is next to impossible unless you recirculate the air like the hahn kit

 

Blow through after the intercooler is best. the MAF does not like it hot so dont put it before. Depending on the power you are going for though you may see if maxing out if you are running a lot of boost. In that case, going with a larger pipe like 3" will help

 

Hoping Bryan will step in here...

So how difficult would it be to tune a draw through setup if a recirc valve is being used?

Vise versa, what would the impact be running a blow through w/ that same recirc valve?

 

Bump for exposure...

 

as for tuning a recirc valve...it wont be nearly as difficult as tuning a car without one on a drawthrough setup....actually if i remember correctly hahn wasnt able to tune the draw through tune without one until he added the recirc vavle in....

your second question...im not really sure...to me it seems that wouldnt really have any adverse affect on the setup, seeing as im pretty sure the air gets recirculated back into the intake piping maybe? not sure...but in any case i would think it to be pointless

 

Pointless to run a blow through w/ a recirc or pointless to run a recirc?

 

pointless to run a recirc valve on a blowthrough setup

 

That's what I thought you meant...

 

BOV goes in hot side of piping(before the intercooler)
MAF goes in cold side of piping(after thei ntercooler)

where you position the BOV doesnt matter, the closer to the TB the better, the MAF i would say keep a good 6-12" away from the TB

 

For blow through, we have used the stock MAF in a 3" tube which worked well up to 350 WHP if I remember right. Beyond that we needed to go to a 3.5" tube which gave us a little more room. Eventually you would want to switch to a different MAF, but it really depends on your HP goals.

On a draw through setup with a lot of charge tubing and FMIC, the reason you need to re-circulate is pretty simple. Without a re-circulating bypass valve, you run into one of two issues.

1. With no valve at all, there is a lot of pressurized air that has nowhere to go when the throttle plate closes. Since the engine is taking in less air, there is very little exhaust so the turbo is not being driven anymore. Now the pressurized air in the charge tubing can easily slow down the turbo and come out backwards past the compressor wheel. Aside from possible damage to the turbo if it slows down too quickly, you also have a tuning issue. Air that has passed the MAF and now turns around and heads back out the wrong direction causes a lot of difficulty in keeping a consistent tune. Letting off the throttle will often cause stumbling or rough running.

2. With a valve that dumps to atmosphere, MAF readings are useless with the BOV open. The MAF will meter a LOT of air that does not ever make it to the engine and the fueling will be WAY too rich whenever you let off the throttle and the BOV opens.

With a re-circulating bypass valve, you can run a draw through with reasonable success. In this case, when the bypass valve opens, the turbo can continue to spin very fast while air travels in a short loop back into the inlet tube and through the turbo again.

Advantages to a properly set up draw through MAF is that you do not have to worry about hot air or excessive turbulence where the MAF is located. You can also mount the MAF in a large tube without transition couplers required since the turbo inlet is larger than the charge tubing.

Blow through MAFs have some advantages as well. On most cars, the MAF is near the throttle body. When adding a turbo, it's easiest to keep the MAF in the same area to avoid wiring modifications. They also allow the use of a BOV that dumps to atmosphere. As long as the valve is located prior to the MAF sensor and the MAF sensor is somewhat close to the throttle body, you can relieve pressure without causing false MAF readings.

On high boost applications, it helps to have the MAF sensor after the intercooler because it reduces turbulence and cools the air to a temperature range better suited for the MAF sensor to make accurate readings. It also reduces the amount of compressed air between the throttle plate and MAF sensor for less reverse flow when closing the throttle under boost.

 

blow through is definitely the way to go. I had a lot of problems with the draw through setup on my car. Switched it over to blow through, and well I'll let the vid in my sig do the rest of the talking.