I was thinking about this as well. Wouldnt a "Pressure washer" be a good analogy here? You hook it up to your outside hose bib, which generally has about 40psi. Yet when you squeeze the trigger your getting a blast of water much greater than the input of the garden hose. You have no more water going into the machine, it just takes what is goes in and forces it out at a higher velocity. Could be wrong here, but it sounds good.

 

Pressure Washer - well sort of. The difference is that the compressor actually creates a vacuum and sucks more air into itself which it can then compress and put out to the engine. The engine gets more air than it would be able to draw in NA. In order for more air to be available the compressor must draw more air in than the pistons can on their own. Boost is really a measure of resistance. The compressor draws in air and tries to force it into the engine. The intake manifold and heads can only flow so much and the pistons can only suck so much so the air backs up and creates pressure inside the intake manifold. Meanwhile it is pushing all the air it can into the combustion chambers controlled by the wastegate. No air is lost once it enters the compressor (or at least it shouldn't be lost) so it does not matter if you mount the MAF before or after the compressor from that point of view. The MAF will see the same amount of air being sucked through it if mounted in front of the compressor as it will see being forced through it if mounted after the compressor.

What does change is the heat in the air generated as a by-product of the operation of the compressor or compressor/IC combination. The action of the compressor trying to force the air into the engine creates heat. Hot air contains less air molecules than colder air and the MAF will try to adjust its readings to account for the heat in the air if you put it after the compressor. The actual A/F ratio will need to be measured by a wideband O2 and the tune adjusted to take this into account. Whenever you change the location of the MAF from before the compressor to after the compressor or visa versa the A/F ratio should be checked and the tune adjusted for any changes.

In general most positive displacement and centrifugal superchargers run the MAF in the stockish position and measure air being pulled through the MAF. Most turbos (well at least the STS ones) run the MAF after the compressor and measure the air after it is compressed.

 

okay, got it. I kept my MAF in the stock location and installed the open air IAT sensor in the elbow just before it dumps into the manifold. This way it reads the compressed air but after the intercooler.

 

Whippled 496- Good analogy! That's exactly how I figured the chareger was working....guess not. But good one just the same!!

Mort- Thanks for the detailed explination, I was begining to go nuts with this...as I am nuts enough already, this was making my head hurt

So, MikeGyver- now you know Get the tune set up for it and it should work right for you.....

 

Ok, I've got the pressure washer mounted, I just have to figure out what size pulley to use. Do you guys think I should mount the nozzle before or after the intercooler?

 

300rwhp?

 

400, with the pressure washer.

 

 

I wonder if that would be considered water injection?

 

Man, you guys F'in kill me. Mike make sure to use nothing less than a 2200psi. Using the formula 1psi = 20rwhp....that should net you someplace around 44,000rwhp. In a 6000lb truck that should put you across the 1/4 mile mark in just under 3 seconds @ 455mph.