Whats up guys.....I have a question....

I keep reading that the Comptech aftercooler makes you LOSE boost. Now can someone explain to me why when I buy a supercharger, I want this...???

 

you lose boost pressure because the aftercooler cools down the hot, compressed charge. cold air is more dense, takes up less space, so lower PSI pressure.

hot charge means ECU starts adjusting timing to compensate and you lose power

cool charge means more power.

if you want bragging rights about PSI, you can go to a smaller pulley to make up for the loss of boost and still be ok up to the point that you get too hot again and ECU corrects or you blow the engine.....

you can never just look at a single item, add here robs there, it is all about compromise.


keith

 

Ok so the boost lost on a Water/Air aftercooler tends to be about 0.5psi not a whole lot....

One other point.....more heat increased risk of detonation..
Aftercoolers provide greater protection against detonation than non.

That said centrifugal SC's are the most thermally efficiecnt chargers around, so they raise temps less than roots or screw types. You don't have to have one but it is a good insurance policy especially on HOT days...

Also Comptech has said for a while about introducing a high boost pully kit, the aftercooler would be required for that.

 

I believe that .5lbs to be correct from what I hear.

Here is my question.

Do you lose that .5lbs due to headloss through the aftercooler or do you lose that .5lbs due to boyles ideal gas law (ie. Pv=nrT).

Since the gas is not in a closed system at rest, I don't think ideal gas law applies (and yes, I understand common air is not an ideal gas anyway but closely approximates depending on moisture content).

If that above is correct . .. .. KAMcDonald, I think your explanation isn't quite right. Not trying to flame you just trying to understand. I know from many of the Mid-A guys you are a great guy so please . . . . no offense.


RoadRage, where is my engineering minded buddy to settle this??

 

Thanks guys, Just wanted to understand.

 

[QUOTE]Originally posted by ACLR8
I believe that .5lbs to be correct from what I hear.

Here is my question.

Do you lose that .5lbs due to headloss through the aftercooler or do you lose that .5lbs due to boyles ideal gas law (ie.

 

When you add an intercooler, you are adding VOLUME to the system. It takes more boost to compress a larger volume to the same pressure. And an air/air intercooler is even a larger volume.

 

This may help:
http://www.stealth316.com/2-adiabat1.htm

I believe Boyle's law plays here. But the exact amount of the loss in boost is constantly changing, based on ambient air temp, air velocity through the intercooler, and a bunch of other little gremlins. The point is you have to figure things out for the entire system, and then fiddle with the formula variables until the best "compromise" is reached. This has to be done in league with air/fuel enrichment and spark timing maps. You will need a good table of air density to pressure conversion tables.

I really do not have time tonight to give the ol professor's rehash, but there certainly is some pressure loss, in the Cobras we generally see 1-2 PSI, which is easily offset by a pulley size reduction that does not exceed either the maximum rated speed of the supercharger or produce temps beyond what the IC can cool. Ford has developed a really cool system that will show up on a fuiture Lightning and the 2006 SVT Cobra: they divert some supercooled coolant through the IC to allow supermax boost to be sustained for about 15 seconds.

Given that the S2000 is proportionally smaller, a .75-1.0 PSI loss is to be expected. But you guys are nitpicking the real benefit overall of the IC, which is to allow higher boost with reduced risk of detonation. Gnerally, as long as the boost exceeds 6 PSI or so, concern of IC efficiency (boost loss) is not a real issue, given the benefits. A standard boost of 10-12 PSI in a pulleyed Cobra would produce a thermal result that would boil water!

The simplest way to measure the IC's efficiency is simply to measure the PSI at the outlet of the IC, the PSI at the input, multiply x 100 and there is your intercooler efficiency.

What is the boost on an S200 system?

 

I believe it is a combination of the increased volume, restriction, and Boyle's Law. In the case of the AW coolers I expect that the first two are minimal. The air path isn't greatly longer and although the heat exchanger has a greater volume and some restriction due to the element it's minimal compared to an AA.

But the fact is, you cool a gas, it will exert less pressure. There will still be the same amount of air present it will just be denser and exert less pressure. As both these kits use boost pressure to up fuel the A/F will be leaner. How much and whether or not this is a consideration I don't know.

 

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Diehards only.