2.5" is the plan. as for T-body and intake I'll probably go stock for now. don't feel I have that much to gain, head beeing stock and all.

 

Ok, no probs.

 

Water injection is another way to increase the "effective size" of the intercooler.

 

Hmm that's an intersting way of phrasing it. I guess in actuality it's kind of true if you drop the temps then you are mimicking a larger i/c.

 

Well I dont think you can really say its effectively increasing the size of the IC. You dont have the pressure drop of a bigger IC, you dont have the possible increased lag, you DO get a steam cleaning type effect in the combustion chamber when you first use it. They even reduce charge tems in different ways. One through the conversion of water to steam and the other through cooling the charge air prior to the combustion chamber...

 

To some degree. Eventually you'll (generally speaking) reach a point where you are physically trying to flow a specific volume through a specific size hole, end tank etc and you simply have to increase the size of those parts to reduce restriction.

 

yeah but that point is well, miles away IMO, it has to be flowing less than the head will flow. I had a thread about intake design and boundary layer thickness influence when considering flow to the head on another forum but I didnt get much help.

 

True but, even if the IC out-flows the head, if it's still a bit too "small" for the intended airflow volume, you can still see gains in going with a larger IC by reducing IAT's as a result of less airflow restriction. You might not gain a significant amount of power but cooler IAT's is always a good thing. Air being forced through a smaller hole is generally going to result in hotter air, and vice versa. I've seen a few dynos around here of decent improvements made with stock IC end tank mods, as well as the SFR IC and LR stage 5, and as far as I can remember I don't believe any of those setups were with cars that had modded heads.

 

I think I worked out the power to temp relationship when I was datalogging the intake temps, cant recall exactly what it was but one degree was a reasonable fraction of one HP from memory. I was making 365WHP with a modded head and changing from the stock to the IC I posted gave zero HP, so I am a little dubious about changing the IC below that power level at least...

 

I think I've asked this question before (but one bounces around all these different sites it's hard to remember where you said what?), what about the fact that many turbo outlets are 2" and we're discussing going up to larger i/c pipes, possibly 3.25". Aren't we starting with a restriction from the word go?

 

I think the real issue with front mounts is that you are already increasing the pipe run... if you increase pipe size as well you better be sure that your turbo and setup will yield you some real benefits from the increased flow. Otherwise you are just creating greater volume that needs to be filled and will result in lag.

 

No, because its compressing the air. It not a closed loop system. All 3.25"IC pipes will do is increase the volume of the pipes (not the air consumed by the motor, which is just an air pump, it will only ever flow as much as the head will allow) and reduce air velocity.

 

True but we are not running a n/a motor. You are forcing the air (some people, 2-3 times as much as stock(ST 4x's)) through the head. Thats why the trend is to go bigger and bigger with the turbo. Because the head can't flow.

If you remove all restrictions, you wouldn't need such a large turbo. As far as the IC and IC pipes go. While you can force the air through a 2.5" pipe, it will not go without causing friction and heat. Temperature and pressure are directly related. A larger ID" will reduce those problems.

 

Hehe, you managed to post in 2 short paragraphs what I've been saying in multiple threads using thousands of words. God I need to learn how to be straight and to the point sometimes.

 

But the pressure in the IC pipes is the same regardless of the ID. In fact the turbine is spun faster to maintain that pressure in larger ID pipes as the volume is greater. Meaning more heat. Unless I am missing something here?