IC Piping: Efficient to inefficient...

Nor'Easter

Nor'Easter

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I'm curious for those who have experience with flow rates...

How do you calculate the optimum size for intercooler piping? I know there is a point at which the piping gets so small that it starts reducing the efficiency of the turbo as it now needs to work to push the air through the piping rather than just compress it. I also figure there is a volume size inside the piping that, if very large, starts increasing the time it takes for the turbo to build boost, thus increasing the time that it takes for the engine to receive said air.

I saw a build at SEMA where the IC piping to the intercooler was about 3-4', and then another 3-4' back to the charger.

Any input? Looking for a little more specific than "This ID for s300 chargers". More like, "The map of the compressor dictates the sizing by..." Merely interested, do not have an actual application for such specific knowledge.
 
There is a chart I have found somewhere of what straight pipe flows cfm wise. Then figure flow losses, like bends, and such, Then you figure cfm to hp rating. Boost and temp change things, but I don't know how much.
If I did my math right, 3 inch pipe is good for around 900 hp. Some guys like to use smaller diameter pipe between turbo and ic, and larger between ic and intake, hot "loose" air depends on velocity of smaller pipes to get it to ic, then cooler "thick" air uses larger pipe for mass flow. Its a theory that small gas turbo engines have proven on the dyno.
 
I did a experiment with my IC pipe.
The ID of my pipe coming from IC was 1.700.
I cut pipe off, opened IC hole to 3.100, I bored new
pipe 3.100 tapered down to 2.500 going to turbo.
I opened it up before going into turbo. My theory was more
air at greater pressure. I don,t know if it did anything or not.
 
Nor'Easter said:
I'm curious for those who have experience with flow rates...

How do you calculate the optimum size for intercooler piping? I know there is a point at which the piping gets so small that it starts reducing the efficiency of the turbo as it now needs to work to push the air through the piping rather than just compress it. I also figure there is a volume size inside the piping that, if very large, starts increasing the time it takes for the turbo to build boost, thus increasing the time that it takes for the engine to receive said air.

I saw a build at SEMA where the IC piping to the intercooler was about 3-4', and then another 3-4' back to the charger.

Any input? Looking for a little more specific than "This ID for s300 chargers". More like, "The map of the compressor dictates the sizing by..." Merely interested, do not have an actual application for such specific knowledge.
Click to expand...


I'll suggest a better way of thinking about this.

The piping coming off the turbo, assuming it is of reasonable size (not 1/2" NPT, LOL) does NOT affect the efficiency of the compressor in any way at all. It just acts like a restriction in the system that causes a pressure loss that you can never get back.

If the pressure loss is significant, the result is lower mass flow through the entire system (on the compressor map it moves the operating point horizontally to the left). That can either increase or decrease efficiency depending on where you're at on the map to start with.

If you add fuel to the engine, or reduce turbine A/R to try and overcome the pressure loss and get back to the same manifold pressure, then you're spinning the wheel faster, and that typically pushes the compressor outlet temps higher (again it depends on where you are on the map). The final effect of that depends on how the intercooling components are configured. On a big water to air unit, it could mean practically zero. On a smallish air-air, it might be significant.

I think we agree on the overall result but sometimes the wording is important to the understanding.
 
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On my triple GTX4508 build I measured a pretty healthy pressure drop across the IC.

Changed the inlet and outlet to the intercooler to 3.5 inch rather than less than 3" due to the thick casting and netted 50 RWHP on that alone.
 
All the testing that you all have done, is that with a stock head or one that has been worked over?
 
Hell I don't know. I have looked at this one before, as well as another that was more helpful, which I cannot find at the moment.
 
in Corky Bell's book "Maximum Boost" he talks about fluid flow in piping and that the velocity should ideally remain under the Mach .4 number.

The mach number is the relationship of the fluid flow speed to the speed of sound.


Problem is that the speed of sound and fluid flow are greatly effected by temperature and pressure.

Thats is more math than my brain can comprehend atm.


Some light reading:

http://www.pipeflowcalculations.com/pipe-valve-fitting-flow/flow-in-pipes.php

http://www.aft.com/documents/AFT-CE-Gasflow-Reprint.pdf

http://www.engineeringtoolbox.com/mach-number-d_581.html
 
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