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Discussion Starter #1
so i'm on the last pieces of my build and it's the cooler piping. i did some searching and can't find a straight answer...

most people will run a 2.5" piping from turbo to cooler to tb. this is good etc if you're aiming for high hp setup round 300 whp etc, but on lower/smaller boost setup this will decrease performance to slowerish spool etc.

i'm aiming for 300 ish and should probably go with 2.5", but i was talking to a friend and he says i should go with 2.5" from turbo to cooler, then 2" cooler to tb because the air denizens inside the cooler. this makes sense, but idk if this is a proven fact that would help me spool faster or any kind of gains.

any input?

probably gonna run it my friends way because i only have the right amount for his way lol.
 

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2.5 is pretty much the standard for piping. The air is dense regardless, it is charged. It will be chilled after it passes through the cooler, the different in spool time is going to be very small. You can improve spool by making the shortest possible paths of intercooler piping.
 

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I matched my turbo outlet pipe size (2" IIRC) from the turbo to the intercooler, and then matched the throttle body size (2.5" IIRC) from the intercooler to the throttle body.
 

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you will never notice the difference between 2" and 2.5" in lag time ....2" at higher hp levels could cause some restriction issues though....2.5 it and call it a day
 

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Discussion Starter #5
2.5 is pretty much the standard for piping. The air is dense regardless, it is charged. It will be chilled after it passes through the cooler, the different in spool time is going to be very small. You can improve spool by making the shortest possible paths of intercooler piping.
good point. i'll probably just keep the piping how it is and see if i can source out some 2.5 cold side piping.

thanks guys
 

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2.5 inch all the way unless you have a backdoor intercooler then its probably 2.0 from turbo to intercooler,
 

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go with what fits your budget. the piping size doesnt really do much.

like others stated, 2.5 is just fine. off boost, the small piping can keep intake velocity up for a bit of low end torque, and still allow plenty of pressurized air into your power hungry motor
 

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You want the smallest pipe that will keep the air flow under 304mph. At 304mph air speed you get restriction. I'm running 2" pipe from the turbo to the throttle body.
 

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^ interesting

its pretty easy to find velocity if you know how much air the engine is breathing, which can be estimated pretty easily by RPM and engine size plus a few other factors.
 

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^ interesting

its pretty easy to find velocity if you know how much air the engine is breathing, which can be estimated pretty easily by RPM and engine size plus a few other factors.
But not with a turbo?
Displacement + RPM will tell us how much the engine can "swallow" in a minute, but don't we need (guestimated based on IAT and poweroutput) CFM from the turbo to figure out the rest?
 

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You want the smallest pipe that will keep the air flow under 304mph. At 304mph air speed you get restriction. I'm running 2" pipe from the turbo to the throttle body.
304MPH where in the tubing? (Just something to think about)
 

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But not with a turbo?
Displacement + RPM will tell us how much the engine can "swallow" in a minute, but don't we need (guestimated based on IAT and poweroutput) CFM from the turbo to figure out the rest?
who knows im not an engineer i just use my best estimate and try it. if it works it works if it doesnt ill try something else.

so far, ive been pretty lucky.

304MPH where in the tubing? (Just something to think about)
velocity is highest in the very center of the tube is it not? but friction would occur on the outermost edge of the tube, i assume...??

hm
 

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2 and 1/2" or 2"... With your power goals, it will not matter. Although I would not go Amy bigger that 2.5" unless you are using a bigger setup an making more power.
 

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You want the smallest pipe that will keep the air flow under 304mph. At 304mph air speed you get restriction. I'm running 2" pipe from the turbo to the throttle body.
Where are you getting 304mph? Restriction isn't binary; it increases (approximately) with the square of velocity. There isn't an inflection point or anything at 304 mph. There is, however, and asymptote at the speed of sound.
 
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