Intercooler piping

[VWTUNING]

I was originally planning on running all my IC tubing 2.25" but I screwed up and when i ordered the second U-bend I ordered a 2.5" by accident. Do you think there will be any benefit (or opposite) to running the 'cold' side of the IC at 2.5"? My initial thinking is that after the IC the air will be cooler and expand, so a little bigger tubing might not be a bad thing. But at the same time that is simply more space that needs to be filled and therefor will increase lag.

For reference, turbo outlet is 2" - IC has 2.25" inlet and outlet - Throttle body is 3" (I believe, its a VR TB).


Any input / oppinon is appreciated. Thanks

[boostin20v]

You'll be fine. When I was polling for answers on doing 2.5 vs 2.75 I had some tell me to do 2.5hot/3 cold.

[lotar_6]

I know nothing about your piping size, but isn't cold air more dense? In other words, doesn't it contract, not expand? :confused:

[B4passatglx]

I am running all 2.5 inch intercooler piping from the turbo to the throttle body. My intercooler however is 3" inlet and outlet but I have silicon reducers there. I got a pic. On a VRT I'd say 2.5 is ideal since the throttle body is 3". Let me know if you need some bends in 2.5, I have boxes full of mandrel U bends and 90 bends that I havent used. I also got a lot of straight pipe and lots of couplers and T bolt clamps.

I also have a 2" to 2.5" reducer that I am not using for the turbo since I have a 2 to 2.5 90 bend

Here's my 2.5 setup
http://i4.photobucket.com/albums/y114/jressman/VRT008.jpg
http://i4.photobucket.com/albums/y114/jressman/VRT010.jpg

[Nuksucow]

2.5" will be good, but my only concern would be that the intercooler is 2.25". I think this might screw up the flow a little since it will neck down into the intercooler and then go back up to 2.5". Its probably not a big deal for your power level but still something to consider, you could always make the intercooler inlets larger to have a nice straight air flow.

[USOPHUNKE]

when I ran my stuff I was told the same smaller before the intercooler bigger after and to try to keep the bigger right to the intake if possible. which is why someday I wanna do a mustang t.b. I dont think with the size of your turbo it could have any negative effect, if anything it prob will be good.

[Shiftn4Dubs]

I know nothing about your piping size, but isn't cold air more dense? In other words, doesn't it contract, not expand?


Hmmm? I guess you could think of putting water in an icecube tray or rain droplets that get bigger and expand into icecubes, snowflakes, and hail when it gets colder. Density= Mass

When I was polling for answers on doing 2.5 vs 2.75 I had some tell me to do 2.5hot/3 cold.

You would think this also helps with flow, not sure though, you could get a better flow the other way, or even sized tubes could be better.

I like this idea...http://en.wikipedia.org/wiki/De_laval_nozzle

http://upload.wikimedia.org/wikipedia/commons/thumb/1/1d/De_laval_nozzle.svg/250px-De_laval_nozzle.svg.png
Diagram of a de Laval nozzle, showing approximate flow velocity increasing from green to red in the direction of flow

Not sure if this would apply to air flow also though.

I tried testing this on the GTI last week, I cut a soda bottle in half and placed in the Air intake tube after the filter with the top of the bottle facing the TB(was an exact fit) and taped it up on the end with electrical tape and put it back together, but the vacuum kept pulling it off the tape and sucked it into the bend of the tube and caused a blockage, still ran but couldnt really tell if it made a difference, cause it kept ripping it off?

[boostin20v]

the flow velocity you've cited is all one temp. With intercooler piping it will be hotter pre IC and cooler post IC so the flow is different.

[evolveVW]

cold air is more dense. Air expands as it warms, with the molecules being spaced farther apart. Pressurization creates heat as a byproduct. I would think the purpose of larger piping after IC is to move more volume of cold dense air into the engine, but you should be fine Pete.

[lotar_6]

cold air is more dense. Air expands as it warms, with the molecules being spaced farther apart.

exactly what I was thinking...

Also explains why hot-air baloons fly!

[meatwad!!]

holy crap ! ryan posted pics of his car?!

[BUNNYLOVE]

Your 2.25 IC outlet would be stepping up to 2.5" so it won't cause a restriction. Stepping down wouldn't be good.

[RichB]

Becuase I am a enginerd...

PV=nRT describes the basic relationship (ideal gas law I think its called) of what you all have been talking about.

If temperature goes down on the right side of the equation and the Pressure is constant on the left side, the Volume of the gas has to go down to maintain equality.

[USOPHUNKE]

also air heats up when flowing through a restriction. so it wouldnt do you any good to go smaller. going bigger should be fine. dsm and supra and other cars have been running 2.75 to 3.5 for years with great results on cars with sim size engines and turbo's. I am a firm believer most vw people go to small and need to step it up a notch

[VWTUNING]

OK well I decided im gonna run

2" turbo out
2" to 2.25" adapter
2.25" pipe to intercooler
2.25" straight coupler to IC
2.25" to 2.5" adapter on IC outlet
2.5" pipe to TB
2.5" to 3" adapter for TB.

Down the road I imagine I'll upgrade the IC to some thing with 2.5" or 3" inlet/outlet and at that point I'll prolly upgrade piping to at least 2.5" all the way through.


Thanks for all the input guys. I got very excited laying out the IC piping and IC last night, cant wait to get a manifold made/bought :D

[boostin20v]

what IC are you using?? this a awic?

[VWTUNING]

yeppppers PWR core (4x6 I believe), not rated for more than ~300 but it will be a good start.