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Model specific boards => Golf mk4 => Topic started by: Starry on 05 April 2004, 20:20

Title: intercooler tube size
Post by: Starry on 05 April 2004, 20:20

what are the pro's and cons of the size of tube you use on your intercooler. i am using 2"/51mm tube on my fmic at the mo and was wondering what ,if any the benifits of running larger tube would be. i am running revo/turbo back mitek and my figures are 199bhp/237lbs..

Title: Re:intercooler tube size
Post by: nrgizerbunny on 05 April 2004, 22:07

bigger pipe allows two things to happen.

first of all you can have more mass flow (ie. more mass of air). note MASS there, you could get the same amount of air through the smaller pipe but you would need to compress it.

next you get less friction (pressure) losses because the same amount of air can travel slower. and as pipe losses are proportional to speed you will gain largely there.

i can't think of any downsides other than size and it is possible that the pressure ratio could mess up. there is a bigger volume in the bigger pipe so you need more work out the turbine to get the same pressure ratio if that makes sense.  ;D

hope this helps

have a nice day

sanj

Title: Re:intercooler tube size
Post by: Starry on 06 April 2004, 08:42

thanks Sanj.
as i said i am running 2"/51mm tube do you think this is an ok size for the car/setup i am running. as i dont want to restrict the air flow to my turbo.. i know by running a fmic i will be getting nice cool air without heatsoak but will i get enough, or is this to hard to work out. thanks for any help.. ???

Title: Re:intercooler tube size
Post by: nrgizerbunny on 06 April 2004, 15:46

starry are you running a garret turbo or different one? if you are do you know what the pressure ratio is (i know this varies but a rough guesstimate would be okay)? if you do i can work it out for your worst case and best case scenario

have a nice day

sanj

Title: Re:intercooler tube size
Post by: Starry on 06 April 2004, 16:35

just running a bog standard k03 at the moment till i save up some pennys. but i dont know pressure ratio is on that.

Title: Re:intercooler tube size
Post by: nrgizerbunny on 06 April 2004, 23:55

starry i'll see if i can find the spec. alternately do you know what the mass flow is? if not my haynes manual will hopefully have it in.

have a nice day

sanj

Title: Re:intercooler tube size
Post by: nrgizerbunny on 08 April 2004, 22:24

hi starry,

i did a quick calcualtion based purely on theory and worked out that the maximum performance gain you can get by using a bigger pipe would be about 2-3%(best case) for 3" pipe. the restrictive element is the inlet to the turbo, which you can;'t change. the gains you get from using a bigger pipe are purely from reduced pipe friction losses (the gas rubbing against the pipe surface)

the only other thing i could suggest but its based purely on a guess, is that it could be worse. reason is because you have a big pipe going to a small inlet on the turbo, in order to make the air get through the small gap you end up making it hotter (not by much) but worse still the airflow may become turbulent rather than laminar, so the compressor doesn't work as efficiently.

so to cut a long story short, i would say your okay.

have a nice day

sanj

Title: Re:intercooler tube size
Post by: Starry on 10 April 2004, 10:04

thanks sanj it looks like im ok then. thanks for the advice.
Starry