Turbo Inlet Piping Size

dana · Post by **dana** » Mon Jun 22, 2015 8:10 am

I am working on the charge piping for my TDI swap into my 90 quattro.
There is a LOT of piping crammed in one area. .

I am running 2" piping to and from the intercooler, but i am wondering if i need to run something larger from the turbo inlet to the stock audi airbox. Seems like 2.5" would be good, however 2" fits so much better.

Would 2" be to small on a stock turbo (tuned with injectors) TDI?

dana · Post by **dana** » Tue Jun 23, 2015 8:12 am

well after some internet sleuthing, I found this. http://www.dkgoodrich.com/pipingsize.htm

I figured a diesel 1.9 with a turbo @85% VE will be about 500 cfm at 5000 rpm. I dont rev to 5000 ever, and im not even sure it can do it on a stock (tuned) ecu. According to my internet research, this should be fine with 2". My mk4 tdi with a tune stops making power above 3500 anyway. All the meat is from 2000-3100.

The packaging is way better, so I am going to try and see what happens. I will add a little velocity stack where the pipe stubs into the airbox.

audifreakjim · Post by **audifreakjim** » Tue Jun 23, 2015 11:55 pm

2" is plenty for that motor. I was surprised by how small my 3.0 tdi piping was, it looks like 2"

dana · Post by **dana** » Wed Jun 24, 2015 8:50 am

I agree, 2" will be fine. It looks kind of funny, we are used to seeing bigger is better on this kind of stuff. The problem is the airbox from the 7a that I want to retain faces backwards and has to so a full "s" turn to get to the turbo inlet. I cannot make that work with a 2.5" pipe without making it super ugly. The 2" bends do it just fine, and dont look half bad.

SEStone · Post by **SEStone** » Wed Jun 24, 2015 11:28 pm

The new 991 Turbo uses 2" intercooler plumbing and 1.25" exhaust primaries. It is fast as shit and ultra responsive. Little pipework is not a problem.

Sam

ringbearer · Post by **ringbearer** » Wed Jun 24, 2015 11:30 pm

Velocity!

dana · Post by **dana** » Thu Jun 25, 2015 12:49 pm

well, its built, 2" all the way. ill grab some pics when my paint comes in to cover my shatty welds. :lol:

dana · Post by **dana** » Mon Jun 29, 2015 8:00 am

My lovely ghetto-fabbed turbo feed pipe in 2"

cannibalizing plate from an old winch mount

cheapo motorcycle velocity stack

it ties into the factory tdi inlet pipe that I cut down with a 2" hump hose

DE80q · Post by **DE80q** » Mon Jun 29, 2015 9:13 am

Nicely done! Looks good and should function well!

my2000apb · Post by **my2000apb** » Fri Jul 03, 2015 9:12 am

fits pretty damn well

dana · Post by **dana** » Tue Jul 07, 2015 6:57 am

yes, 2" is sweet to work with. The piping has to do all kinds of twists and turns to fit with the intercooler mounted up high (out of snow bank impact range). The 2" stuff makes it easy to fit it all in there.

PRA4WX · Post by **PRA4WX** » Tue Jul 07, 2015 10:54 pm

Mines a mix o 2-1/4 and 2-1/5.