20vT Boost pipework query

Hi Gents!

This is really more aimed for the chaps who are running custom 20vT's in their Mk1s.

Atm my car is alive and running well, however i have an issue with my K03 turbo, which i think is related to the boost pipework. I'm running a 2.5" boost pipework system which is probably too big for this small turbo. So firstly what size are you guys running in yours? I believe the original OEM pipework is 2.0".

The reasons i'm asking this is because, even though the turbo is holding boost through all the gears at approx 1.1bar - 16psi. The only gear i'm feeling any boost is 1st and 2nd gear, unless this is normal??  

when i was going to run a ko3s in my mk1 i was told to use 2.25 piping. i go for 2 inch on a ko3

cheers peterg60 - Ive also read this somewhere on forums. I think its due to the fact that the turbo has too put x ammount of air around, so by increasing the general size to 2.5" from 2.0" its finding an extra 25% more room, if that makes sense.

Not sure if the k03s (180hp) runs a different pipework size OEM becuase i think the turbo housings are the same as the k03 so i would expect this to be the same. I know Joe90k used 2.25" on his, but haven't asked him personally on how it feels when driving.

Perhaps if i installed a K03s turbo ( straight swap for the k03) it would run better, but even then the 2.5" would probably still be too big in diameter  :dontknow:

i run 57mm pipes on mine and it seems alright so far

Should be OK, first one I built I ran 50mm to the chargecooler and the 70mm from the chargecooler to the inlet with a 70-63 reduction right at the end, was quite a long piece of 70mm pipe too, prob best part of 1m long, this was with a K03.  There wasn't excessive lag either, was much better on its 2nd incarnation though when I ran a TT inlet and lost most of the 70mm pipe and also had a K03s.

Also going from 2" to 2.5" will give an increase of around 50% increase of airflow. (Pi*radius squared)

Cheers Gents. I think after reading plenty of posts on this. Running a 2.5" system is fine. I think if the car was completely standard then i could understand that an OEM setup is required.

As it has Filter, Remap, Exhaust, Forge 007 DV etc, i think a mapping off the car, would cure this problem.