Anyone any ideas what the power difference (peak power) is between a 54mm (Manifold and Up-pipe) and a 60mm Up-pipe and Manifold (both up-pipes narrow to 51mm at the Turbo.............)

 

with my limited knowledge I would say the larger diameter would give less mid-range but more high rpm power than the other..

 

Yes thats what I know........... the spool up will be slower but once going with more gas flow top end power should be more....... but will it be given that at the top of the up-pipe it restricts to 51mm?

I was wondering if anyone could quantify the likely differences - if its less than 10bhp then I'm not too concerned - but more than this and I will be

 

I think they both have to narrow to 51mm at the turbo to line up with the turbo inlet.. so the reduction will not effect the result as they all have too do this.

One thing you should do it match the ports on the new headers to the gaskets and port them to aid flow, and use a good heat wrap on them again to try and increase the flow.

I think Gruppe-S are a good set of headers..

Running standard ported headers on my car as I like low down power and torque so cannot help further than that.

 

JGM

Hmmm - Gruppe S - thats what has been causing my probs - V1 Manifold at 58mm with a useless up-pipe - subsequently changed to a flexi - H&S which is 54mm......... as they dont quite mate the gasket (at 54mm) leaks........ and at the last Castle Coombe day I went to registered 103db with a bung in the exhuast.......

So I have 3 Options:

1. Get a V2 Gruppe S Manifold/or other Manifold - Gruppe S is so much cheaper than anyone elses

2. Get rid of the Up-pipe and the Manifold and go for a 60mm type manifold and up-pipe set up

3. Weld the current flexi up-pipe seamlessly to the 58mm Manifold. Dont know how much I can port out the up-pipe before doing this!! - its not going to port to 58mm - so isnt ideal......... but as its a flexi it should give some cushioning - I could weld up the original 58mm Gruppe S Up-pipe but as this is not a flexi I suspect that thye Turbo gasket end will ultimately fail if I weld the up-pipe to the Manifold. I've tried all other solutions - i.e. Spacers, repositioning the up-pipe, etc, etc..............................

 

my first set of headers managed to allow 567 bhp on the dyno.

The top of the uppipe where it mated to the turbo was only two inches.

The flow is proportional to the diameter and inversely proprotional to the length of the restricted section.

 

Adam

So if I had a smaller hole at the Turbo end I would get more power......... is that due to gas speed increase into the Turbo.............