What is better bigger or the same size as turbo inlet. I would think it would be better to have the same size as turbo inlet for maximum velosity. Thinking of changing my mind from Helix to Turbo XS but it doesnt have a flex joint.

 

The stock size is good, 45mm. You want it a bit small so that you get the highest gas velocity going into the turbine, creating faster spool. If you are running a really big turbo, then you may want to go with a bigger uppipe. Anything the size of, say a VF22, PE1820, or APS SR40 would do fine with a stock size uppipe.

 

I thought this was the case but I saw that Helix (which I beleive is bigger in diamiter than Vishnu or turbo XS) claimed more of a hp gain. Do you think I need to worry about buying a upipe without a flex section if it is installed correctly? I see that allot of the guys say that it isnt that important and allot say it is. I really appretiate the reply, you and wingless wonder always seem to answer my questions.

 

The larger the pipe, the less the pressure, not velocity. I'd think that the reason that the larger diameter uppipes raise hp is because of less backpressure to the headers, which makes the exhaust gasses flow easier. Increasing the velocity would only make the turbo spool up faster.

 

pv=Nrt my friend. Increasing the diameter decreases both pressure and velocity.

 

I have been looking very closely at the Auto Speed Performance (ASP) uppipe, mainly because from what I have heard, seen and read their quality is superb! It also has the flex that I want but the pipe is 2" in diameter... that's exactly 50mm... would this pose a problem as far as spool up, hp loss..etc? I would also couple this with the Turbo Xs TBE with the RFL-TI axle back.

Thanks,
-Nigel

 

I would expect the larger uppipe to spool slightly slower than stock, but still much better without the cat. It's also possible that the ASP unit will show slightly better top end.

 

In my quote, when i said "The larger the pipe, the less the pressure, not velocity", i didn't mean that velocity wouldn't go down. What i meant was that you woudn't get the "maximum velocity" effect that MOREX stated in the initial post. I see though how my statement was misunderstood. Maybe i should take more english classes.