Exhaust Diameter for the 1.6L

["Harry Jones" <hjones1@airmail.net>]

I am in the process of putting a new exhaust on an IT Scirocco and I am
looking for some advice / suggestions. The car has a 1.6L with a Tri-Y
header, G-grind cam and considerable head work (all IT legal , so no
massive valves or extensive polishing, just match ported and such).

What I want is an exhaust pipe from the end of the header, exiting on the
passenger's side, forward of the rear wheel. No cat / No muffler , just
pipe. Yes, I know it will be loud, but the car only runs on the track and
sound control is not a major issue at most of the tracks / events that I
run. I am looking for ANY hp gain!

My Questions : 

1. What diameter will work best? I currently have a 2" pipe, rear exit. I
have seen people running 1.5", 2", 2.5" and 3" systems.

2. I have heard that the pipe must be as straight as possible up to X
inches behind the header junction. Does anyone have any dyno-proven
measurements on how many inches the pipe must "be straight" before a bend?
I have heard 42" and 50". 

Harry

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