Tube Diameter Vs Flow Rate And Velocity

[ADAM]

i am fabing a turbo header....what dia of tubing should i use for each cylinder? (i have 4cyl engine)

flow into engine will be approx 390-450cfm at 100% of boost...though when heated this will be greater..

i was thinking of using 1 inch or 1 1/2 inch stainless tubing?...also any idea of wall thickness?

does anyone know?

if it is too big velocity will slow and slow turbine....

if to small....it is to restrictive..

[Shaman]

Naturally aspirated, I use 1.75" headers and 4" collectors. If you plan to get 2/3 the power out of your engine that I have, then... hmm... the larger of the two might be required to get rid of the spent gases... if you don't get rid of the spent gases properly, you will have other problems (valves not sealing properly, etc).

Just for the record, this is one area of turbo technology I've not spent any time with. Turbo LS1 engines use stock headers or manifolds, and make 500rwhp @ 4.5#. The 700rwhp versions install customized headers.

If I were you, doing road racing on these small tracks, I'd be looking for fast spool times and midrange torque.