Maximum exhaust velocity entering turbine..??

[nissanfanatic]

I was curious if anybody on here has been able to view tests, read anywhere, or just plain find out what exhaust velocity you want to stay below at the turbine entry..?? I am aware that intake charge air velocity should not exceed 300fps as it begins to experience excessive drag. I'm asking because soon, I'm going to be upgrading to a larger turbocharger(T3/T04R w/.82ar stg5 wheel) from my current T3/T04E 50trim w/.63ar stg III. Ultimately I'll probably go to max that turbo as well and I don't want exhaust restriction holding me back because I'm aiming for a very efficient setup.

So far what I did was find the area of the opening in a T3 and T4 flange, then work that backwards in the formula for finding the area of a circle to determine what its equivalent would be in piping diameter, then plug that number into a pipe flow calculator. The pipe flow calculator gives velocity and reynolds number.

So, if I knew what exhaust velocity I was looking for, I could then decide which flange I should go with. I'm already leaning towards T4, but I don't want to go T4 yet if I don't have to. This turbo should do a hair over 700whp. It flows 75lb/min. Any info is appreciated.

-Cory
1992 240sx KA24DE turbo:Faster than "Your Buddy's" car
Stock internals
419whp/378tq-20psi
12.6 at 122.3mph-22psi

 

[SPOrotary]

Basically the major limiting factor is the speed of sound at the density of your exhaust gas. You need to know the temperature and flow that you are going to get out the exhaust port. Once you know these factors the speed of sound is an easy equation away.

The SoS in your average exhaust gas should be above 500m/s so you can easily push the velocity beyond 400m/s without suffering to much backpressure. After the turbine is another question entirely.

Current project car: '98 BMW 316i
Main targets: 950kg, 250rwhp, min. 1G lateral grip. Special: Twincharger system, hydraulic ebrake, New suspension.