max turbine flow

[merkzu]

Not sure if this is a stupid question or not.. I've seen lots of compressor maps posted around, but no turbine maps. I know there is a point where turbine flow basically flatlines above a certain exhaust pressure - that would cause the compressor wheel not to accelerate any further, and exhaust backpressure to increase, right?

If you were trying to get maximum airflow out of a smallish turbo, would it be reasonable to have an exhaust pressure controlled wastegate, set to bleed off excess exhaust pressure but hold enough to keep the turbine near its maximum flow rate?

For example on my 16G I have the wastegate shut off (100% duty on my solenoid) after 5500rpm. Is there excess exhaust backpressure I could get rid of without slowing down the compressor?

I couldn't find a single turbo set up this way so there I'm guessing theres a good reason it's never done this way.

[JET]

Yes it will create more exhaust back pressure, but it also means the turbo is flowing more. There isn't really a wall, just a point of diminishing returns. You wouldn't want to vent that back pressure, it is doing some good.

[merkzu]

Just wondering if its possible to hit a point where venting the pressure would do more good than keeping it against the turbine.. like for this 30R map



After a ratio of 2.0 it can't flow any more. I have no idea what kind of backpressure actually builds up, so is it just that you never reach that point?

[merkzu]

I found a post by a guy that measured the pressure before the turbine on an evo turbo:

http://forums.evolutionm.net/showthread.php?t=327719

48psi at 7krpm, he didn't measure the other side of the turbine though

[JET]

Take maps with a grain of salt, they are guidelines. Compressor maps are the same way, I have seen turbo's flow much more than what the map shows they should be able to.

[merkzu]

I tried lowering the boost solenoid duty cycle 10% from 6000rpm up and boost stayed the same, not sure if it helped anything though or if its even actually opening the wastegate at all.

Just bored at work today

[JET]

The WG is likely fully open at that point anyway.

[Goat Blower]

There is a simple solution to the backpressure problem, a bigger turbo.