Quote:
Originally Posted by pete c
I don't have any actual stats, but, I believe that statement is backwards. I believe that a properly sized turbo uses its waste gate only at high loads.
There is one other problem here. How do you harness power from a device that is spinning at crazy rpms and is very hot? You do it with a rather complicated transmission that will cause turbo lag like you've never seen.
The bottom line is that yes, there is some wasted energy here, but harnessing it is gonna be awfully tricky if possible at all.
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Sorry Pete he is right. A properly size turbo will run a smaller size turbine then needed to keep turbo lag at a minimum. So the waste-gate will open at lower loads to keep from over boost. If you turn the boost up there will be less waste-gate flow. Check out the MatchBot link and notice the waste-gate flow at 17psi @ 7000rpm then turn it up to 22psi and adjust the turbine expansion ratio to the original turbine phi curve. You will see that a higher boost will have less % waste-gate flow.
As far as the turbine not being able to do anything useful then spin a compressor wheel and add flow. Check out what F1 is doing for the 2014 season.
Renault takes lid off of 2014 F1 turbo engine - F1technical.net
They are using the turbo to make power and taking some of the turbine flow that would normally be dumped out the waste-gate and harness it through a generator unit. The electricity can be used on demand or sent into a battery/capacitor system for later use or to be used to spin the turbo if needed for no-lag.