Quote:
Originally Posted by tb13
I think displacement and target power levels would make a big difference in how you would setup your waste gates. If you were on a small displacment 4cyl platform only shooting for 500whp you might be able to get away with only a single waste gate before your primary, small, turbo. When you step up to a inline 6 I just don't think it would be feasible to try and force all of the exhaust gasses through the primary turbo and still hope to have solid exhaust flow and low back pressure.
Would a properly sized primary turbo being twin scroll really make that much of a difference? I feel like it would be difficult to justify a twin scroll primary turbo on a setup that wasn't built to make 1kwhp+ on a 4cly application. Even then, properly sizing the turbos would probably keep a good balance of response to overall power output.
Also, wouldn't diverting gasses around the smaller turbo help maintain the energy that is otherwise lost when it flows through that smaller turbo? That energy would only be wasted once the smaller turbo has made its target boost. Sending it directly to the secondary turbo would allow for better overall response.
Don't know why I really care, but this stuff is really interesting to me...
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Honestly, if you're looking for 500whp out of your 4-cyl you're probably better off with a 7163 efr IMHO. Compounds are better suited for big power and good response. I guess I've just never seen a setup with a tiny turbo that seemed like it could justify it's complexity. Everything is a compromise though, so it's possible there's a 5-600whp setup out there that works extremely well.
Twin-scroll makes a big difference, regardless of compound or not. Whether it's "worth it" or not is up to the person building the system. I've seen a system built with an OEM Evo 9 turbo. Was it convoluted? Yes. Did it respond ridiculously quickly? Also yes. The GenII GTX's do seem like they would be a nice turbo to run if you were set on running something that small, provided you can get enough exhaust around the turbine.
Oh, and you'll definitely want a wastegate that diverts gasses back into the transfer pipe, that's necessary to keep the low-pressure turbo's speed down.