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Forced Induction Forum
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Old 08-26-2012, 03:39 PM   #41
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I did source the housing..... PTE does not offer a divided housing for the 75 turbine wheel.
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Old 08-27-2012, 10:01 AM   #42
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After speaking with Saad, Jim and Jason, the 67 is the only way to go. I thought the QSV would have shifted the power band more which seemed to not be the case. 6766 turbo hits just before 3 grand,..Ill take that over 5 grand any day. Plus with these new turbos they can put down 950hp and thats cool for me. haha
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Old 04-12-2013, 02:06 PM   #43
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Old 04-12-2013, 04:27 PM   #44
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Originally Posted by pilot1ner View Post
It wasnt converted to a twin scroll. Precision turbo makes divided housing(twin scroll).


That is correct. QSV would use the twinscroll turbine housing on a single scroll exhaust manifold. While I'm sure a true twin-scroll QSV setup could be fashioned by modifying the valve to divert exhaust gasses, it would only be a true twin scroll while the value is open.

For anyone who doesn't fully understand why QSV spools faster:

The following page from Garrett explains what Turbine AR ratios are and why a lower ratio like a 0.5 spools faster than a 0.9. It details the main drawback for lower AR ratios - limit to top end power due to increased exhaust back pressure.


QSV allows for a turbo setup to effectively be able to use a lower Turbine AR ratio at lower engine speeds or boost levels (valve closed) for faster spool and then switch to the larger AR ratio (valve open) to get the benefits of the larger AR ratio - increase top end power and reduce exhaust back-pressure.

It could also be called "Variable Turbine AR Mechanism" as that is exactly what it does with the turbo that makes it work they way it does, but that name is both unpleasant and a tongue twister.


QSV is basically a very simple way for a turbo system to be given characteristics similar to a Sequential Turbo setup. I've posted an image that Sound Performance put up that depicts the sequential turbo setup on a 2JZ (Supra engine):

Pilot1ner, a simple way to see if the QSV has made a difference for your ride is to test it. Dyno the car as is, then ask the tech to jerry rig the QSV valve so that it's stuck open (no QSV) and do another run on the dyno so you can compare the results.

If you don't see a _distinct_ difference in the runs, it's possible that the turbo was sized incorrectly for your project.

Last edited by FragNasty; 04-12-2013 at 08:13 PM.
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