I know that a Q trim wheel allows for better top end power at the expense of a few hundred rpm in spool time and allows for less backpressure at higher boost levels. However, I dont understand where/when a Q trim wheel becomes a necessity over a P trim wheel in terms of creating too much backpressure.

Is it even a matter of necessity or just a matter of preference and how you want the car to perform? For comparative purposes (at least to start), let's say that we are using a t-66 compressor on a 1.00 turbine housing. I see many of you recommend a Q trim wheel, but if the user is only using that turbo to say 15 psi, is the Q wheel really a necessity or is it only a necessity if the user is pushing more pressure/HP on that compressor? I could see a Q trim wheel if you're going to be running 25-30 psi, but why at 15 psi?

I hope I explained that well enough...

TIA,

 

The Q trim in the T66 (only) generally spools as fast as the P trim, with better top end. The Qtrim in theory should give another 50-70hp on the BIG end, the big end being 25-30psi. At less than 20 psi you will get a slightly slower spool, at 20-30 psi I expect similar spool with better top end(esp flat torque). These are only piston engine observations, not theory, and not rotary fact. Later, Carl

 

thanks for the response Carl

I've seen most of that in action and read about it plenty times of people running the t66 with a Q trim and being pretty happy with the setup.

my real question is when does the Q trim become a necessary component over the P trim due to backpressure issues in a rotary application....and i'm talking street port here. I wouldn't use anything less than a Q trim on a halfbridge or anything more aggressive.

anybody?

maybe my question is confusing how i'm asking it??

 

anything over 550rwhp needs a Q-trim....Is that what you're asking?

 

ya, basically

wasn't necessarily looking for it in terms of HP, but that'll work

thanks

 

TURBOSTREETFIGHTER, back when he was on here, had used Q-trim wheels many times. He always complained that they were fragile. They are also much heavier than the P-trim wheels. He suggested using a P-trim with a 20 degree clip and a larger a/r housing (if you can get one). Since I haven't used one I don't directly know. That is just what he said so just take it for what it's worth.

 

interesting....

so if dealing with a 1.00Q, he would rather run a 1.15 P trim with a clipped wheel?? That is also a pretty aggressive clip. I thought clipping the wheel made the turbine characteristics lean more so to like it was using a larger housing, but then he would run a larger housing on top of that you're saying...

all i can say is interesting b/c i'm trying to make sense of that with the level of knowledge i have in all of this.

Clipping the wheel allows for less backpressure so I could see him maybe saying to clip the wheel for it to allow the turbine to breathe like it is using a larger trim wheel, but I dont get why he recommends going up in housing size....

Anyone have any idea what makes the Q trim wheel more "fragile" than a P trim wheel? just the design? anyone have pictures of one design next to the other??

 

Good thread and I'm just as interested as suganuma to get some answers. Please keep them coming.

Zach