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Discussion Starter #1 (Edited)
I have a 95 TT 6 speed and my turbonetics T66 went out on me last week so its being rebuilt as we speak. Its was a T66 with 0.7 a/r and p trim. After I got the T66, i had a change of heart and wish i had gotten a little bigger turbo. I will never drag race this car, and it will be mostly for stree/highway rolls. I will also never plan on using race gas. I have the option of rebuilding the T66 to the same specs, or upgrading it to a T72 for no additional cost, since the wheel is damaged and has to be changed anyways.

I will have AEM, full fuel setup, 272/264 cams, crower springs and ti retainers, when the new turbo comes back. My reasoning for changing to a bigger turbo was since I plan on only using pump 93+meth for 95% of my usage, i wanted a bigger turbo that i could use less boost and have more power upto the 25-26psi range. I really didn't care how much power i could put down at 32psi with the T66 since I will not be using c16. I also didn't want to go too big like a T74 or T76 for the obvious increased lag. I figured the T72 would be a nice middle ground. What are your thoughts???? Anybody can comment on spool differences between T72, T74, and a T76??? Remember that the trim will remain a p trim.
 

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My thoughts are based on past events, I did exactly what you are thinking of doing a couple of mths ago with the same logic/thought process you are using related to pump/meth tune ect. The only diff was there was nothing wrong/damaged with my T66, P-trim, .70AR. I just wanted to step it up a bit more after having had it for about 2 yrs. Absolutely no regrets, the T72, Q-trim, .81AR @18psi boost felt like the T66 @24psi boost. Interestingly the tune for 11.5 AFR @24psi for the T66 produced nearly the same 11.5AFR @18psi for the T72. I am not sure if you can use that to assume/deduce that the power is comparable at those boost levels but that's what it felt like. I am now up to 22psi as my everyday street tune with the T72 and it is awesome/scary/you name any explentave it's it! My advise is biased towards what I like to do which is "60mph to I'm really scared now speeds" as quickly as possible. Cheers Phil.
 

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Discussion Starter #3
^^^Thank you so much. That is the kind of real world feedback I was looking for.
 

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My thoughts:
A lot of what allows a "bigger turbo" to support more power at a given boost is the exhaust side, not the compressor. In the same vein, the exhaust side is the main determiner of spool, so if you keep the same exhaust side, I wouldn't expect a lot of difference between spools with the 66 and 72 compressors. I think the 74 and 76 might surge under some conditions with that P-trim exhaust in a .70 housing, but I'm not sure. A 72 is probably a better choice given the rest of your setup and plans (but again, I'm not certain).


alpha6164 said:
I have a 95 TT 6 speed and my turbonetics T66 went out on me last week so its being rebuilt as we speak. Its was a T66 with 0.7 a/r and p trim. After I got the T66, i had a change of heart and wish i had gotten a little bigger turbo. I will never drag race this car, and it will be mostly for stree/highway rolls. I will also never plan on using race gas. I have the option of rebuilding the T66 to the same specs, or upgrading it to a T72 for no additional cost, since the wheel is damaged and has to be changed anyways.

I will have AEM, full fuel setup, 272/264 cams, crower springs and ti retainers, when the new turbo comes back. My reasoning for changing to a bigger turbo was since I plan on only using pump 93+meth for 95% of my usage, i wanted a bigger turbo that i could use less boost and have more power upto the 25-26psi range. I really didn't care how much power i could put down at 32psi with the T66 since I will not be using c16. I also didn't want to go too big like a T74 or T76 for the obvious increased lag. I figured the T72 would be a nice middle ground. What are your thoughts???? Anybody can comment on spool differences between T72, T74, and a T76??? Remember that the trim will remain a p trim.
 

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If you change over to a T72 Q-trim with the Ball Bearing option and a 4" exhaust/housing spool difference for hard boost will be negligeable between the 72 and 66. The 66 will make more progressive small boost earlier which probably helps driveability, but they will hit hard about the same time/rpm. Thats vs. a standard bearing T66 with 3" back.
 

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alpha6164,

Since those are the two choices you are looking at then I would pick the T-72. Before I had gone single, my stock twins in twin mode came on at 4000 rpms. After installing the T-72, with 272 cams mind you, it was EXACTLY the same spool. All of this was accomplished on a VPC/AFC combo.

The turbo was a DBB T-72 Q with a 0.70 A/R by innovative.

Hope this helps guy!

H
 
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