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Report on TPI's 75x90mm throttle body

1132 Views 11 Replies 7 Participants Last post by  Rey
The December issue of Hotrod, page 154 has a very favorable report on TPIS's 75x90mm throttle body mounted on an LS6 intake with a huge #15 cam. On a Superflow engine dyno the combo made a 32 hp gain, and there is gain all across the spectrum.
It appears that the LS6 intake manifold has a far better design than the new LS2.
I've known Myron Cottrell, owner of TPIS for over 45 years now. Naturally, I favor his products. Myron has an '04 CTS-V and installed this oval tb on it. It gained 18 rwhp to 382 rwhp - TPIS headers and cats, stock exhaust and stock intake.
I visited TPIS this last September, and tried the oval tb on my '05. It is a magnifcent improvement. No flat spots anywhere and increased power everywhere, BUT, there was an anoying intake chrip/whistle at low to moderate throttle transition. We spent a full day locating the noise. It is at throttle shaft edge of the intake. We could not eliminate the noise. It was barely tolerable on Myron's '04, and intolerable on my '05. We don't know why the difference, but the end result is that Myron won't sell them for CTS-Vs. He has had no complaints from Corvette or Comaro owners, mainly, he thinks, because their loud exhausts drown this noise.
I did leave Chaska, MN with a ported stock tb. This increased power also, but more in the area of 8-9 rwhp.
The good news is that TPIS is now working on a method to adapt the 90mm circular tb to our LS6 intakes. Stay tuned.
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Sounds great!!! How do we get our stock trottle body ported? Thanks for the information. Good forum contribution!
I'll hold out for TPI's to perfect theirs. I like a company that doesn't or won't release something until their satisfied with it.
Just port the stock one, or get the ported stock one.
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Rey said:
...It appears that the LS6 intake manifold has a far better design than the new LS2.
I was under the impression that the LS2 uses an LS6 intake. :hmm:

The LS2 uses a LS2 intake that comes with a 90mm throttle body from the factory.
Parker said:
The LS2 uses a LS2 intake that comes with a 90mm throttle body from the factory.

:eek: Duh. I forgot about that. It's the heads that are the same, right?

[Sorry for the mini-jack Rey.]

I've known people to flatten the TB post on the plate to allow for better flow. It may be that if the post is ground down and smoothed, to the profile of an oval, the noise may not happen. I'm sure TPIS has thought of this, so we'll see how it looks when they're done with it.
Lots of vendors offer ported throttle bodies. Naturally, some are better than others. I think TPIS's price is about $215.
On TPIS's oval throttle body the TB post is "flattened" to allow for better flow. It still chriped.
Looking at the factory LS2 90 mm throttle body I ordered in anticipation of TPIS's modified intake manifold, I see that the throttle plate is not quite circular. It is very slightly oval, which results in small air gaps. It may well be that these air gaps are engineered to eliminate the chirp.
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