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9 Second Wannabe
272 Posts
Discussion Starter · #1 ·
I've got a 70GTQ DBB turbo I bought back in 2006-2007. The other ID on the turbo tag is 7080RH BB. I'm getting 42psi of pre-turbo back pressure at 27psi of engine boost. That's 1.5x the boost pressure seen in the intake manifold. According to the internet, that pretty much tells me I'm out of turbo. Also, at 32psi of boost the backpressure is 55. My cam specs might be playing a part in that equation. Also, my intercooler seems to be free flowing with near zero pressure drop. So, what's your suggestion on a new turbo to get less backpressure?

Stock 3.8L 109 block bored .020"
3.625 Stroker Crank
212-212 duration .579" total lift at valve
Valve Springs - 200 seat pressure - 490 nose pressure
GN1R Aluminum Heads (race ported)
T&D 1.65 Roller Rockers
PT70-GTQ DBB Turbo w/.85 exh hsg
GN1 Intake (race ported)

6.48 @108mph in the 8th mile at this time with a 1.49 60'

Colorfulness Black Slope Plot Screenshot
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