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Need help from the high CR boosted guys

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Old 05-19-2016, 08:54 PM
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Default Need help from the high CR boosted guys

Guys I need some help. Currently running a 11.2:1 408. PRC 237's and a tv2 cam thru a level 5 T56 and a moser 12bolt with a 3.73 gear. I'm kicking around the idea of running a single turbo with low boost changing as little as possible. A local shop here isn't afraid of the high CR. Says with c16 (cause e85 isn't reliable here) and low boost we should be fine. He suggested a GTX4202R to spool fast. Anyone run anything similar to my build? Would a PT7675 or even an older PT88 be a better choice.

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Old 05-19-2016, 09:32 PM
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I do not currently have a boosted car, but prior to my Vette I ran a '95 TA vert with a blown 383 stroker. It was at 10.5:1 static CR, and ran 9lbs of boost at the manifold.
Boosted engines make the most power possible with low static CR and high boost, this is true. But it's only really pertinent for a pure race car. For a street driven car, I believe you're better off with slightly less peak power, but more usable power from the much wider torque band you'll get with a higher static CR and lower boost.
Old 05-19-2016, 09:55 PM
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That's what I was thinking. From what I have heard compression helps to spool up turbos and makes lag less of an issue. I guess I just needed to hear it from others as well.
Old 05-22-2016, 02:08 AM
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Get a meth injection kit unless you plan to run c16 race fuel everywhere you go? I run 11:1 compression with 91 octane and straight methanol injection on a stock bottom end ls1 6 speed car. I normally run 8 psi ( 640 rwhp ) with no problems at all on a precision 76gts. I have dynod 730 rwhp on 11psi but that's on the limit of 91 + meth.
Old 05-22-2016, 11:25 AM
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Originally Posted by Trais
Guys I need some help. Currently running a 11.2:1 408. PRC 237's and a tv2 cam thru a level 5 T56 and a moser 12bolt with a 3.73 gear. I'm kicking around the idea of running a single turbo with low boost changing as little as possible. A local shop here isn't afraid of the high CR. Says with c16 (cause e85 isn't reliable here) and low boost we should be fine. He suggested a GTX4202R to spool fast. Anyone run anything similar to my build? Would a PT7675 or even an older PT88 be a better choice.
In my honest opinion don't run the gtx4202 on that motor it's honestly to small for that compression and cubic inch. Gtx5008r would work a hell of alot better. Not to mention u will more than likely max the 4202 out pretty quick.
Old 05-22-2016, 12:02 PM
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Lol at E85 not being reliable. Looks like your tuner doesn't know **** about knock threshold.
Old 05-23-2016, 05:01 AM
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gtx4202.. we maxed the exhaust side of one of those on a 2.5L 4 cyl motor at around 750hp the other week. yeah it had a small housing but you still dont need something that small on a v8


my last motor was around 11.5:1 25psi boost 408ci pump e85.

rebuilt it now and have dropped to around 10.0:1 comp. why? because yea e85 will take the compression and boost, but it makes the tuning window very small. 1 tiny fuckup and shes all over.
Old 05-24-2016, 09:12 PM
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10.7:1 here on e85. I wish I could bump it up but I'll wait until I build it.
Old 05-25-2016, 06:28 AM
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Stock LS2 10.9:1 here with a D1SC on 91 octane pump + 20-30% ethanol E85 mix and propane injection. Wastegated at 7psi. Carry on.



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