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Up it to 15 psi ? Stock bottom end/ meth-water inj - CR 9.7:1

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Up it to 15 psi ? Stock bottom end/ meth-water inj - CR 9.7:1

 
Old 01-05-2019, 07:05 PM
  #1  
dizwiz24
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Default Up it to 15 psi ? Stock bottom end/ meth-water inj - CR 9.7:1

am i nuts for considering it? Thinking about going to smaller pulley on p-1sc as I will be proactively replacing the drive belt. Its a dedicated drive belt with lots of wrap on a colleted and slotted pulley (blowerworks) so i am not worried about slip.

fuel system is way overbuilt (2 pumps) and i have the earlier model car with return fuel line vs dead head. I am not worried about running out of fuel. 60 lb/hr inj.

bigger cc heads dropped my compression to 9.7:1.
Meth-water inj keeps it cool (no intercooler).

boost currently is
3000: 5
4000: 7.5
5000: 10
6000: 12.5
redline is 6500 rpm.

What i really seek to achieve is more boost down low....that said would you pulley down if you were me?

Stock knock system is functional and operative - though id hate to be triggering it constantly from excessive boost
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Old 01-06-2019, 10:55 AM
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helga203
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When i had my p1 i had a 3.2 pulley on it at 12 13ish boost. Down low was awesome. had over 500ft by 3k ish. but had some belt slip at the higher RPM range. But was worth it with the down low power.. It was a street car so light to light was ripping. stock bottom end engine with headers lpe heads cam. 80 injectors with 2 -15 meth nozzles. no intercooler but meth keep it nice and cool.

Last edited by helga203; 01-06-2019 at 10:57 AM.
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Old 01-06-2019, 12:20 PM
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junk c5
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I hurt a piston at 15lbs on a 1999 ls1 stock bottom end . Front mount intercooler and meth on 93 octane.
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Old 01-08-2019, 12:40 AM
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_zebra
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do they still make those restrictor plates that let you pulley down for quicker/lower boost but choke it up top so it still flows the same air as it does now?
or maybe rig up a wastegate-style boost relief on the intake for the same effect?
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Old 01-08-2019, 12:17 PM
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algZO6
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I beat the hell out of mine on 15 for years with an old T-1. Good fuel, tune, and meth you will be good.
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Old 01-08-2019, 12:40 PM
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69GTO96Z
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Originally Posted by _zebra View Post
do they still make those restrictor plates that let you pulley down for quicker/lower boost but choke it up top so it still flows the same air as it does now?
or maybe rig up a wastegate-style boost relief on the intake for the same effect?
You can do a wastegate, but from my research, you would only want to gate off a couple of psi. I say pulley it to 15, use good fuel, a spot on tune, and use meth as a safety net instead of trying to squeeze more timing into the tune.
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Old 01-08-2019, 01:20 PM
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TastyBacon
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Originally Posted by junk c5 View Post
I hurt a piston at 15lbs on a 1999 ls1 stock bottom end . Front mount intercooler and meth on 93 octane.
What kind of damage? How much timing?
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Old 01-08-2019, 04:36 PM
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junk c5
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IDK what the timing was. I believe it lifted a ring land on the #7 piston. Pressured the crankcase enough to push out the valve cover gasket. Oil leaked down the rear of the motor and caught the exhaust on fire under the car. Car could have burnt to the ground if I didn’t have a fire extinguisher. Damage was minimal. Burned 02 sensor wires
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Old 01-08-2019, 04:42 PM
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TastyBacon
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Originally Posted by junk c5 View Post
IDK what the timing was. I believe it lifted a ring land on the #7 piston. Pressured the crankcase enough to push out the valve cover gasket. Oil leaked down the rear of the motor and caught the exhaust on fire under the car. Car could have burnt to the ground if I didnít have a fire extinguisher. Damage was minimal. Burned 02 sensor wires
Wow, glad you were able to save it.
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Old 01-10-2019, 05:59 PM
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tabbruzz
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Originally Posted by TastyBacon View Post
What kind of damage? How much timing?
How long did it last before it blew? Was it professionally tuned? I have a 99 with an A&A kit going in which is why I am asking...
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Old 01-10-2019, 10:14 PM
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neutron82
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what really matters is the pressure in the cylinders, that's where the party happens
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Old 01-11-2019, 01:29 AM
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junk c5
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It lasted about two years. It was professionally tuned. That cylinder in particular is supposed to be the weak link. At least that’s what I’ve read. Maybe a little more meth would have helped or a cam that provided lower cylinder pressure.
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Old 01-11-2019, 01:36 AM
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there are a number of professionals who've blown up engines. there are also plenty of folks who tune for themselves or as a hobby & are great at it.
the monetary incentive of someone's tuning experience ain't always an indicator of his quality or expertise.
i ain't saying your tuner's bad or anything - just commenting on the common over-emphasis some folks place on whether or not somebody tunes for a living & using that as a qualifier.
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Old 01-11-2019, 01:23 PM
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tabbruzz
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Originally Posted by junk c5 View Post
It lasted about two years. It was professionally tuned. That cylinder in particular is supposed to be the weak link. At least thatís what Iíve read. Maybe a little more meth would have helped or a cam that provided lower cylinder pressure.
Thanks for the info. This is one of the things I was considering while I was trtying to decide on what A&A pulley to go with. I whimped out and went with a 3.8 in order to keep the boost somewhere between 7-9psi.....Then I can always go for more boost......but 2 years at 15psi, is a fun 2 years
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