Bob(EPP) or anyone else-10.7:1 c/r and boost question
WIMPS!!!
My daily driver LS2-GTO w/ 10.9:1 loves the 7psi it sees on a routine basis
. AND, it pushed 550rwhp/600rwtq at >13 psi...by 4600 rpm [but we zero'd out the maf by 4500 rpm...yep, those #'s came in the mid-4000 rpm range!] with NO KR! On 93 octane w/ methanol & water...not even using the methanol on the 7psi setting.
That said, I think that I may drop in some dished, forged pistons and a custom cam...talk to Jose about mods to the 67 turbo on my car...and plan for a nice, safe 650- or so.
My daily driver LS2-GTO w/ 10.9:1 loves the 7psi it sees on a routine basis
. AND, it pushed 550rwhp/600rwtq at >13 psi...by 4600 rpm [but we zero'd out the maf by 4500 rpm...yep, those #'s came in the mid-4000 rpm range!] with NO KR! On 93 octane w/ methanol & water...not even using the methanol on the 7psi setting.That said, I think that I may drop in some dished, forged pistons and a custom cam...talk to Jose about mods to the 67 turbo on my car...and plan for a nice, safe 650- or so.
TECH Addict
Joined: Jul 2005
Posts: 2,153
Likes: 3
High compression and boost is a great thing, providing you have the octane for it.
However, on limited octane, you'll be driving around a combination not near its potential. A while back, my LT1 had 10.8/1 compression and 9 psi from a Vortech T-trim. It only made 400 rwhp because the timing had to be drastically retarded. Every time I drove it, I couldn't quit thinking about how much faster if would be with 8.5/1 compression, more boost and more timing. I eventually lowered the compression, raised the boost to 14 psi, added an intercooler and more timing and made 550 rwhp.
Mike
However, on limited octane, you'll be driving around a combination not near its potential. A while back, my LT1 had 10.8/1 compression and 9 psi from a Vortech T-trim. It only made 400 rwhp because the timing had to be drastically retarded. Every time I drove it, I couldn't quit thinking about how much faster if would be with 8.5/1 compression, more boost and more timing. I eventually lowered the compression, raised the boost to 14 psi, added an intercooler and more timing and made 550 rwhp.
Mike
I'd worry more about the stock bottom end of the motor.High compression and big Cams can make a ton of power with ATI's.Our race cars run 11-1 compression and 28lbs of boost.My personal Vette ran and still runs 14lbs of boost on the stock motor-16k miles so far.If the fueling and timing are good it will last
my car felt really nice with when it had 10:1 compression and 10 lbs of boost, but i am pretty sure my tune was off and that's why I lost a ringland.
I since rebuilt with diamond pistons/callies rods, arp bolts , etc and my compression is around 9.3:1, with 10 lbs. No knock. I'm gonna add 50 lb injectors, a regulator and go to a smaller pulley, hoping to run 13 lbs on pump gas safely. This should be cruise into the 10's fairly easy with my mom driving.
I since rebuilt with diamond pistons/callies rods, arp bolts , etc and my compression is around 9.3:1, with 10 lbs. No knock. I'm gonna add 50 lb injectors, a regulator and go to a smaller pulley, hoping to run 13 lbs on pump gas safely. This should be cruise into the 10's fairly easy with my mom driving.
Then we go YSi and heads
MTBDOC-sounds like you got money but if you continue to run on 13 lbs you will go BOOM. you may not have knock the pistons are still cast and the ringlands are a major weaklink.
MTBDOC-sounds like you got money but if you continue to run on 13 lbs you will go BOOM. you may not have knock the pistons are still cast and the ringlands are a major weaklink.
Hi, real world experience speaking here...
I (unknowingly) ran 5psi on top of 11.8:1 compression milled 5.3L heads for a few months before my new heads came in. No detonation and no problems, 91 octane plus a gallon or two of VP103 unleaded in each tank, ~18 degrees of timing. I later found out the heads were milled more than I knew - I thought they were closer to 11.1:1.
Of course I have a 222/224 114LSA cam, nothing like your cam. Your cam will bleed a lot of boost...
The question becomes "is it worth the several thousand dollar expense to run <=5psi ?". That money would probably be better spent elsewhere... N2o would provide similar (or more) gains at a fraction of the price.
Just thought I'd throw that out there - it's not impossible, just maybe not the best decision.
Change your cam and heads and it's a whole new ballgame...
Rob (Bad30th)
I (unknowingly) ran 5psi on top of 11.8:1 compression milled 5.3L heads for a few months before my new heads came in. No detonation and no problems, 91 octane plus a gallon or two of VP103 unleaded in each tank, ~18 degrees of timing. I later found out the heads were milled more than I knew - I thought they were closer to 11.1:1.
Of course I have a 222/224 114LSA cam, nothing like your cam. Your cam will bleed a lot of boost...
The question becomes "is it worth the several thousand dollar expense to run <=5psi ?". That money would probably be better spent elsewhere... N2o would provide similar (or more) gains at a fraction of the price.
Just thought I'd throw that out there - it's not impossible, just maybe not the best decision.
Change your cam and heads and it's a whole new ballgame...
Rob (Bad30th)
10 Second Club
Joined: Dec 2004
Posts: 138
Likes: 0
From: FL First in Beer Flight
Originally Posted by Got Me SOM
my car felt really nice with when it had 10:1 compression and 10 lbs of boost, but i am pretty sure my tune was off and that's why I lost a ringland.
I since rebuilt with diamond pistons/callies rods, arp bolts , etc and my compression is around 9.3:1, with 10 lbs. No knock. I'm gonna add 50 lb injectors, a regulator and go to a smaller pulley, hoping to run 13 lbs on pump gas safely. This should be cruise into the 10's fairly easy with my mom driving.
I since rebuilt with diamond pistons/callies rods, arp bolts , etc and my compression is around 9.3:1, with 10 lbs. No knock. I'm gonna add 50 lb injectors, a regulator and go to a smaller pulley, hoping to run 13 lbs on pump gas safely. This should be cruise into the 10's fairly easy with my mom driving.
Thread Starter
Teching In
Joined: Oct 2005
Posts: 14
Likes: 0
I was just looking at- gm hi tech from july/aug 05- they did a grand national segment in the magazine with high boost engines, one guy is running a 110 lsa. 236/236 584/584,and 22psi however he does have 9:1 c/r. just wanted to add those .02 to make my self feel better. thanks again guys
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