View Poll Results: what compression ratio are your running with boost?
8:1
8
2.92%
8.5:1
44
16.06%
9:1
55
20.07%
9.5:1
69
25.18%
10:1
66
24.09%
11:1
32
11.68%
Voters: 274. You may not vote on this poll
High static compression and forced induction
As far as a head gasket recommendation, what ever thickness will yeild a 0.040" - 0.050" quench.
10:1 compression would make a centrifugal setup very nice n snappy and torquey and then you'll have the nice top end pull with the sc.
just add meth if you think you'll be detonating.
I dropped the compression on mine from 10:1 to 9:1 and the car was really a lot weaker down low and I had to rev it higher to make the power.
On the 10:1 setup with stock/cam heads I made approx 480 rwhp (thru an auto) at 6200 at 9-10 lbs of boost (vortech)
On the 9:1 setp with 224/230 cam stock heads I made 526 rwhp at 6700.(12-13 lbs) I believe I could have made 550-560 with probably 30-40 ftlbs more torque throughout if i had the 10:1 compression and still be safe on pump gas.
I had planned to go with a bigger blower down the road hence the 9:1 compression but had I kept that head unit I would have opted for 10:1 again. i had no knock whatsoever.
centrifugals like compression.
just add meth if you think you'll be detonating.
I dropped the compression on mine from 10:1 to 9:1 and the car was really a lot weaker down low and I had to rev it higher to make the power.
On the 10:1 setup with stock/cam heads I made approx 480 rwhp (thru an auto) at 6200 at 9-10 lbs of boost (vortech)
On the 9:1 setp with 224/230 cam stock heads I made 526 rwhp at 6700.(12-13 lbs) I believe I could have made 550-560 with probably 30-40 ftlbs more torque throughout if i had the 10:1 compression and still be safe on pump gas.
I had planned to go with a bigger blower down the road hence the 9:1 compression but had I kept that head unit I would have opted for 10:1 again. i had no knock whatsoever.
centrifugals like compression.
Last edited by Got Me SOM; Dec 7, 2007 at 09:02 PM.
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From: Elmhurst, IL (Chicago Suburb)
I would say at least 10:0 to 1, with only 9 to 10 lbs of boost it won't be easy (and might take 10:5 to 1.
ERIK Koenig of HKE Racing is finishing up my forged 347 LS6 motor as we speak, and I shoud be over 700rwhp no problem, via my ECS D1SC making about 12 lbs of boost at 9:5 to 1, and nice COMP blower cam and TEA high flowing Stage II LS6 heads. I reallly wanted 10:0 to 1 compression for that extra edge on and off the boost but the 9:5 to 1 should be fine, and I can always turn up the wick to 15lbs or so if i want to start making crazy power.
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From: Texas
At 10.1:1 I made 680rwhp uncorrected (668 SAE corrected)) on a low 60* to high 50* day last spring. That was at 9.4psi and a little belt slip starting at 6200-6300rpm. IMHO with a little bump to 10.5:1 and a full 10-11psi I could have reached very close to or slightly surpassed the magical 700rwhp goal. Something I may make a run at this winter 
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From: Tinker till it blows, then back it off a notch, maybe!!
At 10.1:1 I made 680rwhp uncorrected (668 SAE corrected)) on a low 60* to high 50* day last spring. That was at 9.4psi and a little belt slip starting at 6200-6300rpm. IMHO with a little bump to 10.5:1 and a full 10-11psi I could have reached very close to or slightly surpassed the magical 700rwhp goal. Something I may make a run at this winter
If at 668 now, you won't be satisfied for too long at 700.....
If you think you can get anything for your current engine, then why not build a good one and off the old one? Then the sky is the limit....almost
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From: Texas
....just want more now till I have the $$$ to piece together my forged motor...
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That's exacty what I did and I hope it don't bite me in the *** as I am a firm believer in not fixing what is not broken!
With any bit of luck though I should be good to go! TECH Apprentice
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From: Tinker till it blows, then back it off a notch, maybe!!
I dynoed 621/647 at the wheels @ 9 psi and my tune was always very rich....one cold night, I was seeing 13 psi, still rich and the car had to be pushing 700/700 or maybe more???...I was walking away from a lot of high powered cars, even after #1 rod was bent....
Plus, I just can't stay out of it in the heat of battle, so here comes the 383 version...soon
Just gotta do what I gotta do....it's in the blood, I think
On my C5 I had headers and a procharger P1 set at 14lbs on pump gas. It made 500rwhp -- but where did it make 500rwhp? It held 500rwhp for 2k rpm due to tuning. Car ran 10.7 at 130mph with nitto's and stock 3.42 gears. I bet if the car made a peak of 500hp at redline it would run alot slower.It has been 3-4 years and the car is still running at the same boost level on the stock motor but with a cam that put it up to 600rwhp.
Depends on Cam. I would run 10.5-1 on pump gas. It's never about peak hp #'s. If you want a fast car it's about average power.
On my C5 I had headers and a procharger P1 set at 14lbs on pump gas. It made 500rwhp -- but where did it make 500rwhp? It held 500rwhp for 2k rpm due to tuning. Car ran 10.7 at 130mph with nitto's and stock 3.42 gears. I bet if the car made a peak of 500hp at redline it would run alot slower.It has been 3-4 years and the car is still running at the same boost level on the stock motor but with a cam that put it up to 600rwhp.
On my C5 I had headers and a procharger P1 set at 14lbs on pump gas. It made 500rwhp -- but where did it make 500rwhp? It held 500rwhp for 2k rpm due to tuning. Car ran 10.7 at 130mph with nitto's and stock 3.42 gears. I bet if the car made a peak of 500hp at redline it would run alot slower.It has been 3-4 years and the car is still running at the same boost level on the stock motor but with a cam that put it up to 600rwhp.
Can you tell us your cam specs and the thought process behind those specs? For example what did you want the cam to do and what kind of overlap and DCR does it have
Its only money right? What's up dude? I would have just put a bigger head unit on with stock cubes. If money's no object I'd go with a 454 lsx and stick a f1 on it with a decent set of heads n cam. You'd make 7-750 on 93.
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From: Elmhurst, IL (Chicago Suburb)
Hey JEFF,
How you doing bro? Enjoying that Florida winter weather and scenery I bet. $ is tight bud so looking to make 700rwhp with stock cubes and D1 which should be no problem but this **** is always SO ******* EXPENSIVE (no matter which route you go)!
Nice hearing from you man and have a great holiday season!
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From: Orlaanndoooo
This is more of me thinking aloud than anything but correct or confirm me...
This is an oversimplification and assumes things like comparable SC efficiency and intercoolers that would have the same heat rejection capabilities at different boost levels but bear with me. Given 2 a/a intercooled SC pump gas vehicles, both identical with the exception of:
engine A is high compression lower boost
engine B is lower compression higher boost
Engine B is going to be a tad less snappy under part throttle no boost situations but not enough to lose sleep over...those with this combo seem to support that notion. In my mind it tends to fall under the category of "if it's not snappy enough, give her more throttle." Engine B is also going to have a little more power loss due to spinning the centrifugal harder but arguably relevant with the overall power increase.
My main point to ponder is this: How do the two compare across the entire powerband? Would engine B see more air/fuel getting packed into the combustion chambers sooner thus fattening up more of the torque curve? At various points along the rpm range (before peak) would the increased manifold pressure seen by engine B outperform the SCR benefit of engine A?
This is an oversimplification and assumes things like comparable SC efficiency and intercoolers that would have the same heat rejection capabilities at different boost levels but bear with me. Given 2 a/a intercooled SC pump gas vehicles, both identical with the exception of:
engine A is high compression lower boost
engine B is lower compression higher boost
Engine B is going to be a tad less snappy under part throttle no boost situations but not enough to lose sleep over...those with this combo seem to support that notion. In my mind it tends to fall under the category of "if it's not snappy enough, give her more throttle." Engine B is also going to have a little more power loss due to spinning the centrifugal harder but arguably relevant with the overall power increase.
My main point to ponder is this: How do the two compare across the entire powerband? Would engine B see more air/fuel getting packed into the combustion chambers sooner thus fattening up more of the torque curve? At various points along the rpm range (before peak) would the increased manifold pressure seen by engine B outperform the SCR benefit of engine A?
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From: Texas
This is more of me thinking aloud than anything but correct or confirm me...
This is an oversimplification and assumes things like comparable SC efficiency and intercoolers that would have the same heat rejection capabilities at different boost levels but bear with me. Given 2 a/a intercooled SC pump gas vehicles, both identical with the exception of:
engine A is high compression lower boost
engine B is lower compression higher boost
Engine B is going to be a tad less snappy under part throttle no boost situations but not enough to lose sleep over...those with this combo seem to support that notion. In my mind it tends to fall under the category of "if it's not snappy enough, give her more throttle." Engine B is also going to have a little more power loss due to spinning the centrifugal harder but arguably relevant with the overall power increase.
My main point to ponder is this: How do the two compare across the entire powerband? Would engine B see more air/fuel getting packed into the combustion chambers sooner thus fattening up more of the torque curve? At various points along the rpm range (before peak) would the increased manifold pressure seen by engine B outperform the SCR benefit of engine A?
This is an oversimplification and assumes things like comparable SC efficiency and intercoolers that would have the same heat rejection capabilities at different boost levels but bear with me. Given 2 a/a intercooled SC pump gas vehicles, both identical with the exception of:
engine A is high compression lower boost
engine B is lower compression higher boost
Engine B is going to be a tad less snappy under part throttle no boost situations but not enough to lose sleep over...those with this combo seem to support that notion. In my mind it tends to fall under the category of "if it's not snappy enough, give her more throttle." Engine B is also going to have a little more power loss due to spinning the centrifugal harder but arguably relevant with the overall power increase.
My main point to ponder is this: How do the two compare across the entire powerband? Would engine B see more air/fuel getting packed into the combustion chambers sooner thus fattening up more of the torque curve? At various points along the rpm range (before peak) would the increased manifold pressure seen by engine B outperform the SCR benefit of engine A?
