12.5 compression with 93 octane?
Thread Starter
Staging Lane
Joined: Mar 2005
Posts: 81
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12.5 compression with 93 octane? would it be safe to run 12.5 compression on a ls1 with 93 octane? i originally came from the honda world where high compression helped our little 4 bangers keep up with and beat v8s.
what is the highest posibble safe compression to run with 93 octane? with tunning of course.
what is the highest posibble safe compression to run with 93 octane? with tunning of course.
It comes down too many factors. Can 12.5:1 on 93 be done? Yes. It's very doable if you know what you're doing, but cooling, coatings, quench, chamber design/shape, and camshaft will play a big role. I'd advise to use Evans Coolant and Waterpump also.
Originally Posted by MUSTANGEATER
It comes down too many factors. Can 12.5:1 on 93 be done? Yes. It's very doable if you know what you're doing, but cooling, coatings, quench, chamber design/shape, and camshaft will play a big role. I'd advise to use Evans Coolant and Waterpump also.
Be careful with coating though. I still have to do some research in this department. Some say they help prevent detonation some say they contribute. Since they essentially trap heat in the combustion chamber they may contribute to detonation unless you have a super super efficient cooling system (Evans Collant as pointed out before). One thing is for sure, the thermal coating make more power (if detonation is not a factor) as they keep the heat from transcending into thermal loss. In other words the heat is converted to mechanical energy (hp) much more efficiently then without the coating. Coating may help fight detonation though if they are extremely smooth helping to prevent any hot spots.
What kind of motor are you building? Tell us more about your plans.
Thread Starter
Staging Lane
Joined: Mar 2005
Posts: 81
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from experience, high compression is favorable in order to run aggressive cams.
im planning on building an NA machine with gen3perf individual throttle bodies and 12.5+ compression with custom cams on a 427 short block.
im going to be doing more research. i dont want to go to the turbo route because i would rather have the ability to say i run x seconds and still NA. less maintenance i think also.
im planning on building an NA machine with gen3perf individual throttle bodies and 12.5+ compression with custom cams on a 427 short block.
im going to be doing more research. i dont want to go to the turbo route because i would rather have the ability to say i run x seconds and still NA. less maintenance i think also.
TECH Enthusiast
Joined: Apr 2003
Posts: 561
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From: silver Spring MD
Hi Folks
I am running 11.2:1 compression and don't have any problems. If there is a problem, the computer will take over, retard the timing and other things. If it detects some knocks (knock Sensors) because of low octane or bad gas and it will do its thing – save your engine.
Bill
I am running 11.2:1 compression and don't have any problems. If there is a problem, the computer will take over, retard the timing and other things. If it detects some knocks (knock Sensors) because of low octane or bad gas and it will do its thing – save your engine.
Bill
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
FWIW I have never seen any good running car thats really a street car run that much. Maybe 11.50 but that's it.
If you have good VE and you should if you have good TQ and power than you should also have very good cylinder filling.
If you have good cylinder filling then you can only squeeze that high density charge so much before it goes off on it's own in the form of detonation, preignition etc.
So if you have extremely bad cam timing that reduces VE or really terrible heads or you are running more or a very large cam that closes the intake very late to make more high rpm torque you can run more compression also. Also if you have a lot of intake restriction suck as a very small throttle body the compression might help on the top end but will still make you detonate through the middle. The Evan's coolant could also let you run a little more but unless you want to be the guinea pig don't push it too far!
I don't ever advise going crazy on compression on the street since I have to fix so much of that kind of stuff and it also has so many problems breaking stuff especially down south where it gets really hot in the summer and people are stuck on the freeway with the AC blasting and the engine near meltdown!
If you have good VE and you should if you have good TQ and power than you should also have very good cylinder filling.
If you have good cylinder filling then you can only squeeze that high density charge so much before it goes off on it's own in the form of detonation, preignition etc.
So if you have extremely bad cam timing that reduces VE or really terrible heads or you are running more or a very large cam that closes the intake very late to make more high rpm torque you can run more compression also. Also if you have a lot of intake restriction suck as a very small throttle body the compression might help on the top end but will still make you detonate through the middle. The Evan's coolant could also let you run a little more but unless you want to be the guinea pig don't push it too far!
I don't ever advise going crazy on compression on the street since I have to fix so much of that kind of stuff and it also has so many problems breaking stuff especially down south where it gets really hot in the summer and people are stuck on the freeway with the AC blasting and the engine near meltdown!
I agree with Darpsuprslo and Erik on this. I wouldn't build a high compression pump gas car for a daily driver, but that's just me. You'll have to have a working system of parts to get this thing right. Don't pay attention to your static compression, dynamic is the key. I don't think you'll find many "LS1 builders" on here that would try the 12.5:1 system due to the liability, however there are plenty of guys who do build high compression pump gas street motors. FWIW I'm building a 12.5:1, 93 octane, 348 CID
Floyd.
Floyd.
