Pump Gas Compression?
#1
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I'm just trying to figure out how much compression I can safely run on pump gas. I know that the bigger the cam the more you can get away with, to an extent. I also know that there is a point to where you have to take so much timing out to run it on pump gas that the power gain made from the extra compression is out weighed by the power loss of low timing numbers. I have not decided what i am going to build yet, but I am sick of going slow.
P.S. we only have 91 up here
P.S. we only have 91 up here
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Last edited by whyt00; 05-20-2011 at 09:29 AM.
#2
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The combustion chambers on these engines are very efficient... I used to run an LS1 on 87 octane (factory 10.1:1 compression) all the time and the computer never pulled any timing. Before that I had an LT1, which had 10.5:1 and would ping all the time on 87 and about half the time on 89 (starting around 1/2 throttle under 3k rpm) even with the reverse cooling and 160* thermostat. Gen III+ chambers are a much better design than the old SBCs and much more detonation resistant as a result.
If you run 91 all the time I don't see 11:1 being a problem at all. I kinda remember a lot of LS1s back when I was still in the F-body game running 10.8-11:1 compression on mid grade without problems.
If you run 91 all the time I don't see 11:1 being a problem at all. I kinda remember a lot of LS1s back when I was still in the F-body game running 10.8-11:1 compression on mid grade without problems.
#3
#4
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I'm at 11:1 in my truck and I have no issues. I'm putting together a turbo kit right now as well to run on my current setup. You can get away with a lot if you have a good tune.
#5
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As you mentioned about the cam, you can run a lot of static compression if you keep your dynamic compression ratio within check. A "bigger" cam with a lot of overlap will help give the cylinders a natural EGR effect and bring your dynamic compression ratio down. If you want to squeak a little more out of it, make sure that your EGR system is operational as it will actually bring cylinder temps down and help prevent pinging.
#6
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I was really hoping to get 12:1 I really want to get as much naturally asperated horsepower on pump gas as humanly possible, and then spray the crap out of it
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