Generation IV Internal Engine - WHAT COMPRESSION on 93 fuel !
05-09-2012, 12:36 PM
I was planning on building my motor about 11.8 to 1 compression for 93 octaine fuel...well a pretty reputable guy around here said he would go 12.5 to 1 because the cam is going to lower it anyway, has anyone ever heard about safely running that much compression on pump gas
05-09-2012, 01:14 PM
I think 12 to 1 is pretty doable. But arent you going turbo?
05-09-2012, 01:18 PM
That depends on the cam and the valve timings. What is going to be the DCR after the cam is a better question.
05-09-2012, 02:25 PM
Watch this video of me running my oldest sons Firehawk. My motor is 12.7 to 1 and was running on pump premium. I had my timing slowed down to 28 degrees total. You will probably have to slow yours down a lot too but it does work.
05-09-2012, 02:38 PM
You can run that much compression on pump but not really to race on. If your cam is big enough it will bleed off compression just cruising but when you start to turn some rpm the compression will start to build and then you won't have enough octane to control the compression and then BOOM!
I would just stay right at 11.8-12 like you are doing. My buddy has a 12.1:1 LSX 451 and he daily drives it on pump 93. IMO I would stay at 11.8.
05-14-2012, 01:46 PM
It might be a good idea to search around for a dynamic compression vs static compression calculator. The static compression ratio may be "too high for pump gas," but depending on the cam you may have relatively low dynamic compression which would make pump gas more feasible.
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