Reply With QuoteWhat motor?? Get a book called Small Block Marine Performance or Big-Block Marine Performance. It explaines all the issues involved with compression & HP in marine motors.
Can anyone tell me the correlation between compression ratio to horsepower assuming everything else is equal? For instance How much increase in horsepower will you see in an engine if you increase its compression ratio from 9:1 up to 10:1 and again up to 11:1. Is there a rough rule of thumb. I understand that at a certain point you go from pump gas to Higher octane fuels, but actual dynamics aside is there a rule of thumb?
What motor?? Get a book called Small Block Marine Performance or Big-Block Marine Performance. It explaines all the issues involved with compression & HP in marine motors.
One of the Car magazines currently on the newstands has a good article on compression ratio vs HP. They used a 440 Mopar as the test mule. I think it was Car Craft or Hot Rod
Hey fired up, Bob is right about the magazine article.It is in the January issue of car craft.There is some factors regarding combustion chamber design,Type of piston,and if its aluminum or Iron.PQ208 made a good point about displacement.I think cylinder volume,Small blk/Big blk,have different characteristics. My friend has a 468 with canfield aluminum heads and is running 10:1 compression on 92 octane with a solid roller cam.He runs 32 deg.advance wth an msd crank trigger.I have a number you can call for an expert opinion.Call (920)685-3000 ask for todd.He owns Goodwin competition and is really into marine engines as well as everything under the sun.Tell him chris sent you.I was at his shop yesterday and he has 8 allstar 708 cu in motors in different stages of competion.You guys should see these things!They are capable of a max displacement of 998 cu in.Te best thing about this guy is he take the time of day to explain even the most mundane details.I am no high roller,and he treats me as if I am.
In an article I saw several months back in a car mag, they were talking about varying compression ratios and said "rule of thumb" you change HP about 3to4 percent for every point you raise or lower your ratio.
The rule of thumnb is, you lose 4% of horsepower for every decrease of one point in your compression ratio.
Going from 9 to 1 will net you more power than going from 10 to 1 to 11 to 1 ect. providing everything else remains equal. The diminishing return law applies here.
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