compression

[lcp8410]

anybody have a better thougth what is the safe maximum compression ratio running with straigth alcohol? hope to hear from your experience.best regard roy.

[sam]

Varies dramatically from motor to motor and design to design ... as well as with different porting, pistons and combustion chamber size and shape. Its like choosing the best dog. You don't take a Chihuahua bear hunting or use a Great Dane for mousing.

Generally 18:1 is the maximum I have seen, but that may be excessive for your particular motor.

[lcp8410]

opinion.....

sam, i have this 71mm bore and 61mm stroke 2 cylinder outboard with stock 7:1 compression maximum operation range 4500-5500.if i run straight on alcohol then what is the compression ratio will u recommend?best regard roy.

[sam]

That is not enough information about the motor

[DeanFHobart]

How fast do you expect to go ?????

[lcp8410]

70mph

i love to see an avarenge top speed of 70mph.the motor have single carburetor,stock leg, stock port timing,ligthening flywheel and stock ignition.motor running on a ligth weigth tunnel with 10"x18" chopper prop and repeatly hit 60mph reading on gps.i was a bit confuse as i learned that correct compression ratio is needed for certain fuel chioce. but how can compression ratio tolerance with different port timing,rpm range,exhaust system,and speed range?anyone? regard roy.