Compression question

[tblshur]

Does higher compression mean more hp or better performance thanks for replys

 

[dingbat]

Does higher compression mean more hp or better performance thanks for replys

No...compression isn’t a function of HP or performance.

Typically, compression higher than normal is an indication of a problem

 

[achris]

Does higher compression mean more hp or better performance thanks for replys

If you are referring to higher compression as designed, generally yes, more power, but it's not JUST compression. It's all about balancing all factors, compression, cam timing, valve size and lift, combustion chamber design, port size and shape. Even the exhaust system needs to match the rest of the build.

Chris.....

 

[Scott Danforth]

Does higher compression mean more hp or better performance thanks for replys

without context as to your thoughts, we cant answer any more than above

so, lets ad some context to your question

are you planning on building a motor?
buying a motor?
have a buddy with a motor laying around in his garage from a 1984 truck and you arelooking to buy?
general question?
you have an issue?

Help us help you.

 

[tblshur]

sorry i didnt explain i have a j140tlcte which had ring failure mechanic sent the head to be fixed i think bored he put new pistons & rings switched heads i found out later to used low compression heads . when the rings failed originally three cylinders had 120 psi now all 4 have 95 96 96 98 boat runs what i think is pretty good just trying to get a understanding of the compression difference sorry to take up your time for just trying to understand i do thank you all very much for your responces:joyous:

 

[F_R]

All other tnings being equal, lower compression does lower the horsepower. Otherwise, why would anyone use high compression heads, etc? Also a related fact, high compression requires higher octane gas to prevent pre-ignition/detonation---the most common reason for decreasing compression, and possibly why your engine blew pistons and rings..

 

[oldboat1]

Because (and this is the really cool part), higher octane fuel actually burns/ignites slower than lower octane fuel.

 

[rothfm]

I wouldnt particullarly worry about those numbers. had a similar year 140 with similar numbers and ran great. Also had several 150's with 85-90's, was in fine shape and ran years for me very strong motor.

 

[achris]

2 strokes generally have a much lower compression than 4 strokes.

 

[robert graham]

2 strokes generally have a much lower compression than 4 strokes.

That's because the compression ratio on a 2 stroke is measured from the point that the piston rises above the ports to top dead center....my old C90 2 stroke Yamaha has 3 pistons and each cylinder has a slightly different ratio, cylinder 1 is 5.76:1,
cylinder 2 is 5.67:1, cylinder 3 is 5.86:1......but the motor makes 90HP from 69.6 cubic inches, so in my old hot rod days any motor producing more than HP per cubic inche was fairly highly tuned....you just can't compare 2 strokes with 4 strokes,....2 strokes making twice the power strokes per RPM....

 

[tblshur]

i truly thank all you guys for info i feel ive learned alot and i am satisfied with my motor it has taken me fishing many times and brought me back in the 5 or 6 years thanks and have a good day:joyous: