3 replies to this topic

[Ministage2]

Hi Folks

 

In addition to my earlier posts about my stupidity regards my stage 2 head tuning issues.

 

Ive heard high and low compression engines mentioned.

 

The rolling road guy said something about high and low compression engines??? 

 

whats he on about?

[miniman24]

High compression engines have higher compression Not sure about large bore engines but with 998's its to do with the dish in the piston - earlier engines had dished pistons (about 6cc dish I think) which lowered the compression compared to the later flat top pistons.

[jakejakejake1]

They are referring to the compression ratio of the engine, generally the higher the compression ratio the better as it will be more powerful if nothing else changes. But there are limits to how high you can go.

As mentioned some engine had dished pistons which reduced the compression ratio, or flat top pistons which had a higher compression ratio.

[Stu1961]

Any number of things can be done to change the compression ratio, usually people are looking to increase it. I think it's basically the cubic capacity of one cylinder divided by the volume of the space above the piston when it is at top dead centre.