Hi all,

Well my question is a bit confusing but l hope u guys can help me in this. Well as ya all know that we dont usually use high compression rings in turbocharged applications so what exactly is high compression ring??? is it the ring itself or the timing of piston e.g if CR in 8:1 then doest that mean that piston ignites the mixture when its 1/8 at top dead centre???

Another confusing thing is that more high compression rings mean more combustion trappage so why we ignore high compression rings and use the lower compression ones????

And do we need to change timing accordingly...

Thanks a lot....

Guide me in detail......thanx

The compression ratio is determined by the amount of space left in the cylinder when at top dead center. The ways this is controlled is by the final deck heigth & the volume of the combustion chamber in the head. It is not the rings, but most often either the head itself, the piston & or rod length.
Higher compression engines need higher octane fuel, or more timing advance. They also must have tighter manufacturing tolerances.
So lower compression engines can use cheaper fuel & due to allowed variances cost less to make.

While the last answer is correct, if you add a turbo, you will need higher octane fuel on a lower compression engine too. Still, if driven moderately, a turbo set up could actually give you higher mpgs than higher compression rings while offering equal or greater torque. Sure it is more complex, but your engine wo not have to work as hard to do the same job.