Hi,

As the title says, what causes good or bad compression in an engine, what are the most import factors?

I have searched but couldnt find.

I know that the apex seals are the main factor, but what more causes a high or low compression, Corners seals, sideseals, out of spec housing??

Anybody care to shed some light in here?

Regards
Rogier

 

good compression is caused by an engine that has good sealing qualities in the rotor housing ie porperly worn in seals and that kind of thing. and a low compression engine would be caused by worn out seals ie small cracks or depressions in the seals.

 

So you mean all the seals, or mainly the apex seals?

 

All the seals together, and also the springs.

Only thing is, when apexseals are damaged, you lose more compression then when a side seal is worn or damaged. but that is logical if you look at the design.

 

You forgetting to include carbon sticking of the seals which is the biggest contributor to low compression. Stuck seals will always keep the engine from making full compression.

 

The compression will only be as good as the weakest link in the combination of seals, springs and the surfaces that make up the chambers inside the engine. Primarily the apex seal not sealing good on the rotor housing surface will cause the most dramatic loss of compression.