What causes low compression? I have heard that wear on the apex seals causes it and I have heard that carbon build up does too. Anything else? I mean my engine has been rebuilt so I don't think there should be a problem with either.

 

The APEX seals between the rotor housing begin cracking and eventually will pop out or be sucked into the engine. Your compression drops as the seals leak more and more air - and this doesn't really effect HP.

Measuring the compression lets you know how the seals are doing. 3 numbers per rotor for the 3 sides of the housing. When you have low compression you can avoid popping the engine by completing the rebuild including APEX seals.

One day I'll actually do this and have more insight in the seals.

 

So low compression doesn't lead to a loss in HP? What about an oil leak?(I've got one of these)

 

There's oil seals I believe that should be changed. Check the mazda service manual for the specifics (online or buy a copy).

 

I got a FSM on a cd that I can look at but I don't find it easy to navigate really. What oil seals are you talking about because I'll I've heard from people is I need a rebuild to fix it. Could it cause low compression anyways? Thanks.