BNA_ELLIS

Hi all,
I have a question with regards to the compression of an rx7 whether 2nd gen or 3rd gen. I have been wondering for sometime why it is that the rear rotor always gives lower compression readings than the front ?? In the event also of engine failure, a higher percentage of times the seals have gone on the rear rotor compared to the fronts.
Surely it can't be oil as the oil would be injected evenly to lubricate seals on both rotors, it can't be fuel either. With regards then to the 3mm 2mm apex seal debate as to which one is better, would it not then be better to have 3mm for the rear rotor as it has better durability, and 2 mm on the front which has better compression ??
Hope I've made sense!!

Regards

Brian Ellis

Tom Delegram

The lower compression on worn engines and the higher percentage of failure is most likely due to the higher operating temperature of the rear rotor vs. the front rotor. This effect is also seen in most multi cylinder high performance motors. In the world of sport bikes, in-line four cylinder motors have richer fuel mixtures for the middle two cylinders vs. the end two. If there were a way to richen up the rear rotor, this would make it run cooler and prolong its life

Tom