My 2004, 79,000 mile RX-8 recently failed the compression test, but only one rotor seemed to be bad (6.6 for R1, 8.0 for R2 at 270 rpm).

Why would only one rotor wear out and lose compression? Shouldn't they wear evenly? Is R1 more vulnerable for some reason?

Or more importantly, did something specific happen that I can prevent happening again with the new engine?

 

Likely lost a side seal spring in the low rotor.....depending on what the other numbers are for that rotor

It is normal for them to fail like that.....if they are wear only..they will drop more evenly

Doesn't seem like wear is the biggest factor in these engines failing

 

All faces almost identical...

R1 6.6, 6.7, 6.5
R2 8.1, 7.9, 8.0

So the potential problem lies within the rotary itself, and not in... oh I dunno... a line or hose or something that goes to only R1?

I just want to make sure I minimize the possibility of an early failure again... we don't often get second chances in life!

 

Did they do a de-carb? sometimes the numbers will look like that if the seals get all carbon crapped up

I would try a good sea-foam or cleaning and see what happens

 

I don't think so, I think they tested it first, and once it failed... that was that

So what would cause a side seal thingie to fail? Is it just inherent in the original design that some fail early? Or would a different component not working properly cause the side seal to fail early?

 

Basically a crap shoot I don't think there would have been anything you could have done differently

The latest versions of the motor and the new rebuilds are using a new side seal spring..time will tell if that will help in the long term failure rate

 

Even Series I rebuilds like mine will be?

 

I believe so......

 

FWIW, the way the coolant flows thru the rotor housings could have an impact. The coolant will always be hotter for one rotor.