We were doing some balance comparisons using a special arbor made up exclusively for testing Mazda flywheels and counterweights and found that the amount of counterweight is different for the automatic than the manual shift. This should be a huge concern for those using an aftermarket flywheel/counterweight combo for their RX8. There is no properly balanced counterweight for it from Mazda. The counterweight will have to be custom balanced. I don't think it is common knowledge about the counterweights since the amount of counterweight balance was always consistent on RX7 from manual to automatic. Mazdaspeed indicated that the RX8 uses different eccentric shafts in the auto than the manual. This must be where the different balance requirement comes from since they apparently use the same rotors. More flywheel info: The RX7 Turbo and RX8 use the same aftermarket flywheel (with different counterweights, of course).

 

Something to keep in mind.

Any ideas as to weight difference between the auto's and manuals?

 

The manual shift has less out-of-balance than the automatic. I am sure it is enough to shake your bootie and potentially do some real damage to the rear e-shaft bearing. I don't have the figures in oz.in. handy but it is defintely significant. The testing was done at a friend's shop that has the special arbor.

 

I bet that is why Unorthodox Racing is making the flywheel with their own counterweight bolted into the flywheel.

 

I doubt it but I will give them a call to let them know about the balance problem just so they don't have any issues. It is just as easy to match balance to the flywheel as it is the counterweight as long as you know to do so.

 

Counterweights are not consistent with all RX-7s. Third gens for example use a different front counterweight between auto and manual. It's weighted kind a funky.

 

That's interesting. I will have to check the 3rd gen as well. I just assumed the balance was the same from manual to auto, since I know they have been treating them that way for years. You know what happens when you assume.