RX8 E-shaft vs 13B-RE/REW shaft

[vex]

More food for thought (or fuel for fire)

[joff]

Originally Posted by vex

More food for thought (or fuel for fire)

Where'd this figure come from and would you mind explaining?

I assume these are the forces on the stationary gear that would otherwise cause it to twist? How is this relevant to E-shaft loading? I'm just a genuinely curious lurker -- have no credentials for an opinion, and no data points to offer so feel free to ignore...

[REVIT93RX7]

You're just missing the point. But I think what we need here is more data. The more people that use the parts from the 8 in the 7 the more we can learn. My only thoughts here was whether longevity was an issue for you or not. So I for one would like to see some success with these parts. FD engine parts are becoming very expensive. The more parts the better. So let us know how succesful you are with this setup.

[joff]

Originally Posted by REVIT93RX7

You're just missing the point. But I think what we need here is more data.

I agree more data is always good, but I think Glen has a very unique and valuable perspective here -- he actually broke one and followed up with Mazda to understand why and found something very interesting about tempering that has not been brought up before and should not be forgotten.

The facts I didn't know that I've gathered from this thread:
1) RX8 e-shaft is cheaper than RX7 one
2) RX8 e-shaft is lighter.
3) RX8 e-shaft was designed for a car that makes much less torque than the RX7 ever made.
4) Mazda does not temper the RX8 e-shaft, but does on the RX7 one.
5) An RX8 e-shaft has been broken by a prominant engine builder.
6) Tempering, as an extra step in manufacturing, inevitably adds cost.

Fact #5 proves that whatever was the particular failure mode experienced in Glen's build, in that particular instance the RX8 e-shaft was the weakest link.

Fact #6 brings into question the presumption that the RX8 eshaft is cheaper because its newer, as being cheaper because its cheaper to build actually makes more sense when it comes down to it IMHO.

Wikipedia has this to say about the process characteristics of tempering. Apologize if everybody already knows this, I personally did not:

1) Improves ductility and toughness
2) Reduces cracking
3) Improves machinability
4) Increases impact resistance
5) Improves malleability

#4 seems especially like something that might be good for anything inside an internal combustion engine.

[vex]

Originally Posted by joff

Where'd this figure come from and would you mind explaining?

I assume these are the forces on the stationary gear that would otherwise cause it to twist? How is this relevant to E-shaft loading? I'm just a genuinely curious lurker -- have no credentials for an opinion, and no data points to offer so feel free to ignore...

It's from an ASE article regarding the 13B engine from an FD. Loads exerted on the stationary gear play a very large role in an asymmetric loading of the eccentric shaft. Since the loading appears to be greater than what the eccentric shaft sees on the bearing load. This means that a majority of the deforming load applied to the stationary gear should see abnormal wear when you have a case similar to Glenns. This is assuming that an abnormal ignition event caused the initial deformation of the shaft.

The actual title of paper is "Recent Technology Development of High-Powered Rotary Engine at Mazda" by Takumi Muroki.

It also has an interesting portion about timing and the propogation of the flame front depending on the location of ignition (10* EW TDC, 20* EW TDC, 30* EW TDC).

[joff]

Originally Posted by vex

It's from an ASE article regarding the 13B engine from an FD.

I figured it must have been from SAE -- I wish those papers were cheaper than $15 an article. Thanks for sharing and attempting to accomodate a newbie, but I think I'll still need to read the full text to really understand whats being said here. :-)

[vex]

Originally Posted by joff

I figured it must have been from SAE -- I wish those papers were cheaper than $15 an article. Thanks for sharing and attempting to accomodate a newbie, but I think I'll still need to read the full text to really understand whats being said here. :-)

I swear I have portions of dyslexia or something, I screw up so many acronyms.

[Chadwick]

Not to discount Glen’s findings as I respect his knowledge and personal experience, but seeing how my name was brought up I figured I should respond.

The RX8 shaft has been in my car since March of 08 and has consistently been spun to 9k RPM and seen above 300 lbs rwtrq. We pulled the motor apart a few months ago to try out the ALS apex seals and the front and rear stationary gears show no signs of wear and the shaft is still like new. As a mater of fact, most of the bearing babit was still there. I would estimate at that time the motor had close to 30 races on it and around 400 street miles. Now the motor has around 40 races on it and another 600 street miles and is still going strong. At the most resent ProSolo we gave last years National Champion in a 500+ rwhp, single turbo, 3 rotor a good run for the money.

I have plans at the end of this race season to drop this motor in my street car and build a new one for the race car. The new build will be using the RX8 eccentric shaft along with a few other tricks to reduce the rotating mass. Time will tell, but at this point I see no reason to go back to an REW e-shaft.

Dan

[MOBEONER]

when you guys use the rx8 eccentrics do you also get your rotors lightened as well or do you just swap eccentrics?
I am rebuilding my engine in November just to freshen it up. Its reading 15psi vac right now and i would like to rebuild it and i am interested in the rx8 eccentric.

[730RWHP12A]

Originally Posted by Chadwick

Not to discount Glen’s findings as I respect his knowledge and personal experience, but seeing how my name was brought up I figured I should respond.

The RX8 shaft has been in my car since March of 08 and has consistently been spun to 9k RPM and seen above 300 lbs rwtrq. We pulled the motor apart a few months ago to try out the ALS apex seals and the front and rear stationary gears show no signs of wear and the shaft is still like new. As a mater of fact, most of the bearing babit was still there. I would estimate at that time the motor had close to 30 races on it and around 400 street miles. Now the motor has around 40 races on it and another 600 street miles and is still going strong. At the most resent ProSolo we gave last years National Champion in a 500+ rwhp, single turbo, 3 rotor a good run for the money.

I have plans at the end of this race season to drop this motor in my street car and build a new one for the race car. The new build will be using the RX8 eccentric shaft along with a few other tricks to reduce the rotating mass. Time will tell, but at this point I see no reason to go back to an REW e-shaft.

Dan

what class did you run ?