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

[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. :-)

[FreeLance]

Back up top! I'm going to be using the rx8 e-shaft in my newest build and I'm just wondering if anyone has any updates. I respect ALL opinions in this thread but am always open for more data or experience.

[Buggy]

I have the Rx-8 shaft in my Rx-4's engine along with the Rx-8 stat gears and bearings. This is an NA setup mind you so I'm not really pushing these parts to their limits. I've got probably around 6000 miles on this engine with no problems of any kind. Runs great, still builds good power and wicked oil pressure. I don't know if there is any real significant gain to going with the 8 shaft, but lighter is lighter and cheaper is cheaper...... Those were good enough reasons for me.