the FC's all used the same e shaft. the different rotor weights are balanced with different counterweights, NOT with different e shafts.

 

if you look up the bearings, the FD and high power rx8's use the same part number bearings.

i cant explain how the oil galley moves but it uses the same bearing, except that the rx8 front and rear irons are wider for the new ports, and maybe that moved the stat gears a bit?

 

someone had one at sevenstock, that was bent, and cracked, in addition to damage from a bad bearing.

 

This is incorrect, taper was added to both front and rear journals. Each journal is .0001" smaller near the end of the shaft.

FD bearings may fit the same as the RX-8 bearings but S4 and S5 bearings will certainly have the wrong clearances.

I'm personally not going to worry about using an RX-8 e-shaft in my N/A street car because a person or two has bent one, and who knows what they where doing to bend one. Not to say that testing the hardness of them isn't important but I doubt it will be a problem for most people.

 

.0001" is not enough to matter. The e-shaft itself changes size way more than that just based solely on temperature. In fact you could measure a cold e-shaft and a warm one and get a larger variation than that. I don't trust that number and either way it's not enough to do anything useful.

The bent shaft was on a turbo car. I have yet to see one bent on an n/a.

 

Rotarygod

Any information on what kind of power the turbod car running that rx-8 E-shaft was putting out?

 

Just to add from personal experience on this. My half bridge was built using the rx8 shaft.
Now I did it because :

One, the price was excellent to obtain a brand new eccentric shaft in my motor.
Two, I was getting my balanced anyway, so all things fitted just right (no extra cost for the "upgrade" other than buying a 200.00 shaft.

The only mods that were done to get the build completed with the shaft was to silicone the rear stationary gear grove so that it didn't leak.(there is a rubber seal on the rear stationary gear that you don't use anymore).

Ok, now 5 months later and god damn close and over 550whp, I've had no problem with my motor. This is a street car, so it does get some wear and tear.

To add to this thread, I will be pulling the motor to replace seals to the NRS brand and will be going over the shaft with a fine tooth comb. I can take some pics if they are abnormalities on the assembly, which I doubt, but who knows...

If everything is great , I will be going ahead and putting this motor back together and going for some more power..more than likely a 100+ more.

So I'll keep you all posted.

 

I'd want to give a medal to someone who could bend one in an NA

 

excelent this will really put the e shaft to the test, im planing to have similar power and am concerned about which shaft to use.

 

Currently there is no proof that the Renesis shaft is weaker. There has only been one bent as far as I know and it's the uncertainty as to why that is leading to them being tested. I'm just being cautious when I say not to use them. It doesn't mean anything will happen. Something has happened to one though and we don't know why yet and it's the fact that it's happened at all that is suspicious.

 

My measurements where taken on a Zeiss Contura CMM in a temperature regulated clean room at 68 deg F and 35-40" humidity. The shaft was left there overnight to stabilize. The facility was used to build $80k+ race engines the measurements I performed on that shaft where about as accurate as anybody on this forum could get and probably more accurate than the facility used to manufacture it. Granted I only measured the shaft I had in my possession and intended to use in my engine but that number was not reached with a micrometer in my garage.

 

IIRC, posts on the forum have said it was .0005 taper. Diameter or per side? I don't know..

 

You need to move the decimal point over one place. Front and rear journals are stepped .001" (.025mm).

When compared to an FD crank the differences are: stepped main journals, slightly larger diam front main oil gallery, larger chamfer on the rotor journal oil holes, 180g lighter in weight, and lastly much cheaper to buy new. All oil feed holes are in the same position.

 

All well and good, but the difference is so incredibly minute that it doesn't much matter in the real world. What does the shaft measure when it is being cooled by 180 degree oil and whipping and flexing around?

The factory is probably so super ultra **** rententive about clearances because they are trying to get the engine to run up to shaft-whippy RPM and still live under warranty on 5W20 engine oil. Most people who race use 15W40 or 20W50 or 30 or 40, and they run more oil pressure too. So the clearances aren't super critical as long as they're wide enough to prevent contact IF it happens.

 

Here at work our machine tolerances on our eccentric shafts (some of them weighing up to 20,000 lbs!) of .001"-.003". Depending on the time of year and temperature in the shop we can see up .003" of size change so we need to try to take this into account when machining them. Our target number may be at the larger end of the tolerance when it's cold or the other end of the tolerance when it's hot outside knowing it'll change size with temperature.

No one clearances their bearings on rotaries anyways so anything .001" or less isn't anything to worry about. Especially when you can buy bearings in different sizes. If you want to use a Renesis e-shaft in a 13B, go ahead. Just use a 3 window rear bearing. That's it. It works fine.

 

Nobody? I clearanced my bearings on my streetport, a few passes with a flap wheel in a drill in a bath of kerosene. How much did I remove? I dunno, but I took off a good amount of overlay.

It builds enough oil pressure to peg the factory gauge using a stock S4 N/A oil pump, anyway. And it hasn't come apart, yet, and I've zinged it right on up there a time or two

On the P-port I clearanced the bearings the hard way- with the eccentric shaft. Used silicone on the rear bearing instead of an O-ring. It prevented it from seating all the way, so the bearing was crooked. Whooops! Oddly enough, it didn't pose a problem, just wore through the overlay and part of the copper, still had great pressure...

 

When I think about the whole flex thing, the e-shaft does not bend only at the bearing. One has to think about ratios. The bearing is, well, I'm not going to the garage to measure one, but, only about an inch and a half long? Maybe two? Do a little algebra and find out what a total flex equals per inch.

Pick a number. .015" total center flex at 8k rpm? Center to center distance from bearing to bearing is, hell, I'm not going to the garage again, 12 "? .15 divided by 12 is .0013/in. times 1.5 equals .002.

I'm fully aware the bending is not linear, but, it sure supports the idea that .001 to .002 taper for that short distance could be beneficial. The added clearance would obviously demand a better oil supply.

 

But more oil pressure also keeps things in check, as well. Just enough.

An old time trick for making cast cranks live in stock block race engines was to run big bearing clearances, add a bunch of oil pressure, and run up to 70 weight oil. Nowadays with much better forgings and engine designs, we don't have to resort to that sort of nonsense. The Mazda rotary hasn't had any major design changes since 1967, it's been all detail work.

 

My friend, sburkett broke his RX8 e-shaft in half. https://www.rx7club.com/race-car-tech-103/broken-eccentric-shaft-533408/

 

It's no big brainer. THe rx-8 E shaft is 1lb lighter than a 13b e shaft. 1lb is a lot of weight/metal to remove from the e shaft, thus it is going to be weaker than the 13b eshaft. And since the rx-8 eshaft is not designed for a turbo application, I would hesitate to use one on a turbo car. There is a reason Guru makes a two piece e shaft with center bearing.

 

.6 lb lighter.

 

will a NON rx-8 e-shaft work with rx-8 stationary gears?

I already have the manual gears from an rx8, and was planning on using the 8's e-shaft. if decided not to use the lighter e-shaft could one use the traditional shaft with these gears?

 

I sorta asked this question in the second post of this thread. I "hear" they are windowed and hardened like the FD gears and come with bearings installed. I'm curious if I can run the FD thrust bearing without machining.

All I know for sure is the rear gear does not have an o-ring groove so it must be siliconed in. I've also heard the oil pasage does not line up well and a little dremel work is necessary in this area.

Everyone, feel free to add or correct.

 

Out of curiosity I hardness tested an RX8 crank and an FD crank.

RX8 journal = 60 Rockwell C
FD journal = 58 Rockwell C

RX8 center = 22 Rockwell C
FD center = 12 Rockwell C

22 Rockwell is about the hardness of 4340 so I think it's safe to say the RX8 item is made from better parent metal, and therefore probably less likely to 'whip' at high rpm.

Remember the Renesis engine is designed to rev higher than previous 13B's so one would assume Mazda allowed for this.

I'd be interested to see if Rotarygods results are similar.



RX8 stationary gears work fine with earlier cranks and/or rotors. The only mod required is to oval the rear gear oil feed hole with a Dremel so it lines up properly with the gallery in the rear iron. It only needs 2mm or so. I use them in place of 20B/FD gears.

 

12 Rockwell C doesn't even show up that low on the scale. You're into the B scale at that point. Those are soft as hell.