rx7swe

Does any of you use the 12,000rpm crankshaft on you rotaries? because I havn´t seen anything about it on this forum. Can a rotary engine really coupe with 12,000rpm?

BLUE TII

iTrader: (9)

Do you mean the Guru 2 piece e-shaft w/ center bearing?

rx7swe

yes it´s a shaft like that, but the spec on the one I mean says that it can go to 12,000rpm. How much rpm can the shaft you are talking about hold?

Mahjik

iTrader: (1)

What are you trying to do?

I'm just asking because it takes more than just a new/stronger e-shaft for running higher RPM's on these engines and I don't see you asking about those issues as well (so you either already know about them so you didn't ask or you don't know about them).

rx7swe

"Can a rotary engine really coupe with 12,000rpm?" I`ll make it easier.

How can a rotary engine coupe with 12,000rpm? And what mods do I need to make it?

Sorry if I was unclear...

BLUE TII

iTrader: (9)

When building a rotary to operate over 8,500 rpm the typical modifications made since the 1960s are in these catagories.

1. Balancing rotating assembly.

2. Clearancing of bearings and rotors to accomodate e-shaft flexing.

3. Oil mods to increase pressure and flow to bearings and rotors.

4. Apex seal that is lighter and less friction.

5. Oil and coolant cooling mods to shed more heat.

Race engines with these modifications are rarely operated over 10,000rpm.

Using the new 2 piece center bearing e-shaft you reduce the e-shaft flex so less clearancing is needed, but I would think the rest of the modifications will still be needed.

I don't think it is known yet what the high rpm reliability of the 2 piece shaft is yet.

RandomHero

iTrader: (2)

Is there even a port that will sustain power at that kind of engine speed? even peripheral ports on projects ive read about dont need to spin that high.

scathcart

6. Method of keeping the rotor gears in place, such as circlips. They tend to walk out and contact the sideplates above 10,000.

7. Engine studs or supported-center stock tension bolts. Sustained rpms above 8,000 rpm tends to snap unsupported tension bolts at the threads.

scathcart

Large pp-ports will.

peejay

Sustain? Yes.

Make more power up there than at a lower RPM? Maybe.

Accelerate as well as an engine that works in a more realistic powerband? Never.


If you want to twist your engine to 12,000rpm, set your tach up for a 3 cylinder. Then when your engine is really turning 9000rpm, your tach will be reading 12,000. And 9000 is really about as fast as you really want to turn a rotary, no matter what you have for porting.

Mahjik

iTrader: (1)

8. $$$$$

scathcart

That doesn't twist the engine to 12,000 rpms, that twists the tach to 12,000 rpms.

BLUE TII

iTrader: (9)

9. Lightening rotating assembly.

10. Lower friction coatings.

peejay

Given that there's nothing really useful about spinning that high (at 12,000rpm you have twice the rotational inertia as at 8500, and it's damned high at 8500 to begin with!) other than generating *****-envy and reducing the lifespan of your engine, it is much more productive to simply keep the tach over-calibrated. That way you can tell people you shift when the tach says 12,000, then they try to run their engines that high and trash engines left and right and compromise their portign to the point where they have a knife-edge powerband, while you keep on truckin' and win the races.

scathcart

I didn't say I thouyght revving that high was a good thing... I'm saying a miscalibraated tach still doesn't count as twisting the engine to those rpms.

I can think of very few engine/chassis combinations where revving that high would be of any aid in getting down the track faster

Curtisleeyoung

What is all this talk about the guru 2 piece e-shaft?

12at

Go to www.xtremerotaries.com and have a look for yourself.

rx7swe

So the 12,000rpm thing is nothing to go for then unless you wanna buy alot of mods.
Here is a pic of the e-shaft that I´ve been looking at. It looks like a one-piece shaft and not like a two-piece like guru´s.

Since these e-shafts are lighter than original the engine should rev faster an possible make more hp.

Thanks for all good info so far

Curtisleeyoung

Where is that 12k e-shaft from? you said it's lighter?

ronbros3

I think I said this before, the stock mazda e-shafts are made from a 1020 type of steel and they are machined from billet stock then induction hardend on the bearing surfaces only. I say a race shaft for performance engines should be forged into a shape like the original, from 5140 steel then machined to final size and chemically hardend on its complete surface. why! look at all the work we put into a stock shaft to make it so the rotors dont touch anything, thats very poor engineering,and the ROTORS, i got flamed bad on this one, should be ,for performance purposes, should be cast from a hi quality material such as inconel or lighter yet , titanium. a light weight rotor would put a lot less FLEX on the E-shaft

ronbros3

also I do know of a mazda in orlando fl. turning 11000 on launch, and thru the traps at 11500 rpm, works for him!

Curtisleeyoung

makes sense, but the part about "look at all the work we put into a stock shaft to make it so the rotors dont touch anything, thats very poor engineering" I dont quite understand what it is your saying.

BLUE TII

iTrader: (9)

Poor engineering-

To run at high rpms with the attendant e-shaft flex the rotors are given more side clearance and the bearings are run with more clearance so when the e-shaft flexes at high rpm there is no metal to metal contact.

This is poor engineering as proper engineering for high rpm capability would be to try to eliminate the root of the problem- e-shaft flex.

Kenku

All this talk of engineering... anyone ever stop to consider that, maybe just maybe, a 2-piece eccentric shaft would impose all sorts of manufacturing difficulties? Yeah, poor engineering to design a part so you can mass produce them.

And titanium's still not all that great of a material for rotors. Neither is Inconel. There's better materials that are cheaper and easier to work with, if you want to go to the trouble of casting your own rotors.

Curtisleeyoung

I understand what your saying now, and completely agree.