well whats going on guys? well as u know i blew my motor and now im trying to turn it into a beast...well i was reading about the rx8 e-shaft, and what is the benefit of putting a rx8 eshaft into a S5 tII rx7 motor and would it just fit in or would i have to get the staionary gears also?


thanks Marco

 

its lighter, and fairly cheap in price.


from Mazdatrix: These shafts are .6lbs. lighter than the earlier 13B shafts. The main journal diameters are approximately one-half thou smaller, and there is a one-half thou taper in the rear main journal.

Price: $193.59

 

If i recall there was a thread just recently discussing this. I can't really help you out because I was wondering the samething.

 

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/rx8-e-shaft-690841/

 

i know, i read this one already, but it doesnt state what a rx8 eshaft would do to rx7 motor, i want to know would it accelarate faster? torque? and would i need the rx8 stationary gears? thats what i want to know sir...

thank you Marco

 

Being that it's lighter it would have the same effect of switching to a lightweight flywheel, but it won't be near as noticeable, if at all. Switching to the lightweight flywheel, or to a much less extent, switching to this e-shaft, would allow you to rev faster since there is less weight to move.

I was thinking about this too, but I'm not sure it's worth the money for as little weight as it cuts down, and even moreso as little difference as it makes.

 

The RX8 E-shaft is .6 lbs lighter and I thought it was a bit stronger.

I am using one for my build up because its not that expensive and it does drop a bit of weight. Not much, but .6lbs is .6lbs. And when your a slow N/A, thats .6 lbs!!!

 

well im putting it in a s5TII!! does it matter that its going from a NA to turbo motor?

 

E-shaft is an e-shaft regardless of what motor S4/S5 TII or N/A.

The renesis is the next generation of E-shafts, but my guess is they didn't make it weaker. Since the rotors have a 1200 higher redline on the renesis, its probably stronger. So it should work with no problems on an S5 TII.

 

Yeah I think it is stronger actually, but that was never a weak point with rotaries anyway, so I'm spending my money on something that's going to make more of a difference. By all means, if I had money to throw around, I'd be going for the RX-8 e-shaft, lightweight rotors, the whole 9, but I don't at this time. Someday I do hope to run all that stuff though. Good luck with your builds guys.

 

beleive me, im not rich or anything, i just have a good job and still a college student...married with no kids....plus i plan on having the 7 running on febuary of 08....so ima put some money into it...

 

the Renesis rotors are lighter than any of the 13B rotors though, so the stressful forces on Renesis e-shaft IN a Renesis at redline may still be less than the stressful forces on it with 13B rotors at a 13B redline (which varies between years and TII/NA, I know).

 

Right, comparing though the redline on RX-8 is 9200, vs 8000 S5 vs 7000 S4. I think the lighter the rotor the higher RPM it can safely see. (barring ceramic coated and carbon blah blah blah)

 

well people have built race motors that redline at what, 11k, with FC e-shafts? I just think there's a lot more to consider than just the e-shaft.

 

It's only one pice of the puzzle. Just like when people say it doesnt make a difference to get a single exit exhaust or remove the ac. If you do all of the little stuff to make it lighter, it will help.

 

I remember hearing the Renesis e-shaft can be found at a lower price than a 13B e-shaft, so if you need another e-shaft I don't any obvious reasons why you shouldn't go with the Renesis e-shaft...

but just for .6 lbs difference? ...you can lose or gain a few pounds of water in just a day, I don't see .6 lbs making a noticeable difference unless you can find 50 other little things that weigh ~.5 lb to remove...

 

.6lbs of rotating mass is alot different than .6lbs of static weight.

 

Most of these I am willing to bet are ceramic coated and ultra lightweight rotors.

 

but its all in the center!

if you're on a budget, the eshaft rarely wears out, it would be better to spend the dollars in rotor housings, or balancing or an ecu, than it would be to save half a pound on the rotating assembly.

however if you need an eshaft, or already have a really really tight well built engine, then rx8 shaft is the way to go

 

Exactly.

The effect of the weight reduction is directly proportional to the distance the weight is from the centerline.

Reducing the weight from a large diameter object like a flywheel will have a noticeable effect.
Reducing a small diameter part like the eshaft will have much less...in fact, I would posit that you could never tell.

If the newer shaft is better in some other aspect then go for it, but I don't see how it could be justified on the basis of weight reduction alone.

 

The loads seen inside an engine are HUGE. Given that stress on a rotating object is not calculated in a linear fashion, any amount of weight savings on reciprocating mass is sure to pay big dividends with regard to engine durability and high RPM operation. Safer higher RPM operation means more horsepower, and more hp means faster acceleration.

 

read what was just said about forces being more dependent upon the distance from the center of rotation. it was correct. that said, having a more solid e-shaft may actually take those forces better. if the Renesis e-shaft is stronger than FC e-shafts for high RPM applications, then it's because of the material and or process of manufacturing and not because it's lighter.

 

Some of what restricts RPM is balance IMO. .6lb less rotating mass means .6lbs of mass that isn't potentially unbalanced. And because of the RX-8's higher rev limit, I would imagine Mazda put more work/technology into balancing them properly. So, with a front/rear stat gear and e-shaft... It SHOULD be a direct swap. Though nothing beats having your entire rotating assembly professionally balanced. E-Shaft, Rotors, Counterweights...... Its just f-ing expensive.

 

Oh, by no means was I trying to say you were rich or snobbish or anything like that. If that's something you want to get, I wish you the best of luck my friend. I was just saying it's not for me right now.

I didn't know the RX-8 rotors were lighter too. That might change my mind a little, haha. How much lighter are we talking? My current e-shaft is in good shape but I'm currently looking for rotors anyway. I probably still won't have the money for a new set though, and I highly doubt someone would be selling a used set already, haha.

This is exactly what I was getting at. You'd tell more with a lightweight flywheel than you would with a lighter e-shaft.

clokker, I thought your avatar was Tom Servo for a minute, haha. I've had MST3K on the brain lately.

 

There is no real gain to use RX-8 Rotors in a 13B over S5 N/A rotors. Plus the design is a bit different because of the side exhaust.