scathcart

I would balance the whole rotating assembly. There is typically quite an imbalance from factory, even on a matched set of rotors and counterweights. If you use a RX-8 e-shaft, they're usually pretty much spot on for balance and won't need any touching.

If you already have a balanced rotating assembly, and simply swap in an RX-8 shaft, you won't need to rebalance your parts. The e-shaft balance does not affect the rest of the rotating assembly balance.

PnoyRx7

iTrader: (3)

finally lol

nycgps

iTrader: (4)

then I feel really sorry about ur engine.

scathcart

Nothing like the ignorance of the inexperienced.

Liborek

Whats Your problem? I´m sure that "scathcart" has more experience around building high revving all motor engine than most people who posted here...

Shaft is balanced on its own. Counterweights are balancing rotors mass.

PnoyRx7

iTrader: (3)

this... plus i love all the butt hurt old folks around here

nycgps

iTrader: (4)

its a matter of opinion. it might work for you, but Im sure there are people out there with the same if not more experience will have a different point of view.

so no one can have their own opinion ?

CrispyRX7

iTrader: (139)

I just had a rotating assembly balenced by Roger Mandeville (don't know him? Do a search) and he said there is no consequence to swapping out the RX8 eshaft with the 13BREW eshaft - I build FD engines but have raced and built S4 and S5 NA engines. In fact he said not to waste my money in shipping him my RX8 shaft! That he would use an FD shaft he had in the balencing rig already. I sent it to him anyway because I had modified the oil ports but a stock RX8 shaft....don't bother. Since the rotaing mass of the eshaft is so close to the center of rotation it is of no significance relative to the delta found in the rotors and the counterweights. This considering the the eshafts are very well balenced from the factory to bigin with. The RX8 and 13B eshafts are interchangeable with respect to balancing the assm.
Regards,
Crispy

scathcart

Your "opinion" counters that of one of the leading engineers in the design and development of the Mazda 13B.

Laws of physics outweigh your personal beliefs everytime.

nycgps

iTrader: (4)

Im pretty sure I know the difference between the older shaft and MSP's shaft and guess what, even the difference is small & mostly at the center, there is STILL a difference.

and engineers can be wrong at times, Just look at RX-8, S1's RX-8 is a total mess, I thought engineers who designed the car knows best and can't be wrong? guess what, its all wrong. and they have to "fix" it in the S2. and take a guess who gave Mazda advise on what to improve and whats wrong with the original Rx-8 ? not the engineer themselves.

scathcart

I'll repeat this: the mass of the eccentric shaft does not affect the balance of the rotors and counterweights. I've posted proof of this. Until you can prove otherwise, keep your "opinion" to yourself, because its nothing more than false, unfounded heresay.

Saying that it possible for something to be wrong doesn't make it wrong. You have zero evidence that you're right other than "because you think so" or "someone else told me so".

Have you ever even had a rotating assembly balanced? I can honestly speak from experience.

nycgps

iTrader: (4)

Well I guess everybody who said you need to balance it is wrong then? Including Racing Beat? Mazdatrix ? Mazmart ? Hmm. Yeah, you're so experienced ?


Sure, so does that mean it cannot go wrong? hmm, oh wait, I did proved Mazda wrong. but that's something between me and Mazda. right ?

You can have your opinion, I can have my own, I don't have the stuff to balance the rotating assembly but so? I seen the action myself so yeah I know how it works and it depends on how much rpm you're going, for most street car, probably not that important, but if you do race sometimes and keep the rpms high, yeah you do need it.

Its ok man, I get it, you have the experience right? oh what do I know ?

jjwalker

Hmm, I really don't want to jump into this thread, but will with a short post.

If you take a perfectly machined shaft, with no lobes just a shaft and spin it, the rotating mass is at the centerline of the shafts radius.

An eccentric shaft obviously has lobes. These lobes are balanced to return the rotating mass back to the center of the shaft. Obviously it is not perfect, but close enough and within spec. No matter what degree of rotation I rotate an e-shaft, the center of mass is in the center of the shaft.

So no, you do not have to balance the RX8 e-shaft, assuming you are using correctly balanced rotors and counter weights. Adding rotors to the e-shaft moves the shafts center of mass away from center, thus you have counter weights to bring it back center.

If you spent **** tons of money, you could have your shaft and rotors balanced to spec and ditch the counter weights, but that is not COST effective on a mass produced scale.

nycgps

iTrader: (4)

well, I mean, I'm open to any opinion, cuz its your car, your money, you can do whatever with it, right ?

no point of getting it into a war. we all have one thing in common --- we love the 7, right ?

jjwalker

Not all of us are giving you opinions, yes, there are posts involving pure opinion but some of us are doing the math.

Don't be open to opinions, be open to the math and logic behind how the system works. Being open to opinions in machinery is what will mess you up.

nycgps

iTrader: (4)

everything starts from opinions

Yeah I get what you mean.

scathcart

I dare you to call any one of the above and they'll all tell you the same thing I have.
I've shown you the math.
I've told you from first-hand experience.
Others have told you the exact same thing I have, after having their rotating assembly balanced.
Below is a detailed list, prepared by CLR, of the exact balancing process:
https://www.rx7club.com/showpost.php...24&postcount=4
Notice they don't say anything about balancing the eccentric shaft?

After all this, if you choose to take your self-formed, unfounded, and unreasonable opinion to be held as your personal belief, then so be it, but please don't spread your misinformation to others.

20Bforme

i just read through this entire thread...

and all i have to say is:

nycgps

iTrader: (4)

actually I did asked them. so yea and your point ??

ok, Im done you can have all the fun.