Good Info On Rotor Balancing
 

Just found some information in the Gen Technical threads that might be news to some. It was posted by rgordon1979.
"I am in the process of rebuilding a '88 TII engine. In the process of finding a new rear rotor and housing I came across something I have never seen on here before.
As you know, Mazda balanced each rotor at the factory. Due to slight variations in the balancing process, each rotors weight varies slightly. Mazda designates this variation by stamping a letter, (A-E), on the gear side of the rotor. According to Mazda the rotor weight should not vary more than 2 letters in an engine. Ideally, you should have matching rotors. I did verify this with Henry at Mazdatrix. If this is common knowledge, sorry to take up the bandwidth, just wanted to let everyone know.

Rob"

good to know. I need to get a new rotor whenever I decide to do my rebuild

Experienced rebuilders know this.
If it's not obvious, A = heaviest; E = lightest.


-Ted

yea, I see that Es cost ALOT more....

Where do you see this on MAzdatrix site - NOPE!

dont mislead people

Couldnt a machine shop balance the rotors for you? I'm not sure if you need any special equipment. But balancing the rotating assembly on a piston engine isnt really a big deal. I figure with the rotors, if you want to make them a bit lighter, you can just remove material, then rebalance them. Am I missing something here?

I don't beleive Rob says he found it on the website, he says a guy named Henry at Mazdatrix verified this.

They'd have to be awfully good since you not only have to worry about getting the two rotors to the same weight but also have to keep the individual rotor balanced in all three dimensions to insure it doesn't tear the engine apart at high RPMs. I'd sure be scared to allow any machinist to do this. Just specify the correct rotor weight by the alpha code.

so you are saying that mazda balances the rotors at the factory, but there is no other place on the face of the earth where this engineering knowledge applies? If they can balance the rotors at the factory then there is a way to balance the rotors. I'm pretty new to the whole wankel engine, but I refuse to believe that you can not balance a rotary. I will look into what sort of procedure is used to balance a rotory engine and get back to you. If there is anyone here who knows, even rumors, please post.

Any good machine shop should be able to do it. I've never had any luck with automotive machine shops except for resurfacing flywheels, so I always suggest going to a "real" machine shop.

Turns out that from the factory the rotors are balanced to within 15 grams of each other. Most rotary machine shops can balance them to within 1 or 2 grams, as well as balancing the entire rotating assembly. One shop that I found in Redmond, WA looked particularly good.

One thing to keep in mind when balancing the rotating assembly is you must figure in the amount the OIL weighs withen the rotor. If you static balance all the parts, then do a dynamic balance with the rotating assembly without compensating for the oil thats going to be in there while the engine is assembled and running, you'll find a rough non-balanced engine on your hands. Do a search, theres a little info on how to do this.

~Mike..............

you make a good point, i never even thought of that. i'm not sure how much of a difference in will make... but i guess at high rpms even a small amount of oil could lead to unwanted harmonics. thanks, ill check it out.