pistonsuk

I just finished these today too. As some other people have done, I have cut on the trailing side to increase intake duration. This should move the torque curve to the right (better filling at higher rpm). Hopefully, paired with the twin scroll setup (which should move the torque curve to the left, or hold it even, with a larger turbo) I will end up with a larger/flatter torque curve.

I just used a ruler, Sharpie and a 1/4 die grinder with a carbide burr. It took a couple of hours. I also plan to ceramic coat the faces with this CBX powerkote:

http://techlinecoatings.com/BulkEngine.htm


Here are some pics:









I also weighed these before and after:

Rotor 1=> Letter="C" => Before=>4342.11g After=>4312.68g Net=>29.43g

Rotor 2=> Letter="B" => Before=>4377.57g After=>4347.83g Net=>29.74g

As seen above this should not pose any vibration issues as far as counterweights are concerned. Mazda allows up to 2 letters difference in a factory build. The weight difference between this "C" and "B" rotor is 35.46g. This is more than I removed (~30g)!

This too has to wait until this spring to get tested. I should have the engine together by June.

Justin

APEXL8T

So you plan to send them off to get re balanced?

dubulup

Though you have retained a good weight ratio...I would think taking weight out of a rotating assembly (anywhere), throws the rotational weight distribution out some what? Have you talked with engine builders who are familiar with this type of port phasing?

why not just bridge port the irons if this was all you wanted? "increase intake duration"

It appears these rotors, have a little more attention than just grinding some metal out...


Good luck with the project, should be interesting!!

pistonsuk

You mean each rotor individualy? Right? To make sure each apex has the same inertial force when rotated about the center.

No. I wasnt planning on it. I have my doubts that it is any worse than something Mazda would let go out the door.

Does anyone have the spec to which Mazda balances the individual rotors?

For kicks: Lets assume that one pair of cuts (on one face) had 10% more material removed than either of the other faces.

The total weight removed was 30g, divide by 3=10grams each face, multiply by 10%. That means that my rotor apexes should be within 1g of each other at worst.

Is this bad? I dont know.

Justin

pistonsuk

True. But I think the amount that it is out is well within the Mazda limits. My reasoning explained here:

Nope. Someone else on the forum did this back in Dec of 05. Do a search, his is working good so far.

True about duration, but fundementally different. Bridgeport is an early open port. Early open increases intake/exh overlap, which not what I wanted with high pressure, hot exhaust (turbo) and detonation sensitive engine (boosted). What I have done is a late close. The mixture is already being compressed before the port closes, so I will get bad filling at low rpm. At high rpm the intertial effects should take advantage of the increased duration and contine filling the chamber. This is what Mazda was doing with the 6-port design.

Yep. Those look CNC'd. I would have liked to do that, but then again mine cost rougly nothing. If my hypothesis end up wrong about balancing, then maybe the $xxx for having them cut will be worth it in the future.


Thanks! Hope interesting=powerful!

Justin

t-von

iTrader: (8)

Congrats on doing this yourself. I hope the mod works well for you.

maxcooper

Racing Beat can balance the rotating assembly (e-shaft, rotors, counterweights) for a modest amount of money. Your reasoning that you are still within the Mazda factory specs seems valid (assuming the quoted numbers are correct), but it is nice to ensure tight tolerances on the balance, particularly if you plan to raise the redline.

I had my current engine balanced, and it is very smooth. I haven't done a direct comparison to an engine that wasn't balanced in this way, but it is a neat test to hold the revs near redline in neutral for a moment and witness how smooth it is (and with little exhast noise, as you would expect in any unloaded rotary). The balanced engine seems smoother than my last engine, but I don't trust my memory enough to make a strong claim to that effect.

-Max

SureShot

After making the 1st cuts, I made this template to keep them all exactly the same.

Mazda does rotational balance the rotors, and I didn't want to interfere with that.

pistonsuk

^ Good Idea.

Does anyone know what Mazda's spec is on this?

Justin

sholitz

iTrader: (1)

Suuuuuuper old i know...but I'm curious as to how this project turnned out? did your diy work?

SureShot

I'm past 3000 miles.

So far so good.

Howard Coleman

iTrader: (6)

congratulations.

it is always the best moment to see someone doing something differently. with apologies to Carlos Lopez of course. i do appreciate your shirtsleeve-engineering efforts to creatively improve the breed.

continued good luck and keep us updated.

howard coleman

p.s. 'looks like it might just work

pistonsuk

It's killing me to find out. The thing is I dont have my car with me here at school. I graduate this May, then its home to my car and a paycheck

I will definitely update this thread when I get some results.

My hand calcs show that the balance shouldn't be any worse than the factory setups. SureShot has a very similar setup, his seems to be doing fine too.


Justin

IRPerformance

iTrader: (41)

You drop that rotor? The corner seal slot looks like ***.

GregW

Our local engine shop charges $150 to balance the rotating assembly.

Each rotor individually and make them the same weight.

then balance the rotating assy.

Then polish the e-shaft(dont know why they call this polishing when they use 400 grit to do it)

Im sure most places charge < @200

At that price youd be dumb not to get it balanced.

pistonsuk

Balanced to what? There is no such thing as perfectly balanced, there must have been some spec used. I wonder what this spec is?


Also impossible. To what spec were they balanced?


My price is $0 and it might already be "balanced". With the spec defined as "any better and there would be no noticable difference or benefit".

I'm not trying to sling hate. I just want to illustrate that nothing is perfect, but my in-expensive setup might be just as good as "professionally balanced" setup.

If someone can give me a spec used by a professional balancer then I will be able to determine if my setup is still within "spec."

Pondering:
Lets assume that it was possible to "perfectly" balance both the rotors individually and the entire assembly. What happens when oil is injected in to the rotors to cool them? Can anyone ensure an exact oil mass-distribution?

Thanks,
Justin

Godzilla-T78

I have this done to my rotors except we had ours done by a computer controled lathe and such.. mine are quite simular to the ones posted earlier in the post that were done by carlos. All I can say as it does the same job as a bridge port without the shitty idle. If you have your assembly ballanced you will not regret the money spent, if you plan to run your engine into the higher rpms its a must! Anyways good luck on getting it all backtogether and running, good job takes alot of ***** to do that yourself with your own hands lol..

pp13bnos

iTrader: (1)

I'm with the people who said to get it balanced. I'd love to see some pictures of the bearings after 10k miles.

I realy hope this works out in the end for you. CJ

dubulup

like I've said since the beginning...balance these rotors w/ your counterweights. You won't regret it.

brent clement

I believe that balancing the assembly is a good idea, however if you keep the rpms under 8500 can't see it being a problem. As for the rotors, I don't see how taking equal amounts of material off all three sides would through it out of balance. Maybe I'm wrong, but I think it'll be great. You've got my vote.

Brent

pistonsuk

Has anyone been reading my posts? I am hinting at the fact that there is a large possibility that I will regret it! I will regret wasting the money, if it is unnecessary.

Should I have my window crank handle balanced? No, because due to its function it can be very far out of balance and function properly.

As I mentioned before. Nothing is "balanced." Things can be balanced to a spec. Until this spec is known, there is nothing to say your $100-300 worth of balancing means squat.

If someone has this spec then please post it.

Until then I will compare my setup to what I have observed Mazda's spec to be, which apparently allows for rotor weights to range upto ~70grams without changing the counterweights*, and the rotors weight deviation to be around 35grams.**

* Does mazda dynamicly balance each rotating assembly? What is their spec for this?

**This info was found by weighing (3) rotors (B,C and D), then comparing the weights. If someone has more than three it would be nice to get a better distribution of the weights.

So if I had two identical weight rotors and then I removed 29.XX grams (this is how much i had to remove) on one rotor then I could install it with with one uncut rotor and still be within Mazda's spec!

I removed <0.3grams more from one rotor than the other. Is this is out of spec?

Justin

GregW

Yes there is no such thing as perfectly balanced but you can get it very ******* close. Hows that for a spec: "VERY ******* CLOSE". You can basically get it as close as you can measure.


Its not rocket science, ANY engine shop can do it. Its also a dirt cheap mod.

As for the oil. Centrepedal force spins the oil to an even level inside the rotor.
So yeah, thats not part of the equation.

But yeah, your right, it will prolly be just fine without balancing. $150 is a cheap insurance policy though.

Why do you say impossible? Ive seen it done and will have it done in the very near future.

With a balanced and speced engine I have no problems with bouncing of 10k now and then. If I miss a shift I have peace of mind.

Why the **** did you post pics to a FORUM if your going to be such a bitch about people making suggestions to you. Especially if they have already done what your doing?

pp13bnos

iTrader: (1)

What i think is funny, is that you think it *might* be close. Just like in horse shoes, and handgranades. CJ

jic

iTrader: (1)

gl with the project

c00lduke

How does beveling the rotors have the same effects as bridge porting without the crappy idle?