I have a set of s5 T2 rotors. there is a machined finnish on them would I affect the compression ratio, or ballance if I went over them with some 400 grit sandpaper and then polish them? I want to prevent carbon buildup. Is it a worthwhile mod? Thanks.



-Dan

i polished up a set of s4 turbo rotors. i didnt really do much other than shine up the machined faces, so i dont think it changes the balance.



i dont have any way to tell if it did anything, but the engine did run really well

I use an angle grinder with a 3M abrasive impregnated bristle pad. Takes off the carbon without damaging the metal. Just don't go crazy with it. Mac carb cleaner also works great if you let the rotor soak in it overnight.

Yeah I started Polising my S5 rotors Racingbeat.com says that whene you take the metal down it changes the balance of the rotor.

Factory balance is so far out I don't see how you could make it any worse anyhow...

i say go for it. i don't think i'll ever assemble another motor without polishing the rotors again.

Huh?? What are you talking about?



It's not "so far out of balance" in that they rev to 8k or 9krpm stock out of the box...



B

:Hides: 3k... 1/3 of 9000 rpms.. :continues hiding:







BC

haha, good point.

not to mention it goes round and round instead of up/down.

the stock engines are grossly out of balance compared to any piston engine in production. Rotaries are just THAT much smoother.

[attachment=42452:Port_rotor1.jpg]Here is a pic of a rotor I polished up, with a ported iron.

-Dan

very nice. https://www.nopistons.com/forums/pub...IR#>/smile.gif how much time did that represent? then again, you probably have much better (and more efficient) tools/equipment available to you than i do.



there should be pics of the last 12A i built floatng around here somewhere. i plan to start on a 13B soon. between being lazy and trying to sort my life out, i haven't made time to begin working yet.

The heavy parts in a piston engine go round and round, too. The light end of the rod and the pistons go up and down, but their travel is described by a sinusoidal wave and not anything jerky. If you've ever rode on a Scrambler type carnival ride, you've felt what it's like to be a piston except you get the accelerations in both directions.



Plus, the heavy rotating parts of a piston engine are much closer to the axis of rotation than in a rotary, so a gram out is much less critical.

You'll be surprised how many engine builders don't know that. Imagine a piston motor with the factory imbalance of a rotary. It would shake it self to death. Going round and round do have it advantages. The most noticable results from balancing are with a totally stock motor. It's so much smoother and very willing to pile up the revs. https://www.nopistons.com/forums/pub...IR#>/smile.gif

On heavily modified ones your bearings will thank you.

Care to elabourate a bit on this? I was under the impression the rotating assy was very well balanced from the factory.



B

First couple engines I did I couldn't believe the difference, even the owners noticed.

lol, we've been amazed at our customers ability to hear the teeniest little noises from the steering wheel, it was so quiet, that with the engine running the average human cant hear it, yet totally ignore the flatspotted tires and bad wheel bearings.

Hmmm. After thinking about this, I think I'll start doing this on all of the motors I build from now on. I found a local place that'll do it decently cheap so it won't be much more in terms of overall cost to the customer. Thanks for the suggestion, Crispeed. I guess I was wrong in what I had assumed based on what some others had told me.



B

Pardon for bringing up a dead thread (and this is my first post here btw) but...

I was wondering what you guys do when balancing your motors. I will be putting together a new motor and want to do this, or send them out to be balanced.



I was wondering mostly weather it is just as simple as balancing the two rotors equally together, or another system that actually would balance the tips of the rotors. Just curious.



Oh, and I almost forgot https://www.nopistons.com/forums/pub...#>/biggrin.gif wouldn't polishing the faces of the rotors "TECHNICALLY" aid in keeping some of the heat in the combustion chamber and away from the oil. This I would assume would help with detonation as well, but that's just an assumption.



dpf22

It looks real cool, too!



Attachment 18730

If lower oil temperatures is what you're after you're going to see far better results with coatings. We also offer the balancing service.

https://www.nopistons.com/forums/gal...0_42_40243.jpg

You'd have to polish them alot. I wouldn't say they were polished but I brought a set of s4 na rotors to about a 600grit finish and when I pulled the eng apart it hadn't made any difference in carbon build up.

Or, you could just set the car up right and the money spent on this coating junk won't be wasted.



B

Easy there B. The "right" set up may be different depending on who you talk to. Also; last I looked, keeping as much heat in the combustion chamber and in the exhaust was a good thing.... At least on the side of turbo spool characteristics.

As far as I understand, the rotor faces communicate a lot of heat into the oil (as they are full of it) But again I am assuming. I merely like to ask these questions so there is more info out there. I am a novice engine builder(with rotaries anyway), but I love learning everything I can.



Peace, love, and chicken grease https://www.nopistons.com/forums/pub...>/bigthumb.gif



dpf22

I agree on the turbine housing and turbo/exhaust component portion, but I'm nowhere near sold on the idea of coating the rotor housings, iron housings, rotors, etc. I think it's a bad idea. I've seen engines fail showing problems with internal coatings.



B