Hey all

im going to be building a 13b for fun in the coming weeks and i was wondering if there was any benefit to polishing the faces of the rotor, much like cylinder heads are polished.

also has anyone augmented the compression of the rotors to higher CR by TIG welding the divits in the rotor face to have a smaller volume?

 

I would assume, since there's no direct contact, or actual 'air-flow' directed 'over' the rotors, there would be no gain whatsoever by literally "polishing" the rotors.

I would however advocate for a solid cleaning, to get rid of all the carbon build-up... My thinking on this is; once you start cleaning, you've officially 'loosened' everything... So if you don't get ALL of it off, there's "that much more" chance that a random piece will come off and perhaps damage something.

Interesting idea on the welding, but... Sounds a bit sketchy without having serious know-how and the proper balancing tools/R&D etc...

But I guess that's why you asked, lol.

 

low compression rotors are pretty readily available for a low price

 

I believe his intent is to get HIGHER compression rotors.

I.E. "higher CR" in capn's original post.

 

I have some rebuild DVD's here and they mentionned that new rotors are coated with a (I think) cadmium coat to prevent rust etc. I don't think it would provide any added value to your engine. Just make sure you have them cleaned thoroughly (chemically cleaned)

 

In high horsepower engines it might be worth it.
Im thinking heat-dissipation, its all about keeping the combustion heat in the gasses and get it out the exhaust.

I could be wrong, im no pro but this made sense to me

 

I have gathered from other people's experiences that polishing can be very beneficial. There are some effects to this which may or may not be what you want. Polishing the rotors gets rid of the rough casting texture of the rotor tubs. This can be a negative in some cases, because it may decrease fuel atomization. The positive effects of getting rid of the rough texture are that carbon has a harder time sticking to the rotors, and also that the smooth surface will not retain heat the same way. The difference in heat retention could get rid of the chance of having hot-spots that could lead to pre-ignition (detonation). Another effect of polishing your rotors is that you are lowering the compression ratio. Again, this can be good or bad depending on what your goals are with your car. Just remember to send your rotors out to be balanced after grinding all of that material out.

 

well my goal for this engine is purely experimental, and then sell it for some money.

but im going to see what exactly i need to do to balance the rotor and weld the tubs a little so its a high comp engine. (im starting with S4 TII rotors)

but im also going to experiment with the "tub" design see if i can find anything thats beneficial to a high rpm/power NA

 

Please explain ...

 

yeah like by .00001 psi

 

coat the surface of the rotors with that ceramic coating. I used so Sealed Power pistons with that coating and they lasted longer and didnt show any signs of piston burn. YOu can also coat the intake and exhaust ports to keep heat out and in.

 

i messed up on the last post i made, i meant higher compression n/a rotors

S4 n/a rotors are 9.4:1 compression
s5 n/a rotors are 9.7:1 compression


they are cheap enough to aquire, rather than welding things into the rotor to essencially make the balance out of wack, and wearing out the bearings.

 

well why not make them 10:1? i could also make a unique tub design, and possibly make some better flow or flame prognation.

 

then get rx8 rotors, they are 10:1 ratio.

see the thing is... rotors are not like pistons where adding some "divits" to reduce the volume or tubbing them out would work, unless you have some high priced machine to balance the rotors. for pistons, you can be slightly off, and the pistons will still go up and down the cylinder, throw off the weight on one rotor face and your bearings will be shot in a matter of miles

 

Sorry, but no... Physically taking a grinder to the tubbed portion of the rotor is what I am talking about. This would remove the rough casting texture that is there, and would take off enough material (increasing volume) to probably drop your compression by 1-2tenths of a bar, which is going to be around 1-3 psi. Obviously if you have lower compression rotors, you are starting out with a bigger tub, which means you have to take off even more material, which in turn lowers the CR even more. It doesnt seem to be too terribly significant, but if you have a target CR that you are shooting for and want to polish your rotors, you would probably be better served to start with the next higher CR rotor

 

The simple solution to this is sending your rotating assembly (rotors and counterweights) away to be balanced. It is not a big deal. Usually around $200, plus your shipping charges, which are probably semi expensive due to the weight. I would guestimate about $250-275 for balancing and shipping after they are sitting back on your doorstep.

 

im not going to be grininding it im going to be polishing it, and also i said i would weld up the tubs a little and make them higher comp. but this is for experimental fun purposes.