I have been meaning to post this info before but was waiting confirmation from a local Mazda Tech on application reasons.

All Series 2 Engines made from November 10, 2008 (from my EPC calculations) has this coating applied to Rotors.....see factory pic.

Not yet confirmed why, but, Tech believes the coating is there to defend engine from Excessive Carbon Attachment or ECA (his words).

It is considered a Teflon non stick type of coating.



Investigating further, I confirmed this 'Rotor treatment' on the spare brand new factory Renny II Short Engine (Made May 5th, 2010)
I own by shining a flash light into the spark plug holes and turning over e-shaft.
I can clearly see the charcoal grey coating over the Rotor surface only broken by each silver Apex Seals.

Will be interesting to see how this new coating procedure stands up over time/use, and at some stage when these engines are rebuilt.

Anyway, I thought it worth a "tech discussion" here.

 

Nice find ASH!

Thanks, and sub'd for interest

 

Will be very interesting to see how this holds up with time-in-service. Hope it works!

 

mmm, I bought a brand new Rear Rotor Recently, it could be old stock but I don't see this coating on it. it just looks like any other regular Rotor.

mmmmmm, if they're doing this to all their rotors now(or should I say back in 2010?), maybe I should buy another Rotor and see if I have any luck of seeing this new coating.

no word about it on the service highlights tho ?

 

You bought a Series II rotor?
Why?

BC.

 

It's a nice find but i don't think it is PTFE\Teflon as it has a melting point of 320ish °C

 

That’s pretty cool ASH, thank you.

It may not be Teflon but a metal similar to what VW/Audi started or tried to start using in the DI gas engines to mitigate intake valve deposits. I can’t remember exactly what it is or where I read it but it could have been on BITOG or DMW. I think it could be a Tungsten alloy, but that’s a huge guess.

Subarus do or at least used to use Teflon in their 2.5L NA engines about 15 years ago to reduce friction and I don’t recall there being heat issues there but that could have been in areas not directly exposed to the combustion environment.

 

This came in 8 months after the first S2 were released.

'C' Rotors used in S2 (Renny 2) are identical to 80% of all Series RX-8's, 'C' came in 2005 production.

I am pretty sure this is a 'in production only application', and not on OE replacement spare parts.
Not the first time Mazda has done something like this and wont be the last.
I cant point to many parts which are not available as a OE replacement or only in production.

Plus IMO I don't think they want to put out another 'set' of rotors in the market, meaning, would you want to buy a "pair" new?, and that extra cost.?

As I see it Mazda has taken on this extra cost to extend the life of original engines.

 

Well the series II 8's seem to be holding up way better than the series 1's so obviously the figured a few things out to help extend engine life.

 

Yeah I guess, personally I am not so convinced quite yet..

*4th year of use, so 'issues' should start happening this summer in NA.
*S2 vehicle numbers out there are way lower than S1.

They still run pig rich!

 

It's the same rotor for all series, just the engine housing is a bit different (extra holes here and there for newer injection method)

I got it for cheap, I was about to buy all of them but I ran out of funds ... so I just got 1 and the rest was gone

:-)

 

well, they fixed so many issues found on S1 into the S2. so I think it should last much longer ...

yeah ... I wonder why too ...

 

and I just checked ... they actually have Brand new 2009+ engine in stock ~

but ... it cost almost double if not triple ... of a Reman ... *sweat*

 

Jeesh, for that amount you can build a s1 engine that will overperform any s2 engine reliability wise! Lol.

 

To save the CAT. Otherwise EGT would be pushing 2000 def F easily, way beyond CAT spec limits.

 

Where did you find the engines? I'm being told Mazda won’t sell a new engine to anyone, which I found dubious.

 

ok, this is not cool, I bought some old rotor, I want that rotor, NOT COOL

anybody wanna buy my Rear Rotor ... ? I sell it for 500 ! Cheaper than getting one from Mazda !

 

If it's a graphite-grey color with a dull sheen, it's probably molybdenum di-sulfide. Good stuff, extremely hard and abrasion-resistant, holds an oil film very well, doesn't burn off, and very slippery even when un-lubricated. It's used as a vapor-deposited solid lubricant on gears sometimes.

Alternately, if the rotors are aluminum, they might just be anodized. BMW has been anodizing their engine internals for a long time to reduce wear and improve oil-film retention on lightweight aluminum parts.

 

I vote quasicrystalline coating.

 

Mazda knows Aluminum works 100 times better, but it cost WAY too much. consider the engine now cost 7-8K brand new, with Aluminum rotors it will probably cost 10K+

well, will the coating work? we will have to see, but seems like Mazda will NEVER give Rotary Engine up, that's for sure

 

Hmm. It might also be a phosphate-conversion coating, the same coating used to prevent guns from rusting.

 

I bet its not for reducing carbon deposits--its to keep the combustion heat in the combustion chamber.

 

If that's what they're trying to do, they'd need to coat the inside of the housings instead of the rotors. Heat doesn't leak out through the center of the engine, it leaks out through the surface of the engine.

 

The rotors are internally oil cooled and pull tons of heat from the engine...

 

I doubt much heat leaks out through the rotor bearings' lubrication jackets. The rotor faces are constantly being cooled by fresh air from the intake, just like pistons in a piston engine do. The first rotary engines actually used oil-resistant rubber for the round seals around the bearings, because they stayed cool enough that the rubber wouldn't melt.

As far as I know, the single largest reason why rotaries leak so much heat is because one section of the rotary chamber is constantly exposed to combustion, and the heat absorbed by that section of housing never gets re-absorbed by fresh cool air like what happens to the cylinder head in a piston engine. So, to keep that part of the rotary housing from overheating and warping, there has to be massive watercooling in that area, and THAT is where most of the heat escapes, causing the efficiency drop rotary engines are known for.