Some Cermet engine results
 

Hey all, with some of the current interest and cusiosity of wether or not these parts are working, I decided to post some results from the cermet engines. I just did a compression test on a 12a built with cermet b housings and lapped end plates, after 1200kms it has 120 psi compression at cranking on both the front and rear. Motor is needless to say running awesome. Very happy with the cermet housings as is the guy who owns the car.

I have some other motors with Cermet in them as well, and will post results once they are broken in as well. I had no issues with tolerances or anything. Housings looked great and are working great.

What apex seals are you using with them?

Good news to hear wpgrexx....I've done 2 motors so far using JHB housings. I've used the stock Mazda 2 piece seals to build both motors.

stock mazda 2 piece 2mm. I think this is like the 5th or so motor I have built with the cermet. I like the way the cermet breaks in, rather quick compared to new chrome.

What is Cermet?

See this site: http://www.jhbperformance.com/

Do you have any sort of dyno results? Are the motors more potent with the coating? do they run cooler? any other information?

Breaks in and wears out way too quick.Has anyone had a cermet engine apart to see the wear? All those little bits of cermet ripping everything apart.

OK, what's up with this. I have finally started to get my motor back together and now I see this. All of my housings have been done with cermet b. The motor had 100k on the side plates and so I decided to have them cermet coated instead of buying new ones. I opted for this instead of just lapping the housings and loosing the nitride suface and having them wear out even quicker. This seemed like a good option. It is supposed to last longer, wear less, and reduce friction. Has anybody else had there engine apart to see how this stuff is actually holding up. I am going to hold off putting my motor together now.

My rotor housing were also coated because they were scored from using some RA seals. The seals were in there less than 2000 miles. When the motor went together the housings were fine and had only 35k on them. when we pulled the motor back apart to fix a sticky side seal, the housings had scoring like that in other posts that are starting to come up. Needless to say I won't be putting the new set they sent me for warranty. To many people are having problems with them creating too much friction and pulling tiny bits of metal off the housngs. Now this problem with the cermet housings in the pic.

I found this thread after hearing of problems with this stuff from my builder who is concerned about building my engine with these housings. He called around and asked me to search for info on how this stuff is holding up. Go figure, the first post :confused:

Mike

I'm so interested on this topic.

So many questions yet no real time data on these :(

If I remember correctly, Tim had his housings reground somewhere else after he got his housings back form JHBperformance. So his coating might have been to thin to last and protect and do all the other stuff they claim.

Details are in this thread: https://www.rx7club.com/showthread.p...hlight=cerment

Is that a product from JHB or some other company?

I too, have had ALL my housings done with cermet a on the sides and cermet b on the rotor housings. I was planning on having it all back together this month and now I find this thread! Please give some background info about your picture.
From the research I've done, cermet coatings DO have heat resisting properties, are much wear resistant than the iron istself,and even have self lubricating properties should something begin to overheat or loose lubrication.

I'm sure everyone has seen a news flash or two of the safe return of the Discovery space shuttle & crew. Guess what NASA uses in the heat tiles...
A ceramic based formula! NASA has even done ther own research with rotary engines!!! I found a NASA article about how THEY had done their own testing with a cermet coating called ps200 in a rotary snowmobile engine! They even claimed to have developed an even better coating (ps300) which they believe would allow an engine to be run WITHOUT lubrication! It turns out they already have ps200 being used in production in Moller Internation's "Freedom Motors". (Which are a rotary engine design!): http://www.sti.nasa.gov/tto/spinoff2001/t2.html http://www.moller.com/

And I just found these other links.(NASA's still not finished with cermets yet!)

http://www.grc.nasa.gov/WWW/epbranch...CermetCoatings

This very good link for those who have no idea what or where cermet comes from, where it is used, and where it WILL be used in the future:

http://www.newi.ac.uk/buckleyc/ceramics.htm

Just do some searching on your own. There is a ton of info about cermets out there!

I have now laid out my position on cermet coatings, backed up with SOLID proof.
If there are problems with the cermet coatings being used and sold by JHB, Why are they still in business? Why would the Mazda 787b race car use cermet coated internals if the coatings wear out prematurely, leaving bits and pices to grind up the engine? (I'm sure I've read/heard elswere, that if a piece of cermet ever was to be chiped off, it would turn back to dust. But don't take my word for it.)

http://www.answers.com/topic/mazda-787

I would definitely like to see/read proof that the cermet coating is no good, because everything I've read/seen has been good news.


Trueblue707


Go ahead and flame away all you want...I want to be proven wrong, so I can get a refund from JHB. LOL

Tim really should have come into this thread with the full story. I think he really just doesn't want it to be his fault. He got out-of-spec housings back from JHB from a bad run, and instead of sending them back to JHB (which they offered because they'd already f-ed up his order) he sent them somewhere else to have it ground down. From my knowledge I'm pretty sure that the whole reason scalliwag was working on the armacor coating was that nothing else had the level of build up that it does, which would make me think that when tim had them re-ground he was grinding away at something thinner than he should have been. Noone to my knowledge that has gotten in-spec housings back from JHB has had the type of problems tim did having them reground. I believe the only way to have gotten his housings back to spec, would be to grind past the coating, and re-spray, which is the process for application in the first place.

I had my housings reground elsewhere to original spec,so there would have been 0.19mm of cermet on the steel liner. JHB say the finish is very important,and my housings were finished much smoother than they were from JHB.Considering that,there is still no way it should have worn off in 700 miles.I know the engine could have carried on running for 1000's of miles on the steel liner alone,but I stripped it after it started to lose power on the dyno.Most of the cermet had gone,in little bits,scoring absolutely everything.
What concerned me was before I built the engine the cermet did not appear very hard,not as hard as the original chrome.
I have now had the housings ground back to the steel liner,they are to spec,but there are a few lines of cermet still there where the original grinding by JHB was not accurate enough.Next coating?

I'm certainly no expert, but I always look suspiciously at new materials to be used in the engine. Recall that when Mazda was developing the engine they needed to find the right material to use for both the housings and the apex seals. Too hard of one caused damage the other. Too soft of one ment less life for itself. Logically using a new material would stand a high chance at throwing the balance out of wack.

The other property to consider with the housings is that they are designed to have microscopic pores to allow oil to stick to it. If the surface is too slick then the engine doesn't have proper lubrication.

As for use in F1 cars, R26B and Nascar, that doesn't give any indication if the material is appropriate for long term street use.

Side note: That link on the 787B had new info for me. I didn't realize that the R26B made 930hp @ 10.5k. Given their pace going into the '91 race, obviously they couldn't make it reliable enough to push beyond 9k.

a couple of issues with your claims here.

first-how can you take a product, change that product by grounding it down and expect it to still be what it was originally intended to be. You screwed it up. JHB offered to warranty that part for you if you sent it back, instead you went out on your own and modified it.

second-that plate you link a pic to isnt even coated with cermet, that is a stock plate, the housing was coated and than modified without JHB processes.

third-what spec are you referring to? ALso what means of measuring the smoothness are you using, an RA measurement? If so, the number you mentioned in the other thread is totally wrong. How did you measure them?

finally, I have probably more experience building with JHB's parts than anyone else, I have taken a motor apart after roughly 4500kms, after someone horribly messed with the timing and popped 5 out of 6 apex seals. The plates were perfect, all indications of a motor that was just fully broken in. There was no flaking or chipping like you claimed, and this was after a catastrophic failure. The plates went back in with cermet housings and is now making 120 in the rear and 110 in the front after another 1500 on the rebuild.

This all leads me to beleive that the parts work just fine, and the reason yours failed, and if it did chip off or whatever, it is because you modified the part. You totally changed al the properties that were originally intended to be there. Do you not think that the coating is applied to a certain thickness for a reason, and not to be ground down past that. Also, I know JHB uses very specific processes to achieve thier finished surface, unless you know exactly what they are, you have no bussiness messing with what was there. If you didnt like the part, you were offered to be compensated with a new one after they cleared up the tolerance issue. I beleive you screwed up the part and that is why you had the problems.

I will continue to use their parts in rebuilds not only because they are a superior product in every aspect to chrome, but they are also cheaper than new housings.

That is what is so cool about the cermet coating. It is very hard, but has less friction than crhome. Thus, it mantains and even betters the "balance" of the engine as you called it.
I understand your position. I was very scepticall/cautious when I found out about this stuff.

Someone mentioned Scaliwag's cool project of armorcoating housings. I realy hope he can get it to work. We need more people like him. If you have the time, I recomend you read Scaliwag's thread.
https://www.rx7club.com/showthread.p...2&page=1&pp=15
Mark from JHB even bumped in there with some of the test data and pics of JHB's cermet housings. (Pg. 40+)

I haven't heard of anyone else having a failure besides Tim. His case is obviously canceld out by the fact that he altered the coating by grinding and refinishing it.

I did have a small problem with JHB. They sent me S5 rotor housings instead of S4's. They readily gave me the option to have them exchanged for free, but after some consideration I decided to keep them. If it turns out that I have issues with the S4 internals and computer not working with the S5 housings properly(which I am 98.5% positive they will work fine together), then that will be my fault because I decided to keep them.

The only alterations that I will be performing on my housings are oil gallery mods, polishing out ports, and making sure the edges of ALL the ports have a nice smooth radius into the working chamber. I don't plan on ever needing to rebuild this engine ever again, as this will be a bi-weekly driver and only autoxed now and then. If I do take it apart, it will be for porting and ceramic epex seals.

Soon, there will be cermet engined 7's showing up in various places, expelling the doubt about the cermets's abilities.
It's all just a mater of time. Ceramic seals have proven their selves time and time again. Hopefully soon, cermet coatings will be given the recognition they deserve as well.

wpgrexx,
Sorry for getting off topic. This thread was about your compression tests. I like those numbers. I'd like to see that kind of compression in my 13b cermet engine. Any tips/tricks I should know before I stack my motor?

Thanks, Trueblue707

just make sure you have all internal surfaces nice and flat and use new seals. Basically I wanted to show that these motors are making great compression and their is nothing wrong with the cermet parts.

No,JHB screwed up my new rotor housings.What are you saying,I made the coating softer by having it reground?
The plate wasn,t coated,but totally ruined,it was absolutely perfect 700 miles earlier.
If JHB had said the coating was thicker for a reason,then fair enough,but they promised my housings coated and finished to original spec.,then screwed them up.
They never offered me a new part as compensation as you say,and they refused a refund.I did not trust them with my housings again,so that is why they didn't go back.
I had them ground so my rotors would have the necessary clearance.Did you check any that you built?
Are you associated with JHB?

You can go to Mazda in Hiroshima and see the ceramic coated parts on display.....
The main difference I think is the mazda parts were not previously chromed or nitrided then coated, the mazda parts were virgin metal with no oil embedded in the pores or grain of the metal. I dont know what prep JHB does to the parts prior to coating, but I would think it would have to be contaminate free before coating, I dont think the coating would stick to the chrome or traces of chroming, or metal that is contaminated with oil residues..
The mazda parts were most likely covered with a much thicker layer and then cut to spec..Max

Great! I cant wait to hear how the other engines do. With my puttering around I should have my engine up and running in a couple (or more) months with compression numbers. I realy wish I could find the right 7 for it. It came from an SE automatic with power steering. I do have an '86 SE from wich I was going to get the manual steering rack and parts to make the '88 into a standard. Its going to be alot of extra work, but I'll do it if I have to. Why couldn't Mazda just put both standard and automatic transmission mounts on every model?...lol



Mark told me the side housings are ground flat which I asume would remove the nitrating, then coated and lapped down to spec. I can't remember what the target thickness for the coating is suposed to be, but I do remember he said it was six or seven times the required amount to last the normal lifespan of the engine. The process for the rotor housings is a little different. I believe all of the chrome gets removed to expose the inner ribbed steel sleeve before coating, and then ground/finished back to speck. I'm not quite sure how its done, maybe they disolve the crhome out of the ribbed sleeve with a chemical proces? Whatever they do, he said as long as the wear/damage dosen't go through the crhome, the housings are still usable.

The only afiliation I have with JHB is as a customer.

I wish Mark could find the time to start a thread on the cermet specs and testing data. Then everyone would get all the facts from the source, and not from hearsay. From what he's told me, they are keeping real busy filling orders. He said many orders are from dealers and are whole pallets of housings! I believe him because it took six months to get my housings back. I just had to have MY housings... :p:

Once again, sorry for taking this of topic. At least the word about cermets is getting out. Litle by litle...

My housings were new,so would have been contaminate free.If the coating needs to be thicker,and I made mine too thin by having it reground,then JHB are not doing any housings to spec. They told me they remove all the chrome,0.19mm when new,then apply the coating,then grind it back to spec.
Maybe the cermet was affected by fuel,I say this because the coating had worn off more from between the inlet and the plug area.Is this a possibility?

it is my understanding that you were told do whatever you want since you said you could do a better finish and they were you parts. After they were screwed up I beleive he offered you to send them back if you paid theoutstanding balance, you never replied back to him after that. He offered to rectify the situation above and beyond what is normally covered. Basically fix the part that you screwed up. I know he said he was having tolereance issues back then, and told you the same thing, which is why he offered to take them back for a new set of housings for you.

Am I associated with JHB, NO. I have become friends with Marc through buying his parts because I build engines and need a good supply of housings. Cermet is the best option.

More crap that just isn't true.Fact is the cermet came off,should never have happened.My housings left JHB useless for what I wanted them for,should never have happened.

Can you answer why others with them haven't been reporting a problem such as yours? The only difference between theirs and yours was how you handled the situation.. how can you still justify your actions instead of questioning them..

why not post the last email you received from Mark? I am not trying to be an asshole here at all. I just completely disagree with your opinion on cermet.

Not so much my opinion,but an account of what happened.I'm not so interested in what happened between me and JHB,but more interested in why the coating failed.I know I had the housings reground,that job was first class,I know the coating was then much thinner,but the same thickness as the original chrome,so why did 0.19mm of coating wear away?It is wrong to say I screwed them up by finishing the job,just is not the case.
Possibly affected by fuel or oil? Not as hard as the chrome?What is the make up of cermet A?

maybe I missed the parts list but what parts exactly did you have coated?

Assuming you measured correctly, I can see why you'd be upset but now we're all just left wondering what might have happened if you let JHB fix the problem, would it still have failed? What facts do you have that the reground housings came out first class besides that they were now factory spec and smoother to the fingers.. when it comes to a specialty service such as cermet which I haven't seen done mainstream, I would leave it to the ones with experience

I do agree and I wonder what would have happened if JHB had corrected it.No hard facts on the reground finish,apart from it was smoother,and to factory spec,just left wondering why it failed.How can regrinding it affect it's hardness.The apex seals were almost perfect,so I don,t think it was because they had a friction problem with the coating.
JHB would have removed the coating,reapplied it,then ground it back,all I did was ground it back,can't see the difference whichever way it was done.It did save me having to send the housings back to Canada,they had them 2 months the first time,and if I had sent them,I really did not think I would see them again.

JHB has been lacking with the info but I do recall in your other thread them mentioning a certain finish that they leave on the coating which was not the same as your smooth reground housings.. the true effects of the finish may or may not have been the cause.

I don't see one account of failure enough to convince me not to try these coatings, considering all the upsides they may have.

I have a set of new housings in my engine now, and I do see myself using the Cermet coating on then, should I need to rebuild.

I dont think it really matters what thickness it was reground, Timrx is asking why the coating is worn off, the regrinding and out of spec aside, who cares what he had reground to, the point is it started to come off...
Timrx says his housing were new, so they were not oil contaminated, but my point was that the housings mazda did, were neither nitrided nor chromed originally which could affect the ability of the ceramic to adhere on post nitrided and chromed parts.
The other aspect is that since ceramic is an insulator,with steel seals, it will remove one source or heat dissipation through the seal face to the housings, probably not an issue with ceramic seals, but definatly one with steel apex seals..Max

The whole PS serries of coatings are pretty interesting, they tend to take along time to run in though ie the seals wear very quickly for a long time compared to some other plasma sprayed coatings (even silicon nitride).

You used the PS coatings as an example that ceremet coatings are good so to speak and most are but you cant really use that to say all ceremet coatings are good. Due to the way they are applied and the different materials available there are thousands of materials that could be classified as ceremets all having different mechanical properties.

As for the friction of the coating this is usually more dependent on the oil that is used (assuming a constant surface finish).

And finally a line that comes up often in my work: Wear is a system parameter not a material property

I agree with what you say. PS200 is probably not what JHB uses, but mark has said it is very simillar. My point is, ceramics are being used everywhere in high stress/high performance situations and doing better than what was being used before...
http://www.carbideprocessors.com/saws/intro.htm

I'm realy glad to see so many people willing to discuss this issue, rather than reject it alltogether. Ceramics are working in so many different aplications, many of them involving much more stress/temperature than the rotary engine.


What can I say for tim? From what I can deduce it appears that his housings were not prepared properly to begin with. I think max has a good point about adhesion being affected by contaminants and nitrating. I believe JHB grinds the housings to flaten them if they are worn AND to remove the nitride coating to insure proper adhesion. If they were improperly ground or not ground enough, then there could still be unevenes or nitride left. The coating is too thin to "fill in" unenvenes and it wouldn't realy matter if you could/couldn't get it flat if there was some nitrating left on the housing to begin with. If the nitrating realy does affect adhesion then I would expect something like what happened to tim's housings.

It appears JHB has been able to solve the problem(whatever it was), as there are no other reports of this happening.

I have to say that if I was to purchase brand new housings I would not have them cermet coated. The whole idea is to take what is used and make it better than new at a cost less than buying new. Just my 2 cents.

It was only the rotor housings I had coated,not the side housings.The pic earlier was of a side housing scored by the cermet coming off the rotor housings,it has taken on the colour of the cermet.
Has anyone any idea of the make up of cermet 'A'?,or the PS200 coating?

PS304 which is probably very similar to PS200. The PS304 coating is applied using a powder with the following composition 60%wt NiCr, 20%wt Cr2O3, 10%wt BaF2/CaF2 and 10%wt Ag.

On the issue of bonding, if the JHB coating is plasma sprayed or uses a similar process the surfaces would most likely be machined/ground and then grit blasted to remove surface contaminants and give a surface that the coating can mechanically key to, becasue sprayed coatings are relativly thick and soft the nitriding on the side plates would have minimal effect on anything. I would be concened with the thickness of the coatings on the housings (if they are infact only as thin as the original chrome).

Trueblue, thats what i hoped you meant. For examples of ceremets being well and truely accepted in other areas Nikasil would be clasified as a ceremet, most (or maybe just alot) cutting tool inserts are ceremets as well

Oops. I should have read that thread mentioned earlier. I see now the coating looks as though the coating hasn't come of in the kind of pieces I was thinking of.
Those strange colors in the water jacket don't appear to be mineral deposits.

https://www.rx7club.com/attachment.p...d=127027&stc=1

It looks like it suffered from some extreme heat, especially when compared to what it looked like before.

https://www.rx7club.com/attachment.p...d=127028&stc=1

That housing looks beautiful, but something made it fail. The cermet housings I received from JHB are no where near as shinny as your housing looked. I'm sure they made them that way for a reason.

Here is my theory of what happened to your housings.

When you polish something in certain cases you could in fact be making that part more prone to heat buildup from friction. Think of it this way. A regular tire is designed with a tread in order to keep it from loosing traction in wet or otherwise slippery condition. But what happens to the same tire on the race track?
It actually looses traction at high speeds and or hard cornering.
Now look at a race tire. It has no tread and is nice and smooth. It also has fairly poor traction on anything else other than dry pavement. Now, what happens when this tire is used where it was designed for? It provides far better traction at high speeds and or hard cornering. Now why can't the treaded tire provide more traction than the race tire? I'm sure everyone knows.
IT HAS LESS SURFACE AREA IN CONTACT WITH THE PAVEMENT THAN THE RACE TIRE!


Here is my theory of what happened to your housings.

The only way the apex seals can get lubrication is by having the oil injected or mixed into the fuel. Once the oil enters the chamber it doesn't have much time to get to where it needs to go(especially at high rpms). Much of it goes right out the tail pipe. The happy molecules of oil that do accomplish there mission get into seal groves and onto the rotor housing surface. In order for the oil to lubricate well, it needs a place to hold on to.
That is why the chrome Mazda uses is porous and why JHB has a specific finish for their cermet coatings. The pores in the chrome or cermet act as little capillaries holding the oil in place, thus reducing surface contact as the apex seal slides over.
If the surface were to be polished there wouldn't be enough porosity in the finish to capture and hold the oil and an increase of surface contact and friction would result.

That is probably what happened with your housings.

The oil getting onto the surface was not clinging as well and being swept away by the apex seal due to the greatly reduced amount or pores for the oil to get in and hold on to.
As the rpm's increased, so did the heat from the friction caused by the two very smooth and sparsely lubricated surfaces of apex seal and housing.
As the temperatures approached the heat limits of the cermet coating it began to self lubricate, but couldn't lubricate enough to lower the temperatures.
Again, because there weren't enough "holes" for the lubricant vapor particles to be trapped in.
The friction and temperatures at that point were probably more than enough to begin a galling action on the seals. The seals began to chip, sending pieces throughout the engine which then caused more damage to the seals and scratched up the housings.

Again, just my two cents.

Thanks for the input.The apex seals weren't chipped at all,they looked fine.Lubrication was 100:1 premix.
Engine ran fine for 700 miles,until it went on the rolling road.Coolant temp stayed at 86C.I put in 106 octane race fuel,first run I had 349rwhp,then went downhill after that.Something was happening to the coating.I found this on Aus Rotary about the R26B:-
''Chrome-carbide based cermet,applied by detonation gun spray.Providing stable cermet coating is important to secure engine reliability,and of utmost importance in preventing exfoliation of the coating during driving.Regarding exfoliation,various processes were investigated to solve variation factors.''
So is it possible that the race fuel reacted with something beneath the coating,exfoliation occurred,made more possible because the coating was thinner,turning it into carbide grinding paste?Everything inside the engine was coloured.
I thought I had exactly the same coating as the R26B engine,but cermet A certainly doesn't look like a chrome based material,it has a stainless steel appearance.What is it?

I believe how the coating material is ground to spec may affect its adhesion as well.

I seem to recall Scallywag mentioning if during the grinding process there is too much heat built up it will affect the coatings adhesion to the liner.

Keep up the good info:) I called JHB and talked with them for about half and hour.

I'm extremely interested in this since I have 6 housings that could use this treatment. (and the fact that mazda no longer makes housings). If this works I guess I really only need one set since they can refinish them at a discount if you happen to scour the cermet during an apex seal failure.

The only answer I got concerning rotor clearance was that these housings are returned back within mazda specs.

I only know of one person running these coatings and his motor is still fine. Another person will be running it as well.

I only heard of two people with concerns regarding this process.

Apparently jhb has a race car that has been using cermet A process for 6 years without issues.

This all sounds promising. I've been told that they are raising the prices in october.


Now to figure out what type of apex seals I should go with.

Ian

Cheesy allready said what he thinks is close to what JHB uses. I believe he knows far more about cermet composition than I do. I will say that maybe instead of NiCr for the greatest ingredient Cr3C2 is used because JHB says there coating has carbide in it, just like (maybe exactly?) the cermet Mazda used.

I just found this cool site with magnifide samples of different thermal coatings.
(It has a lot of info on the process and methods of aplication as well!)

http://www.gordonengland.co.uk/pmg21.htm



I would be very interested in seeing some more pics, especially of the exhaust port side of the housings. Did you put the factory 2mm bevel back around the opening? (or at the very least on the closing edge of the port)

I don't want to be sounding like a lawyer, but you did say on now's thread...
When I said chipping I wasn't thinking of anything larger than 1mm. Are your seals reusable or aren't they. Being "scored" and being "fine" are two very different things to me.

Please don't take all this offensively. I'm just one of those (sometimes annoying) people who are always too particullar or meticulus about most things.
I get reprimanded alot for taking to long do do stuff or making it more complicated than it really is. (like my posts for example)

when I first looked the apex seals did appear scored,but once stripped,they were very smooth.Suggests that it wasn't the apex seals alone affecting the coating.
I have seen housings scored badly with different apex seals,but this wasn't like that,it had worn off and it appears it wasn't hard enough to damage the apex seals,but hard enough to score everything else.

Kinda sorta offtopic, but anyone know if it'd be feasible to get these cermets to bond to, say, aluminum?

They can be made to bond to aluminum very well, especially if a bond coat is applied to the surface before the functional coating. the bond coat i have used is a twin wire Ni-Cr coating with a bit of Al this gives an exothermic reaction (gives off heat) on the surface. Alot of production piston engines have a coating sprayed directly onto the aluminium bore, these sort of processes are relativly common

Eeeeexcellent. That solves so many problems I was having with some of my wackier ideas...

Hey Cheesy, hows your coating? Tim is looking at a few poduction processes and materials next week. Looking forward to seeing some results! Anyone else have any results from coated housings

I havent got or tried any of the JHB coatings, im testing coatings (and seals) for the pivotal engine for my masters in mechanical engineering. From the sound of it the PS304 coating may be similar to the JHB stuff but it may also be completely different. In the conditions encountered in the two stroke engine the PS304 wears out the compression seals pretty qucikly until it has run-in and it will wear out a couple of sets doing this, although the higher temps in a rotary may mean it will work better, the coating that has given the least wear on the seals is an iron, iron carbide, iron oxide molybdenum plasma sprayed coating