Information on Ceramic Apex Seals

[bill shurvinton]

So how come the mazda 767 which won at le mans and produced nearly 700HP from a NA 4-rotor not only used ceramic apex seals, but ceramic coated rotor housings as well?


As an aside on the hurley seals, I know people in the USA running huge boost on the 3mm seals with no problems. But if one does go it neither harms housing nor turbo, which cannot generally be said for the factory steel ones. In fact until very recently when there was a quality control problem a large number fo the big HP engine builders recommended hurley for that reason. If a seal goes a rebuild takes less than an hour ( NB this is a race engine).

[Carl]

In My opinion it very much depends how the seals go wrong in an engine as sometimes even Mazda seals just crack but do not disintigrate and then the housings and turbo are ok.Whoever say\'s that Hurley seals do not do any damage when they break has not seen what I have seen.Even the Mazda carbon seals sometimes do damage the housings on naturally aspirated engines,and they are much less likely to than any other seal out there.
It makes sense to me that rather than put in a weaker seal, in case of when it goes wrong it causes less damage, it is better to put in the best possible seals ie:ceramic, to try to prevent the possibility of the failure in the first place.
Anyway if the engine is setup properly with fueling and the like it should run happily for a long time,usually the poor old apex seal gets blamed for something that was caused by a poor setup externaly that causes the internal failure on the part under most stress, which is the apex seal.
Hope this info is useful.
ps the ceramic apex seals are stronger,lighter and lower in friction so can have higher spring pressure than any other seal which means that they stay on the rotor housing at revs and prevent preignition from happening.Heavy steel seals are prone to skipping on the minor axis and do not contain compreession at revs so well.
All of this does not mean that in some applications that Hurleys are not ok,just have diffrent problems that need to be taken into account.
Remember,there is no such thing as the perfect seal.
Regards
Carl

[Iwan]

OK... here I go with my broken english

so far, it was interessting to read all the posts.

First what I would like to ask is, in which process the seals was made?
Ceramic seals are nothing new. NSU/Audi was running engines with ceramic in early \'80s. The seals was not hole ceramic, there was coated in CVD process. Also the engine housing where also coated like the 787 LeMans engine.
So the next question is, of which material are the seals coated? Only Si3N4 (or Siliciumnitrid) is right, anything else will not work right.
another question is, which seals are used for coating? The best is, to take the stock 2 peace seals and coat it with about 0,05mm of Si3N4. One peace seals are not recomendet, but will work. I have never seen 3 peace ceramic seals.
They are new processes for ceramic coating just in test by Frauenhofer Insitut in Germany. The new process will coat in Plasma irradiated process. This is realy interessting thing, but with this technology you can coat only in 0,06mm which is to thick. Diamond grind together with this new process are tested now. I will get the price for this new coating process within next days. If the price is right, I will coat my seals and housing.

Regards
Iwan

[Carl]

Hi Iwan,
Nice to get your thoughts.
The Iannetti apex seals are not a coating but solid ceramic which are formed and then machined to size and shape.
They were developed in the mid to late 1980\'s by Francesco Iannetti,and the design now is better than in those daysss.
Kind regards
Carl

[Carl]

Hi Bill,
Sorry i did not pop into to see you after the Wellington country park show.
In reply to your post on the Mazda 787b engine only the side plates were coated in ceramic and not the rotor housings.
The apex seals were ceramic.Rotor housings were chromed as in production engines.
Kind regards
Carl

[Iwan]

Carl, thank you for the information.

Well my opinion is not to go for this seals. Chattermarks may be one of the results.

Black is Chromoxyd or something with about 90% of CR2O2 together with some another stuf to support the CVD or PVD process. This material dont support nitro usage.
Gray should be Si3N4 wich is mutch better!

By coating you Rotorhausing (not only the sideplates) you will reduce the motor temperatur. Why? Couse you will reduce friction. By using ceramic on ceramic you will have nearly no friction. So it is important to coate your rotorhousing.

The discussion about Hurly is funny. If you dont put the lambda over 1.0 Hurly seals will work fine. But going over 1.0 you will blow you seals. As I know, Hurly seals were developed by Daimler (Mercedes Benz) in early \'70s...

Regards,

Iwan

[bill shurvinton]

Now that is interesting. I keep meaning to pop over to a nitriding specialists a few miles away with a pile of bits for them to look at.

Of course if you coat everything with ceramic, where does the heat go? Only the rotor ( and therefore the oil) left

I will call them and report back on what they say (//www.eltro.co.uk)

Bill

P.S. Don\'t worry Carl, I\'ll just pop over sometime as I am \'at leisure\' for a while

[Iwan]

Hi Bill, be carefull! Ask only for SI3N4. What many companys do, them coate with Aluminiumoxyd, Al2O3 which is also called "ceramic". Not every company support Si3N4.

Ask for CVD coating. Plasma coating is a new process.... I\'m waiting for the price for coating my engine, then I will test the new plasma process. CVD is the best process for coating at the moment. 1000°C is to low.... them need a stronger laser.

Best Regards

Iwan