Rotary Aviation seals, a 10,000 km report.....
 

I recently just brought my car out of hibernation and have been driving it, at the end of last season, I had few occasions where it was a bit hard to start when hot..
This year, the problem showed itself just recently, and now has become a full time problem when hot... I did a compression test cold...
rear rotor 100-100-100
front 100-100-100

Got the car hot did a test..
rear rotor 15-30-15 or there abouts
front 0-0-0......

let car get stone cold and its back to 100's

took manifold off, inspected seals, all seal are there, all housing feel and look good with a mirror, edge of seals is extremely sharp like a razor blade....
Seal rocks back and forth quite a bit...
Measure a brand new RA seal, its about 15 thou thinner than a used mazda stocker....
Reassembled car, took for drive, at 12 psi, it makes enough power to spin the rear tires(275 40 /17's) at 60 mph.....its just hard to start...
took car apart again, got a long feeler guage and went in through the exhaust port, I have .007 clearance on the rotor to seal clearance..
Checking my build sheet I did when I assembled I was around.002 when I built the motor on 6 seal grooves...

This isn't lookin good, it looks like the hardened seal is to hard and eats the rotor groove... Its not any kind of omp problem, I premix at 125:1 or so, and always have..

Its wierd I can make so much compression with a loose seal, and when its hot, it goes to shit, but its like the seal is binding in the groove when hot...

I haven't talked to RA yet about it, I am gonna email them tonight, but it look like I am a couple of rotors, for this learning experience...Max

Poor hot-start is the first sign of an engine that is just plain worn out. Sounds like you're there.

How sure are you that it's the rotors that are worn and not the seals?

mine was like that too, easy cold starting and hard hot starting. never measure comp. when cold, but hot was 65 in front and 85 in rear rotor. then drove for about 30 minutes before it wouldn't run right any more and missed badly when idleing. so i can only assume the compression had severly dropped. i have a warranty tho, so maybe they'll fix it

Hmm, this isnt good ( i have a set of these waiting for me to assemble)

Did you add extra clearence for these seals? IIRC Judge Ito mentioned here or on nopistons that these seals expand more than other's when hot, maby this is leading to the increased clearnce issue, and also explain the no commpression when hot because the seals are getting bound up in the grove?

-Jacob

That's part off the problem. They expand more when hot, no question about it. That's got to be what's causing the sticking when hot. But it used to start much better hot than it does now. It must have something to do with the greater expantion when hot in conjunction with the fact the harder seals have "reshaped" the hardened groove of the rotor. The feeler gauges don't lie, plus you can feel it with your finger when you stick it in the exhuast port there is more "slop" to the seal than there was when it was installed and as Max said it's a few thous out of spec now, where as when it was built it was well within spec. It will be interesting to see what RA has to say about this.

I measured the rotors when I put the motor together, everything was well within spec, now its totally out of spec, I am 99.9% sure the seals have worn the rotor grooves prematurely, in fact its the only thing it can be, the internals of this motor were mint, when it went together, and ran great up to about 9900 km, then the compression started to slide away when it was hot... the edge of the apex seal is also super sharp like a razor blade... The apex seals are numbered, and are the proper length to begin with,clearancin these length wise would not affect the groove wear, if they were to long, they would scrub the irons and probably chip a corner isntead of wearing the groove in the rotor uniformly across the rotor width.. Go'in back to 2mm Mazda's next time....Max

If/When you hear back from RA, please post it up, or atleast pm me what they have to say

-Jacob

Razor sharp edge is what bothers me most about the report. The housings can't last too long without a radiused edge.

oh, i forgot to make note, i was only having the same engine problem but not becuase of RA seals, i have an Atkins motor.

mmm,.. glad i saw this thread, I wonder how 88intergrals's are holding up,.. time to order some Mazda OEM parts. Racing beat has the best prices on OEM rebuild kits right?

They did recommend that new housings be used!

Drat! I've got a set of those waiting to go into my rebuild. I think I'll go for something else now (Mazda or ceramics). Thanks for sharing your experiences with them.

-Max

I stacked some feeler guages on each side of the seal to see what wore, and the rotor grooves are taking the heat, the apex seal is not alot thinner than the new ones I have sitting in a bag, but the groove itself is about .0045 wider than it should be by the looks of it..
With a new RA seal in another spare rotor I have a seal clearance of .002, which is where my motor was on assembly..
A used 3 piece mazda 2mm in the same rotor give me a clearance of .0015, which is a pretty good spec for a used seal....
This weekend the motor is coming out, and I will get to see a little more I guess....Max

I think artguy is using these too....or am I smoking something? CJ

Max thanks for your info.

This is not good, because I plan on running the motor hot alot at track events. hrmmm, maybe I need to stick to the OEM 2mms. (motor is being rebuilt right now)

Re: Rotary Aviation seals, a 10,000 km report.....
 

Hey Max,
Was your rotors 2mm or 3mm? I have seen excessive wear on rotors that was milled to 3mm incorrectly. I find it hard to believe that it could create so much wear with the RA seals in less than 10,000 km....

I think you might have another problem. Its just hard to believe that would happen so fast. A milling problem would cause the seal to chatter in the groove and could be responsible for the wear. You could also have a lubrication problem. You say you run premix, but what oil do you use in the motor? I have run mobil 1 15w50 for two years with no problems, but I have seen others run it and find excessive wear when they tore the motor down within a much shorter time period. Could it possibly be a clearancing problem? I know some seals like the Atkins have more thermal expansion than the stock seals, and require extra clearancing. I just spoke with Judge Ito and he suggested .002 thousanths between each side of the apex seal and rotor groove and clearance the apex seal length 1 and 1/2 thousanth shorter than the rotor width. Also, you say that the apex seals were razor sharp? If they lost radius, then it could be a problem with the porting. The factory exhaust port has a 2mm bevel where it closes to prevent the apex seal from hitting a sharp edge as it passes over the port. If the motor was ported and the exahust port not re-beveled, it can lead to premature apex seal wear and loss or radius. I am going to give it a shot and see what happens. I'm not saying your full of it, I just hate to see everyone jump to conclusions when one or two people have a problem.

I have never liked apex seals with the large end piece.
The problem as i see it is that as the seal thermally expands
it displaces the corner piece in the only direction it can go,
which is up and away from the rotor housing, now with the
mazda small corner piece this is not a big deal because the
corner piece is so small the amount of compression lost due
to the small corner piece moving up equates to a very small
amount , but the larger corner piece allows almost a centimeter
of area to loose compression through, which could account
for no compression while hot.
I can not understand why everyone insists on making large corner pieces
I have heard that they reduce the wear line that the small piece
causes, but does it really matter if there is a little wear line at the
edge, or is it better some how with a wear line a centimeter
away from the edge?
I believe that the AR seals are a very good product but added
end clearance might be needed in some applications, and i wish
that the makers would do a news release with the recommended
clearances.
my 2 cents
matt

Agreed.
First time I saw this design was with the Hurley stuff, and I couldn't understand what twisted logic was behind such a design.  Sure, you don't deepen the existing groove, but you take such a significant hit in compression loss it sounds like the greater of all evils.  But then again, they touted their minimized-housing-damage when their seals let go, but I could never understand what a blown motor with no internal damage gets you in terms of a "plus".

I had my doubts on these RA seals ever since I started hearing about the "700%" claims.  I think I even posted that I would worry about premature rotor apex seal groove wear.  This thread is just a very bad sign... :(


-Ted

What about cryotreating the rotors? I have a source to do it locally and might give it a shot. If the rotor is made harder it should combat the problem if indeed the seal is too hard wears the rotor. After all, you want the seals to wear, not the rotor or housings. Also, how much breakin time did you give the motor? From my experiences only a couple hundred miles is needed for stock seals, but I was going to give the ra seals about a thousand to set.

Yes this is making me uneasy considering I have a set of 2mm ra apex seals waitin for my 88 frankenstein motor.... grr They did however say breakin was extensive so I guess sense I already have them I might as well give it a shot.

The stock 2mm Rotor grouves are already hardened! That is why I can't see using 3mm is doing anybody any good you are removing the hardened material! So cryotreating a rotor might make a little better for a little while! then we are going to have issues just maybe a little bit later on!

so max you goin to figer this out before you build my motor. i hope you can figer out whats goin on. shoot me a pm or give me a call and tell me whats up and stuff.
joel

Double post :D

I could not agree more about the 3mm issue. I've been over it before no need to do it again.

So to answer a question asked above the seals in question in Max's motor are 2mm. I really can't see this being a porting issue, nor a lubrication issue. I've seen the insides of the motor and how it was put together.

Feeler gauges don't lie, but all this is being done through the exhuast ports. Once Max gets it all apart to look at it I'm sure he'll give us an update. I was almost going to go with RA seals as well and have decided to stick with my stock 2mm 3pc. I don't think there's any need to push the panic button yet people. Lets wait till the motor is apart and perhaps some pictures can be taken. Lets not forget RA has yet to comment on the issue. It will be interesting to see what they say. It would also be nice if some people with similar milage (10000kms) would chime in.

Joel you need a car to put an engine in first;)