peejay

I thought *all* SA apex seals were 13B 2mm? At least they definitely aren't going to be making any 12A seals.

Feeler gauges don't lie but unless you can remove the seal and measure the seal groove with a calipers then you can't say for certain that the seal groove is worn out. Remember the edge of the apex seal is "razor sharp"... the only way I can think of that happening is if the seal was rocking around a lot, and it could rock more if the seal had lost thickness. I think. It's getting late, time for the bed.

bigmack000

lol i have a car :P its goin back into the same car. my uncle is goin to fix and reinforce the frame and if its doenst' feal rigth after. time to find a shell. yeah it shodul be good when i brign it back form ed for max to put back together.
joel

Tracy Crook

Hi Max,

I don't know what to make of your report (I quoted it below). Several things about it are very confusing.

I'm not saying that this isn't the truth but I can't imagine seals this worn (razor sharp edge, etc) making 100 psi compression even when cold.

The statement about our brand new seal measuring 15 thou thinner than a used mazda stock seal is especially strange. Our seals are CNC ground to a tolerance of less than + or - .0003" from nominal (.076"). Either you got a defective seal set or I don't understand what you are measuring.

We have customers with twice this mileage who are not seeing this problem. Without further clarification or technical details I can't possibly make an assessment of what is going on. I'd sure like to see those seals though. If they are as you say (especially those new ones) we would gladly replace them at no cost.

Tracy Crook, Real World Solutions (Rotaryaviation.com)

Quote: 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...

rx7_turbo2

Excellent. Provided your uncle is carefull when he does the work he should be able to get the car back to an acceptable level. Once that's done your right it's time to start with all those mods you have planned.

I'm glad Tracy came in to post. I was not around for the comp readings. I was however there when a brand new RA seal was measured against a used stocker, it was definetly thiner, this was not done with just an "eye" the calipers were put on it. Perhaps as Tracy mentioned it's a defective seal, out of spec from the factory, Max has more than one unused RA seal not sure if he's checked them all yet or not. I think everyone agrees more will be revealed whent he motor is pulled apart.

bigmack000

yeha hes been doin that stuff and autobody for 25years so i think it will be doen right. mid -end of april i am getting 15 000 in so time to start pouring the cash into the car lol. shoudl be **** loads of fun.
joel

bigmack000

dp

jspecracer7

You need to re-read that thread. Judge Ito was referring to ATKINS apex seals, not RA seals.

Maxthe7man

I know its hard to imagine the seal being razor sharp, but its not the face that touches the rotor housing surface thats sharp, its the transition at the corner from the side to the face thats sharp, the actual face is still rounded, but even 100,000 km mazda seals don't get an edge on them like that....
I have measured my other set of RA seals and compared them to used mazda ones, and they are thinner than used mazda ones. 1.92mm vs 1.83mm..
When I get the motor apart, I can fully measure the wear on the seals vs the rotor groove, but from just playing with the feeler guages and and calipers, I can pretty much tell the rotors are now worn...
It took some work to find that the problem was the motor, as when the car was cold, I could reach in through the window , just turn the key and it fired right up, but it got to the point, where when it was hot, it would just crank and crank, and then I could tell by the way it sounded when it was cranking when hot, it had no compression. Let it cool, though, and the motor once again would have the even stong compression pulses, then I verified it with a compression tester... And I went in the exhaust port for a visual, after seeing a motor go 100-100-100 to 0-0-0 after 20 minutes of idling...
Someone said its because I was supposed to use new housings with them, not so, thats not the point of wear thats the problem, someone said the porting, not so either, I make the exhaust port taller slightly, but I also retain the camfer in the port design, and again not the point of wear that is the problem..
I am gonna pull the motor on saturday afternoon and I will have it apart that night probably, so I can see how the corner seals have worn as well...max

pp13bnos

iTrader: (1)

I'd like to see lots of pics too. CJ

kabooski

I had a motor that was very hard to start when hot
and would start right up when cold

turned out my Side Plates where warped

when cold the plates constrict
when hot they expand and do not privide a flat surface for the side seals and compression leaks out

scathcart

I just measured the thickness of two brand new sets of RWS seals, and got 0.076" on verified micrometer, which works out to be exactly 1.93mm. I got the exact same reading from a set of new Mazda 2 piece apex seals.

I currently have a couple engines running these seals with the two highest milage engines being a nitrous 4-port at 27,000 kms with 115 psi front and rear after using new rotor housings, and a large street-ported TII engine at 12 psi with 22,000 kms, also with new rotor housings, producing similar hot compression numbers.
Checking the build sheet for both gives tolerances for the rotor grooves were 0.002" for the N20 engine, and 0.003" for the TII engine.

I know RWs went through some slight seal changes. How were your seals marked? (felt pen dots, felt pen numbers, engaved numbers, or their latest version, stamped-dot numbers?)

scathcart

Just for verification.... This is a measurement with a digital vernier caliper, with the apex seal hanging to ensure the caliper was actually touching the apex seal.

fstrnyou

umm, after 20minutes of idling? if you actually had to turn the motor off after 20 minutes then you don't have 0 compression. a motor won't run on 0 compression, hell probably not even at 2.7 compression.

drago86

Kabooski did the plates check out ok when you measured them, and just warp under the heat? thax.

Boostn7

FYI: Also measured one from a new set(stamped #'s) and also came up with .076".

JD

kabooski

I think those plates came from a car that most of over heated

they also had deep marks on them from the side seals around the port

I swaped the plates and it was perfect after that

peejay

Once an engine's running, even with total **** garbage seals and housings, it will stay running.

The problem is in starting, since the revs are so low.

Heck, if you turn the engine slowly enough, even a "perfect" engine will have zero compression.

There's a big difference between 150ish cranking RPM and a 900rpm idle.

rx7_turbo2

Hmm it's begining to sound like Max has an old set that are not the same spec for whatever reason. It does not however explain why the seals and rotors were in spec with eachother when the motor was built and now 10000kms later their not.

rotariesrule

pj, an engine WILL have compression if you turn it slowly.

scathcart

Something isn't right here. How do you take out Mazda seals at 1.92mm width (assuming 0.002" clearance from stock seals) giving a groove width of 0.078" and then put in seals that have a width of 1.83mm and get 0.002" of clearance? Its impossible. The rotor groove would have to be 0.074" wide; smaller than stock!!

If you put in those 1.83mm seals, you would get at 0.006" of clearance on stock rotors, and likely 0.007" of clearance on used rotors. So... maybe you didn;t correctly clearance your apex seals when you assembled it?

scathcart

No combustion chambers seals 100%, and if you turned it over slowly, say, one revolution per minute, the compression would bleed out before it could even register one psi.
PJ is correct. Compression values increase with rpm, especially so on a rotary due to the huge increase in centrifugal force placed on the apex seals.

rx7_turbo2

I don't believe the used stock seals he quoted a measurement for came out of the same rotors the RA seals are currently in. There's more than that one motor at his house at the moment

scathcart

Even so, Mazda seals are known to be perfect fit everytime, and the stock apex seal grooves are constant.

rxseven

I agree, it does not add up. I am not suggesting that person is a liar but he could not have possibly had 0.002 clearance in a used rotor groove with 1.83 mm seals. As for the sharp edges, thanks for clarifying where the sharp edge was, it may also suggest lot of apex seal movement in the rotor groove. I am curious to see pics, please post pics of the seals and the housings, thanks.

rx7_turbo2

That's not tureHe's measuring and comparing the width of the seals against eachother (RA vs Used stock). I'm not sure your following what's being measured.