[PICS] - Cracked in half seal VS Non-camfered port job
 

Well, a few of you wanted to see this comparison. Not sure if it had much to do with the seal failure because I did have some pinging in the engine. However, it is all speculation.

For comparison read this thread on exhaust porting.
http://www.nopistons.com/forums/inde...pic=31895&st=0

This is an Atkins rebuild and one other on the forum said their exhaust port job didn't retain this stock feature. Which could have been a contributing factor to my failure.

http://img.photobucket.com/albums/v2...xhaustPort.jpg

I did just get off the phone with Josh at Atkins and said they have a different guy porting now and they do replace that stock feature...

James

Oh, this is a continuation of my previous thread.....

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/%5Bpics%5D-pulled-apart-my-blown-engine-56k-maybe-378432/

James

Awesome linked thread...learn something new every day. How many builders on this forum re-bevel their exhaust ports after opening them up?

I do. :)


-Ted

i do

all of them should

I do (not a builder except for my own car), because it's PROPER.

Anyone that ports the exhaust and doesn't rebevel it shouldn't be porting, even their own engine.

I'm glad Atkins has a new porter that does do it properly.

do you have to rebevel if you aren't porting the exhaust?

No...

When you port the exhaust you take away the factory 2mm bevel around the exhaust port leaving a sharp edge. So if you port the exhaust you have to add this back so the apex seal doesn't hit the edges of it. If you're not porting the exhaust then the factory 2mm bevel is still there.

ahhh ok thanks dDub. Just wondering for later on if I descided to take the rebuild plung myself ;)

Note that this is not really important on the leading (lower) edge of the port.. the seal just begins to expand outward as it hovers over the open port, and keep in mind that at a decent rate of speed (rpm) we're talking thousandths or ten-thousandths of a second, and the metal can only expand at a certain rate...so it's not like a rubber band or something. So anyway, the really important area to bevel is the closing half of the port...the sides and closing edge (top) need to gently nudge the seal back toward the rotor, which is what the bevel does. I usually give about a 1mm lip there and havent had any problems.

No problem.

But as long as you're in there doing a rebuild why not port it too? :D

I know I know, I would kick my own ass if I didn't port it while I was rebuilding it but me and die grinders are not very friendly :) Porting seems like something that a pro should do.

It's not as hard as you think, as long as you go slow and are careful. I was scared as hell when I did mine, but here I am with my break-in over and a ported motor and all I can think about is opening it back up to go slightly larger on the front/rear plates and much larger on the intermediate plate :)

That's the same story I got. Well, it was more like "I had someone else doing all the motor work because I didn't have enough time"

how long ago did you get the motor done?? i think mine was ordered prolly 1.5 years ago.

thats cool! Do you have any pics of your port job?

I would say about 2 years ago. It does irritate me slightly to know that their porter was not in the know when he was doing his work.......

Oh well...this is now..time to get over it

James

oh, yeah, i'm well past all that now, i didn't even bother sending it back, i just rebuilt it the way i wanted and it's been fine since.

here is a theory that sounds like it jives with the picture posted for this thread.

softer apex seals without a beveled exhaust port will 'chip' when they contact the exhaust port with no bevel because it is striking the port as it heads upward. those 'chips' out of the apex seal may not be large to start with but without the contact to the rotor housing to cool the seal it is being blowtorched by the combustion process and more and more metal is taken away as the engine is run especially at higher RPMs where the temps are hotter and more static compression is being built.

so, yes, always bevel your intake/exhaust ports.

Since some us in the begining wondered why the seal failed lenghtwise....this might add some more to it...
http://www.atkinsrotary.com/index.php?pag=40-9

James

Sounds like they are trying to blame something else other than themselves...

It could be they are blaming the EFFECT rather than the CAUSE...

Think about it.
The apex seal is slamming into the sharp edges of the exhaust port.
This causes the apex seal to "wobble" in the apex seal groove in the rotor.
...causing the apex seal groove tolerance to widen over time.

duh


-Ted

so they are telling you that because they did shitty ports before and your motor failed over time because of this, they still will not do anything about it, not even offer you a huge discount on replacement parts?

I never tried to get anything from them.....

Maybe I should....

At this point I don't care.

James

I can totally understand what you mean, I wasn't asking if you went after them... but rather that they didn't impose compensation on your! know what I mean? Maybe I am being unclear? If I am just let me know I will try to explain what I mean in better terms.

Nah, your fine.... when I initally called them I assumed it was compeltly detnoations fault. Then, after reading more posts I realized it was ONE of the reasons the engine failed so soon.

James

It can't be detonation.
I've detonated my engine hard twice after a fresh rebuild with no signs of damage.
I've torn the engine down due to unrelated problems, and the Mazda OEM apex seals are fine.
I'm even using the older 3-piece design.

We've killed motors under detonation, and it never kills the apex seals like that - at least Mazda OEM ones.
Most of the time, it chips the corners by the triangle assist piece.
Else, it cracks the apex seal in half vertically.

The Atkins apex seals are either very soft and can't take ANY detonation, or everyone that's telling you the seals died via detonation is full of shit.


-Ted

I bought a car with an atkins rebuild that look just like the ones on atkins website. I think it was detonation that killed the atkins seals in my engine, two of the corner seals were cracked pretty bad. The atkins seals are pretty weak. One cracked so bad that the top part of the seal actually came out of the seals and ate up the turbine wheel. I took one of atkins seals and you can actually bend them, and they stay bent. I tried bending a mazda one and it stays flat until it breaks. The dont bevel their exhaust ports. Their ports dont even look anywhere close to being the same. They dont blend the top of the intake port so when the trailing edge of the side seals goes over the top of the port it slowly wears out the edge of the side seal. I wonder whats the quality of their solid corner seals?

I wonder if the detonation was caused by hot spots forming on the edges of the apex seal as it slowly deteriorated over time? Sounds like the builder is at fault here and has admitted it, the next logical step is them compensating you in some part for the f*ck up.

-jb

I would agree^^^^ I would hit them with a "Corrective action" form. That will get the top quality mgr. involved. You would at least get something. I mean Why did yoou by from those guys??? becuase you were under the impression that you were getting better than average quality and you paid for it as well.........

You stepped up and paid, now its time they stepped up and earned that extra cash.

It's so obvious to me that the unchamferred port is the cause of that destroyed seal that I can't believe there is any argument at Atkins. They F'd Up the porting. Period! I cannot believe the frequency of half-assed work we find out about here from the supposed "experts" at the name rotary shops around the country. Really discouraging. Gotta learn to do it all yourself.

yeah, if they didnt edge the ports, thats their fault. its really obvious what broke that seal.

as far as atkins and detonation, a softer seal should take detonation better, assuming the material strenght was the same, because it would be more ductile and flex rather than break.

pat

That's a lesson I learned long ago thanks to my friends' misfortunes with paying people to do what a motivated person could learn by themselves.

Did your housings get chewed up in any way by that mistake? If not, the cost to put that all back to gether shouldn't be too bad, right? Just have to bevel that port as it should be, then get a couple of new seals. Do you think you'll go with Mazda OEM apex's this time around? I've done alot of pre-rebuild reading and it sounds like they're still the best you can get for street application.

I didn't want to chance using my rotors again incase they were out of spec in the grove. So, I traded my housings for a pair of S4 rotors and a front counterweight from that s4 engine.

I am going with new S5 housings.

Then for the seals I am going with RA seals and OEM springs.

We will see how that holds up:)

James