What's the concensus on this? Anybody prefer solids vs. stock w/ the rubber insert? I've tried both but not sure which is better, quite honestly.



B

Hey Brian. I don't know which is better, but when I use carbon apexes I like the thought of the extra support that the solid corner gives to the apex.



Gary

I have always wondered about this subject myself. Considering that the stock corner seals were made for three piece apex seals and many of us are using 2 piece aftermarket seals in our rebuilds, an engineering research paper appears to be in order. Anyone care to do the honors?

Hanging around IGY and Dragon, the general consensus is that stock corner seals work fine. I know that IGY bought solid corner seals for one of his bridgeport motors(I don't know the manufacturer) and they wore down very quickly. I know that Hurley makes a solid corner seal with a built in spring. I may try these out to see how quickly the wear down.

PHE 2000



.4mm wear in 700km

I've been running the stock corner seal with the rubber peice removed in a **** load of engines... most of them making over 400hp with no problems ever. I would suggest doing it like that.

With a 2mm seal? Wouldn't there be too much play?

The corner seals with rubber plugs have been used with both 3mm & 2mm seals. The plug has nothing to do with clearances only to help seal better when staring hot. For a street car it's a good idea.

That was my understanding: The rubber insert is there to help hold compression, especially on start up. They seem to work too.

PK797 NYC

Until it falls into your port getting wedged and blows your motor. Fine for a stock motor, will fall out with a big sideport.

Guess I will take mine out then! Never hear of it before though IGY

If the rubber of the corner seal is able to fall into the port at all

that only means you went to wide with your porting. But if you plan to go that aggessive with your porting the solid seals maybe a better bet. They may give you that little extra ley way that get you buy. I don't like to play the odds that close usually so it's not a issue for me personally.

That's funny, I thought the only time the port was to wide was when the corner seal fell in. I have experienced no hard warm starts, and the only times I have ever seen a cracked stock corner is when the rotor tip was bent from a broken apex going past it or the rotor hitting the end plate and bending the rotor tip. Basically something very bad happened first. I am basing everything I have said on things that I have witnessed first hand, not on something someone told me.



Has anyone actually pulled apart a motor where the only problem was a cracked stock corner seal? I am seriously asking this question because I want to know, not because I am trying to be an ass/*******.

A little added extra bonus! This took me a while to find.



"Then don't use the rubber piece!

I won't even use the rubber piece with a good street port!"



This a direct quote from an old post made by crispeed.



Here's the thread on the evil forum



http://www.rx7club.com/forum/showthread.ph...ght=corner+seal

Igy, I took apart a series 4 with broken corner seals, the rotors had been milled for 3mms.. There are two things about this motor which may have lead to the broken corner seals, first was there was only .001 clearance between the sideseals and the corner seals, so the corner seal was broken on that rotor side, exactly where the side seal points to it, so I am surmising that the side seals expanded and pinched the corner seal, breaking it...

There were no rubbers left in this engine, and it had been rebuilt about 10k km's before it let go, by a local shop...

The seal edge on the rear rotor had let go, and the apex basically folded over the rotor face, on a dyno run at 14 psi or so...

The other contributing factor that I can see in this motor, is that the rotor milling is in the wrong place, its offset instead of being centred, so when the apex seals are put in, they are very tight and hard to move because they are binding on the corner seal slot, which appears to be centred..All in all its a disaster of a motor, but it ran, although from day one it barely made 80 psi per rotor face with stock ports..Maxt

IGY

What I was talking about is, when you altering your intake port you can widen it to a point, without effect reliability, but beyond that point your going to run into a reliability issues. This as you may already know is especially true when it comes to the "opening" part of the port alone the long curve next to were the corner seal travels. If you continue to port (which you can if you want) past that point your going to run into a situation were your corner seal path now becomes smaller. Inevitablity if you continue even further with the width of your port one of two things is going to happen (in my experience). First your going to run the very real risk of the rubber part of the corner seal falling into the port. Jamming everything up and ruining your motor, or depending on how wide you went the whole corner seal itself may find itself a new home in your ultrawide port. Again ruining the motor. In either case you can't necessarily blame the seal. The seal is just going alone for the ride. It's up to you and your port design to make sure there is a large enough path for that seal to travel on.

What I also said was that if your going to go wide with your ports you may find better results with a solid seal, because while a soild seal may not give you the same compression numbers as the two peice, it may hold up better with your larger port configeration. P.S. I don't think your a a-hole and I hope this helps.

PK797 NYC https://www.nopistons.com/forums/pub...IR#>/bigok.gif

Yes, you can drop a corner seal into the port if you go out to much. This is a very big port. It takes very little porting out to drop a rubber piece. By running a solid corner I am not going to be able to port out any further than a stock corner with no rubber piece and there is actually less reliability when using the solid corner in my experience(PHE 2000 and Scoot). What is another reason to use a solid corner seal other than the stock seals crack, because the solids will fail just as easily as the stock from what I have seen.

Maxt, I have a friend that used to clearance his side seals until they snapped into place. He had alot of motors with cracked corner seals.

could you flip the corners over so the plug was on the inside, and didnt fall into the port?

It goes all the way through the corner seal.

What would be the clearence for the side seals?

I have had two failures of corner seals. Both the ones with the rubber plug. One turned back into the powdered iron it was made from. The engine stopped but it didn,t do much damage.



The other was just cracked into 2 pieces and found on disassembly.



I now only use solid corner seals.



I use zero side seal clearance. So long as they will pop back up when both the side seal and the corner seal is released as a unit, it will work fine. The centrifugal load will add a bit of clearance, and the the advancing side of the corner seal drives the side seal around, so that junction will wear in quickly and provide even more clearance. Instant hot starts after a heat soak.



If you can wear out a new set of solid corner seals in 400 miles, there is some untold story there.



Lynn E. Hanover

0 side seal clearance ? I'm rebuilding my engine right now. I followed the side seal to corner seal clearance told by the haynes. Should I use new side seals to have 0 side seal clearance. I probably will use stock corner seals without the rubber plug since I want to port the intake.

I didn't want to write up a long story like I first intended to. I'll say that they both work great depending on application(low boost vs high boost.... small nitrous shot vs a big nitrous shot) When using none solids corner seals, try and keep the engine away from detonations. They do not like detonation at all(they will crack down the middle) If your going to build an engine and go for extreme boost or nitrous shot I highly recommend solid corner seals. Basically solid vs none solids is up to the type of application your going to use the engine under. Stock rebuilds and light to medium mods= none solids... serious mods,high boost(30 to 40lbs of boost and/or 200+ nitrous oxide shot use solids).. hope this helped a little.

Sorry I didn't see this sooner.



There is no problem with the stock clearance specs you see in manuals. There is nothing quite like the insanity of racing to show up a problem with any piece of equipment.





A fresh engine has about 20 minutes to break in. Near the end of that time it will be turning up max revs. Maybe 9,600 RPM. So we get the clearance we need for near perfect sealing in short order. The clearance required to seal well is just that amount that cannot bind up the side and corner seals and prevent them from moving. There is a tiny amount of side clearance in the side seal groove. The centrifugal load on the seals tends to force them against the outside of the groove when unloaded. So zero static clearance still produces some clearance. They were at the drive end of the seal eats into the corner seal, and some of the side seal wears away to produce additional clearance. So zero becomes two or three thousandths on teardown. Still, once the extra clearance is established and some oil can get between the parts, the gap will not increase dramatically over a great amount of time.



These are like the gaps in a piston ring. The difference is that the piston is iron and changes shape at about the same rate as the seal. So huge amounts of clearance are not required. In my 3.31" bore Fiat pistons I ran .009" end gap on the top ring and .008" on the second ring. That would produce zero leakdown after a dyno run. And that with 245 pounds of cranking compression.



Extra clearance is not a problem, but it will not produce zero leakage, and zero is what you are looking for.





The picture is the chassis for the 95 RX-7. 135 pounds of SAE 4130 total. The idiot on the right is me. The idiot on the left is Craig Rhine the engineer.





Lynn E. Hanover

Something came to me as I re-read this thread...

If expense was not an issue, could RX8 corner seals be used in a large streetport application? After all the rubber plug has been replaced by a what appears to be a carbon aluminum plug that anchors from inside the Corner seal.

I also understand that the plug will have to be milled due to the apex seal height of the regular 13B and the Renesis.



Just a thought lets see what yall think about it.

Your theory here makes sense, but what happens with the side seal expands when it's exposed to the heat of combustion? What about combustion itself pushing down on the seal? I would expect that to easily overpower the centripetal forces on the seal from the spinning rotor. Perhaps Mazda's thinking of 2 or 3 thou static would become zero under the forces of compression and combustion.

So in my s4 13b block instead of replacing my corners because of lost rubbers i should put them in without? Its a large extended port?



http://img223.imageshack.us/img223/5021/dscf1279mq9.jpg

sorry bout the crap photo but should i reassemble like this?

Re: Corner Seals
 

How thick do may corner seals need to be rx8 2pc can not find this anywere