ok can someone explain the 3mm seal. Is it the thickness of the seal or is the the measurment of the part of the seal that get out of the triangle?

what is the 3mm refering too.

if you blow your engine and have it rebuilt with 3mm, will it be tougher? Anyone ever blew a ported engine with 3mm on "normal" driving condition which means no drag at 22 PSI?

thanks a lot

puma

 

I'm not a huge expert on the internals of our beloved rotaries, so take this w/a grain of salt:

3mm refers to the thickness of the seal. 3mm is only needed if you want to run lots (read >~20psi) of boost. There are issues w/machining the interior of the rotor housings for proper clearance. If looking for seals, check into the ones I'm running; they're like 2mm seals on steroids and Dave at KD Rotary highly recommends them.

 

well the thing is that around here, we don't have anyone running 2mm race seals and i don't want to ship my engine to US.

that is why i was asking for 3mm

puma

 

as far as I know it goes like this...

Regular 3mm seals are used because you dont' have to replace the rotors, just mill them out to 3mm spec and save money (300 per rotor if you buy new rotors). It should hold a bit more boost than the 2mm but some say it has problems sealing during high RPM cuz the seal is heavier and might float.

Ceramic 2mm seals are very strong, possibly stronger than the 3mm ones, but very expensive. One set of ceramics for 1 rotor costs more than the whole set of 3mm for both rotors.

 

hey...just wanted you to know that there is a great thread on the differences in all the 3mm seals and 2mm seals...do a search for apex seals.

I just got the 3mm one piece ceramics....should hold on during high rpm boost abuse..heheh...I know you all do that too.

3mm two piece have better low end compression I am told. The one piece hold out better during high end stress.

both are stronger than 2mm seals.

get the ceramics if you can.


jason

 

ok so i read the threads

almost everyone seems to agree that 3mm isn't better and say to stay with stock 2mm

but if it is so good, why every engine keeps on blowing?

what would be the solution except for tuning to be sure the engine won't blow again

i know i know tuning is the key but i don't have a place to tune where i live and the closest one that knows how to do that is at 600 miles and some people think that he is not even good so...

puma

 

Hi PUMA,

I went with 3mm when I rebuilt this summer. I have not heard of any negatives, backed by evidence, on these. It is just a little insurance but they should be backed by higher performance springs and water seals. The rotor milling is no big deal just increase the slot width but there is a right way and a wrong way. Send a PM to ASTRO in Calgary, he has them I believe and RX7 Specialties in Calgary did mine. Happy rotoring!

 

One issue with upping to 3mm apex seals in that increasing the size of slot isn't necessarily as easy as it may seem.... This is why a lot fo 3mm jobs get botched.

Don't use the rotors from an '84 or '85 GSL-SE 13B. They came from the factory with 3mm seals (and are usually the seals that get put into upgraded FD rotors), but don't match up perfectly with the FD's 13B (They are heavier for one). I've heard horror stories about people doing that.

Don't just mill the apex seal slot up to 3mm... You have to match a centerline from corner seal to corner seal - it isn't necessarily straight across the rotor. If your corner seals aren't perfectly across from eachother and you mill the slot in that direction, your apex seal will bind and you'll loose the motor.

If it's done correcly, 3mm last longer than 2mm, but it is often not done correctly, so you see problems with the 3mm. Every argument against the 3mm can be put against the 2mm as well (chatter marks in the housing, etc.), so the only reason not to go 3mm is expense.

All this info came from a talk I had with Jeff @ Rotary Power. He's a expert machinist and rebuilds rotories, often times with 3mm seals. he claims that every 3mm motor he's built have outlasted the 2mm motors he's built.

 

hmm wel there is one thing for sure, i am not the one who will rebuild it, i will have a shop do it.

It will probably be one of them in calgary or toronto. Shipping to USA will probably be too expensive.

Actually what i want is the more reliable as possible, i don't think i will ever do more than 400hp.

All i can see is that 2mm vs 3mm seems to be a fight just like upraged twins vs single of frount mount vs stock mount.

everyone seems to have a different opinion.

puma

 

One question I've always wanted to know..

It seems to me that going to a 3mm seal would increase the compression ratio. Though not by much, obviously. Does it?