Vagrant02_DRFT

how would these help??

PX Brotherhood

im gonna try and remember all the things people told me.....


https://www.rx7club.com/showthread.p...+seals+ceramic

https://www.rx7club.com/showthread.p...+seals+ceramic

https://www.rx7club.com/showthread.p...+seals+ceramic

jreynish

iTrader: (2)

they save you from having to buy new rotors because you can mill the ones that are shot out! Other than that they do nothing better than 2mm IMHO. Infact I believe 2mm is better than 3mm, but that debate has been going on for a very long time.

PX Brotherhood

the arguement has been going on for a while but.....

there are seemingly clear advantages as well as disadvantages to having them. you have to decide which set of pos/neg is right for your setup

RotaryResurrection

iTrader: (8)

Care to list the "disadvantages" for us?

It's time to dispell some misinformation...

PX Brotherhood

well for one thing i have no first hand experience with any negatives to the 3mm seals. but i have heard that when they blow they tear up your engine pretty good. dont really remember any other good case against them

cmjaure

I heard that pineapple makes a 2-peice that dosent cause to much damage if it goes. but I also heard that all 3mm dont seal as well as the 2mm. again just what I heard

RotaryResurrection

iTrader: (8)

They do. But, so do most all seals, regardless of size or composition. It's just realy hard to crack a piece off of a seal and have it bounce around inside, and not do any damage. And to say, "this seal will do less damage than that seal" is a moot point...one good scratch on a housing is no worse than 5 deep scratches...either one of them make it unusable.


See above.

I built a used housing engine with 3mm 2pc seals and solid corners (without the rubber chunk which is also rumored to help maintain compression at low rpm). With 27 miles on it, I compression tested it today with the mazda digital tester and got 8.4-8.8 all around, which equates to 120-125psi. Which is spec (or higher) compression for a new mazda motor with new housings and 2mm 3pc seals.

Next...?

EatRiceDontDriveIt

Just to ask, I rebuilt my engine 2 years ago with 3mm seals. I kept the car under 3rpm for the first 2k miles and then drove at a normal 4rpm clutch shift.

Is it worth it to do a compression test to see if Im getting good numbers or should I be ok?

RotaryResurrection

iTrader: (8)

IF it runs okay and does what you want, then just drive it. IF you're worried about it, then test it. There is not really any compression difference between 2mm or 3mm seals.

The only possible drawback for a streetcar is that at excessively high rpms (9k and up) the slightly higher mass of the 3mm's can cause them to float, unless you use a stiffer spring. This is not a concern for 99% of us. I think I've proven that there is no loss of compression or sealing ability with them, and I dont know of any other negative effects.

Icemark

Well don't forget the added cost.. There is a neg effect.

Not one of those cost effective items for most people with FCs to use 3mm seals unless they are building a extra high HP motor.

RotaryResurrection

iTrader: (8)

Say you have an s5 t2 engine, or an FD engine, that you blow apex seals on. Right there, you're going to need a rotor and housing, at a cost of about $200 each used, or $450 each new. Now, the housing you can't do anything about, but the rotor can sometimes be saved by milling. So you take the $200 you were going to buy another rotor with, and pay to get both rotors milled out for 3mm. THe seals themselves dont cost any more than 2mm's...and you spend an extra $50 in 3mm-appropriate apex springs and cornerseals...you've got an internal upgrade for $50 more than the standard 2mm setup would have costed you...and you can now feel slightly more comfortable when boosting or raising hell.

I mean, hell, even for a standard rebuild of a stock turbo engine, I don't know many that wouldnt be willing to pay out an extra 300 bucks for an upgrade that could potentially allow their engine to last longer.

I personally feel that all NA rotaries should be 2mm, and all turbo rotaries should have come stock as 3mm. I mean, mazda used the 3mm seal for the first 15 years of the rotary engine production, and those older engines usually lasted a bit longer than the newer ones with 2mm's. IT is not necessarily uncommon to find a well maintained NA with over 200k on the original motor, but it's totally commonplace to find a 200k+ 12a or early 13b.

Icemark

yeah I agree with that.

But if the motor is in decent condition, nothing blown, running at under 250-300 HP levels, wouldn't you agree that it makes little sense to rip apart the motor to replace the seals with 3mm.

Now if the motor needs work anyway, then that is another matter.

RotaryResurrection

iTrader: (8)

Oh, I'd never do the job on a motor that had good compression. ONly during the course of a regular rebuild. The rebuild could have been required because of oil seals, blown apex seals, coolant seals, or just plain weak compression...but that is a perfect time to spend 3 or 400 extra dollars and get a stronger engine. But, the NA's really won't benefit from it, unless you plan to really raise hell, or do a boosted or NOS application of some sort.

Hell, I think some builders, like atkins rotary, have went to building ALL turbo rotaries regardless of year or build level, with 3mm seals. I've halfway considered it myself.

BlaCkPlaGUE

So from what Im reading here, 3mm seals offer the following advantages

-Same compression
-Cheaper to buy 3mm seals for a rotor that had blown seals before
-Lasts longer

So why do they last longer, is it just becuase for boosted engines if they pre-ignite it can hold up to it better?
If it were a brand new TII engine lets say, as in brand brand new everything, would you recommend the 2mm or 3mm seals to go into it?

RotaryResurrection

iTrader: (8)

They do NOT last longer strictly from a wear standpoint, as far as the height of the seal or the rate of seal wear. They do last longer from a strength standpoint in that, even when worn down, it's harder to break a wider/more massive 3mm seal than a thinner 2mm seal.

Think of it like a 1/2" drive ratchet, and another 3/8" drive ratchet. Both operate with the same mechanism, and that mechanism will wear at about the same rate under normal use. However, when it comes time to really torque on the thing with a breaker bar, which one will break first? The smaller one, of course. Now, the smaller one is fine for daily use , but for the jobs that you know will require more power, it's not a bad idea to just go ahead and use the 1/2" drive.

VietFC

that's a great analogy.

BlaCkPlaGUE

So the real question is,

Why did mazda stop using them?

RotaryResurrection

iTrader: (8)

Because supposedly the 2mm 3pc seal does better at higher rpm's...and I suppose they thought it might last longer and wear on the housings less...but in hindsight, the opposite seems true, as we all know the corner assist piece of the 3pc stock seal tears the housings al to hell.

Mazda did a lot of stuff that was questionable. Dont get me wrong, they know their ****, they have done years and millions of dollars worth or rotary R & D, but they don't do everything right either. These are the same people that came up with the e-shaft thermal pellet, the 90" throttlebody coolant hose on turbo motors, the rat's nest of bullshit under the intake of every EFI rotary produced, etc. etc.

jacobcartmill

iTrader: (6)

i heard the blowby was a little worse with 3mm, but negligible.

i might be havin ole kevin rebuild my engine soon. i blew it up (rear rotor) the day after the dyno. (believed to be too much timing) and i've acquired a blown jspec engine as well that has 1 great rotor and housing, so i might use some extra dough and have ole kev pimp me some 3mm seals. i've been reading alot about em lately trying to figure out why everyone thinks they're so much worse and no one has any facts (besides the higher rpm -8500+- blowby) to scare me away yet.

HeffBoost

They only help if you need to save a rotor IMO. I'd never mill a rotor unless it needed it.

It's my opinion that the 2mm seal is better suited.

I think there's a lot of hooey mixed up in all the 3mm seal hype myself.

jreynish

iTrader: (2)

Well said, that is pretty much what I think, If the rotors are salvagable by milling for 3mm, then go for it, however if not then 2mm stock 2pc seals, stand up pretty well I would think , RE-A. uses the stock 2mm in all his race cars, for a guy that runs some pretty wicked cars, and undoubtably built a hell of alot of High end high power engines. But I can't say first hand myself I have no personal experience with 3mm, but physics seems to dictate otherwise, but in the end what looks good on paper doesn't always look as good in real life... could be the same to the versa.

BLUE TII

iTrader: (9)

From my limited experience with 3mm seals they require more lubrication.

I would recommend premix AND a OMP modified for more oil injection on a high HP turbo using 3mm seals.

Premix especially if you are running rich for boost.

A couple applications where I would choose 3mm seals over 2mm every time- carbon race seals and ceremic seals. With either of those the weight and friction is low enough in 3mm that there really is no downside and you gain strength.

capn

I think 3mm seals are awesome, especially mazda oem ones, i was reading an article about the 1st gen 13b engiens and it said that the 3mm seal was like blasted on the tip with an electron beam that strengthend the seal edge and lasted alot longer inside the engine. and i can see really NO disadvantages from using 3mm seals unless you are a race team that wants the least amount of rotating mass. and you dont really care about longevity of an engine as long as it will go past 9k rpms.

but all in all i see more 3mm seal engines running around with higher miles and more abuse then 2mm seal engines. thats all the proof i need, and as long as you use OEM seals i think you'll be in for the long haul.

luiml73

iTrader: (1)

Atkins also uses 3mm on turbo engines.

http://atkinsrotary.com/index.php?pag=9