Every shop tells me different things about the apex seals. Dave at KDR said engines with 3mm apex seals loose compression after a thousand miles and that 3mm Hurley seals are excessive. He also said the best thing to do is to go with 2mm Hurley seals. Rotary shops in Cali, however, (Rotary Power, Fast Freddys, XS) insist on 3mm seals because they are less likely to blow during detonation. Also heard that 2mm are better quality. Have'nt talked to MazdaTrix, but heard they use 2mm. Can somebody that knows their **** clear this up for me? Also, I'm going single turbo, either to4e or to4s from XS if that makes any difference.

 

You actually typed the answer and didn't realize it

If you're going to go single turbo, you're going to need an aftermarket ECU. As long as you have your fuel maps set correctly, you're not going to get to the point of detonation.

There's always a BUT and the one for this situation is: how much boost do you intend to run? Once you get up around 20 lbs you may want the 3mm seals but I believe there are several people running +20 psi on 2mm seals.

 

BS.....I hear this from morons all the time..If you get detonation it will break a 3mm fast, instead of 2 pops it will break on the 3rd...If the 3mm was so great why did mazda go to the 2mm in the highest performance car it ever built (3 gen tt)..????? The 2mm can take over 1000 hp....

 

I agree I had 3mm apex seals and let me tell you if you detonate, those things are going to spit out and into your exhaust turbines. Save the money on milling out for 3mm and use it towards tuning your stand alone. Go with hurley 2mm with double springs. Can you really argue with Dave at KD =D =D

 

This is an interesting thread, I always though 3mm apex seals were really only used when the housings were worn to the point that 2mm seals wouldn't seal properly anymore. I would have to imagine though that the extra 1mm of seal size wouldn't give you too much extra protection against detonation. The real solution is to have the car tuned properly so you won't have to worry about detonation. That's my (pretty much worthless) $0.02.

 

Here's my 2 cents:

Regardless wether you go with a 2mm or 3mm it all boils down to the correct
air fuel mixture. Either 2mm or 3mm will blow if you don't get correct A/F mixture
at that specific boost.

So what are the advantage of 3mm seal:
1) The rotor groves are already worn out. Instead of buying new rotors,
just have it machine to use a 3mm seal -- save money.
2) Probably has a bit higher tensel strength compared to 2mm. That
extra 1mm thickness will probably help. By how much? hmmm...
3) From 2 above, gives owners a sense of security that thicker is stronger.

So what are the disadvantages of 3mm seal:
1) It doesn't seal better as a 2mm seal. Mazda used the 3mm on the GSL-SE,
but returned to the 2mm after that model.
2) It has a higher mass. At high RPM, it will float againts the rotor housing that
can wear out the housing faster.
3) Misconception that a 3mm can be taken to a higher boost than a 2mm.
2mm has been taken to 26psi with no problem - as long as correct AF.

If you are looking for a better seal, I say you go with a 2mm ceramic seal.

just my 2 cents.

 

I was a little confused in the begginig but rx720bt cleared it up. Plus that 20b single turbo in his sig scares the living hell out of me so I'll take his word for it. So basically the apex seals aren't a big deal and where you gain a margin in protection agains detonation, you loose in perfromance?

 

Even PFS runs over 20psi on the 2mmers. It's ALL about the tuning. You blow a seal, and you simply weren't tuned right.

 

(1) The problem with going to a 3mm to save money is cutting the grove in the rotors to accept the bigger 3mm seal. It has to be EXACT..If it is 1/1000 off your engine will not last...Ask Peter Farrell, Dave at KDR or Cameron Worth what they think and why they stopped using 3mm.... (2) The oil metering system is set up for 2mm seals not 3mm so you are adding 50% more seal and weight but no more oil to the seals/housings...You get chatter and will have problems (most shops don't even realize this) (3) Prior to 1986 all apex seals were 3mm they didn't just put 3mm in the gsl-se... (4) Ceramic seals are a waste of time and money...Just buy stock 2mm or 2 mm hurly seals and get the fuel ratios correct......

 

For item 1) I don't think it has to be 1/1000 of accuracy. I'm pretty sure 2/1000 or even 3/1000
and you should still be okay. Check out how
Hurley does their rotor grinding. They do it
with a surface grinder and not with a CNC
machine.

For item 2) The last time I checked 1 - 2/3 is
33% and not 50%.

For item 3) I stand corrected. I'm not old
enough to remember beyond gls-se.

For item 4) I have to disagree.
* Ceramic seals are not a waste of time and
money. In fact the opposite is true. It will
save you some unecessary rebuild due warping
of metal seals. Ceramic seals can withstand
higher heat than metal seals. Wherein metal
seals when cooling down can warp.
* Ceramic seals has a lower mass...
* Ceramic seals can be reuse in every rebuild.
* Ceramic seals has lubricating qualities. It does
not glow hot to dry up the oil on them.
* Ceramic seals has a higher detonation tolerance
than metal seals.
* And if ceramic seal blows, oh well, it will be
just like the metal seals. -- You end up needing
a new rotor housing anyways.

The only drawback I can think about ceramic seals
is the cost. If cost is a concern, I pretty
sure the 2mm stock seals will be just fine as
long as you got the correct tuning. But if you
are looking for a "better" seal, then
ceramic is better -- Why did Mazda use that
in their Le Man's winning car (787B - 26B)?

 

Mr rx-7 tt you said

what kind of problems are you talking about. Can somebody give an example of their engines going bad because of improperly grinded rotar housings that were fitted with 3mm seals? Could it somehow lead to bad water seals? Or compression being dumped into cooling system?

 

if your going to do all that machining why dont you put the 6mm stock seals in there they are lighter than the 2mm ones.

mike

 

I've never heard anything negative about 2mm Hurley race seals. I went with them during my rebuild. About a year ago I had my car up at KDR and he had about 5 or 6 FDs up there with 3mm that let loose on them at like 1000 miles or a little more. The Hurleys are definitely a much more durable seal when compared with the stock 2mm. I've never seen a 3mm seal but have heard MANY bad things go wrong with them. I'm sure A/F has alot to do with it but there is a reason why most of the popular FD tuners don't use them anymore.