2mm or 3mm Apex seals---The Debate.
 

I am hearing conflicting stories from different engine builders. What is the best set up to go with for high boost/high horsepower applications? I would like to hear others opinions on this.

In my particular case I plan to run about 22 lbs. of boost in my 13b-rew. I was putting 413 to the wheels @ 17 lbs. before the rear rotor lost compression. At 22 lbs. I should be north of 500. This will be a weekend driver occasional track event FD3S.

Secondly, what builders would you recommend?

i like kdr but thats in PA...

i had 3mm and blew my motor.. one thing about 3mm is that if they break they will stay in place and not chew up the rotor//housing or spit it through the turbos... 2mm will i believe (from my understanding) but at the same time i went with ra super seals 2mm...........

research. this question has been discussed to death.


it's all about the tuning.



Here's some rotary rebuilders in your area:

IR Performance [Metuchen, New Jersey]
http://www.myspace.com/rotaryexperimentseven

PF Supercars [Frederick, Maryland]
http://www.pfsupercars.com/Mazda/

Rotor Sports Racing [Kannapolis, North Carolina]
http://rotorsportsracing.com/perform...ng/engines.htm

I never recommend 3mm... unless the rotor came with 3mm from factory (not milled down by someone).

There are ton of people who made 600+ with OEM 2 piece seals.. Unless you just want to say you have 3mm seals, i don't see a point.. And I'm sure someone on this forum will disagree.. so, its up to you do make the decision :)

When you do make your decision, I have dealt with brian at rotorsports racing and i would highly recommend them but hey thats just me.

this is all i have to say:

mazda has a higher budget for R&D than any rotary specialist could possibly imagine. internally, if it came from the factory like that and has proven to be effective to numbers above 600hp, i'm pretty sure that would be a reasonable route to take.

mind you, the 787b had 2mm seals too and that lasted 24 hrs of wicked abuse

Speak to Ihor or Rich from IRP as well. From what I've or heard from people around the forum, 2mm OEM seals seem to be favored alot. Have you though about using the Jesus seals?

I'm hearing more people switching to the ceramic seals lately.

3 mm are supposedly able to resist detonation a bit better. But either one will break with a good enough ping. Some people have said 3mm don't seal as well, plus the added cost of getting them milled. Adam of RX7 Specialties recommended the 3mm and said if the milling is done on the proper machine, which according to him not many people had, that sealing was not an issue. My engine has been lasting quite well with 3mm seals and is putting down a lot of power in a street driven car.

more 2mm vs 3mm debate: https://www.rx7club.com/rotary-car-performance-77/rx-7-specialties-apex-seals-418560/

They do, and not just "a bit"....I speak from direct experience, the 3 mm seals are more forgiving of detonation, there isn't the slightest question....during initial tuning my 3 mm motor (still running strong after four years of abuse) detonated several times at high boost and nothing happened, the 2 mm's in my previous crackerbox reman popped when I farted too loud, and the OEM engine before that similarly let go at mild boost (ran lean)

Is this the same research budget that brought us the plastic AST and a cooling system that didn't kick into high gear until 108 degrees Celcius (226F)? Or perhaps the budget that provided the water temperature gauge that moves from the central point right before/after? the engine seals let go? Or the . . . OK, you get my drift. But then again, this topic has been debated to death. . .

I understand your point.. but I believe regarding seals, mazda has the most experience and have ran more real test than any aftermarket company out there. To go by someone who blew their old engine with stock seals and new engine with 3mm is not comparable.. But what I could say is that you could make 2mm seals unbreakable but something else will go bad in return. The best balance of the two is proven by OEM seals...

1) Our '94's AST broke at 98K miles (not too bad). Replaced with a "B" revision OEM type. Try routing the hoses so they don't side-load the nipple(s).

2) OEM thermostat is spec'd to be fully open at 95°C (203°F), per 1994 factory workshop manual, page TD-4. (Can't find a gear shift in the cooling system, maybe I missed it.)

3) Non-linear temp gauges are pretty much standard... on the Miata, too. If you pay attention periodically to either the OEM or a linearized gauge, you will see it move before any real damage is done, even to the 13B. If you don't, well... we bought our '94 new, and the radiator started leaking (at 99K miles) before any overheating occurred. IMHO on a stock FD, the OEM gauge is not a real problem. For folks running southbound up the I-5 Grapevine at full throttle with 15 lbs boost, yep, you'd better have a linearized gauge, projected up onto the windhield! :tonque:

What the factory does really doesnt have any relevance to what any aftermarket tuner would do. The factorys number one concern is their profit. With that said it seems that people have had good and bad experiences with both sized seals. It really seems more down to the quality of the build, and the use of a quality tune. Also the normal reliability items seem to be a must.

^^This is incorrect.

We'll build using whatever seals the customer wants--I went with 2mm seals (Rotary Aviation super seals) in my build, which has a goal of 500+ rwhp. I like the stock seals alot for anything less than 400 rwhp. We also recommend water injection on just about any performance build, but that's another thread :D

This seems to be a very polorizing topic. I guess that's why I've been getting conflicting stories from different builders. In talking to Rotorsports (they built the last engine that blew after only 10k) they seemed to lean towards Ceramic 2mm seals. I had always heard they were only good for N/A applications. Fris at Lucky 7 seemed to indicate that OEM 3mm from the GSL-SE's were the way to go for high horsepower applications.

I appreciate everyones input. I know reliability really comes down to the proper tune, but detonation resistance is my #1 priority.

if detonation resistances is the main concern then you should just swap in a v8 and sleep at night.

tuning, tuning, tuning, everything else is a moot point. It's like asking which is better: Diet Coke or Diet Pepsi? 2mm or 3mm? Blue or Red?


you should be spending more time investigating aux injection with those boost numbers/goals and less worrying about which mm seals to use.

sorry if this comes across as rude but rehashing these same "which is better" topics that have been covered to death gets old.

So you're saying is it's just a matter of preference? I don't think so. There obviously has to be advantages either way. Maybe I'll just put green paint on them.....that would make them more durable......or would yellow be better?

It makes a big difference as I am getting ready to sink a large sum of money into ANOTHER rebuild....even after using aquamist.

413 to the ground at 17 psi isn't exactly setting the world on fire..... youre saying you blew the rear rotor *with* aquamist water injection?

I'd recommend getting a wideband hardwired in, as well as running an EGT gauge. I'd also look into a larger/more efficient turbo for your planned boost levels.

If you blew up with water injection, something in your setup is very wrong.

Edit: some more questions-- are you still on original engine wiring harness? original injectors? fuel filter changed? etc. I don't think different apex seals will help, you need to get to the root cause.

The only time we recommend 3mm seals is in track only cars that are going to be seeing 30+ psi of boost. This type of application requires that the engine be rebuilt often. The 3mm seals produce much more friction, since they are 50% thicker, this wears out housings quicker and generates additional heat. We get 3mm engine shipped to us all the time for low compression due to sagged/warped apex seals. This is typically caused by improper lubrication as the OMP does not supply enough oil for these seals. Our rule of thumb is that if you have 3mm seals you need to be running premix. Another huge drawback is that there is only one apex seal spring on most 3mm seals, this causes extreme amounts of chatter. It also is the reason behind the lower compression and harder starting. So if you are okay with having the engine rebuilt fairly often go with the 3mm.

For the majority of street driven cars stick with 2mm. We personally have 2mm seals in both our 13B-RE and 20B powered cars. If we believed that 3mm were superior in any way they would be in those engines.

Hope that helps.

2mm they are great im boostin 34psi on e85 and no problems with them

Please think about what you would have to do to the rotor to fit 3mm seals. A lot of times machining to fit 3mm seals on rotors that are originally made to fit 2mm aren't machined correctly.. Not only that, think about what you would have to do to fit 3mm seals... personally, I don't think its worth the time, money, nor do I think its a benefit to go 3mm. Its a preference thing and when you really think about it, it doesn't really make much of a difference.