Audio Science

Hi guys. Its been a while. Took a vacation. Anyhow, I'm getting ready to rebuild my 13b. I'm curious about which to use steel or carbon apex seals. I'm hearing that the steel seals will begin to chatter at 6200 rpm. I'm either doing a big street port or as mild as possible bridge port. Unless you guys have some better suggestions on something. I want it to be able to be a daily driver if need be. Well figuring I was hitting 7500+ and pulling hard with stock porting I'd image that I'd be going 8000+ with a big street. So I'm figuring maybe carbon is the way to go? Does anyone know the drawbacks of each of them and which would be the best for my application.

Also If anyone who is really familiar with porting would be willing to give me a crash course on the theory of porting I would appriciate it. I have heard that if you extend the intermediate housing it give you more low rpm horsepower and if you extend the side housings it gives you more high rpm horsepower. Is this true? Also with my 13b being a 6 port is there any crazy stuff I have to do?

Thanks guys.
I apprieciate all the help
Oh and one more thing. Who would have the best prices on gasket kits and seals?

fcturbo2

did you still want my SE rotors??..email me back.

ScruffyChimp

Hi.

I'm sure someone who knows more about this than I will be able to offer better advice, but the Mazdatrix website says:

"Note: The carbon apex seals are designed for racing only. They seal better above 8k rpm due to their lighter weight. They do NOT last very long (20k miles on the high side), and do NOT seal well at low rpm's (like starting and at idle)."

http://www.mazdatrix.com/b3.htm

To my mind, 20k miles (and it sounds like they are being optimistic there) isn't very long if you are considering the possibility of using your car as a daily driver.

Bye,
ScruffyChimp

MAZMAN

carbon seals are used for engines reving past 8500rpm(race engines).
Stick with steals,and rev to 8.5k,that should be plenty if done right

Barwick

you could try Ceramic seals too.. but there's drawbacks to them too..

Audio Science

Wow 20k at best, that really sucks. Of course If I planned on rebuilding every year I guess it would ok. Ceramics are expensive, I'm not able to spend that kind of cash on a rebuild, If I could I might as well go with a TII for a rebuild eh. I've heard they can take upto like 25 pounds of boost or something like that. How about the 1 piece, 2 piece or 3 piece design? Which is the best? I really want to do this right guys. I'm tired of blowing engines. I'll feel alot more comfortable building it myself. I guess steel is going to be best for me then.

I'm going to need some se rotor housings too I think fcturbo2 might hook me up with a rotor or 2. So if you guys know of anyone.

As far as the seals and gasket sets I think the best deals I've found are at atkins rotary. The gasket set is like$135. Can't remember the cost of the seals.

smnc

Take a look at Hurley Motor Engineering

I'm thinking of going with thier Duplex Tip Seals in my rebuild and port next year.
Only problems with the Duplexes is that they only have them for 13B's (which I have), and you have to get your rotors machined to accept 3.5 or 4mm seals. Plus the cost...

That's okay tho, I'll just give up booze and food for a couple months, lol

For those of you less insane than me, their Longlife Tip Seals look great!

Hope this helps,
-Spencer

WackyRotary

well you've probably seen me rant on about bridgeports and rotaries through here. Here are the biggest and worst things about apex seals as I know it.

Steel Seals:$28X1Long lasting, chatter at higher rpm, good for boost, causes rotor housings to be worn down and flaking, 8500rpm limit, good daily driver seal.

Carbon Seals: $30X1short life, good high rpm sealing, bad lowend sealing, very little damage to rotor housings unless they break before you replace them, No boost allowed, nessessary for rotor housing matched bridgeports.

Ceramic seals:$200X1 need I say more? These are very expensive>$2000 just in apex seals?! Good for boost, I am unaware of there weight or how they seal at high rpm, how much they damage rotor housings.

Bottom line in my opinion: Stock-mild or extend port:Steel seals
bridge-PPort: carbon seals
Turbo anything:Steel seals or ceramic seals.
Money to burn:Ceramic seals!

If you don't want to replace seals every 20K or less, don't build a real bridgeport. Stick with a extendport or less.

Audio Science

Those duplex seals look bad ***. But I'm kind of digging on the long life racing seals. Price isn't too bad either. Are those steel?

Hey Wacky, What kind of rmp does your bridge idle at? And where is your power band. How often do you rebuild with those carbons and do you have both side and intermediate housings bridged. Do you know anything about the lower rpm horsepower, higher rpm horsepower thing I was asking about?
Thanks guys

WackyRotary

Well Audio: I had some bad luck today, my thermostat was stuck shut and it "bridgeport" started overheating. DAMN IT! I think that I bursted a inner rotorhousing o-ring that seperates coolant from the chambers. I started it after it cooled and its belching white smoke and was hard to start because the coolant was diluting the oil in the chamber causing low compression, so I will have to tare it down and replace them. Once it was started, it made power, but a huge white cloud!!! DUH!!!*()#. I will find out shortly how long carbon seals last, this was the first time I used them in one of my engines. Stupid thermostat!!!


But its idle was about 1900-2300rpm. It not high, its just a fact of life with a bridgeport, that were mine idles about. IT really doesn't matter as long as it idles!!!
Power: 4K-8.5KRPM. Peak power occurs around 8K and drops off after that. IT gets pregressively faster till you hit 8K at least at the extent of porting I have. My carb is too small, I will get a larger bore carb when money is avalible, so HP is not that great, I'd wouldn't even say a HP figure, because my guess may be way off! I did a chassis dyno run with my mildport and it was 130HP at the wheels. So you lose about 20-30% through the driveline, do the math. But I got 0-60mph in 6.5seconds roughly with the 12a bridgeport so far. Granted I am not very good at launching, shifting, etc.

Audio Science

Man wacky sorry to hear that man. Amazing such a small inexpensive part can cause so much damage. How long does it take you to rebuild it? The best 0 - 60 times I got in the se was around 7. Might have broken into the 6.9's a few times. It doesn't look like racing beat does porting on the 6 ports. Is it possible?

REVHED

You do know that you can't bridge-port a six-port engine don't you? If you want a four port 13B you can use the 12A plates with GSL-SE rotors and housings or you could get an early model (like Rx-4) 13B or maybe a T2 engine and some high comp rotors. But I if you don't wanna go to all that trouble I believe you can street-port the six-port engine with good results.

Audio Science

Hi there revhed, See there, Nope I didn't know you couldn't bridge a 6 port. I do have 12 side and intermediate housings. Think its a better idea to make it a 4 port?

REVHED

I'd definately make it a four port. That way if you street-port it and decide you want more power later on you can cut a bridge-port. As for the talk about apex seals I've been talking to a few engine builders over here and they say steel seals are fine for street use even on bridge-ported engines. As long as you don't hold the engine at high rpm for long periods.

smnc

In case anyone cares, the Hurley seals are made of a special cast-iron alloy.

rxtasy

i had my motor rebuilt in Sept/97 with 181,000 km on the clock.

i really needed my car back so i was being a pain in the *** about getting it done. my mechanic was waiting for some parts and said ' i can finish it now with another customers carbon seals, or get it done ???? when i get the regular ones in'

i said 'do it now!!!'

the car has a slightly 'lumpy' idle that nobody can fix, but other than that it runs and pulls strong from idle to redline.....in all those years it's started on the first try all but 6 or so times and that's because it was slightly flooded. it's always started within 3 tries. i don't race the car but i haven't exactly been kind to it either and no engine probs since the rebuild. it now has 265,000km so that 20k lifetime thing mentioned earlier must be 20k of serious racing.

oh yeah, it's an '85 GSL-SE. Not sure if that makes any difference to your decision, just thought i'd share since i have the carbon seals.

WackyRotary

Ok, for those who care, I found my bridgeport problem, it stems from a cracked rotor housing. I did think maybe these rotor housings may have been mildly overheated before I purchased them since they didn't slide easyly on the dowl pins. But there surface condition was excellent.

Once I had it apart, it was obvioius that it cracked near the leading spark plug hole close to the side of the inner rotor-housing o-ring. The 0-ring had a seperation there, which also explains why the coolant pressure was belching bubbles into the overflow resvior and over flowing and over heating.

Luckly I happen to have one extra rotor housing I already ported and matched to the bridgeport plates. Total cost of this ****. $75bucks for new inner-orings, tension bolt rings, and a pressure plate due to my carelessness! Oh, and may frustrating hours of labor by me! Damn it!

peejay

Says who?

https://www.rx7club.com/forum/showth...ridge+six+port

REVHED

Ok, maybe I was wrong. I quess there's a first time for everything. j/k Sounds interesting but I wonder what the power potential is like compared to a conventional bridge-port. The primaries on a six-port are tiny and by the sounds of what crispeed said you can only cut a small bridge next to the secondary ports. It would be interesting to see some numbers though.