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Best apex seals to use in an ITS engine???

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Best apex seals to use in an ITS engine???

Old 01-16-07, 12:25 PM
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Best apex seals to use in an ITS engine???

Anyone with any first hand experience and would reccomend a certain type/brand of apex seal. I am using used housings in decent shape if that matters. My thoughts so far are Racing beats carbon aluminum filled jobbies...any thoughts. My worries are that the rotors I am using are used, street rotors that have felt the wrath of the 3-peice factory seal. The outter portion of the apex seal grove is slightly opened up, somewhat creating a mushroomed opening. Not major but worht mentioning. Racing beat says that these are rather fragile...why I am concerned about longevity of these bad boys.

thanks for the time fellas. the engine is a 89 13b NA.


here is Racing Beat's description of such:
Carbon Race Apex Seals*
1986-92 Non-turbo (2mm)

These Race Apex Seals are specifically designed to replace the stock cast iron seals in engines operating near, or above, 8,500 RPM. These aluminum-filled carbon seals are a one-piece design, 2mm in thickness, and must be used only with our special Race Apex Seal Springs. We do not believe these seals are appropriate for turbocharged applications because of their fragile nature if subject to detonation.

We do not recommend the use of 3mm apex seals in the 1986-92 non-turbo rotor. If you experiencing apex seal failure, probable causes are detonation. Expensive machining costs withstanding, installation of a larger seal may only temporarily minimize the effects of this detonation.

Price is for one (1) seal. Three (3) required per rotor.

*Legal in California only for racing vehicles which may never be used upon a highway.




and yes...i searched

Last edited by bean13; 01-16-07 at 12:43 PM.
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Old 01-16-07, 05:43 PM
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http://itforum.improvedtouring.com/f...0&hl=apex+seal


Great discussion on apex seals related to your scope of use.

Breaks down to ceramics being the end all, do everything right seal. Only draw back is the money. But you can think of them as an investment. You should NEVER break one with an IT engine and they will last for multiple rebuilds. If you think you might run IT for many years they can end of ammortizing themselves over the long haul. If money isn't an object...

Carbon seals are the best budget seal. They work better than the heavy ferrous seals at the revs you'll be using your engine. They're very housing friendly.

Steel seals are heavy and will quickly ruin a new housing (chatter) when held consistently over 8000 RPM. IMO they are the last choice for an IT engine.

As for your rotors you need to be sure of what you have. There aren't any tricks to putting an IT engine together really. All the power is in the blueprinting. If the rotors are worn enough that you have concerns you need to find better ones.
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Old 01-18-07, 10:54 AM
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wow, great thread at that website, very informative. Do you or any of your fellow builders have any general reccomendations for dyno numbers with the RB carbon seals, i see they dont like detonation so do you have A/F ratios and timing suggestions...anytihng else for set up to, I realize every engine is different, just looking for a good place to start so I dont jeopordize anything. Thanks!!!!

I saw the previous thread about premixing but is there anything specific for carbons...can I (should I even) mix more than 100:1 in your respected opinion.
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Old 01-18-07, 12:27 PM
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Why not go for ceramics, they are down to around 1000, which is 4 times more than the carbons, but should last 10 times longer, be more ruged overall and certainly make more power than carbons, at least in the period after the carbon seals would have worn enough to seal poorly.
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Old 01-18-07, 01:32 PM
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if i had a grand to blow on apex seals i would, that would double the cost of parts for me....not an option at this point. wish I could......

and from what I have heard from fellas like mazdatrix is that they dont neccasarily make more power. But thats just what I have heard, never even seen a ceramic in perons so......
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Old 01-18-07, 01:59 PM
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Originally Posted by bean13
wow, great thread at that website, very informative. Do you or any of your fellow builders have any general reccomendations for dyno numbers with the RB carbon seals, i see they dont like detonation so do you have A/F ratios and timing suggestions...anytihng else for set up to, I realize every engine is different, just looking for a good place to start so I dont jeopordize anything. Thanks!!!!

I saw the previous thread about premixing but is there anything specific for carbons...can I (should I even) mix more than 100:1 in your respected opinion.
i think the carbons like a little more premix, or last longer with more premix.

we had good luck on our car, s5 engine, with 26btdc @13:1 afr, that timing made the best power FOR US on that dyno that day, the 13:1 was more for fuel economy than power, leaner+ s5 tank = one less pitstop in an enduro.

we were revving it to 9400, junkyard everything, with no problems
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Old 01-18-07, 03:17 PM
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I always run 100:1 with the carbons. Wear doesn't seem to be an issue.

Take it to the bank that you'll find best power with around 25-27* TOTAL advance between 5-8k rpm. Throw base timing out the window. You don't care about that. What you need to set the CAS for is advance at full load around 6-7k rpm. You really need a dyno to do this.

As far as a/f ratio I've actually found best power in the 13.5 - 13.7 range. Any fatter than that and power falls off pretty rapidly.

Don't worry about detonation. We always run 87 octane and I've pushed timing to over 30* BTDC total advance experimenting on the dyno and never had a problem. IT engines should not be time bombs and if properly cooled should last many seasons.

That said carbon seals are absolutely intolerant of detonation. I lost an engine a couple years ago when the cooling system developed a leak and quickly lost all the coolant. Oil temp never went up a degree and I reused the bearings...so the engine never got "hot". But the combustion chamber side of the housing got warm enough to induce detonation.

As far as power v. ceramics, I've always heard Speedsource quoting 175 whp (on stock ECUs) with their full tilt package. We've matched that with carbon seals. We've ran against several good Speedsource and SDJ built engines and have never felt like we were giving anything up. Keep in mind when you start talking about power the exhaust system is really the most important part of the puzzle.
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Old 01-18-07, 11:18 PM
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In that thread
Originally Posted by C. Ludwig
At somewhere north of 7000 rpm the ferrous seal tends to skip along the rotor housing because their inertia is greater and they can't change directions as well. This is not only bad for power but it will also ruin a housing. Higher spring pressures could counteract this but that increases drag which robs power, creates heat in the seal, and wears the rotor housing more quickly.
What about the Renesis which would have to be able to withstand closer to the kind of revs you guys put on an engine? Is that why they've moved back to 2 peice steel seals? I know they also use different apex seal springs.
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Old 01-19-07, 12:19 AM
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The renesis seals are much shorter, and certainly have less mass than the previous 2mm seals.

I think power when new is a wash between ceramics and carbon, but when the carbon seals are well used they will be giving up some power. My experience with them is second hand and fairly limited,
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Old 01-19-07, 04:29 AM
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Mazda oem seals is what I use...

Jay7...
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Old 01-19-07, 04:49 AM
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Originally Posted by slo
The renesis seals are much shorter, and certainly have less mass than the previous 2mm seals.

I think power when new is a wash between ceramics and carbon, but when the carbon seals are well used they will be giving up some power. My experience with them is second hand and fairly limited,

I agree. Again, one of the high points of ceramics is that they don't wear much at all. Carbon seals are the quickest wearing of the three.
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Old 01-19-07, 10:58 AM
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Originally Posted by C. Ludwig
I always run 100:1 with the carbons. Wear doesn't seem to be an issue.

Take it to the bank that you'll find best power with around 25-27* TOTAL advance between 5-8k rpm. Throw base timing out the window. You don't care about that. What you need to set the CAS for is advance at full load around 6-7k rpm. You really need a dyno to do this.

As far as a/f ratio I've actually found best power in the 13.5 - 13.7 range. Any fatter than that and power falls off pretty rapidly.

Don't worry about detonation. We always run 87 octane and I've pushed timing to over 30* BTDC total advance experimenting on the dyno and never had a problem. IT engines should not be time bombs and if properly cooled should last many seasons.

That said carbon seals are absolutely intolerant of detonation. I lost an engine a couple years ago when the cooling system developed a leak and quickly lost all the coolant. Oil temp never went up a degree and I reused the bearings...so the engine never got "hot". But the combustion chamber side of the housing got warm enough to induce detonation.

As far as power v. ceramics, I've always heard Speedsource quoting 175 whp (on stock ECUs) with their full tilt package. We've matched that with carbon seals. We've ran against several good Speedsource and SDJ built engines and have never felt like we were giving anything up. Keep in mind when you start talking about power the exhaust system is really the most important part of the puzzle.
yep you'd know if it was detonating with those seals! the stockers prolly would just not last that long, or the failure would look like something else.
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Old 01-19-07, 02:24 PM
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I have ceramics in the bridgeport. They like more timing, they need more time to burn off the fuel mixture. On the dyno we went all they way up to 38*L total advance then backed off to 36.5* for a saftey margin they can take more PINGS, and if they break due to abuse or FUBAR, they *poof* into powder and don't eat the rotor or housings like a steel seal. it's a long term investment.

they last a LONG time as everyone said. most all of the star mazda motors (na 13b 6port) get rebuilds due to apex seals which are stock steel.
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Old 01-20-07, 10:22 AM
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Funny how timely this thread popped up. I have an issue with a customers engine and I thought I'd share what I've seen.

I'm freshening an engine built for an ITS car. Background is that the engine had relatively low hours before it detonated on the front rotor. We believe it was caused by a fuel system issue. Now that I have the car in hand it looks like it has many fuel issues! The engine was built with new rotor housings. It runs the stock MOP and no pre-mix. Upon removing the carbon seals I noticed a visual difference in the height of the seals from the front rotor versus those of the rear. I measure those seals and a set of new carbon seals. Results:

New .336 - .337"
Front .332 - .333"
Rear .315 - .316"

Yeah, I could see .020"

The fact that the rear wore much more than the front led me to believe that the only possible cause could be lack of lubrication to the rear rotor. I called Racing Beat and had a fairly long discussion with Jim Tanner. I first asked him what the wear spec was and to my surprise and disappointment he couldn't give me a firm answer. He even put me on hold while he talked to their "other engineer" (I'm assuming Jim Mederer) and still said they did not have a number they could give me. He did tell me that you could expect around .002" of wear per full season of use. But we still have no idea how long you can run them before the spring pressure goes to crap.

Then we discussed the varience in wear front to rear. In a nutshell he said it almost had to be lack of lubrication. He said a cooling issue could lead to increased wear though. IMO though it's unlikely one rotor would run that much hotter than the other. Since this engine was run with the MOP and not pre-mix it's almost too easy to conclude that the rear rotor was being starved of lubricant for some reason.

Lastly, I asked him what he recommened for a pre-mix ratio. He said they start at 3.5 oz per 5 gallons of fuel at stock power levels and increase the ratio from there. He recommended synthetic 2 stroke oil. Unless my math is way wrong that appears to be about a 186:1 ratio. I've seen ratios of around 150:1 in prep manuals FWIW. That is what I have run in my own ITS engines even though I recommend 100:1 to be on the safe side for customers. In the end the somewhat standard ratio of 100:1 should be quite sufficient.

The moral of the story is that carbon seals can wear at an alarming rate if they are not properly lubricated. The good news is that the rear housing still looks brand new. So can it be inferred that carbon seals are fairly gentle on the housing? I would hate to think what a housing using steel seals would look like when starved for lubricant!
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Old 01-20-07, 12:05 PM
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just more fantastic advice from C. Ludwig.....never fails to come through!!
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