Apex seals?

[C. Ludwig]

So I'm building a motor or two and am trying to decide on apex seals. Hear alot of the big name builders hawk carbon seals. Now from everything I've read these are really only a benefit at high RPM and actually seal worse than stock at low RPM. Seems like 8500 RPM is the magic number where they are better or start to get better. Don't know about everyone else but until I have real dyno info to back up my butt I'm saying I'm out of the powerband by 8000 or so. Sooooo....

What's everyone's take on stock steel v. carbon? Don't even mention ceramic. Since the money is the same either way I just want the best seal for an ITS motor. Will the carbon seals allow the motor to make power past where it's falling off now or is the limit I'm feeling more of a function of intake, exhaust, stock port combo? Will any gains in the upper RPM range offset losses between 6500-7500? Thanks!

Chris

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Chris Ludwig
08 ITS RX7 CenDiv

this sounds like a question best answered by Dave Lemon of Mazdatrix.com, Dave are you out there?

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Daryl Brightwell
ITA RX7 #11
NORPAC
ITA RX7 #77
SOPAC

[Boswoj]

I've heard all kinds of things from different builders about iron vs carbon and the rev ranges that they seal at etc, etc, etc......

The biggest issues for me are about dollars and believe me, my budget is not of the unlimited variety. From what I have seen, and on the info from my motor builder, when carbon seals let go, they typically do MUCH less damage to rotor housings, cast irons, and rotors so more of those things can be reused in your next motor. That can mean a lot of savings on rebuilds! The down side is that carbon seals will sometimes fracture and the iron ones really don't so much. I guess the upside is that the carbon seals fracture instead of just hammering the groove in the tip of the rotor out until they can escape! The carbon seals are especially prone to damage from detonation - but a well set up, normally aspirated roadrace motor isn't going to have much of that. That is the real market for the ceramic seals - turbo rotaries running high boost are prone to detonation, and ceramic seals give a slightly improved resistance from what I hear.

[moto62]

Carbon apex seals rule. They do not give you any more power however, they allow you a little more range at higher RPM. They do not seal as well at low rpm but hey, an IT motor never see low rpm's unless you're driving around the paddock. The number one reason why I use carbon seals is, if you happen to break one, it just disappears (literally) without causing any other damage to the motor. Break a steel seal and then you'll need to replace the motor because they just tear up everyting inside. That's good enough reason for me.
Ray