carbon apex seals
 

hi! ive juste installed a 13B 4 port rebuilded with a bridge port a carbon apex seal, iam running with a atkins rotary intake manifold and a side draft 50mm DCO webber carburator. everything is running perfectly! i would just like to know if any of u have had any experience with carbon apex, cause i d like to know more about long term effect and durability!

from that i have heard , you don't want to over rev
them, or detonate with them or you will have a real
mess. A friend / racer did a real number on a motor
which ran a little to hot and detonated and took out
a housing and rotor.
only other thing i can think of is they don't last as long
but are easy on the housings.

matt

I used carbon seals on my bridgeport 12a, it was fine untill I used some boost on it. :D Actually carbon seals want to be rev'd. I wouldn't keep the engine running below 3500rpm much as blow by is much worse down there and causes the seals to stick. If you are constantly varying the engine speed a lot, it should last a while as from what I found. Now boost, keep out of the engine!

You do NOT want to detonate with them!

Overrev is more of a problem with *iron* seals. Remember, the whole REASON you use carbons is because carbons can handle the revs! In all other respects, carbons suck! They're one piece so they don't seal as well, the material will wear faster, the material won't handle pressure as well... but they can take the RPM.

Bear in mind that seal wear will be a function of how high and how often you rev the engine... a engine driven under road race conditions might have an engine life of 6 hours, while a street engine might last 50,000 miles, your engine will be somewhere in between, closer to which end of the spectrum is your normal life!

After blowing iron seals due to overrev after only 23k after measuring them to be "like new" I think I would rather have carbons. Then again, I don't use artificial induction so handling pressure is not one of my priorities...

NO.

If a carbon seal goes it generally does not mess up your housings... they are soft and break easily...thats why we use em. Detonation is on turbos and everyone knows you DONT use them on turbos. And yes they like revs more than steels. Think of them as between steels and ceramics.

Except ceramics like to break too, and when they go you are guaranteed that the shrapnel will destroy everything in its path (including your skin if you touch the broken bits :) ) Ceramics just don't wear so fast.

Whats the benfit of the damn Ceramic seals they sell for $200+ per seal then?!!!

Anyway, I have to agree with the broken carbon seal theory. When they break, they don't do any damage as long as you don't try to limp more then a couple miles, otherwise the apex springs may start making their way to the rotor tips and then start scoring up the housing.

After the boost I ran, the housings looked just as good as ever, however the carbon seals were certainly not! :D No boost on carbon seals! I would like to build a one-piece seal that can handle the boost and rpm of a bridgeport that I was running. The power is built up high. Maybe a half-bridgeport with boost would be a fair comprimise? I don't know, I will only do streetport with boost from now on.

well the motor i was referring to was ported farther
than any 4 port motor i have ever seen, balanced and
clearanced with hardened stationary gears, should
have been good for 10,000rpm + was making amazing
power!
That said, I have seen enough blown up motors and
to this day have never seen one with as much damage
as the one that blew with the carbon seals in it.
I don't care what anyone says, i don't think there
is such a thing as a apex seal that will not damage the
rotor housing once it is out of the rotor groove!
as to what caused the carbon seal to fail could have been a
few things but the result was the same.

As for detonation, its not just found in turbo's
if compression ratio is high enough, air fuel
charge volume is large enough and temp is high enough
you will have detonation in a non turbo!

matt

The only way I've managed to get an N/A to detonate was by switching the trailing plug wires by accident. 196degBTC timing will do it :) But lean running or hot air or both wouldn't cause detonation.

lean running leads to hot running.
heat has everything to do with detonation!
an air fuel charge that starts out hot becomes hotter
as the charge gets compressed. If combustion chamber
temps build heat from lean running the surfaces
contribute to the heating of the air fuel charge.
As well a small charge compressed say 9 to 1 will
build less heat than a large charge compressed to the
same ratio, so a ported engine will be allowing a larger
charge in for compression, the very point of porting a
motor, to make more power.
If the fuel air charge is large enough (well ported motor)
the heating during compression can result in the air fuel
charge reaching the detonation point of the fuel, this is why
there is higher octane fuels, the higher the octane the higher
its detonation point (slower burning), this is why a high octane
fuel will make less power in a low compressing engine.
the closer you can run to the detonation point of the the
fuel being used the more power you will be making, but
the closer you get the this point, the more careful you have to be with the
smallest changes in anything that will effect the volume, temp, density
of the charge.
for example a perfectly tuned motor running very close to the detonation
point at say 3000 ft altitude if all factors remain the same except for a change
in altitude of say a drop to 2000 ft altitude just the added air volume at
the lower altitude could result in detonation.

matt

Okay then.... how about a street ported engine running so lean an O2 sensor registeres 0.000 volts, full throttle for about 20 minutes at a time? (road course - after 20 minutes the tires would go off)

Had to turn the heater on full blast to keep the water temps below 220. But never detonated.

Or how about at the dragstrip where not only were the spark plugs chalk-white but the trailing plugs were eating the ground electrodes away after only 2 passes. This was before installing the O2 sensor, and obviously before installing an upgraded fuel pump to combat the problem...

Or how about limping 20 miles home with a badly clogged carburetor, engine running so lean it is misfiring and full throttle only was good enough for 35mph or so. No detonation, although I did burn all the gaskets out on the exhaust system :)

all i did was give the meaning of detonation.
if you ran really lean and hot and didnt detonate
were not at the detonation point of the fuel yet.
port it more and rev it higher under the same conditions
and you can reach detonation with a n/a.

As another example, an air fuel charge in a container which is not
compressed will detonate if it is heated to the detonation point
of the fuel without even a ignition source.

matt

I kinda doubt heat was a problem in my n/a'd bridgeport setup. I drove it hard, nothing bad happened even while experimenting with richer and leaner jet combo's. Now boost -> the compression of the raw a/f entering the engine and then being compressed some more, then the chances of detonation become realistic and the strength of the detonation wave is much more severe.

Conservative timing with correct fuel ratio and your carbon seals will be fine for a long time. One set of mine were 25,000miles+ already. Mazdatrix advertises 20,000miles max before they go out.

detonation is detonation the definition doesn't change.

matt

I've been experimenting with custom 2 piece carbon apex seals. The results have been very good so far. Both compression and power is up from the regular 1 piece design. We run them in our all-motor race car below.

Do they cost more than regular 1 piece seals?

Yeah I was below the detonation point of the fuel.... given that one generally cannot find fuel lower-grade than 86 octane in the US, which is what I use (in a pinch I'll use 87, since 86 isn't universal), could it be safe to say that running lean and running hot won't lead to detonation in a N/A? :)

Remember Mazda used to truck in 80-octane fuel to race rotaries... we should have no problems at all with 86 or 87. (And in fact, we don't)

shouldnt be a problem unless you do some
big ports which allow more air fuel charge in:)

matt

i got my gsl-se to ping on 87, it was lean enough to stop revving up top

mike

I think they are about the cheapest seals

Interesting.

1-piece carbons are, what, $30-35 apeice? How much cheaper would 2-piece carbons be?

(Although what use would they be if you were running a full/relieved bridge port?)

mike you must be mistaken there isnt a turbo on that!
(just being an ass ) :)

matt

I just decided to try some 89 octane fuel and the car started to back fire a lot. Also it could be because i didn't really measure how much oil i was putting in the tank:doh:

nope it was detonation, it did take a long time to figure out what it was, because non turbos dont detonate.

motor is still fine btw, pulls hard to 8500

mike

When mine detonated, I had no clue what the hell was happening, because it didn't sound like detonation, it was more of a loud chirping.

Must have detonated about 50-100 times before I realized what it was. Couldn't give it more than about 1/3 throttle or it would detonate, and when it did the car would buck pretty bad as well and it made no power. So I'd get sick of it and just floor it in an effort to get up past 60mph in a reasonable amount of time :)