ballzout

Has anyone ever had multiple motors throw out just the rear apex seals??
I have had 4 motors all spit out just the rear seals, ...and a few thousand dollars too

mostly stock, 2nd gen, with every precaution taken each time I rebuild, some last a year, some only break in.

2 motors w/steel seals, 2 motors with carbon seals ( which are cheaper to blow )

Thanks,
Rick

RotaryRocket88

iTrader: (7)

What does "mostly stock" mean? If you're constantly blowing engines, you're making some major mistake. Be it too much timing, too little fuel, etc...

BASTARD

iTrader: (4)

yes

ballzout

mostly stock means all stock except upgrades that EXTEND motor life i.e. higher persure reg, bigger injectors, Exh temp guages, 3 window bearings, no check ball and spring iin e-shaft, premixing w/inj pump still in place, and NO the timing hasn't been changed on this car for over 10 race seasons.


The mystery question is WHY ARE ONLY THE REAR SEALS BLOWING, time and time again?????

Sgtblue

iTrader: (16)

I'm not a "builder" but are there any specific conditions when they blow? Is it under load? High RPM? Or both? If so, I'm guessing your running lean for some reason at the rear rotor. Re-check injectors and anything associated with fuel delivery...intake, diffusers etc.

You are you using new springs....aren't you?

farberio

iTrader: (7)

Is your rotating assembly balanced?

Aaron Cake

iTrader: (1)

The rear rotor tends to run hotter than the front.

But you say you are racing the engine. Can we have some specifics on your setup? Because you mentioned carbon seals, I assume NA.

Have you swapped flywheels?

Where are you shifting? Spending minutes at a time at 8K?

rxtasy3

iTrader: (2)

what kind of racing is this engine seeing? how many engines have u built in this "over 10 race seasons" have u done? in all this racing and u've only lost 4 engines, i don't know if that's good or bad since i don't know how many races r in a season. but since it only the rear rotor, and only the apex seals, i'd say the apex seal grooves in that rotor r probably out of spec, especially if they barely last thru break in.

ballzout

OK, you want the dirt, and all of I spose!!

I race SCCA Improved Touring, been doing it for 15 years now, the Mazda is great for the class, so I built one, and she comes off the trailer and wins about every race it's played.
1st season, I use a over the counter MAzda factory rebuild, runs perf. but a few races go by and I take out a motor from a coolant line rupture.
Season 2, I put in another Mazda rebuild, now this is all stock, the class we run is NA with a header, and some sort of better than stock air cleaner...wooopty doo!
3 seasons go by and I plow a guy who spun and got on in front of my 90 MPH car, she lost a foot of her profile, but I redid the body and off we go again 11 months later.
So by now we're in about season 5 with this car, and has only been nocked off the podium once from suspesion failure, and a few DNF's from motors, and the one big wreck.
But I notice, after the big wreck, this thing has always had a touch of a cooling problem, even tho I bought another Mazda Comp rad. But we worked around that and ran cooler right up until 100 degree days on slow tracks, but about a season after the BIG crash, I cooked another old, old 3+ season motor, she just was wore out, and hot.
So move up another year, and a clown in Ca. builds me a "pro" motor to the tune of $7000, ( the joke was on me, cuz it was a bunch of hodge podge parts I found out later) and it only lasted about 4 races, then at Cal Speedway, I lost a rotor ( still held on to 2nd place tho ) and put it back on the trailer.
So another Mazda rebuild goes in, and we get another season ( 6-10 races) I believe. till it burst??

Now I do major home work on educating myself on DIY and walla, I build my own motor...and it runs,...great!!!

What I noticed was , both the last blown motor, and the "pro" built motor had lost only rear seals, but to me at the time , I was really OK with that cuz all I need was two good housings and rotors, so off I go to Hodge Podge land with a bunch of good "used " stuff.

Now I'm using carbon apex seals, and single spings fron RB and it runs amazing, probably 5 good hours on the thing, and before I could get it to the track... POP

So I tear it down , and realize it was the REAR APEX SEAL!!!!!!!! AGAIN !!!!!!!

Now I freak out and do everything possible to NOT cause this again...i.e.

Piggy back computer mods (to monitor and keep from lean, or advanced condition) bigger injectors , 3 window bearings, bigger oil presure reg., removed springs and ***** from e-shaft, bocked off water bypass, exh. temp sensor, wide band 02 sensor to monitor a/f ratio, oil baffle, and probably a few more things I've forgotten. like pre-mix plus oil pump, and I run Moble 1 changed every race
During assembly, I measure every tollarence meticulessly, and she's within spec and then some, and I did weigh the rotors to make darn sure they are within spec too.

BUT, I did NOT have the rotating assemblies balanced, or clearenced, and I am still using "used" parts, including oil control rings, side seals, corner seals, and rotor bearings ( NOT TO MENTION ROTORS AND HOUSINGS. )

And yes I did drop the exh, port, and open up the intakes, and I have a lighter flywheel now, so it's just a tad better than stock power wise.

BTW it is an 89 so I have the lighter rotors.
The reason I used carbon, was for price, and the fact "if" it came apart again, I could save the rotors/housings again.

So, right now, I have bought a set of ceramic seals and am ready to go after it again, BUT, before I waste a set of $ 2,000 seals, and some very expensive, and ported housings I thought I would ask the perverbial question???

WHY DO I KEEP LOOSING O N L Y THE REAR SEALS ????????

now do ya get me guys ?

Thanks for the support,
Rick

Sgtblue

iTrader: (16)

*Fuel delivery
*Out of spec parts
*Coincidence

diabolical1

iTrader: (3)

probably preignition ... as stated before the rear rotor runs hotter. you really need to put your cooling issues to bed before you can expect any semblance of maximum reliability. just to throw some ideas out there:

which coolant bypass did you block off?
what have you done about water pump cavitation?
what shape is you oil cooler in?
what size carb jets did you replace the ball and spring with?
is there proper airflow through the Mazda Comp radiator and oil cooler?
maybe look into a better radiator?
maybe increase you oil capacity?
etc....

you may also want to do the coolant mod to the rotor housings. it sounds like you run the car pretty hard, and that's racing i suppose, but every little bit helps. these engines can live through a lot, but they need to stay cool or all hell breaks loose.

on a separate note, if you've invested the money in ceramics, you should probably get your assembly balanced for the next rebuild.

Aaron Cake

iTrader: (1)

Do you have the proper counterweight installed for the S5 rotors?

Also, do you have any oil temp and coolant temp measurements?

What header are you running?

ballzout

Oil temp is around 230 on a good day can reach 260, water around 220 most often.
I wonder now if I need a new oil cooler, I have a huge splitter and it doesn't matter, on the long tracks it's ok, but the tight ones nadda.
Header is mazda comp.

I stilll think it may be computer related , Dave Lemon says apex loss is hard to do under any circumstance on a stock motor, and Jim @ RB says he'd bet it was electrical. ie ECM, or CAS , but it could be cooling is a factor??

Thanks,
Rick

ballzout

Rear counter was included when I bought flywhl from RB
I know when theyre wrong, I put the wrong one in once, that was quite bad

Aaron Cake

iTrader: (1)

220 seems pretty high under load. Factory thermostat temp is 84 degrees C, and 220F is 104 degrees C. That should peg the stock temp gauge.

Your oil temps are actually quite good for a raced engine.

What about the front counterweight?

ballzout

I've never changed the front CW, why would I???

Aaron Cake

iTrader: (1)

If you put S5 rotors into a non-S5 engine without changing the front counterweight, the assembly is unbalanced.

ballzout

could you feel it if it were unbalanced? and if so how bad? Mine was unbalanced once, when I had the wrong rear weight/flwhl combo, and it was so bad you couldn't NOT feel it.
As far as I know, all the motors I have been using have had s5 rotors/weights.
Are the counterweights numbered ( stampings/marks) to tell which one is which??

I may send this thing out for some machine work this time, lapping/surfacing, balancing, , clearancing, and perhaps water jacket machining

Aaron Cake

iTrader: (1)

You'd probably feel it above 3500 RPM.

The counterweights are numbered but it is a bit of an odd situation. They aren't all marked and apparently Mazda adjusted each counterweight slightly for each rotating assembly.