I had heard this was the case and it happened over the winter on my stock engine. I am sure there is a reason for this, I just can't imagine what it would be.

 

because when the fuel cut occurs it cuts the fuel to the rear rotor, so that's when the Apex seal goes Boom

 

I also heard that due to the flow of coolant through the housings, from front to back, causes the coolant to be hotter on the rear housing, thus higher temps all around (intake charge, coolant, oil). Plus I believe (personal opinion) that you have more heat soak back there too due to the tranny (also a heat source), flywheel, and the amount of metal back there is greater than the front housing. So, higher temps and fuel cut could explain this a little.

Frank

 

The rear rotor runs hotter.

I have temp leads at the base of both leading spark plugs and it always runs 15F hotter than the front. I doubt if this contributes to premature failure but it IS interesting.

 

i dont think anyone KNOWS for a fact, but i knwo there is no shortage of theories.

 

Doesn't boost go into the rear rotor, like how Boost goes into piston #3 in a normal engine?

 

when the apex seal goes out....do you need a complete engien rebuilt...or what does this cost like 300 or like 2000

 

You need a new engine, it costs about $2500 for a Mazda reman.....or if you go somewhere else you can spend as much as $5K. Plus labor if you dont do it yourself

STEPHEN

 

damn...correct me if im wrong but are the main reasons they go out is b/c: low oil, bad spark, over heating...

So change your oil/plugs get a good cooling system and you should be pretty well off...

 

no, air goes into both housings equally 4 intake ports, 2 on the intermediate and 1 on each sidehousing.

thats correct on some ways a motor can blow...they are discussing why the rear rotor usually fails instead of the front one.

 

Rarely do engines go because of low oil. There are many reasons because engines blow. Generally, it's either from someone getting too "power hungry" or improper maintenance.

If a seal goes whether apex or coolant; to replace it the engine needs to be disassembled and rebuilt, period.

 

According to Sport Compact Car "project Rx7" the rear housing doesn't have a knock sensor like the front housing does.

 

Exactly. There is no Knock sensor on the rear rotor housing therefore removing the protection device to prevent blowing the apex seals.

 

When the knock sensor senses knock, it retards timing for both front and rear rotors. That does not explain why the rear housing are usually the one to go.

Even with engines with stand alone ECUs that do not use the stock knock sensor, when they blow due to detonation, its usually the rear rotor.

Why? I am not sure.

Anthony

 

Is there any reason not to move the knock sensor to the rear rotor?

also on my PFC i run 2.5% more fuel to the rear rotor. I do this for just this reason. A bit more fuel cooling back there can't hurt.

 

Someone needs to install a wideband and egt on both exhaust ports prior to the turbo to check them individually. Course it wouldnt be me spending that $1600 haha

Also, it would really need to be a single turbo car, it would be hard to fit all that **** in on a stock manifold car.

I've also heard a theory that as the air makes that sharp turn in the elbow the O2 molecules concentrate to the right as they go thru that turn (kinda like when you make a strong right in your car and it pulls you to that side) causeing more oxygen to hit the rear rotor than front.

STEPHEN

 

My old FC also blew the rear rotor after 135,000 hard miles

 

Ya know , now I'm starting to think its a heat issue. I had a 81 Rx7 with 150k miles and it blew a seal in the rear housing after overheating several times. At the time, my stupid young *** just keep driving around the car while it had a radiator leak After about a week of this abuse, my mom tried to start the car and it locked down during start up Well thats my fault for being a young stupid ***! Anyways, if its a heat issue do you guys think its because of FlyRx7's opinion (heated flywheel,transmission,ect)? The extra heat back there could also allow the rear plate & housing to shift slighty more because of more heat expansion. Who knows, maybe it's time mazda installed extra dowel pins from he start.