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I see all of these engine failures that are covered by warranty. Yet has anyone been denied a replacement engine and opened the engine up to see what seals went? If Mazda is using a vacuum leak down test to diagnose a bad engine, then I image they are looking at compression seals (apex and side seals). If that is the case, then it is the housing, the side irons, or the seals that are going bad. If they are rebuilding them and putting them back in car, it is probably not the housing or side irons. This leaves us with apex and side seals.
Does anyone know if it is these compression seals that are going away?
I have also heard seals are going away due to the use of synthetic oils. This would lead me to think there is a chemical break down of the seals (which could be water seals, oil containment seals, or compression seals). Since I have not heard of tons of smoke and leaking water I would not think it is water or oil containment seals. Back to compression.
The other issue with synthetic oil is that it really does not burn well. If the oil metering system is injecting this into the combustion chamber, this could be plugging up the cats and causing the heat. So, is it really is a heat issues, again which seal is it going bad.
Or, maybe it is this oil that is causing a carbon build up which is gumming up the compression seals.
In the end, if the housing and irons are good, they are not that hard to rebuild. Anyone having luck with this…for that matter, any more info on the break down?
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The renesis does seem to wear side seals more than other older rotary versions where the side seals did not really wear whatsoever. This is probably due to the extra heat they endure with the side exhaust ports. This leads to the thin coating of oil film being burned off of the side seals, and accelerated wear.
Much of the other issue is the lean OMP injection ratio that mazda programmed into the car, causing premature weardown of all compression seals, mainly apex seals and rotorhousings...which then leads to weak compression, slower starting, rougher idling, slight power loss, etc.
Nothing is actually breaking in these engines that are getting replaced in most cases...they are just wearing down and becoming weak.
This is part of a pattern that's gone on for a long time that most 8 owners are not aware of.
The 88 and prior rotaries had mechanical OMP's that were rod-connected to the throttle linkage...the more throttle, the more oil was injected. This system was simple and nearly bulletproof, and seemed to work well in practice. Those engines generally lasted 150-200k miles, and even the poor examples would last 100k.
IN 89, mazda went to the electronic controlled OMP in search of a way to better control emissions, and reduce the oil consumption reputation of the rotary...trying to make it more appealing to the masses and the government. I feel that they removed a bit too much OMP injection, and despite the internal coatings on the rotorhousings being made stronger at the same time, these engines generally failed 25-50k miles sooner than the previous versions.
Again in 93 they made another change, they went from 4 oil injectors/lines down to 2. Again, the coating on the rotorhousings was made even better than before, but again, these engines fail far sooner than the previous versions. Again, they seem to have leaned out the oil consumption even further. Of course...this was not the only reason for this engine's weakness...they set it up to run on the ragged edge as far as heat transfer was concerned.
Then again here we are with a new version of rotary with improved rotorhousing coating...and again we find engines getting weak prematurely due to a lean OMP injection ratio.
Then again here we are with a new version of rotary with improved rotorhousing coating… and again we find engines getting weak prematurely due to a lean OMP injection ratio.
And yet, when Car and Driver did their long-term test, the engine didn't get weaker—but stronger…
"Racers say rotary engines get faster as they age, the engine's best lap always being the last one. The RX-8 didn't disprove the theory after 40,000 miles, cutting its drag sprints down to 5.9 seconds for 60 mph and 14.6 seconds at 96 mph through the quarter."
Others have noted this, too. But it doesn't make sense, does it! I mean, if the engine's have a flawed design, then they should all grow weaker and fail. Not get stronger!
Last edited by New Yorker; 07-23-2007 at 11:09 AM.
My local dealership has change 2 engines(1 6 port and 1 4 port) out of about 150 cars.As was pointed out this is in Toronto,Ontario,slightly cooler than NY,NY.
It is hinted that the rate of failure is higher in Nevada,Arizona,Texas etc,but I have seen no real data just innuendo and general bull.
I have opened one engine and there was no problem with excessive wear on side seals,cut-off seals,apex seals,rotor housing or side housings.
It is a fact that there were no engines or ignition coils in any Mazda Parts warehouse in North America as of last Friday.Though I do not know the significance of it.
Charles R. Hill and Rotary God are in the process of rebuilding Charles' engine and they have a thread they are posting observations about it. Search it out and read through. Then post some specific questions and you can probably get some good answers from them on what they are seeing.
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Interesting. I had a post here and it got deleted.
In any event, RR pretty much covered it. The only thing I'd add is that the side seal riding over the huge crater that is the intake port seems to provide for a fairly fantastic collision on some motors.
Synth oil is not a factor. Its just a lack of lube.
Much of the other issue is the lean OMP injection ratio that mazda programmed into the car, causing premature weardown of all compression seals, mainly apex seals and rotorhousings...which then leads to weak compression, slower starting, rougher idling, slight power loss, etc.
What is OMP?
I just recently brought my car in with the same problems that you just described. the Idle was sparatic it would be really rough sometimes and the RPM's would just go up and down. Slow starting I don't really know if I've got that...it does take a little bit longer to get the car to start though. I can vouch for the power loss. sometimes the car feels like it doesn't even want to go, and it holds onto 2nd gear forever sometimes...
I dunno. Sounds like what you described is what I'm having problems with, what is OMP though so I can talk to my dealership about it =/
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The problem is, in most cases by the time the symptoms show up, the wear has already occured and running more OMP injection or premix will not really cure the situation long-term.
Premix on a weak compression engine will band aid the symptoms a little in the short term by helping restore a few psi compression. On my car premix helps the idle stabilize and helps it start about 0.5-0.75 seconds sooner than without.
It's still kinda like putting a band aid on a bullet wound, though.
Thanks Rotary Resurrection and others, this is the kind of info I was looking for. I will also search for the Rotary God info.
I had not thought about the added heat and wear caused by the new exhaust configuration.
So, on the engines that have been opened how bad is the wear? Has it been that really only the seals have needed to be changed or have the irons and housing needed to be replaced? I understand that if the rotor clips the intake it would cause damage to both, but most of the failures seem to be caught before things are rattling around inside.
I have also heard seals are going away due to the use of synthetic oils. This would lead me to think there is a chemical break down of the seals (which could be water seals, oil containment seals, or compression seals). Since I have not heard of tons of smoke and leaking water I would not think it is water or oil containment seals. Back to compression.
The other issue with synthetic oil is that it really does not burn well. If the oil metering system is injecting this into the combustion chamber, this could be plugging up the cats and causing the heat. So, is it really is a heat issues, again which seal is it going bad.
Or, maybe it is this oil that is causing a carbon build up which is gumming up the compression seals.
actually in most cases synthetics burn cleaner and have less ash (what is left after the oil is burned) than many conventional oils.
Yeah, I'd like to see that oil. Sulphuric acid, maybe?
There is a thread somewhere around here where a forum member burned down a bunch of different oils to see what was left. Apparently, Royal Purple left behind the most "junk", but it was not determined what that stuff was.
Well, I got to speak with the technical folks at Mazda Competition today and I learned that it appears the synthetic oil is NOT burning well resulting in a gummed up combustion chamber. I was told that I could run synthetic if I wanted to pre-mix and not use the factory oil injection. I still could not get a number/percentage of failures from these folks. But, I did get to see a new engine from Mazda prior to install and it came with a synthetic oil warning tag. It looks like Mazda has identified a key problem.
Hey Icemark, where did you get your info on the burning of synthetic oil, I would like to read it. Also, I could imagine some chemicals in different oil products could effect the materials in the apex seals. One area the oil could effect would be the soft seals. I could imagine there could be an effect similar to the effect using non-girling brake fluid in old British cars. I am not a chemical engineer, that was reason I was asking these questions. I was hoping to find out from people who have actually opened up these engines and looked at the problems. It was looking for real data, because it seems so many folks seem to be speculating and sharing their best guess. I just want some data.
Well, I got to speak with the technical folks at Mazda Competition ...
Welcome to the party. Did anyone offer you a drink yet?
Come in, sit down, relax. Stay a while.
I think you will like it here. Introduce yourself - everyone is glad to see you.
There, are you comfortable? Anything I can get for you? Great.
NOW STOP POSTING CRAP!
I know. That was harsh. Sorry. I didn't mean to loose my temper with you. Relax. It will all be OK.
I think I have Tourettes! I'll have to see the doctor about that next week.
HOW ABOUT USING THE DAMN SEARCH FEATURE AND LOOK AND THE SIX BILLION POSTS ABOUT SYNTHETIC AND ALL THE SPECULATION ABOUT "RESIDUE" AND "DEPOSITS" AND ALL THE OTHER UNFOUNDED CRAP!
Oh my. There I go again. I don't know what has come over me! I feel faint. It must be all the stress over this synthetic oil debate. Its giving me the vapors! I think I'll just sit down a while and...
THERE IS NO CORRELATION BETWEEN SYNTHETIC OIL AND ENGINE FAILURE< NOR IS THERE ANY DATA TO SUGGEST THAT SYNTHETIC OIL DOES ANYTHING DIFFERENTLY IN THE COMBUSTION CHAMBER THAN "NATURAL" OIL SINCE IT IS ESSENTIALLY THE SAME THING!
Wow, you are so creative…
You cut that from somewhere else and posted it here, great!
Cut 'n Paste! Now I am insulted. I worked really hard on that for 4 or 5 minutes so you can call it Cut 'n Paste?!?
The answers are all there. If you would just stop posting duplicate threads for a minute and do a search, you will be rewarded with days of reading.
Really - DAYS.
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