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interesting core teardown: 04 AT 34k original miles
Customer reported difficulty starting when COLD and absolutely impossible to restart when hot, as well as stalling at idle and vibration at idle. Indeed, as soon as I sat in it at idle it had the worst vibration I've ever felt in an rx8. I removed the engine and tore it apart, and found some interesting things I've never seen before.
This is severe carbon buildup on the chrome rotor housing friction surface. Normally this does not happen because the apex seal is sweeping across the surface thousands of times per minute and keeps it pretty clean. This carbon was so hard and thick (about 0.5mm in thickness) that the seal was lifting up off of the rotor housing and letting all the compression blow out. http://www.rotaryresurrection.com/bu...e/DSCF2244.jpg http://www.rotaryresurrection.com/bu...e/DSCF2245.jpg Also I found significant wear and grooving in the compression-generating area of the rear housing above the trailing plug. http://www.rotaryresurrection.com/bu...e/DSCF2246.jpg http://www.rotaryresurrection.com/bu...e/DSCF2247.jpg http://www.rotaryresurrection.com/bu...e/DSCF2248.jpg Here is some pretty significant chrome flaking. http://www.rotaryresurrection.com/bu...e/DSCF2249.jpg http://www.rotaryresurrection.com/bu...e/DSCF2250.jpg Scraped off the carbon layer. http://www.rotaryresurrection.com/bu...e/DSCF2254.jpg http://www.rotaryresurrection.com/bu...e/DSCF2255.jpg http://www.rotaryresurrection.com/bu...e/DSCF2256.jpg Apex seals are worn everywhere except the edges...wonder why that is? :mdrmed: http://www.rotaryresurrection.com/bu...e/DSCF2258.jpg Hmmm...this doesn't look quite right? http://www.rotaryresurrection.com/bu...e/DSCF2261.jpg One of the 3 short apex springs on the rear rotor was broken. This normally does not happen. http://www.rotaryresurrection.com/bu...e/DSCF2262.jpg Here is how the springs would normally sit when properly installed. http://www.rotaryresurrection.com/bu...e/DSCF2263.jpg |
How much side seal clearance?
http://www.rotaryresurrection.com/bu...e/DSCF2264.jpg HOW MUCH?!?! 15 thousandths...spec is about 2-4, I usually try for 2 at most. In other words this engine had 7-8 times as much clearance as I usually set with when I build. http://www.rotaryresurrection.com/bu...e/DSCF2265.jpg More of the same on the front... http://www.rotaryresurrection.com/bu...e/DSCF2275.jpg http://www.rotaryresurrection.com/bu...e/DSCF2276.jpg This housing looks a lot better when cleaned up than the rear did. http://www.rotaryresurrection.com/bu...e/DSCF2278.jpg Now here it gets interesting again. As you can see here, two unbroken short springs on the front rotor are offset and not centered in the slot that they should be sitting in on the bottom of the apex seal. You can see that it's been riding this way since there is a set of shiny spots on the bottom of the seal that indicate where the tips of the spring have been riding. Thus, we can conclude that mazda installed these springs wrong when the (original, not a reman) engine was built new. http://www.rotaryresurrection.com/bu...e/DSCF2281.jpg http://www.rotaryresurrection.com/bu...e/DSCF2282.jpg Another broken short spring on the front. Total count, two broken, the other 4 installed incorrectly. http://www.rotaryresurrection.com/bu...e/DSCF2285.jpg |
Neato! Thanks, RR.
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Also I should note that the customer did the "decarb" procedure twice, as well as took it out and ran it hard for a few days, per my advice before giving up and bringing it to me. As you can see neither of these procedures helped the carbon buildup much.
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i love threads like this ... they legit make my day ... not because of the 'happy ending' or any of that sort... but because of the awesome detail in the pics. thumbs up.
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Wow .... thanks for posting this ... I spy an rx7 motor in one of the pictures (tall injector holes on the center iron is how I've been able to distinguish rx8 and rx7 motors ... also the front cover is different, and I think the gasket setup for it? )
also thanks for your contributions in general .... I wish there more threads like yours out there and I think most of the rotary (RX7 too) community would agree with this. (and your rebuild service as well) |
I was going to say that this gives some reason to drive your 8 hard regularly. But with the likelihood of the engine coming out of the factory with messed up seal clearance... Can't really say so.
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Makes you wonder how many engines came like that out of the factory...
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Good stuff RR. My original engine died at 22k, it must have been built by the same guy in Hiroshima :)
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Originally Posted by stinksause
(Post 4392258)
Wow .... thanks for posting this ... I spy an rx7 motor in one of the pictures (tall injector holes on the center iron is how I've been able to distinguish rx8 and rx7 motors ... also the front cover is different, and I think the gasket setup for it? )
also thanks for your contributions in general .... I wish there more threads like yours out there and I think most of the rotary (RX7 too) community would agree with this. (and your rebuild service as well) Pictures! |
I wonder if this 04 had the MSP16 ECU re-flash?, what was MOP condition like?, nozzles and oil lines?
Naughty Mr Mazda assember...I wonder if he still works there? BTW: Thanks for great info! :) |
RR what are your opinions on decarbing and premixing. Obviously their superfluous if the engine wasnt built to spec to begin with but would they actually be of any use in situations like this where carbon is excessive? Ive been premixing with valvoline 2 stroke since ive got my 8, decarb about twice a year although its effect is small if any. And every once in a while i premix with MMO because of its cleaning properties, effects of that arent noticeable (again minimal if any).
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Premixing helps if done consistently and properly. Decarbing is a waste of time and money.
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Love this thread
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Originally Posted by ASH8
(Post 4392319)
I wonder if this 04 had the MSP16 ECU re-flash?, what was MOP condition like?, nozzles and oil lines?
Naughty Mr Mazda assember...I wonder if he still works there? BTW: Thanks for great info! :) |
Yeah I always figured my first original engine (lasted 22k) was probably the last one built on a Friday after a 60 hour work week in Japan and my last reman (lasted 27k) was built on a Monday after a weekend in Vegas :lol:
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This thread was very cool and informative, thanks for posting such detailed pics as well as description.
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Originally Posted by RotaryResurrection
(Post 4392005)
Also I should note that the customer did the "decarb" procedure twice, as well as took it out and ran it hard for a few days, per my advice before giving up and bringing it to me. As you can see neither of these procedures helped the carbon buildup much.
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Thanks RR
Great read Love the pics |
Originally Posted by GK1707
(Post 4392377)
RR what are your opinions on decarbing and premixing. Obviously their superfluous if the engine wasnt built to spec to begin with but would they actually be of any use in situations like this where carbon is excessive? Ive been premixing with valvoline 2 stroke since ive got my 8, decarb about twice a year although its effect is small if any. And every once in a while i premix with MMO because of its cleaning properties, effects of that arent noticeable (again minimal if any).
as for premix, it helps to coat the housing so crap does not stick on as easy. most crap came from gasoline, so pick a better, newer station ... hey RR, thx for the pics! ya think the build up has something to do with the improper springs install? thats what it looks like. like u said u never seen crap like this before and this engine's springs were not installed correctly |
Originally Posted by nycgps
(Post 4392656)
when u soak hot parts into tub of hot decarb mixture, it desolves the crap on it fast, but most people thought those thing works like detergent and the longer it soaks the better. i seen big ass machines use pretty much the same kind of solution and heat to clean parts. the key point is it has to be hot hot.
as for premix, it helps to coat the housing so crap does not stick on as easy. most crap came from gasoline, so pick a better, newer station ... hey RR, thx for the pics! ya think the build up has something to do with the improper springs install? thats what it looks like. like u said u never seen crap like this before and this engine's springs were not installed correctly Lucky for me I havent had any compression related issues since I've owned my 8 (knocks on wood). Just trying to see if their are any real ways to keep carbon away from my engine or am I just wasting money on seafoam. I think RR may have proved seafoam to be ineffective. Good thing i've been filling up with 93 at the same Mobil station for over a year now. Then again I think that being an automatic really factors into this situation. More than likely this engine might not have seen high rpms throughout much of its life and RR's suggestion to drive the car hard wasnt enough to combat all the years of carbon build up off of this engine. Like you said nycgps, carbon might be able to be broken down under excessive heat which is why I continue to drive my car at high rpms every once in a while. |
off the shelf product usually sucks.
and there is no way to tell if the owner actually did the decarb correctly. not to mention, the springs weren't even installed correctly ... it's easy to build shit like that. |
just wow.
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Always a pleasure seen your work, your a big help and you helped answer questions on my build and that's why my build is running so good , your information helped a lot,
Question what kind of oil did he use and gas.? Just wondering |
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