Replacement engine longevity
 

My wife tells me the power loss is back and she couldn't hold a cruise on a 30 miles drive as the car lost power. I'm concerned that we're looking at an engine replacement-- if it isn't the coils/CATs/etc..; (04 MT GT, 33K)

Has the live span of the remanufactured motors improved since they were first introduced last year? I ask since I recall there were a number of people that had their replacement motors go bad not to long after they were installed.

thanks for any help.

i have 17 k miles on a reman one. all is well...

beers :beer:

On rx7s remans are not known for their longevity. I get a LOT of 93-95 FD remans for rebuild with 20-40k on them. But then again average life expectancy of the ORIGINAL engine in the same car was only 75k.

I have seen a few remans that went to 100K in the older rx7s. Most live about 50% of the lifespan of the original engine, whatever that might be for the particular model.

Since ORIGINAL rx8 engines are lasting 25-75k on average before dealers are replacing them, I would hope that remans make it at least that far.

The best thing you guys could do, in lieu of (or in addition to) the various PCM flashes and updates, is to run additional 2 cycle premix in your gas. This will make up for mazda's lean operation of the oil metering pump and keep seals from wearing down so quickly...this is what causes drop in compression, hard starting, rough idle, stalling, etc.

A little history for you non rx7 guys. The 88 and earlier rotaries used a mechanical oil metering pump with a rod that went to the throttle linkage. They used more oil and smoked slightly more, but the engines lasted 125-200k miles (usually 125-150 for the turbo models).

Then in 89 mazda went to their first electric, computer controlled OMP in an effort to reduce oil burning and more precisely meter the oil injection for better emissions. They also improved the rotorhousing coating so as to be harder and not wear as much. No one knew it for a while, but in retrospect it's clear that the 89+ engines did not last as long as the earlier versions, despite the better coating which should have helped them last longer. Why? Mazda leaned the oil injection out somewhat.

Then again in 93 they did another such "improvement" with a harder coating on the housings and less oil injection (only 2 lines instead of 4). Yeah, those are the engines that only last 50-75k miles (granted these are the twin turbo setups that create a lot of heat).

Then here again we see the rx-8 encountering more of the same...too lean an oil injection setup and engines wearing out very fast.

If a man bought a brand new rx-8 and premixed 8oz per tank in addition to the stock OMP, did 2500 mile oil changes and yearly coolant flushes, I am willing to bet a renesis could make it to 150-200k miles easily.

The only issue with premixing like that is clogging the fuel pump pickup thus causing a lean condition. Old Dragger, Track Addict, Silver 8, and I have proved it already and it has been confirmed in lab testing (really).

I agree completely that engine longevity went to shit with the intro of electroninc omp but on the 8 premixing can be good while causing problems elsewhere which can also cut engine life. It has been my experience that the best thing you can do for the engine in the 8 is drive the piss out of it regularly. All of the track addicts cars in our group have 50000 + miles and still have strong vacuum and run perfectly. I have another customer with an automatic with over 80000 miles on it with no issues whatsoever. We maintain it, he runs the piss out of it. It kicks ass for an automatic.

A clogged fuel pump is cheaper to replace than the engine, so I premix with Cameron's Protek-R.

A third option (I am not sure about the mod on an rx-8 as I have not done it yet) is to modify the stock OMP to inject 2 cycle from a dedicated reservoir in the engine bay. I have my FC set up with this modification. OF course you are still depending on the stock OMP injection programming which is insufficient in this case. With the DBW throttle setup on the renesis, an 88 and earlier mechanical OMP retrofit is also out of the question.

SO there are 3 options:

1) run the stock OMP with stock crankcase oil which leaves deposits and does not lube well enough.

2) run the stock OMP with 2 cycle oil which leaves fewer deposits but still does not lube well enough.

3) run premix in the tank and *possibly* need to service your fuel system more often at a cost of <$100.

FWIW, rx-7 guys have been running premix for years and years and I have never heard any conclusive evidence that it actually harms anything in the fuel system. Given the relatively short age of the rx-8 (and the mods to it) I would be interested to see what "proof" you have that premix clogged your fuel system.

When running premix IN ADDITION TO the stock OMP you do not run all that much...I'd go with 8oz. per full tank. When running premix WITHOUT THE STOCK OMP injecting anything, I would double that.

I'd love to see those lab results.