Hi there. Just about to start rebuilding my series 5. Before I go and buy all the wrong parts just wanted some experienced advise. My tuner reckons that the ball bearing turbo is not a good choice as they can't be serviced and rotary engines produce more heat than others which will result in the turbo not lasting too long. Any help appreciated

 

welcome to the board.

i guess the first question should be what does he consider to be "not lasting too long"? also, aside from regular oil and filter changes, i'm not sure what service the turbo itself would require at intervals. perhaps i'm uninformed.

at any rate, if you look around the board you will see that many members have/had long-term projects and daily drivers that they built around ball bearing turbos. unless there is something about your planned use/situation that you haven't shared, i don't see any reason to exclude them from your choices.

not sure if any of that helped you at all.

 

Only downsides to BB turbos on rotary vs journal bearing turbos are-

Initial cost.

Cost to re-build/replace when apex seal takes out exhaust wheel.

I like how fast BB turbos recover boost between shifts.

 

The journal bearing is fine if you want to save some money and don't need a quick spool, such as for a street car that only sees occasional 'racing'. A ball bearing turbo is much better at spooling, so it has a big advantage for road racing and autocross events. There are people on this forum who have OEM turbos that are 28 years old and still running fine, so the heat shouldn't be a problem if the car's cooling system is designed properly.

The important thing is to get a water-cooled turbo so that it doesn't get fried. This is why Mazda used water-cooled turbos as standard equipment. Also, a properly-plumbed water-cooled turbo will circulate fluid even after the engine is shut down, which means that you don't need a turbo timer.