I'm just thinking out loud about the new efr turbos. I read in one post on this forum about the 8474 and 9280 that the reason BW doesn't offer the bigger turbine on the smaller compressors is fear of overspinning.

My thought, if I could find another interested party, would be to buy a 8474 and a 9280/9180 and swap compressor wheels and housings (using a professional turbo rebuilder to make sure things are balanced properly) to custom build an 8480 and have a left over 92/9174.

Edit: I actually saw a place where you can buy replacement compressor wheels. Maybe when they start providing replacement wheels, I can buy a housing and the 84 wheel and try it on the 9180.

I'm not sure the dangers of overspinning the wheel, but I'm assuming that's what the speed sensor is for to set provisions in the ecu.

My main question is, can the compressor wheels come off separately on these turbos or is one piece or extremely difficult to remove and reassemble properly?

 

They're advertised as non-rebuildable, never bothered to try as the supercores aren't that expensive when you get down to it.

 

Seeing there's a nut on the front, they certainly were assembled at one stage. Tooling to hold the fragile bit might be specialized beyond the run of the mill rebuilder if it's not a one shot deal and never the pair shall part short of destruction of the hotside? There's been a few 80mm turbine efrs fly apart in rotary use down here already so not sure the small compressor wheel would be a very good idea!

If you believe the distributor here, they are rebuildable....at least by BW, but didn't get into cost v a new core. I recall Turblown saying similar on a forum elsewhere too.

 

The problem with over spinning the EFRs is only for the 80mm turbine wheels. The mass of the wheel is the problem for the gammi ti, and it cannot exceed 115k rpms(again 80mm turbine wheels only)
So putting a 80mm turbine wheel on the smaller compressors would not make it more reliable, in fact the opposite. I have yet to see an EFR fail FYI. And yes you can take apart the efr turbos, you just cannot buy new components from BW for them...

 

How do you prevent overspinning? Lower boost, ignition cut? At this point I'm just curious because it sounds like the risks are far greater than the dream turbo.

 

Regarding how to prevent overspinning, I've seen speed sensor data from an EFR turbo (not a rotary engine) and the speed seemed almost directly related to boost pressure. RPM was also a factor, but not nearly as much as you might think.

 

That actually seems indicative of a low grade rotational stall.