Hot side locked down??
 

I was driving the FC around tonight and doing a few pulls out on the farm to market. I was running 16psi on 110 octane, pulling hard in 4th about 6.5k rpms and heard what I relate to a 2 stroke motorcycle locking up (sound like a piece of metal snapping) and lost power. I instantly let off the gas thinking the motor was gone and held the clutch in coasting. A few seconds later I stepped on the gas to be sure and the engine was running fine. sounds fine, no smoke, revs fine in neutral. I began to think maybe I had locked up the turbo so I get home (pulls vaccume but will not boost at all and there are no air sounds at all) and pull off the intake to see if the compressor is turning. It is turning just fine. I get in and give it the gas, still no spool up. I'm thinking perhaps I may have locked down the hot side. Does this ever happen? I am unsure why it locked down if in fact it did but i'll take it off tommorow and see what the deal is.

Can the compresser turn with the hot side locked up? Is there a shaft that could break??? it sounded like a "snap". The hot side is the only used part I put back on the car. 62-1 turbonetics

Any help would be appreciated..

Yes there is a shaft that connects the compressor to the hot side turbine. No, I don't believe the compressor can turn if the turbine is locked up. Perhaps the hot side locked up, the shaft snapped and now the compressor is spinning freely.
-John

Makes sense that you would have a shear shaft in there, to prevent something even more destructive from happening...

Drop the downpipe and check the turbine.

Ok I will check on it tomorrow. If the shaft is broken is that something that can be replaced without having to replace the compressor side?

correct, the turbine/shaft are one piece, just replace that and try and figure out what made the turbine lock up in the first place....

Depends on how the shaft ends are attached at the wheels, I would think. Splined or keyed, might work without having to rip everything apart, if you're lucky.

The compressor is held into the shaft by a nut, so it's easily removed. The turbine and shaft are one unit and will need to be replaced together. You'll also need to get the whole rotating assembly professionally rebalanced, since the wheels are no longer matched.

It could definately be the shaft, especially with a hybrid turbo. Using the stock shaft with that much of a larger compressor puts more stress on the shaft, especially with you running that much boost. You may be overspinning the limits of the stock shaft. If that turns out to be the problem, Id look into having the exhaust housing machined out for a larger wheel, and use a whole 62-1 shaft and fins with a larger A/R and a thicker shaft.

Thanks for the input guys. The collective knowledge of the RX7Club members is impressive!

I'll let ya know what happened tommorow when I get it apart and post a few pics of the broken pieces.