Z4 throttle body shaft snapped

[dre99gsx]

Was at a race event and this happened. Anyone else experience this ?

[grannyknot]

Too many heat cycles for the plastic gear?

[dre99gsx]

Not the gear... look at the end of the long shaft. It is supposed to be one piece with end of the other assembly pictured near it.

[Steeler]

Sheared shaft.

Butterfly got caught up on something?
Any indication of rev hang before it sheared?

[dre99gsx]

Log file shows nothing abnormal. When this happened, the engine shut off. I could not start the engine afterwards, it would just die immediately.

After inspection, the butteryfly was completely shut (nothing was found obstructing it).

Nothing that I'm aware of was ingested into the engine but now that you mentioned it, I'll do a once over into all the bores.

I'm waiting on a replace TB, so will see if engine runs fine afterwards. The current and closed loop operation is fairly "strong" - you can hurt your finger if you close the plate on it.

I suspect the plate closes so violently that it just kept banging away at it. Perhaps I need to re-tune the PID on this, but it's been 7+ years racing with no issue.

The section where it sheared is much thinner then the rest of the shaft. It actually gets located via a small pin that keeps the entire shaft in place. That pin to the shaft groove is definitely high friction, and it's possible with heat it just fatigued.

Attached image: you can see the pin near the bottom. I also noticed the area where the pin was contacting the shaft was slightly wearing away at it, but the wear was directly on the bronze section that sheared.

I betting I'm the first to ever snap this thing, but I don't know anyone using an N52 TB for racing duty.

[Steeler]

Does the butterfly actually slam closed?
It does need to remain open a few degrees, otherwise off throttle would stall the engine every time.

Surprised there is not a spring damper.

[dre99gsx]

It's possible it slams closed, but the PID corrects it to about 5% open angle immediately - engine never stalls on off-throttle.

I believe there is 6amps of current going into this motor. I do know that it's impossible to manually open the butterfly by hand when it's energized - so it does create a good amount of force.