spfautsch

Obviously an M6 car - interested to hear from anyone who tracks or otherwise drives their car to it's full capability while operating it with all four appendages simultaneously. If someone replies to this thread with a youtube video demonstrating anything other than the exact phenomenon I'm describing, expect more profanity.

So I'm driving my home commute on my favorite stretch of winding 2-lane highway. Not pushing it particularly hard, I approach a moderate 90 degree left sweeper - around 55 mph I stupidly aim to save some #5 syncrho wear by attempting to downshift from 6th to 4th. And yes, I know how to rev match and would have done so quite nicely had I actually found 4th. Needless to say I missed (B&M short throw shifter, far too short IMHO).

As the prop shaft spins up to speed it's sounding a lot like my router spooling up to 10k rpm, I immediately realize I accidentally hit 2nd and instantly push back to the neutral gate with the clutch pedal still at the floor. As I'm hunting for the #4 gate I noticed the "check gauges" illuminated. As I'm focusing my attention on the curve I'm boiling into I slowly begin to realize the engine is no longer running as power steering (and brakes) begin to fade, and that the check gauges light was trying to get me to look at the tachometer indicating zero. Thankfully there's a seldom traveled intersection at the outer apex and I manage to get it off and stopped.

Started back up immediately and drove the rest of the commute w/o issue. No codes were set. The only damage done was to my pride, and possibly underwear. Drove it today the same route, didn't attempt to skip shift this time.

Anyone ever witness this? I have to wonder what would cause such a thing - even if the rev limiter was triggered by the turbine air of the disengaged clutch disc over-revving the engine, it should've decelerated rapidly when the trans was dropped back to the neutral gate and once below the fuel re-enable RPM should've continued on as if resuming from a DFCO cycle.

Anyone? Bueller?

C5MSG2004Vert

Well if you were only going 55 to 60 mph down shifting from 5th to 2nd should not have caused the engine to over rev. 2nd gear on the mn6 is good to about 80 mph. The trans might whine while the gears were synchronizing and from downshifting, but that wouldn't cause the engine to shut down.

The Former

It's gremlins. I have them too. They laugh at your efforts to keep your C5 on the road.

spfautsch

Isn't that the truth.

Yesterday I had the opportunity to wind it up in 2nd gear and hold that speed for a bit, and found that at 3500 rpm it was reading 44mph. My (possibly incorrect) differential algebra puts 60 mph at 4772 rpm in 2nd. Nothing at all troubling about that. I'm still scratching my head as to what the cluck could have happened to cause the PCM to shut the engine down. The outcome could have been a lot worse on a road with no shoulders to pull off on.

Coming to a stop from 60mph with no vacuum to boost the brakes isn't what I would describe as wholesome fun.

purrvert

Just a WAG. "The PCM calculates the amount of airflow expected for a given RPM and throttle position, if these values are exceeded then C1514 will set."
When tuning my twin turbo the engine shut down numerous times. albeit associated with a loud unexplained bang, till I increased table 6101. Some tuners just max that table.

spfautsch

The thought of that throttle control protection table came to mind.

Full disclosure it could've set that code, I didn't check because it didn't turn on MIL. I've been messing with some experimental aldl software and cleared the codes after getting my script to dump the PCM flash the next day.

This has my curiosity up, I might try to reproduce on a safer stretch of road.