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Discussion Starter · #1 ·
OK, so a road boulder got in front of me on Sunday as I descended "The Pigs Tail" (a.k.a. Que de Porka) on Sonora Pass Road. He pulled off at the one and one pull out (nice guy!) and I jumped on it in 2nd gear, Race mode, manual shift. The road is a 15-20% downgrade at this point. When I hit the upshift paddle I spotted 6500RPM on the tach of my Q4. I sure hope I did not damage anything. I did hear some whistling noises from the engine that I had never heard before.

I had already eased up on the throttle at the upshift, so I do not know if the engine rev limiter cut in. The hill is steep enough to drive the engine to higher RPMs.
Due to instrument lag it is possible that the engine was revved above 6500RPM.

Note that manual shift race mode does not appear to have the automatic "save the engine" upshift of the DNA modes.
 

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I doubt you hurt anything with a momentary over-rev like that. Lots of tuned engines run a higher rev limited than stock without much issue.
 

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Discussion Starter · #3 ·
I doubt you hurt anything with a momentary over-rev like that. Lots of tuned engines run a higher rev limited than stock without much issue.
Yeah, but my Norton Commando produced peak power at 7000RPM, had a redline of 7000RPM and at 7050RPM the valve train would "instantly" self destruct (valve guides gall).

Hopefully the redline is set in the Multiair 2 engine based on "no more power available" (turbo limited) rather than the mechanical/lubrication limit of some parts.
 

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On my GT3, with something like a redline of 8200 rpm, there was an easy to pull up log of over-revs, with four levels of overruns. Any over revs beyond level one made it impossible to sell the car. I didn't know there was no fuel cut off in R mode in my QV But I never drive in R anyway, and rarely in manual mode either. NV
 

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I had the EC tune with the raised rev limiter and bounced off that many times on track. I wouldn't worry at all.
 
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Discussion Starter · #7 ·
Well it most likely would, but it's expecting the QV redline...
I think you are confusing the presumed instrument panel issue with the shift lights with an ECM issue with actual shifting.
In "manumatic" mode I know for certain that it will upshift in D when you hit the redline. I do not recollect if it also does so in full manual.
 

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I think you are confusing the presumed instrument panel issue with the shift lights with an ECM issue with actual shifting.
In "manumatic" mode I know for certain that it will upshift in D when you hit the redline. I do not recollect if it also does so in full manual.
Nope, soft limiter in full manual. No auto upshifts though.
 

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It all depends on whether the I-4 engine is an interference design - ie that the valves can contact the tops of the pistons in an over-rev situation. (Miata’s don’t) I have personal experience of this with an M3 that I buzzed on the track - its called the “money shift!” Resulting damage was 5 bent exhaust valves at ~$2 grand to fix. The damage was noticeable within a 100 miles of normal driving, so if you made it home, no worries.

As for the Giulia, I always manually shift in D-mode at the track and have found the rev limiter silently prevents the car from exceeding the limit, even at WOT - no stumble or any other indication that the limiter has kicked in, so again, you should be good...
 

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Discussion Starter · #10 ·
It all depends on whether the I-4 engine is an interference design - ie that the valves can contact the tops of the pistons in an over-rev situation. (Miata’s don’t) I have personal experience of this with an M3 that I buzzed on the track - its called the “money shift!” Resulting damage was 5 bent exhaust valves at ~$2 grand to fix. The damage was noticeable within a 100 miles of normal driving, so if you made it home, no worries.

As for the Giulia, I always manually shift in D-mode at the track and have found the rev limiter silently prevents the car from exceeding the limit, even at WOT - no stumble or any other indication that the limiter has kicked in, so again, you should be good...
That would depend on if valve float is what sets the redline. In some engines excessive wear rates on rings (ring slap) and/or valve train sets the redline. Crank, conrod, piston and block are more parts that can fail from high RPM usage. My brother had a highly tuned 440 engine in his 1970 Charger and the camshaft is what failed due to high RPM usage.

In jag Etype 3.8 or 4.2 6 cylinder engines lubrication fails first from high RPM usage. The oil return from the head gallery is inadequate, such that all of the oil ends up in the head.

Of course Desmodrome engines do not exhibit valve float, but then you have a high maintenance Desmodrome to keep running.

While Mazda Protege engines are non-interference, the later model higher CR Mazda 3 engine does have an interference design. Mazda replaced the timing belt with a timing chain as a result, but also changed the camshaft gear attachment to be key-less; an arrangement that can cause loss of valve timing with a tiny loosening of the fastener (warning: hear-say from my mechanic). I do not know if Miata/MX5 engines underwent a similar modification.
 

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I had a desmo 78 Ducati 900, in the 80's. Waaaay cool street bike. 90 degree v-twin, had cams, big Malossi carbs, and Conti pipes. It ran with the new Ninga 900's at the time. Revved past the end of the stock tach. How I survived those days...

My 74 Olds Vista Cruiser with the Rocket 350 and 4brl Quadrajet would float the valves (regularly) at ?RPMs; it had no tach. At full stick, at the top, the power would drop by about half and she would release the dark ghost. Slam the next gear and all was well.

My built Nord 2000 115 GTV engine made power into the deep 7000's, until I learned about centrifugal crank oiling. That's another story.

@lockem, my guess, ya'll be ok.
 
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Discussion Starter · #12 ·
There is more to this discussion than simply if my engine was damaged. If the Multi-air 2 engine can handle more RPM maybe a little more (hybrid) turbo + a little more RPM = serious power boost?

Many large diesels are able to overrev by 10-20% when the engine is being driven by a downhill rather than by fuel. This allows some extra engine/exhaust braking capability.
IIRC, my Cummins ISB5.9 redline is 3200RPM but the max "spin" speed is 3600RPM. I believe that in this case the redline is set by max speed with effective fueling/smog rule compliance.
Also IIRC, the Cat 10.4 engine in my WhiteGMC dump truck had a redline of 2100RPM but a max spin speed of 2400RPM. That engine was the only part of the truck that worked properly...
 
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