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FYI. This speaks to the 991.2 but we share the same function in our 982, similar potential for premature wear on turbo shaft/bearings related to frequency of start/stop.

PorscheBoost - Porsche 991.2 9A2 3.0 Start/Stop contributing to premature shaft/bearing wear?
I have always disabled the start/stop function and I presently have 4500 miles on the car, and I will continue doing so. I especially didn't want the oil draining from around the cylinders repeatedly during the 2K mile break-in.
 

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It's basically the first thing I disable every time I drive.


But my car is PDK and I wonder if stop-start is any benefit to the gearbox?


As we know, dual clutch gearboxes don't have torque convertors so they don't really "slip" the way a normal trans does. It's my assumption that the slight "drag" I feel when the car goes in "D" is the wet-clutch plates dragging slightly. I would imagine if this happens enough (as in a car that spent much of its life in heavy traffic) those plates would wear prematurely.


So maybe stop-start reduces this wear in heavy traffic? Hard to know.


I don't spend any great amount of time in heavy traffic so this would not apply to me.
 

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It's a function I've had on a few cars, but I find it a pretty useless one if I'm honest. Where I live we rarely ever get traffic jams & if I'm waiting at a busy junction or roundabout then the last thing I want is a momentary delay for the engine to restart. The first thing I do on any car after starting is turn it off & I feel that should really be the standard setting, with the option to engage stop/start if required.
 

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I have it engaged and it works when it needs to when I am in traffic. When I am running, it being on means nothing. I’m sure the engineers know what they are doing and if keeping it on breaks something, that is what warranty is for.

Rippey
 

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I looked at that module but didn't want to fuss with the center console given that I essentially never forget to disengage the Start/Stop feature.
Same here. I almost bought it but then didn't. My center console trim is painted and I didn't want to take the risk of chipping the edges unnecessarily.
Now I actually enjoy the "startup ritual":
Insert key, turn once, push auto start/stop, push PSE, foot on brake, disengage parking brake, start engine...rev to wake up neighbors...and takeoff! :D
 

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I have it engaged and it works when it needs to when I am in traffic. When I am running, it being on means nothing. I’m sure the engineers know what they are doing and if keeping it on breaks something, that is what warranty is for.

Rippey
To me, the concern would be that the issue wouldn't be a problem up until the warranty is already expired.

I doubt the turboshaft will fail in 50k, but what about those who put 80k miles on? 100? You shouldn't have to replace a turbo on an 80-100k car.

There's a concern here I think. I'll wait to judge until we see some turbos from cars cracked open at 50k.
 

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Discussion Starter · #11 · (Edited)
I don't mind pressing the button to turn off A/S/S every start-up as I'm used to doing that on my wife's last couple Benz SUVs, one of which is now 'the dog car' for trips with our German Shepherd, and which I drive about as often as my Porsche. So not in need of the Memory Module but understand its appeal as initially the wrong default assumption bothered me, less so now as it's become just part of a short pre-flight checklist that includes turning off the parking sensor proximity warning whilst backing out of the garage. Still, glad there is such an option as the Memory Module.

I wonder if Porsche and M-B making ON the default setting was dictated by EU fuel consumption testing protocol.....
 

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Turbos get very hot when pumping vigorously... so it's a good idea to let it cool down (if you've been running hard) before switching off, avoiding "cooking" the lube on the shaft turning it into varnish. I'm reminded of this now in this thread from years ago with three previous turbo cars. Surely would have a "bearing" on longevity :)

Doug
 

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I forgot to say this above but I was told that this start-stop button causes one other function: it allows the car to freewheel in "D" when the car is coasting.


In other words, the engine drops to idle speed as you are slowing down (saving a tiny amount of gas and perhaps reducing some trans wear....in exchange for a miniscule amount of brake wear).


This was told to me by the driving coach at PEC/Atlanta.
 

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I for one can feel the car freewheeling many a times (usually when I’m slowing down when I’m bumper to bumper traffic on 287 or 280, notorious traffic spots in NJ

Rippey
 
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I have a 2015 Macan S with pdk. Because it is 4wd, there is an option to view power allocation between front and rear on the right-hand screen (next to the tach). It shows when the car is coasting by showing no power allocation, so it gives a visual of when coasting is active. It will coast only under certain conditions (sport mode is off, the car is at temperature, cruise control is off, the car is going downhill, and it is otherwise happy (see manual)). This doesn't hurt gas mileage if the engine is warm, but it is not clear that it is worth the expense to me or has overall environmental value. I almost always use sport mode, which deactivates auto s/s. (I have had problems with auto s/s on start-up from stop signs - it sometimes gets confused between go/don't go, which has been discussed elsewhere.) My driving involves very little heavy traffic and (relatively) few traffic lights, and I got around 24 mpg over 30000+ miles, which is 1250 gals. If auto s/s gave a whopping 4% improvement in gas mileage, say to 25 mpg, gas used would be around 1200 gals. At $3/gal, that is $150 dollars saving over three years. I wonder what I paid for the auto s/s, which is bundled in the car, and what is the environmental impact of producing the auto s/s system. Obviously, if gas costs more where you live, there is a different calculation. BTW my 2018 Cayman has a manual transmission, and auto s/s does not coast, but at red lights the engine shuts down and does not start again until the clutch is pushed...I feel much better about that, but still use sport mode mostly. The Cayman has averaged about 30 mpg over 4500 miles.
 
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