jivemutha

All 2015 Caymans will all have have "auto start stop," meaning when you come to a red light, the engine will automatically shut off to save gas. (I'm guessing this began with the new 2014 model but don't know that.) With PDK, it's activated by keeping your foot on the brake pedal for a period of time (I don't know how long) and is deactivated the second you take your foot off the brake.

Sure--this will reduce gas consumption. But it puts a load on the starter motor and the battery. Does anyone out there (a mechanic? a backyard mechanic? an automotive engineer?) know enough about the trade-off to say whether it makes sense to allow this function to work, or will the battery life decrease, or of even greater concern, will the starter motor probably die before the car has seen the first 100,000 miles as a result of this work-out?

While I'm worried about it (I have a 2015 CS on order), I'm also thinking that none of my Prius-driving friends are complaining about starter motor failure, and Porsche engineers only rarely get it wrong, and they must have considered this problem, one would think.

FYI, there is a button allowing the driver to shut this system off, and it will automatically shut off in very cold weather or if the battery is drained. Also, I've heard (but haven't read) that when you hit the SPORT button, "automatic start stop" is deactivated as well.

Thanks in advance for your sage advice, gang.

extanker

much ado about nothing ...your battery/starter life will be fine. this is from an old mechanic that knows about hand cranking motors over to clear cylinders over before starting. batteries have greatly improved dude. are you planning on having this car past 100k miles ..................thats what i thought. my advise is ...if you ever get this car just drive it

inkatouring

After you turn off the autostop....

jivemutha

So--Extanker has been a mechanic and says not to sweat the on/off/on/off from "auto start stop." (He's right--no way will I ever get to 100K on the odometer; at 2 or 3K/year, I won't last that long.) About battery improvement, indeed I get 10 years out of a good battery these days here in mild-wintered Portland, OR (and do hope to keep the car longer than that.) Thanks for this info.

Yet Inkatouring says to shut it ("auto start stop") off. What's your reason, if it improves mileage and, according to Extanker, won't meaningfully affect battery or starter motor life? What else is there? Porsche makes it sound like the engine relights so fast that it can't really affect acceleration from a standing start.

inkatouring

Couple of reasons. First, short of living at the redline on the track -- the most stress a street-car's motor experiences is at startup.

Second, the reason car manufactures design this feature is to squeeze a few more fractions of MPGs to satisfy the fleet mandates -- something I couldn't care less about. If it really boosted MPGs, I'd be all for it, but how much gas do you really think you'll be saving with it? I doubt much. Many "features" like this are designed for the specific MPG evaluation process, so I'm skeptical that there is much real life advantage. Balance that slight MPG advantage against the wear and tear of starting and stopping, it doesn't pan out in my opinion (which I'll admit is based on guesses).

Third, I find it incredibly annoying. If I'm sitting for a long time, I'll turn the car off. Otherwise, no thanks.

btwyx

Having driven a few cars (not Porsches) with with an autostart function, I generally like it. It will suit the traffic out here, where you stop at a stop light for minutes at a time. I find it a bit annoying in creeping start/stop traffic, which is typical in London, but its easy to turn it off.

Other manufacturers have said they uprated the battery and starter to cope with the extra loads. That would be smart, but Porsche doesn't mention that.

Its turned off in sport mode, so it might never activate anyway.

jivemutha

With these disparate perspectives, besides trying to keep an open mind . . .

I think that when the car arrives (August 22nd supposedly) I'll keep tabs on MPG for a few tanks with and without "auto start stop." If the difference is trivial (as suggested by inkatouring), I'll shut it off--end of story. If it turns out to be otherwise, then before using it I'll ask my trusted Porsche mechanic. If his perspective is the same as extanker, I'll turn it on. If my mechanic has qualms (see inkatouring's comment about the stress of start-ups--a somewhat different concern than my original question about batteries and starter motor life), then better MPG or not, off it will stay.

If anybody else has experience with the issues at hand I'm still all ears, gentlemen. (I can't imagine any woman engaging in this kind of banter. While my dear wife puts up with it I secretly suspect she questions my sanity.)

Pep!RRRR

I think that a part of the problem is the auto stop/start feature does not seem consistent with the primary purposes of the car, i.e., emphasis on acceleration and handling and other sensory experience with gasoline consumption being a lower priority. Admittedly, my car is not a DD and I prefer to hear the exhaust burble when I'm stopped at a light with the windows down and the AC off. (And Sport Mode engaged).

On the other hand, I owned a Honda Insight two seater for many years and could sometimes get upwards of 70 mpg with it. This is a whole different and enjoyable kick. The Cayman (Base model in my case) can get 34 mpg when driven without heavy acceleration. It might do even better with auto/stop/start turned on.

I'll be interested to hear the outcome of your experiment.

jivemutha

I think it's designed so that Sport Mode automatically shuts off "auto start stop." Sport Mode also shuts off "coasting"--a new PDK-only feature, again to save gas, that avoids normal engine braking when the foot is off the accelerator.

May we assume to get such spectacular mileage you've got a 981 Cayman (meaning a 2014) and not an earlier model?

We've got a long wait. Again the car isn't due till August 22nd. I was very poor as a young man so for me a new Porsche was something I could only dream of. I'm having trouble sleeping, much like a 4-year-old the night before Christmas, except I've got 134 days to wait . . .

Pep!RRRR

Yes, mine is a 2014. The 34 mpg is based on the digital display and so may not be terribly accurate. I think I did get to that number once or twice on the way to the dentist (i.e. not particularly eager to get there quickly). But the bottom line is that the car is light, aerodynamic and efficient. The engine does very little work to maintain 70 mph. Of course on the track the mileage is less...(by a lot).

extanker

if you have sports type car and you are getting good mileage YOU ARE DRIVING IT WRONG. corvettes get real fun when the mpgs dip below 10 mpg.btw. if you get 10 years out of a porsche oem battery ....sell it back to porsche...they will wanna put it in their museum . drive the car then decide which nannies to turn off/on.you do know about the 300 dollar oil changes ?

Dino944

I believe 2013 Boxsters started with this feature. Its on my 2014 Cayman S. I turned it off. Most dealers turn it off when you go for a test drive.

I had a loner car from Mercedes, a 2013 C300 and I found this a painfully annoying feature. There was a very noticeable delay going from taking your foot off the brake to the engine restarting and proceeding.

Its definitely something I wouldn't waste my time with.

jivemutha

Only after the test drive did I realize that DINO944's comment was exactly what happened--the dealer DID shut the auto stop start off before the test drive began.

Regarding his other comment, if it turns out the delay in the Cayman S will be what he had to deal with the Merc, of course I won't use it. In that case I can only imagine the feature will be used for one purpose only--to get Porsche the MPG rating they're shooting for.

Re extanker's comment about batteries, agreed: OEM batteries, to my knowledge, never get 10 years of life. Where I've previously been able to achieve this trick is with a Toyota MR2 Turbo (sort of 'Cayman 987 lite from the '90s'), buying the biggest most expensive over-sized Interstate battery I could cram into the car. I did it twice, (having had the car for over 20 years). The battery dealer expected this. As I was pulling away with the first installation, he said "See ya in 10 years." Incredibly he was right. That said, in Portland OR winters don't get very cold nor is the a.c. on much in summer.

william_b_noble

I have a 2014, I bought to be a comfortable daily driver, I keep the auto stop feature on all the time. I get just over 25mpg in heavy traffic, a bit over 31 on long drives, I'd speculate I'd break 33 or 34 on a long steady no surface street drive. The auto feature is pretty smart, if AC is on, it will restart when the AC pressure drops, if seat warmers are on, it also will restart "soon", usually it will restart after a couple of minutes of sitting when it feels it's time. I test drove the car with the feature on - a dealer that turns it off and doesn't point that out to you is dishonest, find another dealer. If you buy the car for track, this doesn't matter, but if like me you buy it for comfort, not speed, you might care

worf928

There's a button on the center console to turn off auto-start/stop & coast. This button works regardless of the other buttons. Sport mode (or sport plus mode) may also turn it off. I don't know: The primary off button has been in the off position since it was delivered. I doubt it will ever be in anything other than the off position.