MJones

Porsche’s new Auto Start Stop function automatically switching off the engine when coming to a standstill and with the driver pressing down the brake pedal – for example at the traffic lights or in traffic congestion.

Yikes, gotta wonder about this feature.....

Motobob

Sounds like my Prius...

Bob - Colorado

russo

This is a common feature in euro cars. I rented a 3 series in Italy just last september, a diesel of course, since 95% of their sales are in this segment. The first time it happened I thought the car stalled, but as soon as I took the foot off the brake the thing started on it's own, and sure enough each and every time afterwards.

mbslrm

Does it really make a difference?

Chaos

You have a problem with golf carts ?

Carrera GT

In the Tahoe Hybrid, the auto feature was credited with 1 mpg "or better" (?) depending upon traffic congestion, but the Tahoe has the electric motors to "crawl" in stop-n-slow (eg. being in so much traffic you don't get through on the green light) so it does a lot better crawling in traffic or idling around looking for a parking spot. A conventional engine uses a tiny fraction more fuel starting on the initial cycle on the starter motor (assuming the engine hasn't had a chance to go cold) but could have variable displacement even (disabling half the cylinders) though I've not heard anything of Porsche on this idea -- the Tahoe does this at highway speeds to dramatically reduce consumption (from 15 mpg on 8 cylinders up to 25 mpg on four cylinders) and uses the electrics for extra oomph to compensate for throttle response.

I like the auto "pause" feature so long as the brakes, steering and a/c are all electric (which hints at the Panamera having gone all electric, since they have a Hybrid version in R&D.) With synthetic oils, concerns about bearings and cylinder bores are no real issue.

As I understand the Chev/Chrysler/Mercedes technology, the system "halts" the engine with a cylinder ready to fire on a compression stroke, but it has the advantage of the electric motors being connected to the engine, not relying upon a starter motor (far less torque) to engage and crank the engine. If the system leaves the engine to stop at a random point in the cycle, it would potentially waste fuel, but it should run the last series of power strokes with no fuel injection, plus the direct injection allows for metered spray with far more precise delivery. Aside from fuel burn efficiency, the concern is how much unspent fuel escapes during the exhaust stroke to attack the cats. Retained cylinder head temperatures and high compression ratios would help with that first ignition cycle.

All that said, I have no doubt it's worth a couple of mpg around town and I find it remarkably satisfying to have the engine stopped at a red light. I don't see myself getting one of these first, expensive, "beta" Panoramas, but I could see myself in the Hybrid version -- it certainly can't come soon enough. Maybe Porsche will have a diesel offering by then too. Aagh! If Porsche offered a diesel hybrid Cayenne and Panomessa, both with the updated "nokia" dash design, which to choose?