drgek

This is a geeky question for ehybrid owners. I purchased a 2017 Platinum Edition Cayenne S ehybrid a month ago, and part of the fun of driving this is figuring out how to optimize battery vs fuel usage. Currently, in the cold Chicago winter, I'm getting about 11-12 miles on a full charge; with whatever combination of city/highway driving I'm doing 20% of my other miles seem to be "engine off" miles.

My specific question is the role of the echarge mode. Do you guys activate it during highway driving? Porsche claims a 20% loss in fuel efficiency, but it's hard for me to believe that happens on the highway. Currently, highway driving even in normal mode will charge the battery to about 20% of its capacity.

Undoubtedly optimizing this strategy might save me about $20 a year in gas . It's purely an intellectual exercise.

Thanks.

Marv

I once remember hearing someone complain about people not running headlights in the evening during a rain storm. He chided, saying, "Do these guys think they are saving electricity?"

Ironically, they are. Powering the headlights, although relatively small, doesn't come for free. Thermodynamics teaches us that.

You do use more gas to run the lights because the alternator must work harder to produce that power.

That only gets worse when charging a battery pack. The energy used to do that must come from somewhere and the engine supplies that energy. It's like the car is now driving continuously up hill, your mileage goes down.

20% might be right.

thescratt

This is my favourite game.. =)

E-Charge anywhere other than a highway is a pretty inefficient use of the feature IMHO.

I literally only use it towards the end of a long run if I have managed to deplete the battery and am approaching a city / town area. Because then having hybrid available, I think, just about balances out with how inefficient the car is when running purely on the ICE. What I mean by that is even 10% in the battery is significantly better than nothing, with stop start driving, as it then keeps itself topped up quite nicely with regenerative braking, and gives more fuel efficient pull aways from stop.

Round town E-Charge barely charges the battery anyway, and does burn more fuel.

I am not so sure it's as bad as 20% though. My understanding is that while it does obviously use more fuel, it's still quite frugal. The engine auto-start stop still functions, and it uses engine overrun a bit more to top the battery up.

YMMV, pun intended, based on how much you use "sailing" and regenerative braking. I have got into the habit of doing that a lot, which poses another problem.. My brake discs are quite often "dirty" as I don't use the brakes enough when doing round town runs. So I have to remember to do some harder stops to clean them up a bit from time to time.

On the few occasions I've done full days of driving, where you inevitably deplete the battery, the fuel efficiency drops down into 20mpg and lower quite quickly. I've not seen it drop much lower even with E-Charge on. So, 20%... not so sure.. But definitely inefficient anywhere other than on the highway.

Couple of things I do..

1. I use the graph screen on the PCM to experiment with things from time to time.. Watching the mpg display and so on depending on the state of my battery and the kind of journey I am doing.
2. Run E-Charge for the first part of a very cold run in the morning, where the car forces you to have the engine on anyway to warm up, and is often producing more energy than it's using for driving.

tbh I am not sure if 2 does much. These cars are very good at routing excess energy to the battery all by themselves. If anything I am probably doing this more to encourage a good warm up than anything else. I do live in Iceland. =)

drgek

I think I'm actually going to do a mileage calculation on the highway with e-charge on and with it off. I agree that it's probably not worth using driving around town.

mudman2

Was playing with this on a loaner last week. LED lights reduces power consumption by an order or 2 of magnitude so can I think be mostly ignored.

I was using e-charge around town and got up to 12 miles before I turned it off to see how it ran with the electric, the answer was pretty well

Not sure about the final MPG numbers but thought that if they do take my Diesel back this would not be a bad alternative, quite interesting.

thescratt

I personally love all the fiddling with engine modes on the hybrid. And the driving style it requires to get the best in terms of regenerative braking and so on. But I am a petrol-head / nerd. I am counting the days until the 911 hybrid happens.. And will be first in line if I can convince my wife it's ok.

I also put petrol in far less IRL than I ever did in my Turbo. I plug it in whenever the battery is below 50%, and quite often do local runs in Super Sport suspension mode, and all electric engine mode. It's like a rather large electric go-kart then. More than punchy enough for local roads.

I rarely see less than 1000km on a tank with my normal driving schedule. That is obviously very subjective, but is a combination of all electric local driving, which still feels special (almost a year in to owning it), and longer runs where I "sail" a lot and get a pretty good average mpg in hybrid mode.

When needs must I light it all up and drive it hard.. and then it sucks electricity and fuel just like any Porsche SUV.. but it also passes people and handles just like a Porsche SUV. =)

wkearney99

Personally, I hated the regenerative braking effect. I 'get' why it acts that way but it was unpleasant to have it grabbing at momentum when I expected it to be coasting up to a stop light. That and the battery weight really threw off the balance compared to a non-hybrid. It was still miles better than a non-Porsche, to be sure.

drgek

So here's a truly geeky calculation:

My gauge said for my last trip that I was using about 39.4 kwh/100 km. Assuming that is in any way accurate, the cost of 39.4 kwh from my power company is $2.99. For 62.4 miles, that is less than the cost of a gallon of premium gas.

thescratt

Were you driving this generation or the last?

If anything you have to try to regenerate.. it's very easy to just hit the brakes. Your driving style sounds like you coast up to junctions, which is well suited to this.
I miss engine braking for sure. That is really not a thing in hybrids except at highway speeds.

Downhill, any time you are off the gas it is also regenerating.
I have learned to use just enough brakes to have it at 99% of the regeneration range.. and if the ICE is running that is a very very light touch indeed.
There is slightly more resistance when driving just on battery.

When I first got the car I was convinced I'd rear end someone from looking at the gauge too much.

thescratt

Sounds about right based on my calculations here. We pay about half the cost of electricity of most countries as we are all geo-thermal in Iceland. So local travel on the battery is basically free. =)

I was driving on our sea front road with heat on full blast, in a snow storm on battery with all the lights on going at about 60kph this morning.. felt extremely surreal.

chiapet15

If I know the roundtrip distance is greater than EV range, I typically use the ICE on the highway portions only. If after the highway portion, I know there is still significant surface street driving or traffic, I will use e-charge on the highway portion to get the battery to a level that can cover the remaining distance.

Anything is better than entering a state where it idles the ICE to recharge, in which case you are getting 0 MPG.