Quote: Porsche said Tuesday a new prototype SUV hybrid will be capable of cruising at speeds up to 70 miles an hour on the electric engine alone, far faster than existing hybrids.The hybrid version of the popular Cayenne SUV, expected to hit showrooms in the next two or three years, can't reach 70 miles per hour without the traditional engine, but once it gets there it can cruise at 70 without the need for gasoline. http://money.cnn.com/2007/07/24/auto...ex.htm?cnn=yes

Wow that's great. I can cruise on battery mode only at 70 mph and I get a increased FE of 25%. That sounds so great that I can't wait to trade in my camry hybrid, sell my wedding ring and my wife's and then take a second mortgage on my house, just so that I could cruise on battery mode in my new 2010 cayenne. WoooHooo.

This is a $44K car with a new EPA rating of 16mpg. Porsche must be desperate or just plain stupid to consider a mere 25% efficiency in order to gain advantage against all the other $40+ suvs. Thats only 4 mpg improvement!!! And it only takes premium gasoline!!!

On top of it all, it is only a prototype. The article cited 2-3 years before release. That is plenty of time for the current hybrid forerunners to juice up their lineup. Once the LiIon battery technology issues are squared away, all the current hybrid manufacturers need to do is probably reset the onboard computers with a new firmware that shuts down the engine at an acceptable cruising speed.

I wonder for how long (time wise, miles wise), this prototype Cayenne can cruise at 70 mph on batteries alone?

Best single LD trip: 35.3mpg

That's another contention I had with this news release. Sure it can run on 70mph but how long. I believe one can answer that question using some math and comparison to current hybrid performance.

Lets first use a simple scenario for starters. The cayenne engine runs at 20 mpg on highway (presumably 70 mph). If it can run 50% of the time on engine and the other half of the time on EV only. That means for the amount of gas that he would typically run in a set distance in a conventional cayenne, it would only need half that amount for a hybrid. That is an increase from 20mpg to 40 mpg, aka a 100% increase in fuel efficiency.

But...the stated FE is only 25% improvement. Based on this, the hybrid cayenne would on average be running only 1/5 of the time on EV mode. For a 50 min cruise at 70 mph, it can be in EV mode for 10 min of that time. That is pretty good but is that realistic? First off, 10 min at 70 mph means that the cayenne can cover 11 miles on EV. That is a little hard to believe considering a camry with ~40% FE, can barely sustain 11 mile at 40 mph on the flat road. Second, the cited FE is likely a combined highway and city. FE will be lower for a long duration highway driving.

So how long do I think it can run on EV at 70 mph, 2 mins tops (and that's me being very generous and kind this morning.)

...and that's my $.02

More news on the cayenne.

http://driving.timesonline.co.uk/tol...cle2231500.ece

A 32 mpg would be remarkable indeed. That would be a whopping 100% increase in FE from the current 17mpg. It is certainly not the 25% as previously reported and would place it higher in FE than any car in its class hybrid or otherwise. Guess I will eat every byte of what I wrote if porsche manage to put this on the road anytime soon. Hmm....I wonder if a granny was test-driving it. (Sorry...no offense intended to any grannies out there reading...If you happen to drive like a race car driver instead, more power to you!)

Also in the news, porsche is working on LiIon. Now that's news. Ain't market pressure great?