Clever engineering makes Porsche’s hybrid genuinely efficient
Posted 07.22.2010 at 1:30 pm
8 Comments
Few vehicles flaunt their gas-chugging power as proudly as a Porsche Cayenne, so it’s natural to be suspicious of the hybrid version. Can this racecar-like SUV really improve gas mileage and still be a Porsche?
Thanks to several technological tweaks, yes. First, a more-efficient supercharged 3.0-liter V6 replaces the V8. The gas engine is paired with a 47-horsepower electric motor, and the two are linked with a decoupling clutch, so either one can run the vehicle independently. The motor is capable of handling the load alone at up to 37 mph. Together the pair flings the SUV from 0 to 60 mph in 6.1 seconds. Yet the hybrid gets an estimated 20 mpg city and 25 mpg highway, a 25 and 14 percent gain over the non-hybrid version. It also does tricks: At up to 97 mph, when you take your foot off the accelerator, the engine disengages from the drivetrain and shuts down. Here’s how this “sailing” mode lets you briefly zoom without any power at all.
Porsche Dissected: Courtesy Porsche
How to Drive Gas-Free at High Speeds
Lift Off the Gas Pedal...
when coasting at high speeds, and the gas engine powers down. A decoupling clutch disconnects the gasoline engine from the electric motor and the rest of the drivetrain, freeing the drivetrain from the drag that the powered-down engine places on it and allowing you to coast farther, fuel-free.
Coast...
powered by unhindered momentum. In this mode, which Porsche calls “sailing,” the electric motor runs in reverse, acting as a generator that harvests kinetic energy to recharge the hybrid system’s nickel-metal-hydride rear battery.
Punch It...
to speed up again. A computer coordinates the transition back to gas power. The decoupling clutch reconnects the gas engine to the drivetrain within 300 milliseconds, and the electric motor provides an additional boost for highway acceleration without a perceptible lag.
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What's old is new again. In the 50's Saab made a 3 cylinder two stroke engine which like this Porsche disengaged the engine, when you took your foot off the accelerator. No computer, just a simple mechanical freewheel. Computers in cars weren’t even in the auto designer's dreams at that time. I believe the Saab also shut down the engine after a short period of coasting. The Saab couldn't get up to 97 MPH like the Porsche. But it did get excellent mileage, better than the Porsche’s 20/25 MPG. According to the Saab Museum website it got 32.4 MPG. No electric motor needed. Oh, and it had clutchless shifting (after 1st gear.)
Also, anyone who drives a stick shift car knows about coasting. Just step on the clutch and coast up to a stop light. If you are good at it, you can even come to a stop barely needing the brakes.
eh, the saab had a freewheel, technology made popular by the bicycle.
I put my car in neutural when coasting down hills all the time with on my automatic... I can coast at least 30-40% further without the engine braking my momentum.
@Igot1forya In a recent Popular Mechanics magazine (either May or June) I read that method actually uses more gas than staying in drive. This is because in drive, when you take your foot off the pedal, gas is stopped from being pumped into the engine, whereas in neutral it continues to fire.
25 mpg is NOT efficient
In fact its really quite pathetic.
@bobbyfrother - It is when you consider how much "get up and go" it has.
I just hope while coasting you don't have to slam on the brakes.
There are cars like the Honda Civic Hybrid which have been making great use of start-stop technology. Im not sure why this is not installed on every vehicle. Think of how much gas is wasted just sitting there idling.
At a traffic light
At a drive-thru
At the school drop off
And the list goes on and one
www.gasmileageace.com