micahbones

According to the latest Evo (issue 162) the new electric power steering system in the 991 saves .1 liters of fuel per 100km, or .0264 US gallons of petrol per 62 miles. I thought a large part of the justification for these systems was improved economy, but that is barely measurable.

Porsche's website states:

Research shows that a car drives in a straight line 90 percent of the time. That inspired Porsche to develop a new electromechanical power-steering system for the new 911. In place of a conventional hydraulic steering pump, which constantly demands a portion of the engine’s power, this system employs an electric motor that uses energy only when the steering wheel is actually turned.

Again, I do not understand that reasoning. The estimated 10% in the curves is when you want positive, detailed, accurate steering feedback the most, so in designing the 991 why not err in the favor of the driver over efficiency, especially for the GT variants? Also, how much power does a hydraulic steering system really consume in a 350-400hp engine? We will know once 991s are reviewed and driven, but every electric power steering system I have driven feels artificial and "videogamey". Let's hope Porsche have worked some magic on this front.

87 944 C

i don't really know, i agree with the better feedback in those 10% of turns(tho idk where that number comes from), but the electric power steering will make it one less serviced item on the car(no PS flushes) so cheaper in theory, plus it's lighter that way(again on a 911 wouldn't mind a lil weight up front). that's all i got

Alan Smithee

Cheaper to build = more profit for Porsche.

Mike in CA

A bit of googling yielded the following points regarding electric versus hydraulic steering:

1. Hydraulic steering pumps can steal 8-10 horsepower under load
2. Small improvement in fuel economy plus elimination of weight of pump, hoses, fluid etc.
3. Eliminates leaks and need to check fluid levels
4. Quieter due to elimination of pump noise and fluid flowing through hoses and valves.
5. Electric steering can be fine tuned with a precision that is hard to match with hydraulic controls. By monitoring vehicle speed, driver inputs, suspension dynamics etc, the system can provide just the right amount of steering feel to match road conditions. It can even provide assist when the engine is off.

In today's environment, where fuel economy/weight control are paramount you can see why Porsche went this way. It may not seem like a huge savings, but taken in concert with other changes, it all adds up. Still, number 5 is the key to whether this system will be acceptable in a Porsche sports car. Keep in mind that a hydraulic system is no guarantee of good steering performance; there are really crappy, soul-less conventional steering systems out there. It's all in the execution. Porsche found a way to maintain proper steering feel when they abandoned manual steering back in the '80's and went to boosted systems and my bet is that they will do the same with electric steering on the 991.

Graygoose997

Let's not forget the inevitable electronic steering option....the self parking 991

Nizer

See Rohrl's comments on electric steering:

http://www.carmagazine.co.uk/Drives/...-Walter-Rohrl/

micahbones

Good find Nizer! Here are a couple select quotes related to the steering:

'Although the new steering may face the odd acceptance problem among purists, it is in my view superior to a conventional rack because it can support the driver in critical situations, for example, by enhancing the self-centering motion or the directional stability on split-friction surfaces.'

This sounds like more control given to the electronics and less to the driver. For me most driver aids/assists are a double-edged sword: while they may provide extra safety and margin for error that are welcome while commuting, even basic systems like ABS can serve to decrease the driver's direct interaction with the car and the road that many of us want while out at play with our vehicles.

What impressed Kacher most was the new 911's near total absence of understeer. Rohrl struggled to provoke the Carrera S into oversteer too - the engineers admit that sideways mode is no longer part of the car's character.

More neutral handling means quicker and safer, but is it as fun? We shall start to get a real sense once independent journalist drivers from mags like Evo, CAR, and Excellence get behind the wheel...

NJ-GT

the GT3 Cup and GT3 RSR already use an electric power steering pump.

The electric power steering pump can be located in the front of the 911 helping to get better weight distribution. It doesn't rob power from the engine. It is lighter by eliminating unnecessary long PS fluid lines running from the back of the car. Locating the pump in the front axle as low as possible improves cooling on this pump.

The belt driven power steering pump is obsolete in design.

If it works in the race car, is good enough for my street needs.

JLHendrix

The first transition to power steering in the 911 garnered quite a bit of criticism. IN my own '90 964, the steering was offensively soft and islotated. The transition to electric steering may take some tinkering. Even after years of this, BMW has continued to produce less than satisfactory results with electric steering in its M cars.

texas911

I thought one of the reasons was so that Porsche could turn off the engine when at a stop and not lose power steering? I guess that goes back to saving fuel?

micahbones

I could very well be wrong, and please correct me if so, but I believe the 997 GT3 Cup and 991 steering systems are quite different. Whereas a 997 Cup car uses an electric pump to motivate power steering fluid (see pic), the 991 actually uses electric motors to assist steering without hydraulic fluid at all.

NJ-GT

No idea on what the 991 is going to use yet, but if it is what you just described, PORSCHE just screwed it up again (big time). That would remove the natural feedback we get from the steering wheel.

Replacing the belt driven pump by an electric pump is good.

Replacing the fluid driven steering rack by an electric device, is very bad.

911SLOW

It seems that they didn't use the cup solution. We will confirm/know it as soon as PIWIS opens the 991 section..

911SLOW

Now we can (finally) agree..

alexb76

Basically, ALL you described is IRRELEVANT to a sports car (highly doubt 10HP loss of a steering pump)!

Specially last point.

So, this basically means, that THE CAR/SYSTEM/CPU will monitor speed/input, etc.. and then will react based on Algorithms, WHAT did the driver wanted to do! Putting an UNNCESSARY LAYER between YOU and the car/steering/wheels.

Mike, I've really come to the conclusion that in your eyes, Porsche can do NOTHING WRONG, even if they came with a 200HP car that was slower than 997, with borrowed VW Polo interior, you'd still find a reason to justify it!

The electrical steering is very well hated by every enthusiast, we can justify reasons behind it (cost, Porsche profit, Al Gore), but there's absolutely NO WAY it can be deemed *a better* steering system with better feel/precision for a sports car.