RE: Chris Harris meets Porsche R&D chief
Discussion
anonymous said:
[redacted]
I thought his opinion on the steering was fairly straight forward, sadly hydraulic IS a thing of the past now. This is not a result of accounting interference, electric steering is an essential tool to allow Porsche and every other car manufacturer to meet ever more stringent emissions standards. So accepting they have to live with it, they will continue to improve it. Centre Lock is less straight forward as he's basically saying if its maintainted correctly there are no problems, but owners 'forget' to maintain them and therefore have problems. I wonder how clearly the maintenance requirement is made clear to customers at point of purchase and in the maintenance schedule? I can well imagine how this would get overlooked particularly once the cars get to 2 or three owners and fall out of the OPC servicing network.
RX7 said:
DodoRacing said:
Interesting how he categorized the old Boxster as "feminine" (which even females like his wife don't like). Not something I would expect from a top Porsche executive.
He needs to work on a better way of explaining product differentiation between the Boxster/Cayman and the 911. If you're (relatively) poor buy the Boxster and if you're rich buy the 911 is essentially what he's saying. I thought that's exactly the image they were trying to change with the new Boxster/Cayman.
Exactly how i read it, the Boxster is feminine and the Cayman is entry level so you can say you own a Porsche but just not the 911 you really wanted. Which is exactly what some have been saying for years, but obviously Porsche owners have vigorously defended such statements! He needs to work on a better way of explaining product differentiation between the Boxster/Cayman and the 911. If you're (relatively) poor buy the Boxster and if you're rich buy the 911 is essentially what he's saying. I thought that's exactly the image they were trying to change with the new Boxster/Cayman.
J-P said:
911 a first car? Really? It's very practical for a sportscar but you'd still need another first car IMHO, one that you can actually do a monthly shop in.
Isn't that what all the supermarket delivery services are for?I ran a 996TT for 2 years as my daily driver and it was great.
On the engine front, a GT3 without a race derived engine simply isn't worthy of the name. One of the best things about the Mezger mill is the sound of the internals spinning up. It's simply wonderful over 5k rpm.
993RSGT3 said:
J-P said:
911 a first car? Really? It's very practical for a sportscar but you'd still need another first car IMHO, one that you can actually do a monthly shop in.
Isn't that what all the supermarket delivery services are for?I ran a 996TT for 2 years as my daily driver and it was great.
On the engine front, a GT3 without a race derived engine simply isn't worthy of the name. One of the best things about the Mezger mill is the sound of the internals spinning up. It's simply wonderful over 5k rpm.
We wanted to do a diesel so we took it racing. Yep and that's why I have no f**king interest in LeMans these days. We're supposed to be excited by diesels... Diesels are not exciting.
The wheel nut thing is just more stubbornness from the company that excels at it (still making a bad idea work 50 years down the line). At some point you've got to accept that wheel nuts, you know the ones on every other road car, work. There's a reason no other company uses the centre locks...
The wheel nut thing is just more stubbornness from the company that excels at it (still making a bad idea work 50 years down the line). At some point you've got to accept that wheel nuts, you know the ones on every other road car, work. There's a reason no other company uses the centre locks...
Edited by juansolo on Saturday 8th December 09:28
Wolfgang Hatz said:
But anyway hydraulic steering is past - today we have to work on fuel efficiency and electric is a way to save fuel.
I can understand how having an electric system would remove the hydraulic lines, oil and pumps etc. but doesn't the electric system just replace it with a motor that requires additional energy?I'm not for one minute questioning the statement an engineer and entire company just I don't understand how electric steering saves fuel? How is a car more fuel efficient with electric steering? My mind cannot make the connection.
Agent Orange said:
How is a car more fuel efficient with electric steering? My mind cannot make the connection.
A conventional hydraulically assisted passenger car steering system uses an "open spool" architecture. This means that at all times the hydraulic fluid is flowing between the pump and the rack. Only when you actually ask for assistance does the system pressure increase to provide it. hence, all the time you are not actually making steering inputs that require assistance you are still moving hydraulic fluid around the system. This is a loss of energy that cannot be easily avoided.This is the case with an engine driven PAS system and an electrically driven one (EHPAS). EHPAS can minimise the effect by running with a speed (and hence flow) dependant system, such as in the TRW GEN2/3 units, but you still need to maintain some flow to avoid and "sag" or "lag" during rapid transient events.
EPAS, pure electric drive via an emachine direct onto the rack without using any hydraulic fluid does not have any hydraulic losses, uses no power when not assisting, and as a final positive, allows the chassis designer to tailor the systems response differently (depending on say driving mode (eco, sport etc) and between different platforms but using the same hardware (massive cost saving for volume manufacturer)
The downside is the systems refferenced inertia. To get a suitably high power density from a small Emachine, it must spin at high rpm. This means the Emachines rotor must be geared to the steering racks bar by a large reduction ratio. This means that the rotor's inertia is now coupled to the steering system via this large ratio, and as such appears as a much bigger inertia to the system. In order to appear "transparent" the motor must accelerate it's own rotor's inertia with a high enough frequency response to not "slug" the feedback loading to the steering column (and hence handwheel / driver).
The lastest systems, using low inertia rotor's and really high bandwidth motor control algorithms are managing to do this with a first order response up to ~20hz, up from ~5hz of the first systems.
Until vehicle electronics moves to a higher voltage (BMW leading the 48V revolution with the new 7) EPAS will always trail the more conventional hydraulic systems in this respect (48v = more power = the ability too cancel the systems inertia at a higher frequency)
Finally, it has to be said that drivers have simply become used to the feel of hydraulic systems. (which remember were widely slated when compared to unassissted steering racks initally!)
Great info there ^^^ I hadn't thought of the effect of gearing on inertia.
One more thing I read is that conventional PAS systems only work when the engine is turning, but even Porsche want to be able to cut the engine when e.g. descending a hill on a motorway, to save fuel ('coasting' / 'sailing'). An ePAS system can be run from the battery, so that you still have assistance with the engine off, otherwise you would have some very heavy steering all of a sudden!
One more thing I read is that conventional PAS systems only work when the engine is turning, but even Porsche want to be able to cut the engine when e.g. descending a hill on a motorway, to save fuel ('coasting' / 'sailing'). An ePAS system can be run from the battery, so that you still have assistance with the engine off, otherwise you would have some very heavy steering all of a sudden!
EHPAS also runs "engine off" if required
EHPAS: For example TRW Gen3 system
12vdc Brushless motor and controller linked to hydraulic vane pump and oil resevoir. Output flow controller by motor speed, mapped against engine rpm, vehicle speed and handwheel rate. Uses conventional hydraulic steering rack with normal spool type valve.
EPAS:
Brushed motor on steering column:
old style system, poor resonse, high coupled inertia, and low power density
Brushed, direct to rack pinion:
better, but still poor response / control
Brushless, direct to rack bar:
Highest power density, lowest inertia, simplest package and installation.
EHPAS: For example TRW Gen3 system
12vdc Brushless motor and controller linked to hydraulic vane pump and oil resevoir. Output flow controller by motor speed, mapped against engine rpm, vehicle speed and handwheel rate. Uses conventional hydraulic steering rack with normal spool type valve.
EPAS:
Brushed motor on steering column:
old style system, poor resonse, high coupled inertia, and low power density
Brushed, direct to rack pinion:
better, but still poor response / control
Brushless, direct to rack bar:
Highest power density, lowest inertia, simplest package and installation.
Some observations:
Electric Assist Steering -- Even the lowly Mustang has electric steering with good feel to it. The new GT500 Shelby on "sport" mode has perhaps too much according to some test magazines. Other manufacturers have managed electric steering with good feel. It seems very odd that Porsche couldn't do just as well with the system. At least according to journalists.
The new GT3 -- It is difficult to imagine a more disappointing GT3 for a true enthusiast (and that's what the GT3 is aimed at) than the one shaping up. At least on paper. From what we can see it has involvement-killing PDK only, involvement-killing electric steering, and doesn't even have the same engine anymore as the racing version does. Not looking very promising.
The 991 -- Why does it have the same interior as all the other Porsche cars? Why doesn't it do its own thing? Looking at the interior of the new Cayman, it seems hard to differentiate it from a 991. Or a Panameradingdong. The 911 should be a stand alone car with unique overall features which make it different from any other car. As a serial 911 owner, I've become less and less interested in the 991 the more I considerate it. In many ways, the 991 is becoming a generic Porsche.
Electric Assist Steering -- Even the lowly Mustang has electric steering with good feel to it. The new GT500 Shelby on "sport" mode has perhaps too much according to some test magazines. Other manufacturers have managed electric steering with good feel. It seems very odd that Porsche couldn't do just as well with the system. At least according to journalists.
The new GT3 -- It is difficult to imagine a more disappointing GT3 for a true enthusiast (and that's what the GT3 is aimed at) than the one shaping up. At least on paper. From what we can see it has involvement-killing PDK only, involvement-killing electric steering, and doesn't even have the same engine anymore as the racing version does. Not looking very promising.
The 991 -- Why does it have the same interior as all the other Porsche cars? Why doesn't it do its own thing? Looking at the interior of the new Cayman, it seems hard to differentiate it from a 991. Or a Panameradingdong. The 911 should be a stand alone car with unique overall features which make it different from any other car. As a serial 911 owner, I've become less and less interested in the 991 the more I considerate it. In many ways, the 991 is becoming a generic Porsche.
Trevor M said:
Some observations:
Electric Assist Steering -- Even the lowly Mustang has electric steering with good feel to it. The new GT500 Shelby on "sport" mode has perhaps too much according to some test magazines. Other manufacturers have managed electric steering with good feel. It seems very odd that Porsche couldn't do just as well with the system. At least according to journalists.
The new GT3 -- It is difficult to imagine a more disappointing GT3 for a true enthusiast (and that's what the GT3 is aimed at) than the one shaping up. At least on paper. From what we can see it has involvement-killing PDK only, involvement-killing electric steering, and doesn't even have the same engine anymore as the racing version does. Not looking very promising.
The 991 -- Why does it have the same interior as all the other Porsche cars? Why doesn't it do its own thing? Looking at the interior of the new Cayman, it seems hard to differentiate it from a 991. Or a Panameradingdong. The 911 should be a stand alone car with unique overall features which make it different from any other car. As a serial 911 owner, I've become less and less interested in the 991 the more I considerate it. In many ways, the 991 is becoming a generic Porsche.
Good points Electric Assist Steering -- Even the lowly Mustang has electric steering with good feel to it. The new GT500 Shelby on "sport" mode has perhaps too much according to some test magazines. Other manufacturers have managed electric steering with good feel. It seems very odd that Porsche couldn't do just as well with the system. At least according to journalists.
The new GT3 -- It is difficult to imagine a more disappointing GT3 for a true enthusiast (and that's what the GT3 is aimed at) than the one shaping up. At least on paper. From what we can see it has involvement-killing PDK only, involvement-killing electric steering, and doesn't even have the same engine anymore as the racing version does. Not looking very promising.
The 991 -- Why does it have the same interior as all the other Porsche cars? Why doesn't it do its own thing? Looking at the interior of the new Cayman, it seems hard to differentiate it from a 991. Or a Panameradingdong. The 911 should be a stand alone car with unique overall features which make it different from any other car. As a serial 911 owner, I've become less and less interested in the 991 the more I considerate it. In many ways, the 991 is becoming a generic Porsche.
Agent Orange said:
So in summary a traditional PAS system is drawing an amount of energy from the engine at all times where an EPAS system is on demand and therefore more efficient.
Indeed, and i could have said just that, but then i would have missed a good oportunity to sound massively inteligent........ ;-)Seriosuly, though, the one place where it really wins of course is over the emissions/FE test cycle, where the car is fixed onto a set of chassis rolls, and no steering occurs whatso ever. In effect, you drive 11km (for the STD Euro test) in a dead straight line! (No wonder the OEM's like to fit it, no matter what the percieved "cost" in terms of feel etc)
regarding the new Gt3, can i just go on record to say i expect it to be brilliant!
(no, it won't be the same to drive as the 997 GT3, which wasn't the same as the 996GT3 which wasn't the same as the........ etc etc etc. But it will be brilliant) In fact, mis-quoting horribly, Time waits for no man, as someone significantly more wordy and pompous that I once said.
So, the Metzger engine will continue to be used for the racing versions of the 991. That says it all -- the DFI 991 engine isn't good enough.
Also, the EPAS just isn't good enough either. Yes, I am comparing it to previous assisted systems in 911s -- because we are talking about 911s. The fantastic steering was one of the things that made 911s better to drive than other cars. I don't care if it's among the best of EPAS -- it should simply be best, period. It isn't.
Also, the EPAS just isn't good enough either. Yes, I am comparing it to previous assisted systems in 911s -- because we are talking about 911s. The fantastic steering was one of the things that made 911s better to drive than other cars. I don't care if it's among the best of EPAS -- it should simply be best, period. It isn't.
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