991 Cup uses Mezger and Hydraulic Steering
01-31-2013, 03:15 PM
#31
01-31-2013, 05:06 PM
#32
Race Director
Looks as if Nissan and Hitachi are making electro hydraulic power steering (EHPS) units right now:
http://www.nissan-global.com/EN/TECH...IEW/ehpss.html
Hyundai is also using EHPS (scroll down the features list):
https://www.hyundaiusa.com/about-hyu...-20120613.aspx
Didn’t spend a lot of time searching, but there are probably a few others still in production. It may not exist within the supplier network that GM uses. But if a car manufacturer really wanted EHPS, given that at least a dozen different manufacturers have used this system over the recent past in some pretty low cost models, it can’t be rocket science to work with a supplier to create this capability at a reasonable cost.
I can believe that an electro-mechanical system might ultimately be cheaper by a few dollars per vehicle because it eliminates a few low-cost parts, and that it would yield a very fractional increase in fuel economy. If .1L/100KM is really the gain relative to pure hydraulics (20MPG improves to 20.16 MPG if my quick math is correct), the improvement will be even less than 0.16MPG in comparison to EHPS, probably a lot less. Those improvements may have been the basis for Porsche to adopt electro mechanical steering, or maybe it was something else entirely, such as long-term reliability, controllability, packaging, etc.
http://www.nissan-global.com/EN/TECH...IEW/ehpss.html
Hyundai is also using EHPS (scroll down the features list):
https://www.hyundaiusa.com/about-hyu...-20120613.aspx
Didn’t spend a lot of time searching, but there are probably a few others still in production. It may not exist within the supplier network that GM uses. But if a car manufacturer really wanted EHPS, given that at least a dozen different manufacturers have used this system over the recent past in some pretty low cost models, it can’t be rocket science to work with a supplier to create this capability at a reasonable cost.
I can believe that an electro-mechanical system might ultimately be cheaper by a few dollars per vehicle because it eliminates a few low-cost parts, and that it would yield a very fractional increase in fuel economy. If .1L/100KM is really the gain relative to pure hydraulics (20MPG improves to 20.16 MPG if my quick math is correct), the improvement will be even less than 0.16MPG in comparison to EHPS, probably a lot less. Those improvements may have been the basis for Porsche to adopt electro mechanical steering, or maybe it was something else entirely, such as long-term reliability, controllability, packaging, etc.
Maybe Corvette couldn't find suppliers to provide parts which would allow them to build steering systems with the performance characteristics they required. Or maybe it's one or more of the other possible factors you mentioned that Porsche may have had to consider. For all we know, there might even be environmental issues around using/disposing of hydrualic fluid at an industry wide level. Regardless, I have a feeling that it's not as simple as some bean counter deciding, "Hey, let's go cheap and **** off a segment of our customer base by changing the steering in the 911".
01-31-2013, 06:39 PM
#33
Burning Brakes
Interesting. I'm slightly skeptical, though, that Nissan and Hyundai have found the holy grail of steering with their electro-hydraulic systems, while Porsche, Ferrari, BMW, Mercedes, Corvette, and others have all missed the boat completely with electro-mechanical ones. I guess I'll have to go buy a Hyundai now to experience real steering nirvana.
Maybe Corvette couldn't find suppliers to provide parts which would allow them to build steering systems with the performance characteristics they required. Or maybe it's one or more of the other possible factors you mentioned that Porsche may have had to consider. For all we know, there might even be environmental issues around using/disposing of hydrualic fluid at an industry wide level. Regardless, I have a feeling that it's not as simple as some bean counter deciding, "Hey, let's go cheap and **** off a segment of our customer base by changing the steering in the 911".
I could be wrong, but I suspect the new EM systems are better suited for this kind of control algorithm input in comparison to EHPS. If so, it’s no surprise you’ll see more widespread use of EM steering as all modern vehicles move toward higher degrees of computer control.
Last edited by fbirch; 01-31-2013 at 06:54 PM.
01-31-2013, 07:24 PM
#34
Race Director
I could be wrong, but I suspect the new EM systems are better suited for this kind of control algorithm input in comparison to EHPS. If so, it’s no surprise you’ll see more widespread use of EM steering as all modern vehicles move toward higher degrees of computer control.
01-31-2013, 07:58 PM
#35
Burning Brakes
Mike – I don’t see any reason why a well-engineered EM steering system couldn’t be developed that had great feel. I vaguely recall that Ferrari held off for quite a while putting any power steering systems on their cars until the systems had been developed extensively enough to preserve most of the great feeling of a manual rack. I haven’t driven a 991, so I can’t comment on its feel, but I’ve read lots of passionate opinions in both directions.
BTW, I don’t consider computer intervention for the sake of safety or faster lap times to be a bad thing at all – as long as it has an “OFF” button that really means OFF But this is a separate issue from steering feel.
BTW, I don’t consider computer intervention for the sake of safety or faster lap times to be a bad thing at all – as long as it has an “OFF” button that really means OFF
But this is a separate issue from steering feel.
02-01-2013, 11:45 AM
#36
Addict
Rennlist Member
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Thread Starter
Mike – I don’t see any reason why a well-engineered EM steering system couldn’t be developed that had great feel. I vaguely recall that Ferrari held off for quite a while putting any power steering systems on their cars until the systems had been developed extensively enough to preserve most of the great feeling of a manual rack.
