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View Poll Results: What is your single most wanted F8X technical data?
Steering system HPS/EPS 8 7.48%
Power 13 12.15%
Weight 27 25.23%
Power to weight 33 30.84%
Engine type I6/V6 8 7.48%
Turbo system 10 9.35%
Other 8 7.48%
Voters: 107. You may not vote on this poll

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      09-05-2013, 02:23 PM   #45
solstice
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Porsche also say that the new GT3 has the same ZF Servoelectric HW as the non GT3 991s. SW tuning seems to be the key and likely very, very difficult taken the poor results from BMW. I've read that Porsche has rather successfully attempted to "emulate" the steering feel of the 997's HPS system in the 991 GT3.

So it sounds like it's artificially recreated HPS feel which can't be easy or cheap to achieve with such a different method of assist. I think we can be sure that taken the limited number of HW available the SW for these systems will be guarded as Fort Knox by the manufacturers that has it figured out. VW could potentially offer Porsche's know how to Audi though but since there seem to be minimal help going that way likely not.
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      09-05-2013, 03:47 PM   #46
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Quote:
Originally Posted by solstice View Post
Porsche also say that the new GT3 has the same ZF Servoelectric HW as the non GT3 991s. SW tuning seems to be the key and likely very, very difficult taken the poor results from BMW. I've read that Porsche has rather successfully attempted to "emulate" the steering feel of the 997's HPS system in the 991 GT3.

So it sounds like it's artificially recreated HPS feel which can't be easy or cheap to achieve with such a different method of assist. I think we can be sure that taken the limited number of HW available the SW for these systems will be guarded as Fort Knox by the manufacturers that has it figured out. VW could potentially offer Porsche's know how to Audi though but since there seem to be minimal help going that way likely not.
I doubt it is just SW. More likely the moments and general steering geometry that makes all the difference.

Porsche were quite late to the assisted steering scene in the first place. A front light car meant they didn't require assistance like a 50:50 or worse car did to do the 'comfort cruising' thing. Times have changed with 911's being as front light as they were, but still have less weight up front and less need to assist the crap out of a steering system.
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      09-05-2013, 05:08 PM   #47
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Well ZF don't make a different models for each manufacturer. You can get the 'Porsche' ZF Servoelectric in the F30 today. In BMW format it sucks.
Although I have not thoroughly reviewed ZF options, 1 - I doubt they list everything on their public non partner website and 2 - I doubt those systems are identical. If they are it shows how incredibly important the software is in such systems (just like in a DCT).

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Originally Posted by NISFAN View Post
As we know, steering feel is dependant on many other factors including general design of pivot points, arm lengths, castor camber, even steering wheel size, etc. BMW's are primarily designed to be comfy, so the design is less performance orientated than say a sports car brand might get away with (i.e. Porsche). P's entry level cars are on par with BMW M cars in terms of compromise and engineering.
Agree. However, I think EPS (along with software) is a larger variable in terms of feel than most of these other factors. We only have to look at how different such systems feel based on the presence of EPS or the OEMs choice of EPS system (as you pointed out).

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So can't see how because a rear engined sports car has successfully implemented a ZF steering rack, that ZF are the best.
Well regardless of front or rear engine steering feel can certainly be made to be excellent. It is again simply that ZF+ZF software+Porsche+perhaps Porsche software or software tuning has delivered arguably the best EPS available from the perspective of a sports car and HPS like steering feel.
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      09-05-2013, 05:20 PM   #48
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Quote:
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I doubt it is just SW. More likely the moments and general steering geometry that makes all the difference.
Although somewhat speculative, I disagree. Just like a DCT, software is key. There appears to be some validation of this claim here in a good article including interview comments from Porsche's General Manager Chassis Development Suspension, Steering and Hydraulic Systems, Florian Sprenger.

A description is offered of the Porsche/ZF (software) system that monitors steering angle, yaw rate and other information from CAN coming through the stability control sensors to vary the assistance and, therefore, the felt "weight" at the wheel. This is opposed to totally different designs which only monitor the torque at the steering wheel.

Like just about everything else in the world today - more software, software more important.
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      09-06-2013, 05:02 AM   #49
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Quote:
Originally Posted by swamp2 View Post
.........

Well regardless of front or rear engine steering feel can certainly be made to be excellent. It is again simply that ZF+ZF software+Porsche+perhaps Porsche software or software tuning has delivered arguably the best EPS available from the perspective of a sports car and HPS like steering feel.
Put the Porsche ZF system into a car that handles like crap, and guess what, it still handles like crap.

Joking aside, I disagree with software being the crucial factor, important to not screw it up, yes, but I'm sure ZF know what they are doing.

Steering feedback has to be due to the front suspension geometry and design. Some designs are inherently stable, some designs have a strong centreing characteristic, etc. Some give really poor feedback even with no assisted system, so how would they be tuned to give feedback with assistance? Answer is they can't (unless you think piped engine sound and piped force feedback ala computer joysticks are 'real').
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      09-06-2013, 01:41 PM   #50
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Quote:
Originally Posted by NISFAN View Post
Steering feedback has to be due to the front suspension geometry and design. Some designs are inherently stable, some designs have a strong centreing characteristic, etc. Some give really poor feedback even with no assisted system, so how would they be tuned to give feedback with assistance? Answer is they can't (unless you think piped engine sound and piped force feedback ala computer joysticks are 'real').
All (OEM) steering systems are kinematically/dynamically stable (self centering). However, what you say above is becoming less and less true. What part of

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the Porsche/ZF (software) system...monitors steering angle, yaw rate and other information from CAN coming through the stability control sensors to vary the assistance and, therefore, the felt "weight" at the wheel.
did you miss? What part of the fact that the torque or weight felt at the wheel is basically artificially induced with EPS. How is that done (apart from electric motors)? SOFTWARE. Software could absolutely make a 911 GT3 feel like an overboosted, poor feedback, 1970s Cadillac, or, well, like a HPS 911 GT3. Do you think all of these variables mentioned above are monitored for fun or not out of necessity? You realize that this is a pretty big real time data acquisition and software task yes?

Again just like DCT the fact that it basically a MT inside, that it has two transmissions running in parallel and two clutches as well - all of these contribute essential feel to the DCT. However, the software has more flexibility and more control. One only has to experience Drivelogic mode D1 vs. S6 to realize this.
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      09-06-2013, 02:15 PM   #51
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swamp, after having refreshed yourself with the EPS science are you feeling more,less or equally confident that steering will be great with EPS on the F8X? Maybe steering is not one of your priorities in a car so it's not a big deal if it's a bit numb and artificial?
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      09-06-2013, 07:56 PM   #52
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Quote:
Originally Posted by solstice View Post
swamp, after having refreshed yourself with the EPS science are you feeling more,less or equally confident that steering will be great with EPS on the F8X? Maybe steering is not one of your priorities in a car so it's not a big deal if it's a bit numb and artificial?
I don't have any particular opinions that have any strong evidence to support them (other than the fact that the software will be absolutely key). In a rough sense I think the steering feel will be better than any BMW EPS to date, but unfortunately will probably fall short of the best Porsche/ZF systems available today. Said another way, given the minor shortcomings of the current M3 steering it will probably about on par with it, perhaps improved in some areas and inferior in others. Again, all just some reasonably educated guesses here.

For me personally steering feel is indeed important as either a purchasing consideration or as a important criteria in judging a vehicles performance. I just don't want to know details about it nearly as much as power to weight.
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      09-07-2013, 02:10 AM   #53
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Ring time
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      09-07-2013, 09:38 AM   #54
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turbo and valvetronic system would do me nicely
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      09-07-2013, 10:30 PM   #55
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Swamp, I have a question (since I know you come from an engineering background). Are EPS systems (usually) programed to vary the boost so that it always requires X amount of torque to turn the steering wheel Y degrees?

If so, that would completely make sense as to why the GT3's steering is so much better than the standard 911's.


I still don't get why the loss of road feedback has happened though.
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      09-08-2013, 01:02 AM   #56
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Quote:
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Swamp, I have a question (since I know you come from an engineering background). Are EPS systems (usually) programed to vary the boost so that it always requires X amount of torque to turn the steering wheel Y degrees?

If so, that would completely make sense as to why the GT3's steering is so much better than the standard 911's.


I still don't get why the loss of road feedback has happened though.
Just to be clear I have no direct engineering experience with EPS or HPS systems although I have done engineering for disc brakes and disc brake hydraulics at a job once long ago.

The short answer to your question is covered in just a couple posts back and is a resounding no. EPS systems come in many different varieties and can use feedback from a small or large number of monitored vehicle parameters.

Also a better way to think about steering in general is not the torque required to move the wheel a certain angle but to imagine a graph of torque vs. angle throughout the lock to lock angular range. This graph will generally depend significantly on speed but with modern EPS systems such as in the Porsche things like vehicle yaw rate (i.e. is the vehicle rotating in the same plane as the road, either as part of a turn or perhaps part of over or understeering), stability control parameters and others are used to determine felt resistance at the steering wheel.

I would speculate that in comparing a base 911 to the GT3 back when both had HPS the steering feel differences were due to both hardware differences and software differences. However, in the current EPS models I suspect all of the differences in feel are covered by software alone. Again emphasizing the importance of software in such systems.
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      09-08-2013, 12:53 PM   #57
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Quote:
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Just to be clear I have no direct engineering experience with EPS or HPS systems although I have done engineering for disc brakes and disc brake hydraulics at a job once long ago.
Well compared to my engineering background which is 13 days of college, 2 FSAE meetings, and 30 pages of Tune to Win.

Anyway, thanks for answering that. It was just a thought I had.
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      09-08-2013, 10:04 PM   #58
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Weight or power:weight

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I voted weight, because power/weight doesn't say anything irl if the power is @ 8300rpm and 'no torque' whatsoever below 4000rpm....

First get rid of the overweight the E9x M3 is suffering from.


Cheers
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Yes, low weight with the same hp as current would be fine with me (assuming more torque), because that aids handling. Keeping the existing weight and just adding hp is not the same, though the power:weight might be. Unfortunately, I don't think they will get much below 3,500 lbs given the starting point and price point.
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      09-08-2013, 10:05 PM   #59
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Many are reporting that Porsche has hit a home run with very little if anything lost to HPS. Unfortunately I've yet to drive one myself, let along be able to drive one hard...



That is a stretch and not what I said. First of all no OEMs make the EPS, they are from Tier 1 suppliers. Secondly the steering on the E9X is good but has its flaws. I don't think I can personally quite give it a 9 or 10 out of 10 rating. I didn't spend enough time with my E46 M3 but I think the E46 had better steering.
Yeah, it let you feel the understeer perfectly!
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      09-25-2013, 09:00 PM   #60
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I want to know weight, even though I am sure it will be heavy.

also, all of the 4 series reviews praised the steering feel.
So the tech specs are released, ~170 lbs lighter. It is not crazy light, but it is lighter than I expected. This 3300 number is going to confuse the lot of us.

I look at it like this: compared to an e92 335i
way more power
way better handling
way more technology
similar weight
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      09-25-2013, 09:47 PM   #61
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similar weight
Despite larger size.

People tend seem to overlook that.
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      09-25-2013, 09:50 PM   #62
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Options and prices, that's it.
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      12-11-2013, 11:40 PM   #63
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Since we discussed it here quite a bit. The updates toady confirm that ZF were the chosen supplier for the M4s EPS system. No worries from me here at all.
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