21st century diff control for C4?
10-12-2012, 10:53 AM
#1
Three Wheelin'
Thread Starter
21st century diff control for C4?
There have been some interesting developments in the last couple of years in the Impreza, Evo and Skyline worlds with regard to electronic centre diff control.
The Skyline is my area of special interest, the R32 GTR Skyline is pretty much a direct contemporary of the 964. It uses an electronically controlled, hydraulically activated centre diff. The "brain" takes inputs from throttle steering angle and 2 axis g-sensors to use PWM to activate a solenoid to modulate the pressure on friction plates splitting torque between the front and rear wheels. It differs from the C4 in a few ways obviously, for example that the default status is 100% RWD. But there is a lot in common.
Being Japanese, from the earliest days electronics were available to either modulate the g-sensor (and other input) signals to alter the performance characteristics of the 4wd system. They were rarely seen in the wild, and outside of 1500bhp drag cars people didn't look to optimize this system, maybe because they were often required to race in RWD form or just because it was too hard.
Just as with the C4 the old analogue mechanical, swinging pendulum g-sensors, whilst better engineered than the Bosch ones we have, eventually wear out, and are cripplingly expensive to replace. Modern g-sensors are better and cheaper, but obviously not direct plug and play with our old C4s - that said they are usually linear 0-5v output so they may be closer.
Recently there has been increased interest in competitive use of the R32/33/34 GTR in time attack and other series where they are eligible to run in 4wd mode, the market has translated work that was being done on Evo's and Imprezas to the GTR.
For example, this system replaces and simulates the original g-sensors, and provides an entire replacement control unit to send signals to the solenoid which activates the centre diff. It also offers i think (as do some of the others) manual control of either the fixed torque split or the "aggressiveness" of the automated split algorithm.
http://www.full-race.com/store/r14-a...ne-gt-r-1.html
I understand this system was developed with a Canadian company (may be of interest to a certain Canadian C4 owner):
http://dccdpro.com/main/?page_id=3
This unit simply replaces and simulates the g-sensors
http://www.midoriseibi.co.jp/news/re...0120924-g.html
There is also a UK product called Skylab which is soon to release a new version along the lines of the Full-race product.
BTW These systems are all less than the price of a single new g-sensor from Porsche.
Also some folks are selling race spec center diff clutch packs (I'm sure most of our clutch packs were long ago worn out)
http://www.gtr.co.uk/forum/161207-n0...utch-pack.html
We have an added option in the shape of active rear diff control. while a few GTRs came with an active rear lsd, no one yet seems to be selling a combined centre and rear diff control system.
Despite the smaller market (C4 production figures, I don't know ~30,000? vs ~60,000 GTRs across all variants), I wonder if there is scope for some of the good folks that have worked on projects like Bosch Hammer replacements, CCU repair and rear spoiler control (in some cases resulting in salable products and services coming out of their efforts) to cast their intellects in this direction?
The Skyline is my area of special interest, the R32 GTR Skyline is pretty much a direct contemporary of the 964. It uses an electronically controlled, hydraulically activated centre diff. The "brain" takes inputs from throttle steering angle and 2 axis g-sensors to use PWM to activate a solenoid to modulate the pressure on friction plates splitting torque between the front and rear wheels. It differs from the C4 in a few ways obviously, for example that the default status is 100% RWD. But there is a lot in common.
Being Japanese, from the earliest days electronics were available to either modulate the g-sensor (and other input) signals to alter the performance characteristics of the 4wd system. They were rarely seen in the wild, and outside of 1500bhp drag cars people didn't look to optimize this system, maybe because they were often required to race in RWD form or just because it was too hard.
Just as with the C4 the old analogue mechanical, swinging pendulum g-sensors, whilst better engineered than the Bosch ones we have, eventually wear out, and are cripplingly expensive to replace. Modern g-sensors are better and cheaper, but obviously not direct plug and play with our old C4s - that said they are usually linear 0-5v output so they may be closer.
Recently there has been increased interest in competitive use of the R32/33/34 GTR in time attack and other series where they are eligible to run in 4wd mode, the market has translated work that was being done on Evo's and Imprezas to the GTR.
For example, this system replaces and simulates the original g-sensors, and provides an entire replacement control unit to send signals to the solenoid which activates the centre diff. It also offers i think (as do some of the others) manual control of either the fixed torque split or the "aggressiveness" of the automated split algorithm.
http://www.full-race.com/store/r14-a...ne-gt-r-1.html
I understand this system was developed with a Canadian company (may be of interest to a certain Canadian C4 owner):
http://dccdpro.com/main/?page_id=3
This unit simply replaces and simulates the g-sensors
http://www.midoriseibi.co.jp/news/re...0120924-g.html
There is also a UK product called Skylab which is soon to release a new version along the lines of the Full-race product.
BTW These systems are all less than the price of a single new g-sensor from Porsche.
Also some folks are selling race spec center diff clutch packs (I'm sure most of our clutch packs were long ago worn out)
http://www.gtr.co.uk/forum/161207-n0...utch-pack.html
We have an added option in the shape of active rear diff control. while a few GTRs came with an active rear lsd, no one yet seems to be selling a combined centre and rear diff control system.
Despite the smaller market (C4 production figures, I don't know ~30,000? vs ~60,000 GTRs across all variants), I wonder if there is scope for some of the good folks that have worked on projects like Bosch Hammer replacements, CCU repair and rear spoiler control (in some cases resulting in salable products and services coming out of their efforts) to cast their intellects in this direction?
10-12-2012, 11:11 AM
#2
Race Car
I'm interested to hear how this one goes - but I dont know how much difference it will make relative to a properly functioning setup in the C4. I would like to lock my car into 39/61 front to rear so that it cant change - that would make a huge difference imho...
But in terms of diff management, the problem areas are in the on/off of it more than how it functions when 'on'. When on, unless its raining or snowing - it sucks...like trying to drive a *****'s jeep around a corner...but just one that doesnt flip...lol...
But in terms of diff management, the problem areas are in the on/off of it more than how it functions when 'on'. When on, unless its raining or snowing - it sucks...like trying to drive a *****'s jeep around a corner...but just one that doesnt flip...lol...
10-12-2012, 12:06 PM
#3
Rennlist Member
regarding diff. control.
I was always fascinated by the 964 Lightweights adjustable diff. control dials. They look so cool!
"...4 wheel driv-train (torque manually adjustable to the front and rear axles and from side-to-side by driver-operated ***** on dash, unlike the Paris – Dakar 953 which was electronically regulated)." Maxted-Page.com
I was always fascinated by the 964 Lightweights adjustable diff. control dials. They look so cool!
"...4 wheel driv-train (torque manually adjustable to the front and rear axles and from side-to-side by driver-operated ***** on dash, unlike the Paris – Dakar 953 which was electronically regulated)." Maxted-Page.com
10-12-2012, 12:26 PM
#5
Three Wheelin'
Thread Starter
Those 964 lightweight controls are fully hydraulic (you can see the master cylinders), which has the benefit of simplicity but I reckon it really wouldn't be hard to wire up an Arduino or something similar to give the same functionality. Basically two analogue inputs and to PWM outputs - you'd just have to test it out to scale the PWM frequency range - very little coding required. You'd basically plug your controllers outputs into the existing solenoid in the frunk, and probably wire up some big ballast resistors to the factory harness plug to fool the PDAS ecu to prevent warning lights etc.
Even if it's not something we can do as a community effort I wonder if its something we could encourage Geoffrey, Steve or even Colin to pursue?
Even if it's not something we can do as a community effort I wonder if its something we could encourage Geoffrey, Steve or even Colin to pursue?
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10-12-2012, 01:22 PM
#8
I for one would be happy enough if someone found a way to adapt modern accelerometers to the 964. Is it difficult to convert the signal from a moder acclerometer into something that the 964 brain understands?
I would love to show the dealers my *ss when he asks me for almost 2 grand for a 20$ part...
I would love to show the dealers my *ss when he asks me for almost 2 grand for a 20$ part...
10-12-2012, 03:20 PM
#9
Nordschleife Master
While it is not very well known in Porsche circles, we are also involved in LSDs for the Evos and STis. We go pure mechanical with them and remove all electronics on the center diff. Not everyone in the industry agrees with our approach, but we've got track and stage records to back it up. Here's one example:
Like Porsche decided on the 993 and 996 models, I think if one were ever to do it, a mechanical solution on the 964 C4 would be the best way to do it.
Like Porsche decided on the 993 and 996 models, I think if one were ever to do it, a mechanical solution on the 964 C4 would be the best way to do it.
10-12-2012, 03:38 PM
#10
Three Wheelin'
Thread Starter
Super, but do you offer centre diffs for 964 C4s?
It's not like we can through a regular TBD or LSD in there, as it uses an eliptical gearset....
It's not like we can through a regular TBD or LSD in there, as it uses an eliptical gearset....
10-15-2012, 12:41 AM
#11
Nordschleife Master
Hello Alex,
I am not trying to sell you something, and no we do not make a center diff for the 964 and likely never will. There's no motorsports market for it. I offered my experience and credentials to lend credence to my opinion and nothing more. My point was I don't think that electronic solutions are superior, at least if one has a racing bias like I do. For a road going vehicle and keeping an old 964 C4 working well it might offer a solution someday. But if one is seeking maximum performance, the electronic solutions may not be the best answer to the question. That's all I am saying.
I am not trying to sell you something, and no we do not make a center diff for the 964 and likely never will. There's no motorsports market for it. I offered my experience and credentials to lend credence to my opinion and nothing more. My point was I don't think that electronic solutions are superior, at least if one has a racing bias like I do. For a road going vehicle and keeping an old 964 C4 working well it might offer a solution someday. But if one is seeking maximum performance, the electronic solutions may not be the best answer to the question. That's all I am saying.
10-15-2012, 04:40 AM
#12
Three Wheelin'
Thread Starter
My point is that I don't think a mechanical solution is within reach.
Whereas the electronics are available now that can cost effectively improve the system and offer more flexibility in the balance struck between safety and performance. The suspicion being that the designers favoured the former over the latter due to the increasingly litigious nature of their largest market.
Whereas the electronics are available now that can cost effectively improve the system and offer more flexibility in the balance struck between safety and performance. The suspicion being that the designers favoured the former over the latter due to the increasingly litigious nature of their largest market.
10-15-2012, 02:21 PM
#15
Nordschleife Master
My point is that I don't think a mechanical solution is within reach.
Whereas the electronics are available now that can cost effectively improve the system and offer more flexibility in the balance struck between safety and performance. The suspicion being that the designers favoured the former over the latter due to the increasingly litigious nature of their largest market.
Whereas the electronics are available now that can cost effectively improve the system and offer more flexibility in the balance struck between safety and performance. The suspicion being that the designers favoured the former over the latter due to the increasingly litigious nature of their largest market.
Like other projects they have done over the years, Porsche actually lost money on every 959 sold. How do they recover some of those huge R&D expenses? They apply some of the technologies they have developed to their street car production. IMO, it is for this reason alone that the 964 C4 gearbox and everything required to make it function is as complicated as it is.
Hindsight is 20-20 as they say, and over time Porche figured out that the gearbox was best left mechanical, and that the electronics were better placed out on the wheels. What this has become is things like ABD, traction control,stability management, and etc. that we see on the modern cars.
Good luck on your endeavor. Like others, I am subscribing and interested to see if you can come up with something like a DCCD Pro for the 964 C4. I think it's a great car and if someone comes up with a solution that keeps long term maintenance costs down on them, they will be doing a great service to the P-Car community.