Haldex XWD in Pictures
If picture is worth a 1,000 words in life, a picture is probably worth 50,000 words in the blogosphere.
Nowhere is this truer than in this case.
For all of us that are Saab purists (I count myself one, for sure), these photos are a little bit of heresy. After all, who among us has ever seen a drive shaft driving the rear wheels on a production Saab built in Trollhattan? (See how I cleverly excluded the 9-7x and the 9-2x? That’s spin, folks.) I’ve not. And I really never expected to.
And along came Haldex with a brilliant system that Saab could embrace as if it is their own. And they have. According to Steve Shannon, General Manager of Saab USA, all Saab models from now on will have the option of XWD. In fact, the 9-4x, the next Saab to debut, is already done and is in testing even as we speak.
The Haldex XWD system is deceptively simple in concept: use a system of variable slip mechanisms to apply torque to the wheels that have the best grip.
In practice, this is a little harder to manage from a driver and “whole car” point of view. Changing torque distribution on the fly creates headaches from several angles. First, the drive train won’t work very well or very long unless the overall load remains somewhat predictable. Likewise, the driver cannot easily steer a car that applies torque shifts too quickly or too radically for a human to process.
Tommy Sundin, a tall, lanky Swede in the Trollhattan engineering department explained the setup and development in this way: “Anyone can build this system into a vehicle. The trick is to integrate it with the car so that it is seamless.” Integrate, indeed. The Haldex system has myriad sensors and active components that are constantly measuring and re-measuring the performance of each wheel of the TurboX and looking for ways to improve performance based upon speed, direction and available traction.
According to Mr. Sundin, the XWD system adds roughly 60kg (130 lbs.) to each car, and the additional body brackets (only six additional pieces are necessary) and the revised rear suspension add another 40kg (90 lbs.) or so.
So, here are the first shots, my friends, of the Haldex system actually installed in a production Saab.
Once again, many thanks to Herb Chambers Saab in Boston for being our gracious hosts. Without their facility, there would be no pictures to show. They are after the break…
The complete view from under the front of the Saab TurboX to the rear. Note the exhaust re-routed to make room for the rear drive shaft in the existing body tunnel.
Close-up of the Haldex rear transfer casing. Note that the Haldex controller (the small box with the Haldex logo) is integrated with the rear unit, making it much easier to design into an existing platform.
The entire setup from rear to front this time. Note the fuel tank modifications to accomodate the rear drive shaft and the rear XWD torque transfer unit. There are two distinct “nodes” on the gas tank on either side of the drive shaft rather than the flatter setup in the standard Saab 9-3.
The front XWD transfer case (and Tommy Sundin’s head). Note that the catalytic converter seems to be rotated about 45 degrees to allow for more drive shaft clearance. The torque transfer case must be coupled to the transmission, which is traverse mounted. That portion of the casing was difficult to see on this car with the road hazard sheilds in place.
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Dumb question: How does the two-node gas tank work? Does it have 2 pick-up tubes? What keeps one node from running empty before the other?
Yurk: The tank is still a single tank, and I assumed that there was a common low point for pickup. However, looking at the picture, I wonder, too, because I don’t see that common point. I can ask…
When I read the story bellow, on Saab-i, I was a little jolted to learn that Haldex has a lot more Saab in it than we might have thought. What a pity GM didn’t tap into this resource before. Today, Saab could be what Audi has become with it’s Quattro revolution. They could even have bought Haldex and keep it only for Saab and GM . But that’s the past. I’m glad the connection was made… better late than never.
Since the next 9-3 is clearly a ways down the road, it needs a new interior more than ever. Coupled with XWD it could really spring back to life alongside a new 9-5 and 9-4x. It would be a first in the history of Saab to have more than one car in the showroom that isn’t a dinosaur by today’s car life cycles.
«Three Generations of Saab History»
Peter Johansson is one of the chassis engineers responsible for the development of the new Saab XWD system. But his father, Sigge, is a former member of the competition department at Saab, who in the 1980s came up with a design for a limited-slip differential to use in rally cars. He took out a patent and eventually sold the rights to Haldex in 1987. Now, two decades later, that original design forms the basis of the electronically-controlled eLSD that his son worked with to develop Saab XWD.
In fact, the family’s connection with Saab goes back even further, right to the beginning of the car company. Peter’s maternal grandfather, Tage Flodén, is now a robust 88-year-old but in 1945 he started working for Saab Aircraft as a toolmaker and transferred to the newly-created car division in 1949 to make tooling for the first Saab 92 production car.
Over three generations, the Johansson family spans the history of Saab, from tooling up for its first production car to the launch of its latest product technology. “It’s a bit like a family business for us,” says Peter, 45, whose own seven-year-old son, Simon, is already showing a healthy interest in cars.
Sigge, now 74, was an accomplished race driver and rally competitor in the 60s and 70s, even fitting a turbocharger to a Saab 96 V4 as early as 1973. But it was his determination to improve traction and handling that prompted him to pursue his own design for a limited-slip differential.
“Saab suggested that my father should take his design to Haldex for development,” says Peter, who is also a keen racing driver who once beat a very young Ayrton Senna in a karting race in Sweden. “At that time, Haldex was not involved in the car industry but they could see the potential of this differential and decided to pursue its development.
“Dad has been for a ride in one of our test cars and was pretty impressed by what we have done with the XWD system. Obviously, we have come a long way from his time by adding four-wheel-drive and all the control electronics that were not around in his day.
“Both my father and grandfather can look back to when Saab was a much smaller company and I don’t think either of them ever imagined it would grow into the big international brand it is now. It is a story that the three of us feel part of, something that is very close our hearts.”
http://www.saab.com/main/GLOBAL/en/saab-i/2008/05/3_generations.shtml
Well that’s a silly question, they just give the gas molecules in the one side of the tank hiking boots, and when it’s time they climb over that hump!
No seriously, now you’ve got me wondering too.
With my new job, I’ve learned that Volvo also uses Haldex AWD. I’ve yet to learn when they acquired it, though.
Volvo has been with Haldex since the very first XC70. It was a pretty laim system back then.
There is a jet pump (venturi-jet) fed by the fuel pump in the pick up unit constantly pumping fuel from the “secondary” side to the other.