Auto Service World
Feature   January 1, 2015   by Steve Pawlett

Driveline Innovations Pushing Growth


With OEMs continuing to push innovations in driveline technology to improve ride, handling, safety, and fuel efficiency, jobbers can expect this burgeoning market to continue to expand on many fronts.
According to a recently published study by Frost & Sullivan on driveline systems in North America and Europe, OEMs are focusing on the use of on-demand disconnect driveline systems and right-sizing of drivelines for the SUV and CUV markets, to improve performance and fuel efficiency to meet consumer demand for vehicles in these markets.
“In terms of driveline efficiency, this is something the industry has been talking about for a long, long time,” explains Frost & Sullivan automotive and transportation research analyst Vikram Chandrasekar. “The trend we are seeing is the OEMs moving towards implementing this in more front-wheel drive vehicles, because you don’t have to send power to the rear wheels, which would involve more parasitic losses.”
By 2020, the penetration rate of AWD systems in North America is estimated to reach over 80% in the sport utility vehicle segment, thereby driving the adoption of driveline disconnect solutions. According to the Frost & Sullivan report, front-wheel drive-based, all-wheel-drive disconnect systems; true torque vectoring systems; electronic limited slip differential systems; and power transfer units will remain the most important parameters defining OEMs’ driveline system strategies. Currently, OEMs are focusing on automatic switching systems, as consumers prefer them to manual systems. These systems were first introduced to the market over 20 years ago, and are now coming back. This bodes well for jobbers, as more driveline components are developed and brought to market by OEMs looking to improve performance, reliability, and fuel economy.
“For front-wheel-drive vehicles, cost is a major concern because the OEMs have to add disconnects at two locations so the axle won’t spin. For transverse engines and the compact SUV market, those consumers do not want to switch manually, so it’s about how they can get an automated process into it. And this is an extremely difficult challenge, according to the OEMs,” explains Chandrasekar. “Another reason for an automated system is if the driver gets caught in the wrong mode and gets a wheel slip, it’s a huge risk.”
According to the report, TTV (True Torque Vectoring) is only being considered by a few OEMs because of the cost constraints, and there is only a marginal increase in performance when compared to electronic slip differential. “TTV will remain a niche technology for high-end vehicles. OEMs will likely focus more on pseudo-torque vectoring (fixed ratio split) as it is less expensive than the true torque vectoring system,” adds Chandrasekar.
“There are two types of torque vectoring systems. One is a variable ratio system (from 1 to 1.5, for example), which is a way it can be used on all-wheel drive and front-wheel drive. The second type is a fixed-ratio split. The two torque vectoring systems would have split ratios or variable ratios. The variable system is much more expensive and will likely only be seen on high-end vehicles. There are other systems in the market, called torque vectoring, that are really brake torque vectoring systems. They utilize the braking system to vector the torque, so these are really pseudo-torque vectoring systems,” explains Chandrasekar.
“Torque vectoring systems are something that you add at the coupling mechanism to the axles. Each of the axles gets power based on the conditions of the road and what angle you hit the road. Torque vectoring is like rowing. If you row only on one side of the boat, it will veer to one side. With torque vectoring, it regulates torque to each wheel depending on several conditions to help stabilize the vehicle.
“BMW has true torque vectoring, which is a hydraulically controlled system and has hydraulically actuated clutches to each of the rear wheels. This system is targeted for models like the M version of the X6 and X5. Audi will have a very similar system that will be targeted at the Q5, S5, S4, and A5.
“Honda has a totally different approach. It has more from the controllable ratio system of the true torque vectoring system with a fixed ratio mix-match system. The trade-off is less torque vectoring, but at a lowered cost. The Honda Acura has it, and the MDX RDX and the LX and SX have it,” adds Chandrasekar.
“Certain OEMs are also looking to replace AWD vehicles with an eLSD system only. The pickup segment will likely introduce eLSD, and OEMs such as Toyota and Ford are looking to introduce this in the near future.
“The eLSD should also see more demand from the performance hatchback segment since its introduction in the VW Golf,” adds Chandrasekar.
Similar to torque vectoring, brake eLSD systems come at no additional cost. However, the problem with the brake eLSD system that it’s very limited, and there are issues like extra brake wear and traction control issues as well as temperature increase issues with this system.
“This system is focused more on the performance audience. There are even claims from within the industry that the eLSD system can help as much as an all-wheel drive system on a small car, but that isn’t expected to happen for some time, according to industry sources,” says Chandrasekar.
“In terms of eLSD systems, we have the high performance rear-wheel drive, the front-wheel drive, the utilitarian SUV market, and the truck market, and according to my research, these markets will catch up. There is a lot of growth potential in these markets. It’s the cost of the software that is making it really hard to make the technology work on such lower-priced cars, but the market has, from my analysis, great potential as software requirements and safety requirements mature and you gain economies of scale for these eLSD systems. I think we will see them come to the SUV market,” says Chandrasekar.
Premium OEMs such as Mercedes-Benz and BMW will likely introduce FWD-based AWD vehicles with single stage PTUs in the C-segment. Most OEMs are moving to single-stage power transfer units to gain efficiencies, but packaging constraints are a major concern in the left-hand shift PTUs.
“There are single-stage PTUs, dual-stage PTUs, or a three-stage PTU. As of now, we see that OEMs are moving towards single-stage PTUs. Ford, for instance, has a three-stage PTU, and it has an efficiency of 90%, which is very bad in terms of driveline efficiency today, so Ford is moving towards a single-stage PTU. You can expect to see legacy models like the Ford Flex having the single-stage PTU,” says Chandrasekar.
While Ford is moving towards a single-stage PTU, GM is still using a two-stage PTU while it contemplates whether to move to a single-stage PTU to gain more efficiency. “When you go to a single-stage PTU from a dual-stage PTU, you save approximately $100 per PTU and you improve efficiency. GM is one OEM that is still sticking to the two-stage unit, but I believe going forward, they will eventually move to a single-stage PTU. But that’s yet to be seen,” adds Chandrasekar.
“In terms of PTUs, there are the left-hand shift and the right-hand shift. The left-hand shift is the closest to the transmission, and it’s the most difficult to package because it’s on the transmission side. There are a lot of moving parts in the front engine bay, so apart from the engine you have the power going to the transmission and the transmission sending power to the PTU, and the PTU will split the power between the wheels. So when this happens, the PTU has a lot of work to do – and having a left-hand shift is a real packaging problem,” explains Chandrasekar.
A right-hand-shift PTU is much easier to package, but the right-hand shift costs more. Because of these
cost reasons, OEMs try to put in the left-hand shift where they can, but right-hand shifts are there as well. “The evolution has occurred and there are different ways in which the PTU is activated. You have the synchroniser in the driveline of the Land Rover models, for instance, and then you have the dog clutch, which is less expensive but much more difficult to control, so both of these are being considered now based on cost. It really depends on what OEMs are looking at and what they are likely to have in terms of cost,” he adds.
“From my analysis, I don’t see too many OEMs going in for the disconnect systems, mainly due to the cost factors. Most OEMs will likely focus mainly on systems where they can use the existing hardware and not spend a lot of money on new hardware, so the focus will likely be more on driveline right-sizing,” surmises Chandrasekar.
Driveline right-sizing allows OEMs to reduce the mass of the driveline, particularly in the coupling technology, which will help reduce driveline masses and reduce parasitic losses.
“When you downsize, in terms of coupling technology, it should have a high level of torque agility and load capacity and there are a number of coupling technologies available. You have hydraulic-based coupling, electro-magnetic coupling, and electronic coupling,” explains Chandrasekar. “There are different coupling mechanisms and there are different suppliers working on various systems. For example, BorgWarner is participating in both all-wheel drive disconnect systems as well as driveline right-sizing. GKN is another major North American supplier that is participating in driveline right-sizing to reduce parasitic losses,” says Chandrasekar.
“Realistically, there is a crucial difference between what consumers really want and what vehicle development engineers really want. For example, you have the non-Japanese OEMs that generally tend to oversize the driveline because they would like to have as much power as the coupling mechanism could take, while OEMs like Honda and Toyota design their systems differently. For example, Toyota launched the RAV 4 knowing their target audience isn’t going to take it on a road that is half-ice and half-rock at open throttle, so they size the driveline for that particular market. These designs help to reduce parasitic losses and bring down the driveline sizing based on what the market wants and how it is positioned in the market,” explains Chandrasekar.
“So it will be more of a cost reduction, and this is what most OEMs will be focusing on, but there are inherent limitations to downsizing and still achieving the same performance. You can categorize the market based on the target audience. A RAV 4, for instance is an urban SUV, so you don’t need a powerful four-wheel drive system, but if you take a Ford F150 or 250, which requires much higher performance in terms of all-wheel, drive capability, the requirements are much different. Again it depends on your audience,” adds Chandrasekar.
Electric all-wheel drive systems
Even though electric all-wheel drive systems can have a significant impact on parasitic losses, the Frost & Sullivan report predicts they will be limited to use primarily on hybrid models.
“Basically, in a traditional all-wheel drive system, power from the engine is being delivered to the front wheels and/or the rear wheels, and when the system takes a wheel slip the power is transferred to the follower axle – the front or the rear axle. This is done by putting the power through a couple of shafts to a coupling mechanism and to a transfer case, which means a lot of unnecessary losses trying to spin a lot of parts in the driveline system,” explains Chandrasekar.
“These parasitic losses can be overcome by the E-all-wheel-drive system, by fitting an electric motor on the front axle or the rear axle. For example, on the Audi Q5 the motor powers the car and when required, the electric motor works in sync with the front axle to provide extra power when it’s needed, to pull up a hill for example. This means you can downsize the engine and the electric motor will give assistance when the power is required, and there are no mechanical connections or parts to spin in the axle. So there is only the electric motor which is powering the set of wheels,” explains Chandrasekar.
“In terms of in-wheel motors, it’s been talked about in the industry for a really long time, but we don’t see any application for it, although prototypes are out there. The question is who is going to buy the car, and cost is going to be a limiting factor.
“From my analysis, in-wheel motors will not be coming into the market any time soon. But we will see the axle-split hybrids where there is some connection between the axles and the wheels – the front axle being powered by the engine and the rear axle being powered by an electric motor. That is the only kind of architecture that I think we will see. The BMW I8 is an axle-split hybrid system…that is an all-wheel drive system. And you have your Audi Q 5 that is an axle split hybrid,” says Chandrasekar.
As long as OEMs continue to strive for improvements in traction and fuel economy, jobbers can rest assured that their driveline parts list will continue to grow as these vehicles begin making their way into independent repair shops for driveline service on a regular basis. And it’s a good bet that many will be in sooner rather than later.


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