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Throttle-by-wire replaces throttle cables with an electrically wired or electronic position sensor at the throttle handgrip.
To take on the entire concept of how throttle-by-wire (TBW; used here throughout for simplicity) is used in every type of transportation technology is to exceed the scope of what can be covered here, but there is much that can be discussed about the positives and negatives of using such a system in Trikes. Here, we’ll touch upon some reasons why using electronic throttle control systems in Trikes should be examined on its own merits as compared to its being used in almost any other mode of transportation. The intention of this article is provoking an open a dialog about the use of technology and not an endorsement or indictment of the role electronics serve on our Trikes.
As most know, throttle-by-wire replaces throttle cables with an electrically wired or electronic position sensor at the throttle handgrip that transmits a signal to a motor controlling the opening and closing of throttle plate(s) (butterfly). Some newer and “high-end” motorcycles and Trikes, such as the new touring BMW 1600GT and GTL and Can-Am Spyder, also integrate throttle control with traction control, anti-lock brakes (ABS) and many other facets of engine and ride control management. Since 2008, Harley-Davidson’s Touring models and all of its modern Trikes employed the cableless throttle mechanism.
So, to establish why the use of TBW and ride control systems might be viewed differently when these systems are used on Trikes, let’s start with the very basic differences between riding a Trikeand driving an automobile:
• The extra wheel on a car provides increased stability and tip-over protection
• Cars rely very little on the gyroscopic effect of rotating wheels for stability.
• Cars do not roll as much going into turns.
• There is a much greater level of physical protection while driving a car than when riding a Trike.
First, it should be established that some electronically controlled systems used in Trikes are considered worthwhile by most riders and Trike authorities. Fuel injection systems on Trikes are a great benefit: the fuel is dynamically adjusted for altitude, air pressure, ambient and engine temperature, resulting in smoother throttle response, better drivability and greater fuel efficiency. It also requires the use of a fuel gauge, or at a minimum a low-fuel light, giving the rider an objective indication of when they are low on fuel. There can even be an argument made for safety here as reaching down to change over the petcock to reserve can often be a tricky situation. How many times has your Trike sputtered making a turn in traffic and you had frantically tried keeping the Trike controlled as it bucked and surged while you tried not to get rear-ended?
Where potential problems begin is in using a system where dynamic control of the Trike (or any vehicle for that matter) is modifies and controlled by an intermediate controlling system not in direct control of the rider. Some anomalies in TBW systems have already been noted by motorcycle publications while testing bikes that incorporate TBW and an Internet search turns up some very interesting, and potentially alarming characteristics regarding these systems. For example, here’s the first paragraph of a review of the 2011 BMW S1000RR written by John Acton in February 2010: “Coming out of the long right-hand turn nine at Palm Beach International Raceway, BMW’s new S1000RR did something unexpected. Despite having the throttle pinned wide-open, the bike didn’t want to accelerate. It wasn’t until the lean angle came within 45 degrees from vertical that a blast of horsepower from the Bavarian bullet lifted the front wheel about a foot off the asphalt and hurled the bike down the 0.6-mile straightaway.”
Even a cursory read of the first paragraph of this review raises some obvious red flags. First, Mr. Acton says that the motorcycle, “did something unexpected;” that the bike “didn’t want to accelerate,” and third, “it wasn’t until the lean angle came within 45 degrees…that a blast of horsepower…lifted the front wheel about a foot off the asphalt and hurled the bike down the 0.6 mile straightaway.” The entire opening paragraph outlines a series of occurrences where the rider was not in control of the bike! Not just one hiccup, but a list of events in a high-speed situation that were not in rider control, and it actually surprised him, as Mr. Acton describes it. What is missing from that paragraph however is the BMW was set up for the racetrack and running in “Slick” mode used for racing situations. With a less experienced rider that could be a scary and dangerous scenario.
Extending the logic here, how often does your Trike “do something unexpected?” Except in a malfunction, when was the last time you twisted the throttle and “the Trike didn’t want to accelerate?” Alternatively, how about the engine producing a “blast of horsepower” that unexpectedly lifted your front wheel off the ground?
Without intending to single out BMW motorcycles, the problem is obvious: an engine control system that can apparently usurp operator intent, and possibly initiate a series of events that could cause unexpected alteration of a rider’s control of the machine. This could occur at a time when the rider must fully rely on the physics of how the machine will behave and the expectation of how it will respond at a very critical control point. The expression “that could never happen” is often used to assure the public, and everybody knows how it usually turns out. Our computers and all other electronic gadgets we use every day were tested not to crash in a controlled environment, yet we all know that certain combinations of factors can and do cause malfunctions and quirky behavior. Even something as simple as the tried and true cable operated carb or throttle body has a safety factor built into it. In fact, the extra cable on push-pull throttle-cable systems was a safety measure employed to be able to close the butterfly in case of cable or other malfunction in the carb.
Ask the people who have experienced unintended acceleration in their cars what they think when a corporate spokesperson says, “it can’t happen.” Moreover, in case you think these are isolated incidents, according to a Consumer Reports article from December 2009, fifty-two unintended acceleration complaints were reported to the National Highway Transportation Safety Administration (NHTSA) about Toyota products (Toyota and Infinity) and 36 complaints were lodged about Ford products produced in the 2007-2008 model year. While these occurrences took place in automobiles, an excerpt from article about TBW used in motorcycles from the Bosch (manufacturer of many TBW and other electronic technologies) website is of particular interest: “Thanks to the use of fully-electronic engine control systems, motorcyclists (Trikers) now have complete control over their machines, too. To do this, existing automotive systems were adapted to motorbikes within the framework of our drive-by-wire motorcycle study. The first road-capable prototype is an Aprilia RSV1000 R. In selecting the components, we rely on Bosch components from the automotive sector, which are thus now available for the motorcycle market. The development of the electronically controlled throttle valve for motorbikes is yet another example of customer-specific, individual system adaptations of Bosch components for which Bosch Engineering GmbH is internationally known.”
(www.bosch-engineering.de/en/boschengineeringgmbh/newsspecials/drive_by_wire.aspx or click HERE)
Therefore, what Bosch is saying here is that motorcycle “fully electronic control systems” are adapted from automotive systems. It is logical then to consider that any potential hardware failures and software programming errors that by some accounts have already occurred in automotive systems could also be potential problems in motorcycle and Trike systems.
Let’s examine another important point: the anomalies in the S1000RR engine management system that Mr. Acton described were not malfunctions. The loss of throttle control, the inability to accelerate when the bike was leaned, and the (unexpected) surge of power when the bike was partially righted is apparently how the electronic engine and traction control management system for this bike are designed and programmed to work under those conditions. Oddly, in the review of the S1000RR, Mr. Acton did not seem alarmed by this situation where control of the bike was apparently out of his hands, and he generally gave the bike a favorable review. Racers seem to love the technology since these systems produce faster and better times on the track without the rider actually becoming, well, a better rider through increased skills.
So here, we have an example of an anomaly in the electronic engine control system when the bike is functioning properly. How about what happens when things do malfunction?
In some recent discussions with David Hough (author of the Proficient Motorcycling book series) on the issue of throttle control and electronic engine management, he relayed a situation where a Can-Am Spyder (with TBW) had a reoccurring drivability problem: “I had some…electronic issues, one being that the engine would suddenly go into limp home mode after hours on the freeway. I found that shutting off the main switch for a period of time would…allow the system to reboot, and then it would start and run normally. The error message on the dash showed “check DPS computer.” DPS is Dynamic Power Steering—sort of a “mother” computer, and if a fault in any of the other systems occurred, the DPS computer would signal the Engine Management Computer to initiate a loss of power…I [later] discovered that the leaf spring on the brake pedal was not giving the appropriate “brake off” signal to the DPS computer. I did a little adjusting with needle nose pliers, and solved the limp home problem.”
As many know, “limp home” mode is where an engine management system will limit speed and acceleration in order to prevent engine damage when a problem occurs. Many of our Trikes have this feature. However, in this case, the limp home mode erroneously activated on a freeway when the problem apparently had nothing to do with an engine malfunction. Here is a case where an electronic override system caused the Trike (with a Rotax motorcycle engine used by many manufacturers) to suddenly slow down on a freeway while other traffic around the vehicle would normally be maintaining highway speeds. While this scenario might make sense if the limp home mode had been activated due to an engine problem, should it have been caused by a simple mechanical problem with a brake signal switch? Most would probably argue no. Broken, chafed or worn out wires are not the exception on a well-ridden Trike- it will happen and what can happen as a result is not as predictable like older machines.
This next part is for all of us to consider and think about. David goes on to say: “I’m not so concerned about complex systems when they are brand new. I’m more concerned about maintainability. What happens to the high-zoot electronic system 5 years down the road, or longer?…The owner who has all of his maintenance and repair[s] done at the dealer’s shop will buy a brand that has a nearby dealer, and be clever enough to trade it in as the warrantee expires. But for owners such as myself, who…do our own servicing and repair, there is a practical limit to how complex a machine can be.”
As David points out, what happens to ridability of the Trike when a totally integrated throttle/traction control/braking system experiences failures or components wear out? The increasingly higher levels of technology may start to yield diminishing returns when the engineering that goes into them gets so complex that a machine can no longer be reasonably maintained by an owner, and very high expense is necessary for their repair. Have you had your Trike in the shop for repairs lately? Even the simplest maintenance procedures performed in a Trike repair shop often yield an expensive bill. Try to imagine the bill when electronic engine management components begin to fail and all problems diagnosed and repaired at a dealership. Having to trade-in a Trike before the warranty period expires is an option that most currently typically cannot afford, or even want, to make.
Perhaps a “simpler” TBW system that is not part of an overall engine management system may not be significantly more complicated in principal than throttle cables, but there are some notable differences: finding the source of a cable problem will usually only require visual inspection, maybe getting the Trike back to your garage and removing the fuel tank or body panels to locate a cable restriction or to lubricate a cable or to replace a broken one. Repairing an electronically controlled throttle system would typically require troubleshooting knowledge that exceeds that of a typical DIY mechanic and the use of diagnostic equipment that most will not own or even know how to use.
So how much more will the costs be to repair the higher level of complexity of systems that incorporate TBW, traction control and braking into an engine management system? How much of an effect on the ability to continue to operate the Trike and even the safety of the rider if a failure of even one of the systems occur? As these systems are still relatively new, the jury will be out for some time.
Of course, it is understood that a tremendous amount of R&D goes into getting these systems to be useable, functional, reliable and safe, and that in the vast majority of riding circumstances, riders will find the increased options for choice of ride type, handling and braking capability will take Trike riding to new levels of comfort and convenience. While in the majority of situations the computer will choose the best combination of handling characteristics in a given riding situation, some of the reviews and reports indicate that this may not always be the case. David Hough’s experience with his Spyder going into limp mode due to a simple mechanical problem is one example; John Acton’s description of the BMW’s behavior is another.
There are also discussions posted on several Harley-Davidson owner group sites concerning idle variation problems on TBW-equipped Baggers/Trikes, most notably V-TwinForum.com and HDForums.com, with the latter having a link to a service bulletin released by Harley-Davidson referring to a TBW problem. Several posts say that the throttle control problems occurred while the machines were being ridden, rather than just at idle.
We experienced firsthand one such case where the loss of throttle control (albeit a two-wheeler, but the exact same system employed on the Trikes) resulted in an extremely dangerous situation. Quick thinking and luck proved to avoid disaster. While riding a new 2009 CVO Road Glide with less than 2,000 miles on the clock the TBW system did something that “can’t happen.” While riding on a four-lane freeway packed with loaded 18-wheelers blazing out of the Port of Long Beach and commuters buzzing along bumper to bumper at 80 mph the Glide lost the throttle. Being in the left lane with no shoulder and a 6-foot tall retaining wall to the side this was no place to experience a malfunction. At first, the bike hiccupped and continued running when suddenly all propulsion was gone, coasting at this point with the car behind thankfully slowing to avoid the unexpected slow down. . There weren’t any pull over options. Not knowing what was happening we tried pulling in the clutch, as a broken belt was the first thought of the symptom experienced. With the clutch disengaged, we noticed the engine dropped to idle, the opposite of what would be expected under those conditions. Twisting the throttle had zero effect on RPM. Frantically waving our left arm to try to get to tjhe shoulder we began moving rightward and the bike surged as the throttle/throttle body/computer kicked back into action. That was another potentially disastrous situation as we were attempting to get over while trying to convince and alert drivers we had a problem. For the next 15 seconds or so the bike’s brain went into and out of consciousness. Making the side of the road the bike was now idling and the throttle had no effect on the motor. The police showed up to get us out of the situation- either call a tow truck or get moving was the order. We shut the motor down and the bike’s power- restarted and still nothing. A few attempts at this and the throttle came back on line. 100 yards down the shoulder and the throttle went out again. An off-ramp a mile down the road was the target and after a few of these start stop conditions the bike made it off the freeway and died at the top of the ramp. It wouldn’t start. Pushing the bike off the ramp and into a safer place, we removed the seat, figuring it was an electrical problem began poking and prodding the wires under the seat. Nothing. We just wanted to get home and not have to get this brand new bike scratched or damaged from towing. As nothing was helping and the bike was still dead, the gentle discovery of the problem was replaced by anger and we pulled on every harness we could find. The bike fired up and ran well for the 10-mile ride home on surface streets. Just as we turned into the driveway the bike completely died, barely avoided dropping it as it lost power midturn, and coasted to the garage. A Harley-Davidson technician picked the bike up and noticed the computer’s memory had “a lot” of fault codes due to malfunctions in the system. The bike was hauled away and returned a few days later “fixed.”
Us: “So, what was the problem?”
Them: “Nothing. We didn’t find any problems.”
Us: “What does that mean? The bike had a mind of its own and you couldn’t get it to start when you picked it up.”
Them: “We took the fairing off to have a look around and found nothing wrong, so we put it back together and the bike ran fine.”
Us: “What about all the fault codes?”
Them: “They had nothing to do with the bike not starting or any problem with the throttle and apparently showed up because the system went crazy.”
“Us: “That’s it? Nothing’s wrong and you found nothing, yet the throttle didn’t work and then the starter wouldn’t turn over? And now it’s fine?”
Them: “We couldn’t find anything that would cause that problem. Just ride it and let us know if there are any other problems.”
We never did have another problem with that bike; it ran perfectly. What was it? A computer virus, solar radiation, gremlins, a bug in the software that Harley didn’t admit to? Whatever it was, it wasn’t normal, it was a bone stock machine with nothing added on to it and everything wasn’t alright. Quick thinking, skill and a little luck were all that prevented this “nothing’s wrong” scenario from being catastrophic.
Further, in the cases of claimed unintended acceleration in automobiles, throttle and engine management computers may have no direct “cause and affect” as to how they may operate should a control system get an errant control input. On older bikes and Trikes, a shorted or broken wire produced easily identifiable consequences. That TBW uses an electronic signal rather than cables, a system malfunction could conceivably result in a variety of unexpected control problems, simply because triggering an electrical short, open circuit, or component failure could cause an electronic hardware problem, a software error or both. A Trikemay accelerate, go to idle, shut off, go into limp home mode—any of a number of unexpected behaviors based on a wrong signal in an electronic engine management system. Furthermore, fixing the short or ground situation on the side of the road doesn’t always fix the problem. Computers may need to have codes cleared, be updated or rebooted.
Conclusion
In the engineering field, there is a concept known as “elegance.” It refers to the idea that the more you strive to keep electronic systems and their software programming simple, the less likely that bugs or unintended outcomes will result. The idea of keeping Trike control systems simple is worth considering for this reason. Consider also that following the “KISS” principle here may also be a good idea due to the lower level of physical protection for the rider of a Trike, as opposed to a car. There is a logical connection between these two thoughts: if a throttle system were to malfunction causing unintended de- or acceleration, a resulting accident would certainly have a greater potential for serious physical injury on a Trike than in a car.
Technology with a proven track record of decades in use are logical additions to Trikes, and while electronic fuel injection is more complicated than a carburetor, you get a lot for the tradeoff for the relatively small increase in complexity.
Some thoughts to ponder: Will there be high-mileage TBW Trikesstill around and usable in 20 years? 30 or 40? Will the cost of repair exceed the value, as is the case with the current “buy it, drive it, junk it philosophy” of many automobiles. Planned obsolescence as it’s called; it’s seemingly designed into everything these days. How many of you early H-D EFI owners junked a perfectly good Trike because of the Magneti-Marelli manufactured throttle body? Even when in optimal shape that system was mediocre at best for its given application and miles just made it worse, wearing out parts that can’t be fixed, leading to a Trike that cannot run correctly. There are upgrades and solutions but all cost in the thousands of dollars. The decision is then, junk it or dump a boatload of cash into it that may equal the value of the Trike?
Please share your thoughts on this with us. Have you had any odd experiences or lack of control from a TBW system or expensive repairs? We’ll share your responses and opinions right here.
We’d like to thank Aaron Frank of Motorcyclist magazine (motorcyclistonline.com) for input and discussions relating to TBW and this article.
