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Ride by Wire: Part 1

A Case of Diminishing Returns?

By Philip Buonpastore

The new BMWs have it, most of the Harleys have it, the new Can-Am Spyder has it, so do many models of cars and even jet aircraft. What is it? Throttle, drive or fly by wire - electronic throttle control and engine management systems, of course.

To take on the entire concept of how electronic throttle control 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 motorcycles, and to examine the reasons why using electronic throttle control systems in motorcycles should be examined on its own merits as compared to its being used in almost any other mode of transportation.

As most know, throttle by wire replaces throttle cables with an electrically wired or electronic position sensor at the throttle handgrip that sends a signal to control the opening and closing of throttle plates. Some newer and "high-end" motorcycles, such as the new BMW 1600GT and GTL, also integrate throttle control with traction control, anti-lock brakes, and many other facets of engine and ride control management.

So, to establish why the use of throttle by wire (and ride control systems) might be viewed differently when these systems are used on motorcycles, let's start with the very basic differences between riding a motorcycle and driving an automobile:

  • You do not have to balance a car.
  • Cars rely very little on the gyroscopic effect of rotating wheels for stability.
  • Cars do not lean into turns.
  • There is a much greater level of physical protection while driving a car than when riding a motorcycle.

First, it should be established that some electronically controlled systems used in motorcycles are considered worthwhile by most riders and motorcycle authorities. A self-contained ABS system - that is, a system that is limited to preventing wheel lock-up in straight-line emergency stopping situations - is a benefit to the vast majority of motorcycle riders. Likewise, fuel injection systems on motorcycles are a great benefit: the fuel is dynamically adjusted for altitude, air pressure, ambient and engine temperature, and results in smoother throttle response, better drivability and greater fuel efficiency. It also requires the use of a fuel gauge, or at minimum a low-fuel light, giving the rider an objective indication of when they are low on fuel.

Where potential problems begin is in using a system where dynamic control of the mo-torcycle (or any vehicle for that matter) can be acted upon by an intermediate controlling system. Some anomalies in electronic engine and ride control systems (and drive-by-wire systems) have already been noted by motorcycle publications while testing bikes that incorporate this technology, and an Internet search turns up some very interesting, and somewhat alarming indications of a few not-so-great idiosyncrasies inherent in 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 shows some obvious "red flags." First, Mr. Acton says that the motorcycle "did something unexpected." Second, that the bike "didn't want to accelerate" and third, that "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 seemingly 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, from how Mr. Acton describes it. How often does your bike "do something unexpected"? Except for a malfunction, when was the last time you twisted the throttle and "the bike didn't want to accelerate," or the engine produced a "blast of horsepower" that unexpectedly lifted your front wheel off the ground?

Of course, it is difficult to know whether a typical street rider would be in a situation on a public road where they might be generating the combination of speed, lean angle and throttle position that John Acton was applying on the race track, but let's transfer the experiences he had to a possible real-world scenario:

An experienced sportbike rider ('he' for simplicity) is having a great day on his new S1000RR on a twisting mountain road. He is "into the groove," countersteering and getting some serious lean angles going and the bike is responding in stellar fashion. The rider gets a little over-zealous and come into a left-hand curve too hot, but as he is an experienced rider on a performance motorcycle, he has the presence of mind to lean the bike way over and manages to make the turn. But as he starts to countersteer and apply throttle to right the bike when coming out of the turn, the bike ... doesn't want to ... and faced with an emergency, the rider immediately applies more countersteer to get the bike upright in order to brake. All of a sudden ... he gets a blast of horsepower that lifts the front wheel off the ground. At that point, if he is not able to get the bike back under control very quickly, the rider is probably "hurled", alright - into the trees when the road makes the next right-hand corner that appears shortly after the left he just tried to recover from. A far-fetched scenario? Not from what was described in Mr. Acton's review.

Without intending to single out BMW motorcycles, the concern is an obvious one: an engine control system that can apparently usurp operator intent, and, as it seems in the review by John Acton, initiate a series of events that could cause unexpected alteration of a rider's control of the machine 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. While those who design these systems would be reticent to admit that this is a loss of control situation, it is hard to believe that the hypothetical of the rider on the mountain road described previously could never happen. The expression "that could never happen" is often used to assure the public, and everybody knows how it usually turns out.

Ask the people who have experienced unintended acceleration in their cars what they think when a corporate spokesman says that it can't happen. And 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, a quote about drive by wire used in motorcycles from the Bosch website (

"Thanks to the use of fully-electronic engine control systems, motorcyclists 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 RSV 1000 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."

So basically, 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 systems.

click here to read part 2

Philip Buonpastore/Fall 2011


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