Drive-by-wire throttle: It's not so bad!

September 28, 8:37 PMOrlando Auto ExaminerMichael Block

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As technology advances, new and more efficient devices become more affordable, and old and inefficient technology, while becoming even more affordable, becomes obsolete. As a result, the advantages of sticking with the old technology because of its cheap price are soon no longer apparent. Although the new technology may be more expensive, the increased productivity of the person operating it due to its higher efficiency begins to outweigh the cost savings of the outdated technology.

A significant update in technology has recently become popular in the world of automobiles: drive-by-wire throttle control. What this means is that there is no mechanical connection between the driver’s right foot and the throttle body on the engine. The accelerator pedal has a sensor that reads how hard the driver is pressing down; it relays that signal to the engine computer, which sends a signal to the electronic throttle body to open the butterfly valve – the valve which regulates the amount of air entering the engine – accordingly.

Through my own experience from working at a car dealership that carries the Mazda and Subaru franchises, I have learned that virtually all Mazdas since 2004 have been using drive-by-wire technology, and that all Subarus since 2005 have as well. Many other manufacturers are utilizing drive-by-wire throttle, including Honda and Toyota.

There lies a dilemma in all this; a dilemma that I understand as an automotive enthusiast. First and foremost, there is almost always a very small delay between the driver pushing the accelerator pedal and the throttle body opening the butterfly valve. During day-to-day commuting, this is barely noticeable, if at all. But on a racetrack, where every millisecond can count, it becomes a much bigger problem. Then there’s the argument of aesthetics, that the driver no longer feels connected to the car.

But I believe that, ultimately, drive-by-wire throttle is the way to go. The advantages of this new technology outweigh those of the old technology, and here are two reasons why:

-          Drive-by-wire throttle now controls the idle speed of the engine. In the earlier days of fuel injection, the butterfly valve in the throttle body was completely shut during idle. To keep the engine running, a bypass valve was frequently fitted to the engine to allow a small amount of air to enter and thereby regulate and set the idle speed. Since the mechanical connection between the accelerator pedal and the throttle body has now been removed, the throttle body can now regulate the idle itself, with no need for a bypass valve.

-          The drive-by-wire throttle body is now the cruise control system in its entirety. Cruise control allows the driver to set the speed of the car as it cruises down a highway, so the driver can rest his or her foot. This used to be a very complicated system separated from the rest of the car’s electronics, in which the standalone cruise control computer regulated a certain amount of engine vacuum, which in turn controlled a cable attached to the throttle body. Now that the throttle body is electronically operated, the throttle body receives the cruise control settings directly from the engine computer, thus eliminating the whole cruise control system.

So, the car today has been made much simpler than the car of yesterday in this respect. If something goes wrong with any of those aforementioned systems, there’s only one thing to replace, and that’s the electronic throttle body.

Now, if you’re still skeptical, I imagine that what you’re probably thinking is that that electronic throttle body is so full of technological gizmos because of all these new responsibilities that it carries, that it must cost as much as all of those other components.

But that is not true at all.

From my experience, electronic throttle bodies run somewhere between three to six hundred dollars. Indeed, that is quite a hefty sum.

But consider this situation:

An older car comes into a shop with three problems. For the sake of argument, we’re going to ignore the value of the car or the potential obsolescence of parts for an old car. The cruise control system is shot, it won’t idle right, and the throttle position sensor (the sensor that tells the engine computer how much the driver is opening the mechanical throttle body) is bad. The cost of replacing the entire cruise control system could easily approach six hundred dollars in parts alone, the bypass valve that regulates the idle can be another three hundred dollars, and the throttle position sensor can be another hundred dollars. Again, we’re not including the labor to replace these parts, which can get very intensive because the mechanic has to go to three different places on the car to replace them all. When all is said and done, the total cost of these repairs could very well reach two thousand dollars.

But if a newer car with drive-by-wire throttle comes in with the exact same problems, all three of them can be traced back to one source: the electronic throttle body. There are no cruise control systems or bypass valves at all. Even if we take the highest figure of six hundred dollars, it still works out to be a lot cheaper. Plus, the labor will be cheaper as well, because all the mechanic has to do is remove and unplug the faulty throttle body, and install and plug in the new one.

There are more advantages to a drive-by-wire throttle system, such as increased fuel mileage and reduced emissions, but this article is already nerdy enough!

As for the issue of delay in throttle response, and the sense of detachment from driving enjoyment, all I can say is that the technology is relatively new, and that as time goes on, it will surely improve.

Now, I want to specify that I am only praising drive-by-wire throttle systems, and that I don’t feel quite comfortable enough endorsing the use of drive-by-wire technology in other automotive components such as the steering or braking systems. First off, if a drive-by-wire throttle body malfunctions, the worst thing that can happen is that the car quits running and comes to a stop. If a drive-by-wire steering or braking system malfunctions, it may not be possible to control or stop the car. That’s dangerous enough. There have also been cars designed to be operated by joysticks (see the For More Info box), and my issue with those is that we have calibrated ourselves to drive cars with steering wheels and pedals for over a century, and the average driver will likely not be able to negotiate the car through a corner, or especially an emergency maneuver, due to his or her unfamiliarity with the new controls.

Since such cars are not legal for highway use, I’m apparently not the only one sharing that concern.

So, for those who have seen the Terminator movies a few too many times, and fear that electronics are taking over our lives through our cars, you have no need to worry!

The drive-by-wire throttle system was designed to make driving more efficient and economical, not take away from the driving experience. I think the miniscule throttle delay (which could possibly no longer be a problem soon) is a small price to pay for the increased efficiency and economy of the drive-by-wire throttle system.