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Posts Tagged ‘vehicle’

Sudden Acceleration Problem May Not Be Limited To Toyota Vehicles

8 million Toyota vehicles have been recalled due to issues relating to the gas pedal, as mentioned in CNNMoney today. Dr. David Gilbert of Southern Illinois University appeared on ABCNews demonstrating how, he claims, accelerator pedal units on certain Toyota vehicles are failing. Toyota mentioned in their Statement on Rebuttal of Professor Gilbert’s ‘Unintended Acceleration’ Demonstration

that he has reengineered and rewired the signals from the accelerator pedal. This rewired circuit is highly unlikely to occur naturally and can only be contrived in a laboratory. There is no evidence to suggest that this highly unlikely scenario has ever occurred in the real world. As shown in the Exponent and Toyota evaluations, with such artificial modifications, similar results can be obtained in other vehicles.

More popularly, however, are the problems with Toyota vehicles in which the accelerator pedal becomes trapped in the open-throttle position by an unnecessarily heavy floor mat. This seems to be the biggest cause for concern, as several documented cases of this happening have been recorded. Another issue, and reason for recall, has been caused by friction devices in the accelerator pedal unit wearing down and causing the pedal to stick, possibly in the partially open throttle position.

In Dr. Gilbert’s demonstration he basically “hacked” the throttle sending unit to make the powertrain control computer “think” that the pedal was being pressed to the floor. Previously, in mechanical throttle systems, a cable connected the pedal to the throttle plate, which was held closed by a spring. If the throttle cable broke, the plate would close due to the mechanical force of the spring. This demonstration would basically be the equivalent of cutting that cable, and pulling on the end that was still connected to the throttle plate. I guess if somebody decided to try and rewire their gas pedal, this type of event may occur. But naturally, I don’t think so.

Fully electronic throttle control units have been integrated in vehicles for some time now and are commonplace in almost all new vehicles produced today. This was something that we knew was eventually going to be an issue, and it’s certainly not limited to Toyota vehicles. This situation could occur in any vehicle utilizing an electronic throttle control unit. Now I’m not aware of any documented cases of these units failing in the manner that Dr. Gilbert demonstrated, and if anybody is, please reply to this post in the comments section with a link as proof. I have to admit that I am a little iffy about vehicles driving themselves, but as long as automakers continue to design the systems properly, and you keep any malicious electricians away from your gas pedal, I don’t think we really need to worry about it.

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Maybe I Was Wrong About Hybrids

I used to think that hybrid vehicles were a waste of time and energy. It made sense to me that a car that used an electric motor directly inline with the engine would never be efficient and would pretty much always be limited to the efficiency of the engine. If you’re new to the workings of gasoline hybrid technology, I’ll try to bring you up to speed. We’ve all heard of hybrid vehicles by now, they have a gasoline engine that is assisted by an electric motor and a bunch of batteries. There are two types of hybrids, series and parallel. Series hybrids have an electric motor mounted directly to (or basically on the same shaft as) the gas engine. The Toyata Prius and Honda Civic hybrids are the two best examples of these. Parallel hybrids have an electric generator mounted to the engine for the sole purpose of generating electricity for the electric motor that drives the wheels. Big diesel locomotives are a perfect example of this type of hybrid, which in my opinion, is the best type. For more information on hybrids, check out this Wikipedia page.

My big problem with hybrids was the fact that there have never been any commercially produced of the parallel type, they have all been series. This means that the engine still has to run at varying engine speeds depending on the speed of the vehicle, which is inefficient because gasoline engines are most efficient at a set speed and load. Upon researching the Prius, I came across the technical page explaining the Hybrid Synergy Drive. I now realize that vehicles that use this type of powertrain can function as both series and parallel hybrids. They accomplish this with two motor/generators that are connected to the engine and each other by a type of clutch and a continuously variable transmission (CVT). With this setup the engine can run independent of the wheels for the sole purpose of charging the battery, acting as a parallel hybrid. It can also function as a series hybrid by using one of the motors to assist the engine in acceleration and provide regenerative braking. The CVT in combination with the two motor/generators allows the engine to run mostly in it’s most efficient speed and load range. It seems to me, now, that the new technology added to these hybrids has utilized much more of the potential efficiency of gasoline engines, without the extra baggage of a full-out split parallel hybrid.

Despite this great new technology, I still don’t think that gasoline engines are the way to go. Diesel engines are far more thermodynamically efficient than their gasoline counterparts, we’ve known this for a long time. It’s all about the combustion process, compression ignition will always be more efficient because higher compression generally gives higher efficiency. A good running car with a four-cylinder diesel engine gets better mileage than one of the newer gas hybrids. I think we need a vehicle that features a small diesel engine coupled to one of the newer hybrid drive systems. That, in my opinion, would be the ideal hybrid.