4 ms·

The term "fly by wire" refers to the lack of mechanical linkage between the operator controls and the flight control surfaces. Cars have gone through similar d

The term "fly by wire" refers to the lack of mechanical linkage between the operator controls and the flight control surfaces. Cars have gone through similar design changes, yes. The car accelerator no longer opens valves/injectors for the gasoline to enter combustion chambers. In both cases - aircraft and cars - the primary goal was reducing weight. But this term is not intended to refer to driver-assistance features. [1] https://en.wikipedia.org/wiki/Drive_by_wire https://en.wikipedia.org/wiki/Drive_by_wire

kube-system 5y ago
> The car accelerator no longer opens valves/injectors for the gasoline to enter combustion chambers. The part you're thinking of is the throttle (which is why the accelerator pedal is sometimes called the throttle pedal), which controls the flow of air into the engine. The flow of gasoline has always been automated as a derived value from this (and often, other factors) -- even when engines were entirely mechanical; this was the function of the carburetor.
- sidewndr46 5y ago
  That's not universally true for internal combustion engines. Many old diesels had a "rack" that was tied to a system of levers. Each lever controlled a single fuel injector. The throttle cable was tied to this rack.
  - kube-system 5y ago
    That’s good context, but I did specify gasoline.
  - twofornone 5y ago
    Because diesels (even modern) don't use throttle plates. They control power entirely through fuel metering, as predetonation is not an issue given the the more robust cylinder design and nature of diesel fuel. Some diesels use so called J-brakes which effectively function as throttle plates to induce engine braking, but they are exclusively for slowing down the vehicle.
KennyBlanken 5y ago
> In both cases - aircraft and cars - the primary goal was reducing weight. That wikipedia article is a lot of unsourced nonsense written by complete idiots who clearly lack subject-area knowledge The goal for drive-by-wire in cars was primarily emissions reduction. Many cars "smooth" throttle inputs to improve mileage and emissions. In some cars "eco" mode exaggerates that smoothing, or changes the mapping of the throttle to allow for much more control over a lower portion of the throttle range. In others, "drive" is smoothed, and "sport" mode is not (unfortunately "sport" mode often makes the transmission far too aggressive.) It brings mechanical simplicity, because cruise control can be integrated in. Drive by wire throttles were notoriously unreliable for almost a decade after their introduction. They get gummed up, the actuators fail, the position sensors fail, etc. It's a laugh that the article claims they're "easier to service" - they're usually buried in difficult-to-access places and there's nothing "serviceable" about them compared to a true mechanical throttle that can usually be completely rebuilt.
- jacquesm 5y ago
  Correct. The whole idea was to decouple the accelerator pedal from the throttle using a sensor, a computer and an actuator to ensure that the right amount of fuel/air would be passed into the engine. https://en.wikipedia.org/wiki/Stoichiometry https://en.wikipedia.org/wiki/Stoichiometry If you don't do that then the excess fuel goes back out unburned. Multi point injection has changed this process a bit in that compared to the first single point injection systems the fuel is mixed with the air on a per-cylinder basis leading to better fuel economy and even more efficient combustion. This is also why these systems have air mass sensors, the amount of air is an important thing to measure in order to determine the right amount of fuel. Essentially fuel injection systems they have all of the complexity of a servo system, and the number of failure points compared to a direct linkage is huge, especially when you have a block that is split into two cylinder banks, V or Boxer.
  - KennyBlanken 5y ago
    Drive by wire throttles have nothing to do "ensuring the right amount of fuel/air would be passed into the engine."

kube-system 5y ago

> The car accelerator no longer opens valves/injectors for the gasoline to enter combustion chambers. The part you're thinking of is the throttle (which is why the accelerator pedal is sometimes called the throttle pedal), which controls the flow of air into the engine. The flow of gasoline has always been automated as a derived value from this (and often, other factors) -- even when engines were entirely mechanical; this was the function of the carburetor.

sidewndr46 5y ago
That's not universally true for internal combustion engines. Many old diesels had a "rack" that was tied to a system of levers. Each lever controlled a single fuel injector. The throttle cable was tied to this rack.
- kube-system 5y ago
  That’s good context, but I did specify gasoline.
- twofornone 5y ago
  Because diesels (even modern) don't use throttle plates. They control power entirely through fuel metering, as predetonation is not an issue given the the more robust cylinder design and nature of diesel fuel. Some diesels use so called J-brakes which effectively function as throttle plates to induce engine braking, but they are exclusively for slowing down the vehicle.

KennyBlanken 5y ago

> In both cases - aircraft and cars - the primary goal was reducing weight. That wikipedia article is a lot of unsourced nonsense written by complete idiots who clearly lack subject-area knowledge The goal for drive-by-wire in cars was primarily emissions reduction. Many cars "smooth" throttle inputs to improve mileage and emissions. In some cars "eco" mode exaggerates that smoothing, or changes the mapping of the throttle to allow for much more control over a lower portion of the throttle range. In others, "drive" is smoothed, and "sport" mode is not (unfortunately "sport" mode often makes the transmission far too aggressive.) It brings mechanical simplicity, because cruise control can be integrated in. Drive by wire throttles were notoriously unreliable for almost a decade after their introduction. They get gummed up, the actuators fail, the position sensors fail, etc. It's a laugh that the article claims they're "easier to service" - they're usually buried in difficult-to-access places and there's nothing "serviceable" about them compared to a true mechanical throttle that can usually be completely rebuilt.

jacquesm 5y ago
Correct. The whole idea was to decouple the accelerator pedal from the throttle using a sensor, a computer and an actuator to ensure that the right amount of fuel/air would be passed into the engine. https://en.wikipedia.org/wiki/Stoichiometry https://en.wikipedia.org/wiki/Stoichiometry If you don't do that then the excess fuel goes back out unburned. Multi point injection has changed this process a bit in that compared to the first single point injection systems the fuel is mixed with the air on a per-cylinder basis leading to better fuel economy and even more efficient combustion. This is also why these systems have air mass sensors, the amount of air is an important thing to measure in order to determine the right amount of fuel. Essentially fuel injection systems they have all of the complexity of a servo system, and the number of failure points compared to a direct linkage is huge, especially when you have a block that is split into two cylinder banks, V or Boxer.
- KennyBlanken 5y ago
  Drive by wire throttles have nothing to do "ensuring the right amount of fuel/air would be passed into the engine."