7 ms·

I was always taught that the mechanical override was shifting it out of drive and into neutral.

by makerops 13y ago

michael_h 13y ago
This is true for most vehicles, but on some cars (like the Prius) the shifter is not mechanical. Yes, it's unnerving.
- msandford 13y ago
  That's why you buy a car with a manual transmission. Those haven't been electronic-ized yet and are unlikely to be as the forces involved in depressing the clutch are substantial and unlikely to go away. Once the clutch plates are no longer in contact the engine can do whatever it wants but none of that makes it to the wheels. And then you can get the car out of gear to coast, turn the whole car off and then back on. There's no substitute to having a human being in the loop to execute high-level "executive" functions, especially when things aren't done to the very high standards of aerospace. You know, like cars.
  - drbawb 13y ago
    > That's why you buy a car with a clutch pedal. There exist "manual transmission" that lack an operator controlled clutch. DCTs are very much manual transmissions, but many of them rely on a TCM to disengage the clutches.
  - bri3d 13y ago
    I do agree that having a hydraulic (or cable)-clutch car eliminates the ECU from a critical path (power to wheels), but there are plenty of electronic-ized manuals. There are all sorts of advanced DSG / dual-clutched transmissions in many newer cars, but even some older cars like the MR2 and Smart cars have a http://en.wikipedia.org/wiki/Electrohydraulic_manual_transmission http://en.wikipedia.org/wiki/Electrohydraulic_manual_transmi... : quite literally a manual transmission where the clutch has been actuated electronically.
- drbawb 13y ago
  The list is only growing longer . . . If you have computer-assisted hill starts, collision avoidance, or computer assisted braking [through ABS, certain traction & stability control systems, etc] your computer has control of your brakes. If you have range-assisted cruise control, or early collision alert, your computer likely has total control over your throttle. If you have parking assist, lane departure warning, lane following assist, or electric power steering etc: your computer has control over your steering. If your car has a DCT: your computer has control over your shifting _as well as both clutches._ -- Meaning you have _no mechanical interface_ to disengage the motor from the transmission. This is similar to your Prius example: the shifter is not mechanical. On many new cars: there's no ignition key to remove. You likely have a smart "keyfob" that simply needs to be within X-feet of the car, and then you have a push button ignition. I'm sure there's some override for the button [push and hold for three seconds], but it's still going to go through some electronics to figure that out. --- The only bit that scares me is that all these systems potentially share the CAN bus with the horrendous "Infotainment" systems that every manufacturer loves to install. shudders
  - fnordfnordfnord 13y ago
    Mfrs have started using LIN for slow-control accessories like power windows, door locks, wipers, etc. A separate CAN for critical functions of the auto, and another (sometimes CAN) system for non-critical things like GPS integration, entertainment, and (apparently) MOSTbus has finally taken off after much teeth gnashing. MOST is a higher bandwidth than CAN bus system designed for 'infotainment' systems in autos. https://en.wikipedia.org/wiki/MOST_Bus https://en.wikipedia.org/wiki/MOST_Bus
    - drbawb 13y ago
      Thanks for sharing! I have to admit though I'm surprised that some of those accessories even require a bus as they're typically operated by simple switches. I guess door locks, wipers, etc. make some sense: with the prevalence of central locking, as well as wipers that sense rain and things like that. Windows are a bit odd, as they just need a very simple switch. I suppose having all the accessories on a common bus must simplify the wiring harness though. --- I'm curious how TESLA integrates their in-dash system with the rest of the car. I thought their in-dash console could control some rather safety-critical "preferences" of the car ... for instance I thought you could adjust the level of regenerative braking. (Other manufacturers are also offering "sport modes", etc -- though they're not always controllable through the dash.)
matt-attack 13y ago
I agree. With a Camry, shifting into N would have immediately remedied the problem. I remember hearing reports claiming: "Shifting to N didn't do anything". The explanation always seemed obvious to me: Non-technical driver experiences UA. In a panic shifts into neutral. Hears engine scream. Thinks, "The car is still going!" and doesn't realize that despite the sound, the car is actually slowing down. I know this to be a common misconception in my experience. People commonly misinterpret high revs with "going fast".
- drbawb 13y ago
  Oh wow, good point, I hadn't thought of that. "High revs" = "motor going fast" to me, not "wheels going fast." But I had not considered that this correlation is only intuitive to me because I own a car with a manual transmission.
  - Zancarius 13y ago
    I'd imagine the sudden loss of power should be apparent as well. But then, people can react irrationally (or not at all) in a full on panic.

I was always taught that the mechanical override was shifting it out of drive and into neutral.

michael_h 13y ago

This is true for most vehicles, but on some cars (like the Prius) the shifter is not mechanical. Yes, it's unnerving.

msandford 13y ago
That's why you buy a car with a manual transmission. Those haven't been electronic-ized yet and are unlikely to be as the forces involved in depressing the clutch are substantial and unlikely to go away. Once the clutch plates are no longer in contact the engine can do whatever it wants but none of that makes it to the wheels. And then you can get the car out of gear to coast, turn the whole car off and then back on. There's no substitute to having a human being in the loop to execute high-level "executive" functions, especially when things aren't done to the very high standards of aerospace. You know, like cars.
- drbawb 13y ago
  > That's why you buy a car with a clutch pedal. There exist "manual transmission" that lack an operator controlled clutch. DCTs are very much manual transmissions, but many of them rely on a TCM to disengage the clutches.
- bri3d 13y ago
  I do agree that having a hydraulic (or cable)-clutch car eliminates the ECU from a critical path (power to wheels), but there are plenty of electronic-ized manuals. There are all sorts of advanced DSG / dual-clutched transmissions in many newer cars, but even some older cars like the MR2 and Smart cars have a http://en.wikipedia.org/wiki/Electrohydraulic_manual_transmission http://en.wikipedia.org/wiki/Electrohydraulic_manual_transmi... : quite literally a manual transmission where the clutch has been actuated electronically.
drbawb 13y ago
The list is only growing longer . . . If you have computer-assisted hill starts, collision avoidance, or computer assisted braking [through ABS, certain traction & stability control systems, etc] your computer has control of your brakes. If you have range-assisted cruise control, or early collision alert, your computer likely has total control over your throttle. If you have parking assist, lane departure warning, lane following assist, or electric power steering etc: your computer has control over your steering. If your car has a DCT: your computer has control over your shifting _as well as both clutches._ -- Meaning you have _no mechanical interface_ to disengage the motor from the transmission. This is similar to your Prius example: the shifter is not mechanical. On many new cars: there's no ignition key to remove. You likely have a smart "keyfob" that simply needs to be within X-feet of the car, and then you have a push button ignition. I'm sure there's some override for the button [push and hold for three seconds], but it's still going to go through some electronics to figure that out. --- The only bit that scares me is that all these systems potentially share the CAN bus with the horrendous "Infotainment" systems that every manufacturer loves to install. shudders
- fnordfnordfnord 13y ago
  Mfrs have started using LIN for slow-control accessories like power windows, door locks, wipers, etc. A separate CAN for critical functions of the auto, and another (sometimes CAN) system for non-critical things like GPS integration, entertainment, and (apparently) MOSTbus has finally taken off after much teeth gnashing. MOST is a higher bandwidth than CAN bus system designed for 'infotainment' systems in autos. https://en.wikipedia.org/wiki/MOST_Bus https://en.wikipedia.org/wiki/MOST_Bus
  - drbawb 13y ago
    Thanks for sharing! I have to admit though I'm surprised that some of those accessories even require a bus as they're typically operated by simple switches. I guess door locks, wipers, etc. make some sense: with the prevalence of central locking, as well as wipers that sense rain and things like that. Windows are a bit odd, as they just need a very simple switch. I suppose having all the accessories on a common bus must simplify the wiring harness though. --- I'm curious how TESLA integrates their in-dash system with the rest of the car. I thought their in-dash console could control some rather safety-critical "preferences" of the car ... for instance I thought you could adjust the level of regenerative braking. (Other manufacturers are also offering "sport modes", etc -- though they're not always controllable through the dash.)

matt-attack 13y ago

I agree. With a Camry, shifting into N would have immediately remedied the problem. I remember hearing reports claiming: "Shifting to N didn't do anything". The explanation always seemed obvious to me: Non-technical driver experiences UA. In a panic shifts into neutral. Hears engine scream. Thinks, "The car is still going!" and doesn't realize that despite the sound, the car is actually slowing down. I know this to be a common misconception in my experience. People commonly misinterpret high revs with "going fast".

drbawb 13y ago
Oh wow, good point, I hadn't thought of that. "High revs" = "motor going fast" to me, not "wheels going fast." But I had not considered that this correlation is only intuitive to me because I own a car with a manual transmission.
- Zancarius 13y ago
  I'd imagine the sudden loss of power should be apparent as well. But then, people can react irrationally (or not at all) in a full on panic.