Article to explain why Toyota pedal fix may not be so good

ChrisSuich · **Posted:** Wed Feb 03, 2010 1:24 pm

Nice analysis of the problem...

http://www.thetruthaboutcars.com/why-toyota-must-replace-flawed-cts-gas-pedal-with-superior-denso-pedal/

Vincent Keene · **Posted:** Wed Feb 03, 2010 1:29 pm

Quote:

Toyota uses two different electronic gas pedal designs in its cars.

There's your problem right there. Why the hell does a gas pedal need to be electronic? The whole DBW thing sounds like something a German engineer would come up with and use. I thought the Japanese were smarter. Guess I was wrong.

Jason Tower · **Joined:** Wed Jun 11, 2008 3:31 pm **Posts:** 1173

Vincent Keene wrote:

Quote:

Toyota uses two different electronic gas pedal designs in its cars.

There's your problem right there. Why the hell does a gas pedal need to be electronic? The whole DBW thing sounds like something a German engineer would come up with and use. I thought the Japanese were smarter. Guess I was wrong.

the mercedes s-class (w220 i think) was the first mass produced car to use throttle by wire, i worked for the company that made the pedal assembly. spent a fair amount of time at the facility in werne, germany where it was assembled as the company wanted to have the ability to sell it domestically and we'd have to manufacture it here. at the core it was a programmable angular position sensor, but since the pedal only pivots about 10 or 15 deg that didn't give enough sensitivity or resolution. so there was a complex arrangements of pivots, levers, teflon-coated cables, etc that amplified 15 deg of pedal movement into about 80 deg (iirc) of sensor movement. not only that but a huge amount of work went into matching the friction and hysteresis characteristics of a conventional throttle linkage, smooth and friction-free operation is actually bad because the driver finds it fatiguing and it's difficult to hold a constant steady state throttle position.

it was brutally expensive compared to a conventional system but on a s-class that wasn't such a big deal. the benefits were that cruise control was basically "free" compared to the vacuum-based systems that would otherwise be used, traction control was much simpler to integrate, and throttle cable routing issues were eliminated.

edit: i just looked at the article mentioned in the OP, i see it discusses the whole friction issue. very interesting, at least to a guy who used to think about such things.

Vincent Keene · **Posted:** Wed Feb 03, 2010 2:26 pm

Jason Tower wrote:

the mercedes s-class (w220 i think) was the first mass produced car to use throttle by wire, i worked for the company that made the pedal assembly. spent a fair amount of time at the facility in werne, germany where it was assembled as the company wanted to have the ability to sell it domestically and we'd have to manufacture it here. at the core it was a programmable angular position sensor, but since the pedal only pivots about 10 or 15 deg that didn't give enough sensitivity or resolution. so there was a complex arrangements of pivots, levers, teflon-coated cables, etc that amplified 15 deg of pedal movement into about 80 deg (iirc) of sensor movement. not only that but a huge amount of work went into matching the friction and hysteresis characteristics of a conventional throttle linkage, smooth and friction-free operation is actually bad because the driver finds it fatiguing and it's difficult to hold a constant steady state throttle position.

I knew it, there was a German behind it! If you want to make something simple complicated, ask a German how to build it.

clinehall · **Posted:** Wed Feb 03, 2010 4:58 pm

Vincent Keene wrote:

Jason Tower wrote:

the mercedes s-class (w220 i think) was the first mass produced car to use throttle by wire, i worked for the company that made the pedal assembly. spent a fair amount of time at the facility in werne, germany where it was assembled as the company wanted to have the ability to sell it domestically and we'd have to manufacture it here. at the core it was a programmable angular position sensor, but since the pedal only pivots about 10 or 15 deg that didn't give enough sensitivity or resolution. so there was a complex arrangements of pivots, levers, teflon-coated cables, etc that amplified 15 deg of pedal movement into about 80 deg (iirc) of sensor movement. not only that but a huge amount of work went into matching the friction and hysteresis characteristics of a conventional throttle linkage, smooth and friction-free operation is actually bad because the driver finds it fatiguing and it's difficult to hold a constant steady state throttle position.

I knew it, there was a German behind it! If you want to make something simple complicated, ask a German how to build it.

VK loves him some german engineering!

Patrice Bousquet · **Posted:** Thu Feb 04, 2010 10:03 am

Working for a German company I must say that VK is right, I look at component and wonder why they make it so complicated, but they are nice piece of engineering.
But sometime they have some simple design that work really good, sometime. The Swede are quite good too for making complicated component. We have a piece of equipment design and made in Sweden and that one beat the German hand's down.

Richard Casto · **Posted:** Thu Feb 04, 2010 5:13 pm

Well done article. It actually surprises me that the mainstream media has not looked into this at or near this level of depth. Especially considering how much it has been in the news.

My take away from the article is that they the DBW pedal assembly needs to be of generally better design and quality. I for one am not thrilled by how flimsy the entire assembly looks to be. Of course this is just 1/3rd of the entire system. You have the software and then the throttle body actuator. You don't want the software to have problems (but they probably are better tested than the mechanical parts) and you don't want the actuator to fail and be stuck at full throttle.

To VKs comments, DBW can give you better economy and (maybe) better performance as well. An example is that just because you give it full throttle as quickly as you can, you may actually get better economy or performance if how the throttle opens/closes is not tied directly to the pedal. I think that some recent hybrids have a mode that will softens throttle input so that it can result in economical acceleration. In the 2010 Honda Insight, it is called the "ECON" mode and you can turn it on/off.

Chuck Branscomb · **Posted:** Thu Feb 04, 2010 5:29 pm

DBW throttle is required for modern traction and stability control systems too. It is also heavily programmed in some instances, especially in cars with automatic transmissions, to control emissions under transient conditions apparently (sometimes resulting in some ugly response characteristics in some car brands/models).

Sean O'Connell · **Posted:** Thu Feb 04, 2010 8:19 pm

its not a very complicated system, basically there are 2 or 3 potentiometers in the pedal assembly and another one on the t-body. the computer must receive the same signals from all potentiometers or it will go into failsafe mode and the car wont move. from what i've heard about the toyota issue is that the pedals are not returning to the 0% position.

for those of you who say why complicate stuff, its going to kill us all, i cant trust it bla bla bla bull s!@t. airplanes have been using the same technology in "fly by wire" for probably as long as i have been alive its really not that big of a deal any more but people are making it out to be.

Jason Mauldin · **Posted:** Thu Feb 04, 2010 8:29 pm

Airplanes have redundant systems and engineers that are trained to produce failsafe products.

That article is written by a blogger doing an engineering analysis. I wouldn't put too much credit into his preconceived evaluation.

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

I've seen several references to "fail safes" and the "lack" of them on the Toyotas. Problem is, to the car's computer this fail mode just looks like someone having a good time -- WOT for extended periods of time. Short of putting some kind of pressure sensor on the pedal, I can't conceive of a fail-safe that could intervene.

Except of course a "maximum WOT duration" limit. Oh joy, a car that shuts down if you're into the gas for too long. I wonder how long it will be until cars can't be hurtled down the straight at your local race track....

The greenies in Washington will probably decide this is a good way to reduce Global Warming too and mandate it via the EPA

Donnie Barnes · **Posted:** Fri Feb 05, 2010 3:55 am

MikeWhitney wrote:

I've seen several references to "fail safes" and the "lack" of them on the Toyotas. Problem is, to the car's computer this fail mode just looks like someone having a good time -- WOT for extended periods of time. Short of putting some kind of pressure sensor on the pedal, I can't conceive of a fail-safe that could intervene.

Except of course a "maximum WOT duration" limit. Oh joy, a car that shuts down if you're into the gas for too long. I wonder how long it will be until cars can't be hurtled down the straight at your local race track....

The greenies in Washington will probably decide this is a good way to reduce Global Warming too and mandate it via the EPA

Porsche and some other manufacturers already have the perfect fail-safe mode for this...they cut ignition when you press the brake very much while lots of throttle is input. Left foot brakers hate it, but it's effective for this very "problem." It can also be aftermarket tuned out on Porsches, anyway.

--Donnie

Jason Mauldin · **Posted:** Fri Feb 05, 2010 7:55 am

MikeWhitney wrote:

I've seen several references to "fail safes" and the "lack" of them on the Toyotas. Problem is, to the car's computer this fail mode just looks like someone having a good time -- WOT for extended periods of time. Short of putting some kind of pressure sensor on the pedal, I can't conceive of a fail-safe that could intervene.

If the peddle was "stuck", I would think that the signal going to the ECU would also look stuck? I can't imagine a human holding a perfectly constant signal regardless of how good of a driver they are. Other than holding it WOT.

But I agree with you, the easy way out is to just have the brake over-ride the throttle, which is likely to be the route that Toyota takes. Fortunately, Toyota doesn't currently make a car that's worth driving on track.

Your idea of a pressure sensor on the throttle isn't half bad. For that matter, couldn't you just replace the pedal with a pressure sensor? :wink:

DickRasmussen · **Posted:** Fri Feb 05, 2010 9:14 am

I briefly owned a replacement carb for a 1960 Studebaker Lark 6 (my first car :cry:

) that was spring loaded wide open throttle. Even 40 years ago that was stupid. :twisted:

I immediately returned the carb and got one that was spring loaded closed throttle.

DickRasmussen · **Posted:** Fri Feb 05, 2010 9:21 am

MikeWhitney wrote:

The greenies in Washington will probably decide this is a good way to reduce Global Warming too and mandate it via the EPA

Probably not. At least half of the Prius drivers I see treat the speed limit as something they can ignore by a wide margin . . . either that or they have stuck throttles. :lol:

I'm impressed by their "off the line" acceleration in traffic. Are they really that quick or do the drivers just mat the throttle at every opportunity? I'm not saying they are actually "fast", just they typically don't poke like most other drivers/cars do in traffic.

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Article to explain why Toyota pedal fix may not be so good

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