Throttle Controllers

[@rt]

Hi Guys
I have a theory that throttle controllers such as iDrive have to be a big fat scam.

Modern cars feature fly by wire, and their accelerator pedals contain a spring, and a sensor that is just a variable resistor.
These boxes are supplied with power, and interface between the accelerator (or throttle position sensor), and the plug that normally plugs straight into the throttle position sensor.

So how can this box claim to reduce “throttle lag” or do anything at all that can’t be reproduced by different pressure of the foot on the pedal?
Anything I’m not considering here?

I understand that this thing could, and obviously does indeed remap the resistance curve normally presented by the TPS.... but the claims of these things seem to imply further than that.

[james_s]

Never heard of them, but it sounds like it does exactly that, remap the curve to create a feeling of more power. Back in the carburetor days it was common for gearheads to mess with the linkage to make the throttle open more aggressively, it made the car feel really punchy off the line but it was only an illusion, obviously it didn't actually allow the engine to develop any more power, it just made the throttle more twitchy.

[@rt]

Never heard of them, but it sounds like it does exactly that, remap the curve to create a feeling of more power. Back in the carburetor days it was common for gearheads to mess with the linkage to make the throttle open more aggressively, it made the car feel really punchy off the line but it was only an illusion, obviously it didn't actually allow the engine to develop any more power, it just made the throttle more twitchy.

I’m not actually sure if this kind of link is allowed, but I’m obviously not advocating it. They aren’t cheap either.
https://www.autobarn.com.au/ab/Autobarn-Category/Brands/Evc/THROTTLE-CONTROLLER-3-MODES-EVC652/p/PE59007?gclid=Cj0KCQjwmIuDBhDXARIsAFITC_5mzOEglWyzv6h_zOCfcEyD1sqtw9UMXqTbkapIJravqbSUr84P0S0aAkyTEALw_wcB

I figure most vehicles would work this way nowadays, and mine is one of those. I’m in Facebook groups pertinent to my vehicle, and these things come up often,
as do adds for the things in my feed.
There are videos about them with a pair of identical cars racing each other etc.. or the same car with the device enabled/disabled.
This is where I think things are going way too far. many actual users swear by them.

[Alti]

Hi Guys
I have a theory that throttle controllers such as iDrive have to be a big fat scam.

There are people that deliberately put some controller in between acceleration pedal and throttle body. 

[Gregg]

What we really need is a controller that shuts down the throttle whenever the brake pedal has any pressure on it....to get rid of the idiots that can't keep their left foot off the brake and their brake lights are always on.   

[amyk]

So how can this box claim to reduce “throttle lag” or do anything at all that can’t be reproduced by different pressure of the foot on the pedal?
Anything I’m not considering here?

You still have to overcome the (small, but I guess if you're racing, every tiny bit counts...) inertia of the pedal, so if it changes the curve such that 1% throttle becomes 10%, it will feel more responsive.

That said, I suspect drive-by-wire is more for reducing emissions than anything else - and of the cars that I've tried which have it, there is a noticeable lag between punching the pedal and the engine responding. This is especially noticeable with a diesel. They deliberately limit the acceleration of the engine below the smoke-point.

[Mazo]

Drive by wire has a gazillion advantages.Never heard of this product,but a glance at the first page of their site makes me think they are semi-legit(no claims of higher power?).Indeed setting a higher "target" with this device or just by simply mashing the throttle might result in reduced lag.A lot of ECU's(or atleast that I know of) deliberately add lag(even pushing the ignition advance on gasoline engines) when there is a step change on the throttle.Why?To prevent the jerk in the drivetrain that follows when you do that on a big engine especially.
You are right though,nothing you can't reproduce without that thingy.

[james_s]

What advantages? I don't doubt that it has some, but I have never really had any complaints about the old fashioned throttle cable in my car. I'm generally a fan of simple, direct mechanical links like that vs more electrical connections and sensors. Thinking about problems I've fixed in various cars, connections and sensors are some of the most common non-consummables I've had to repair or replace. 

[SilverSolder]

What we really need is a controller that shuts down the throttle whenever the brake pedal has any pressure on it....to get rid of the idiots that can't keep their left foot off the brake and their brake lights are always on.   

How are you supposed to do a brake stand with Dad's car with that kind of technology?? 

[SilverSolder]

Applications engineers that work on the engine management systems of modern cars spend a LOT of time getting the "feel" of the accelerator "just so".  This is mostly done by testing on the track and on the road...  after all, only a human driver can tell you how the accelerator "feels".

And the "feel" that they aim for will be different depending on the target market.   The electronic throttle in a Mustang GT will not have the same goals for throttle response as a Toyota Camry! 

[@rt]

This is the wall of text I see most often on one of the Facebook adds.
I have a 4WD, and look at 4WD stuff, so that’s probably why it keeps being shown to me.


.....

WHAT IS THROTTLE LAG?
Well first we have to take you back to the good old days of throttle cables and carburetors. In the old days, the gas pedal was directly connected to the engines throttle plate by a cable, and any lack of response from the engine could be attributed to a couple of things. Either the cable has stretched enough to create slack and, consequently, a delay in pedal response, or the engine was out of tune which meant it was not making as much power as it should've been. Easy fix, buy a new throttle cable for $20 and get your carby tuned. Nowadays though it's not that simple.
Let's look at how electronic throttles work. Instead of a cable, the pedal is now connected to what essentially are potentiometers. They generate a certain amount of voltage which the ECU reads and equates to throttle angle openings. They first of all measure how far your foot travels when you push the pedal to a certain point as well as how fast you pushed the pedal to reach that point. The ECU then sends a signal to the butterfly position sensor which controls the opening rate of your butterfly on the throttle body, and opens it up by the amount programmed into the ECU for a given voltage generated at the pedal. There is also a feedback sensor on the throttle body which informs the ECU that the throttle butterfly is doing what it is supposed to (i.e. opening the throttle up to the angle dictated by the ECU).
Now, like with most electronic control systems, there is redundancy built into drive by wire systems. Instead of just one demand sensor at the pedal, there are two. Same goes with the feedback sensor at the throttle body. This is to avoid loss of control should one fail. The complex nature of this system with its variety of potentiometers, computers, sensors and management systems is what results in a noticeable delay when you first hit the pedal, known as throttle lag or dead zone. No matter how hard or fast you stomp on your accelerator there is no overcoming this delay, it is an inherent electrical delay that physical input cannot overcome.
Why the change from a physical cable to invisible electrons telling your engine what you want to do? Well a few reasons, first of all the electronic throttle system is a lot lighter, reducing weight in modern cars, also they are far easier to service and tune, simply hook up a computer and let it do the work for you. It is also worth mentioning the impact of emissions control in regard to switching to electronic throttle systems, using electronics allows for much more precise control of the throttle opening compared to a cable that stretches over time. It also allows the throttle response to be programmed in by the manufacturers. Yup, that's right. The throttle response on drive-by-wire control systems can be programmed. This is where the EVC Throttle Controller comes in.
The EVC Throttle Controller modifies the voltage signal from the drive-by-wire pedal assembly to allow you to tune the response from your accelerator pedal and greatly reduce the dead zone from when you initially depress the pedal, commonly referred to as throttle lag. The EVC does this by providing new points of reference for the vehicle's throttle mapping. It is still working within the standard parameters; however, it introduces a far sharper throttle curve. It is also actuating the throttle earlier in the pedal stroke, introducing petrol and air into your engine earlier in the throttle stroke thus improving throttle response and performance.
The real benefit of the EVC though is its ability to give you complete control over the throttle response of your vehicle, if your vehicle is too responsive you can dampen its response to a level that suits your driving style. You can also change the EVC's settings and modes on the fly so if you are driving along the freeway and need to overtake someone, crank the iDRIVE up a few levels to deliver better throttle response, or if you are towing a trailer/ caravan you can bump up the throttle settings to account for the extra added weight. Don't just take our word for it though, every EVC comes with a 30-day money back guarantee so you can try the EVC and see its effectiveness for yourself.
Check it out for yourself:

[AndyC_772]

This:

The complex nature of this system with its variety of potentiometers, computers, sensors and management systems is what results in a noticeable delay when you first hit the pedal, known as throttle lag or dead zone.

...is simply untrue.

If there's a lag when you increase pressure on the accelerator, it's because the car's ECU has been programmed to keep the engine running closed-loop whenever possible. Closed-loop means the fuel/air ratio is controlled, making use of the lambda sensor, to maintain the ideal mix for complete combustion.

Small increases in power can be accommodated this way, but a rapid or major increase in power output requires running the engine in open-loop mode. The amount of fuel is increased, the fuel/air ratio increases, the engine produces more power, and hydrocarbon emissions go up. Thus, for emissions reasons, the ECU is programmed to avoid doing this unless it's definitely required.

Any resulting delay in throttle response is not due to "the complex nature of this system"; it's a side effect of this deliberate feature of the ECU.

That doesn't mean a delay when you actually do call for more power is desirable, though.

A device that essentially remaps the position of the throttle pedal can't overcome pure delays that exist in the ECU's programming, but it might mean that a relatively small increase in pedal travel is enough to exceed a programmed threshold for what constitutes a 'small' throttle opening vs a 'large' one.

It's not doing anything you couldn't do just by pressing harder on the pedal, but if it means the overall system response matches the driver's preference or expectation, it's no 'worse' than having a seat that slides forwards and backwards to make the reach to the pedals more comfortable.

[SilverSolder]

There isn't anything wrong with re-tuning the "feel" of the throttle pedal, it is no different than customizing anything else on your ride...

I sometimes drive a friend's muscle car, which uses an electronically controlled throttle.  Let's just say that throttle response is not as much of an issue as making the rear tires last for longer than 20 miles or so! 

[David Hess]

Modern cars feature fly by wire, and their accelerator pedals contain a spring, and a sensor that is just a variable resistor.

The ones I have studied use a reversed redundant pair of hall-effect sensors and not any sort of resistive element.  Personally I think this is still reckless because of additional failure modes compared to reversed redundant pair of LVDTs or RVDTs with AC excitation and synchronous detection.

[james_s]

Applications engineers that work on the engine management systems of modern cars spend a LOT of time getting the "feel" of the accelerator "just so".  This is mostly done by testing on the track and on the road...  after all, only a human driver can tell you how the accelerator "feels".

And the "feel" that they aim for will be different depending on the target market.   The electronic throttle in a Mustang GT will not have the same goals for throttle response as a Toyota Camry! 

They did that on old cars too. I remember discussing this a while back with a friend, he was talking about a car someone he knew had in the 80s that had a really aggressively tuned throttle, it was done so that if you just touched the gas from a stop it would feel powerful, puttering around town it gave that feeling of "whoa, this thing really wants to go!" but then if you actually stomp on it, it would pretty much run out of steam. It was not a very powerful car, it was just tuned to create the illusion of being powerful.

[David Hess]

They did that on old cars too. I remember discussing this a while back with a friend, he was talking about a car someone he knew had in the 80s that had a really aggressively tuned throttle, it was done so that if you just touched the gas from a stop it would feel powerful, puttering around town it gave that feeling of "whoa, this thing really wants to go!" but then if you actually stomp on it, it would pretty much run out of steam. It was not a very powerful car, it was just tuned to create the illusion of being powerful.

I am not surprised they would do something like that.  They play that game with modern electronics also.  For example cell phone signal level bars have their dynamic range altered so that they are more likely to show maximum indicating a good connection even when it is poor.

Old enough cars had progressive carburetors so at least you could feel the additional resistance when the next set of butterfly valves opened.

[SilverSolder]

Many cars are tuned to feel powerful by applying a lot of throttle at the beginning of the pedal movement.   This is exactly what you don't want for fine control in snow or slippery conditions, of course...   

[hans]

Applications engineers that work on the engine management systems of modern cars spend a LOT of time getting the "feel" of the accelerator "just so".  This is mostly done by testing on the track and on the road...  after all, only a human driver can tell you how the accelerator "feels".

And the "feel" that they aim for will be different depending on the target market.   The electronic throttle in a Mustang GT will not have the same goals for throttle response as a Toyota Camry! 

And on high-end cars they do this mapping or tuning for both "sports" or "comfort" driving operation as well.

Technically speaking you could just measure the throttle position, scale it to 0 ... 1, and then apply a sqrt() (or any fractional power for that matter) function on it to incredibly make it more punchy at the low end of the curve. Likewise if you want to soften it, you could square (or any power between 1 and 2) the value to make it incredibly slow at the low end. In that regard, these after market devices are not rocket science. They are purely an illusion or perhaps even a driver aid for economical driving.

IMO: If there is one throttle curve that is 'correct' or "ideal"; then tune the output of the drivetrain (e.g. if you have hybrid systems) to deliver a certain torque demand. Then linearize the throttle position to the capabilities of the drivetrain, both in retardation as in acceleration. Depending on how you scale the capabilities, you could even make it independent of engine rpm, vehicle gear or vehicle speed (as that will naturally increase vehicle retardation). The upside is that torque is what you feel will push you back into your seat, so will be relevant in feedback to the driver. You could make that feeling very predictable without knowing what the drivetrain under the hood is doing. The downside is that at certain speeds the drivetrain is not able to always deliver that torque demand.
Or just buy an electric motor.. I believe those are typically quite linear and ideal

Anything that makes that ideal throttle response softer/harder is just market tailoring torwards comfort or sport packages.

They did that on old cars too. I remember discussing this a while back with a friend, he was talking about a car someone he knew had in the 80s that had a really aggressively tuned throttle, it was done so that if you just touched the gas from a stop it would feel powerful, puttering around town it gave that feeling of "whoa, this thing really wants to go!" but then if you actually stomp on it, it would pretty much run out of steam. It was not a very powerful car, it was just tuned to create the illusion of being powerful.

I am not surprised they would do something like that.  They play that game with modern electronics also.  For example cell phone signal level bars have their dynamic range altered so that they are more likely to show maximum indicating a good connection even when it is poor.

Old enough cars had progressive carburetors so at least you could feel the additional resistance when the next set of butterfly valves opened.

I recognize my Ford Fiesta in this. On the lower half of the RPM range, it's already pulling full torque with 1/3 or 1/4 throttle position. The rest of the pedal is dead. Doesn't do anything.

[SilverSolder]

[...]
IMO: If there is one throttle curve that is 'correct' or "ideal"; then tune the output of the drivetrain (e.g. if you have hybrid systems) to deliver a certain torque demand.
[...]

That is pretty much exactly how the throttle works in my hybrid Ford - which is extremely good in snow and ice because the torque can be controlled almost perfectly to the point just before spinning the wheels in all but the most extreme slippery conditions.  During snow storms, I have rescued a lot of stuck 4wd vehicles with this car, where the owners got a little overconfident! - my favourite comment from one guy, looking down at my wheels, "Are those summer tires?!?"  (yes, they were!)

[Sal Ammoniac]

That said, I suspect drive-by-wire is more for reducing emissions than anything else - and of the cars that I've tried which have it, there is a noticeable lag between punching the pedal and the engine responding. This is especially noticeable with a diesel. They deliberately limit the acceleration of the engine below the smoke-point.

I've never driven a diesel, so I have no experience with how drive-by-wire works in that scenario, but I can tell you that on an electric car like my Tesla, there is no noticeable lag at all between punching the pedal and the car responding. It's much better than my previous IC car, which did have some lag. Plus you can tune the response as well, including turning off "creep" so the car doesn't move with your foot off the pedal like IC cars with automatic transmissions do.

[amyk]

Electric vehicles don't have to worry about emissions, and motors can provide full torque at 0 RPM. I haven't touched a Tesla but have tried a trolleybus before, they have a surprisingly large amount of torque for such a huge vehicle and can accelerate ridiculously fast.

[tom66]

I drive a hybrid that has a 'sport' mode (GTE) and a normal hybrid mode.

The normal hybrid mode has deliberate lag applied to it - ie you put your foot down and it waits a bit before it selects the lower gear and accelerates up.  I think this is designed to improve fuel economy with twitchier drivers, but it's damn annoying if you actually know how to drive. 

I end up just switching it to 'sport' when I want the extra responsivity, then take it out of this mode when I don't.

Interestingly the adaptive cruise control is also more aggressive in 'sport' mode.  But, the output power is the same (204 PS/150kW) in all modes, so 'sport' is an illusion, provided you don't mind the slightly slower throttle map. 

[Circlotron]

One nice thing about drive by wire - adding a cruise control function is simply a bit of extra code in the ECU. Everything else is already there.

[james_s]

I don't know that it really makes much difference for that, even on older cars cruise control is not exactly complicated. Mine consists of a control box that gets a signal from the speedometer, switches on the brake and clutch pedals, a vacuum servo connected to the throttle spool and a little vacuum pump/solenoid valve. Drive by wire adds complexity over a throttle cable, being able to add cruise control at that point isn't really gaining anything.

[tom66]

Adaptive cruise control is quite clever though.  I've always wondered how my car knows exactly how much to brake and accelerate by, in stop-start traffic for instance it gets the braking to a stop and acceleration almost perfect.  It can get a bit rough if someone cuts in, then it brakes harder than usual but that's probably a safety system given the radar doesn't see the other car until they get past about 25% of my vehicle so it would end up braking later than an attentive driver.  And sometimes it rolls back very slightly on a hill before setting off, but only intermittently, like it's not quite sure how much acceleration to use.