How are by-wire throttles controlled??

[MacroP]

Hilux 3.0 Litre NA(5L-E) and turbo Diesel (1KZ-TE), have an electronic throttle setup too if you're looking around for bits to play with. These are a Pot and stepper motor(sprung closed) setup from what I can tell. The servo setup looks like the old toyota traction control throttle setup found on 1UZ's(this is sprung open) and others. Thats their exact reason for this electronic setup now - no need for seperate servos for traction control and cruise control. All in one setup.

[slide86]

Mate crap, you have never driven one have you? or know anything about it?
If the 540 BMW i have sitting at home did the claimed 5.2 or 0-100 that would mean they could take a secound of that time using a cable and save themselves a tens of millions of dollars!
Stop learning of web sites or bad ones!lol

p.s a few seconds would make the 540 do the 0-100 in 2.2 seconds with a cable! i want one of those 540's!

errr. yeah nevre driven one.......except the hundreds of VZ and VE commodores and astras and vectras that i drive everyday. thats my experience with them and all the customer complaints we have regarding slow pedal response.

so its not entirely crap. sorry to have a perspective on it. "a few seconds" was an overkill statement

[kingmick]

I know, just taking the piss when i can. i new you didnt really think it was a few seconds!
but they do lack a bit of feel!

[Mos]

The Lexus (toyota) electronic throttles, as far as I can tell (by observation and toyota literature - no direct testing yet), are a DC motor with an electronically operated clutch, in a servo loop with a TPS on the throttle plate.
An additional APS (Accelerator Position Sensor) is rotated by the throttle cable, which comes from the pedal and attaches to the throttle body in a conventional fashion (in the throttle assemblies that I have seen).

On the IS200 both the APS and TPS appear to be identical electrically, although having different shaft attachments, both have two pots internally (there is no idle switch unlike conventional TPS') and the four signals are fed to VTA, VTA2, VPA, VPA2 pins on the ECU. With Vcc and E2 the APS and TPS have 4 pins each.

On the LS400 the APS is much larger and incorporates the cam holding the throttle cable.

The DC motor and clutch are operated through M+, M-, CL+, CL- pins by the ECU. The M+ and M- conductors are shielded through GE1 which appears to be a dedicated ground. The motor/clutch unit has 4 wires running to it - the shield does not extend to the connector.

There was a rumour that there is a failsafe mechanism that will still open the throttle mechanically using the cable if the electronics fail (at a small but useable angle), however I haven't been able to confirm that.

While not having driven the 540, the IS200 system is far from ideal with virtually any spirited IS200 driver attesting to lack of response. On manual models some experience revs increasing before they drop on gear changes, but that could be driving style as it wasn't my experience.

If anyone is not convinced there's a delay on them, all you need to do is fast multiple on/off throttle inputs in quick succession. The engine will buck with noticeable delay unlike that of a cable operated throttle. I'm invisaging this will really suck on a racetrack...

Draven - I'm intruiged about your one - I'd love to compare it as I can't see how it can be at least as good .. There's simply no way it can be more responsive than a cable

In terms of opening time, the motor will have a certain maximum speed at which it can open the throttle. Whilst not having tested it, I'd say it's extremely unlikely this speed will be faster than what someone can do with their foot.

JMO. Thoughts?

Mos.

[S.W.A.M.I.]

There was a rumour that there is a failsafe mechanism that will still open the throttle mechanically using the cable if the electronics fail (at a small but useable angle), however I haven't been able to confirm that.

this is correct.....testest this on an altezza. You only get about 30% throttle

The delay & poor throttle response seems more connected to how the stock ecu is programmed. An aftermarket ecu solved that problem

[Draven]

To be fair, it could just be the tune of the microtech that makes it (the 1j) a bit less responsive

[Hen]

Actually, I'm starting to think that using a traction control throttle body may be a good idea. Being sprung open rather than to a part-open failsafe position could make it easier to control. It is not going to be used as a normal throttle, so precise positioning and response time aren't super important.

Any further info on the type of control used is appreciated. As are opportunities to prod and probe your throttle with a CRO.

Hen