Motorised throttle body

[Duk]

Do you think it is possible that at low rpm and high load you can actually get more power with partial throttle opening due to increased air velocity. Drive by wire may actually help in this case.

In my old Ford Laser turbo (KH), accelleration in 4th gear at about 60ks always felt better when you used less throttle than simply flooring it.

[RobertoX]

I'd say a lot of the reasoning behind is for fuel economy too.

Out of interest, does anybody know what sort of electirc motor is commonly used? (stepper or servo etc)

[wilbo666]

that's a pretty good point... controlling smoothness of the application on the throttle would surely help to protect drive line components too...

echo!

>Allows the ECU to implement gearbox saving features / driving enhancements (e.g. throttle blip on downshift)

Gearbox saving features -> also things like no full throttle at low RPM, and no sudden throttle changes (smoothed)

Do you think it is possible that at low rpm and high load you can actually get more power with partial throttle opening due to increased air velocity. Drive by wire may actually help in this case.

A bit like the old SU carbies or the twin throat carbs with vacuum secondaries that would only open up after you get a decent amount of vacuum.

Yeah possible...

I think they are usually a stepper motor, not 100% on that tho .



What you guys need to realise is that there isn't anything wrong with FBW in theory... it is just the implementation that maybe a bit lacking, and that is simply programming to a very large extent.

I'm sure lots of people hated EFI when it came out too (and still do ).

Cheers
Wilbo

[amichie]

In my old Ford Laser turbo (KH), accelleration in 4th gear at about 60ks always felt better when you used less throttle than simply flooring it.

I have noticed this also. There was a thread on the topic a few months back also.

Is it because EFI engines have such big throttle bodies compared to the old carby days.

[RobertoX]

Exactly, you could make your own map for the throttle if you wanted. Possiblly even do something about the lag with some electronic trickery?

[Moppitt]

What you guys need to realise is that there isn't anything wrong with FBW in theory... it is just the implementation that maybe a bit lacking, and that is simply programming to a very large extent.

I'm sure lots of people hated EFI when it came out too (and still do ).

Cheers
Wilbo

Bingo. We are seeing the same thing with stability control and run-flat tyres at the moment. A new technology that is initially a pretty blunt instrument, ie, run-flats ruined the ride, stability control activated early and heavily. With time and more development these technologies have become well implemented. The same goes for FBW. To see how quickly fbw can respond, jump in an e46 or later m3 (i'm sure there are others, just I know m3's). ITB's and FBW gives you the most responsive engine I have ever driven.

[wa5]

M3 isnt really an every day example though.

[Moppitt]

That is very good point, however that is a demonstration that the system can work well from both a drivability and manufacturers point of view. Now we all just need the manufacturers of everyday cars to start dbw properly.

[MWP]

ITB's and FBW gives you the most responsive engine I have ever driven.

By definition FBW cannot be any more responsive than cable, unless its driven by a computer that can preempt your actions.

FBW will never be fast in everyday cars... there is just no need for it, and it is more expensive to produce.
Fast FBW throttles will only ever happen on "sporty" cars.

[Mos]

3. Removes a mechanical wear point from the cable

Not necessarily. The earlier toyota setups still ran a throttle cable to a throttle position sensor mounted on the same shaft as the throttle plate - this allowed a backup mode in the event of failure.
In the later toyotas they removed the cable and used an APS (accelerator position sensor) on the pedal itself - probably proving the reliability of the earlier setup.

On OEM setups its a direct drive in comparison to the driver's input. The only other way it is manipulated is by TCS.

Not necessarily either. When manipulated by hand, the toyota 1G setup does appear to be directly coupled, however when changing gears in an auto it backs off the throttle resulting in a perfectly smooth shift. Turning on the snow feature reduces its responsiveness also.
I would imagine that in the LS400 it won't respond linearly to a stomp on the throttle from standstill.

I have yet to actually drive the 1UZ FBW throttle using the 1G ECU but in testing it responds linearly and instantly.

FWIW some turbo Audi setups interpreted the pedal input as a "torque demand", initially opening the throttle a lot, then backing it off as torque increased from boost. Highly non-linear, but apparently "better" as torque delivery was linear. (Don't ask me to find the literature though.. was ages ago).

Out of interest, does anybody know what sort of electirc motor is commonly used? (stepper or servo etc)

On the 1G-FE (IS200) and 1UZ-FE (97-00 LS400) they are DC motors with twin position sensors on each of the pedal and the throttle plate, and a clutch. The DC motors are similar in size to a power window motor and let me tell you there is no shortage of torque - it would take some experimentation to deduce if the motor could keep up with someone's foot but no amount of hand actuation could show up any lag.
The motor is controlled by PWM, pushing against the return springs, however on a sharp decel is does change polarity and the motor current helps close the throttle. At a steady state open position the motor is fed some current but the duty cycle is very low. Even full throttle is still a relatively low duty cycle, which provides a lot of headroom if extra current/speed is needed on movements. I'm trying to remember if sharp opening transitions went to 100% duty or not...

On the 1GZ-FE they are stepper motors (almost identical to an earlier traction control setup) but I'm not sure if the feedback is dual or single.

By definition FBW cannot be any more responsive than cable

Well, it could depend on how much the throttle cable stretches

With time and more development these technologies have become well implemented.

And consequently more accepted. The same thing happened when hydraulic brakes were introduced - people "protested" because removal of a mechanical link between their brake pedal and brakes left them feeling insecure.

Mos.

[madmont]

Here is what is on my 1JZGE motor from a 2001 Crown
The throttle cable pulls on the mechanism and when it gets to a little over half way the butterfly starts to open. When the throttle cable has reached the limit of its pull the butterfly is about half open. The rest is controlled by the computer.

[Mos]

Here is what is on my 1JZGE motor from a 2001 Crown
The throttle cable pulls on the mechanism and when it gets to a little over half way the butterfly starts to open. When the throttle cable has reached the limit of its pull the butterfly is about half open.

This is the backup feature. It's inactive during normal operation (by means of it being present only in the last 30% (or so) of the throttle cable travel).

The rest is controlled by the computer.

Not quite (If I'm understanding what you're saying). The computer controls *ALL* of the movement, unless there's a malfunction, in which case the backup feature happens.

You either get normal operation, or backup, not both.

Mos.

[87lux]

FBW is also designed to eliminate the need for a stepper motor that your older throttle bodies had. the cable designs used a small idle bypass tube to allow the idle to be increased and decreased but over time the small orifice would block up and fail to work. Now with FBW the throttle can be adjusted by the computer as engine load changes. Its not necessarily an easy system to use though as a base setting needs to be carried out every time you clean the TB and usually needs to be done so with a diagnostic tester.

[mrshin]

The idea itself is great, it's just that some examples of it are not so good - manual V6 Commodores and Rodeos are examples. They use horrendously slow throttle response, and worse still, take even longer closing the throttle, for emissions etc. reasons.

It is a cost effective way to include cruise control, stability control, traction control, idle speed control, and various torque limiting functions. If you don't like it, too bad, it ain't going away any time soon!

[thechuckster]

fwiw: wilbo's new 2JZGTE vvti has FBW throttle - fairly sensible packaging and obviously allows them to combine TCCS, cruise, throttle into one butterfly.