In Take/Throttle Plates/VAG Passive Throttle

InTake/ThrottlePlates/VAGPassiveThrottle (2010-12-21 09:01:29)

Subpage of InTake/ThrottlePlates

Overview

This is a DBC (Drive by Cable) VAG throttle body used on VAG models, generally 1996 to early 1999.

These units use an electric motor for Idle Control only

How it works

The DBC throttle body contains

two position sensors (variable resistors)
one end switch and
a DC electric motor to adjust the angle of the throttle. Spring return to closed position
- Is this 12..14V and what max current? (are the 1.1A stepper driver channels able to drive it or not ?)
- Does it withstand 14V continuous drive even in the end-position ? (for how long?)

Inside

See [DBC circuit diagram].

Cropped%20Full%20Size%20AEB_TB_IAC_Labels.gif

Pictures:

Can Someone tell me if the connector is micro-power-timer or junior-power-timer (likely) size? (see ConnectorSelection or tycoelectronics.com if unsure about sizes, or just measure the pin dimensions, like "2.68 x 0.8mm"). I saw an apparently matching female 2x4 one-end-rounded connector housing on the front-cover of a tyco catalog (could not find the product inside though, except in 2x4 pin microtimer size - on http://www.tycoelectronics.com ).

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note that it has 2 speed-down gears inside, about 1/7 and 1/8 ratios (1/56 effectively).

Pictured throttle body is not fully motor driven.

Only throttle plate position at idle is controlled with gear motor.
Hence this is cable operated, but idle is controlled with gear motor.
Has two potentiometers, one for idle position feedback and other for measuring cable operated throttle plate opening angle.

NEW Kevin sent the following information:

It is for the VW/Audi cars made from 1996-1999. Drive by Cable.

It is a small electric motor and gear that turns a larger gear, that opens the actual throttle plate up to ~15%,

and

it can also actually close the throttle plate farther than it's resting position as well.

I have tried to use a PWM to control this, but the throttle plate movement is "weak".

For example, I can have it slightly open, and take my finger and physically move the plate, and it will not "self correct".

This translates to the engine speed fluctuates greatly, and proper control is impossible.

yes, because from the schematic it looks like +12V and -12V bidirectional drive is needed on the motor to move one direction or the other

This units operates OK at 100% open, and it will close to the resting position when the DC is 0%. But everything in between is bad.

(And I don't know how to close the plate from it's resting position to lower the idle from base)

Cropped%20Full%20Size%20AEB_TB_IAC_Labels.gif

Sensors

Finally, there is an "Idle Circuit" that I cannot use, because it is wired (internally) to make the TPS% go to "100%"

when connected.

This means that the TPS% moves when the IAC is active.

This TPS is also "backwards" - "TPS100% setting" is small, and the "TPS 0% setting" is large.
- This itself is not a problem

Wishlist summation:

Proper idle control
Add "idle switch input" in ecu firmware
- is this needed ? Did you try simply calibrating higher value for TPS-LOW than for TPS-high ?
the throttle-controller code would watch a 2nd analog input for throttle-command (I recommend TCS abbreviation, because throttle-pedal-sensor abbreviation would collide with throttle-position-sensor we already use)
- decision is needed for connections. In any case, for internal idle-threshold the throttle-command (pedal sensor, not the actual throttleplate position sensor) must be used, for safety
Have everything work without wire swapping, to suit Plug-and-Play installs.

Please measure current, and try to confirm that reverse driving voltage closes it (try to be careful, and use fuses).

Jorgen's comments :

There can be different versions of this throttle, but the ones I have seen worked fine.

This throttle has worked good before
- Q: (driven how ? simple PWM or with +12V / -12V signals ?)
- but there is a trick to it. As it turn the throttle itself it change the TPS angle, this means that as soon as the idle control is activated the TPS will change and the idle control will be turned off instantly.

There is an idle switch in the throttle, you need to use that to short the TPS signal to ground.

As this throttles TPS has the wrong polarity you need to connect it with the opposite polarity. This unfortunately make the idle switch short to 5v instead of 0v.
- So You need to use a small signal transistor (same NPN + 2 resistors as in the InputTrigger/WheelSpeed and AudiTrigger/CamHALLInverter ) to reverse the polarity of the signal.

Possible interference with TPS-acceleration enrichment

There will be a sudden jump in TPS voltage when the idle switch become inactive as the TPS signal go from 0v to the output of the TPS instantly. I have expected this to give a squirt of fuel through the acc enrich but I have not tuned any of these cars myself and the customers who did the tuning didn't notice a problem even if I asked them to look for the problem. I'm sure that we can come up with a workaround if it's needed.

But it would obviously be best if we could have an idle signal input on the ECU.

What would be the exact semantics ?
- If idle-signal input==active (normally active below 1.6V, or above 1.6V if inverted input is chosen) than we consider idle-mode (pretend that TPS < iac_tps_threshold) regardless of TPS voltage ?

Plan - steps

We need to find out

hardware requirements, like current consumption in both direction (when moving, and likely higher when stopped)
if the +-12V drive assumption is correct
voltage mapping of the analog feedback signals for min 8 points, and min 4 points around idle
implement firmware code for it
find/tune suitable PID parameters
write some vemstune help text for the new dialog

I'm pretty certain that Jorgen Karlsson is more knowledgeable than me, and he might confirm or deny some of our assumptions.

(OLD) Sources

VAG item number ?
- VDO unit. Throttle diam 45mm
  - 030 133 064 F
  - 408 237/130/004 I 3 33 99
other suppliers ?

Costs > 350 Euro. Anyone knows good sources ?

Audi V6 uses much larger (~70mm plate) size with same design

See also