In Take/Throttle Plates/VAG Passive Throttle

InTake/ThrottlePlates/VAGPassiveThrottle (2013-08-20 16:18:51)

Subpage of InTake/ThrottlePlates

Overview

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

How it works

Throttle is cable operated, but idle is controlled with gear motor.
Only throttle plate position at idle is controlled with gear motor.

The 1996-1999 VAG DBC throttle body contains:

Two potentiometers, one for idle position feedback and other for measuring cable operated throttle plate opening angle.
One "Idle Position" Switch (Open with ANY movement of the Throttle Cable)
A DC electric motor to adjust the angle of the throttle up to small amount for Idle Control. (Motor can also close throttle slightly more then "Rest Position").
Spring return to closed "Rest 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?)
  - TODO: Measure Current and Frequency (somewhere around 125 hz)

* Motor measures 4.0 Ohms at rest.

Diagrams

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See [DBC circuit diagram].

Pictures:

Outside

Inside

[3]

[4]

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

NEW Kevin Information / Control Development:

1) Idle Control Issues:

I have tried to use an Injector Output to PWM to control for this (with IN4007 Diode), 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".

* Does power source matter? (Ignition Power vs. Power Connected Directly to Flyback Circuit?)

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

(I can pin idle control to fully open or fully closed OK, but everything in between is bad).

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

OK, let's get started :)

2) Idle Switch Implementation (or temporary hack)

Need to develop way to use the Idle Switch to use Vems "Idle Control TPS Threshold" setting)
Without, this means that the TPS% moves when the IAC is active.

New Wish, please add "Accel Enrichment Trim" to Anytrim options, so I can disable (lower by 300%) the TPS enrichment when the (poorly controlled at 10-20HZ) throttle plate/tps is bouncing around. KevinBlack

Sensor Info

Two potentiometers, one for idle position feedback and other for measuring cable operated throttle plate opening angle.
- This TPS is "backwards" - Use smaller setting for "TPS100%", and larger setting for "TPS 0%".
One "Idle Position" Switch (Open with ANY movement of the Throttle Cable)
- Idle Position Switch is internally connected to Sensor Ground (Which, unfortunately, means 100% TPS seen by Vems - it would have been easy to use this otherwise)

Sensor Measurements (on Audi V6 unit)

Pins 5-7 (TPS and Sensor Ground)

1,455 ohms at Rest, 720 Ohms at WOT

Pins 8-7 (IAC-only TPS and Sensor Ground)

1,185 Ohms at Full Closed IAC (push throttle plate fully closed by hand).
1,140 Ohms at Rest.
920 Ohms at Fully Open IAC. (push throttle plate to end of gear travel)

* Motor measures 4.0 Ohms at rest.

Wishlist Summation:

1) Proper control of motor in both directions
2) Add "Idle Switch Input" in ecu firmware (Necessary to use Vems "Idle Control TPS Threshold" setting)
3) Have everything work without wire swapping, to suit Plug-and-Play installs.

Advanced: 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

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

* TODO - Figure out proper Testing Method.

* Motor measures 4.0 Ohms at rest.

* Reverse voltage does close throttle completely.

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 after hitting Vems TPS Threshold setting.

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.
  - Strong wish to make this work with no wiring/harness modifications (because of PlugAndPlay installs)

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

(OLD info, should update) 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

Audi PN 078-133-063AP

Pre-1996 VW TPS Info(Should be moved)

VW TPS part numbers:
- 2.0L 8v: 037 907 385 N/P/Q
- 2.0L 16v: 054 133 154 F
- G60: 037 907 385 D/M (and maybe H)

See also