In Take/Throttle Plates/VAG Passive Throttle

InTake/ThrottlePlates/VAGPassiveThrottle (2021-10-29 22:27:45)

Overview

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

Attempt in 2021 to properly support this throttle

An idea for an adapter that utilizes a dual inverting gate driver and motor control IC to drive the throttle motor for idle. The mux to select between the high and low tps may not be required at all.

One critical element though, is we need to be able to assign an input to an idle switch function and instead of using TPS % for "idle" mode, we need to use the state of the idle switch input. Using some of the below ideas to use the idle switch to rail the TPS signal to 5V (closed on this throttle) caused oscillations of the idle switch at low loads which made the accel enrich significantly overfuel the engine. I even added a large capacitor filter and it helped slow the oscillations, but they were still there and the accel enrich was still a problem. Very willing to share circuit that doesn't work if desired.

Can this be implemented relatively easily? Possibly with a custom firmware to test it (MembersPage/JasonRussell has bench test setup, and customer car arriving 1 Nov 2021 which could test)

The VAG Passive Throttle listed on this page IS NOT DBW.

It is only electronic idle motor to throttle plate, the actual full opening of the throttle plate is cable operated

I was thinking about this throttle: what makes it special that prevents using either the IAC-PWM or (since the IAC can also effect the ETC target) ETC code to drive this throttle...

If the actuator is "higher PWM percentage" => bigger opening
- than only a bridge-output is needed, and the IAC-PWM can drive it
- could also be driven through the IAC => ETC target => ETC output but much more settings to get right, with apparently no advantage in this case
if the actuator is "integrating type" (CONFIRM HERE IF YOU KNOW THAT IS THE CASE) , that is (in some way similar to the stepper):
- it keeps it's position when unpowered
- moves up or down for + or - voltage (what is approximate speed ?)
- then indeed the IAC code needs some mods to drive it (either derived from the PWM code or from the stepper code)
- is there a feedback for the actuator ? (or only the TPS signal that is also effected by the driver's foot)
  - YES there is feedback for the Idle Circuit, 0-5v, all of that info is below ***
    - The main problem with PWM is, I can NOT control the throttle plate when partially open, it is very "weak". I can pin it open or closed easily, but part way, no. AND I have to use 20 to 10 HZ just to do that. If I select 150 HZ - there is almost no opening at all. KevinBlack ****

Bridge-output is needed in any case so request "H-bridge for VAGpassivethrottle" in the order comment.

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?)
  - YES it will open and is strongly held open with 14v ***
  - 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