Subpage of InTake/ThrottlePlates
Overview
This is a DBC (Drive by Cable) VAG throttle body used on VAG models, generally 1996 to early 1999.
Firmware implementation notes
ETC (electronic throttle) is implemented in VEMS v3 fw since 1.2.14
- including the PPS1 / PPS2 TPS / TPS2 sensors (so it consumes +3 analog inputs, besides the normal TPS signal)
- and safety relay output (safety relay is part of the system, cuts throttle power if sensor/mismatch or TPS > target).
- 1.2.15 (or newer) fw recommended ( GenBoard/UnderDevelopment/FirmwareChanges )
The PWM-ing frequency is actually 488 Hz, currently unconfigurable (usual recommendation is 450-550 Hz and throttle gets warm at low freq especially under 100 Hz).
- Since hardware-PWM ("OC0") is used, injector-PWM-ing cannot be used simultaneously (use high-Z injectors, or series resistors if low-Z is unavoidable).
- We've tested all ETC functions on actual throttle (VAG and Citroen throttles are very similar, BMW has only 1.3 Ohm resistance and therefore higher current and the 5A-chip is just unsuitable),
- and testing on real engine (Emil will report results very soon now). Emil tuned PID in the lab, and throttle-response was surprisingly good (fast, and very little overshoot).
When ordering assembled ECU, it is important to write Electronic Throttle output stage-box" in the order comment.
- Currently H-bridge is implemented with TO220 FETs (and protection diodes of course) clamped inside a seperate Aluminum box
- similar as used for [blue LCD] so it gets appropriate cooling with no compromise.
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)
Diagrams
![[DBC circuit diagram]](http://vagner.jeje.je/bilder/albums/album113/TB_Diagram.jpg){kind=link}
Pictures:
Outside
Inside
![[3]](http://vagner.jeje.je/bilder/albums/album113/TB_01.jpg){kind=link}
![[4]](http://vagner.jeje.je/bilder/albums/album113/TB_02.jpg){kind=link}
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.
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
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)
- 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
(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
- VDO unit. Throttle diam 45mm
- other suppliers ?
- 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