This document is for the current software revision (1.12). For the earlier 1992-1994 only software version (1.0), see this user manual.

As the user, you interact with the TDS-1 using one button. The button is either pressed normally, or held down for a longer duration (approximately 2 seconds). The normal press is referred to in this document as a "short press", and the long press is referred to as a "long press". These are the only two ways that instructions are given to the TDS-1.

In normal operation, a short press serves as a "next" button, advancing to the next display mode in a circular fashion. In configuration mode, a short press moves to the next value or setting.

A long press enters and exits the display option select mode from normal mode. The TDS-1 will indicate that the button has been held long enough to qualify as a long press by displaying the BUtton screen.

In normal operation, you have a number of different informational screens to choose from, using the short button press to scroll among them. Each mode has a unique identification displayed on the bottom row of the display. Note that it is possible to disable modes that are not needed. This will be discussed later.

Instantaneous Manifold Pressure Mode

If the displayed value is above atmospheric (i.e. boost), the letter "B" will be displayed on the center line. This picture was taken when the engine was not running, hence zero PSI boost (or zero inches of mercury (inHg) vacuum, depending on your perspective).

Peak-hold Manifold Pressure Mode

The "B" for boost applies to this mode as well, with the addition that the "B" will flash when the peak boost value is being held. There are two manifold pressure modes ("U1" and "U2"). U2 is a peak hold mode which holds the highest reading over the last 5 seconds, and U1 is a direct display mode with no hold. Both modes average the MAP signal over a 20 millisecond period to obtain their readings. Optionally the U2 mode can be configured to display the signal from the radio head unit instead of vacuum readings.

Atmospheric mode

Atmospheric mode displays the current atmospheric reference pressure, in kilopascals. If the "A" is flashing, this indicates that the reference pressure was measured during this run cycle, using the procedure described below. If the "A" is not flashing, then this is the value stored the last time the pressure was read. Alternately, a "D" may be displayed to indicate the Default pressure value, or an E may be displayed if the atmospheric pressure measurement resulted in an implausible value.

Instantaneous IAT mode

There are two Intake Air Temperature (IAT) modes. The Instantaneous IAT mode averages the IAT reading over a period of approximately 330 milliseconds (1/3 second) and displays it directly.

Peak-hold IAT mode

The peak hold IAT mode averages IAT readings for only 20 milliseconds (1/50 second) and displays the highest reading read over the last 5 seconds. The peak value will tend to be slightly higher, even when the IAT is not changing. This is due to small amounts of noise on the IAT signal.

Voltmeter mode

Radio pass-through mode

The "RDO" screen is displayed for a few seconds when this mode is entered. If the Audi/Bose radio is turned on, after a few seconds its output will be shown. If the radio is off, or if no suitable radio is present, then the screen will be blanked.

Note that the radio mode is intended for cars with the Audi/Bose "Gamma CC" (narrow face) radio. For cars with aftermarket stereos or the later "Delta CC" (wide face) radio, the radio modes can be disabled in the System Configuration (see below).

On all model year cars, this mode can be used to "turn off" the TDS-1 if you desire.

The run-time configuration modes are entered via a long button press from the screen being configured. The screen indicator digit (e.g. the 1 in "U1", etc.) will flash while in run-time configuration mode. A long press will exit the configuration mode and return to normal mode.

Manifold pressure display units

In the manifold pressure modes, there are three options for display. The normal mode displays pressure in units of PSIG (Pounds per Square Inch Gauge) for boost and inHg (inches of mercury) for vacuum. There is an absolute pressure mode, which uses units of kilopascals. And finally there is the PSIG only mode, which displays boost in PSIG, but instead of displaying vacuum readings, it relays the radio display signal, or displays a blank screen if no radio signal is present.

MAP Units Select Mode

A long press from either "U1" or "U2" enters the MAP units select mode. A short press toggles between the two or three available display formats.

When configuring the MAP units, the "full scale" value is displayed in the selected format. The full scale value depends on the MAP sensor range selected, and the local atmospheric pressure. At sea level, a 3 bar map sensor has a range of 43.5 PSI absolute, or 28.8 PSIG. However, the "3 bar" sensors used have a transfer function such that full scale is actually approximately 3.3 bar, or 33 PSIG at sea level. The value displayed by the TDS-1 here is the PSIG reading assuming a maximum (5 volt) MAP signal input.

The above two screens were entered from Instantaneous MAP mode U1. The units configuration screen can be entered from Peak-hold MAP mode U2 as well.

The display format is configured for both U1 and U2 modes at the same time; the configuration can be done from either screen.

As above, units select screen entered from "U2".

This option is available from both "U1" and "U2" configuration screens, but it only applies to the U2 mode. When selected, the vacuum measurements are not displayed when in U2 (peak MAP) mode. Only the peak boost (in PSI) is displayed. When the manifold pressure is below the measured atmospheric pressure, the radio display is passed through from the radio to the cluster directly. If the radio is off, the display is blank.

In this mode, the autocheck display operates exactly as it does from the factory, except when the turbo is producing boost, in which case the peak boost pressure is displayed instead of a blank screen or the radio station. Note that the "U1" instantaneous pressure mode is unaffected by this setting, and will operate in normal PSI/inHg mode.

On cars without the Gamma CC radio (1995.5 models, etc.), this mode can be used to suppress the vacuum display, so that the TDS-1 only indicates peak boost. When the turbo is not producing boost, the display will remain off.

MAP Range Select Mode

This mode is entered via a long press in Atmospheric (U3) mode.

Short presses will increment the selected MAP range. The sequence is 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 2.0, and then 2.5 again.

The MAP range parameter determines how the TDS-1 converts the MAP signal from the ECU from a voltage into pressure. This depends on what kind of MAP transducer you have in your ECU. The Ur-S4/S6 came from the factory with a 2.5 bar sensor. If you have "chipped" your car, you may have a 3.0 bar sensor. If you have a VMAP, then you may be using it as a 2.8 or 2.9 bar sensor. Naturally, if you do not configure the MAP range on the TDS-1 correctly, then the reported pressure values will be incorrect.

When the MAP range is changed, the TDS-1 will revert to a default atmospheric pressure of one standard atmosphere. To measure the actual atmospheric pressure after changing the MAP sensor range, turn off the ignition key, wait a few seconds, and turn the ignition to "run" without starting the engine. After the "OK" screen disappears you should see the new atmospheric pressure reading.

IAT Temperature Units Select Mode

The IAT units selection screen is entered via a long press from either of the IAT modes (U4, U5).

A short press toggles between Fahrenheit and Celsius. A long press exits the selection screen.

Measured Atmospheric Pressure Display Mode

When the "A" is flashing, this indicates that the atmospheric reference pressure was read during this power cycle. If the "A" is solid, then the pressure reading was loaded from non-volatile memory.

The TDS-1 has some less-frequently-changed options which are set from a special system configuration screen. This screen is entered by holding down the TDS-1 button before turning the ignition on, and continuing to hold it it until the four digit configuration value or the "BU"tton indicator appears. This takes a few seconds, and normally appears right after the "OK" display clears.

Note: The button should be released as soon as the TDS-1 display appears. If the button is held down too long, the TDS-1 will clear all of its nonvolatile memory. This will erase all saved settings.

The system configuration is entered as a 4 digit number which encodes the various options. The option codes are described on this page. To enter the value, the four digits are changed one by one, from left to right. Long presses advance to the next digit, and short presses increment the currently flashing digit.

Default Setting

A short press will increment the selected digit. A long press will move to the next digit.

A long press will exit system configuration mode when the rightmost digit is selected.

Option Codes

Click this link for the option codes

Splash

When exiting configuration mode, the "TDS.1" screen will display briefly on 1992-1994 cars. On later cars, this screen is a sequence of punctuation characters. (Audi changed the font for 1995!)

In order to calculate gauge pressure and vacuum readings, the TDS-1 must know the local atmospheric pressure. This value can be measured by turning the ignition to ON, from OFF, not cranking the engine, and waiting approximately 5 seconds. The TDS-1 will read the pressure of the Manifold Absolute Pressure (MAP) sensor in the ECU and use that as a reference point for relative measurements.

The TDS-1 can not measure atmospheric pressure if the engine is running or being started. The TDS-1 monitors the car's voltage when it first receives power. If the car's voltage does not exceed approximately 12.8 volts, and is not less than approximately 11.3 volts, the TDS-1 will measure atmospheric pressure. Otherwise, the atmospheric pressure reference value is loaded from memory.

There is an option in the System Configuration which enables an automatic radio display mode. In this mode, the TDS-1 functions normally, except when the Audi/Bose radio outputs a new display due to e.g. a change in CD track, radio station, etc. When the radio display changes, the TDS-1 will display the radio display for approximately 15 seconds, and then revert to the TDS-1 display. In this mode you get the combined function of a boost gauge and a "heads up" radio display.