Classic Instruments - Speedo/Tach Interface Module - SN74Z

Speedo/Tach Interface Module - SN74Z

The SN74Z has the following features when used as a Speedometer interface.

Input Source Options

• Three wire pulse signal generator input source
• Built-in Vehicle Speed Sensor (VSS) input source

Most Tremec transmissions

Later model 700R4’s         

Typically a sine wave signal

• Two wire pulse signal generator input source

Classic Instruments SN96 or SN95

Typically a sine wave signal

• One wire ECM signals input source

Typically a 5 volt square wave

Output

• The output can be selectable between either 8000 pulse per mile or 16000 pulse per mile
• Outputs a 12V square wave, 50% duty cycle
• 8000 pulse per mile cruise control output

Additional Benefits

• Three different calibration options

Instant: drive 30 MPH and press the calibration button

Real-Time: press and the hold the calibration button to match the speedometer reading to the actual vehicle speed

Marked Mile: Drive a measured mile to calibrate the speedometer

• Input signal can range from 2000-200,000 pulses per mile
• State of the art signal averaging software that ensures smooth pointer operation, even in fluctuating signal conditions.
• Noise-reducing, filtered power output for powered speedometer signal generators

The SN74Z has the following features when used as a Tachometer interface.

Input Source Options

• High Voltage Coil signal input source

.5-6 pulses per revolution (1-12 cylinder engine)

Typically the negative side of an ignition coil

• 5-12V Square Wave signal input source

.5-6 pulses per revolution (1-12 cylinder engine)

20%-50% duty cycle

Typically from an electronic ignition box or computer

• Inductive Gear tooth sensor input source

Typically used in diesel applications where there is not an ignition system

The sensor can be mounted to the engine near the flywheel to sense the gear teeth as they rotate by

Can be used with 32-510 tooth flywheels, 32-510 pulses per revolution

Output

• Signal output

12V square wave, 50% duty cycle

2, 3, or 4 pulses per revolution (4, 6, or 8 cylinder)

3 preset flywheel tooth settings

148 tooth – Chevy Duramax

152 tooth – 5.9L Cummins

155 tooth – 7.3L Ford Powerstroke