Marshall Instruments specializes in OEM, private label and custom in-dash and pedestal mount tachometers. Contact us today for a quote.
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The Marshall Instruments 3-3/8" in-dash tachometers work with most 0.5-6 PPR (pulses per revolution) vehicles (1 to 12 cylinder). Our tachometers are designed to work with a wide variety of ignition types, including standard inductive coil (-) connection and any ignition system with a clean tachometer output signal. The input level can range from TTL 5V (outputs from newer
engine control modules) and 300-400 volt pulses from coil (-) on
most inductive ignition systems. Our
tachometers will operate on most traditional capacitive discharge
ignitions when connected to the ignition primary circuit. However,
for high-output CD's (such as MSD) only connect to the tach output
terminal, never the coil primary.
Calibration
Until recently, tachometers were calibrated based on the number of
cylinders in the engine. Now, there are all types of engine control
modules (ECMs - on-board computers) and distributor-less ignitions
and the old standard rule, "half the number of cylinders equals the
pulses per revolution (PPR)", no longer applies. Pulses per
revolution (PPR) relates to how many times the ignition fires per
crankshaft revolution. The tachometer outputs from the ECMs can
range from 1-PPR to 4-PPR for a V-8 engine. So, the new standard is
to refer to PPR instead of the number of cylinders.
Calibration of your Marshall 3-3/8" tachometer is done via dipswitches in the back of the gauge. There are 3 dipswitches, each of which can be set to OFF (down) or ON (up). Use the following table to determine the correct dipswitch combination for your PPR.
|
1 |
2 |
3 |
| 0.5 PPR / 1 CYL |
OFF |
OFF |
OFF |
| 1 PPR / 2 CYL |
OFF |
OFF |
ON |
| 2 PPR / 4 CYL |
OFF |
ON |
OFF |
| 3 PPR / 6 CYL |
0FF |
ON |
ON |
| 4 PPR / 8 CYL |
ON |
OFF |
OFF |
| 5 PPR / 10 CYL |
0N |
OFF |
ON |
| 6 PPR / 12 CYL |
0N |
ON |
OFF |
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The Marshall Instruments 5" tachometer sets the new standard for quality and value. We have packed all of the latest technology into this tachometer at an unbelievable price. Our Comp II 5" Memory Tachometer is available with or without an external shift light and comes in black or white dial versions.
Standard features include:
- high precision full sweep stepper motor movement
- 1.5" Six LED shift light
- peak RPM recall
- two color (amber and white) LED through-the-dial lighting
- attractive no logo dial for OEM look
- illuminated pointer
- low profile case with stealth black mounting strap and base
5" full sweep electric pedestal tachometer with two color LED through-the-dial lighting. Dial mounted control panel features 3 soft-touch buttons that control all features of the tachometer. Calibration, shift light activation point and maximum RPM recall are all accessed via the control panel.
Design features include black low profile case (approx 2.5" total depth), black strap with black rubber shock absorber and black mounting base. The low profile black shift light has six bright LED bulbs and a red lens.
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Use the following guides for where to obtain a tachometer signal for your application.
High Discharge Ignitions
Never connect the signal wire to the coil when using a high output discharge ignition system (i.e. MSD). Damage to the tachometer will occur and the warranty will be voided. Only connect the tachometer signal wire to the supplied tachometer terminal.
Distributor Ignition System
Connect the tachometer signal wire to the negative terminal of the coil.
Coil Pack, Distributorless, or Wasted Spark Ignition System
- Option 1. Connect the tachometer signal wire to the signal wire from the ECU to the factory instrument cluster. The PPR of this signal is usually half the number of cylinders.
- Option 2. Connect the signal wire to a coil trigger wire. There is typically 1 wire for each pair of cylinders. The PPR of this signal is usually 1.
- Option 3. Connect a tachometer adapter to a current carrying wire. Connect the tachometer signal wire to the adapter signal wire.
Coil Near Plug or Coil on Plug Ignition System
- Option 1. Connect the tachometer signal wire to the signal wire from the ECU to the factory instrument cluster. The PPR of this signal is usually half the number of cylinders.
- Option 2. Use this solution only if Option 1 is not available. Connect a tachometer adapter to a coil trigger wire. Connect the tachometer signal wire to the adapter per the adapter manufacturer's instructions.
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If the tachometer does not function, or functions erratically:
- Ensure the tachometer is installed correctly and has a good common ground.
- Verify the tachometer is obtaining the signal from the correct source.
- Ensure that the ignition system is in good working order in accordance with
the vehicle manufacturer's specifications.
- If the ignition system is in good working order but you still experience erratic readings, the tachometer may be picking up electro-magnetic interference. Try re-routing the tachometer signal wire away from all other spark plug wires, ignition coils and the alternator.
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