Alternator driven diesel tach?

[Chuckanut]

Hey guys, I’m looking for a 2 1/16 size tach gauge and I found a isspro gauge but it saids “ sensor required“. Has anybody not used the sensor and wired one up to the alternator? Or does anybody know of any 2 1/16 diesel gauges that wire up to the alternator I found 4000 RPM gauges that say they wire up to the alternator but they’re not for diesels. Thanks guys

 

[simp5782]

Hey guys, I’m looking for a 2 1/16 size tach gauge and I found a isspro gauge but it saids “ sensor required“. Has anybody not used the sensor and wired one up to the alternator? Or does anybody know of any 2 1/16 diesel gauges that wire up to the alternator I found 4000 RPM gauges that say they wire up to the alternator but they’re not for diesels. Thanks guys

The gauge doesn't care what engine it is.

Cockpit International 4,000 RPM 2 1/16" (52mm) Tachometer, 12V, 400-1300Hz Alternator Signal | Programmable Tachometers | Cockpit International | By Series | Instruments, Displays and Clusters | VDO Instruments and Accessories

Cockpit International 4,000 RPM 2 1/16" (52mm) Tachometer, 12V, 400-1300Hz Alternator Signal

www.vdo-instruments.com

 

[Barrman]

The CUCV alternators have a tachomoter output on the back for the STE/ICE system. Your tach might work off that signal. The best way to make it work and be able to get calibrated is to by the Dakota Digital diesel alternator tach adaptor. I have one on my CUCV engined and wired M715 and one on my 6.5 powered Suburban.

 

[Keith_J]

The gauge doesn't care what engine it is.

Cockpit International 4,000 RPM 2 1/16" (52mm) Tachometer, 12V, 400-1300Hz Alternator Signal | Programmable Tachometers | Cockpit International | By Series | Instruments, Displays and Clusters | VDO Instruments and Accessories

Cockpit International 4,000 RPM 2 1/16" (52mm) Tachometer, 12V, 400-1300Hz Alternator Signal

www.vdo-instruments.com

I have that tachometer in my CUCV, running off the driver side alternator. No adapter required.

The tach terminal is variable frequency alternating current from one of the three field windings. Most traditional tachometer use the ignition coil primary voltage which is a variable frequency pulsed direct current.

Stock 24 volt 100 amp CUCV have a 7.75 inch crank pulley and a 3 inch alternator pulley, meaning the alternator spins 2.583 times faster than the engine. The rotor is a 16 pole (8 north and 8 south poles). These factors are used to calibrate the tachometer.

This means every turn of the crank causes 2.583 x 8 cycles per revolution. For an idle speed of 625 RPM, that is a frequency of 215.25 Hz which can be measured with a good digital multimeter. 3600 RPM will be about 1240 Hz.

Keep in mind the engine can spin much faster than 3600 RPM, the fuel only.fully cuts off at 4400 RPM.

 

[Chuckanut]

I have that tachometer in my CUCV, running off the driver side alternator. No adapter required.

The tach terminal is variable frequency alternating current from one of the three field windings. Most traditional tachometer use the ignition coil primary voltage which is a variable frequency pulsed direct current.

Stock 24 volt 100 amp CUCV have a 7.75 inch crank pulley and a 3 inch alternator pulley, meaning the alternator spins 2.583 times faster than the engine. The rotor is a 16 pole (8 north and 8 south poles). These factors are used to calibrate the tachometer.

This means every turn of the crank causes 2.583 x 8 cycles per revolution. For an idle speed of 625 RPM, that is a frequency of 215.25 Hz which can be measured with a good digital multimeter. 3600 RPM will be about 1240 Hz.

Keep in mind the engine can spin much faster than 3600 RPM, the fuel only.fully cuts off at 4400 RPM.

So you have the isspro? Does it matter witch one? Also how did you hook it up to the alternator?

 

[Keith_J]

I have the VDO tach mentioned in the quoted thread.
ISSPro uses a Hall Effect or magnetic sensor, requiring 2 magnets to be installed on the crank pulley. Far from ideal because that is 2 pulses per revolution. And gluing magnets to the crank pulley is another failure point.

Alternator tachometers for the 27 SI have pulley ratio of 2.583:1 multiplied by 8 "pulses" per alternator revolution. Over 10 times the precision plus the signal is a sine wave, allowing for common mode rejection filter on the signal.

Alternator tachometers require calibration, the VDO was a bit fussy since the spin lock mount had to be removed for fine tuning with a jeweler's screwdriver.

 

[Chuckanut]

The gauge doesn't care what engine it is.

Cockpit International 4,000 RPM 2 1/16" (52mm) Tachometer, 12V, 400-1300Hz Alternator Signal | Programmable Tachometers | Cockpit International | By Series | Instruments, Displays and Clusters | VDO Instruments and Accessories

Cockpit International 4,000 RPM 2 1/16" (52mm) Tachometer, 12V, 400-1300Hz Alternator Signal

www.vdo-instruments.com

Do you when what settings I need for the tach?

 

[Keith_J]

Do you when what settings I need for the tach?

This tachometer has 3 DIP switches on the back , set #2 on, the rest off. Use the fine adjust for 625 RPM @ idle.
Instructions are online.

 

[chevymike]

I used a diesel tach from Speedhut Gauges for my build. It runs off the tach output on the alternator. I used a cheap Amazon RPM checker to establish the idle RPM's and then adjusted the tach to match. Works great.

RPM checker
https://www.amazon.com/gp/product/B004Q8L894

Speedhut Gauges - They are custom made to your specs (i.e. pointer style, font, color, lighting, etc)

Diesel Tachometer Gauges: Universal, Aftermarket & Custom | SPEEDHUT®

The ultimate aftermarket automotive gauges for any vehicle. Shop our huge selection of high-performance and customizable tachometer gauges - backed by a Lifetime Warranty!

www.speedhut.com

 

[Keith_J]

In case you cannot find the instructions

 

[Keith_J]

One more note on tach calibration..regardless if you use magnets attached to the damper pulley or Hall Effect sensor on ring gear, the tach only needs a one point calibration. This is how most tachometers can be calibrated with only a few switches and a fine adjust potentiometer.

Alternator stator alternating current is the same, the only weakness is belt slip.

 

[Chuckanut]

This tachometer has 3 DIP switches on the back , set #2 on, the rest off. Use the fine adjust for 625 RPM @ idle.
Instructions are online.

Great thanks!