Cheap Replacement Tachometer

[neworleansrich]

In various threads, there was interest in replacing or adding a tachometer to diesel engines.

Most inexpensive, off the rack, tachs (like Sierra) are only set up to accept spark pulses for 2 4 6 or 8 cylinder gas engines. Diesel engines commonly use either a gear sensor or alternator pulse train, hence the number of pulses per revolution can be almost anything. For example, I have a Cat 3126b that produces 120 pulses/revolution.

I found these cheap Tachs on eBay sold by many different "overseas" sellers that offer an alternative:


https://www.ebay.com/itm/85mm-Car-Tr...53.m2749.l2649

While, the descriptions do not explicitly say what range of pulses they can accept, it turns out they can be set to very wide range, up to at least 200 pulses/rev.

[tkeithlu]

A route I went was a small digital run off a magnet glued to the flywheel. Here's one at $19 from Amazon, with engine hours displayed whenever you shut down.

https://www.amazon.com/DIGITEN-Digit...037443&sr=8-11

I have a cheap analog, which I bought because it just seemed silly to use that tiny little LED digital on a honking big 4-53 diesel. Of course, I calibrated it on the digital. My only problem has been that it is far from accurate at the ends of the scale, having been calibrated in the middle RPM range.