Electronic rev counter...

[Douglas Alderson]

Smiths / MGB rev counter swap the bezel for one off an older warn out speedo or clock. Replace the face with an aluminium disc and print off a new face on slip transfer, I also added the speed in 4th to the face. If you are lucky you can find a smith rev counter which is both 6v and 12v (adjustment on back).
   

[Bob Culver]

Useful for trails and racing but for most cars things happen realtively slowly. In a road Seven seldom any confusion about which gera in.It is not difficult to remember the mph speeds corres any arbitrary rev limit.

[Colin Morgan]

Hi,

Curious about revs so bought one of the cheap induction tachometers mentioned above from Amazon.  Just measured the revs as follows (figures in brackets were not achieved - extrapolated instead - as were some intermediate speeds.):

Look reasonable?  This standard 3-bearing Ruby engine also seemed happiest up to about 3000rpm.

Colin

[Oxford Jack]

Not quite along the lines of the previous correspondence but closely related. I have a Durite 52mm electronic rev counter in my trials car, the gauge reads 0-8,000 rpm. On the back of the instrument there is a switch for 4-6-8 cylinder use.
My question/s: if I change the switch to 8 cylinder, will it read at 50% of the revs? or is there a tech savvy reader who knows how to make the full scale read up to 4000 rpm, so that it suits the engine speed rather better than at present?
I could then remove the front and pointer, print a new face reading 0-4,000 rpm and have a more suitable instrument for my purpose.
Here is hoping!

[John Cornforth]

Hi

If you use the 8 cylinder setting, at any given RPM reading the instrument "expects" to see twice the rate of impulses compared to 4 cylinders. The scale will therefore be 0 to 16000 RPM when used on a 4 cylinder, which isn't very helpful.

There may be a way of modifying the internals but unfortunately I have no details of the inner workings of the Durite gauge.

When I needed a tachometer I used a secondhand Durite instrument scaled 0-4000 RPM. This was the sort aimed at the marine market, and is normally driven from the alternator as there are no igniton pulses available. The only workaround I found to this was to build a small driver circuit and use this to drive the meter movement directly, the original circuit being bypassed. I can give you a copy of the circuit if you PM me.

[Oxford Jack]

Thank you John, I realised shortly after writing that my first suggestion was bonkers! I will pm now
Thanks Jack