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Tachometer woes!
Posted: Wed Sep 28, 2016 7:22 pm
by paulsv8manta
Hi guys,
my existing Tachometer is initially from a four cylinder motor.
I started the v8 engine up very briefly and the Tachometer red lined!
Do I need to buy one specifically for a v8 or do i need to check my wiring?
Cheers
Paul
Posted: Wed Sep 28, 2016 9:02 pm
by ChrisJC
A 4 cylinder tacho won't work on a V8. But redlining sounds a bit odd. It would read double if it was working properly.
Chris.
Posted: Wed Sep 28, 2016 9:28 pm
by stevieturbo
A lot will depend on the actual unit.
Some may have a means of internal adjustment, or you can get creative and make it sort of adjustable.
Or use some sort of signal adjuster to change the number of pulses it sees
Posted: Thu Sep 29, 2016 11:30 am
by gelmonkey
Paul
You need a divide by two unit which will make your tacho work
might have one here for you.
Have you managed to get a spark then and fire the old tart up?
Cheers
P
Posted: Fri Sep 30, 2016 10:17 am
by paulsv8manta
Hi gelmonkey,
I found a break in the wire from the negative side of the coil.
When she fired up that's when I went into panic mode! Rev counter of scale, oil light that wasn't on (thought the bulb had blown) came on! Oil pressure gauge maxed out! But oh what a sweet sound!!!
Posted: Fri Sep 30, 2016 11:58 am
by DaveEFI
Depending on your electronic skills, it might be easier to replace the tach electronics with a modern IC that allows any of the common number of cylinders, and triggers easily from a low volt signal, rather than from the coil.
When I went wasted spark on my SD1, none of the adaptor circuits was 100% perfect. It's an open frame rev-counter, so easier to get at the electronics than a 'sealed' type in a housing.
Posted: Fri Sep 30, 2016 12:23 pm
by paulsv8manta
Hi gelmonkey,
I found a break in the wire from the negative side of the coil.
When she fired up that's when I went into panic mode! Rev counter of scale, oil light that wasn't on (thought the bulb had blown) came on! Oil pressure gauge maxed out! But oh what a sweet sound!!!
Posted: Fri Sep 30, 2016 4:02 pm
by gelmonkey
Re the oil gauge maxing out just swap the wires the other way around and that will sort the problem in a flash.
Bet it put a smile on your face once you heard the beast fire up mate.
You will soon have the same smile on your face as you did last weekend when I gave you a blast out in mine BUT it will be in your own car!!!!!
cheers
P