The V8 Owners Forum -

i believe deisel altinators have a rev counter output?

my problem is that now my car will have 8 cylinders rather than 4 its goign to cock up my rev counter which usually gets its feed from the coil negetive, if i do the same here i will presumabley double my revs.

my car was origanaly a 4cyl carb/dizzy engine, and im goign to efi V8,

would it be possable to fit a deisel altinator and use that? from maybe a disco?


Ralph

If the alternator has a tach output, which I have never heard of, its only going to be as accurate as the belt driving it, different size pulleys will speed up or slow down the drive, and if its a v belt wear on the belt will also have an effect on the tach reading, any belt slippage will also adversly affect its peformance.
Probably the easiest way to sort out your tach is swop the internals from a V8 tach into your tach body just remember to use a tach with the same angle of rotation as your 4 cyl one.

i agree its not the best place for a tach read out but im pretty sure deisels use it as its the only electrical device on the unit.

not a bad idea taking rangy dials appart and putting its dial in to mine if they ahev the same angle read out.

can anyone confirm how the deisel system works?

and also where does '89 rangy get its feed from? coil negetive?



Ralph

hello mate a diesel gets it feed from the the alternator same as a rangerover does to i got a 1990 rangerover and taco dont work as i put a new alternator on it bloody crap think lol!!

I know some of the later 3.9 engines had a tach out on the alternator because that's what I have. Its the serp type pulley system though so if you wanted to use one you will probably need a custom pulley made.

Pretty sure earlier RRs had alternator driven tach as well . . . . but it's all a bit fuzzy.

Russ

Triumph GT6 had a "speedo type" cable out the rear of the alternator to drive the rev counter

IAn

do they give out a normal negetive pulce like a coil gives out then?

ie would an altinator work on a car which usually had a std coil??



Ralph

Chill out.......


Your rev counter will work fine, or can be adapted.

Try a search.....its been covered before.

Or take it apart first, there may already be a trim pot inside the rev counter, that allows you some adjustment for its output.

If there isnt, add a 1k trim pot into the feed going from the circuit board, to the actual coil of the rev counter, and that will allow you some adjustment.

All swing type meters end up as volt meters at some stage. You just need to reduce that voltage.

stevieturbo wrote:Chill out.......


Your rev counter will work fine, or can be adapted.

Try a search.....its been covered before.

Or take it apart first, there may already be a trim pot inside the rev counter, that allows you some adjustment for its output.

If there isnt, add a 1k trim pot into the feed going from the circuit board, to the actual coil of the rev counter, and that will allow you some adjustment.

All swing type meters end up as volt meters at some stage. You just need to reduce that voltage.

lol chilled!

very true, over looked that it would be a voltage goign to the needle part, would put a pot in there somewhere....

have searched but couldnt find anhthing relivent, probly searchign wrogn things...


Ralph

Ralphh85 wrote:do they give out a normal negetive pulce like a coil gives out then?

ie would an altinator work on a car which usually had a std coil??



Ralph

a coil triggered revcounter won't work on the alternator and vice versa

bodger wrote:

Ralphh85 wrote:do they give out a normal negetive pulce like a coil gives out then?

ie would an altinator work on a car which usually had a std coil??



Ralph

a coil triggered revcounter won't work on the alternator and vice versa

stevie turbos idea just got a hole load better lol


Ralph

Bodger is right, a rev counter intended for an alternator signal will not work with a rev counter intended for a coil -ve signal & vice versa.

In my limited experience of these instrument packs (from a variety of Montego / Maestro / LDV / etc):


The Diesel rev counters are supposed to be driven from an alternator 'W' terminal. Of course the calibration depends on pulley sizes as already stated.

The petrol rev counters can be modified to suit different numbers of cylinders. I modified the 150MPH instrument cluster from the Maestro Turbo (4 cyl coil -ve feed) to work with my V8 Sherpa (coil -ve feed). I also calibrated it so it was cock-on. I seem to recall changing one resistor on the PCB.

Previous to the 150MPH speedo, I did have a diesel rev counter running from alternator W, and it happened to be not too far out (maybe read 6K at 5K)

Chris.

thats like exactly what i wanted to hear, changing one restister on the pcb would be easy.

do you have any more info on which one?

my dials look very similar to thoes being rover.

my rev counter goes to 7 which is a bit over the top but doesnt mater i guess.


Ralph

I did make a note of what I did (for future reference!!), I've just got to find it. I'll try to remember to look this evening...

Chris.