RPM gauge 12V on earth?

[gtt1951]

Panky, I've only just noticed something about your fantasic animated "signature" - the Traveller is Left-Hand-Drive (and, of course, it is riding on the right-hand-side of the road)!

Theo, I haven't applied a meter to my Grey car's 803 engine since going "electronic" - I'll have to see if two of my meters, the Gunson's Testune and Hawk Diagnostic & Tune-up Analyzer can still read off RPM.
If they can still measure RPM, then there must be a work-a-round for your gauge.
The only thing I tested, with the Gunson's, was the Dwell Angle, after conversion.
Before, the Dwell was about 55 deg (nearly correct), after, with the "adaptive dwell" electronic conversion, I was getting about 24 deg - don't understand why the drop, but it works. Dwell angle is the period that the points gap is closed.

[panky]

Panky, I've only just noticed something about your fantasic animated "signature" - the Traveller is Left-Hand-Drive (and, of course, it is riding on the right-hand-side of the road)!

I've been rumbled
Not mine I'm afraid, found it on the net ages ago - wish I had the knowhow to change it.

[gtt1951]

But it seems to be the right colour ...
G.

[panky]

A couple of shades darker than Bermuda blue unfortunately,but I use my imagination - and it makes me smile

[Theo_NL]

Theo, I haven't applied a meter to my Grey car's 803 engine since going "electronic" - I'll have to see if two of my meters, the Gunson's Testune and Hawk Diagnostic & Tune-up Analyzer can still read off RPM.
If they can still measure RPM, then there must be a work-a-round for your gauge.
The only thing I tested, with the Gunson's, was the Dwell Angle, after conversion.
Before, the Dwell was about 55 deg (nearly correct), after, with the "adaptive dwell" electronic conversion, I was getting about 24 deg - don't understand why the drop, but it works. Dwell angle is the period that the points gap is closed.

That sounds like there should be some kind of an electronic solution
The tacho works with an inductive sensor, the time the signal is 'high' could influence the functioning. If the signal could be extended or amplified, it might work....

First of all I will make a test set to simulate the pulse and check the proper working of the tacho with a clear pulse.
To be continued...

[gtt1951]

Theo, got the Grey car out and fired up the engine. Connected the Gunson's meter (as I'm +ve earth had to connect the RED lead to earth and the BLACK to the ignition side see below[frame][/frame]
Both leads were connected to the LT posts on the Coil. Meter did respond and showed the same RPM that I remember before fitting the elctronic replacement for the points - just under 1000 RPM (see next photo)[frame][/frame]
Whilst I was at it, decided to time the dizzy again, by ear, as the car was a bit sluggish last time out. So I thank you for getting me to check the car for the RPM display, as the new timing means the car has got back to better acceleration and higher road running speed - also adjusted the throttle stop screw to give a slightly lower tick-over speed.

[bmcecosse]

I'm bemused why the coil is connected to earth....but I suppose it must be something to do with your electronic ignition....

[chesney]

That's how the electronic ignition kits work for positive earth kits Roy. They're not really 'positive earth' kits, but convert the ignition to work with negative earth, as far as I can work out.

[bmcecosse]

Yes - I thought that would be the explanation.

[gtt1951]

I'm bemused why the coil is connected to earth....but I suppose it must be something to do with your electronic ignition....

Roy, both the +ve earth cars (the 918 and the 803 engined ones) needed this mod. The -ve earth conversions are actually cheaper to buy (like on the 1098 engined car).
Regards, George.

[bmcecosse]

Yes - I'm sure they are! Confuse the hell out of the AA man if you ever have to call one out........

[Theo_NL]

Theo, I haven't applied a meter to my Grey car's 803 engine since going "electronic" - I'll have to see if two of my meters, the Gunson's Testune and Hawk Diagnostic & Tune-up Analyzer can still read off RPM.
If they can still measure RPM, then there must be a work-a-round for your gauge.
The only thing I tested, with the Gunson's, was the Dwell Angle, after conversion.
Before, the Dwell was about 55 deg (nearly correct), after, with the "adaptive dwell" electronic conversion, I was getting about 24 deg - don't understand why the drop, but it works. Dwell angle is the period that the points gap is closed.

That sounds like there should be some kind of an electronic solution
The tacho works with an inductive sensor, the time the signal is 'high' could influence the functioning. If the signal could be extended or amplified, it might work....

First of all I will make a test set to simulate the pulse and check the proper working of the tacho with a clear pulse.
To be continued...

Reconnected everything and it works!
Must be special, RVI type of taco with electronic ignition. Measured the dwell angle too: 50 deg.

The tacho had an adjustment hole/screw on the back, and calibrated it at running idle. Now it shows 2500 rpm at driving 50 mph in 4th gear. Is this in the right range?

[bmcecosse]

Far too low rpm - but is the 50 mph accurate? More like 3000 rpm at true 42 mph..

[Theo_NL]

My Tom Tom navigation shows true 46 mph at 50 mph on the speedo. I will connect my flashlight/rev counter and make a trip to check.

[IslipMinor]

Theo,

50 mph speedo = 46 mph true = 2,800 rpm in 4th gear with the standard 4.22 rear axle ratio and 145/80x14 tyres.

I have the same Smiths rev counter RV1 on negative earth and it worked fine with the Aldon Ignitor electronic ignition - the induction loop has to be the right way round for the polarity (your instructions show that). The only problem was at night, as the illumination bulb sits almost on top of the calibration potentiometer and the accuracy goes way off! Same thing in bright sunny weather.

I was told that it I had the later 'innards' fitted it would not happen - it is much better, but not immune local warmth!

[Theo_NL]

Theo,

50 mph speedo = 46 mph true = 2,800 rpm in 4th gear with the standard 4.22 rear axle ratio and 145/80x14 tyres.

I have the same Smiths rev counter RV1 on negative earth and it worked fine with the Aldon Ignitor electronic ignition - the induction loop has to be the right way round for the polarity (your instructions show that). The only problem was at night, as the illumination bulb sits almost on top of the calibration potentiometer and the accuracy goes way off! Same thing in bright sunny weather.

Thanks Richard.
Yes, I was driving at night, so this could explain the difference 2800/2500 (i have standard rear axle and 145x14 tyres).

Case closed