26 replies to this topic

[I hate Brian]

Hi all anyone got a smiths electronic speedo,I'm using a vthree gps unit all supplied by Digital Speedo's my problem is go above 30mph the needle goes round to 130mph stop and it drops back to o mph drive past 30mph and sticks at 50 mph or around to 130 mph again stop and goes back to omph until you hit 30 mph +

Now I have smiths rev counter fitted, electronic ignition by Keith Calver (CST9013  GT spec distributor with electronic ignition fitted) non resister spark plugs do you think the spark plugs not being resistive could cause this or the rev counter giving or overriding the electronic pulses, I've contacted Digital Speedo's who are at a loss only stating sometimes bike without resistive spark plugs have occasional issues.

Can I fit resister plugs with the distributor I have will this affect the performance just so I can rule the plugs out ?

 

Anyone throw some advice please

Edited by I hate Brian, 30 November 2020 - 04:19 PM.

[Spider]

I wouldn't put it past the plugs being at issue here. I recently had an issue with an ECU shutting down, after some frustration on behalf of myself and the manufacturer, it was that resistor plugs were not fitted that was the issue. Give the small signal level digital instruments work from, I can easily see RFI from non-resistor plugs being at issue here.

 

The other thing it could be is RFI from the Alternator, I have that causing another issue with an auto-changer between the Music Box and CB as well ! This is fairly easy to test for, disconnect the Main Charging lead off the Alternator and go for a drive.

 

Just another thought here actually,,,, does it do this at the same speeds in all gears or is it RPM related ? eg, if you try it in say 2nd, does it play up at around 15 mph ?

[I hate Brian]

Can I use resistor plugs with the electronic ignition setup I have Chris ?

[I hate Brian]

 

Just another thought here actually,,,, does it do this at the same speeds in all gears or is it RPM related ? eg, if you try it in say 2nd, does it play up at around 15 mph ?

I'm struggling really as the car has been off the road for 8 years and due its MOT so no tax or MOT just insurance so I haven't gone far only around my estate to try and bed the brakes in prior MOT tomorrow, really frustrated with the speedo as it cost a lot of money plus the GPS unit which are supposed to work fine together as a recommendation from Digital Speedo's. But in fairness to them and Caerbont they have been very helpful to a point.

[Tornado99]

Resistor plugs, caps, and HT leads are fine for electronic ign systems. Just watch how much total resistance is present between coil end and plug end of the leads and add it to the plug resistance amount. Typically a good coil is easily able to handle 5k to 10k resistance. This will bring down the interference significantly, which is the whole point. Electronic ign, radios, anything using computerized circuits are susceptible to interference. Older point igns and analog electrics are not susceptible to spark generated interference and thats why you didnt see resistor spark systems back in older days.
Adding proper resistance lowers voltages getting to spark gap, but only a very small percentage and not much of concern. More resistance increases the current across the gap, which means a longer duration spark, which is not a bad thing either.

[I hate Brian]

These are the plugs fitted at the moment DR15ZC Racing Spark Plugs Brisk

[Tornado99]

"R" in the plug code typically means they are resistor type plugs. You can check the rating by finding the plug spec online or asking your retailer. You can also measure the resistance directly by using a standard multimeter. As mentioned before n you should also check the leads from the coil end to distributor end and then from distributor to plug cap ends. Add up all the reading to get total resistance from coil to each plug gap. Thats how much resistance the electricity sees to reach the gap. Typically 5k to 10k Ohms is fine. If you check the coil specs on line you should find what resistance it is rated for.

[Spider]

I thought the same as Tornado when I saw the Part no. (R - Resistor Plugs). I've just looked them up and yes, indeed they are a Resistor Plug, so you can cross that off the list.

[Bobbins]

Just another thought here actually,,,, does it do this at the same speeds in all gears or is it RPM related ? eg, if you try it in say 2nd, does it play up at around 15 mph ?

I'm struggling really as the car has been off the road for 8 years and due its MOT so no tax or MOT just insurance so I haven't gone far only around my estate to try and bed the brakes in prior MOT tomorrow, really frustrated with the speedo as it cost a lot of money plus the GPS unit which are supposed to work fine together as a recommendation from Digital Speedo's. But in fairness to them and Caerbont they have been very helpful to a point.

As far as I'm aware you don't need an operational speedo for the MOT but you will need a way of showing the recorded mileage, re-fitting the original speedo would satisfy this.

[I hate Brian]

Hi bobbins I've gone from a three clock to a centre clock

[I hate Brian]

Good news is Brian passed  his MOT sailed through even on emissions.

Still having the needle bouncing around and sticking as per earlier posts, no rhyme or reason as to when it does this really after driving around for 40 odd miles

[Tornado99]

Is this a magnetic/inductive pickup on the sensor or is it running off the mechanical cable drive?

Could be a bad electrical connection or a poor sensor installation. Could also be a fault inside the speedo itself.

[Spider]

One other test here that maybe worth while is to roll on a hill with the engine off (and the ignition on to power the speedo) just to be sure it's not something screwy with the electronics. If you have metallic Brake Pads, it's not unknown for these to also be a source of interference with these set ups and this test may help show that up.

If your GPS wiring isn't routed through the engine bay, you can be reasonably certain that it's not ignition related. I'm not sure if you can relocate the GPS Pick up, even temporarily. but it might be worth moving it elsewhere and trying again.

 

I run Hall Effect Gearbox mounted senders on my Speedos. I did look at the GPS type, but I was put off because they need line of sight to the sky to work. There are some though that have dual inputs, that favour GPS when a good signal is available, but then will automatically change over to a Gearbox (or Wheel) sender when the GPS signal is unreliable (or not there !). I have been using a sender though, that was never a brilliant fit to the gearbox. These work OK for a while, but haven't been reliable as they get older. I purchased one from Mini Spares, that is a perfect fit, but is only 1 pulse per turn (it's advertised as 6 and even the included documentation says this, but the manufacturer confirmed it's 1), so below 30 kph, isn't smooth, but the needle pulse between zero and what ever speed your doing. Some I'm on the search for a suitable sender. I've found one that appears to be fitted to one of the Peugeot cars, mechanically, it seems a perfect fit, but I can't order one as no one yet seems to know what model it was fitted to.

[I hate Brian]

Hi Tornado99 its a Veethree GPS unit an American company who specialise in GPS  

https://www.digital-...ona-gauges-p445

[Tornado99]

If gps, then try moving the location of the GPS antenna and checking the connections. For it to suddenly drop to zero and jump the needle around, something has to be losing connection or signal.