Lotus Elan

tacho part 2

PostPost by: Ennva » Thu May 01, 2014 8:37 pm

Having read a few post, my tacho is an RVI negative earth, any help on wiring this with accuspark system. it was previously working fine on the lumenition system.
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PostPost by: rgh0 » Thu May 01, 2014 11:51 pm

Wire it up according to the instructions except dont take the power supply to the unit from the coil positive connection as shown on the installation diagram. If you do that then you introduce additional current pulses generated by the unit itself as it works into your tach sensing circuit which is on the postive supply to your coil. Take the powr from a separate 12V supply that is switched by the ignition switch.

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PostPost by: Ennva » Fri May 02, 2014 12:38 pm

OKAY, THE PART MAKES sence, i have a seperate power feed to positive side if coil, remove this and connect directly to positive side of accuspark. Do i then install the current white tacho wire on the positive or low tension side of coil.

many thanks
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PostPost by: rgh0 » Fri May 02, 2014 12:45 pm

I don't understand - do you have 2 wires going to positive side of coil currently? Do you or did you have the ballast resistor ignition system.?

Some pictures or diagrams of what you currently have would help. The lumenition should have had a switched power supply to it that was separate from the white power supply to the coil positive that comes from the tach if it was previously installed correctly

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PostPost by: Ennva » Fri May 02, 2014 1:38 pm

Yes, the lumenition was seperately powered, i have taken this feed direct to coil and then to accuspark.

From reading your reply take this and connect drirectly to accuspark, then connect the white tacho wire to the coil

amny thanks indeed
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PostPost by: jeff jackson » Sat May 03, 2014 11:20 am

I would be very careful wiring your RVI Tach to the Accuspark, I blew my first accuspark up with my RVI tach.
Best get your Tach converted to RVC or do it yourself, its very easy, you can buy a conversion board off Fleabay for about 40 quid, or design the circuit yourself if you are confident.
Also please search the archives on this forum, I know there is a long thread about this WRT converting tachs from neg to pos, and to RVC.
I might just add you may get away with using your RVI without damaging your Accuspark, many have. Many like me have also blown them up.
Hope it helps.
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PostPost by: rgh0 » Sat May 03, 2014 12:01 pm

I don't understand how a RVI current sensing tach could cause damage to an accuspark unit. Can you explain more on the technical reason for it?

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PostPost by: jeff jackson » Sat May 03, 2014 1:00 pm

Hi Rohan,
Yes I can, but i am in the middle of exam revision! There was something about it on the forum.
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PostPost by: rgh0 » Sat May 10, 2014 1:43 am

I have read most of the posts on tacho and electronic ignition issues but cant find any technical explanation of the possible way an accuspark could be damaged by a RVI tach so appreciate any derails when you have a chance.

I struggle to understand it as there is no direct connection between the tach and the ignition circuits that the accuspark is connected to -- just a loop of wire in the power supply to the coil that the tach senses the changing magnetic fields in.

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