EDIS 8 VR and Tach

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EDIS 8 VR and Tach

Postby garrycol » Mon Apr 10, 2017 1:56 am

I am in the process of wiring up EDIS 8. I have a VR sensor and trigger wheel fitted - the wiring diagram for EDIS 8 indicates that there is a positive side and a negative side of the VR sensor though I thought that it does not matter.

So is there a positive and negative side of the VR sensor and if so how do tell which connector is which?

Also can I connect my tach direct to the tach port of the EDIS 8 module or is there something else that is needed? Also on this - much later I will fit my LPG back on - as a safety feature it has an induction wire that wrapped around the HT lead of the distributor so the LPG picked up the induction pulses from the HT lead to tell the LPG that the engine is running - if not running the LPG is shut off. So with no distributor or HT lead can I use the EDIS 8 tach output to provide the required pulse to the LPG directly wired in.

The induction pulse from one of the spark plug leads (particularly with wasted spark) should be enough but looking a options.

Thanks

Garry
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Re: EDIS 8 VR and Tach

Postby DaveEFI » Mon Apr 10, 2017 4:58 am

Wish I knew the answer with VR polarity. Answer seems to be if it doesn't work or you have problems, try reversing it. :D

As regards driving a tach, it depends on the type of tach. Some need the high voltage pulse from the coil negative. Some work from a 12v one - or less. The options for additional drivers are covered in the manual.

As regards your induction coil, you may have to experiment with which of the two spark plug leads it works on. Just a guess.
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Re: EDIS 8 VR and Tach

Postby garrycol » Mon Apr 10, 2017 6:33 pm

Thanks - I thought a VR sensor was just a coil that got a small induced voltage into it when iron in the form of teeth on the trigger wheel passes by - so shouldn't matter how it is connected - maybe I will contact the seller for advice but that will take some time to get a response.

The tach is just a basic aftermarket unit that takes it input from the low tension side on the coil on a dizzy system - so is basically counting ignition firing pulses. In theory the tach out put of EDIS 8 should do the same.

So if anyone has a definitive answer on the poloarity of the VR sensor please speak up.

Thanks

garry
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Re: EDIS 8 VR and Tach

Postby garrycol » Mon Apr 10, 2017 10:06 pm

Found this on the internet so I will go with this.

Image
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Re: EDIS 8 VR and Tach

Postby garrycol » Tue Apr 11, 2017 1:09 am

Used the above information so now the EDIS 8 is all wired up and I have connected a spark plug and lead to each spot on the coils and have good spark at all eight spots. i9 just hope it is firing cylinders in the right order - Dave I am using the firing order/coil pack diagram you have provided me earlier so I will have someone to blame if the firing order is wrong :lol:

So tomorrow, I will reconfirm TDC and 10BTDC, put fresh fuel in and see if she fires up for the first on EDIS working alone.

Cheers

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Re: EDIS 8 VR and Tach

Postby DaveEFI » Tue Apr 11, 2017 1:26 am

The tach signal you get from the LT side of the coil is a lot more that 12v - due to the induction of the coil. It is a pulse with a peak voltage of perhaps 4 times that. Your rev counter may or may not work with a lower voltage pulse - try it and see. If not, you may need to add a simple circuit to replicate the coil pulse.
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Re: EDIS 8 VR and Tach

Postby garrycol » Sun Apr 23, 2017 9:15 pm

Well the engine is now running on carbs and the EDIS8 default mode for ignition. Runs on both petrol and LPG. The tach would not work from the EDIS module so I built a circuit that combines the Coil outputs into one tach input and works fine.

So once I get my annual gas certificate for the LPG (one of the reasons I need to get the engine running now before I am ready for the installation MS3) I will then pull off the carbs an put the injection system on.

So decisions will be needed on whether to keep the EDIS or not. If I just ran petrol there would be no reason to retain the EDIS 8 but if running on gas the engine will still run if MS3 has failed with EDIS providing ignition. The vehicle might run like a dog with any revs but will still run.

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Re: EDIS 8 VR and Tach

Postby DaveEFI » Mon Apr 24, 2017 1:46 am

Main disadvantage with EDIS is you can't set a spark cut rev limit with MS. Which is of no relevance on a standard RV8.
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Re: EDIS 8 VR and Tach

Postby jsmcortina » Mon Apr 24, 2017 2:33 am

garrycol wrote:Thanks - I thought a VR sensor was just a coil that got a small induced voltage into it when iron in the form of teeth on the trigger wheel passes by - so shouldn't matter how it is connected

It does matter.

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Re: EDIS 8 VR and Tach

Postby DaveEFI » Mon Apr 24, 2017 4:42 am

It would be useful if there were a convention for marking them.
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Re: EDIS 8 VR and Tach

Postby garrycol » Mon Apr 24, 2017 6:25 pm

This is the pic I used for the polarity of the VR sensor
Image

This is what I used for the tach signal generator
Tach_adapter_sch.jpg
Tach_adapter_sch.jpg (246.45 KiB) Viewed 314 times


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