How to get a tach signal from 3 coils ?

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ad francois
MS/Extra Newbie
Posts: 17
Joined: Sat Feb 19, 2005 6:00 am
Location: Bergen op Zoom , The Netherlands

How to get a tach signal from 3 coils ?

Post by ad francois »

I have a Goldwing 1500 6 cylinder (boxer) for which I want to use the negative coil wire as tach signal. I am using the megasquirt V2.2 and have 2 throttle bodies, each with one injector.
The engine has 3 coils (1 for each pair of cylinders) and is firing one coil each 120 degrees.
I did attach the tach signal to one coil on which I could start and run the engine. My fear is that 2 squirts per engine cycle is too little. Therefor I tried to hook up the other coils to the tach signal, but here I get stuck.
I am not that familiar with electronics, but I know this has to be done by using diodes. I tried a wiring diagram I found in the MSN-extra description to hook up multiple coils for the tachometer. This diagram is using one zener diode (3.3 v) and for each coil a normal diode (1N4004). I tried this, but without positive result. Is there anyone out there who can help me with a schematic how to derive the tach signal from 3 coils?
jsmcortina
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Post by jsmcortina »

I would try using one coil and pretend you have a 2 cylinder engine. Provided the rpm is displayed correctly it doesn't really matter seeing as you are fuel only.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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ad francois
MS/Extra Newbie
Posts: 17
Joined: Sat Feb 19, 2005 6:00 am
Location: Bergen op Zoom , The Netherlands

Post by ad francois »

This is exactly the condition I'm running on now, but as it's a 2*3 cylinder I want to have at least 3 squirts in a cycle, and if possible 6.
I'm worried about running some cylinders too reach and some too lean.
Do you have any experience with TBI and do you think it really matters ?
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