Tach signal from LS coils

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Tach signal from LS coils

Postby banzairx7 » Fri Dec 22, 2017 9:57 am

I'm setting up an MS1 as an additional injector controller on a 2015 Chevrolet 4.3 V-6. I'm having trouble with getting a tach signal. This engine uses the same coils as the LS V8's so thought there would be an easy solution but I can't seem to find one.

The MS is set up to read a tach signal from the coil trigger as per instructions here- http://www.msextra.com/doc/general/tachin-v30.html#opto . Double checked my board mods and everything looks good. I'm running the tach signal into the MS on pin 25. I'm hooked into pin 3 on the coil.

Attached is my MSQ. We've done almost nothing as far as changing any settings at this point. Any help is much appreciated!
banzairx7
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Re: Tach signal from LS coils

Postby SwedCharger-67 » Fri Dec 22, 2017 11:26 am

I'm guessing here but a 2015 model probably uses a logic signal in to the tach? Old tachometers used the (very) dirty 12V spike from the primary coil of the ignition coil. My LS2 coils don't have anywhere such a voltage could be used.

I have from Summit Racing a converter that takes the 5V Tacho Out from the MS3X (don't know the MS1) and converts it to the dirty 12V spike that the my original Charger 67 tach needs. Don't recommend it however, has an annoying buzzing sound that follows the rpm.

MS docs show how to strip an inexpensive relay to generate the dirty 12V spike old tachs need, if that is what you need.
However, I think you need to tell exactly what you have
Martin, Sweden
Mopar 512 cui, 8.4 liters, high compression, fuel E85, full sequential control by MS3X, burning rubber just blipping the throttle... :D
SwedCharger-67
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Re: Tach signal from LS coils

Postby banzairx7 » Fri Dec 22, 2017 1:36 pm

Little back ground- This engine now resides in a Land Rover Defender along with a Comp Turbo CT4 Turbocharger. The factory tach was run off the can bus. We're running a Dakota Digital dash that reads the tach off the can bus also. The direct injection on this motor maxes out pretty quick so we're using the MS1 with two injectors before the throttle body to add additional fuel under boost.
banzairx7
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