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MSD 6AL and stock tacho


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#1 hanra

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Posted 10 February 2017 - 01:02 PM

Has anyone fitted a MSD 6AL into an LH or LX and continued to use the standard tacho? Or does it require a tach adaptor?
 
Has anyone split the Tach Output wire from the 6AL to run a tacho and trigger an EFI system?
 
I note MSD appear to state in this thread it can support 3 devices.
 
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https://forums.msdpe...erratic-reading

#2 76lxhatch

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Posted 10 February 2017 - 01:25 PM

I run the tach direct from the MSD 6A tach output. It works as well as any old Holden tacho... (needs reconditioning to read accurately at high RPM but its the fault of the gauge as usual).

There is no point in connecting this output to an EFI system as its timing-dependent, i.e. it already reflects any advance and does not provide an accurate reference. The best gains from EFI are made by controlling the timing anyway.

You can still keep the MSD unit with a number of GM and other style ECU controlled ignition modules, it just goes between the output of the other module and the coil.

#3 hanra

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Posted 10 February 2017 - 01:28 PM

This is what I am referring to. W/O timing control, it is required to be connected to the Tach Output of the CDI box.

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#4 76lxhatch

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Posted 10 February 2017 - 01:45 PM

Well it will stop you from getting too many signals (which would happen in multi-fire mode if it were connected direct to the coil) but if you have say 30 degrees of timing advance then its still going to be a crappy reference signal.

Looks like it is set up to use the green and violet wires direct to a magnetic pickup dizzy (which would then be locked) and control ignition timing? Without that its really just an electronic carb.

#5 hanra

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Posted 10 February 2017 - 02:14 PM

This is with timing control

 

 

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#6 _SRH11_

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Posted 10 February 2017 - 10:18 PM

Hi, I'm running a FiTech 600 hp Power adder and MSD 6A on a 308 in a UC hatch.

 

I made up a small electrical wire "Y" piece to split the signal coming out of the MSD box. One goes to the FiTech unit (I'm running w/o timing control) and the other to an aftermarket tacho (with shift light) and all works well.

 

I even tested it on the original UC tacho and it works (except it is a 6cyl tacho so the reading is out).

 

I have been running this combo for about 9 months and have had no issues with it.

 

Hope this helps.



#7 hanra

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Posted 10 February 2017 - 10:39 PM

Ok cool. Thanks for that. Sounds like it should work then. Will give it a shot.

#8 76lxhatch

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Posted 11 February 2017 - 05:19 AM

With timing control would be vastly better, and if its all built in the ECU already (i.e. no extra pieces to buy) then it seems silly not to use it?

#9 axistr

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Posted 11 February 2017 - 09:03 AM

What engine are you going to control with this system. Chev, Holden.



#10 hanra

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Posted 11 February 2017 - 09:17 AM

Holden. MSD tech support confirmed overnight that I can split the tach output wire. Will just have to wait and see how the tacho responds.




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