technoversions tachmatch voltage booster

[kully 560]

I installed the technoversions tachmatch voltage booster on my early 260z today so I can have the stock oem tach working off of the msd 6a ingition direct. at first it was about 1500 rpms to high, and when I did start playing with resistors, I found that a 35k resistor worked with accuracy. the only problem I have is when the electric cooling radiator fan comes on the tach drops down and then back up to normal after the fan is running. now my thoughts are to maybe add a diode in line with the resistor. I did wire the tachometer direct from the voltage booster. I am looking for some input from any electronic gurus. thanks

 

[Zed Head]

Where do resistors come into the picture with the voltage booster?  The pull-up resistor?  Are there instructions that came with the unit?  Might help to take a picture and post them.  I don't see anything on the web site, except the FAQ's.  Probably want to tell which MSD wire you're using also.

 

https://www.technoversions.com/TachMatch.html

 

https://www.technoversions.com/Faq.html

[kully 560]

thanks Zed head for the reply, the signal from the voltage booster is 2 strong for the oem tach, I am running the msd 6a ingition which on the output tach connection it puts out about 3-3.5 volts according to msd ,that is why I went with the voltage booster. I now have to lower it with a resistor. I tried a 24k ohm resister with little change to the rpms. then I went to a 47k ohm resistor and the tach never moved. I then went to a 35k ohm resistor and the tach work great and the rpms are spot on. according to technoversions he had some 260z cars work fine just with the voltage booster.  it now works great except the current drop when the electric cooling fan comes on.  I thought about a diode in line with the resistor. what do you think.

[kully 560]

I sorry for not answering your question, it is not the tachmatch convertor it is the tachmatch voltage booster.

[kully 560]

Just now, kully 560 said:

I sorry for not answering your question, it is not the tachmatch convertor it is the tachmatch voltage booster.

or tachmatch v boost

[kully 560]

I see the new msd 6a has a plugin harness where my older msd 6a has the tach output on 1 side with a recessed spade male connector. and on the other side the harness for ingition and power.

[SteveJ]

You didn't use the ignition circuit to power the fan, did you?

Edited March 31, 2023 by SteveJ

[kully 560]

hi steve, the fan runs off of the battery and the ingition circuit only controls the 30a relay to power the fan. now also steve the turn signals will affect the tach also but very slight. that is why I thought about using a diode before the resistor or after the resistor to maybe to block the current draw? not sure!

[SteveJ]

A diode won't help you. Here's the issue: something is limiting current flow, such as a dirty fusible link, corrosion at the ignition switch, or poor contacts in the ignition switch. What ever the cause, the limits on the current flow result in lower voltage in the ignition circuit.

Think if a partially blocked pipe. Water can still flow through it, but as you open more valves downstream of the blockage, the pressure (voltage) drops.

If you put the year of your car in your posts (or in your signature), I can give specific diagnostics.

There's a good chance one of your future best friends will be a Dremel with a wire brush to knock off corrosion.

[Zed Head]

I wonder how the tach wire on the MSD box works.  That's where the voltage is coming from that is then either amplified or is used to trigger the Technoverion unit.  "generates a stronger signal".

I went back and found the instruction manual by accident.  Here's some text.  Click on Voltage Boost on the sidebar in the link and it will take you down to the instruction manual.  Haven't opened it yet.  So exciting!!!

https://www.technoversions.com/documents/TachMatchVBoostInstructionManualRev-.pdf

https://www.technoversions.com/TachMatch.html#TM4

TACHMATCH VOLTAGE BOOST MODULE

Most tachometers can be driven with a 12v pulse signal, such as that provided by the standard TachMatch and the MSD-6 series. However, some tachometers need a stronger signal that more closely replicates the signal generated by the coil.

The TachMatch V-Boost Module takes a lower level input signal, whether it be ECU output, MSD 6 tach output, or from a standard TachMatch TM-03, and generates a stronger signal to the tachometer, similar in function to the MSD 8920.

Another application is when you are changing from a coil-style ignition to a system that uses a ECU. Often, ECU's, with a 5-volt signal, will not drive tachometers designed to use a 12-volt (or higher) level signal. This unit will convert from the digital-level signal to one which will drive your tachometer, similar to the Auto Meter 9117.

The TachMatch Voltage Boost Module does not do cylinder conversion. If you need that, it needs to be driven from a TachMatch TM-03.

Details of it's connection can be found in the instruction manual below.

[kully 560]

I do understand what you are saying Steve, but I have a separate fuse block new next to the battery for the fog lights, msd ingnition, and electric cooling fan,also new key switch ect. maybe I will try going from a 35k ohm resistor to a 30k ohm resistor and see how that works. I just might be limiting a little much voltage. but with resistor change comes the rpm change which is spot on. I thought about the diode to help with the current draw so it might not fluctuate but you seem to think it will not help. I do need to be care full as to not damage the tach, I do have a dash cover I installed 30 years ago, and the tach can't be removed from the front anymore. now I really don't want to pull the dash for a new tach install. thanks

[Zed Head]

Here's the MSD stuff.  I've always wondered about the voltage sensing tachs.  Do they just see the voltage appearing and disappearing as the coil circuit is made and broken?  Or do they need the big "flyback" spike from the coil discharge?

 https://documents.holley.com/6425.pdf

TACHOMETERS The MSD Ignition features a Gray Tach Output wire that provides a trigger signal for tachometers, a shift light or other add-on rpm activated devices. The Tach Output wire produces a 12 volt square wave signal with a 20% duty cycle. Some vehicles with factory tachometers may require a Tach Adapter to operate with the MSD. For more information on Tachometers and MSD Tach Adapters, see the Tachometer Section on page 6. If your GM vehicle has an in-line filter it may cause the tach to drop to zero on acceleration. If this occurs, bypass the filter.

 

INOPERATIVE TACHOMETERS If your tachometer fails to operate with the MSD installed you may need an MSD Tach Adapter. Before getting an Adapter, try connecting your tachometer trigger wire to the Gray tach wire of the MSD. This output produces a 12 volt, square wave (see page 2). If the tach still does not operate, you will need a Tach Adapter. There are two Tach Adapters: