86-88 Factory tach w/V8

[85_Ranger4x4]

I have some tidbits from when I looked into it 5 years ago, didn't know if anyone had more how to get them to work.

http://www.therangerstation.com/forums/showthread.php?t=113129&highlight=tach

 

[RonD]

Dakota Digital SGI-8E gets stock tachs working with any size engine, $85

You set it for Cylinders in, new engine size, say 8 cyl
Then set it for Cylinders out, old engine size and what stock tach expects, say 6 cyl

It is usually pretty accurate after that, but old tach could have been off originally so you can also adjust it, fine tune it, after cylinder setup

 

[85_Ranger4x4]

Searching along those lines I did find another option:

http://www.bakerelectronix.com/products_tsd/

Costs half as much but isn't adjustable. I don't see putting a 4 or 10 cylinder in my truck for it to be much of an issue though.

 

[RonD]

Hadn't seen that one.
Yes, most people don't swap engine SIZES multiple times in one vehicle, lol.

So getting a pre-set 4 to 8 or 6 to 8 for less $$ makes sense

 

[85_Ranger4x4]

I emailed them to see for sure which one I would need when I get around to doing this. I was thinking the 3/4 one since a V8 has more heartbeats per rev than a V6 and 6 is 3/4 of 8. 15 minutes later I get this back:

Thanks for your inquiry,

I've attached the manuals for the TSDr and the ATSDr for you to look over.


To determine which multiplier you need, the best way is for you to figure out by what factor your tachometer is currently reading incorrectly. If the tachometer is reading 1/2 of what it should, you would need a x2 multiplier to correct it, if it is reading 4/3 of what it should (33% too high) you would need a x3/4 multiplier to correct it, and so on.

You can also make an educated guess; if your new signal is from an engine that has 8-cylinders and the old one (that the tachometer was made for) had 6-cylinders, you might expect that your tachometer would read 8/6 (which is 4/3 or 1.333 or 33% too high), so you might need a x3/4 multiplier to correct it. But this is only an educated guess it's certainly a wrong guess if you are getting your signal from a different source. It is best to confirm how far off your tachometer is reading by checking the tachometer's readout at known RPMs. Or, if you just don't know, you may want to purchase the ATSDr which has eight of the most common multipliers that you can switch between.



Ralph Wise
Baker Electronix

And the adjustable one is $10 more.