Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

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datsun.dave
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Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby datsun.dave » 15 Jan 2018 16:47

Hey Guys -
I have just gone through the process of wiring in a stock tach to my 72 510. The car runs an EI matchbox distributor and I believe that I have it wired correctly after reading through multiple posts and a bunch of surfing - and chatting to Jim - Zkars.

The tach reads close at idle, but the slightest throttle pressure and it pins to 8000rpm.

There are a couple of mentions on several articles suggesting adding a resistor inline to reduce the intensity of the inductive signal. So, I started with a 1k Ohm resistor at 5W, and the car wouldn't even start... resistors were available all the way down to 1/4 watt, but honestly, I am completely out of my wheelhouse at this point so I don't want to just keep buying random resistors...

So, does anybody know what wattage makes sense in this case? And does anyone have any real world experience with this problem and successfully resolving it?

Thanks Guys!
David Wilson
65 WPL410 Wagon
67.5 SRL311 #00050
68 SPL/SRL311 Racecar project
72 510 Sedan - L18 w/Webers and Dogleg 5 spd
74 260Z - L26 w/ Triple Webers and 280ZX 5 spd
88 Be-1
89 Toyota HiAce Work Truck
91 Figaro

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Heinrich
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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby Heinrich » 15 Jan 2018 21:05

from what i remember about old tacho's is that the actual coil drive signal is router through them.
so if a resistor is added in line it will reduce power to the coil.i would suggest starting with a 5 Watt 1 ohm to minimize power loss and move up from there with resistance.
you could also run 2 parallel wires.one through the tacho and one just bypassing it, thus halving the inductive power in the wire.
Progress is slow, but it is progress non the less.

datsun.dave
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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby datsun.dave » 15 Jan 2018 22:40

Thanks for the response Heinrich. I don't know enough about electrical to recognize a reasonable starting point, but the couple of posts I saw suggested 1K ohm - implying that it had been done that way and worked. So, primarily I am wondering if my wattage was just too high... Does that make any sense? You are suggesting reducing the ohms vs. reducing the wattage? There are lots of guys who seem to have had success with the same set up as me, so I don't want to reinvent the wheel unless I have too...
David Wilson
65 WPL410 Wagon
67.5 SRL311 #00050
68 SPL/SRL311 Racecar project
72 510 Sedan - L18 w/Webers and Dogleg 5 spd
74 260Z - L26 w/ Triple Webers and 280ZX 5 spd
88 Be-1
89 Toyota HiAce Work Truck
91 Figaro

datzenmike
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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby datzenmike » 16 Jan 2018 06:04

Wattage is just a measure of how well the resistor dissipates heat that is produced. A 1,000 ohm 5 watt resistor is identical to a 1,000 ohm .5 watt resistor as far as resistance.

Points and EI are essentially the same... an on and off 12v signal. I had an inductive Datsun tach from a 1200 in my L20B EI 620 and it worked just fine.

Just for giggles swap the wires so the signal goes through the tach in reverse to what it does now.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

datsun.dave
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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby datsun.dave » 16 Jan 2018 10:11

Hey Mike -
I did try the tach the other direction... I saw a couple comments about that too... in the opposite direction, it didn't respond...

That is cool info about the resistor. So, does that mean that the 1k resistor at 1/4 watt would probably lead to the same result? I am assuming as much. So, practically, Heinrich's point is probably more appropriate - reduce the resistance... maybe try 500 vs. 1k...
David Wilson
65 WPL410 Wagon
67.5 SRL311 #00050
68 SPL/SRL311 Racecar project
72 510 Sedan - L18 w/Webers and Dogleg 5 spd
74 260Z - L26 w/ Triple Webers and 280ZX 5 spd
88 Be-1
89 Toyota HiAce Work Truck
91 Figaro

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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby 510rob » 16 Jan 2018 10:17

The factory tach is supposed to be wired INLINE with the +12V feed to the coil.

One end of the white wire goes into the tach, makes a few turns through what forms a simple current transformer, then comes out of the tach as the same piece of wire. I should have taken pictures of my tach when I had it opened up, but I am not good at documenting things; from a circuit perspective, that white wire is just a piece of white wire that is about 16ga. As the coil is charged/discharged etc., the tach's internal circuitry picks up a bit of transient noise from those little loops of the white wire as it passes through...

+12V power comes from the battery, through some kind of fuse, through the ignition key, through the tach, through the + terminal of the ignition coil primary to the - coil primary terminal, through the EI box, to ground, and back to the battery. Circuit completed!

That said, how do you have the tach connected? (I'm not sure where you would put a 1kΩ resistor).

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TheHeretic
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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby TheHeretic » 16 Jan 2018 12:03

I wired mine up correctly and it still wasn't very accurate and would jump around a lot. Had West Valley Instruments rebuilt it and part of the process was for them to modify it so that it picked up the signal with a single wire to the negative side of the coil. Very easy install and it works just fine now.
http://westvalleyinstruments.com/
Carpe Diem!
Ryan

datzenmike
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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby datzenmike » 16 Jan 2018 14:39

It should be connected between the coil negative and the EI. Or take the wire off the coil negative terminal and insert the tach between to complete the circuit.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

datsun.dave
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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby datsun.dave » 16 Jan 2018 21:55

Hey DatzenMike -
Ya, I have it on the coil negative.

Goes from ignition, through tach, to coil negative. I would really like to know if anyone has had success with the resistor concept - there is mention of that in the Dime Quarterly article... I am just throwing darts guessing now... I guess it is possible that the tach is screwy too... but don't want to rebuild it unless I need to.

Thanks guys, all feedback is appreciated for sure!

510 Rob - I think when you are saying +12V feed to the coil, we are talking about the same thing - the ignition power from the switch sends the 12V to the - side of the coil... Right?
David Wilson
65 WPL410 Wagon
67.5 SRL311 #00050
68 SPL/SRL311 Racecar project
72 510 Sedan - L18 w/Webers and Dogleg 5 spd
74 260Z - L26 w/ Triple Webers and 280ZX 5 spd
88 Be-1
89 Toyota HiAce Work Truck
91 Figaro

510rob
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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby 510rob » 16 Jan 2018 22:54

Hi David,

I have never seen a wiring diagram for the optional OEM PL510, but there are diagrams for the 240Z, which essentially uses the same type of circuit as the one in the optional PL510 tach...
Attachments
Datsun 240z Tach Wiring.jpg
Datsun 240z Tach Wiring.jpg (186.02 KiB) Viewed 194 times

510rob
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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby 510rob » 16 Jan 2018 22:56

also, I borrow-shared the picture from http://woodworkerb.com/wp-content/uploa ... Wiring.jpg

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Byron510
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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby Byron510 » 17 Jan 2018 03:52

If the tach is hooked up to (-) then it’s not wired as it should be stock.
As Rob noted above, the 510 tach has an inductive pick up which works on the (+) side of the coil.
The 510 harness never included the factory tach, the factory patch was to have a sub harness which plugged into the factory coil (+) feed (disconnected from the coil obviously), then ran back through the firewall at the drivers side and just before the subharness conected to the tach, this white wife had a split which also fed the tach power (yes he tach actually leached a bit of cool (+) juice. The two white wires on the back of the tach are simply an inductive coil pick up, which is why they are both white. Then this power wire goes back to the coil (+). So this takes care of 3 of the 5 wires on the back of the tach. The other two wires are conected to a 3 prong in-line plug in he factory harnes which was intended to run the clock in the same pod. This plug is usually under a bit of blue tape in the factory dash harness and it contains 3 wires; one constant power (unswitched to keep the clock going - don’t use for powering the tach), one powering th dash lights and one ground. For the tach installation you need the light harness and the ground to operate the tach. So there you have the factory 5 wire connections as per the factory wiring harness installation.

Hope that helps.

Byron
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because the opposite never works.

datzenmike
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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby datzenmike » 17 Jan 2018 08:41

No not what I said. The tach is fitted in line between coil negative and the distributor. Not between ignition and coil negative.

It may work between ignition and the positive terminal, but I connected on the negative side.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

datsun.dave
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Location: Calgary, Alberta, Canada

Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby datsun.dave » 17 Jan 2018 10:08

Ok. I think I may have distilled this into an understanding of where I went wrong... I will try again and report back.

Thanks very much guys.

dw
David Wilson
65 WPL410 Wagon
67.5 SRL311 #00050
68 SPL/SRL311 Racecar project
72 510 Sedan - L18 w/Webers and Dogleg 5 spd
74 260Z - L26 w/ Triple Webers and 280ZX 5 spd
88 Be-1
89 Toyota HiAce Work Truck
91 Figaro

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abisel
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Re: Factory Tachometer Install with EI - Resistorr Size for use with EI Dizzy

Postby abisel » 17 Jan 2018 14:07

Maybe this will help.
6tach_wiring_72_sedan_std[1].gif
6tach_wiring_72_sedan_std[1].gif (53.69 KiB) Viewed 159 times


Be sure to connect the tach power wire (green) from the tach to the switched ignition power to the heater blower/radio power.
The ground (black) wire can go anywhere on the chassis.
The two white wires that have been discussed go "before" the ballast resistor, to the tach and back to the ballast resistor. The tach is in series with the ballast resistor and (+) terminal of the coil.


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