83-84TC tach modification - input needed

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83-84TC tach modification - input needed

Reply #30 – December 31, 2012, 06:20:04 PM

Thanks guys! this looks like the solution, how does someone order one of these?

83-84TC tach modification - input needed

Reply #31 – December 31, 2012, 08:49:32 PM

What do you want to order?? The northern one or the one i posted??? I have used many tach adapters over the years. And basically the difference is the pulses per min. The gauge it self should be identical i would imagine. Just a meter movement. But not an electronic engineer. Only thing we do when we install universal tachs is set the switches or select a resistor

83-84TC tach modification - input needed

Reply #32 – December 31, 2012, 09:45:34 PM

I'm trying to find as much info as I can for a guy that is interested in purchasing the cluster I have. He's wanting it to work with his 5.0 and is also trying to find info on how to do so. all help is appreciated.

83-84TC tach modification - input needed

Reply #33 – December 31, 2012, 10:19:14 PM

i know right now who has the answer, havent seen him around in so long though,, bondocougar,, and master blaster,, niether have been around for so long but thier legendary work is remembered

83-84TC tach modification - input needed

Reply #34 – January 01, 2013, 09:11:00 AM

Jay it seems to me that all is needed is a TACH module. If memory serves me they are available from many outlets like MALLORY. Basically what you did with the volt meter. I am willing to bet the movement is identical in specks. So just use the movement with a remote transmitter that is calibrated for a V8.

OR buy a tach and use the guts to power the stock tach gauge movement. Another words use the electronics to power the in dash meter movement!!! Bet it will work!

83-84TC tach modification - input needed

Reply #35 – January 01, 2013, 12:42:40 PM

thinking out to loud here,,,
wondering why a tach couldnt be operated off vac pres. this would eliminate the qty of cylinders and calibration.

83-84TC tach modification - input needed

Reply #36 – January 01, 2013, 01:20:43 PM

Mechanical tachs have been around for years. But never saw a vacuum one????????????

JAY you surprised me on this one. After you went to all that trouble making an AMMETER in to a Voltmeter. A tach should be a piece of cake. Once again buy a tach buttstuffog in nature and use it's internal electronics. Then wire it to the original movement in the dash. Simple and i think it will work. Or better yet use a V8 ford Tach in place of the 4 Cyl unit. Or just use the V8 electronics to power up the 4 CYL tach movement. Or use a V8 unit and swap the face plate .Not Brain Surgery. just something i think would work!!

83-84TC tach modification - input needed

Reply #37 – January 01, 2013, 02:12:16 PM

I didnt make the ammeter into a volt meter, i gutted the housing and stuffed a volt meter in there. kept it simple.
the item you posted is turnkey and why bother,, it satisfies the univeral requirement.
\

the vac tach occures to me evertime i hook up the vac tester to test and say to myself,, now this guage reads fairly linear with rpm,, why cant it be used to illustrate rpm.
yes i know this isnt 100% true but the vac needle moves,, with R's ,, im sure its already been thought and thrown out as an option.

i love vac operated devices,, keeps things simple

83-84TC tach modification - input needed

Reply #38 – January 01, 2013, 03:12:46 PM

Would two cars with two different engines (different displacement, or even different mileage on the same engine type) produce the same measure of vacuum at the same RPM? Probably not. That's probably why there's no vacuum tach. You'd have to calibrate it for every engine. Then probably recalibrate it as the engine ages. Whereas an electrical pulse is a cam rotation on every engine.

If we're reinventing the wheel, and you want true universal tachs, we should measure from the crank sensor pulses. One blip, one rotation, regardless of cylinders. I know, most older cars don't have a crank sensor...

83-84TC tach modification - input needed

Reply #39 – January 01, 2013, 04:19:35 PM

Easy enough to get your signal...run a wire to the coil, positive side. Green and white wire. On my cars, I've just popped the pin out of the connector, and added the new wire to it, then reinstalled it into the connector

83-84TC tach modification - input needed

Reply #40 – January 01, 2013, 04:59:42 PM

I don't want to go back to vacuum windshield wipers. They were a pain.
They would stall when you stepped on the gas and go like crazy when you got off the gas.
You wound up adjusting your driving habits to what the wipers wanted you to do.

83-84TC tach modification - input needed

Reply #41 – January 01, 2013, 05:02:22 PM

Coils Positive side SORRY CHARLIE NO PULSES THERE.

83-84TC tach modification - input needed

Reply #42 – January 01, 2013, 07:34:08 PM

A Vacuum tach wouldn't work because vacuum is more dependent on engine load than it is on RPM. For example there is very little vacuum at WOT, regardless of engine speed. There is very high vacuum at closed throttle as well, both at idle and when you let off on the gas. Vacuum could be (and has been) used as an economy gauge. Lower vacuum (IE closer to atmospheric pressure) generally equals higher economy. This is why "highway" gears provide better economy - larger throttle opening and low RPM for a given speed gives better fuel economy versus nearly closed throttle at high RPM.

Quote

Well thought i would post that SORRY. But from memory a resistor change is what is needed as i remember. Years back a tach had a couple of different resistors for calibration. Honestly i cant think the electronics would be different. pulses are Pulses. Sorry for trying to help!

Tom: First off, get your panties out of a bunch and learn to accept when somebody points out a mistake you've made. We know you didn't purposefully try to send anyone astray here, and nobody is shoving bamboo shoots under your fingernails, so no need to act like they are. Second: A pulse most certainly is not a pulse. Pulses vary in strength (voltage), frequency (hertz) and duration (milliseconds). The only one of these three variations that a tach is concerned with is frequency, which changes with engine cylinder count. The more cylinders, the more pulses per second for a given engine speed. No resistor change on the input side of the tachometer can correct for this.

As for resistors: When you replace a resistor in a tach to calibrate it, you are changing the resistance in the part of the circuit that actually moves the needle, not the part of the circuit that counts revs. A tach is basically a primitive digital-to-buttstuffogue converter (DAC). It converts the digital signal of the coil to an buttstuffogue signal that moves a needle. It converts a digital count (how many pulses per second) into an buttstuffogue signal (how much voltage). Higher counts convert to higher voltages, which moves the needle higher. Changing a resistor to recalibrate it merely changes the amount the needle moves for a given signal from the DAC. The DAC still puts out the exact same signal to the needle, but a resistor changes how much of that signal the needle sees. In very basic terms, let's say that you have a 4-cylinder car. A 4-cylinder fires a spark plug every 180 degrees of crankshaft revolution. This means there are two pulses for every full revolution of the crank. The tach's internal DAC sees two pulses per revolution, but does not know how many revolutions are happening, it's simply calibrated for a certain number of pulses over a certain amount of time, and puts out , say, a 3 volt signal at 2000 RPM. That three volt signal causes the buttstuffogue needle to move to a certain position, which is marked "2000" on the face. Installing an 8-cylinder engine doubles the number of pulses per minute (A V8 fires a plug every 90 degrees of crank revolution, so 4 pulses per revolution). The digital side of the tach would now see twice as many pulses over a given time. Since it does not know how many revolutions are happening (it merely counts pulses per second) it "assumes" the same engine is installed but spinning twice as fast. It puts out, say, 6 volts now, which shows 4000 RPM when the engine is actually only spinning at 2k. The key is to intercept the signal between the DAC and the buttstuffogue needle and change it so that it shows actual engine speed (IE to reduce the 6 volts down to 3, so that when the engine is spinning at 2k RPM the needle only shows 2K RPM). Since it's an buttstuffogue signal the easiest way to do this is a resistor change. The problem is finding which resistor on that circuit board, then using trial-and-error to determine the correct value. This is how the 87-88 style tachs were "cracked".

You might be able to find the key resistor in the 83-84 style if you can trace the circuits back from the buttstuffogue needle. You might even be able to calibrate it yourself by installing a variable resistor in series between the tach's circuit board and the actual needle, but this would require the use of a signal generator to simulate the engine's output while tuning. To do this you'd need to set the signal generator to a certain frequency (say 20,000 pulses per minute, or 333 pulses per second, or 333 Hz, which would be equal to 5000 RPM on a V8) and then adjust your variable resistor so that the needle shows 5000 RPM. Since this circuit very likely wouldn't be "linear" (IE the required resistor value might vary at different tach readings) you'd be advised to choose something close to redline to calibrate to, since this is the most important end of the tach...

83-84TC tach modification - input needed

Reply #43 – January 02, 2013, 01:54:26 AM

thinking out loud again,,
wonder what a split core CT would do for information gathering placed on the coil wire. Split core ct's are not all that expensive either especailly the size we are talking, Square D makes several we use for whole facility or individual circuit current monitoring, i know exactly whats happening inside them, never occured to me what they would do around a coil wire. they are passive as well, thats a plus.

i think we got a bunch of idea hampsters around now, its good to think and wonder once in a while, keeps you on your toes.

83-84TC tach modification - input needed

Reply #44 – January 04, 2013, 10:45:30 PM

Ok ladies and gentlemen. I totally know that a series resistor in the Kettering Ignition system wont change the Tachs ability to sort out Pulses. If this bugs you and you need a place to hook up a TACH use the alternator. tach pulses can be obtained their. Other than the hundreds of tachs i have installed over the years they either have a select switch for cylinders or an INTERNAL RESISTOR TO CHOOSE FROM. And or a combination of resistors to alter the tachs cylinder designation. I did not post a series resistor for tach selection on it,s lead gathering info from the coil.

NOTE DIESELS get Tach pulsed from the alternator. Imagine that!!!

Electronic tachometers work by counting pulses.

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

This is from FORD!!!

The tach signal is a pulse. The factory pickup spot is pin 4on the computer. The wire color is a dark green/yellow for 88-91 cars.

Altering the tach for different cylinders may include a condenser and or a resistor or a combination of both. I am not an electronic engineer. I have a double masters in mechanical engineering. So i corrected a post!!! And got thunder mad. I will be available next week for the lynching at a described time as posted by Thunder Chicken . Make the arrangements with him.