Digital Tachometer

[aviationfred]

I thought,    While I will be installing the digital GPS speedometer. Why not do a digital Tachometer?

This is what I found.

http://youtu.be/Mt9VYgqsEts


http://www.ebay.com/itm/Summit-Racing-Tachometer-LED-0-9900-rpm-3-3-8-in-Digital-Electrical-Each-/191286013885?pt=Motors_Car_Truck_Parts_Accessories&hash=item2c8988efbd&vxp=mtr#ht_1600wt_867

Fred

[Tuneforkfreak]

Fred is this what you're shooting for  as an end result ? http://www.shorelineaviation.net/Portals/17518/images/Matte%20Black%20Glass%20Instrument%20Panel_Piper%20Aircraft%20Premier%20Elegance%20Interiors_.jpg Hope my link worked. Just kidding around with a fellow pilot! I think it will be cool when you get it done, cant wait to see it.

[aviationfred]

Fred is this what you're shooting for  as an end result ? http://www.shorelineaviation.net/Portals/17518/images/Matte%20Black%20Glass%20Instrument%20Panel_Piper%20Aircraft%20Premier%20Elegance%20Interiors_.jpg Hope my link worked. Just kidding around with a fellow pilot! I think it will be cool when you get it done, cant wait to see it.

Great looking glass cockpit in a Piper. I have worked on similar equipment, (Learjet, Cessna, Beechcraft, Bombardier Business jets). I am not a pilot, but I have been around aviation since I was old enough to talk. I also have been a helicopter/airplane mechanic and avionics tech since I was 20 years old.

I have also ordered a digital oil temp gauge like this.



Fred

[fj1289]

Fred - are you going I start the FJOwners hole saw kit?! 

What's the plan for mounting the gauges?  Modify the stock dash pod or replace it?

I'm still a steam gauge guy myself -- but use glass when I need to!

[aviationfred]

Fred - are you going I start the FJOwners hole saw kit?! 

What's the plan for mounting the gauges?  Modify the stock dash pod or replace it?

I'm still a steam gauge guy myself -- but use glass when I need to!

The digital speedometer and tachometer will drop into the existing corresponding holes in the OEM instrument panel. (No cutting needed) 

The oil temp gauge will need a hole cut in the right hand panel between the fuel tank and the main fairing.

Fred

[Bozo]

Fred - are you going I start the FJOwners hole saw kit?! 

What's the plan for mounting the gauges?  Modify the stock dash pod or replace it?

I'm still a steam gauge guy myself -- but use glass when I need to!

The digital speedometer and tachometer will drop into the existing corresponding holes in the OEM instrument panel. (No cutting needed) 

Fred

FYI, I installed a speedhut 3 3/8" GPS speedo and it is fantastic. It did require some gentle filing/dremelling of the facia and the main body and then I simply? used selastic/ RTV to hold it down.
I used the old reset button to control the GPS speedo functions by extending a pair of wires to a push button C&K switch. The GPS pickup can be seen on top.

[aviationfred]

I received the Digital Tachometer to day. At the moment, I would not recommend this as replacement for the tach. It will not fit in the center. The face is too tall and the clear cover hits the lower part of the tachometer.

I was able to move it to the left side and put the digital speedometer in the center. To make all of this fit, I had to severely modify (hack up) the white instrument housing.

Also once everything was hooked up, the RPM's seem to be about half of what they should be. I will be calling the manufacturer tomorrow to see what should be done to fix the issue.

Here is a video of the tach.

http://youtu.be/MO3eFkOqrTE

[FJ_Hooligan]

There should be a 4cyl/8cyl switch (or programming parameter or jumper) that will fix the 1/2 reading.

Found the installation instructions.

Instructions say: "For 4 cylinder operation, cut the BLUE wire loop."
"For 6 cylinder operation, cut the ORANGE wire loop."

If you didn't cut either of the wire loops, it thinks it's an 8 cylinder

[aviationfred]

Instructions say: "For 4 cylinder operation, cut the BLUE wire loop."

I cut the BLUE wire loop.

My idle was about 1100rpm with the OEM tach. With the digital tach it is now 600rpm


Fred

[fj1289]

Yeah, but we have wasted spark ignitions, plus what is/are the ignition feeds for it?  Everything I've done with an RPM/cylinder setting on the dragbike I've had to screw around with various settings until it reads right. 

Have you reconnected the blue wire?  Have you taken the red pill?   

[Dads_FJ]

First I would call tech-support like you are already doing.  But then when they shrug their shoulders I would incorporate a circuit like this which should double the trigger signal to the tachometer.  Assuming the trigger is from the negative terminal of a coil that is...

[FJ_Hooligan]

I forgot about the wasted spark.  Reconnecting the blue wire should double the pulses and give you the correct reading.

Sorry about that!

Edit:
But wait!  Upon further confusing myself about it, the 4-cyl mode should work.

We have 2 sparks per crank revolution (wasted spark but only using the signal from 1 coil).  That's the same number it should be counting for a 4-cyl engine without a wasted spark ignition.

Unless there's a defect in the unit and cutting the blue wire really didn't do what it was supposed to do.

Sorry, no help....

[FJ_Hooligan]

I hate being stupid.

The FJ only has 1 pulse per crank revolution given that the tach is only using 1 coil that operates as a wasted spark.

A typical (auto) 4-cyl ignition would see 2 pulses per rev (that's why it's reading half).  Reconnecting the blue wire will cause it to read half again as much. 

Dad has the proper solution, you've got to double the signal to the tach.

I'll stop now before embarassing myself further.....

[FJ_Hooligan]

Risking further embarassment....

I don't think it's as easy as connecting both coil ground wires to the tach line.  The coil fires in response to the ignition system breaking contact on the ground side.  This stops the flow of current through the coil and causes the secondary to discharge through the spark plug.

The tach is looking for an interrupt signal to register as a fire event.  Hooking both coils will provide a constant 12 volt signal to the tach.  When one coil loses it's 12 volts as a result of the ignition system breaking the circuit, the tach  will not see this because the other coil is still providing a 12 volt signal to the tach.

I'm not an electrical engineer, but I think both coil negative wires would need to be input to some kind of AND gate.  The output of the AND gate would go to the tach.  This output signal would be interrupted whenever either coil fires.  That would provide the correct number of interruption signals for the coil to count as firing events.

[aviationfred]

I tried wiring the tachometer like Dads_FJ diagram. No change in the rpm's. 

My next avenue to wander down is to connect the tachometer signal wire to the grey wire coming from the Coil Pick up to the Igniter.

Fred