Tachometer issues..

[andrecht]

Badlandbuggy 750cc Tachometer issues..

I have just installed a Tachometer into my Badland buggy..
I'm running a GS750cc Suzuki engine with dual coils.

Not realizing at the time of buying the rev-counter (tacho), it is made for a single input from a single coil..
My common sense tells me that if i run both (-) negatives ti the coil, ill be bridging the outputs from the CDI, and create both coils to ignite at the same time....

I was thinking the only logical way to overcome this problem is to install Diodes on the feeds to the tacho.......

Any comments?

BTW...
Here is a video of the test run..

www.youtube.com/watch?v=-Zyh3Z6Xj10&feature=c4-overview&list=UUvt_2Of4tpOp5_mjy1tXCkA

 

[itsid]

what?
just attach it to one ignition cable and you should be good.

A one cylinder engine has an ignition every second revolution
(tacho counts ignition and multiplies by two)
A two cylinder engine has one ignition per revolution
(count one cylinder ignition and your perfectly good)

if you count both ignitions you'll have a false rpm reading (twice the actual rpm)

'sid

 

[andrecht]

The 750cc is a 4 cylinder engine with 2 separate coils.... 2 and 3 is fed from coil A 1 And 4 form coil B, thereby I'm only getting half the cycle pulse.....

 

[itsid]

So,
again: you only want half the cycle, because all single cylinder tachs multiply by two to show the rpm (they have to)

and it almost doesn't matter as long as one single cylinder of your engine is ignited every second revolution you only want to count this ONE cylinder with your tach to get the correct reading.
The more cylinders an engine has the more complicated it get's, but in your case it's rather easy..
Your coils will fire alternating, ababab... every second revolution coil A.. so instead of one cylinder read one coil.
just read coil A and you're good.

with 6,8,10,12 cylinders you'll run into problems, maybe even on single ignition coil 4cyl. engines(like most cars have), but that's not applicable here

'sid

 

[andrecht]

Sid

Maby you misunderstood

The Autogauge Tacho meter is a standard unit made for 4 or 6 or 8 cylinder engines designed for single coil ignition systems.....
The single coil fires 4 times per cycle..
Assuming having two coils, one coil will only fire twice per cycle, thus only giving me a half pulse per cycle....

Am i missing something?

 

[OzFab]

Being a dual coil setup, it would be controlled by a module of some description wouldn't it? You need to locate the tach output on the module...

 

[firemanjim]

Uhhh, wont that engine hit more than 8 grand ? Its more like 14 or 16 grand with a red line area around 12? That tach might not work, period...... But what if,.... You only hook up to 1 coil and then multiply by 2 to get real rpm.... Is that right , 'sid?

 

[itsid]

Uhhh, wont that engine hit more than 8 grand ? Its more like 14 or 16 grand with a red line area around 12? That tach might not work, period...... But what if,.... You only hook up to 1 coil and then multiply by 2 to get real rpm.... Is that right , 'sid?

well, the GS750E is a cruiser, not a racer; 8k is below it's max rpm but within it's cruising speeds I think
IIRC it's max rpm is 9k (well.. red line)

and yes, just one coil and multiply by two is what I would do
(I'd change the dial to ease the pain )

Sid

Maby you misunderstood

The Autogauge Tacho meter is a standard unit made for 4 or 6 or 8 cylinder engines designed for single coil ignition systems.....
The single coil fires 4 times per cycle..
Assuming having two coils, one coil will only fire twice per cycle, thus only giving me a half pulse per cycle....

Am i missing something?

Ah, I did... by "single input" I though you were talking about a single cylinder single coil setup, not a four cylinder single coil one.

In that case you're right, measuring just one coil will give you only half the rpm.
So, just as Fabroman said.. use the common ground wire from the contactor plate for the pulse.

AFAIK you have two orange wires (one per coil) to the contactor plate, and the common ground should be white I think... uhm... I hope

'sid

 

[andrecht]

Fond this on the net..

Comments?

 

[andrecht]

Anybody?