75 Twin Spark after market tacho

[alanm]

Hi all

I would like to install a (discreet) aftermarket tacho in my 75 Twin Spark and I was wondering if the installation is complicated by the fact that the car has 2 coils and 2 distributors?

Does it matter which of the 2 coils you connect to?

I gather that the two sparks on the 8V TS engines do not fire at exactly the same time, but they presumably fire at the same speed?

Any information much appreciated!

Cheers
Alan

[festy]

Just pick up the tacho signal from one of the ignition modules, I don't think it matters which one.
The ECU provides the same advance and dwell to both modules and they appear to be both fired at the same time, because the two ignition pins are joined together inside the ECU.

[Paul Gulliver]

Thanks Festy, Now back to that important work your doing with the Motronic tuning over on Alfa BB.

http://www.alfabb.com/bb/forums/engine-management/190352-what-stock-75-ts-motronic-can-cannot-do.html

Bump: For anybody with a twin spark motronic this is very exciting news worth reading the whole thread & the work Festy is doing

[alfagtv58]

Thanks Festy, Now back to that important work your doing with the Motronic tuning over on Alfa BB.

http://www.alfabb.com/bb/forums/engine-management/190352-what-stock-75-ts-motronic-can-cannot-do.html

Bump: For anybody with a twin spark motronic this is very exciting news worth reading the whole thread & the work Festy is doing

WOW!  Thanks for the heads up Gully!  It's all above my IQ level, but I will go back and try to read it later on when I can actually concentrate on it.

[Paul Gulliver]

It's all above my IQ level, but I will go back and try to read it later on when I can actually concentrate on it

Phil,

I'm only just hanging on with  that thread. Your kids are probably a bit young but teenagers should be able to help.

[BradGTV]

im a teenager.. some bits are still comfusing 

[Henry Goodman]

I'm waiting for the summary in plain english.

Oops I off topic on this thread - sorry.

[alanm]

Hi all,

Completed the install over the long weekend, thought I would share some learnings...

Photo 1 shows the rear of the fuse box with accessory power terminal circled (fuse 10).

Photo 2 shows the white wire which connects to the negative terminal on the coil.
Alfa/Bosch conveniently supply this with a male connector. Your choice of coil, on my car the factory tacho (brown/white wire) is connected to the coil on the left of the shot.

Photo 3 shows a row of male connectors earthing to the front of the car right behind the headlight, once again Alfa conveniently supplies 2 spares (lower row)

Photo 4 shows the installation of the Speco tacho to the windscreen frame (no holes in dashboard!).

I only needed to drill 1 x 7.5mm hole in firewall right behind the fuse box to pass wires into the engine compartment, this was finished with a rubber grommet.

Cheers
Alan

[alanm]

A SMALL  BUT IMPORTANT ADDITION TO THIS POST.
I got an erratic tacho reading until I installed a 1N4004 diode between the coil and the tacho (make sure you install the diode facing the right direction, band facing the tacho).
Al

[Colin Edwards]

Problem rectified!

:-)

[GTVeloce]

Alan, your engine bay looks far too clean and tidy! You need to drive the car more!!