TS spark plug timing

[GTVeloce]

I noticed last night that my two dizzies don't appear to operate on the same timing. The primary dizzy runs the usual 1-3-4-2 timing but the secondary dizzy runs differently! The car runs fine except for a very faint non-steady idle. I have tried looking through all my documentation but can't find anything about this.

Thoughts people? Will there be any harm if I try and run them in the same order?

[Darryl]

It should be same firing order/timing on both. That said, I picked a 75 TS up from a seller in Sydney and was driving it back to Bris and noticed it would get rough under load and revs (both, didn't seem to mind one or the other). When I got it back to Bris and checked it over I  found a pair of leads swapped. Easy to do and as it runs it is possibly not immediately obvious (depending on just how wrong the firing order/phase is)?

[festy]

The two pins on the ECU for the ignition modules are joined internally - it fires them both together with the same dwell, timing etc so they should be set up identical.
The ECU doesn't actually "know" there's two coils.

[GTVeloce]

Thanks guys. I swapped them over (there were just two that were around the wrong way) and to be honest it didn't seem to make much of a difference. However, I also suspect the throttle switch is not set properly (it doesn't click when just opened) so that could also be making a difference.

[Beatle]

I can't recall, but does the dizzy fire each plug one-in-four strokes, or does it fire on each upstroke (one-in-two).  If the latter, that may explain how you can have a lead incorrectly fitted but it still runs OK.

[festy]

My theory on this is that as long as one of the plugs in each cylinder fires at the correct time, having the other plug fire out of sequence may not have a big impact (if it fires on the exhaust stroke, for example).
The fuel is burnt by the correct plug firing, so won't ignite while the exhaust valve is open like it would with a "normal" monospark engine.

[Darryl]

What festy says - it would be much like a "wasted spark" setup firing the alternate cylinder on exhaust - the bigger problem could/would be if the leads were out of "phase" such that it fired on inlet stroke? I can't actually remember / didn't check what exactly the timing I had on the car I mentioned was but it was while trying to diagnose the iffy feel under load + revs that I resorted to pulling leads and that lead to the culprit rather than a visual check (just as well given my cross-eyedness documented in another thread  ). You can pull any one lead on a twinspark and, unless the other one/the other plug is stuffed or in the wrong place, you won't notice much of a difference. It also means you can have a stuffed dizzy rotor on one dizzy and not notice for a while, although it certainly doesn't do the cap any favours...

I've also been told by a tuner that the actual impact on performance of running a single plug (in effect, by firing second one on exhaust) vs correctly timed twin spark can be pretty small (or non existent or negative on at least on one, modified, engine).

[GTVeloce]

It is interesting you mention the dizzy cap Darryl as I noticed the cap in question was looking tired (a kind of green tinge at the contact points) that I don't recall last time I looked. I thought I had replaced both caps recently although I may be getting confused with the other car.