Fiat Dino Forum (FDF)

Guys
The Dino is back from the workshop with most faults sorted and it is feeling great. I think there is still a lot more to come from the engine. I am going to have the Dinoplex internal replaced by Superformance because I do not have the original coil. Apparently the car is only running on one set of points and several people have told that this is fine which begs the question of why they are fitted with two in the first place? What is the role of double points? How much more performance should I expect getting the faulty Dinoplex sorted and fitting correct double points? I haven't driven another Dino so I don't have a reference point but it does not feel very smooth.
Regards
Rob

The two ponts are to ensure ignition also on very high revs: two points with three lobes on the distributor cam.

With the Superformance conversion there is not much difference (if any) between your current points based setup and the conversion, both are a standard inductive setup with the same coil current. Would recommend to either get a MSD 6A/Blaster 2 coil setup or a high power transistor ignition setup for the Dinoplex conversion.

You might also want to make sure that your fuel pump is fine, that distributor is working properly (ignition advance) and that the carbs are clean and correctly jetted for best performance.

Good luck,
Adrian

Hi Rob,

I've been through this process with my spider over the summer. Poor running at high revs, hot start issues, etc. It took a while to get it properly sorted. You may need to look at the fuel side of the equation. Problems I had included (in order of severity):

• worn cams
• distributor needed rebuild - very common apparently due to being mounted horizontally
• intermittent fuel delivery problems (probably) - also common on Dinos. Fuel pipe gets crushed under tank. Fuel pumps can suffer from lots of issues including voltage drop when under load - though mine wasn't a problem.
• non-functioning Dinoplex

It now pulls strongly and cleanly into the upper rev range. Are you UK based? Send me a PM if you want to try and get our cars together to compare notes.

Hugo

ThomasK wrote:The two ponts are to ensure ignition also on very high revs: two points with three lobes on the distributor cam.

3 lobes 6 cylinders 2 contacts. I thought it used one contact for every bank..

Now I don't understand.. Could you explain a bit more?

Thanks.

What happens, unregardless of whatever breaker setup, is that your ignition coil needs to 'recharge' to store enough energy for every spark. It does this conventially while the contact breaker is closed, it discharges and generates a spark at the point the contact breakers open. The relation between the amount of time open and closed is called dwell or dwell angle.
This means at a conventional 6 cilinder the contact breaker has to open and close 6 times per distributor rpm to recharge and discharge the ignition coil to generate the 6 Sparks. That is a lot because at 8000 rpm it will open and close ((8000/2)*6) = 20000 times a minute. Because it will open and close so often (and we are talking about a spring loaded mechanical gizmo with a certain mass inertia and so on) you are running at a point where speed and inertia are playing such a role that exact timing, recharge and discharge time are not precise enough anymore.
By using 2 sets of contact breakers (and a 3 lobe cam), they use the point where 1 contact opens and the point the other closes to generate the dwell. This means ultimately that 1 contact breaker now is opening and closing ((8000/2)*3) = 10000 times a minute. Now the factors of mass and inertia play a significantly smaller role on dwell, timing and so on what makes it running more reliable, better or more precise on higher rpm's with double contact breaker setup.
Hope this is understandable

S125A/AX/BX has three cams and two sets of points, one for each bank.
S125C has six cams and two sets of points, a standard one "A" and a 5.5 degree retarded one for the emission control setup in later Ferrari Dinos.

http://www.dinoplex.org/#Marelli_S125

Keep in mind that dwell is not relevant for the factory Dinoplex (or MSD) setup, it is only important for the Emergenza setup.

Stefan2000 wrote:What happens, unregardless of whatever breaker setup, is that your ignition coil needs to 'recharge' to store enough energy for every spark. It does this conventially while the contact breaker is closed, it discharges and generates a spark at the point the contact breakers open. The relation between the amount of time open and closed is called dwell or dwell angle.
This means at a conventional 6 cilinder the contact breaker has to open and close 6 times per distributor rpm to recharge and discharge the ignition coil to generate the 6 Sparks. That is a lot because at 8000 rpm it will open and close ((8000/2)*6) = 20000 times a minute. Because it will open and close so often (and we are talking about a spring loaded mechanical gizmo with a certain mass inertia and so on) you are running at a point where speed and inertia are playing such a role that exact timing, recharge and discharge time are not precise enough anymore.
By using 2 sets of contact breakers (and a 3 lobe cam), they use the point where 1 contact opens and the point the other closes to generate the dwell. This means ultimately that 1 contact breaker now is opening and closing ((8000/2)*3) = 10000 times a minute. Now the factors of mass and inertia play a significantly smaller role on dwell, timing and so on what makes it running more reliable, better or more precise on higher rpm's with double contact breaker setup.
Hope this is understandable

Yes. I understand. I'm quite familiar with these terms, I've been tuning engines for some time, and I have also done some Megaskirt mapping. Now I realise that when I asked the question, I simply misunderstood the previous explanation.

Sorry for making you explain. It was a really good explanation anyway, it will help others.

Both your explanations are really good Stefan. So my understanding is and I may be wrong! that two parallel circuits each have a set of points grounding the coil through the condenser. So one set of points closed is all that's needed to charge up the coil. Both open to create the spark, the spark being created at the opening of the second set.
So the first set opens nothing happens but they stay open,
Second set opens she sparks
First closes coil recharges
Second closes finishing the cycle.
Each lobe is 120 degrees out therefore the first set need to come on cam slightly before the second set comes on the preceeding cam?

This probably sounds absolutely stupid to you