Alfa Romeo Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
2,777 Posts
Discussion Starter #1
Hi alfa fellas!

Today just made an interesting test. You know CF1 and CF2 TS engines link to spark plugs in a strange way. Each one drives 2 spark plugs on 2 different cylinders. The 2 first coils run the 4 primary spark plugs, and other 2 run the secondary. On CF3 TS engines each coil runs th 2 spark plugs on the same cylinder, the more logical option.

I have a CF2 engine, so I switched leads from coils 2 and 3, making each them run the 2 spark plugs from their own cylinders, like in the CF3 engine. Coils 1 and 4 left untouched cause lead from coil 4 can't be taken out with removing the coil pack plate...

Well, started the engine, no problems, no ECU faults, but just on idle.

What do you think about this? Prognostics? Any benefits on performence? Disavantages on coil usage, misfire?
 

·
Registered
Joined
·
37,360 Posts
I wouldn't mind betting that you will notice no difference whatsoever.

That is providing the plugs, leads and coils were good to start with.
 

·
Registered
Joined
·
2,777 Posts
Discussion Starter #3
And about the coil stress feeding the plugs? Is it the same? Spark quality?

Also related, the spark plugs in the same cylinder are then fired at the same time, or like before switching the leads?
 

·
Registered
Joined
·
37,360 Posts
From what I gather both plugs fire at the same time, and they do this on both the compression and exhaust strokes as it is a "Wasted spark" system.

I think both versions work the same in terms of when the sparks occur, it is just they are wired so that the small plug is paired to the large plug on a different cylinder.

I am sure there is a better explaination the net somewhere. :)
 

·
Registered
Joined
·
37,360 Posts
The way I see it is that in a normally aspirated engine like a TS power is limited by the amount of air that can fill the cylinders. This amount of air is then mixed with the correct amount of fuel and ignited by the plugs.

If the pair of plugs were not already igniting the fuel properly then you would have running and emissions problems.

If the car is already running properly then you will see no difference.


I would say that only by increasing the amount of air and fuel going into the engine are you going to get any noticeable increase in power.
 

·
Vendor
Joined
·
45,305 Posts
You can fit CF2 coilpacks to a CF3 and vice versa, seems to make no noticeable difference to how they run. You can't swap CF1 with either CF2 or CF3 but only because the plugs on the tops of the coilpacks are different. If you change the plugs on your engine loom then you can use CF2 or CF3 coilpacks.

Because its a wasted spark system as Symon says then it doesn't make any difference which coilpack fires the plug. If anyone does notice a difference after changing its probably down to a coilpack being a bit duff to begin with.
 

·
Registered
Joined
·
2,777 Posts
Discussion Starter #8 (Edited)
I think there's a lot of misinformation about this on the web. These are my thoughts...

On a CF2 TS engine coil 1 fires both primary spark plugs on cylinders 1 and 4.
Coil 4 fires both secondary spark plugs on cylinders 4 and 1.

Firing order is 1-3-4-2

So, cylinder 1 primary spark plug is fired by coil 1 at 0º crank rotation at beginning of power stroke. Coil 4 is firing secondary plug on cylinder 4 at the end of exhaust stroke.
cylinder 3 primary plug is fired 180º after cylinder 1 primary plug
cylinder 4 primary plug is fired 360º after cylinder 1 by coil 1, the exact same moment at the end of exhaust stroke on cylinder 1, when coil 4 fires secondary plug on cylinder 1.
So, switching leads of coils 1 and 4 with have no practical effect. Both coil will still fire 2 spark plugs 360º fased out on crank rotation. This is the same switching the leads of coils 2 and 3.

The only advantage I can think on this configuration is that a cylinder is serviced by 2 coils, and on a coil failure, cylinder still runs. Runs much better if only the coil firing the secondary plug fails. Harder if primary fails.
Disavantage, it's harder to diagnose a failing coil pack, specially the ones only running secondary plugs.

Edited text in bold.
 

·
Registered
Joined
·
30,019 Posts
As I'm sure I've said before, I've long suspected that the reason for the change was just to save a few Euros on the amount of HT cable needed on each car...
 

·
Registered
Joined
·
2,777 Posts
Discussion Starter #10
Strange is why alfa did not opt for this later more obvious and cheaper option in the first place...
 

·
Registered
Joined
·
37,360 Posts
From what I can see, on the newer setup if a coilpack fails you loose one cylinder.

If you loose a coilpack on the earlier system the engine will still run ok, but you will lose one of the twin sparks.
 

·
Registered
Joined
·
565 Posts
On a CF2 TS engine coil 1 fires both primary spark plugs on cylinders 1 and 4.
Coil 4 fires both secondary spark plugs on cylinders 4 and 1.
er....no...

On my CF2, Coil pack 1 (nearest cam belt) fires Primary 1 and Secondary 4, coil 2 fires primary 2 and secondary 3, coil 3 fires primary 3 and secondary 2 & coil 4 fires Primary 4 and secondary 1
 

·
Registered
Joined
·
2,777 Posts
Discussion Starter #14
Hi, just an update! Just made the complete CF3 conection conversion. Two lambda fault codes (p1030 and p0170) never reapeared after being reset. The same when I had the original CF2 conecction and unplugged coil packs 3 and 4, disabling the secondary plugs. I must be having issues with coil packs, but the CF3 like linkage could be a workaround...

Also, some people think the secondary plugs are doing nothing or not much. Try unpluging coil 1 and 2 on a CF2 engine, disabling primary spark plugs. The engine will start and run, bad, but will. So, secondary plugs are doing something ;)
 
1 - 14 of 14 Posts
Top