Coil Packs

[duncan]

Following from Jonathan comment on the potential to use the later OBD11 [3 pin] coil packs on earlier OBD1 [2 pin] cars.

i'm guessing the 3 wire OBDII coils have a pair of coil supply wires and a sense wire whereas the OBD1 have just the pair of coil supply wires... just thinking if the mountings are the same that a set of 6 adapter wires can't be too difficult to make....



I wondered the same; simply snip off the 3rd pin and have some sort of piggy back connector between them, HOWEVER, the polarity of the spark seems different. See the two attached pdf's.

Assuming the low tension side A and B have the same polarity [effectively the CB and SW terminals in old money], the spark will jump in a different direction as the diodes have opposite polarities.

My questions are, am I correct, does this matter and will it it work.

In the days of my youth I ran a Citroen 2CV; the 2CV used a twin ended coil with all [both of the 2] cylinders firing at the same time, the respective sparks jumped in different directions. The spark plugs eroded at different rates.

[britlude]

those were the diagrams i was going to hunt down!

as far as i know the direction of the spark can't be that critical, as pretty much every ford with coilpacks has half the sparkplugs firing the reverse direction with the wasted spark system.

more investigation required!!! :)

[Hagasan]

Had a look at this and from what the manual suggests...The OBDI Terminal A feed comes from the main relay and Terminal B from the Igniter Unit. The secondary winding terminal would be to the spark plug.

On the OBDII it would appear the same in that A is from the Main Relay and B the Ignition Control Unit with the secondary winding terminal again going to the plug. The extra terminal on the other side of the capacitor goes off to the Plug Voltage Detection module.
From what I can surmise this would appear to be an enhanced misfire detection set-up to further tighten down efficient fuel burn/emissions or at least highlight the slightest hint of an emission problem that would have, in previous years, not been so critical?

I think the diode direction may be a red-herring as the spark can and will only be going one way, to the plug. Maybe just a diagram glitch?

I know the plug part numbers are different between OBDI & II but I don’t know if there are any physical differences in length and or the top diameter the coil fits on to?

All things being physically the same, the resistance specs are, I can’t see why these couldn’t be used but the un-terminated terminal downwind of the capacitor output… how do you discharge that and if not, will it damage the coil? OBDI doesn’thave the plug voltage detection module......

It seems strange that if it was as easy as adapting a connector then fitting that none of the Yanks have done this with the huge price differential….

I guess I haven’t really helped here, just raised a few more questions:D

[duncan]

Different plugs?
From the various factory manuals the grade of plug is given in the Maintenance Schedule and under Engine Electrical. Comparing the early cars to later, all years are quoted with the same ND plug PK20PR-L11; for NGK up to 1996 the reference is PFR6G-11, then for the remaining years the 'Engine Electrical' specifies PRF6L-11, however the Maintenance Schedule contradicts this for 2004 and 05 and reverts to PFR6G-11.
Answers?

[britlude]

for NGK this might this help.... though as it doesn't distinguish the G and L firing end construction it might not....


http://www.sparkplugs.co.uk/graphics/tech/ngk_sparkplug_symbol_key.gif

[NSXGB]

http://www.ngksparkplugs.com/docs/tech/design_symbols_plugs.pdf

Firing end construction:
G = Fine wire nickel alloy Centre electrode.
L = Medium heat rating ( if -L ? )