4 electrode spark plugs

Nov 12, 2010 5 Replies
A

Hi



When servicing my Rover 25, I got seduced by the blurb surrounding 4 electrode SPs and decided to fit some.



The starting had gradually become more problematic, eventually taking a couple of turns of the key each time, to successfully start.



Initially I changed the fuel filter, knowing it hadn't been done, but then reverted to a new set of the correct plugs when that made no difference.



The next morning the starting was just as hesistant but since then it has been fine.



My question is, could this initial problem have been caused by the ECU re-adjusting it's settings or am I assuming an early ECU is far too clever ? I'm just interested why there might have been this initial delay in reverting to normal starting.



FWIW I came across this on the

formatting link
site.
formatting link
"From our experience and testing we know tha multi electrode spark plugs require more voltage to make a spark and do not run as smooth as normal small diameter single electrode spark plugs. This is also because the 3 or 4 electrodes block the beginning flamefront and flow around the spark area.The secret t improved ignition performance is mainly a thin centre electrode."



Cheers Andy C


Vote
Twitter Facebook LinkedIn
T

Does your 25 have coil on plug, or dizzy & rotor arm?

Tim.

Vote
Twitter Facebook LinkedIn
D

When 3 electrode plugs first came out about 20 years ago, (Shitfire I think they were called) and claimed as being a performance item the local rolling road started seeing them appear on modified engines. In back to back tests they regularly "reduced" power by a measureable amount over conventional plugs! I agree it's down to shrouding of the flame front because the centre electrode is almost completely surrounded by chunks of metal.

You ideally want the spark to occur in as open a space as possible so it can quickly propagate to the adjacent fuel/air mixture and spread through the chamber. Exactly what you get with a single side electrode and also a thin central electrode.

Even with single electrode plugs the most fastidious race engine builders try to select individual plugs so that when tightened the electrode gap points in the optimum direction to propagate the spark. It might only make a further miniscule difference to performance but it's a recognised procedure.

Vote
Twitter Facebook LinkedIn
D

"Dave Baker" wrote

Alfa Romeo used to specify Golden Lodge plugs with 4 electrodes back in the 70's. I reckon conventional NGKs worked better on my Alfasud.

Vote
Twitter Facebook LinkedIn
M

my alfetta had them in when I got it, not for long though, I put in NGK and they stayed there till I sold it in 1979, and the new owner wrote it off on an ice covered road.

Vote
Twitter Facebook LinkedIn

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required