Club 80-90 Forums

Hi,
Purchased some new plugs, Bosch, and prepared to set the gap to 25000" (for lpg) but the feeler gauge slid thro with some resistance as per usual so left them as they were.
Then noticed that the box said they had already been set to 28000".
My point being I measured gap as 25000" but the manufacturer said they are 28000". Should one 'struggle' to pull the feeler gauge through ie a real tight fit or should it just have some resistance. What do you do?

You asked 'what do you do?' Well, I use the triple electrode plugs that don't need the gaps set.
But if I were setting the gap, it would be somewhere between tight and loose. Just a bit of resistance.

LPG does not like multi electrode
don't worry too much about the difference 1mm is 25 thou and fine.
if they are more just tweak them in a bit by pushing on a bit of wood while the feeler guage is in

itchyfeet wrote:LPG does not like multi electrode
don't worry too much about the difference 1mm is 25 thou and fine.
if they are more just tweak them in a bit by pushing on a bit of wood while the feeler guage is in

That is interesting to hear, any explanation why, I can not understand why & would have thought a spark is a spark.

yes but with multielectrode you get three spartks not one.

no experience myself I took the advice at the time and fitted single electrode for my LPG, multielectrode is a gimmick anyway.

Jeff J wrote: That is interesting to hear, any explanation why, I can not understand why & would have thought a spark is a spark.

A spark is not just a spark - you can have small yellow ones (bad) or big fat blue ones (good).

Everyone said don't use triple Latrobe plugs with lpg, but I did for years , no terrible thing happened, and it ran very well, and then it suddenly became a bad thing .....

itchyfeet wrote:yes but with multielectrode you get three spartks not one.

no experience myself I took the advice at the time and fitted single electrode for my LPG, multielectrode is a gimmick anyway.

Taken from the NGK website regarding multi electrode plugs

Why have spark plugs with multiple ground electrodes?

Every time the plug sparks, minute particles of material are worn away from the electrodes. This phenomenon is called spark erosion. This continuous process over time increases the spark plug gap between the centre and the ground electrode. If the gap becomes too large, misfiring will occur.

In order to extend the service interval of vehicles, the service life of the spark plug must be increased. Some manufacturers are fitting multi electrode spark plugs as original equipment to achieve this. Multi electrode spark plugs can have two, three or four ground electrodes depending on the service life requirement of the manufacturer.

Do multi ground electrode spark plugs provide simultaneous sparks to each ground electrode every time the plug sparks?

No. No matter how many ground electrodes the plug has, every time the spark plug fires, only one spark occurs between the centre electrode and the ground electrode which has the lowest required voltage or the least distance to travel between the centre and the ground electrode.

I was working in a VAG dealership around the time that Transporters (and others) went from single to double & triple electrodes. The change was simply to extend service intervals/lower service costs and maintenance.
The outer three electrodes on these plugs are curved so setting the air gap in't really practicable and they are definitely pre-set bigger than recommended by VW so that's a bit of a contradiction I would say.
Recommended air gap on petrol is 0.7mm for a wasserboxer.
Recommended air gap on LPG is 0.6mm (ask Steve Shaw Gasure or Andy at Camper Shack)

Recommended plug when using gas (according to Bosch) is the single electrode 'platinum' W7RDP. This is a LONG LIFE spark plug so will last 2 - 3 times longer than that of a WR7DC (single electrode copper core) and has the benefit of better starting ON GAS.
Triple electrode plugs are getting harder to find now and have been replaced by super 4's .. I would still recommend the WR7DP on gas though... in fact I would recommend use of this plug on petrol as well.

http://www.ebay.co.uk/itm/4x-Bosch-Plat ... b4E3kiCnRg" onclick="window.open(this.href);return false;

Martin