Volvo multi-ground spark plugs - why?

KevinMalone

KevinMalone

Joined
Sep 2, 2016
Messages
628
Any ideas why Volvo would specify a multi-ground spark plug (Beru Ultra Nickel Z204) for the naturally aspirated B5244S on P2 models (and possibly others), while turbo engines in the same platform get platinum spark plugs (Bosch FR7DPP)? All engines use the same ignition coils as far as I know.

Volvo enthusiasts claim that the naturally aspirated runs best with the OE multi-ground spark plugs but does it actually matter? I have read that the multi-ground plugs are supposed to maintain specified gap for a longer service interval. However, I've seen the center electrode on these wear down to triangles in just 50k km, which is consistent with the expected service life from a nickel plug. It would be nice to use longer lasting double platinum/iridium spark plugs if possible.

1704698346304.webp
 
Those look just like the Auburn tc3 plugs I ran in the 70s....Remember the fire injector plugs from JC Whiteney in the 50s and the 60s...nothing new in spark plug design...
 
BMW came out with similar plugs at one time, they called them "high power" or Longlife and these are the reasons they gave:

All models
Situation: "Longlife" spark plugs have for the first time been approved for the start of series production of the new 3 Series E46. As of Model Year 1999, all other BMW models will also be equipped with these spark plugs. Moreover, these spark plugs can also be used with immediate effect in certain engines (see retrospective approval). The new spark plug has the following design features:
- Four earth electrodes
- Centre electrode with platinum plate
- Semi-surface discharge technology
On semi-surface discharge spark plugs, the electrodes are designed in such a way that the spark will always slide over the insulator before it flashes. This prevents sooty deposits from forming and so pre-empts misfiring. The spark always flashes at the point on the electrode which will give the best combustion conditions. In this way, the electrodes will wear evenly throughout the service life of the spark plug. The platinum plate on the centre electrode is highly resistant to spark erosion.
This design allows operation to be maintained consistently at an optimum level for the entire service life between the change intervals.
Benefits of semi-surface discharge technology:
- Outstanding cold-start performance.
- Improved combustion characteristics, providing for higher idle quality and better acceleration performance.
- No misfiring on load change or full load.
- Maximum ignition reliability, even in extreme short journeys or in stop & go traffic, protects against damage to the catalytic converter.
- Consistently high level of operation throughout the entire service life.
- Up to double the service life, depending on the model.
- High degree of safety reserves when vehicles are run under difficult operating conditions.
Click to expand...
 
I'm >20 years on 3 consecutive P2 Volvos which use that plug; all with the B5244S base engine as stated by the OP.
No trouble with those plugs or any of the coils.

NOTE: A few posters on Volvo boards described the coils as "trouble prone". An online parts rep from a Texas dealership told me (of the coils), "We stock 'em and I've never sold one".

Ha, maybe the people with coil troubles were using conventionally styled plugs.

I welcomed the "French 5-pack" as they were always available and obviated plug selection.

What caught my attention was the huge selection of plugs for the turbocharged engines.
 
kschachn said:
BMW came out with similar plugs at one time, they called them "high power" or Longlife and these are the reasons they gave:
Click to expand...
I think those triple electrode plugs were used longer than the E46 - my 1991 E30 M42 (1.8L 4 cyl) used them too. Couldn’t easily find them so most folks went to dual electrodes…

Here is an brochure on them, from Autolite’s position:


Doesn’t give much concrete, not sure if flame kernel speed is really materially different in the photos shown, but that was as I recall, rationale against too many ground electrodes.

I don’t think the concept of it being a “spare” electrode really works. I think there is something to be said about offering multiple paths so the best one can be taken given the mixing environment.

IIRC, some engines specify that spark plugs be “clocked” with the ground in a certain position. Maybe it was @The Critic that mentioned that?

Ive done work on dielectric breakdown, arcing, etc. and certainly the local chemical makeup can affect the ability for an arc to form, and extinguish. So having the two electrodes in the right point to allow the mixture, in its movement pattern, to proceed is important…
 
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I use the OE multi ground plugs in two family vehicles.

There are many posts on Volvo sites to use OE only. People who have tried other types report issues.

In my experience the OE plugs work extremely well at a modest price.
 
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My takeaway from the Autolite article is all that electrode material quenches the flame, much like the backfire flame arrestor in old air filters of carburated engines.
 
Pepe Silvia said:
Any ideas why Volvo would specify a multi-ground spark plug (Beru Ultra Nickel Z204) for the naturally aspirated B5244S on P2 models (and possibly others), while turbo engines in the same platform get platinum spark plugs (Bosch FR7DPP)? All engines use the same ignition coils as far as I know.

Volvo enthusiasts claim that the naturally aspirated runs best with the OE multi-ground spark plugs but does it actually matter? I have read that the multi-ground plugs are supposed to maintain specified gap for a longer service interval. However, I've seen the center electrode on these wear down to triangles in just 50k km, which is consistent with the expected service life from a nickel plug. It would be nice to use longer lasting double platinum/iridium spark plugs if possible.

View attachment 197248
Click to expand...
My 1998 Audi A4 with 2.8 came with a Bosch 4 electrode plug that ran better and you could feel the power difference at higher RPM. My seat of the pants dyno would say it had to be at least 5 hp more to have been noticed. As time went on I had to hunt for 3 or 2 prong equivalents. The car would run smooth on a platinum single ground plug but Bosch or Beru multi-grounds with copper cores ran best. It must have given it better combustion. I also found that clocking the grounds on a single or dual ground made a difference. Oddly enough I never found any plug that was lasting in that engine even past the factory change intervals but that may have been due to the 5 valves per cylinder high compression design.
 
JHZR2 said:
I think those triple electrode plugs were used longer than the E46 - my 1991 E30 M42 (1.8L 4 cyl) used them too. Couldn’t easily find them so most folks went to dual electrodes…

Here is an brochure on them, from Autolite’s position:


Doesn’t give much concrete, not sure if flame kernel speed is really materially different in the photos shown, but that was as I recall, rationale against too many ground electrodes.

I don’t think the concept of it being a “spare” electrode really works. I think there is something to be said about offering multiple paths so the best one can be taken given the mixing environment.

IIRC, some engines specify that spark plugs be “clocked” with the ground in a certain position. Maybe it was @The Critic that mentioned that?

Ive done work on dielectric breakdown, arcing, etc. and certainly the local chemical makeup can affect the ability for an arc to form, and extinguish. So having the two electrodes in the right point to allow the mixture, in its movement pattern, to proceed is important…
Click to expand...
Electricity always takes the easiest path.
 
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Thanks for the input so far. I'm no smarter than the engineers at OEMs so I usually don't deviate from whatever is OE, but could the ignition system actually be "designed" for multi-ground plugs?

It seems like multi-ground plugs were "ancient tech" to extend service life before precious metal plugs became more common. In addition to the above bulletin from Autolite, here's a Denso engineer claiming multi-ground plugs are for longer service rather than performance: https://www.denso-technic.com/hu/what-do-technicians-need-to-know-about-spark-plugs

Can a multi-ground spark plug be replaced by a single-ground spark plug?


PS: “A multi-ground electrode is preferred by some engine manufacturers and VMs because of the extended lifetime of the additional ground electrodes. Extending a spark plug’s service interval, without the use of precious metals, is a very cost-effective solution.


“Multi-ground spark plugs are designed specifically for long life rather than performance, but replacing a multi-ground spark plug with a single ground spark plug will improve performance, at the sacrifice of reduced service life.


“Upgrading a multi-ground electrode spark plug to a long-life iridium spark plug, like the DENSO Iridium TT, however, will combine both performance and durability.”
Click to expand...
 
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JHZR2 said:
I think those triple electrode plugs were used longer than the E46 - my 1991 E30 M42 (1.8L 4 cyl) used them too. Couldn’t easily find them so most folks went to dual electrodes…

Here is an brochure on them, from Autolite’s position:


Doesn’t give much concrete, not sure if flame kernel speed is really materially different in the photos shown, but that was as I recall, rationale against too many ground electrodes.

I don’t think the concept of it being a “spare” electrode really works. I think there is something to be said about offering multiple paths so the best one can be taken given the mixing environment.

IIRC, some engines specify that spark plugs be “clocked” with the ground in a certain position. Maybe it was @The Critic that mentioned that?

Ive done work on dielectric breakdown, arcing, etc. and certainly the local chemical makeup can affect the ability for an arc to form, and extinguish. So having the two electrodes in the right point to allow the mixture, in its movement pattern, to proceed is important…
Click to expand...

NGK has a similar comparison of flame kernel growth to promote the PSPE ground electrode on their Ruthenium plugs: https://ngksparkplugs.com/en/products/ignition-parts/spark-plugs/ruthenium-spark-plugs
1704735655374.jpeg


Merc, and possibly others, require spark plugs to be indexed on their DI engines: https://mbworld.org/forums/attachme...ark-plugs-226-278-157-spark-plug-indexing.pdf
article_4d410cafc58867a59635f3a3ee2d475b343f5117_ec877ed323e280961ddfe2079bd1df661632ffa2.png
 
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For Volvos, and I own five P2 at the moment, I go with genuine Volvo plugs. Always. Other brands have been hit or miss.

They just work better. FCPEuro has good prices.

Why this style? No idea. But if they work well, I’m not going to deviate from my recommendation.

The coils last a long time.

Don’t goop antiseize all over them. I’ve had to clean quite a few plug threads as a result of over eager antiseize application.

Clean threads. Volvo plugs. Torque to spec. Done.
 
JHZR2 said:
I think those triple electrode plugs were used longer than the E46 - my 1991 E30 M42 (1.8L 4 cyl) used them too. Couldn’t easily find them so most folks went to dual electrodes…
Click to expand...

When introduced, the BMW four- and six-cylinder gas engines (M4x, M5x) that would serve in the 90s were equipped with what NGK called the "Delta" plug. There was also a Bosch equivalent.

BMW referred to it as a "platform" plug. They were so called because they had a lot of structure in the combustion space; essentially, like a mini triangular stool plopped on top of a typical spark plug.

Can't find pix online of the NGK plug, and I don't know where my NGK catalog where is was featured on the cover is located, to illustrate, but I did find a pic of the Bosch version:

Zündkerzen F03DAR Bosch Super

Zündkerzen F03DAR Bosch Super
zuendex.de zuendex.de

The NGK version was a bit more sharply defined, and also had three holes in the triangular "platform" above the center electrode.

In fact, those plugs served only for a short tenure, and were quickly phased out after a couple years, due to fouling issues under certain conditions (extended idling, short trips, urban driving) in favor of a more typical dual electrode plug, the BKR6EK. It wasn't happenstance that those platform plugs disappeared. They were a failure.

The Bosch equivalent of the BKR6EK was the F7LDCR, but not as common, either OE from the factory, or as replacement parts. By the time the M60 V8s were introduced, this plug was standard, so it never got the oddball plug like the early M50s and M42s.


It wasn't until 1999 that the quad-electrode single platinum ("High Performance Platinum Spark Plug") 100k-mile plug was introduced, and also approved for use with the older engines. It was known as the BKR6EQUP, and very similar to the Audi plug pictured above.


The passage quoted above comes from a BMW TSB noting their introduction:


I used both types, and given the cost difference between the dual- and quad-electrode plugs, there was a strong argument to just use the cheaper plugs and replace them more frequently. Not a difficult task, and some prefer to not leave plugs in for extended periods anyway. And no real perceptible performance difference either.

And while I'm not going to wade into the debate in the other thread about gapping multi-electrode plugs, I will note that BMW refers to them as "non-adjustable," and does not specify a gap.
 
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