Spark Plugs .028 versus .044?

poconosms1 · Post by **poconosms1** » 04 Feb 2019, 04:42

I just purchased a used 2010 XC90 with the 3.2l. Everything looked cleaned, no leaks, no rust, new tires, etc....

I decided to change the air filter and plugs. I found the dealer had replaced the air filter, so that was something good about the dealer.

I purchased champions platinum .044 on rockauto. It said they were pregapped, so I figured it should be .044.

When i pulled the old plugs, the gap was .028. I checked an online manual, which listed .028. Further research on internet found cases where owners pulled .044 gapped plugs from their motor even though their manual called for .028.

I searched a couple of online suppliers and found that for my year, model, and engine size, i can purchase either the .028 or .044. That makes no sense to me if the motors are all same.

Can I use the .044? Additional research indicated that you can get a better burn. I noticed carbon deposits on the current plugs, which I believe suggests too lean a mixture.

I was thinking of regapping the champions, but I know some higher end cars don't do well going down that road.

I'll probably return the champions and pick up the NGK Iridium or the Denso 5344

Looking forward to responses.

Thanks!

Post by **abscate** » 04 Feb 2019, 11:05

Use the manufacturer spec of 0.028

That gap spec is designed for the specific compression and coil voltage in the engine made by Volvo.

poconosms1 · Post by **poconosms1** » 04 Feb 2019, 11:28

So, the 3.2 motor actually has two different compression and/or coil voltage systems for the same motor? Mine has the tow package, could that be the reason that there are two different gaps?

thanks for replying.

Post by **pgill** » 04 Feb 2019, 14:53

This is just my $.02

I own two 3.2's

2010 S80 3.2
2008 LR2 3.2

Both vehicles have essentially the same engine.

In both I am using the Denso Iridium plugs.

For my LR2 I installed

Denso (5344) IKH20 Iridium Power Spark Plug at 50,000 miles

Denso (5344) IKH20 Iridium Power Spark Plug again at 100,000 miles

For my S80 I installed

Denso (5344) IKH20 Iridium Power Spark Plug at 125,000 miles (when I bought the S80)

The iridium plugs are very fine wire and the Voltage required to jump a gap from a fine wire is less than what is required for a large electrode.

Or to say the same thing the fine wire plugs can use a higher gap for the same voltage.

With this in mind the next time I change plugs I will be using

Denso (4704) IKH20TT Iridium TT with a .040" Gap

The TT (Twin Tip) has two fine wires.

My recommendation

Denso (5344) IKH20 - these have worked very well in my LR2 3.2 for the last 70,000 mile and are working great in my S80 3.2

Denso (4704) IKH20TT - if you are looking to upgrade

Here is the Denso website

http://densoautoparts.com/find-my-part. ... rchResults

If you only look at Iridium plugs then you have the plugs I listed above and a third choice

Denso SK20HR11 - this is what I removed from the S80

If you never want to change spark plugs again then the last choice is likely the best choice.

For me I'm changing mine at 50K intervals and I prefer the other choices

Good luck

Paul

bguzz · Post by **bguzz** » 27 Feb 2019, 18:38

I just pulled the original iridiums from my 2008 XC90 with a 3.2l. The iridiums were .044 and I replaced them with Denso 3381 copper plugs and gapped them at .044. That seemed to be the suggestion of Denso as well from their website. All seems good and the car runs very smoothly. I haven’t seen anything to suggest it should be .028.

Post by **abscate** » 28 Feb 2019, 03:56

If the Ir wire is what lets the gap get big then you shouldn't use the big gap for Cu, i think.

The car will run fine on new plugs for the first 5-10k miles, the question is what will happen down the road.

The user manual is the place to look this up, not the spark plug manufacturer. Volvo has all their user manuals on line for free , if you don't have one.

SIdebar - I run coppers on all my cars since I don't like plugs sitting in engines for 3-5 years, the Coppers are cheaper if I don't count my time (which I don't, as I change plugs on my compression test day).

Post by **jimmy57** » 28 Feb 2019, 08:06

Turbo engines use the smaller gap usually. The firing voltage requirement is greater for turbo engines as cylinder pressure increases ionizing voltage needed to get a spark to travel the gap. As gap increases the voltage also increases. Turbo engines with wide gap may require more voltage than coil and boot can tolerate for long w/o developing insulation fault. On non turbo the gap is larger as the cylinder pressure is less. The cam profile shifting of the 3.2 (other than the super low emissions versions where CPS is not used) causes more turbulence in cylinder so the extra gap width may not be as important for that reason. Wider gap ,1.1-1.2 mm(.044in-.048in) is consistently specified for the non-turbo engines if I look in a few pocket data books I have here, the turbo engines use the .7mm (.028in) gap and the V8 and 3.2 use the 1.1mm (.044 in) gap. The 6 cylinder turbo used in the P3 models uses the .7mm(.028in) gap. I think the info for the late 6 cylinder is muddled and the turbo and non-turbo gaps are confused in listings.

Post by **pgill** » 28 Feb 2019, 15:05

Bguzz,

if you are going to change the spark-plugs every year then the copper plugs should be fine.

Note: it is easier for the spark the jump from a fine point (Iridium plugs) or from a sharp edge (new copper plugs)

If you remove the copper plugs every 6 months and file down the center electrode (to get a sharp edge) and adjust the gap then you could probably use the same plug for 20 years.

Jimm57,

What you wrote is exactly the point.

The only caveat I would add is that depending on the boost of the Turbo the gap may not need adjusting as compared to the a naturally aspirated engine of similar construction. (or if you prefer the engineers did not bother to adjust gap because the engine worked as expected with the larger gap and a new part number couldn't be justified)

Example
2008 S80 3.2 (240 Hp) SK20HR11 Gap 0.44"

2008 S80 3.0T (300 Hp) SK20HR11 Gap 0.44"

2015 V60 3.0T (325 HP) FK20HQR8 Gap 0.32"

Here is a nice article about the V60 3.0T with 325 Hp https://www.caranddriver.com/reviews/a1 ... st-review/

Based on this information I am going to narrow the gap on my Audi 2.0T from .040" to .032" because I am not stock and I am well above 100HP/liter. (The style of plugs that I needed for the Audi only come with a gap of .040" from Denso)

Note: I am running the TT style plugs in the Audi and I will be using the TT style plugs for my next change on the S80 3.2 and LR2 3.2.

One last note if I buy a Volvo 3.0T in the future I will be using the FK20HQR8 Gap 0.32" even if I get the 300 HP version.

Take care

Paul

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