Page 1 of 1

White-ish scaling deposits on spark plugs, 2.0 16v N/A

Posted: May 22nd, 2017, 11:02 am
by NickRP
After about 5000 (road) kms, my spark plug tips look like this (please excuse borderline image quality):

Cyl #1:
Cyl #1
cyl1_crop_mini.jpg (55.29 KiB) Viewed 3824 times
Cyl #2:
Cyl #2
cyl2_crop_mini.jpg (54.7 KiB) Viewed 3824 times
Cyl #3:
Cyl #3
cyl3_crop_mini.jpg (63.16 KiB) Viewed 3824 times
Cyl #4:
Cyl #4
cyl4_crop_mini.jpg (54.96 KiB) Viewed 3824 times
The engine is a plain stock Fiat Tipo 2.0 16v. The fueling is programmed somewhat on the lean side under low load conditions, where the car spends 95% of the time.

Fuel: E10 (10% blend of ethanol in gasoline)
Oil consumption: approx 300-400 ml / 1000 km
Compression pressures: 14±1 bar

Now, I am wondering whether the white-gray ash is coming from oil (detergents), some kind of fuel additive present in E10, or something else. Another engine for the car is being slowly built, so oil consumption will be solved in the future, however, I should there be any other causes, I would like to be aware of them early enough.


Re: White-ish scaling deposits on spark plugs, 2.0 16v N/A

Posted: May 23rd, 2017, 3:21 pm
by Sandro
Hi Nik,

I only just saw your post apologies.

So in my experience this is usually oil ash deposits I have seen this many times on EU engines, and as yours does have some oil consumption this makes sense. Its not that severe to be honest.

Sometimes fuel additives can do this but I don't believe this is the case this time based on what I have seen.

To be 100% sure I would need to analyse the deposits, but I can show you photos of spark plugs tested on engines with high oil consumption that are the same.

Spark plugs will be ok, I can see some of the deposits have broken off on the ground electrodes, this is usually due to electrode movement, maybe re-gapping. Be very careful to re-gap these plugs, you need a special tool, if you lean on the insulator nose it may crack. These plugs generally do not need re-gapping once worn you replace.

I hope that helps


Re: White-ish scaling deposits on spark plugs, 2.0 16v N/A

Posted: May 23rd, 2017, 5:09 pm
by Guy Croft
Hi SP,

many thanks for answering Nikola's post, since you head-up spark-plug mfr for Federal Mogul and Champion Race Div (incl F1...) too I have no doubt you're right....

Not sure I like those plugs Nikola, why not use what I'd use - drop me an email...

or give me a call on 0044 1522 705222 one afternoon..


Re: White-ish scaling deposits on spark plugs, 2.0 16v N/A

Posted: May 26th, 2017, 12:47 pm
by NickRP
Thank you very much, that was the kind of reply I was hoping to get on the subject. I definitely did not regap the plugs.
Would it be possible the cracks / peeling are the result of a few cycles long low-load, low RPM detonation, (I) programmed into the engine management, to aid cleaning of the combustion chamber etc? Many modern cars also have this "feature".

Thank you for your remark. Actually, put those in, to test how they would behave with lean mixtures. They performed somewhat better under low load in comparison to the standard (OE) type plugs (misfire counters reduced by about 30%, throughout the cylinders), so I left them in. I have a new set of iridium tip plugs with 1.1 mm gap waiting to be installed (reference to the manufacturer deliberately omitted). 1.1 mm as I upgraded to high energy distributorless ignition system (EDIS). But given the condition of the current engine, it would almost be a shame to have them in, and covered with deposits in a few thousands. I would, of course, be grateful to hear your suggestion. As said, the car is a daily driver, driven under low load most of the time (2-3000 RPM, 300-500 mbar manifold pressure, for 95% of the time).

Re: White-ish scaling deposits on spark plugs, 2.0 16v N/A

Posted: July 7th, 2017, 2:41 pm
by Sandro
The cracking I was referring to is only the deposits lifting off. Sometime when the ground electrodes are moved the deposits will lift. No issues there. What are you doing exactly in the programming to clean the chamber?

The spark plugs you have are 3 ground electrode types done in OE for achieving a specified lifetime at a reasonable cost, but these are not particularly good from an ignition point of view. The more material you have at the end of the spark plug ie ground electrodes will absorb energy from start of ignition and slow it down. I have videos that show this not sure how I can upload its 750Mb. So you using the Iridium spark plugs with a fine centre electrode tip will definitely be better and your measurements confirm this, also you have a nice big gap 1.1mm helps a lot too. Let me guess these are from a Japanese manufacturer :) .....Personally I would change Multi ground electrode spark plugs for single ground electrode ones, you don't have to go for the most expensive Iridium ones, platinum ones are fine too (Iridium generally lasts longer but I had Platinum ones in my old Bravo 2.0 20V that went 70k miles without any issues, I did notice the engine ran smoother with these compared to the 2 ground electrode designs from OE fitted) the important point is the centre electrode has a fine tip, (going back to the less material point above.) I know some spark plug manufacturers are offering cheaper fine tip designs in a reduced range, these are not too expensive and should work well in your car. The question is what do you want to achieve with this car? Are you going to rebuild the engine? if so wait then put in the Iridium ones.

In general for road cars you want:
1) big electrode gap ( the bigger the gap the higher the voltage so you have to be careful that your ignition system can provide this voltage to fire the plug) the reason gaps are set small to start is to achieve a certain life. You could always buy plugs with bigger gaps and check them for gap growth every 10-15k km, but normally 1.0mm is good enough for naturally aspirated engines as a starting gap. Turbo engines need smaller gaps due to higher pressure in the chamber that drive higher voltages. Most modern turbo engines 1.00mm gap is end of life for spark plugs due to voltages and also abnormal combustion issues so be careful.
2) fine centre electrode tips, this helps what we call the ignitability of the fuel, and is the best type, material is not important, it only affects life.
3) projection of the spark position into the combustion chamber. This helps reduce losses to the ignition system and it depends on the type of fuel system you have, but this is done at the development and I wold not recommend you play with this unless you know your engine well, some pistons get very close to the spark plugs and you may have contact.

Race cars have a different requirement and it is on a case by case, its not easy to give a hard an fast rule.. the ones Guy has are proven on the TCs and without doing a proper evaluation I would not go against these recommendations.

I hope this has helped...but I am available for any discussion on this topic....


Re: White-ish scaling deposits on spark plugs, 2.0 16v N/A

Posted: July 8th, 2017, 9:23 am
by Guy Croft

From an industry expert....

thanks very much indeed Sandro


Re: White-ish scaling deposits on spark plugs, 2.0 16v N/A

Posted: September 21st, 2017, 8:26 pm
by NickRP

Thanks for your feedback and please accept my apologies for the delay in replying.

As per your suggestion, I installed spark plugs with fine center electrode tip. Knowing my engine quite well, clearances included, projected version was chosen.
I have slightly redesigned crankcase ventilation (in an attempt to reduce blow-by carried oil being drawn into the inlet).

Below some observations:
  1. Ignition advance between 1,500 and 2,000 RPM had to be significantly reduced - depending on load I had to take away some 5-10 degrees to fight detonation (likely much faster flame propagation from more advantageous spark plug tip design)
  2. Oil consumption has dropped to 200 - 300 ml / 1000 km, a reduction of about 100 ml
  3. Currently, after about 2000 kms of mixed use, minimal deposits on the spark plugs are present
20170806_01_web_small.jpg (154.74 KiB) Viewed 3274 times
Controlled detonation is created in low RPM range (<2,500 RPM) under positive load transients, by limiting ignition change gradient for a couple of cycles. It has been observed not to cause detrimental effects on engine longevity, while it is efficient at shearing off deposits from combustion chamber.


Re: White-ish scaling deposits on spark plugs, 2.0 16v N/A

Posted: October 19th, 2017, 5:07 pm
by Sandro
Hi Nikola

sorry for late reply...
these plugs for me look ideal for this engine, they have fine tips, and I even know the manufacturer from the pics :D
Projection or spark position looks to be in the 3mm region so good for this engine. The further you project the plugs the better the performance as you reduce losses as the flame front starts further away from the cylinder head. With race engines you cannot do this as the ground electrodes being too long will fatigue and can break off. For std road engines this is the trend today we see.

The reduced advance makes sense based on what I know, 10 degrees does sound like a lot but that does improve efficiency as you are lighting the fuel closer to top dead centre.

The deposits look a lot lower but it is difficult after only 1500 km to have significant deposits unless you are burning a lot of oil.

One thing unless its the pictures....plugs 1 and 3 look like they are running richer than 2 and 4.


Re: White-ish scaling deposits on spark plugs, 2.0 16v N/A

Posted: April 5th, 2018, 11:21 am
by Will01
Wow, i found this very interesting for sure.
Nice thread