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

Road-race engines and ancillaries - general discussion
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NickRP
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White-ish scaling deposits on spark plugs, 2.0 16v N/A

Post by NickRP » Mon May 22, 2017 11:02 am

After about 5000 (road) kms, my spark plug tips look like this (please excuse borderline image quality):

Cyl #1:
cyl1_crop_mini.jpg
Cyl #1
cyl1_crop_mini.jpg (55.29 KiB) Viewed 548 times
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Cyl #2:
cyl2_crop_mini.jpg
Cyl #2
cyl2_crop_mini.jpg (54.7 KiB) Viewed 548 times
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Cyl #3:
cyl3_crop_mini.jpg
Cyl #3
cyl3_crop_mini.jpg (63.16 KiB) Viewed 548 times
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Cyl #4:
cyl4_crop_mini.jpg
Cyl #4
cyl4_crop_mini.jpg (54.96 KiB) Viewed 548 times
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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.

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

Post by Sandro » Tue May 23, 2017 3:21 pm

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

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

Post by Guy Croft » Tue May 23, 2017 5:09 pm

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..

G
Guy Croft, owner

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

Post by NickRP » Fri May 26, 2017 12:47 pm

@Sandro:
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".

@GC:
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).
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Sandro
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Re: White-ish scaling deposits on spark plugs, 2.0 16v N/A

Post by Sandro » Fri Jul 07, 2017 2:41 pm

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....

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

Post by Guy Croft » Sat Jul 08, 2017 9:23 am

MODEL POST!

From an industry expert....

thanks very much indeed Sandro

GC
Guy Croft, owner

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