Lead substitute additives and O2 sensors 5

[NickJ67]

Hi,

Slightly unusual situation here in that we have a couple of 60s Triumph car engines running aftermarket fuel injection, with wideband O2 sensors for tuning and trim, but no catalytic converters.

One of these does not (yet) have hardened exhaust valve seats fitted and has started to experience valve seat recession. I know the correct solution is to have hardened seats fitted. However, for various reasons relating to cost and only needing to get another 9 months / 6k miles from this engine before its complete replacement, we are debating whether we can get away with running an additive to halt (or at least slow) the recession process long enough to get us there.

Up to now we have avoided additives due to worries about killing the O2 sensor. (Bosch LSU 4.2). I've now had a bit of a trawl of the web looking to see whether this is a valid worry and struggling to find anything definitive.

Seems lead does definitely cause premature failure though not instant death. Zinc also gets a mention as being a problem, though I've been running high zinc oils with the same O2 sensor 12 years in the other car without trouble.

The common lead substitutes seem to be using potassium or manganese salts and I can't find much about those. Most, but not all, manufacturers say unsuitable for use with catalytic converters (logically enough!) but nothing about O2 sensors specifically.

Not a mainstream situation I know. Anyone have any specific knowledge or experience?

Thanks & Regards

Nick

 

[enginesrus]

["It would also be worthwhile to research the reasons that US auto manufacturers started manufacturing cylinder heads with induction hardened exhaust valve seats in the early 1970s, and why automotive engine repairs and overhauls in the past several decades frequently include installation of stellite exhaust valve seats. Let me know if you think the money spent on these upgrades was wasted, and why."]

Not wasted at all. The higher temperature of unleaded back then can cause the recession problems. And in the day TEL would also cause the same due to corrosive chemical attack. Newer unleaded fuel now may have been improved since back in the day when we did the testing.

["I think you need to look at the fields the experts are working in. The aircraft experts talk about valve recession caused by lead while the automotive experts talk about valve recession due to no lead. These are two very different applications. "]

Yeah one bunch then actually knows something. The other bunch is years behind and always has the attitude they invented something new. Like the use of turbo chargers and N2o, all from WW2 aircraft engine days.
The application has little to do with the chemical action on the parts. The big difference now is the fuels used and power demand, and of course most aircraft engines are air cooled.

 

[TugboatEng]

You have much to learn. The aviation industry has the advantage of taking one engine design and refining it to perfection/death. The automotive guys have to come up with new ideas anually to keep up with customer demands and emissions rules.

You have a lot of work to do on perspective. Yes, the wingnuts figured out they could use turbochargers to make their engines perform similarly at high altitude to their ground performance. It was those dummy stationary and marine guys that figured out the Miller Cycle that boosted power to astronomical levels while lowering emissions and it was adopted by automotive before the wingnuts figured out fuel injection.

 

[gruntguru]

The state-of-the-art in automotive reciprocating engines has moved way beyond engines in aero applications. The frenetic pace of aero piston engine development died at the end of WW2 in favour of jets and turbo-props (and next will be battery-electric and hydrogen alternatives).

You suggest the role of TEL in reducing valve seat recession is a myth but offer no evidence and no inclination to follow the links and evidence presented here. Extracts from scientific publication such as

lead acts as a lubricant between the mating surfaces of exhaust valves and their seats in the cylinder head. Many older engines took advantage of this fact and employed “soft” valve seat metallurgy, which relied on some form of protection to prevent excessive wear, commonly referred to as valve seat recession.

An easy read. Link
Scroll to page 4 and read the paragraphs titled Mechanism of Wear which describes the wear process and concludes in paragraph 4

https://www.jstor.org/stable/44718153?seq=4#metadata_info_tab_contents[/URL]]The presence of lead in the combusted fuel has been proven to drastically reduce or totally eliminate the wear process described above.

je suis charlie

 

[enginesrus]

gruntguru,
All that is still just basically hearsay, again where is the proof it acts as a lubricant? It sure didn't help lubricate valves and seats in the old days.
I can offer evidence that TEL did the opposite of what you say. I will post it once someone posts the metallurgical evidence that TEL or what ever from it, attaches to the valve face seat interface and acts as a lubricant, not just repeating some story's started by some TEL manufacture back when it was mandated away from automobile use.

 

[TugboatEng]

You are supposed to present information to stimulate discussion, not walk in the room and yell, tell me something so I can prove it wrong!

 

[gruntguru]

More heresay and anecdotes.

Abstract
Valve seat wear or “sinkage” or “recession” was observed in eight engines run on unleaded fuel. Detailed studies of valve seat wear were undertaken in a 302 cu in. V-8 engine run for 10-1/4 hr at WOT on a dynamometer stand. The seat was oxidized and flaky, and the valve face was spotted with hard (45-55 Rc) oxide nodules. It was concluded that during operation the oxide flakes adhere to the valve face to form nodules which become embedded in the metal (43 Rc). With the embedded nodules, the valve wears the cast iron seat (40 Rc) by abrasion. Loads, rotation, and temperatures are often influencing factors.
The use of leaded fuel in another engine was found to form PbO · PbSO4 on the hot valve face and Pb (Cl0.75 Br0.25)2 on the cooler seat. These compounds are high-temperature solid film lubricants which, by coating the surface, inhibit cast iron oxidation and also prevent material transfer.

je suis charlie

 

[TugboatEng]

In the engrus' favor, seat recession on diesel engines habe been all over the board over the years and the fuel hasn't changed much other than sulfur content. There has never been TEL in diesel. Please exclude heavy fuel diesel engines as vanadium salts cause their own problems.

 

[enginesrus]

Funny how those high temp solid film lubricants cause corrosion.
One of many.

https://apps.dtic.mil/dtic/tr/fulltext/u2/a801137.pdf

 

[TugboatEng]

So your gotcha article is about ethylene dibromide and not TEL. Can you explain your conclusions? Also, your article is dated before any modern fuel formulation.

An interesting example, I interned on a steam ship built in 1975 to run on Bunker-C. By the time I set foot on the ship in 2005, bunker-C was obsolete. We had to run a similar fuel called IFO-380 but the ash content wasn't controlled and the fuel bought in Hawaii caused fouling of the fuel heaters and coking of the boiler tubes relative to the fuel bought in SF.

Fuels and lube oils change regularly, almost anually right now so past experiences are weak correlations. I'm talking about you Shell Rotella lovers.

 

[3DDave]

Great report, but no fuel maker would add TEL without a scavanger such as ethylene dibromide. The report also fails to mention any failure of the valve seat, the core of the disagreement. What is also true is no baseline for valve weight loss absent the use of TEL was given so it is not much proof of anything but the effectiveness of ethylene dibromide, which is the subject of the report.

Also, the lead was removed by electrolytic process; there was no proof that a valve with no lead deposits would not lose weight or that merely holding lead in contact with the valve during the electrolytic process would not do the same, just that apparently heavier deposits are likely to require a lengthier time and would remove more metal overall; possibly the valve weight loss is due to dissimilar metal corrosion from the electrolytic bath, a loss that would not occur in a running engine. I understand they did not use a non-TEL fuel as a corrosion control as they were only interested in increasing TEL with ethylene dibromide additive.

Perhaps the other reports are more focused on how the TEL valve seat corrosion occurs. It doesn't explain why the engine makers put the extra expense into harder seats if it was not required.

 

[TugboatEng]

I must disagree on one detail. Valve recession must always be considered as the sum of both valve and seat wear. I don't how different us diesel dudes experience is bit recession is usually concentrated in the valves for us.

 

[enginesrus]

At the very top summary "Corrosion of Exhaust Valves". You need to remember those valves and seats where corrosion resistant materials, high nickel, chromium, cobalt etc.
Like I said TEL is not protecting valves and seats.
This fellow was refreshing

https://www.avweb.com/features/pelicans-perch-55lead-in-the-hogwash/

it is amazing all the things learned in the old days are either ignored or forgotten.
The many cases in the 50's of valves and seats being eaten by recession and wear are thrown out in the modern day TEL topic.

 

[TugboatEng]

It seems the concensus should be that TEL prevented recession in automotive engines without hardened seats. TEL prevents low speed detonation in aircraft engines. As soft seats are a thing of the past TEL is no longer required for automotive engines but aircraft engines still have issues with low speed detonation hence why lead is no longer used for automotive but still in use for aircraft.

 

[gruntguru]

The first link (Link) has zero relevance to the topic.
1. It is entirely concerned with chamber deposits and resulting corrosion - nothing to do with valve recession.
2. Valve recession is not a corrosion phenomenon. Did you read "Mechanism of Wear" in the above linked paper? (Link)
3. Valve seat recession due to lack of lead lubrication occurs at higher engine speeds. Car engines operated at low speeds and aircraft typically do not suffer.
4. The test engine was an aircraft engine with hard valve inserts.

The second link (Link) is a fine example of something you are not interested in:

I'm not anti TEL. I'm just interested in real information and not the internet story's passed on about the subject.

He may even be right, but again he is referring exclusively to aircraft engines - all of which operate at relatively low speeds and have hard valve seat inserts.

je suis charlie

 

[enginesrus]

grunt, corrosion is the topic of recession. There were all kinds of automotive valve problems in the old lead days. No valve job made it 100,000 miles in the 50's. Lead lubrication of valve seating is a fallacy a wives tail just like many other such goofiness on the internet, similar to another unrelated fallacy that is taught in many university's and of course the internet, that has been noticed by experts in that area of study as being wrong. Just because everyone preaches something, that does not make it true. Corrosion, heat as well as rotation/ movement and pressure is the mechanism of wear at the valve seat interface, and with rotation/ movement and tons of lead in the fuel, recession happens, how can that be with all that TEL lubrication? Lead oxide is corrosive.

Like so called experts are never wrong.
2. Valve recession is not a corrosion phenomenon. Did you read "Mechanism of Wear" in the above linked paper? (Link)

 

[TugboatEng]

Ugh, the discontinuation of TEL for road gas was coordinated with and by the USA auto manufacturers so they could make the necessary changes to their engines in order to run on unleaded gas. Thankfully, the change forced the engine manufactures to make more durable engines.

 

[gruntguru]

grunt, corrosion is the topic of recession

No it is not.
You obviously have still not bothered to read "Mechanism of Wear" in the above linked paper! Link

je suis charlie

 

[enginesrus]

The link the date, and Phillips Petroleum company, explains it all. I saw no "Mechanism of wear" in that link, it is just a preview of the paper. Does it mention heat, movement- rotation and impact loading when closing as well as corrosive attack? And of course they want to sell leaded fuel as well.
There are plenty of stories about how unmodified auto engines survived just fine as far as valves go after the introduction of unleaded. Like mentioned during the leaded gasoline period valve regrinds were needed about every 30,000 to 50,000 miles or so. TEL has never been friendly to valves, and has caused more burned valves from buildup of deposit's and pitting, than unleaded has in recessed valves.

Go to page 180 conclusion to see cause of valve recession, is there a lube mentioned that will prevent that? I suppose lead bearings act as a lube for a few minutes after the oil film is gone, just before the journal seizes in it.

http://www.ijirset.com/upload/december/7-Failure Analysis of Internal.pdf

 

[gruntguru]

Apologies for problems with that link - no wonder you hadn't read it! I will try to post the relevant section from my work computer next week (I have better access to research publications at work).

The solid lubricant deposits on exhaust valves arising from TEL are not "Lead", they are compounds of lead (see below). The wear mechanism is much more complex than sliding of a plain bearing (see below).

"The seat was oxidized and flaky, and the valve face was spotted with hard (45-55 Rc) oxide nodules. It was concluded that during operation the oxide flakes adhere to the valve face to form nodules which become embedded in the metal (43 Rc). With the embedded nodules, the valve wears the cast iron seat (40 Rc) by abrasion. Loads, rotation, and temperatures are often influencing factors.
The use of leaded fuel in another engine was found to form PbO · PbSO4 on the hot valve face and Pb (Cl0.75 Br0.25)2 on the cooler seat. These compounds are high-temperature solid film lubricants which, by coating the surface, inhibit cast iron oxidation and also prevent material transfer."

je suis charlie

 

[enginesrus]

TEL was banned for automotive use in 1996. The paper date was 1985 so of course the oil company's were going to try to prove that it was good for something. The facts are there are no benefits to valves using TEL.
Look for the pre 60's study's of valve burning caused by it. Looks to me the oil company's are the ones that started the valve recession story.