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Lead substitute additives and O2 sensors
5

Lead substitute additives and O2 sensors

Lead substitute additives and O2 sensors

(OP)
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

RE: Lead substitute additives and O2 sensors

If your software has the ability to do so, lock in your current trim settings, disable the self-tune/auto-tune/closed-loop operating mode, and remove the O2 sensors.

This is what is done in the motorcycle world when using aftermarket EFI and the engine is to be operated on race fuel.

RE: Lead substitute additives and O2 sensors

It seems some of the outboard boat motors with 2-stroke engines had oxygen sensors. I don't see lead substitute being much different from 2-stroke oil.

RE: Lead substitute additives and O2 sensors

There are plenty of products like this around. Link "Safe for oxygen sensors and catalytic converters."

Or you could run a low percentage of leaded fuel. If you visit one of the EFI tuning websites, there are lots of tuners using WBO2 sensors to tune race engines on leaded fuel. They will know how long they last on leaded fuel eg. Link A contaminated sensor will recover significantly by running it for a period in another (unleaded) engine.

je suis charlie

RE: Lead substitute additives and O2 sensors

So where is the data that shows lead oxide deposits on valve contact surfaces and adds protection? Has there been chemical analysis to prove such? Or is it just the ante-detonate doing its normal job and lowering the combustion chamber temperature and thus the valve contact surface temperature causing less supposed micro welding and attack? There is data showing how the leaded gas would chemically attack and shorten valve life.

RE: Lead substitute additives and O2 sensors

The data goes back 100 years. Try Google.

je suis charlie

RE: Lead substitute additives and O2 sensors

For example:

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: Lead substitute additives and O2 sensors

All anecdotal information. Tests with no data. "How ever tests at lower speeds valve seat recession was greatly reduced"
So does that mean less load and less heat? The real data shows lead caused the problems, not helping it.

RE: Lead substitute additives and O2 sensors

Low speeds tend to produce more load and more heat. Reciprocating aircraft engines operate at very low speeds compared to their automotive counterparts which is why they still get to burn leaded gas.

How about this?

"Initial results have indicated that unleaded fuel is more severe than leaded fuel with respect to varnish deposits, full throttle octane requirement increase, exhaust valve seat wear, and wear of certain other engine components."

https://www.sae.org/publications/technical-papers/...

Then again 2 years later:

" The unleaded gasoline performed as well as or better than a leaded gasoline in this test when both gasolines contained the DC additive. Engine deposits were comparable, and wear and corrosion were reduced when unleaded gasoline was used."

https://www.sae.org/publications/technical-papers/...

You'll have to fork over some money to get the definition of "wear".

RE: Lead substitute additives and O2 sensors

TugboatEng
That is the problem, we don't know the most important variables. The load and the combustion temperature. Lead had a corrosive effect on valves and seats, the one thing it did good was inhibit combustion or cool it, similar to H2o injection. Hardened seats and valves were desired in the days of TEL through WW2, corrosive resistant materials.
I desire to see the proof of lead deposition onto the valve - seat interface. Who has done the chemical analysis of the lead attachment, and how something corrosive to the valve - seat material is protecting it?

In automobile terms less speed means lower load and temps, throttle is closed some.

[quote the above]
Low speeds tend to produce more load and more heat. Reciprocating aircraft engines operate at very low speeds compared to their automotive counterparts which is why they still get to burn leaded gas.

How about this?

"Initial results have indicated that unleaded fuel is more severe than leaded fuel with respect to varnish deposits, full throttle octane requirement increase, exhaust valve seat wear, and wear of certain other engine components."

https://www.sae.org/publications/technical-papers/...

Then again 2 years later:

" The unleaded gasoline performed as well as or better than a leaded gasoline in this test when both gasolines contained the DC additive. Engine deposits were comparable, and wear and corrosion were reduced when unleaded gasoline was used." [end of quote]

What is the DC additive? Of course the hotter burning unleaded is worse.

RE: Lead substitute additives and O2 sensors

Corrosion from lead certainly seems to be a problem for aircraft engines that operate at high EGT's for extended periods of time.

The principal corrodants in internal combustion engines operated on leaded gasoline are lead oxide, a mixture of sulfates, bromine, and chlorine. The presence of these corrodants have been determined by diffraction, and EDAX deposit analysis. Bench test data has been run to rate various valve materials in these corrosion environments. When the standard line of carbon and nitrogen strengthened stainless steels (such as 21-4N developed specifically for exhaust valve applications) are employed and operating temperatures exceed the capability of these steels, failure results in lead oxide enhanced corrosion fatigue. Nickel-base superalloys, such as Inco-751, possessing excellent lead oxide corrosion resistance are relied upon to extend valve life. Based on lead oxide corrosion bench test data of these alloys, a 115 C increase in operating capability would be expected. However, the life improvement in these alloys is now limited due to sulfidation and bromine/chlorine enhanced corrosion. Consequently, the increase in operating temperature capacity is limited to approximately 60 C.

https://www.osti.gov/biblio/5452230-high-temperatu...

However, corrosion takes time to occur and may not be the leading contributor to recession, especially for automotive engines that rarely operate at high enough temperatures to cause this corrosion.

Take the lead away and live with detonation at low speeds and see what causes shorter overall engine life.

RE: Lead substitute additives and O2 sensors

Aircraft valves and seats have been made from non corrosive materials for many many years. So then lead not needed for that.
Right on TEL is for anti detonation. It does not coat the valves and seats. Unless there is someone that can show the metallurgical tests to prove it does.

RE: Lead substitute additives and O2 sensors

Ok, this one shows recession in automotive engines caused by the removal of lead and suggests replacement additives.

"In using unleaded gasoline for cars with soft exhaust valve seats, their recession was found to be excessive after only 3000 - 12 000 km of usage on the highway at 120 km/h "

https://www.sae.org/publications/technical-papers/...

Aircraft have almost always always had aluminum heads so they've required inserts always. I guess your dilemma comes from two very different uses of lead in two very different applications.

RE: Lead substitute additives and O2 sensors

It looks like TEL increases combustion temps or at least interferes with adverse cooler combustion knocking:

Quote (https://en.wikipedia.org/wiki/Tetraethyllead)

A noteworthy feature of TEL is the weakness of its four C–Pb bonds. At the temperatures found in internal combustion engines, (CH3CH2)4Pb decomposes completely into lead and lead oxides as well as combustible, short-lived ethyl radicals. Lead and lead oxide scavenge radical intermediates in combustion reactions. Engine knock is caused by a cool flame, an oscillating low-temperature combustion reaction that occurs before the proper, hot ignition. Lead quenches the pyrolysed radicals and thus kills the radical chain reaction that would sustain a cool flame, preventing it from disturbing the smooth ignition of the hot flame front.

RE: Lead substitute additives and O2 sensors

Quote (Valve Seat Recession – An Independent Review of Existing Data. R. C. Hutcheson. Cameron Associates)

ABSTRACT
The mechanism of valve seat recession is well
understood and a review of the existing literature shows
that it consists of two processes – the generation of hard
particles that then grind or abrade the valve seats.
Metallic fuel additives can prevent recession by stopping
the generation of these hard particles. Both new and
previously published data are presented to demonstrate
that low concentrations of all the commonly available
additives provide adequate protection for most service
applications. However, the data also show that severe
testing with low treat rates will produce valve seat
recession. The author argues that, if sufficient
concentration of additive is used, the initiation of
recession is stopped under extremely severe conditions
and alternatives to lead can offer complete protection.
The paper concludes that the use of lead replacement
additives should be at the maximum possible level
commensurate with all aspects of engine performance.
There are no standard tests for valve seat recession and,
as a consequence, the additive supplier must be
responsible for recommending dose rates that do not
lead to potentially harmful side effects.

INTRODUCTION
Since their discovery in the late 1920’s, lead alkyls have
been used in gasoline to improve octane quality.
However, environmental pressures have resulted in a
progressive reduction in lead content since the early
seventies, culminating in a complete ban in much of the
European Community from 1 January 2000. As well as
boosting octane, 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.
. . .

je suis charlie

RE: Lead substitute additives and O2 sensors

Again all anecdotal information. Now show the information of how TEL ruined valves and seats, of aircraft engines, especially German engines in WW2!
Wikipedia quotes mean nothing, all that is there is constant repeats of the various wives tails.
Any valve - seat recession is caused by corrosive action and heat. TEL is a known corrosive.
Any tests run on engines that I know of have not identified the important parameters that can cause recession.
Most have just been run for a time on this fuel, then that fuel. Absolutely no information on combustion temperature.
I would like to see the information that shows real data, not a bunch of internet experts.
Data like metallurgical testing etc.
3Ddave if so then it would assist detonation.

RE: Lead substitute additives and O2 sensors

2
SAE has that information in the studies I linked. You're going to have to pay to see them. SAE is one of the most authoritative bodies when it comes to engine development. However, you clearly know the answers to your questions so your time is wasted here.

RE: Lead substitute additives and O2 sensors

TugboatEng
Have you looked at that SAE info? I have some old SAE papers I will review. I don't remember ever seeing any sort of report from any organization that mentions metallurgical study's of lead deposition on
Valve seating faces and valve seats. How come all the data about ruined valves and seats caused by TEL is almost completely ignored by all the supposed experts in the engine field? I'm not anti TEL. I'm just interested in real information and not the internet story's passed on about the subject.

RE: Lead substitute additives and O2 sensors

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.

RE: Lead substitute additives and O2 sensors

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.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: Lead substitute additives and O2 sensors

["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.

RE: Lead substitute additives and O2 sensors

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.

RE: Lead substitute additives and O2 sensors

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

Quote (Valve Seat Recession – An Independent Review of Existing Data. R. C. Hutcheson. Cameron Associates)

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

Quote (from https://www.jstor.org/stable/44718153?seq=4#metada...)

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

RE: Lead substitute additives and O2 sensors

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.

RE: Lead substitute additives and O2 sensors

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!

RE: Lead substitute additives and O2 sensors

More heresay and anecdotes.

Quote (Published February 01, 1971 by SAE International in United States)

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

RE: Lead substitute additives and O2 sensors

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.

RE: Lead substitute additives and O2 sensors

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.

RE: Lead substitute additives and O2 sensors

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.

RE: Lead substitute additives and O2 sensors

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.

RE: Lead substitute additives and O2 sensors

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-55le... 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.

RE: Lead substitute additives and O2 sensors

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.

RE: Lead substitute additives and O2 sensors

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:

Quote (enginesrus)

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

RE: Lead substitute additives and O2 sensors

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)

RE: Lead substitute additives and O2 sensors

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.

RE: Lead substitute additives and O2 sensors

Quote (enginesrus)

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

RE: Lead substitute additives and O2 sensors

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%2...

RE: Lead substitute additives and O2 sensors

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

RE: Lead substitute additives and O2 sensors

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.

RE: Lead substitute additives and O2 sensors

Are you even reading our links?

Valve seat recession was a problem in AUTOMOTIVE engines. The TEL had to be replaced by other chemicals to prevent recession so CLEARLY it has an effect.

From my SAE link ALREADY posted:

Valve Seat Recession and Protection Due to Lead Phase Out in Thailand 962029
As the consequence of air quality detenoration and the car overpopulation in Bangkok Metropolitan Area, unleaded gasoline was introduced in 1991 In using unleaded gasoline for cars with soft exhaust valve seats, their recession was found to be excessive after only 3000 - 12 000 km of usage on the highway at 120 km/h Such cars represented about 15 percent of the national car population in 1993
Using an anti-valve seat recession additive is one solution used to prevent valve seat recession An engine test simulating field conditions to evaluate additive effectiveness was implemented Potassium-based and sodium-based additives were tested and the test results led to the conclusion that the effective anti-valve seat recession additive treat rate suitable for car population and driving condition in Thailand was 10 mg of potassium or sodium per kg of fuel Unleaded gasoline with anti-valve seat recession additive has replaced leaded gasoline in Thai market as of 1995 Finally, leaded gasoline was completely phased out as of January 1, 1996 by Government regulation

RE: Lead substitute additives and O2 sensors

I think the point must be that it was such a vast conspiracy, secretly funded by the TEL makers that had a financial interest, that every study showing the benefits must be a lie and that only those with their own research can know the truth.

Even if true, especially if true, it broadly makes zero difference anymore. In this case, it's one motor for the original poster, and I literally would like to see an end to hobby manned aviation if it depends on the use of TEL.

The crime the TEL makers commit is lying about the lead poisoning of millions of people; who cares about valve seat damage in comparison to that? I sometimes wonder if the "lead paint" campaigns were funded as a cover for far more toxic lead vapors.

RE: Lead substitute additives and O2 sensors

I had mentioned the test done that shows why the valves did better with TEL than unleaded gas and it has zero to do with with a corrosive skin of TEL deposites on the valve faces and seats.

RE: Lead substitute additives and O2 sensors

From "Exhaist Valve Recession with Low-Lead Gasolines." Schoonveld et al



References.

je suis charlie

RE: Lead substitute additives and O2 sensors

All those same things that happened in the leaded fuel days as well, so what they say is untrue. More so with hotter cylinder head temperatures with the new unleaded gasoline's, that maybe different now don't know.
Again for all the SAE papers listed above, what organization's did the investigations? They are looking at the wrong cause of the problem. I'm not saying the presence of TEL does not help the problem.
In the 50's-60's build up of lead deposit's caused burned valve-seat faces. I remember horrible looking valves and seats in those older engines back in the 60's, lots of guttering and pitting, there are SAE tests of the valve recession in the mid 50's one is measuring dynamic valve recession from TEL components. In the hay day of 3 to 4 cc's per gallon of TEL in the 50's, there was one engine manufacture that was having huge problems with valve seats and valve faces wearing out prematurely, TEL was not lubricating them very well. The article above sort of hits on the main cause, with the mention of load.

RE: Lead substitute additives and O2 sensors

Quote (enginesrus)

I'm not saying the presence of TEL does not help the problem.
Great. We are in agreement.

je suis charlie

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