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

 

[TugboatEng]

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

 

[3DDave]

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.

 

[enginesrus]

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.

 

[gruntguru]

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

References.

je suis charlie

 

[enginesrus]

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.

 

[gruntguru]

I'm not saying the presence of TEL does not help the problem.

Great. We are in agreement.

je suis charlie