Why I run LOP and add TCP to fuel

[mcpilot]

Here are some before and after photos.  The before photos were taken of #2 and #4 exhaust valve faces (rear cylinders left and right which are the hottest CHTs) on my 1995 M20J MSE.  After the initial photos were taken, I began to add TCP to the fuel and installed a JPI EDM830 and ran the mixture LOP according to the recommendations of Mike Bush on Savvy Aviator.

 

As you can see the valves look much cleaner...  The IO360 A3B6D seems to have issues with stuck and sticking valves and running according to the operators manual (50 degrees and > ROP may lead to these problems...  

 

[ncdmtb]

Do you have any mods installed? GAMI?

[mcpilot]

Yes. GAMIjectors. The fuel flow spread between peak EGTs is 0.2gph

[aviatoreb]

What is TCP?

[mcpilot]

TCP is tricresyl phosphate.  IT's a lead scavenger that is added to fuel.  ITs FAA approved as a fuel additive.

[aviatoreb]

Huh - never heard of it.

 

But as a scientific experiment, doing two things and reporting the change does not tell us that both were important.  Maybe running ROP and using TCP would have shown the same result as the TCP is a super product for lead scavenging.

 

Or maybe TCP is not worth anything but LOP ops keeps it clean and even scavanges recently deposited lead and gives the results you see.

 

Or maybe as your experiment suggests that both are helpful and together is even better.

[mcpilot]

Haha. My post was not to be taken as a scientific experiment. Scientific research was already done on TCP during its FAA certification process. Running LOP has also already been proven to produce a more complete combustion event and as result less undesirable by-products with the added advantage of cooler CHTs....

I would guess that if you started with a clean engine and just ran LOP the ethylene dibromide in 100LL would do its job as a lead scavenger and TCP might offer only marginal improvement. The problem may be when you have an engine that has been run ROP and that has developed a lot of buildup. The ethylene dibromide in the fuel may not be enough to clean it up as well....

[N33GG]

Us old timers refer to TCP as Tom Cat Piss. I added it religously to the gas in my Swift since its engine was designed for much lower lead than 100LL which was the lowest available. Without TCP in that engine, the lead fouling on the plugs and valves was significant and immediate. Worked great. I have never added it to fuel in higher compression engines that are designed for higher lead content.

I am not an expert in this area. Before I would add TCP to an engine I would seek advice from some people that could assure me that there would be no adverse effects.

For all the experts out there, here would be my questions: Do modern engines need the additional lead for lubrication, and does the addition of TCP to modern engines present a risk in any way?

[mcpilot]

TCP is FAA PMA approved for all Continental and Lycoming non turbo supercharged reciprocating engines. It also has approval for some others as well. I'm not here you'll the product. Check out the alcorinc.com website and if you are interested you can read the FAA poor les and the MSDS.

TCP promotes the formation of lead phosphate during combustion as opposed to lead oxide. This does not effect the beneficial properties of tetra ethyl lead. Lead phosphate is more easily removed in the exhaust than lead oxide which is a harder material and more prone to cause buildup and valve seat erosion.

I'm not posting this information to try to convince anyone to use or not to use this product. I'm just sharing something I thought might be of interest to he group. Take it for what it's worth...

[DaV8or]

Kinda hard to tell from your photos what exactly is going on. Is the lead going away, or increasing? It could be argued that the lead is actually covering over, rather than receding.

[kmyfm20s]

What ever happening, it's even now.

[bnicolette]

Us old timers refer to TCP as Tom Cat Piss.

I have never added it to fuel in higher compression engines that are designed for higher lead content.

For all the experts out there, here would be my questions: Do modern engines need the additional lead for lubrication, and does the addition of TCP to modern engines present a risk in any way?

 

There are definitely some of us that have had the issue with lead build ups causing morning sickness.  I have run 50/50 ROP & LOP over the last 40 hours or so and still had this issue creep up on me.  However, I have been using TCP over the last 20 hours and will continue to do so.  So I will see how it works for me.  Certainly not a big cost and very easy to add to the fuel.

 

http://mooneyspace.com/topic/9525-sticky-valve-lycoming-io-360-a3b6d/

[mcpilot]

Actually what I was told by Mike Bush is that you want to see an even pattern on the valve face with the "circle" pattern in the center.  This would indicate even heat distribution.. He looked at the photos that I posted as well and gave them the thumbs up...  The lead combustion product is different from that without TCP.  Lead phosphate is more of a "powdery" substance that is removed in the exhaust and oil...  You can see evidence of it on the tail pipe of the muffler....

[pinerunner]

There are definitely some of us that have had the issue with lead build ups causing morning sickness.  I have run 50/50 ROP & LOP over the last 40 hours or so and still had this issue creep up on me.  However, I have been using TCP over the last 20 hours and will continue to do so.  So I will see how it works for me.  Certainly not a big cost and very easy to add to the fuel.

 

http://mooneyspace.com/topic/9525-sticky-valve-lycoming-io-360-a3b6d/

I don't believe lead serves as "lubrication" but this articles by Ben Visser, an oil industry expert sheds some light.

 

www.generalaviationnews.com/2008/02/mythbusters-does-lead-have-any-effect-on-valve-life/

 

 

"Lead byproducts of combustion coat the exhaust valve and seat interface. This prevents the valve from grinding into the valve seat and recessing into the head.

Exhaust valve recession is very real and very easily demonstrated. I observed many lab tests on automotive engines in the late 1960s. Exhaust valve recession would occur any time an engine designed to run on leaded fuels was run at high RPM and high load with unleaded fuel. The automotive industry has eliminated this problem in today’s engines by installing hardened valve seats. In addition, auto engines are liquid cooled.

About 15 years ago, an aviation fuel supplier started selling 80/87 avgas with no lead. This is perfectly legal because the spec for 80/87 only calls for a maximum of 0.5 grams of lead per gallon and no minimum.

The fuel worked well for awhile. Then people started to overhaul their engines, and found that when they used unleaded fuel from the start, the exhaust valves recessed into the head. Usually the valves would recess enough to use up the clearance and then the valve would be held off the seat until valve burning occurred.

Here we have a problem that has been observed and documented by many knowledgeable people, yet there are those out there who call it a myth and a complete fabrication. I believe that this is one of the biggest problems ? if not the biggest ? in aviation."

 

In a separate article he states "It is important to understand that most exhaust valve sticking is caused by excessive amounts of lead being deposited in the exhaust valve/guide area. The above mentioned bulletins outline several steps, such as aggressive leaning and more frequent oil changes, which can reduce the amount of lead by burning it (leaning) or removing it (more frequent oil changes)."

 

So apparently some lead on the valves is good and prevents valves wearing away the seat while too much leads to sticking. This is more complicated than I thought and makes me want to go out to the airport and bay at the moon.

 

Its good to know TCP and LOP can have an effect without needing a top overhaul. I want hardened valves seats.  Do I have to get new cylinders to get them? Are we going to go through a bunch of trouble when lead-free gasoline comes online in a few years?

 

Dave 

[jetdriven]

That's an old wives tale. Aircraft engines have had hardened valve seats for decades. There are RV guys and Bonanza guys who have run unleaded fuel for 2000 hours and no valve seat erosion. Lead is there solely for octane enhancement.

[pinerunner]

That's an old wives tale. Aircraft engines have had hardened valve seats for decades. There are RV guys and Bonanza guys who have run unleaded fuel for 2000 hours and no valve seat erosion. Lead is there solely for octane enhancement.

You mean..I have hardened valve seats!   

[Shadrach]

You and everyone else...  It was not always in all engines.  Most of the British motor vehicles of the before the about mid 70s were susceptible to valve recession when run on unleaded fuel. But those motors were easily upgraded at overhaul to accommodate unleaded fuels. AFAIK it has never been an issue on aircraft engines, which may in fact be due to hardened valve seats. Given the operating range of most AC engines, one might also theorize that AC engines likely run much lower valve spring rates and lower lift than most road vehicle applications; this would also make them less susceptible to valve recession...

[pinerunner]

You and everyone else...  It was not always in all engines.  Most of the British motor vehicles of the before the about mid 70s were susceptible to valve recession when run on unleaded fuel. But those motors were easily upgraded at overhaul to accommodate unleaded fuels. AFAIK it has never been an issue on aircraft engines, which may in fact be due to hardened valve seats. Given the operating range of most AC engines, one might also theorize that AC engines likely run much lower valve spring rates and lower lift than most road vehicle applications; this would also make them less susceptible to valve recession...

Ah are you saying Visser was just making this up.

 

"

About 15 years ago, an aviation fuel supplier started selling 80/87 avgas with no lead. This is perfectly legal because the spec for 80/87 only calls for a maximum of 0.5 grams of lead per gallon and no minimum.

The fuel worked well for awhile. Then people started to overhaul their engines, and found that when they used unleaded fuel from the start, the exhaust valves recessed into the head. Usually the valves would recess enough to use up the clearance and then the valve would be held off the seat until valve burning occurred."

 

The article is at old so add a bit to his 15 years. I think he's retired now but he used to be a chemist for an old company I think and analyzed the deposits on a lot of valves etc. I believe they were getting evidence as to what made them stick (lead implicated along with something else helping it stick; ROP byproducts I bet). He was nice enough to answer one of my emails so decent guy i think. There must be something to that 80/87 unleaded avgas senario. 

 

Anyway I'm going to try TCP.

 

I have to add something to this. I just read John Deakins "Lead in the Hogwash" article and am starting to think Shadrach is spot on. It can be hard to tell who's giving you real data and who's quoting someone elses made-up data. Perhaps Visser was quoting old company propaganda that he believes. Maybe a bit of truth in there somewhere. I also found a PDF copy of a 1989 report where they ran two IO-320's side by side on a test stand, one with unleaded premium auto gas and one with 100LL for 150 hours. No significant difference in valve recession could be found. It was by Jerry R. Allsup.