6.5 connecting rods

[consaka]

So are you coating the back side of the precups or just the bowl behind it?

Any part directly exposed to fire will get coated. The idea being to keep the heat on the fire side and allow the precup to be cooler.

 

[consaka]

I have pulled many heads with 150,000 + miles that the precups never cracked. Ask yourself why they doubled the cost of making the head by using the inconel precups instead of something cheap or just cutting the port into the cast head.

If you want to insulate between the precup and the head, I am all for it. But the specific inconel that was chosen is not the cheapest one, infact it is one of the most expensive ones- why? Because they want the precups getting as hot as possible and retaining the heat as much as possible. That way it is not heat cycling up and down in temperature.

And yes, ignition in the precup is a big helper. If it didnt matter you could just open the port wide open and the bigger you make it letting fuel get through quicker, the more power you would have. But many here learned a little port goes a long way.

The only precups I have seen that were not cracked were the older smaller ported precups. The T-cups I am reusing for this build are already cracked. Not too badly. I'd prefer the newer diamond cups but no idea where to find them.

Why would you insulate the precup from the head? You need to do the opposite. It needs heat sinked to the head. I am going to respectfully disagree that the precups need to be hot. I do not believe they do need to be hot. Heat absorption is a loss of power. Heat absorbed by the precup gets sent directly to the head and carried off by the water. Sure I understand there is a delay due to heat traveling through the precup to get to the head at its contact points. Thus its temps are far higher than the head itself. But think of it this way. What the coating does is allow the precup to run cooler while the surface of the coating actually runs hotter. That is how insulators work, building a barrier between different levels of heat. I have no idea where you get the idea that insulating the precup is going to cause heat cycling. I also don't understand your comment on ignition in the precup. It is an IDI engine, the ignition is always in the precup but has nothing really to do with the precup. The precup is a way of controlling the flame and rate of cylinder fill. It is also a nice handy place for glow plugs to sit directly in the injection stream. Once the engine is running the fuel does not need to hit a hot surface to ignite. The air is always hotter than any surface in the cylinder at the time of injection. The exhaust valve might be an exception.
Ideally all the metal surfaces would be completely insulated to absorb no heat whatsoever. Such an engine would be massively more efficient. The in cylinder temps would be hotter and the heads, valves, and everything else would be cooler.

 

[consaka]

Just for giggles has anyone actually seen a broken precup? I presume those cracks could get so bad they would eventually go all the way through.

 

[Will L.]

Yes i have seen precups crack so bad the compression blows out theough it. When I was running my psycho fuels in my drag truck, I blew some heads to pieces.

I understand the thought process you are following- we are just seeing opposite sides of the same barn.

Give it a try, but at some point get it going, and change out only the precups for comparison.

 

[consaka]

Yes i have seen precups crack so bad the compression blows out theough it. When I was running my psycho fuels in my drag truck, I blew some heads to pieces.

I understand the thought process you are following- we are just seeing opposite sides of the same barn.

Give it a try, but at some point get it going, and change out only the precups for comparison.

Ahh I love a good test. Anyone care to wager what will happen? Anyone got spare precups for the experiment?
Anyone got any idea as to measurements to test the results?
I'll be building an engine stand and putting a 4L80E on behind but I will have no way to actually load it down. Be good for idling and throttle blips though.

 

[Will L.]

Dont have lots of spares anymore, that was all years ago. Been theire, got the tshirt. For diamonds, look at optimizer heads.

When you start doing things like have an engineer friend at Timet (the titanium manufacture here) make you blended titanium and inconel precups, you learn a thing or two. He even did a set of titanium pistons that lasted 5 minutes. Enough playing around has been done by me. Your turn to reinvent this wheel. There is much better insulators available to you now.

Just remember: when you get to the fork in the road go "right", not like I did many times experimenting. "Right" the first time would have saved some headaches, haha.

Good luck, and take some video if you can. You tube has lots of room to go!

 

[consaka]

Titanium pistons? why they last only 5 minutes. That stuff should be pretty tough.

 

[Will L.]

Nitropropane, twinturbos, etc. They are strong but turns out they bounce of asphalt exactly the same.

 

[consaka]

That is a little cryptic. I had thought of titanium pistons a long time ago right after I thought of steel pistons. Cost of titanium would always be an issue. blowing a hole in one should never be an issue.

 

[Will L.]

I cant imagine somebody paying for them. This was a friend playing with some new machining tooling that had access to the free ingit remnant for material.

As for cryptic- we put in those pistons into an engine trying to run on straight nitropropane with twim gm4s running around 20 psi each. Our theory is the crankshaft gave out first, and most the rods and pistons ended up on the track with he truck going about 60mph. There is a book more of details but not mentioning the finite details I didn't think would leave it cryptic.

So, playing with insulating as well as helping heat the precups and other components is something we played with along the way. My end result is of the opinion of what I mentioned.

But I am all for other people doing things a bit differently. You might hit results that make big improvment. I just say if you are trying to learn, you have to compare each component on its own. Lets say yoh get a 10% gain in what you are doing. How much from the precups? Maybe everything else was really a 12% gain and the precups set you back 2%. Maybe he precups are responsible for 9% of the 10% gain.

Coatings get some impressive reults. We did differing metulurgy for our insulation. Please let us know how it turns out. Always cool to learn.

 

[WarWagon]

I would love to see the results as I have always wondered about coating and insulating everything to keep the heat out of the cooling system. Specifically coating the prechamber head surfaces. I know a member on here has experimented with coatings. Let me encourage you to try and clear up a possible misunderstanding you may have. The heat in and from prechamber parts changes a lot of things related to ignition of the diesel after injection.

"Once the engine is running the fuel does not need to hit a hot surface to ignite"

No! There isn't a thing correct about raw diesel hitting a hot surface to ignite. It's about hot diesel vapor getting hot enough spontaneously combust. If the diesel doesn't vaporize and reach the magic temperature it's going out the exhaust as useless unburned white smoke and/or wet stacking and into the engine oil. (Got an extreme example of diesel washed rings out of a 1992 6.5 project in my garage at the moment.) Where it gets the heat to evaporate completely then light along with injector droplet size matter. Higher pressure means you can get smaller droplets from a design standpoint.

You know the white smoke belching "dump truck driven through a Nitroglycerine plant" noise on a cold 6.2/6.5 engine with cold advance on vs. what a hot 6.2/6.5 engine sounds like. The hot glow plugs are intended to heat the prechamber not light the fuel hitting them. (They will evaporate fuel hitting them quick and some designs are moved into the spray pattern for this reason.) Ether as a starting aid is the same idea: heat. Ether burns before the diesel injection event attempting to drive the engine backwards, bend rods, disintegrate glow plugs, and break the starter off. However, it heats things up and allows the later injected diesel to evaporate and reach the magic light off temperature. The RPM being the same cold or at operating temp is an example of the amount of heat into cold air the prechamber provides during the intake and compression stroke and it's significant. The trade off is the losses on the power and exhaust stroke.

The question that can be answered is IF a coating/insulation can prevent enough heat loss on a cold engine to allow it to start and keep the engine running on heat of compression alone when up to temperature. Does the heat coming off the prechamber matter on the intake and compression stroke? Think of this: On a long grade going downhill in a Colorado Blizzard say Eisenhower Tunnel you can have the engine cut fuel so long that the air pumped through it cools it way down. The Thermostat is helpless fully closed when you are spinning the engine and "Northstar" air cooling it without any fuel being burned. Application of throttle is an eye burning white exhaust smoke event. So could the coating improve this?

Sure it's loss of power for the heat to be adsorbed into the metal. However an IDI needs heat to run and compression alone isn't enough. So it borrows heat from the last power/exhaust stroke to heat the air and diesel up. The best example I can give you is this: Correct timing and prechamber heat can be heard at 45MPH per Bill Heath's advice. At 45 MPH little fuel to maintain speed. Add fuel to speed up you get diesel clatter that goes away as heat builds up in the prechambers. This be the correct timing. How would insulating or cooling the precups change this?

Want efficiency? Get rid of the 10-15% loss the antique IDI design has and go DI. Then try coating the DI head and ports... After all IDI is from a low pressure injection system era where emissions didn't matter so much. Getting the big drops of low pressure injected diesel to evaporate and light so the dammed thing starts or stays running is a challenge. (NOx concerns are lowering compression making starting harder due to less heat from compression.)

Cracks are from stress. Temperature changing too fast, pounding, defects, etc. Too hot and shock cooling... Too hot will simply melt things. Is there a point the blowtorch powerstroke shocks the precups going too and from the cool intake stroke and cool diesel mist injection events? Perhaps the cold chamber diesel clatter provides more shock than a hot prechamber. Detonation breaks rings and pistons in gas engines... If the diesel injection mist builds up and then finally lights off I would suggest this is the detonation high stress arena and our beloved 6.2 signature school bus clatter sound.

That is a little cryptic. I had thought of titanium pistons a long time ago right after I thought of steel pistons. Cost of titanium would always be an issue. blowing a hole in one should never be an issue.

Context to decode Will above.
http://www.thetruckstop.us/forum/threads/megadeath-of-6-5.45288/

 

[Twisted Steel Performance]

Well, I have done the coatings to the cups & heads and I know the outcome of the test if anyone ever takes the time to do it themselves.. In fact I have coated different parts with different coatings with much success, but be advised their is a steep learning curve to be able to know for sure that your application process will give you the results you think they will, after all you won't really know till it's taken apart and checked after a hard test session.

Their are some coatings that can't be used inside the cly, they won't take the psi. funny thing is no one tells that part ...

Are you diy or sending to a shop ??

 

[consaka]

I cant imagine somebody paying for them. This was a friend playing with some new machining tooling that had access to the free ingit remnant for material.
As for cryptic- we put in those pistons into an engine trying to run on straight nitropropane with twim gm4s running around 20 psi each. Our theory is the crankshaft gave out first, and most the rods and pistons ended up on the track with he truck going about 60mph. There is a book more of details but not mentioning the finite details I didn't think would leave it cryptic.

Coatings get some impressive reults. We did differing metulurgy for our insulation. Please let us know how it turns out. Always cool to learn.

I claim zero knowledge of nitropropane. It sounds like it might be bypassing the injection pump. If that is the case you were really gambling. How did you control the timing? What compression ratio were you using? Sounds interesting to be sure.

 

[consaka]

Well, I have done the coatings to the cups & heads and I know the outcome of the test if anyone ever takes the time to do it themselves.. In fact I have coated different parts with different coatings with much success, but be advised their is a steep learning curve to be able to know for sure that your application process will give you the results you think they will, after all you won't really know till it's taken apart and checked after a hard test session.
Their are some coatings that can't be used inside the cly, they won't take the psi. funny thing is no one tells that part ...
Are you diy or sending to a shop ??

Pfft. You know you can't trust a shop. If you want to know what is in there you have to put it there yourself. This is the same reason I build all my own engines. So far I have had a LOT better success than my dad has and he is the one that taught me engine repair at the age of 9 and 10. Seems like the older he gets the less he likes to dig into the oily guts. for the last 20 years or so he has been buying "good" junkyard engines. "professionally" rebuilt long blocks. Problems with every single one. Example: One longblock ford 460 built in Seattle one head/valve never had the valve seat put in but tight clearanced enough it ran, for a while. Other problems I can't remember. lol One major headache after another.

What coatings did you find worked best? I plan on doing some experiments first before doing this engine. Experiments to just see how much difference can be expected. Just on scrap aluminum pieces of course.

 

[consaka]

"Once the engine is running the fuel does not need to hit a hot surface to ignite"

No! There isn't a thing correct about raw diesel hitting a hot surface to ignite. It's about hot diesel vapor getting hot enough spontaneously combust. If the diesel doesn't vaporize and reach the magic temperature it's going out the exhaust as useless unburned white smoke and/or wet stacking and into the engine oil. (Got an extreme example of diesel washed rings out of a 1992 6.5 project in my garage at the moment.) Where it gets the heat to evaporate completely then light along with injector droplet size matter. Higher pressure means you can get smaller droplets from a design standpoint.

Not sure why you are telling me this. I figure just about everyone knows this. The exception is the glow plug on cold start. We may have to agree to disagree on that since I believe it works two fold. It heats the air but the compression still does most of that work. It glows red hot and the fuel hits that it immediately turns into something finer than the injector could ever spray. That heat causes the fuel to start to burn which starts the chain reaction that is increased pressure to more burn of the fuel that has not yet ignited. Heat causes those spray droplets to turn to white smoke and thus combust. Finer high pressure injection droplets help that to happen faster than larger low pressure droplets. Cold start combustion starts right at the glow plug. That glow plug has no time to heat the precup itself thus that really doesn't play into the cold start at all. Easily proved with some experiments. Air is a pretty good insulator.

The hot glow plugs are intended to heat the prechamber not light the fuel hitting them. (They will evaporate fuel hitting them quick and some designs are moved into the spray pattern for this reason.)

Ok I am going to assume you mean they are intended to heat the AIR in the precup and not the precup itself. I find this to be somewhat implausible. So let's see. We can use my van for an example. I climb in and it is 30 degrees f outside. I climb in and turn the key on and flip the glow plug switch and count to 12. Crank it and it starts. 6 of those 12 seconds it isn't even glowing red. Plus the piston is down which means it is only heating something less than 1 out of the 18:1. What about the rest of the air in the cylinder. It isn't being heated at all. Not to mention the short time frame of 12 seconds is barely enough to heat the air a little bit around the glowplug itself. As that air starts to heat it also starts to heatsink into the cold head. if the glow plug was not in the fuel stream the engine would not start nearly so easily. Keep in mind that if the glow plug heated the fuel hot enough it would spontaneously combust without the aid of compression. Glowing red hot is pretty close to that temp. Every little bit helps but in a cold engine its the fuel hitting the hot glow plug that contributes the most. Nothing like a little hot fuel to get things going.

The question that can be answered is IF a coating/insulation can prevent enough heat loss on a cold engine to allow it to start and keep the engine running on heat of compression alone when up to temperature. Does the heat coming off the prechamber matter on the intake and compression stroke? Think of this: On a long grade going downhill in a Colorado Blizzard say Eisenhower Tunnel you can have the engine cut fuel so long that the air pumped through it cools it way down. The Thermostat is helpless fully closed when you are spinning the engine and "Northstar" air cooling it without any fuel being burned. Application of throttle is an eye burning white exhaust smoke event. So could the coating improve this?

I have done this on many diesels and the only ones that don't have this problem are older 6.2. I am thinking the pump never shut off the fuel to these engines. Pumps may differ and others likely know more about that than I do. I do know on pumps that pretty much shut the fuel off the engine can get cold enough it won't want to run. My Marine pump seems to be that way. We went through the mountains of Wyoming on our way back from WI just a month ago. Some of those grades are 10% with 7% being very common. And they are long grades too. And it got cold at the top. Around 9,000 feet of elevation if I remember correctly. Going down was a long engine braking ride. My low temp on the EGT gauge was on a lot. It comes on at 200 degrees. Even the antifreeze temp started dropping. All the engine is doing is pumping that cold air. An engine can go from 1000 degrees to less than 200 pretty quick under those circumstances. The only thing you have in your favor is the engine RPM at the bottom of the hill. If you keep it at 2000 rpm you will be fine because you are not losing the 60% compression that you are when you are cranking a cold engine. If I let it get down to idle at the bottom of the hill I was pushing out white smoke on possibly 2 cylinders. Apparently 2 have slightly less compression than the others. Not sure why. possibly and extra copper washer(heatshield? I think some of you call it) stuck in the head and another accidently on it would cause a slight drop. Otherwise a possible broken ring? Dunno. dont have any blowby at all.
Now would coatings help? Sure they would help because they mitigate the heat sinking that is constantly going on from the hot compressed air to the head and precup area. The coating keeps the metal cooler because it allows the heat to stay on the other side of the coating. If I am interpreting the info Buddy posted correctly. We need 500 degrees to spontaneously combust the fuel on injection. At 32 degrees ambient the engine at 18:1 CR should be generating 1075 degrees at TDC. That is in a running engine before ignition. Should be plenty since losses to heatsink and blowby dramatically decrease as engine speed increases.

Sure it's loss of power for the heat to be adsorbed into the metal. However an IDI needs heat to run and compression alone isn't enough. So it borrows heat from the last power/exhaust stroke to heat the air and diesel up.

Actually all diesels need heat whether they are IDI or DI. The air starts heating as soon as it hits the intake manifold. To say heat from compression alone is not enough is not entirely true. See my last example. True we would be in trouble if we could build a 100% efficient engine with no heat loss. It would only run where the temp was high enough for the compression to generate enough heat to spontaneously combust the fuel. My previous example based on memory and info posted by buddy, shows this to be somewhere below freezing. In 20 below zero weather we rely on wasted engine heat to heat the air entering the engine. In that circumstance we have heat stored in the block and head to heat the uncompressed air so when we compress it we get the 500plus degrees we need to ignite the fuel. If our engine was 100% efficient we wouldn't even need glow plugs to start it when cold. In fact it is doubtful they would help much at all when super cold unless we left them on. We would have to do some clever engineering on such an engine to get it to run below 0 degrees. On a hot summer day we can start without the glow plugs. Obviously that is started on compression alone.

Cracks are from stress. Temperature changing too fast, pounding, defects, etc. Too hot and shock cooling... Too hot will simply melt things. Is there a point the blowtorch powerstroke shocks the precups going too and from the cool intake stroke and cool diesel mist injection events? Perhaps the cold chamber diesel clatter provides more shock than a hot prechamber. Detonation breaks rings and pistons in gas engines... If the diesel injection mist builds up and then finally lights off I would suggest this is the detonation high stress arena and our beloved 6.2 signature school bus clatter sound.
Context to decode Will above.
http://www.thetruckstop.us/forum/threads/megadeath-of-6-5.45288/

I will respectfully disagree on precup cracks. It matters not really how fast it heats and cools. Cracks will form anyway. The cracks are a direct result of the metals ability to be elastic. Apparently the newer ones have a better formulation than the older ones. Any time you have a chunk of metal that gets super hot where it is thin you will have a high stress area when it cools. When it glows red hot it is expanding. When red hot it can compress onto itself to relieve that stress. Now when it cools it is under high stress to pull apart. You see that action in the T precups. It happens at all 4 corners where you would expect the leverage faction of the stress to be greatest. Red hot is pretty close to melting depending on the material. For regular soft steel it is really close and the metal can be flattened by tapping with a hammer. titanium is a good example of the other side of the spectrum. It can glow bright yellow and still hold its form quite well. Which is why it is used in jet turbines and turbo turbines.
Apparently the diamond precups are made out of something close to as tough, or tougher.

 

[Will L.]

Well, I have done the coatings to the cups & heads and I know the outcome of the test if anyone ever takes the time to do it themselves.. In fact I have coated different parts with different coatings with much success, but be advised their is a steep learning curve to be able to know for sure that your application process will give you the results you think they will, after all you won't really know till it's taken apart and checked after a hard test session.

Their are some coatings that can't be used inside the cly, they won't take the psi. funny thing is no one tells that part ...

Are you diy or sending to a shop ??

What is your take on coating precups? How have you tried and what results? Insulating cup from head, cup from flame, or both. I know great results on all the other stuff you did, but what about precups seperate?

I claim zero knowledge of nitropropane. It sounds like it might be bypassing the injection pump. If that is the case you were really gambling. How did you control the timing? What compression ratio were you using? Sounds interesting to be sure.

2 injection pumps. One for diesel, one for nonompressables. When i said straight nitorpropane thats not exactly right, we used about 1% gasoline and 1% diesel to ignite the nitro propane. We did the propane in the air system and via pumps.

Compression numbers I promised my teammates not to share, but can say never lower than 16:1. Yeah, things went boom, haha.

 

[consaka]

2 injection pumps. One for diesel, one for nonompressables. When i said straight nitorpropane thats not exactly right, we used about 1% gasoline and 1% diesel to ignite the nitro propane. We did the propane in the air system and via pumps.
Compression numbers I promised my teammates not to share, but can say never lower than 16:1. Yeah, things went boom, haha.

Would you say the boom was caused by preignition of the fuel not going through the pumps but rather carried on the air? Or just flat out too much cylinder pressure? If I was doing anything that radical I'd be retarding the timing. The faster the flame rate the more retarded it would be. Honestly I think you could get away with quite a bit if that pressure had somewhere to go.

 

[Will L.]

Over pressurization. Too much gunpwder in too small a cannon. Yes timing was retarded, probably not as much as me.

GM's precups were all made of same inconel. Design differences is all.

Rate of heat expansion and cooling contraction is the problem for cracking. Take a #12 rose bud on your torch and heat one up to 2400f. Increase temp 100 degrees per minute. Maintain the top heat 1 minute, Cool it down at same rate. It will be fine.

Now the fun part of experiment begins.
In a 5 gallon metal bucket mix: 2 gallons water, 2 lbs crushed ice, 12 oz salt, 24 oz water soluable cutting oil (water wetter will do) as we don't like the Leidenfrost effect here. Stir well until salt is disolved and 3/4 ice melts.

Morgan Freeman voice over (while heating the metal to the same temperature in 3 minutes or less):
"Heat expands metals from the outside in, and cold contracts in the same manner. When it occurs to rapidly, the thinner material expands and contracts at a different rate than the thicker area of the component. Since our metal is not pliable enough, we get..."

Now drop the precup into our bucket-o-fun as Morgan says "...THIS!!"

Dont want to ruin a good precup? Do it with a piece of inconel flat bar 1" wide by 2" long and drill (machine) one side full of a few 1/8" holes- just dont use my drill bit-haha.

This is why annealing process is so crucial for many things that are temperature critical.

 

[consaka]

I get what you are saying. My point was that in the head the thicker mass of the precup is heat sinked and will only get so hot while the thin area around the nozzle will get red hot. This temperature differential is where the problem occurs. The new stuff must be really tough or designed differently than these T-cups.
In your experiment you are heating the precup hotter than it would normally get. Then you are quenching it. The thinner area around the nozzle quite naturally is going to cool and shrink first. Thus crack etc etc. Experiments are great and all but they need to duplicate original conditions that cause the problem.

 

[Will L.]

I had a guy tell me metal fatigue from vibration never causes cracks in sheet metal, that everytime you see it that is always manufacturing defects. I demonstrated by bending some back and forth rapidly and it cracked.

Did I use more force and motion- yes. But the way show demonstrate a long term problem is to amplify the forces to make up for the time difference.

Best way I can explain is to blow something to larger porportion for the example. Probably why Im bot a teacher. Kinda dont know how else to explain it. Hope the info helped, if not not biggie. Let us know how it goes.