CR melted piston discussion, why, why not, and for the love of god how not to..

[Dockboy]

If its workin for Greg its gota be tough.....oke:

:hehe:

I plan on tearing the engine down this winter to check it over, so we will see.

By the way, I don't run a pressure box either

 

[Joesixpack]

:hehe:

I plan on tearing the engine down this winter to check it over, so we will see.

By the way, I don't run a pressure box either

Smart man......that will be the last run I make on the mp8, need more fuel, get some bigger holes.

[/IMG]

Never seen so much smoke in my life.....solenoid blown off = injector stuck full open......

 

[chrleb1]

So Mr Brown....... What r u doing to keep things alive? Or what things are you NOT DOING?
Thanks



Has anyone melted there motor with out running extra rail pressure?

We have blown up or melted down our fair share of pistons, motors, and turbos in the quest for that extra little bit of power. These are things we have just learned from what we have destroyed. Everytime we push the limit, we learn more and more. Most of the time people are burning things up, it's because they aren't doing everything to cool the pistons. They think the EGTs are low and that means they are safe.

I think coating and and water is an absolute must. I have a motor here in the shop that melted some pistons.... stock injectors, tnt, twins. The problem was he was in it too long pulling a long hill. EGTs where in check, but the cylinder temp just kept rising and eventually burned the piston. This is an example the pistons melting at 475hp. What could have been done..... water.

These are all just ideas. We are pushing a 6 cylinder motor to the point of breaking.... things happen. We just have to come up with the next thing to handle the next performance goody that is built for us.

 

[soulezoo]

Anyone tried putting the 03-04 ecm on the 04.5-05 and keeping the newer pistons and stix? Possibly use the qsb marine pistons?

This is the setup I am currently using... I have not melted anything, yet, but doesn't mean this is the magic bullet either.

I have cut and coated 06 pistons and 06 stix... 04 ecm.

So far it is working well.

 

[SledPuller21]

I don't think it'll matter what anyone does for tuning. It is a matter of making power for a long time and the piston temp just keeps on rising. The only way around it is to use sometime of artificial cooling (whether it is some extreme coating or water). Piston temp has to be brought down, period. Over-fueling will not help things out. It could actually make things worse because of the longer burn of the 04.5+ programming.

Tuning has everything to do with the problem...

 

[jsf350]

We have blown up or melted down our fair share of pistons, motors, and turbos in the quest for that extra little bit of power. These are things we have just learned from what we have destroyed. Everytime we push the limit, we learn more and more. Most of the time people are burning things up, it's because they aren't doing everything to cool the pistons. They think the EGTs are low and that means they are safe.

I think coating and and water is an absolute must. I have a motor here in the shop that melted some pistons.... stock injectors, tnt, twins. The problem was he was in it too long pulling a long hill. EGTs where in check, but the cylinder temp just kept rising and eventually burned the piston. This is an example the pistons melting at 475hp. What could have been done..... water.

These are all just ideas. We are pushing a 6 cylinder motor to the point of breaking.... things happen. We just have to come up with the next thing to handle the next performance goody that is built for us.

Thank you Eric,

What water kit do you recommend- my truck is not an every day driver- but does see the drag strip every now and then.
Thanks

 

[chrleb1]

I don't really have a recommended kit. Anything that is going to last and perform well will work. There are a ton of kits out there. You need to get everyones feed back and opinion of whose kit is better, then make a decision. You could also put your own kit together.

 

[Kman9090]

So pretty much the conclusion is if you are running big horsepower it's not if your motor will meltdown it's just when will it? Mine melted down the first time with 66,000 miles on it because I had a few injectors get hung open. Now I am currently on 100,000 miles with about 40 pulls. Motor is decompressed as well but I am only running 100 horse injectors as I also need to drive this truck occasionaly on the street. I have never ran the TST though but will be running it at the next pull.

 

[HIGH TECH RAM]

I think heat soaking things plays a huge part. You guys playin with the current TST are flirting with melt down IMO...

 

[outlaw99]

well im going to go ahead and put my truck back together with all 06 stuff again and hope for the best...lol

 

[mikmaze]

has anyone tried going with a higher flow rate oil pump, getting more oil to the bottom of the piston via the squirters could help pull out a little more heat, then again, in the time it takes to get the heat through the piston to the bottom, the top is most likely vaporized already, just trying to figure out loud.

 

[KILLER 'B']

Seems to me like the CR injection systems are beginning to burn fuel TOO efficiently, to the point where the gasser logic of "rich = cool, lean = hot" is coming into effect.

Diesels are opposite.. Rich is hot, lean is cool.

 

[outlaw99]

nothing lean is cool????? it doesnt matter heat is heat fuel will put the heat out... why do you think it hard to get truck to light with alot of fuel..

 

[Begle1]

Diesels are opposite.. Rich is hot, lean is cool.

That mantra is an oversimplification germane to airflow instead of fuel combustion.

"Rich", as in black smoke, often belies afterburning, which causes the pyrometer to register higher EGT's, but is a result of an inefficient combustion, which puts less heat in the combustion chamber. Injected fuel that doesn't burn is also a coolant akin to water injection. This can be seen when a truck dumps too much fuel into the engine down low and has trouble lighting its turbochargers.

"Lean", as in the beautiful high-power light gray haze a lot of tuners aim for, can register on a pyrometer as a lower EGT, because it's a more efficient burn and is putting more heat into the combustion chamber. This can be seen when you advance your injection timing, and your EGT's and smoke both drop significantly, but your cylinder temps increase.

In the gas world, when you add air you add fuel along with it, and the air-fuel mixture burns with an efficiency largely dependent on the stoichiometric ratio, because the fuel is already diffused with the air and doesn't have a hard time finding oxygen to react with. In the Diesel world, you add fuel independently from air, and the efficiency of the fuel burn is dependent on the injection system's capability to diffuse the fuel into the air instead of the stoichiometric ratio.

A Diesel with greater airflow is usually going to run cooler, and that's where the "rich is hot, lean is cool" maxim applies, but just having more air doesn't mean that the fuel is going to burn any more or less efficiently. With a given amount of air flow, a P-pump is going to tend to burn "rich" and cool, because the fuel is not as well atomized and it has a hard time finding enough oxygen to react with; a common rail is going to run "leaner" and hotter because the fuel diffuses through the oxygen exceedingly well.

 

[mikmaze]

ok, where did ya copy paste that from ?

 

[Big Swole]

Nicley Put!!!!!

:ft:

That mantra is an oversimplification germane to airflow instead of fuel combustion.

"Rich", as in black smoke, often belies afterburning, which causes the pyrometer to register higher EGT's, but is a result of an inefficient combustion, which puts less heat in the combustion chamber. Injected fuel that doesn't burn is also a coolant akin to water injection. This c:ft:an be seen when a truck dumps too much fuel into the engine down low and has trouble lighting its turbochargers.

"Lean", as in the beautiful high-power light gray haze a lot of tuners aim for, can register on a pyrometer as a lower EGT, because it's a more efficient burn and is putting more heat into the combustion chamber. This can be seen when you advance your injection timing, and your EGT's and smoke both drop significantly, but your cylinder temps increase.

In the gas world, when you add air you add fuel along with it, and the air-fuel mixture burns with an efficiency largely dependent on the stoichiometric ratio, because the fuel is already diffused with the air and doesn't have a hard time finding oxygen to react with. In the Diesel world, you add fuel independently from air, and the efficiency of the fuel burn is dependent on the injection system's capability to diffuse the fuel into the air instead of the stoichiometric ratio.

A Diesel with greater airflow is usually going to run cooler, and that's where the "rich is hot, lean is cool" maxim applies, but just having more air doesn't mean that the fuel is going to burn any more or less efficiently. With a given amount of air flow, a P-pump is going to tend to burn "rich" and cool, because the fuel is not as well atomized and it has a hard time finding enough oxygen to react with; a common rail is going to run "leaner" and hotter because the fuel diffuses through the oxygen exceedingly well.

 

[KILLER 'B']

Agree..

"Rich", as in black smoke, often belies after-burning, which causes the pyrometer to register higher EGT's, but is a result of an inefficient combustion, which puts less heat in the combustion chamber. Injected fuel that doesn't burn is also a coolant akin to water injection. This can be seen when a truck dumps too much fuel into the engine down low and has trouble lighting its turbochargers.

"Lean", as in the beautiful high-power light gray haze a lot of tuners aim for, can register on a pyrometer as a lower EGT, because it's a more efficient burn and is putting more heat into the combustion chamber. This can be seen when you advance your injection timing, and your EGT's and smoke both drop significantly, but your cylinder temps increase.

In the gas world, when you add air you add fuel along with it, and the air-fuel mixture burns with an efficiency largely dependent on the stoichiometric ratio, because the fuel is already diffused with the air and doesn't have a hard time finding oxygen to react with. In the Diesel world, you add fuel independently from air, and the efficiency of the fuel burn is dependent on the injection system's capability to diffuse the fuel into the air instead of the stoichiometric ratio.

A Diesel with greater airflow is usually going to run cooler, and that's where the "rich is hot, lean is cool" maxim applies.

Disagree and why...

Just having more air doesn't mean that the fuel is going to burn any more or less efficiently. There is too many variables in this statement. If there is proper air/fuel ratio, there will be maximum efficiency.

With a given amount of air flow, a P-pump is going to tend to burn "rich" and cool, because the fuel is not as well atomized and it has a hard time finding enough oxygen to react with. I think that with the right injection system and turbo set-up, a P-pump truck can run jut as efficiently as a common rail.

a common rail is going to run "leaner" and hotter because the fuel diffuses through the oxygen exceedingly well. This happens, because of the increased atomization effect with a common rail injection system. The better the atomization, the better the burn, the better the burn, the hotter the fire, the hotter the fire the better it runs.. Shouldn't it? that's why it was invented.

An Audi R10 race car has a 5.5 liter v12 Common rail engine with a diesel particulate filter.. It has twin turbos with a 1.57" inducer and manages to produce peak 700hp and continuous 600-650hp. All this with no smoke. Why because of the advanced common rail injection system designed for the engine. It was designed to race for an extended period of time at sustained maximum RPM at max fuel......

The Cummins Common rail Injection System was designed to make the power is had to make, while obeying emission standards, and staying quiet so the average 'Joe Shmo' can have a quiet, powerful, dependable truck... Chips and boxes increase timing and duration, but do not get rid of multiple events. (that I know of, enlighten me if there is) These multiple injection events coupled with increased timing and increased amounts of fuel is what cause melted pistons in common rails.. These extra events were added for noise emissions and exhaust emmisions. If the first injection event doesn't burn and stays raw in the chamber and is ignited by the second event there might as well be a OXY-Acetylene torch aimed on the lip of your pistons..

If what you say is true than all the common rail guys have to do is put big nozzles in, turn down their rail pressures, decrease duration, and have one injection event... :bang As RPM increases Cylinder Pressure decreases. Cylinder temperature and pressure gets so high in common rails, because of the multiple injection events coupled with high timing and duration... With that being said, diesel fuel burns very slow compared to other fuels. With this scenario, the actual combustion is fighting against the upward travel of the piston, resulting in extremely high temperatures and pressures. (this is much like high timing in P-pump trucks, however, with a mechanically controlled injection pump, there is one event and has a relatively short duration) So you have not only one event with increased timing, you have multiple..


Diesel Air/ Fuel Ratio for max power: 18-22:1 Is this always possible? no...

Did you ever put an O2 sensor in a common rail's exhaust to see what their actual air/fuel ratio was compared to a 12 or 24 valve?

 

[KILLER 'B']

Marco's post from the other thread!!! Makes sense to me!!



For me it's as simple as too much power for too long and combined with high RPM's.

Let me expand. Let's say the engine is turning 100 and each cylinder is fired once a second. That gives the piston one second to cool down before the next power stroke. Double the RPM, half the time for the piston to cool down.
See where I'm heading?

Now, if the piston does not have the time to cool down between the power stroke(s) that will create hot spots in the piston bowl for sure thus lead to uncontrolled burning of the injected fuel. In that scenario, timing? WHAT timing? The fuel starts to burn whenever it comes into contact with the hot spot.

Then more I think about it, then more I'm convinced that I'm on the right track. OK, but why 2 of 6 injectors have no damage then? The reason could be "cylinder contribution" if in these holes the injectors did inject a little less fuel, or they were down a little on compression or the head did flow more air or...

Possible solution(s)?
-Different cam with more overlap to scavenge ( cool ) the pistons better?
-Less RPM ( more cool down time ).
-Different piston bowl design.
-Steel pistons.
-Pure water injection.
- I'm sure a lot of you can come up with better solutions than mine

Marco

:clap: !00% correct

 

[outlaw99]

I agree with you 100% alot of us have touched base with the injection theory only if we had efi live to shut of certain injection evens mostly post injection... I would leave pre injection becasue these trucks would be noisy as hell without it.. the run bigger hole injectors with one less event..

 

[Big Swole]

I agree with you 100% alot of us have touched base with the injection theory only if we had efi live to shut of certain injection evens mostly post injection... I would leave pre injection becasue these trucks would be noisy as hell without it.. the run bigger hole injectors with one less event..

I would LOVE to have just one event and have my CR sound like a12V....And the mileage!!!!