meltdown -- common rail style

pilot injection is probably making these problems worse. i have found distorted tips on a few of these failures not really sure why but the end of the tip is deformed and the angles of the holes are off. does anyone know what the injection duration is on the tuning he was running?

ted
 
The 03 04 trucks don't have the post injection event, correct. If that is the case maybe the post injection event, lower timing, and piston design are what the cause of the 04.5 and up engines to have more of a problem. Just a thought, just trying to learn more and more about these trucks.

Joe
 
I melted 2 sets of 600 series switched to 55's and melted the hell out of those. Piston design I think has little to do with it.

I will start a new thread for this....
 
I have spent the last 4 years trying to get my truck to run clean. (lean)
Now to find out it may be detrimental. WTF
I was always told diesels cant run to lean more air the better.

JP, sorry for your loss

I think its time for some of the talanted minds to help out here.
I know Don has been a big supportor of water injection on the CR's
Its been said, running 700 /800 Hp is a delicate balance keeping them alive.
Maybe alot of us on on the edge.
doug
 
doug60 said:
I have spent the last 4 years trying to get my truck to run clean. (lean)
Now to find out it may be detrimental. WTF
I was always told diesels cant run to lean more air the better.
Click to expand...


That was my understanding also. I know you can burn up a gasser in nothing flat when it runs lean. I was under the impression diesels ran cooler with less fuel in the given mix.
 
bdp said:
I melted 2 sets of 600 series switched to 55's and melted the hell out of those. Piston design I think has little to do with it.

I will start a new thread for this....
Click to expand...

Keep us post Bean- id like to know what your doing now. thanks
 
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
 
Think you on a good track, Im going to get with Bean and see what is different about our setups.

Also Marco, did you get my reply PM about the timing question?
 
Without a doubt, heat over time is the issue, there's a reason Schieds and all the other big pullers/tractors are running water, the pistons can simply not sink that much heat.

Even with my steel pistons I'm using the water injection, valve's can't like the 2000+ either.

I'd bet a bag of marbles both Bean's and jlibert's engines would still be fine it they were running a properly set up water injection system.
 
Last edited:
You think the water would also help in the case of a bad injector that could cause melting??


I guess I need to look into a water system....I know Nothing about them at all..
 
Joesixpack said:
Without a doubt, heat over time is the issue, there's a reason Schieds and all the other big pullers/tractors are running water, the pistons can simply not sink that much heat.

Even with my steel pistons I'm using the water injection, valve's can't like the 2000+ either.

I'd bet a bag of marbles both Bean's and jlibert's engines would still be fine it they were running a properly set up water injection system.
Click to expand...
If they're running a 2.6 class then they won't be allowed to run it. :bang
 
kas83 said:
How is running a diesel lean hurting it and causing more heat?
Click to expand...

esp. with twins the lean condition will elevate cylinder pressures will it not ?
Cummins may be different than what I'm used to though.
 
With all this talk about high rpm's and not enough time to cool the crowns...what about running at 4K being out of the usable area of the injector???

Since we all put aftermarket valve springs because stock ones are good to 3500, what if the stock ball/spring in the injectors are also only good to 3500??

At 3500rpms and 3 injection cycles per event...thats alot of firing per second (sorry my math isint working too well today) what if at 3800 your esentially putting the injector into "Valve Float" and the injector is staying open and dumping fuel???

Just a thought...
 
2007 5.9 said:
With all this talk about high rpm's and not enough time to cool the crowns...what about running at 4K being out of the usable area of the injector???

Since we all put aftermarket valve springs because stock ones are good to 3500, what if the stock ball/spring in the injectors are also only good to 3500??

At 3500rpms and 3 injection cycles per event...thats alot of firing per second (sorry my math isint working too well today) what if at 3800 your esentially putting the injector into "Valve Float" and the injector is staying open and dumping fuel???

Just a thought...
Click to expand...

That's a very good thought!
 
2007 5.9 said:
With all this talk about high rpm's and not enough time to cool the crowns...what about running at 4K being out of the usable area of the injector???

Since we all put aftermarket valve springs because stock ones are good to 3500, what if the stock ball/spring in the injectors are also only good to 3500??

At 3500rpms and 3 injection cycles per event...thats alot of firing per second (sorry my math isint working too well today) what if at 3800 your esentially putting the injector into "Valve Float" and the injector is staying open and dumping fuel???

Just a thought...
Click to expand...

So with my semi-retarded math I think that at 4K the injector fires 50 times per second with all three injection events ocourring.

Heres the math...correct if wrong...

4000\60=66.67 rps. 66.67\4(numbers of strokes per cycle)=16.66 revolutions per power stroke. 16.66*3 (injection events)=50 injector fires per second.

My math might be off....
 
p-pumped said:
does anyone know what the injection duration is on the tuning he was running?

ted
Click to expand...
marco would probably be the only guy that would be able to tell you that.

Marco said:
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
Click to expand...
I think you make a very good point, and are probably right. The only thing i can think of that doesn't fit is how lots of 12v's are living with lots of fuel at higher rpms than what our common rail engines see.

Smokem said:
once the heat reaches the crown of the piston, failure is bound to happen. In every picture you can see where the bowl lip is flat between the jet marks, even slight beginning points on #3, and 5.
Click to expand...

Looking at the crown, on many pistons the crown is in good shape where fuel was being sprayed, but melted between the jet pattern. This goes a long way towards convincing me that more fuel may help these pistons live.

a/f ratio meter anyone?
 
what was the big missing and white smoke at the end of your pull..... thats what my truck did when i melted my two pistons.. some noise them and bunch of missing and white smoke..
 
It's possible your pistons that where not totally melted had better oil cooling. Remember how we were talking about putting a torch to aluminum? The aluminum will look okay until it reaches a certain temp, once reached, the alum just falls apart. Those cylinder temps or piston temps could have been just slightly cooler for whatever reason.

This is the reason for every motor we build now has coated pistons. We are trying to keep the piston temp down. Let's take a perfect injector situation and make that motor run 26K rail pressure all of the time for lots of miles (remember perfect injectors). If the cylinder temps and piston temps are down, you should never have pistons with burnt rims. We are seeing burnt rims where the piston is getting hot though. As soon as that rim burns, it allows the flame to roll over the top. Once the flame is on top where there is a lack of air, the temp of the piston increases quite a bit. This is where the piston falls apart or is pushed apart. The motor only needs a couple of revolutions to do what it did to the pistons if they are at too high of a temp. Like stated above earlier, aluminum can melt away in a split second.

1,400* unfortunely means nothing on these CR motors. The only thing it really matters for is the valve and the valve seats. A/F will have nothing to do with it either.

The fuel just barely helped keep the sprayed section ok. It was dropping the temp of the piston in those 5 spots just slightly. To cool the whole piston with fuel probably would have hurt things even more.

Coating pistons is the only way to make the CR pistons live in high rpms (especially the 04.5+ piston). Cummins may have spent 10,000 in design of this piston, but they messed up. As Weston said earlier, and I have said always, the 03-04 piston is better in design. There is a reason Cummins when back to it for the 6.7.

As the pictures show, fuel wasn't on top of the piston rim. The flame did travel up there though. This could have possible still happened on stock timing.

One question to everyone, does this new ULSD burn quicker or longer?

Running lean will not hurt these pistons, remember on my motor, at 1K wheel the temps would not go ever 1,250 and there was no smoke. The piston were totally fine. This kinda rules out lean conditions causing this.

Okay, i'll stop rambling...
 
chrleb1 said:
Running lean will not hurt these pistons, remember on my motor, at 1K wheel the temps would not go ever 1,250 and there was no smoke. The piston were totally fine. This kinda rules out lean conditions causing this.

Okay, i'll stop rambling...
Click to expand...



Comparing a few seconds on a dyno, is nothing like 25-30 on a pulling sled.
I doubt your egt guage can even stabilize in that time.

I guarantee you, there is no way these engines can hold 1000 for that long, without excess fuel cooling, or water.

That coating on Bean's pistons sure held up great.
 
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