Melting CR's. Timing? RPM? Multiple INJ?

1911 guy

1911 guy

Trunk Monkey
Joined
Nov 10, 2007
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131
I have an 05 and this melt down thing has my attention. Im searching post after post about melt downs. Im getting the idea that the multiple injection cycles of the 04.5-07 CR's combined with too much timing is the main reason. Something i read in a post puzzled me in that RPM over 3400 can cause a melted piston. In all my knowledge im not seeing how this could be a factor. Since we are on the subject of RPM. Will the bottom end hold this speed reliably without any mods? Now granted the valve train will need upgrading to support this kind of RPM. Any thoughts are appreciated.

Thanks, Corey.
 
As RPM increases...window to cool piston crowns decreases.

Better airflow at higher RPM's will greatly reduce meltdowns...not just more but better, cooler, denser air.
 
Very good point. One i had definantly not thought of. So with that said shouldnt a cam with longer valve overlap duration affect the cooling of the piston at the top of the exhaust stroke?
 
1911 guy said:
Very good point. One i had definantly not thought of. So with that said shouldnt a cam with longer valve overlap duration affect the cooling of the piston at the top of the exhaust stroke?
Click to expand...

Bingo!!!

Take the in-cylinder EGR out of the equation and now on every intake stroke you get a cylinder full of fresh cooler air, instead of half recycled exhaust and half fresh air!!

Most if not all aftermarket cams remove the EGR effect.

FWIW, I am running a Hamilton Big Stick...and love it!!
 
Not if your fighting huge backpressure, reversion becomes the issue.
(On the valve overlap)
 
Joesixpack. If i understand corectly, what your saying is, If there is excessive back pressure between the combustion chamber and the turbo charger exhaust gas could potentialy push all the way back into the manifold and contaminate the intake air charge of another cylinder on its intake stroke?
 
Joesixpack said:
Not if your fighting huge backpressure, reversion becomes the issue.
(On the valve overlap)
Click to expand...

Change the cam and remove the exhaust restriction and that becomes less of an issue than injection sequence.

Changing the cam profile does help a lot with the timing issue as the stock cam does not like a lot of fuel too early in the sequence.

The biggest problem seems to be at high rpms the 3rd event is dumping too much fuel outside the bowl because of where it is the piston travel sequence.

AFAIK, the current crop of programmers cannot materially effect where in the injection sequnce the fuel is being delivered, only the amount. The stock protocols are still controlling the events and those need to be modified to adjust where the bulk of the fuel is delivered.

Either maintain a small amount of fuel in the 3rd event and the bulk in the main, split it better across the 2 events, or even remove the 3rd event for optimizing the burn. The stock bowl design and injection timing just does not lend itself well to high fuel applications. Done correctly multiple events are going to be more effective but there other parameters that need to be adjusted to take advantage of it.

It is an emissions engine and designed for certain parameters after all.
 
I removed all the BS in this thread! Keep it on topic, ALL PARTIES!
 
Nooooooo I needed a pissing contest so they would spill their guts!!!!!
 
In the last 3 years I have rebuilt close to 100 CR engines. Out of those 50-60 had injector issues that either melted the piston or aided in dropping the valve seat. 10-15 had air filter issues that sanded the engine. 4 or 5 resulted from turbocharger failure. And 2 to 3 resulted from excessive temps while playing.

Out of around 100 85-90 were 04.5-05's, 10-15 03-04's and not a single 06+
Most of the failed engines had no fueling modifications. A big percentage of the engines with melted pistons had a burned number 6.

In the same time we did probably 20 1998-2002 24v engines
most of those were split 53 blocks, sanded engines , and a couple dropped valve seats on 02's

In the same time We did 10-15 12v's Most of these were #1 or #6 scoring. or sanded engines. In that same time we did a lot of head gaskets on 12v's. I have seen a lot of engines that had been so hot that the piston bowls had cracks in them, the heads had cracks, the manifolds had cracks the turbine housings had cracks and they all still ran fine.

From all of this I have seen that the amount damaged 03-04's was about the same as the 98-02's , and that most of the 04.5's and 05's had no fueling modifications whatsoever. I think this directly points to the injector spray angles and the open piston bowl of the 04.5+ along with the pistons inability to reject heat and cool. Throw in the last injection event and you have an engine prone to melted pistons. The 03-04 pistons have more crown mass that has the ability to accept more heat without being "heatsoaked" to the point of melting. The early pistons also concentrate the flamefront in the center of the piston and subject a smaller area to the extreme temps of combustion so that less heat is transferred to the piston. A lot of the early engines even had the smaller piston cooling jets and still ran just fine without melted pistons.

Air flow improvements to cool the cylinder would help quite a bit. But doing a cam while keeping a 9cm housing wouldn't do much. Having an aftermarket turbo that had a broader boost range without excessive drive pressure would help a lot as well. I would suggest this before a cam. The aftermarket turbo combined with a cam would be the best for cooling.
I am no expert on injection events or programming, but have observed a lot of failures in the last few years. This is just my observations. Draw from it what you may. On a side note it is nice to see that cam threads are nice and civil again. I guess nozzle threads are the new cam threads. Don, it looks like you have two front lines, so did the Germans.

Zach Hamilton
 
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Forgot to mention that most of the high hp trucks we built were 06 trucks. Many over 700 and 2-3 almost 1000hp daily drivers all had healthy injectors and all have had great luck with no damage.


Zach
 
So since i am adding a larger cam to my set up do i need to upgrade my 62/71/14 turbo? When i was running stock injectors and this turbo there was nothing i could do to break 1300 on the pyro. I dynoed 585 and was only pulling 39psi. Since adding 90hp nozzles i can peg the pyro gauge in a matter of a few seconds. I kept the turbo gated to 39 to save HG. now with the addition of studs i plan on cranking it up. Will a higher boost level potentialy run cooler? I know this turbo can produce 60psi but is it likely that it will be out of its eficiency range at theese pressures? I know drive pressures play a big roll in EGT's. Is there any way to measure theese pressures? And how do you determin a good drive pressure to boost ratio?
 
when I melted my #4 piston, I believe it was mainly do to lack of air and too much fuel. Something to keep in mind....that 62 isn't a whole lot bigger than the stock turbo.

Since my melt down I've ran a Silver bullet 66 and only ran 50psi so, I don't think you'll want to be pushing that 62 to 60psi ! More boost doesn't mean more power or cooling.

1:1 is the optimal drive psi you want to see.

A correctly set up truck isn't gonna melt pistons IMO. Since my build, I've frequently seen 1600F ( by the 1/8 ) and 29Kpsi RP at WOT. I've ran the truck like this for well over 2 years without issue. Not going overboard with the timing, injectors matched to the air you have and plain common sense are big factors IMO to avoid a melt down
 
I will throw this into the mix, because it is kind of alarming to me (but good for business ;->


Last month we had a 125k '06 come in with a no start. Sounded bad, fuel through the intake, etc. Pulled the head. Found what amounted to combustion mud in 4 cylinders. Bad injectors. Rebuilt the motor.

100k 2006 drops seat and burns gasket. Cracked head. Running Smarty, 90hps, bigger charger. Ran some drag runs and a couple of sled pulls.

Low mile 2006 dropped a valve seat and toasted the gasket. 90hp injectors, and Smarty. Sent to dealer for warranty. Was a 6speed truck and had done some sled pulls, so figured high heat/rpm was the cause

Jason checked his contribution on his 2006 and found two low. Same scenario as above, but he had a cam, bigger turbo, stock injectors/cp3.

Two days ago, 2005 with 135k comes in with a funky noise. Eats a quart of oil every 400 miles. Excessive blowby. Pulled head, found #1 destroyed. Looks like a ring came apart. No obvious damage to the head and valves/seats on #1 look great.

Yesterday, no BS!!!, TWO trucks (2003 5speed SO truck with 135k and a 2007 with 155k, both stock) come in with poor running, smoke, funky intake/exhaust sound. The '07 is down 12% in cylinder two and he has already replaced injectors. The '03 runs so bad I told him to leave it. Both are getting the heads pulled over the next couple of days and I can't wait to see what we find.

Anyway, not sure how many of these are heat or injector related or how many are seat failures, but the fact that at least half are stock and fairly low miles for a Cummins makes me a bit nervous about the longevity of the common rails.
 
So with what you are saying about matching air to fuel triton. Is there a good rule of thumb to go by as in lbs per min on the turbo and ml per min on injectors? I know there are a ton of other factors that will ultimately affect air flow but with the multitude of set ups everyone runs, Dyno #'s and all the race teams conducting R&D for their setups Some one has bound to have seen a trend of air flow versus fuel flow #'s that produce reliable HP.

By the way where at in the NC mountains do you call home?
 
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