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

bdp

bdp

beans diesel performance
Joined
Apr 23, 2006
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1,730
Ok so everyone with cr's are melting pistons so lets have a discussion on this.

Post up if you have melted some and if you have what series engine, mods and what programmers/boxes were you running.

I have melted 2 sets of 600 series and 1 set of 555's in my truck. All have been done with a Smarty/TST combo first two sets were with no timming on the Smarty and last set was all out with full timming on everything and was the worst so far.

My therory, It starts with timming. Get rid of the pre-injection and I think things suddenly get better. CR's are about the only engine on the market that we can not self tune. We rely on off the shelf programmers and stacking boxes to make power and while that works well its the same tune for everyone. Every truck build is going to be different and need specific tuning for that combo to be able to get maximum power and saftey for the engine unless its stock.

Next is pressure, every other injection system runs WAAAYYY hotter egts then the cr's yet how may pistons do you see melted in 12v's and vp's? Or even in a Powerstroke? Those injection systems run alot less injection pressure thus you see more smoke and higher egts because much of the fuel is burning in the manifolds. IMO it is not the egts in the manifold that is melting these things its the actual temps on top of the pistons. They have such a fine mist of fuel then can burn more completly and much hotter in the cylinder then the lower pressure systems. So while you may only see 1400 degrees on your pyro the piston is getting melted down by a cutting torch called an injector nozzle while all of the fuel is still getting burned in the cylinder and not heating up the pyro probe.

How do we keep this from happening? I am not tottaly sure. IMO a start would be a whole new engine management system that we can have better precise control over. In doing so we can eliminate the multiple injection events and get more precise with injection event timming.


Lets hear some other opinions on the subject....
 
06 dodge melted number 4.. running smarty/mp8 stack injector failure is what caused mine we think...lol havent investigated it all yet just happend maybe less than a week ago..
 
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.
 
Smokem said:
Did you keep the 124° injector when you went back to the smaller bowl piston?
Click to expand...

I remember seeing a photo of the doctor'd pistons and they were modeled towards the non re-entry style bowl like the 04.5's, so I would imagine he would have been stuck with the 124 degree injectors.....I see the Flux injectors I have are tighter yet.


For chits and giggles I'm going to try a set of 03-04 tips with my steel pistons, the bowl is kinda a hybrid, and I'm running the 124's right now, but the bowl design should work as re-entry as well, they have the small radius at the outer side of the bowl, to curve the spray down and back in.

I remember reading a while back that cummins spent a bazillion processor hours modeling the 6.7 pistons......only to come out with almost the same piston as the 03-04's.... multiple injection events to boot....If I didn't have these steel pistons I'd be leaning that way (03-04)'s, and matching nozzles.
 
I dont quite get it either. My 600 series got ran multiple times last yearand I didnt have a problem. My egts wernt insane and the smokewas pretty clear @ WOT
dodgemotorpics007.jpg

dodgemotorpics004.jpg

dodgemotorpics003.jpg
 
Is there a metallurgical difference between pistons?

Has anybody melted pistons while blowing massive quantities of blacks smoke?
 
Excess quantities of fuel can increase EGT's due to afterburning, where it continues to burn after the cylinder. But it can decrease the amount of heat in the combustion chamber by absorbing heat similar to how water injection works.

I hypothesize that CR's are now burning fuel so quickly, so efficiently, with such a wide pattern, that gasser logic applies. More fuel should help keep them cool.
 
With the injection pressure and how well the fuel is atomized, is it possable that the egt's are staying low but the cylinder temps are through the roof because all the fuel is burnt in the cylinder and there is no fuel left to burn in the manifold. Why would the cr be burning pistons with lower egts and the p pump and vp trucks blow so much more smoke and see higher egts and they don't? I think it is because the egt# on the p pump and vp trucks is even or higher than the cylinder temps because of all the raw fuel still burning in the manifold. Just my 2 cents.

Joe
 
bdp said:
Ok so everyone with cr's are melting pistons so lets have a discussion on this.

Post up if you have melted some and if you have what series engine, mods and what programmers/boxes were you running.

I have melted 2 sets of 600 series and 1 set of 555's in my truck. All have been done with a Smarty/TST combo first two sets were with no timming on the Smarty and last set was all out with full timming on everything and was the worst so far.

My therory, It starts with timming. Get rid of the pre-injection and I think things suddenly get better. CR's are about the only engine on the market that we can not self tune. We rely on off the shelf programmers and stacking boxes to make power and while that works well its the same tune for everyone. Every truck build is going to be different and need specific tuning for that combo to be able to get maximum power and saftey for the engine unless its stock.

Next is pressure, every other injection system runs WAAAYYY hotter egts then the cr's yet how may pistons do you see melted in 12v's and vp's? Or even in a Powerstroke? Those injection systems run alot less injection pressure thus you see more smoke and higher egts because much of the fuel is burning in the manifolds. IMO it is not the egts in the manifold that is melting these things its the actual temps on top of the pistons. They have such a fine mist of fuel then can burn more completly and much hotter in the cylinder then the lower pressure systems. So while you may only see 1400 degrees on your pyro the piston is getting melted down by a cutting torch called an injector nozzle while all of the fuel is still getting burned in the cylinder and not heating up the pyro probe.

How do we keep this from happening? I am not tottaly sure. IMO a start would be a whole new engine management system that we can have better precise control over. In doing so we can eliminate the multiple injection events and get more precise with injection event timming.


Lets hear some other opinions on the subject....
Click to expand...


Bean, what type of timing are you adding with the TST?
 
Melted #4 back when I ran a single...You've prob. seen the pic so I won't repost..

Ran BD Crazy Larry early on but switched to the Smarty TNT....I think the damage was already done though...MP8's been on all the time....100% with racing and playing a bit....

I'm pretty sure mine was due to a cracked / Bad injector....Noise was getting louder and then the truck wouldn't start...Warrantied injector body and it seems to run fine with the exception of a little sputtering / white smoke at cold start up......Still made 584 with melted piston...

As for my new build and with the cut piston (.100 off top), So far so good...Although with me it being TOTALLY clean at WOT, I'd say I'm lean I guess....Chasing a power loss / sputtering issue now though....Bore scope showed that my pistons seem to be in tact......

Go Figure!!!

I do have the Very bad Rattle that we've all debated before...I'm sure with my cut pistons that I getting ignition against the cylinder wall a bit from the pilot inj. event.......Who knows what thats really doing or if its a source of any problems yet....
 
BTW bdp, I agree with you logic completely with regards to these CR's!!!!

Have no clue how to fix it though...That's gonna be above my head!!!
 
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
 
i think we need to list what years of cr's and what tuner's your running. just have noticed a lot of smarty tuned trucks that have torched pistons....i have also noticed the crazy hp tunes arent available for my 07...

so lets list and try and isolate!
 
When you think about the CR injector, and pressure, in theory it **might** be possible for pressure spikes....even pressure alone to overcome the ball seat, and mabey not fire the injector, but maybe even some leakage, and in that case bring on timing in that cylinder.

Should include the use of a pressure box on kill in the list of melt downs.
 
I have run my CR race motor in my 1990 truck for three seasons and for some reason I have never had a pistion issue. This truck is not a street truck and sees only track and dyno time. The motor is a 03 250 hp and for the first season had the plastic spray jets. I installed the blockers and added the "j" jet this year. I have always had the rail and the timing jacked up. Spray water only with shots for NOS. I run a fairly small turbo set up compaired to most. Only see 80 psi of boost- 100 drive psi. I have never run a TST on it I will be next weeked to see what difference it makes. I also run a rail cap so who knows how high the pressure really is. Never had a injector issue to date. I have bent connecting rods, push rods, lossened valve seats, cracked cylinder bores and ate transmissions like crazy (till now). EGTS (all six) never read below 1600*f on a pass. Intake air temp is always 120-130*f. I think Marco said it best. HEAT/TIME to cool. Too much duration may cause the crown to be heated all the way down to BDC after the power stroke. Air to fuel ratio and cooling time play a big part. The newer trucks have that post injection event I think that is what is killing most 4.5+ engines.


I think a poll of failures with what engine and mods and what where you doing when it melted would be a great idea.

Just my thoughts.

Malcolm
 
I think you all are onto something here, less timing advance does result in less combustion in the cylinders and more in the exhaust system. I have always felt more comfortable with egt's in the 1500-1600 range for short periods with less timing, crank the timing up though and I limit it to less. This still doesn't explain why J.P. melted down though, timing 4 is not advanced relatively speaking but taking into account the rpms like Marco said does make sense. I think you can't inject enough water, to the point of quench. I wished I had more and I am using 2 625 nozzles and 220 pump. On any of my next builds I will have a water injection port for each cylinder.
 
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