LLY: cracking injector bodies

[juddski88]

Maybe your rail pressure sensor is sticking and it is going higher than the 26K without it knowing it. Also the rail pressure sensor is scaled to read up to 200MPA? Stock only goes to 180 and it will spike above 26K if you command more than 180 without rescaling the rail ressure sensor. Not trying to offend, just know that sometimes the simplest detail can be overlooked and cause a serious issue.

I have read this before and i have since forgotten the details i guess. I will take a look. We had an issue on Dylan's truck a few weeks ago where we think his regulator stuck because of commanding 180mpa and his truck hiccupped half track and then defueled to 20k on the rail and threw a high rail pressure code. Mine could very well be spiking well over 26k, which is my fear, because I know the injectors can't take it.

Edit:

here is the table, it is scaled to 180. I have one LBZ cp3 and one II 220% pump.

 

[duratothemax]

I really still think it was a fluke...considering how many trucks with twined pumps and running 26k on LLY/LB7 injectors without problems. Particularly schulte's truck, which has even bigger injectors than yours (modded regulators, and holds 26-27k during WOT runs). I know Dustin apparently had problems....but thats just one other truck.

The history on those injectors is unknown, and with how hard the truck has been run before...if it was a pressure thing, I think they would have cracked a long time ago. Especially considering how similar they are to LBZ injectors.

Its probably going to be impossible to fully pinpoint the cause, considering your engine/injector/FICM/tuning mashup.

 

[sweetdiesel]

last i knew guys "billet" hold downs were off the market because a flaw found in the material? (was what i heard) and he was in the process of redesigning them with a better material.. Weather this is true or not i haven't heard. He does have the ARP stud kit though as he is where i got mine from..

That was a bad batch from Arp that's from what I heard been resolved ?

How cold is it?? With no glow plugs I have no problems starting without ether.

Me niether??

that's what everyone tells me, but without my glows ive never been able to start this truck with either motor, and this one has higher compression! cranking injection quantity is still stock, maybe that needs a tweek? i dont know. it can be 100 degrees it wont start. needs to be 110 degrees ECT before the truck runs clean

You have something wrong tim??? I hate to say it but I run 15.7 comp and it starts first crank at cooler temps. You need to investigate

 

[sweetdiesel]

Fwiw I've seen higher press than that on a lb7 and never cracked a inj? Maybe just lucky but I don't have luck

 

[juddski88]

That was a bad batch from Arp that's from what I heard been resolved ?


Me niether??




You have something wrong tim??? I hate to say it but I run 15.7 comp and it starts first crank at cooler temps. You need to investigate

The only place to look is the tune at this point. The pw has to be spot on perfect to get this truck to start and idle at all. There's a very very small margin of what works and hat doesn't. The ECT modifier has been changed, because the truck runs pretty cold and in order to get it to stop skipping and belching when cold we figured out that table was injecting so soon when cold it was cooling the cylinders off even more and not even burning the fuel. And again, the margin Is very very small.

 

[S Phinney]

You are running Davids camshaft right? With the specs on that can it could be the overlap bleeding off cylinder pressure causing a lower than optimal condition. Just throwing that out there to think about. Have you done a compression test to see what cranking pressures are? I'm with Ben on this about the injector cracking. Its probably a fluke. It happens.

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[juddski88]

Truck did the same thing with the socal cam. with the socal cam it pumped 300psi cold. Mahle forged pistons 41.5cc bowls, c gaskets, .005" protrusion. This cam actually comes in earlier and holds much longer...im running .012" protrusion now and c gaskets

 

[TROJAN366]

Truck sounds so mean. When you were warming it up next to the dyno I instantly realized I needed some headers, or at least manifolds

 

[DAVe3283]

Edit:

here is the table, it is scaled to 180. I have one LBZ cp3 and one II 220% pump.

See how the table goes flat on the right edge? You want to continue the line linearly out to the end of the table. That allows the ECU to "see" slightly higher rail pressure, and indicates if you are actually overshooting 180 MPa, where as before you wouldn't know.

If you don't know how to do a linear interpolation, post up the values from the table, and I (or someone else here) can fill in the last few cells for you.

 

[juddski88]

See how the table goes flat on the right edge? You want to continue the line linearly out to the end of the table. That allows the ECU to "see" slightly higher rail pressure, and indicates if you are actually overshooting 180 MPa, where as before you wouldn't know.

If you don't know how to do a linear interpolation, post up the values from the table, and I (or someone else here) can fill in the last few cells for you.

Hmmm, interpolation....that's a tough one. Haha. Thanks Dave, I rescaled it.

 

[S Phinney]

Truck did the same thing with the socal cam. with the socal cam it pumped 300psi cold. Mahle forged pistons 41.5cc bowls, c gaskets, .005" protrusion. This cam actually comes in earlier and holds much longer...im running .012" protrusion now and c gaskets

With my first build which had cut and coated LB7 pistons that came out to be 15.98:1 comp with all data considered. My truck would not start in weather colder than 40 area without plugging in the block heater and it would read 340 psi on compression test. Since I changed my pistons and went with a 17.4:1 compression, there isn't any problems with start up in any conditions and it runs clean from the initial start. Before it was terrible starting and didn't run clean until there was substantial heat into the motor. It could idle for a while and still smoked but if you drove it it would clean up after a few hundred yards of driving. The startup problem probably is compression related, since static compression is only an indicator of where you actually are on cylinder pressures overall.

 

[juddski88]

shes definitely making some pressure now, but get this:
I only saw 42psi boost in denver with a .092 jet and 23-2400 microseconds and would bury the pyro past 2000 degrees at the end of a run
I made 53psi fuel only the other night, 58 psi drive pressure, and 1800 degrees on the pyro, same PW and just smoothed timing tables. main changes were: cam, heads, more protrusion, looser piston to wall clearance, tighter valve to piston clearance

 

[S Phinney]

You probably brought some timing up in some areas when you smoothed the tables. Better airflow with your combo didn't hurt either. Its crucial to make those tweaks to get it running tops.

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[McRat]

Cracked Injectors:

Rare. They happen though. I had one crack. I use 3 shims on race engines then bottle test. I program max fuel pressure. I wouldn't change anything unless you crack one again. Kinda like a transfer case exploding, rare, but it happens.

 

[juddski88]

If its so rare why are some pullers replacing bodies every 4-5 pulls even with reliefs in place? Just because it's not mentioned here doesnt mean it's not happening

 

[juddski88]

Fact: more people than just Dustin have found that running less than 175mpa greatly increases injector life. Those who have the money to play still keep their pressures up amd make retarded power and win pulls by 30 ft

 

[McRat]

Dunno, I've run a few thousand passes, over 200,000 miles, over 100,000 towing, on 3 trucks programmed to "kill" on pressure.

Guess it happens, I'm just not seeing it a lot like turbo boots, speedos, wheelbearings, pistons, rods, etc.

If my setups were popping injectors on a routine basis, I'd be doing something. But one failure in 7 years for us is not enough to generate a MTBF.

NOTE: LBZ+ injectors have thicker bodies.

Also, be aware that by now, hundreds of people are running KILL fuel pressure. All the tunes I sent out were maxed, and I didn't get much feedback about cracking.

When the LB7's came out, everyone blame pressure boxes on the high failure of LB7 injectors. Later on, they found it was the injector itself that was the issue, at any pressure.

 

[duratothemax]

not to start an argument tim but....how can you definitively blame this 100% on "just because running too high pressure" when your whole fuel injection setup is a complete through-and-through wild card.

You're feeding the injectors double the voltage (LB7 FICM driving LLY injectors).

You're running a completely unique/wild/abstract tune (because thats what it needs to even idle, let alone make big power, as we've found over the past year or so of playing with tuning on it)

You're running an LB7 ECM. LB7 and LLY ECM's definitely run pilot injection differently, and LLY ECM's control the ramp-in and ramp-out of pilot injection more precisely. LB7 ECM's also generally process things a little slower, so fuel pressure control PID/feedback loop is going to be slower.

You've got a completely custom wiring harness, and IIRC the injector-control wires are the same size as all the other wires, whereas the factory uses much thicker gauge wire from the FICM to injectors. (maybe the longer wires changes capacitance to the point where it screws with things? I dont know)

But basically......in my opinion you really cant definitively write this off as "such-and-such problem caused this" considering your truck and how its built/configured/wired/tuned. I know it feels comforting to "have a definitive answer and smoking gun" to problems like this........but in this case, there really is neither......

 

[Rhall]

shes definitely making some pressure now, but get this:
I only saw 42psi boost in denver with a .092 jet and 23-2400 microseconds and would bury the pyro past 2000 degrees at the end of a run
I made 53psi fuel only the other night, 58 psi drive pressure, and 1800 degrees on the pyro, same PW and just smoothed timing tables. main changes were: cam, heads, more protrusion, looser piston to wall clearance, tighter valve to piston clearance

It was Denver man, bad air. Better cam and heads should make less boost of they are more efficient while making more power.

 

[Rhall]

Also the people I know that have had injector body issues are pretty extreme, 3 stroker cp3s goin wide open to nothing will cause extreme spikes. I haven't had a problem with 2 stroker pumps, and high pressure but my junk is lb7