I thought with all the knowledge we have here we should discuss this. I heard on DP a comment about using larger injectors and less injection duration to help with the cracked piston issues. Are there any benefits to this? Could this help relieve the stress on our rods. I know they are not needed to reach high HP#'s but could they help our engines last longer?
Duramax Larger Injector Discussion
- Thread starter Blackbird1877
- Start date
The biggest advantage to big injectors for most trucks is to those who sell injectors.
At first, we though the cracked pistons were caused in part by big sticks. Why? Most the pistons that busted had big sticks in the engine.
With cylinder pressure testing coming up soon, perhaps some of these riddles can be answered.
For right now, keeping EGT's and torque down seem to be the answer today.
At first, we though the cracked pistons were caused in part by big sticks. Why? Most the pistons that busted had big sticks in the engine.
With cylinder pressure testing coming up soon, perhaps some of these riddles can be answered.
For right now, keeping EGT's and torque down seem to be the answer today.
Ever wonder why injectors are getting smaller, not bigger?
Small injectors with very high pressure can act like big injectors OR small injectors, depending on the rail pressure. Lots of pressure = Big Injector. Little Pressure = Small Injector.
12v, 24v, and CR 5.9's have cracked pistons, and they use HUGE injectors, every one of them. It boggles the mind how big these sticks are, some are 10 times the area of Dmax injectors.
Small injectors with very high pressure can act like big injectors OR small injectors, depending on the rail pressure. Lots of pressure = Big Injector. Little Pressure = Small Injector.
12v, 24v, and CR 5.9's have cracked pistons, and they use HUGE injectors, every one of them. It boggles the mind how big these sticks are, some are 10 times the area of Dmax injectors.
I am not saying I'm right on this, what I'm saying is I need some proof that big sticks do something good. Big stick trucks have cracked pistons too, but that doesn't mean it was their fault.
I'm not even convinced that advanced timing is what cracks pistons, which is now generally accepted "knowledge". I run as much if not more timing than anyone, yet haven't cracked pistons yet. Bent rods, melted pistons, lifted head, but no cracked slugs yet.
I'm not even convinced that advanced timing is what cracks pistons, which is now generally accepted "knowledge". I run as much if not more timing than anyone, yet haven't cracked pistons yet. Bent rods, melted pistons, lifted head, but no cracked slugs yet.
I heard sometime back that the reason that LBZ pistons crack is due to the wrist pins being pressed in and the tolerances are to close. Truth or myth?
From what I've seen, that would be correct. Some pistons are overstressed from the factory during the press-fit operation for inserting the brass wrist-pin bushings.
Seems you either crack your LBZ pistons in 12,000mi, or they last forever.
But LLY and LB7's have cracked pistons also. Often at high mileage instead of low mileage. The common symptom seems to be high EGT's.
Seems you either crack your LBZ pistons in 12,000mi, or they last forever.
But LLY and LB7's have cracked pistons also. Often at high mileage instead of low mileage. The common symptom seems to be high EGT's.
I did NOT know this
Off the top of my head, one street Cummins injector is 6 hole x .016 DIA per hole. This is .0012 sq in. An LLY is 7 x .0059", or .00019 sq in, about 6 times the flow. But the LLY injector will make as much power, 100rwhp per injector same as the Dodge. 6 x .016" aren't the "big" Dodge injectors, they are about 200HP IIRC.
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PS - I'm no Dodge expurt, this is just based on my feeble memory of reading Dodge boards (since I'm banned from most!)
If we can keep are rail pressure up We will be doing better to help the pistions rather then going with bigger sticks. Drive pressure and High Egts IMHO is the biggest cause of bent rods.
The cyl psi testing will be a blessing! I need twin CP3's as is. I need a lot more than that too(rods, pistions, etc.). I'm running 50% ExtrudeHone'ed tips now. I do need more rail psi but I think the dual feed line helps me a little. Runnin the 20/20 tune i calculated 19MPG the last tank! (with a heavy foot too!) I do get some combustion rattle though especially if i step on it and let off and give it some throttle it rattles for a second. and currrantly boost is 32psi and 45ish drive PSI
i melted my pistons, not cracked, but my EGTs were extremely high.... i would hit 1800* on the street and i never looked at it when i pulled.
12 valve injector i use is 5x24 i notice since i went with bigger injector in my duramax the truck egt are not high what so ever. but i ran out of fuel so im going bigger now.