injectors = broken crank ?

[JOHNBOY]

My take

Could injectors cause a crank to break?
A bad set over time sure could IMHO. Am I saying these where bad? No I am not.

Without a complete tear down, and exam by a skilled expert it will be hard to tell. Lots of things can bust a crank. Bearing failure, Balancer coming loose, hydrolock, and so on. It could also be a mixture of things.

If I had to take a wild guess I would look at the crank thrust bearing and see what they look like and how thick they are compared to what they where when the went in. To much crank end play is very bad.

 

[Stingpuller]

Injectors

Not that what I think means anything but I would lean towards harmonics more than anything! I just can't see injector's breaking a crank! I would believe a hydrolock issue but not from different cyl. pressure from injectors. P.S. sorry to hear this Jay. Jeff

 

[LBZ]

....last topic prolly wrong place and may tick a few peoplke off,but on a properly balanced engine set up an aftermarket dampner isnt needed...

I disagree-to a point. At lower rpm's I think your right, but some people that have been shooting for higher rpm's have failed the stock dampners so I think at that point an aftermarket is in order.

 

[duratothemax]

What would that have to do with the broken crank?

I can't figure out why people say this, so I'll give my scenerio and you can give me yours.

Let's say one cylinder was off as much as 30lbs more of cylinder pressure. Would that mean that section where the rod meets the crank is not strong enough for that much cylinder pressure? There is no opposing force that it needs not to overcome to be sure it stays together....after all it is a V shaped motor? If one cylinder is down on pressure, does that mean it would break there because the rest is being thrashed harder in opposing direction....or should it in theory be stronger because it is seeing less abuse?

I could see pistons being issues with a FAULTY injector, but I can't seem to see this theory how a set of not "matched injector bodies" would cause a crank to break. I'm not saying it's not a good investment, I just can't see what it is that people seem to think if an injector flowed even 2% more that it would cause this??? Recently having the heads off and seeing perfect patterns on the pistons as well as great balance rates leads me to believe he doesn't have any injector issues at all.......course he could start the truck and one could fail.....but so could yours and then maybe I could possibly see it taking it's toll on the crank....BUT we have all seen that the pistons, no matter where the came from or the model...are WITHOUT A DOUBT weaker than the crank.

Not to mention it states 60% Extrudehone injectors right in his sig........

Please respond because I would really like to hear YOUR view....OPPOSING what I said above.....maybe I am missing something?

George...I completely agree. I still fail to see how injectors can break a crankshaft.

There are so many other variables that can affect how each cylinder makes power differently. Location in the block (each cylinder is going to run at a slightly different temp), how much air (the duramax heads and intake system flow fairly nicely compared to say a cummins, but you cant tell me the design allows for equal and even air distribution and flow to each cylinder) each cylinder gets, and a million other things.

And also...the engine has a firing order...its not like you have multiple cylinders firing at the exact same time...I think thats what everyone is subconciously thinking/assuming; they are forgetting the basic fundamental that the design of the engine does not allow two cylinders to "fight" eachother.

Example, Dustin (othrgrl) had really crappy injectors if I remember correctly? His pistons were toasted...was his crank broken? no. I think broken cranks are more a fluke than anything.

And Matt (sikdmax), for someone who cant even route fuel lines correctly on a motor, I cant see why you are going around telling everyone that stuff about injectors and their correlation with broken cranks when you dont even know how an injector works or flows...no offence...but you are one of the main people trying to sell others on the "bad injectors = broken cranks" theory....so im confused.

JMO.

ben

 

[duratothemax]

also something to think about...why is everyone so sure that having injectors properly matched at high rpm is more critical than having them properly matched at idle? GM seems to think its most important to have them balanced at idle....they know that no injector is going to flow exactly the same as the other...thats the point of the ECM calculating balance rates and compensating slightly to produce a smooth running engine. But why does the ECM only worry about this at idle/low rpms...?

 

[SIKDMAX]

And Matt (sikdmax), for someone who cant even route fuel lines correctly on a motor, I cant see why you are going around telling everyone that stuff about injectors and their correlation with broken cranks when you dont even know how an injector works or flows...no offence...but you are one of the main people trying to sell others on the "bad injectors = broken cranks" theory....so im confused.

JMO.

ben

Ben.... are you talking about the injector return line thats draped across the top of the motor? Lol.... way to sneak a jab in there though... nice try!


Carry on..... interesting discussion.

 

[dmaxvaz]

also something to think about...why is everyone so sure that having injectors properly matched at high rpm is more critical than having them properly matched at idle? GM seems to think its most important to have them balanced at idle....they know that no injector is going to flow exactly the same as the other...thats the point of the ECM calculating balance rates and compensating slightly to produce a smooth running engine. But why does the ECM only worry about this at idle/low rpms...?

YOU HAVE A VALID POINT BEN, ALSO WHERE THE HELL HAVE YOU BEEN? I WAS GOING TO CONTACT THE AUTHORITIES TO HAVE YOUR PICTURE POSTED ON THE SIDE OF MILK CARTONS AND POST IT ON MISSING PEOPLE SITES:rofl: ANYWAYS, GOOD TO HAVE YOU BACK

 

[McRat]

George...I completely agree. I still fail to see how injectors can break a crankshaft.

There are so many other variables that can affect how each cylinder makes power differently. Location in the block (each cylinder is going to run at a slightly different temp), how much air (the duramax heads and intake system flow fairly nicely compared to say a cummins, but you cant tell me the design allows for equal and even air distribution and flow to each cylinder) each cylinder gets, and a million other things.

And also...the engine has a firing order...its not like you have multiple cylinders firing at the exact same time...I think thats what everyone is subconciously thinking/assuming; they are forgetting the basic fundamental that the design of the engine does not allow two cylinders to "fight" eachother.

Example, Dustin (othrgrl) had really crappy injectors if I remember correctly? His pistons were toasted...was his crank broken? no. I think broken cranks are more a fluke than anything.

And Matt (sikdmax), for someone who cant even route fuel lines correctly on a motor, I cant see why you are going around telling everyone that stuff about injectors and their correlation with broken cranks when you dont even know how an injector works or flows...no offence...but you are one of the main people trying to sell others on the "bad injectors = broken cranks" theory....so im confused.

JMO.

ben

Please do not throw slams in a tech thread, thanks.

I personally have no idea why Dmax cranks bust. Not enough people magnaflux them beforehand to determine if there are hidden cracks.

On injector balance, the way the ECM figures out balance is by the variation in crankshaft acceleration. At first, only GM could get this right.

It's simple math. At high rpm, it's way harder to tell variations in crankshaft acceleration. Not sure if the ECM can do it, dunno.

Could big differences in crankshaft acceleration between cylinders cause part failures due to metal fatigue? Sure. I just have no idea how much it would take.

 

[RENODMAX]

Ok so I may be totally off the mark here but..
With the higher HP engines running stock pistons is there anyway that so much heat (boost) could get them to expand before cracking? Or do I need to set the crack pipe down or the morning

 

[BlkMax]

Are the cranks breaking in the same spot, or does it vary with each failure?

If the cranks are breaking at the same journal, it could possibly shed some light on what may be causing the failures.

 

[BIG DIPPER]

A few things I would like to see:

1. Matt post as he was the one "referencing" the injectors being at fault for the crank.
2. A flow sheet showing how well a stock set of injectors are balanced.
3. A "matched complete in jector" flow sheet after it has 10k miles on it.

There are some certanties in some of the things that have been posted here. While some get scared and intimidated on the net and others choose to argue...I find myself wondering why I got in this to begin with. When people who are uninformed and inexperienced start making inuenods, others get screwed. The simple fact here is that crank has been through some SERIOUS abuse. Since Jay has twins, it is able to make the bottom end torque that others don't and still have the top end that the masses do while getting it all down the track in a 7k truck.

I never liked getting into injector discussion because it always seem to lead to some sort of friendship ending argument in the Dmax community. I stand by everything I have posted and learned over the past years, but it sure is funny how the people who were always against them saying they didn't need them or they saw no gain are jumping ship. I try to keep an open mind when it comes to new ideas and experiences and let the proof be in the pudding. Ask anyone who calls me to hash out a new idea and they will tell you that I argue it with them just to get all the angles....the crank broke and the injectors are fine, a bit small, but fine....it is what it is.

I don't think the ECM is compensating in the RPM range either, I feel it is at idle for "driver comfort". Remember diesels had a pretty bad rap a few years ago and the big 3 have been trying to get rid of all the drawbacks to make them more user friendly. I was just throwing out possibilities that we really don't have the answers to.

Pat, as far as the metal fatigue, it's racing. The idea is to make HP and as much as you can.....metal fatigue is going to be there no matter any other circumstances. Having a complete set of injectors will not change that....which is the reason this discussion started. I am open to discussion or proof showing otherwise.... The harmonics thing could be beat until we are all dead....everything going on in the truck will affect it...all the way to the bumps in the track. How would that compare to BB Chevy plated to a dragster? Could you really tell me that gas flowing through a carburetor evenly distributes to all the cylinders and that crank acceleration is linear and smoother?

 

[zfuller123]

I know George will argue to understand one's reasoning.... back when we were discussing my motor build, he had lots of things to say that caused me to rethink, for a while, what i was doing with my setup. Particularly with the air and turbo setup.

However, i've also found that he always has an explanation ready for his point of view or particular belief - so I don't feel he throws out these questions and points without some valid reason.

A for an injector taking down a crank - that's a hard one and i believe as many others do, that more data is needed. Right now we only know what was IN his truck (config) - and that the crank is broken. For someone to have already alluded to an injector failure causing it seems to be a pretty hefty claim right out of the box IMO.

I will be the first to admit i'm 90% ignorant on these Duramaxes. I do feel my knowledge has grown quite a bit from my personal breakages and experiences over the past 10 months though. I would think that this failure is going to be, in the end, guesswork - or, 'it is what it is'.

There are always the outside chances of something else (other than raw abuse) being the culprit - I mean how many of us have had such a weird problem with our trucks that nobody's ever heard of it? It happens randomly and can't track it down or log it? Rough idle's but perfect balance rates, etc. etc.??

I would just hate for a topic such as this to make people turn away from each other or have an all out fued, even though it's definitely something worthy of a heated discussion. Can't we all just get along? :hug:

 

[malibu795]

what condtions are the mains in?

 

[McRat]

A few things I would like to see:

1. Matt post as he was the one "referencing" the injectors being at fault for the crank.
2. A flow sheet showing how well a stock set of injectors are balanced.
3. A "matched complete in jector" flow sheet after it has 10k miles on it.

There are some certanties in some of the things that have been posted here. While some get scared and intimidated on the net and others choose to argue...I find myself wondering why I got in this to begin with. When people who are uninformed and inexperienced start making inuenods, others get screwed. The simple fact here is that crank has been through some SERIOUS abuse. Since Jay has twins, it is able to make the bottom end torque that others don't and still have the top end that the masses do while getting it all down the track in a 7k truck.

I never liked getting into injector discussion because it always seem to lead to some sort of friendship ending argument in the Dmax community. I stand by everything I have posted and learned over the past years, but it sure is funny how the people who were always against them saying they didn't need them or they saw no gain are jumping ship. I try to keep an open mind when it comes to new ideas and experiences and let the proof be in the pudding. Ask anyone who calls me to hash out a new idea and they will tell you that I argue it with them just to get all the angles....the crank broke and the injectors are fine, a bit small, but fine....it is what it is.

I don't think the ECM is compensating in the RPM range either, I feel it is at idle for "driver comfort". Remember diesels had a pretty bad rap a few years ago and the big 3 have been trying to get rid of all the drawbacks to make them more user friendly. I was just throwing out possibilities that we really don't have the answers to.

Pat, as far as the metal fatigue, it's racing. The idea is to make HP and as much as you can.....metal fatigue is going to be there no matter any other circumstances. Having a complete set of injectors will not change that....which is the reason this discussion started. I am open to discussion or proof showing otherwise.... The harmonics thing could be beat until we are all dead....everything going on in the truck will affect it...all the way to the bumps in the track. How would that compare to BB Chevy plated to a dragster? Could you really tell me that gas flowing through a carburetor evenly distributes to all the cylinders and that crank acceleration is linear and smoother?

Jumping ship? My ass. I'm testing stuff. I have a piston melting issue I need to resolve, so I'm trying different things.

Whether anyone believes it or not, I did make 798rwhp uncorrected on a 4-5 second unloaded pull with stock LLY sticks. There were lots of witnesses and it was dyno that has always been stingy. That was a single turbo, nothing but pump diesel, no 90psi liftpumps.

Let's see you test anything publically before you start slamming those that do.

I've been witness to LOTS of fk'd up Dmaxes running poorly made injectors, dating back 4 years, hence why I was scared to run untested injectors. If I was building a Dmax hotrod, I'd certainly make sure I was getting good sticks.

I did not say massive injector inbalance is the cause of broken cranks, that would be pretty silly considering the first broken crank I saw was in a stone stock truck, and the next couple were stock stick trucks.

Here's my position, you know, the one that causes people to call me a cheerleader, nut-swinger, biased, blah, blah, blah:

Since I started racing late model GM's, I have always tried to publically support shops who I felt could really help us hotrodders. The list is really, really, really, fk'g long. Fasttoys, Superchips, GM Performance Parts Division, AFR, LS1Edit, AutoTap, CCW, Kumho, MT, M&H, Hoosier, etc, etc, etc, before Dmaxes were even made. I determine which shops I contact and support based on testing products that I paid full retail for. And I also tell people when products aren't as advertised or a company that really isn't interested in our hotrods.

Now there are guys who think I did a 180 deg about face the second I bought a Dmax 5 years ago. Bullshit. They are so wrapped up in selling stuff and their own "nutswinging" that it's easier to just to throw darts than do the legwork of testing.

If I had a piston that would not melt at high boost, high DA, I would still be running stock injectors. Or if Bosch didn't want $6000/set for their racing sticks, I'd be running theirs.

As far as you trying to humiliate another member here by starting this thread and explicitly calling him out, I'm not sure how that affects crank failures or injectors, but I do know how that attitude affects tech boards. It fk's them up. Discuss tech, not people. There is a difference.


PS - I've gotten balance sheets, before and after, from both SCD and MDE. If you are honestly interested in what stock sticks flow/balance at high pressure, do a search. Or I'll track them down for you.

 

[BIG DIPPER]

You are clearly one of the reasons why this can't be discussed Pat.

You make everything personal and become a child.

You all can continue on without me. This was another opportunity for as all to learn something, especially if Guy were to participate.....gone to shitter again.

One other thing, I only make comments and contribute on something I an intrigued by. If Matt had nothing to offer other than a sales pitch, he should have stayed out of it.

You really are an ass.

Ps. You're paying retail on parts you test is a lie. I know a lot of the people you deal with and they like me better thn you. You really got me on not being public on anything I've tested.....Mike is the only one doing any trans R&D....I just copy....give me a break.

 

[Leadfoot]

But why does the ECM only worry about this at idle/low rpms...?

Is it due to the processors inability to aquire data, compute, and execute corrections at higher RPM's? I would think that the ECM processor is more than capable of doing that at idle RPM's (where vibrations can often be felt most and because a smooth idle is very desirable), but at some point it is not fast enough to calculate/process at higher RPM's. It made sense to cut it off somewhere so idle it was (also the reason for being able to check up on balance rates). The only thing I fault them for is not illuminating a CEL automatically when balance rates get outside the designated "window" of accepatable values (by itself or when compared to it's 7 brothers). It would be a good early warning of a bad injector.

As for crank issues, I was talking to my engine builder and he had some things to share. He has seen cranks overpowered and broke but it usually starts at one of the "throws". I told him that several DMax's have broken at the snout. He said it was most likely due too much pressure on the snout. He is not very familiar with the DMax motor or crank, but said he has seen more than a few blower motors snap the snout as the blower drive added too much resistance. I don't know what the front of the crank runs/drives. I saw Ben's crank at the house when he had several motors there but my memory isn't that great.

I brought up the fact that many of these builds are turning some serious RPM and that there are some pretty stout lockup converters available. I was thinking that there are 3 forces acting on the crank. 1 is the rods forcing it to rotate, 2 is the converter/clutch/tranny adding resistance (converter locking being pretty rough at high HP and RPM), and 3 the resistance of the balancer and front "drive". The bellhousing end of the crank is pretty stout, but what about the front. Could the fast rise in RPM and quick drop with that heavy of a balancer cause the crank to fatigue. He said maybe, but analysis would have to be done.

His best quess was that the crank is just not up to the task. I tend to believe him as he's pretty good and the fact that we are seeing more broken cranks as power is up.

I spoke to him about injectors and harmonics and he said anything is possible, but if a cylinder or cylinders is causing harmonics (be it injectors, broken, rings, etc), there is usually tell tale signs in the main bearings, pistons, cylinders too. It will be interesting to see what Jay finds when he tears his down.

I have a feeling that at some point past 1000RWH that a better crank will be needed for longevity. At that point it almost seems like the stroker is the way to go unless someone makes a cheaper stock stroke crank that will hold up. The diameter of the snout might be the biggest weak link in the chain, if we can't physically make it bigger.

This is just some ideas and hopefully food for thought.

 

[Leadfoot]

Are the cranks breaking in the same spot, or does it vary with each failure?

If the cranks are breaking at the same journal, it could possibly shed some light on what may be causing the failures.

That would be a huge indicator. I keep hearing they break at the snout but have not seen side by side pictures (or any pictures) that show exactly where it broke and MORE IMPORTANTLY how it broke. How it broke can sometimes provide as much information or more as where it broke.

I would hate to see people leave this thread. We all don't have to agree on hypothesis', but we all do have to find an answer to this if high HP builds are going to continue and survive.

Heck I can be an ass at times (we all have our moments), but without these forums many of us (including the experts) would be left in the dark :hug:

 

[McRat]

You are clearly one of the reasons why this can't be discussed Pat.

You make everything personal and become a child.

You all can continue on without me. This was another opportunity for as all to learn something, especially if Guy were to participate.....gone to shitter again.

One other thing, I only make comments and contribute on something I an intrigued by. If Matt had nothing to offer other than a sales pitch, he should have stayed out of it.

You really are an ass.

You started this thread (your stated reason, twice) to slam somebody who thought injectors contributed to crank failures. I don't know if that is a contributing factor or not, but I do know that only an ass would think that a personal attack against someone is a great way to start a tech thread.

Then you have to bring me into it when they don't reply fast enough? If you can't get someone to fight you, you throw a punch at the guy sitting at the bar minding his own business?

Why is it that everyone thinks I'm a jerk if I reply to their slams? I'm nobody's doormat. I'm not in a good mood obviously, since I just drove 1300 miles to bust my truck racing.

I seldom if ever fire the first shot on the interwebbythingy. The only time I've been "punished" on websites is for firing back after getting blasted first.

You know, I might be an asshole, but at least I admit I'm one.

So please leave me out of your freaking rants aimed at others, and we will get along just fine. I've never done that to you, and I expect you to show me the same consideration that you demand for yourself.

Yours Truly,

The Guy with a Busted Truck and a Short Fuse.

 

[Stingpuller]

Crank's snout

I can't by the crank snout is not up to the task. The Dmax crank is 1.970+/- and a BBC is 1.6+/-. I have seen some pretty stout blowers driven by std. BBC cranks and they do just fine. There is no real drag on the front of are motors! The front has very little drag compared to some race motors. To break a crank at the front I fill it's Balance/Harmonics. If it was from to much power it would go on the #7/#8 rod most likely. That's were all the twist would be. I have nothing in this this is just my thoughts. It just sucks that we are seeing new problem's. Jeff

 

[Leadfoot]

I can't by the crank snout is not up to the task. The Dmax crank is 1.970+/- and a BBC is 1.6+/-. I have seen some pretty stout blowers driven by std. BBC cranks and they do just fine. There is no real drag on the front of are motors! The front has very little drag compared to some race motors. To break a crank at the front I fill it's Balance/Harmonics. If it was from to much power it would go on the #7/#8 rod most likely. That's were all the twist would be. I have nothing in this this is just my thoughts. It just sucks that we are seeing new problem's. Jeff

Like I said I have only seen one if person and did not know the dimensions. My only question is yes it's bigger than a BBC crank (per the dimensions stated) but what material and how much does torque, balancer weight, etc. differ from at BBC to DMax? I'm not doubting, just asking as a naturally aspirated BBC is a much different animal than a turbo diesel. It's not a true apples to apples comparision. Both are essentially big airpumps but they do have differences. Again not trying to dispute, just trying to get answers.

I think there will be alot of speculation and incorrect ASSumptions until more failures are made public (Thanks to guys like Jay) and analysis of those cranks and motors can be done. Until then I think we are going to have alot of differing opinions and probably many UNNECESSARY heated discussions and name calling.

It would be nice to have a locked sticky post with a listing of those who have broken cranks with specs on motor build, conditions of failure, pictures, etc. but knowing how much people are not forthcoming with information (with some exclusions) that most likely will not happen.