Cranks

[Mikey]

The harmonics in LS and LQ engines are not the harmonics in a duramax

Ok Thanks
Trust me. I am not here to measure my Johnson against anyone like many do. I am only here to gather good info.
Given that, wasn't the revised cam for the Gas engines designed because of bad harmonics. The firing order is similar to duramax engines.

 

[PACougar]

Ok Thanks
Trust me. I am not here to measure my Johnson against anyone like many do. I am only here to gather good info.
Given that, wasn't the revised cam for the Gas engines designed because of bad harmonics. The firing order is similar to duramax engines.

I don't think you can compare two different engines because they have something similar between them. There are so many small differences and everyone plays a part. It's like the duramax hit the proverbial lottery for breaking cranks.

 

[duratothemax]

If you look at the main cap design, the duramax is similar to the old sbc and the newer LS and LQ motors have better cap design..

Have you ever looked at a Duramax block? Im guessing not, because the duramax main cap design is nothing like a Gen I small block chevy.

 

[Fahlin Racing]

The cam changes with the rearrangement of the distribution of the harmonics by operation are the only things in real direct relation from one compared to the other, design is different however thought is the same. With the firing pressures between the two the amount of stress concentrations are different regardless in frequency or part design flaws.

 

[Mikey]

Have you ever looked at a Duramax block? Im guessing not, because the duramax main cap design is nothing like a Gen I small block chevy.

I meant in terms of design advancement. LS and LQ motors have a much advanced cap design compared to the sbc design. Relative to that, the duramax is in its first generation of cap design, and quite frankly it is a poor design for high horsepower.

 

[adeso]

to give you guys who haven't seen it an idea of what we are talking about, here is a vid of taking a steel plate though its natural freqs. now they are racing though each band, but notice when they are changing freqs the plate just sits there and doesn't react until they dial in the freq. Hitting a natural freq even if it doesn't destroy it it puts a lot of stress on it.

https://www.youtube.com/watch?v=1yaqUI4b974


Here is one of a Chinook that hit on of the systems natural frequencies. There isn't someone in there messing with the controls to do this, everything is locked in position they just brought it up to a ground resonance and it got away from them.


https://www.youtube.com/watch?v=-LFLV47VAbI


Ok one more, slow motion of what is going on. Now remember this is just a tiny vibrator (yes it is called a vibrator) that is exciting the steel. I wish I could find a video of taking a structure up and down freq ranges. It does nothing between its natural frequencies, just sits there and shakes. Until you hit a natural freq then you can rip apart anything. And each part has different natural freqs, and they all interact with each other.

https://www.youtube.com/watch?v=uBZqa851uvw


Ok Ill stop now. Hope this makes some of the new guys understand what is being talked about here. And remember, what is going on in the engine is much more complex than a single bar experiment

 

[McRat]

So, we still can't shake the material flaw train of thought.....

I will put forth that if it was a process or material issue, the failures locations would be more diverse.

Since it is rotary forged (sequential throw), is it possible the front forge operation yields a different grain structure as the other throws?

 

[duratothemax]

I meant in terms of design advancement. LS and LQ motors have a much advanced cap design compared to the sbc design. Relative to that, the duramax is in its first generation of cap design, and quite frankly it is a poor design for high horsepower.

Im still not sure what you are talking about.

The Gen III/IV/V LS engines and the duramax both have the same style deep skirt block with cross-bolted main caps.

So if you think the duramax is a "poor design", then you think the LS is a "poor design" too because they are both basically the same. Only difference is the LS engines have 4 bolts that go straight in and 2 cross bolts per cap, versus 2 bolts that go straight in and 2 cross bolts per cap on the duramax.

 

[Fingers]

And those extra two bolts are a big deal when it comes to distributing the clamping force.

However, for truly advanced main cap design, you have to look at those with combined caps and girdle like this.

Thought a lot about making one for the Duramax.

 

[prodiesel804]

looks like a 6.0 powerstroke

 

[MarkBroviak]

That right there is my favorite part of the 6.0L Powerstroke engine, wish the DMax was like that!

 

[MAXX IT OUT]

I don't think this was gone over, but could there be anything with the different in the blocks, 01-05 and 06-current engine blocks that may have an impact on harmonics problem.
x+y+z+the firing order=a broken crank?

 

[S Phinney]

They are still the same design and all generations are seeing broken cranks.

Sent from my XT1080 using Tapatalk 2

 

[Mikey]

..

 

[MAXX IT OUT]

I heard that the main journal webbing is different....

 

[JoshH]

I'm working on a truck right now that has a crank that broke at the front of the 7-8 rod journal.

 

[JoshH]

A few pictures.

 

[Fingers]

It still intrigues me how the initiation point is rotated from the axis center. Even when they break on that throw of the crank.

 

[fishsmith]

That truck had an edge with dpf delete on it. Otherwise stock. Never abused.

 

[Mikey]

Is it possible that the rear 2 cylinders have reversion issues, heat buildup, and hydraulic activity due to poor exhaust design?