Jon did you see what Henry posted about the 2017 Dmax, how its going to be running up to 3000psi cylinder pressure? And they did something different with the crank....
Crank Plots
- Thread starter Fingers
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I could be wrong, but I think they have been rolling the fillets from the start.
220 Bar is only slightly higher than what they are running now. You can get there just by running more boost with no changes to the bottom end.
220 Bar is only slightly higher than what they are running now. You can get there just by running more boost with no changes to the bottom end.
I thought stock LLY tunes were around 1800psi peak?? Maybe im thinking of what my previous aftermarket rods were designed around? I specifically remember 1800psi from somewhere.
Stock would produce 2800 PSI max (year dependent) chamber pressures. It was an obvious target since the pressure would climb smartly and flat line at 2800. I suspect it was for emissions.
You only need to add a little timing to pop over the 3,000 mark.
You only need to add a little timing to pop over the 3,000 mark.
Are you running sensors in the glow plug holes? Wondering if my Isspro logger could log cylinder pressures 1-8
Is thre any connection to this and the tick knock? I know that every Duramax dosen't have it and those that do have different variations of what it sounds like. I've never heard any other diesel ever do it, just the Duramax. Anybody ever make a correlation to it and broken cranks?
Its a very interesting subject for sure, would be nice to know exactly why.
And a side thought, if I built my engine there's no way I'd bother buying a new crank if mine checked out ok. Too many guys breaking new ones, even under moderate power!
It is still a fairly common practice for racers to run a "seasoned" bottom end in their cars. Basically run your bottom end for the racecar next year, in the tow vehicle this year. Doesn't explain why people break them on old cranks, but maybe guys with brand new are pushing them too hard right out of the gate.
And IMO I wouldn't do an AF cam with a used crank. Unsure of how changing the firing order would change the stresses halfway through a cranks life?
Sorry for the clutter
And a side thought, if I built my engine there's no way I'd bother buying a new crank if mine checked out ok. Too many guys breaking new ones, even under moderate power!
It is still a fairly common practice for racers to run a "seasoned" bottom end in their cars. Basically run your bottom end for the racecar next year, in the tow vehicle this year. Doesn't explain why people break them on old cranks, but maybe guys with brand new are pushing them too hard right out of the gate.
And IMO I wouldn't do an AF cam with a used crank. Unsure of how changing the firing order would change the stresses halfway through a cranks life?
Sorry for the clutter
Mine had this for the first 40 000 miles then it went away for the most part. Once in awhile it would do it after that. Then I broke a crank at 120000 miles.........Is there a connection? Maybe...
Something I never put out there is that the force on the crank to make the variations that you are seeing in these plots is on the order of 40,000 ftlbs if the whole crank is actually being accelerated/decelerated the shown amount.
I don't think that is the case. Because of twist, not nearly as much of the crank's inertia is coming into play. Probably on the line of 1/4 of the inertia, so say 10,000 ftlbs which translates to about 60,000 lbs on the rod journal.
That seems like a lot, but each piston and rod pushs on the journal with 25,000 to 30,000 lbs cruising down the highway.
Bottom line is the velocity changes are significant and need to be looked into in more detail with better measuring techniques.
I don't think that is the case. Because of twist, not nearly as much of the crank's inertia is coming into play. Probably on the line of 1/4 of the inertia, so say 10,000 ftlbs which translates to about 60,000 lbs on the rod journal.
That seems like a lot, but each piston and rod pushs on the journal with 25,000 to 30,000 lbs cruising down the highway.
Bottom line is the velocity changes are significant and need to be looked into in more detail with better measuring techniques.
Have you had a chance, John, to test again with a viscous damper and see if it eliminated that frequency or shifted any of the frequencies at all?
I believe I mentioned that same thing in the other thread you started a year ago. Several times actually. But got ignored and or deleted.
Stock and ATI only so far for dampeners. I don't think a dampener has enough mass to smooth this out. Look at the scale of the fluctuations. 10% in some cases. You would need an additional 20# mass to even dent that.
Still looking for the source.
Still looking for the source.
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Would we? Assuming that the Alt. Firing order reduces that 10% change in velocity even by half, and that it is not the entire cause for the cranks to start cracking, but instead a contributor, maybe we add some rotating mass to the damper and also find a way to dampen the wave that could be weakening the material at that journal?
Edit: Also, because the viscous dampener may dampen a wider range of frequencies, the extra-mass theory may not hold true. The ATI dampener is really only tuned to dampen one natural frequency at a given velocity, not multiple.
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