Why limit your RPMs to 2500?
Just how the cards that are in play pan out. First the twin hx35s with 10cm housing by estimate, will start building boost at 1000rpm and be at the limit around 2400. Second is Im going to get cummins marine injectors from @CBRF3, he say there good to 2500. Third is I like the zf 460 ratio with 3.73 gears, this will be in the window of 1500 to 2400 rpm. If down the road I add in a type4 cam, that would also give benifit in this range. Also this range would give good fuel economy, in the end adds up to a beneficial range.
Running 20lbs at <1500rpm is how you bend rods
This build is using powerstroke rods, it will take a bit to bend them.
Seriously every big HP diesel built right I've seen or read about runs high RPMs not lower. The bottom end can't handle that kind of torque, so move it up the RPM scale.
Parts are on the table and cant change them, so there is no changing the target scale.
But say 40psi at 3000rpm would be comparatively much gentler on the same setup.
30psi at 2800rpm was a though but has issues with durability in the long run. That could get me close to the 350whp range running a 130cc pump. But am told that is were pistons and precups crack, see a lot of mention of it in the 6.2/6.5 forums as well. So would need to scrafice the 6.9 for testing to see if a resolution can be found, Im not in a state to do such so not valid path. This is what I found would need to be tested and where a posible resolution can be found.
So might see a solution to the cracked cups, it may be stagnet thremal expansion out the cup and across the piston. The sister engine sees this piston cut and pre-cup shape as the solution to get the heat out the cup. This could be a starting point for testing, just have a guinea pig engine with egt sensor in place of glow plug straped to some load. The 6.9 can have new bearings slaped in her and set to be killed again like kenny.
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EDIT: found another variant of a cut for bowls
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What I have gathered about cup port is they need to match fuel supply given. This is a photo I found of 6.5/6.2 precups, the ones for the 7.3/6.9 are around size of one the top three. They found best life of the cup using one the bottom two when going for power, that is T and diamond cups. On the other hand the small port ones work out best for N/A and low power turbo setups.
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