Anyone found the limits of a 6.7 Cummins block?

Mopar Muscle said:
The 6.7's that have survived 1,000+ hp have all been with large singles with less useable torque down low. I'm planning a triple build with my 6.7, so I'm worried about the block handling 1,800-2000 ft-lbs at low to mid rpm levels. It seems that compounds on 6.7s seem to be the killer (usually rods). Just wanting to find out what I need to worry about if I have a set of billet rods, pistons that will hold up, and a real girdle. A reputable source on here told me that the cylinders can crack. I just wanted to see if I could find a first-hand witness to this problem.
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I know of a few 6.7 that were north of 1200HP and the cylinders cracked with a large single.
 
so im wondering why have people not started tuning the bottom end torque out of these?ive had several discussions about this and it makes sense no sense to make this much torque that low.
 
It's helpful to think in terms of cylinder pressure delta/ crank degree
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Mike, do you have a feel for peak cylinder pressure limits and preak pressure rise limits for the 5.9 and 6.7 Cummins? ...or more specifically what these numbers look like on a 900 hp / 1600 ft-lb ISB?

I know in *general* terms for light/medium duty diesels that we test at work, most limits set by OEMs are around 160 bar peak pressure and 10 bar/degree pressure rise. However, I don't have a feel for what those numbers would look like on are engines that are 2x, 3x, and beyond the stock calibrations. It seems some manufacturers are approaching 200 bar peak pressure with the trend of smaller displacement, highly turbocharged platforms.

--Eric
 
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So,, let me ask a question. In a racing application, say approx 4000- 4500 RPM, about 12-1400 HP, would Billet Rods, filled block and a girdle be enough to hold it together?
 
morkable said:
So,, let me ask a question. In a racing application, say approx 4000- 4500 RPM, about 12-1400 HP, would Billet Rods, filled block and a girdle be enough to hold it together?
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I would say yes if your not trying to make all your power below 3000rpm. My new 4BT engine is going to turn 5000rpm and I'm tuning it to make power above 3000.
 
I know Ken Jones with Wild Diesel was in works of a billet block about a year ago. But you better have a liquid cooled credit card!
 
I have personaly seen filled 6.7 blocks crack after two seasons of pulling. This is on a 3.0 class motor about 65 psi boost so i dont think boost is the issue. Boring the blocks out and having them sleaved seems to be the way to go if your set on running one of these blocks
 
Eric, I've seen >250 bar peak for thumpers - won't comment specifically on max allowed pressure delta increments, but even OEM limits provide for ample power increases within available ignition-blowdown windows... and remember that combustion expansion rate varies far less with RPM than piston speed.

CTD/EFI Live in conjunction with combustion pressure sensor traces is an effective way to tune to just this side of parts failure.
 
XLR8R said:
CTD/EFI Live in conjunction with combustion pressure sensor traces is an effective way to tune to just this side of parts failure.
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Have many people installed cylinder pressure sensors on the Cummins? Any clue as to how much that might cost for the sensor/s? I've got a nice Nation Instruments DAQ system that I'm sure would work to data log.
 
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Mopar Muscle said:
Have many people installed cylinder pressure sensors on the Cummins? Any clue as to how much that might cost for the sensor/s? I've got a nice Nation Instruments DAQ system that I'm sure would work to data log.
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i really feel they would survive in a non water injected application.
 
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