Re: GM\'s Duramax Diesel engine
bgott, Yeah, software is a wonderful thing, too bad computers are just a passing fad!
There are other considerations beyond getting more torque and HP out of the Cummins B 5.9 (AKA Super Bee, Killer Bee, etc) Note the torque rating of the 10 cyl gas engine and the Cummins with automagic (automatic)tranny, then note the torque specs with stick. Auto is downrated and in Cal downrated even more (12 valve recollections). The automatic in the Dodge will not safely handle much increased torque. As a minimum I would think the prudent hot rodder (if it waddles and quacks, call it a duck) should go for a beefed up torgue converter. Cummins used to offer an uprate for HP with virtually no increase in torque (for 12 valve) just because of Dodge's weak drive train.
Once you uprate the torque (and actually use it), your torque converter is living on borrowed time. An aux tranny cooler is good but you need a beefier converter (avail from several sources, see TDR advertisers). I put in a BD low stall speed HD converter and have had zero problems but I don't exceed 300 HP and 650 lb-ft.
In marine applications this engine (12 valve) produces 400+ HP for extended run times (days, weeks?) so the basic engine is capable of reliably producing 400 HP for extended periods. Dodge's auto tranny is the weakest link in getting BIG truck performance.
Another drawback is the Dodge automatic overdrive (aka, 4 speed automatic tranny). Third gear is 1:1 so 4th is technically "overdrive" but I come from a time when overdrive was a multiplier available for use in all gears, hence if you had a three speed stick with OD you had 6 forward speeds. A specific difficulty with the Dodge tranny is the HUGE step between 3rd and 4th (AKA OD). If you are not able to pull a hill well in 4th and shift to 3rd you loose a lot of speed since the step is so big. If the hill flattens out a bit but not enough to allow 4th you are stuck at 45-50 unless you don't mind relativistic RPMs in excess of red line.
I added an aux OD to my rig (MFG by Gear Vendors in San Diego) so I have (not counting 4 wheel low range) 8 forward speeds available and can shift in and out of OD electrically under full load with no problems as the unit was designed to shift under load. They sell a version for race boats and dragsters, they are tough. The unit is called a gear splitter as its OD ratio essentially gives you gears midway between your Dodge gears. Pretty handy to have what is essentially 3rd and a half gear for the hill situation I mentioned. I have pulled really steep grades off-road in 1, 1 1/2, 2, 2 1/2, and interstate grades in 3, 3 1/2 whatever does the trick. The down side is that when decelerating with the exhaust brake you must be in a Dodge gear not in a half gear as the gears in the G-V unit are helical cut to develop thrust to assist the unit's clutch in engaging under load. It took a bit of learning but being a drummer and being able to rub my belly and pat my head at the same time I had no major cognitive overload when running through the gears and half gears. I typically use 3 1/2 much much more than any other half gear so it is pretty trivial.
If you don't need to set any cross country minimum driving time records, maybe with a Dodge you need a Gear Vendors aux OD much more than you need to mod the engine. With the right gears you will do much better than with stock automatic. A BIG exhaust will reduce your turbo spool up time and get you off the line much better and add a measureable but small increase in HP at higher RPM and a touch of fuel economy. I went farther than I may have needed but with a utility bed and the largest Lance slide in camper and towing all at the sime time (5ft receiver hitch extension), I probably erred on the side of "MORE POWER!!!. uhh uhh uhh)
Just remember to chant this mantra ("I am my own waranty station, I am my own waranty station...") as Dodge will go to great lengths to deny waranty if you change anything on the engine but the oil.
Patrick
I haven't found a Dodge dealer yet that really knows anything about these motors. I have an injection pump that gets a little funky at times so I'm going to give them a PITA and see if I can get them to let me take it to Cummins. I might also go ahead and pay Cummins to do a diagnostic and throw it in Dodge's face. I can buy a service manual and upgrade my Snap-On scanner and figure it out myself but I damn sure don't want to buy a pump while the engine is still under warranty.