6.7 Changes
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To help clear up some confusion on the new engine and the after treatment, I'm going to try and list some of the changes and go into further detail on the after treatment...
Changes To the 6.7 CM2150:
Rod Bearings: Low bearing stayed the same, however, the upper is a new Bi-metal bearing.
Crankshaft: Increase stroke for increase displacement, 100mm machined counterweights.
Piston Cooling: Only piston coolers available are the J-Jet type piston coolers on all ratings
Piston: All use gallery cooled pistons, piston pin is offset for noise reduction, second piston ring is a chrome face rang and not phosphate coated (black). Connecting Rod: Still fracture split, however, it isn't backwards compatible with some rods due to weight differences. The connecting rod orientation has changed as well
Cylinder Block: skirted design with ribs for strength and noise reduction. Cylinders may be bored out to .5mm max. Siamese bores
Main Bearing cap screw: Torque value increased. This limits the number of times it can be used again.
Block Stiffener Plate: On all engines, helps strengthen block and reduce noise.
Vibration Dampener: Dampener and crank tone ring are permanently attached. Drive pulley has increased displacement.
Front crank seal: dual or non lip style which utilize a built in wear sleeve. Because the rotating portion does not contact the crankshaft, wear will not occur on the crank, but will internal to the seal.
Rear crank seal: went back to the old style double lip seal without a wear sleeve, rear seals will come with 2 seal drivers, one for front gear train engine and one for rear gear train engine.
ECM: no fuel cooling on the ECM plate, the new style is a nylon plate.
Cylinder head: same design
Valves and valve seat inserts: New exhaust valve and valve seat material which requires an increased lash setting of the exhaust side (.026) opposed to the old .020.
Head gasket: New design, if valve depth and injector protrusion specs can be maintained, the cyl head can be reused. For the block, if the piston protrusion spec can be maintained, the block can be resurfaced.
Overhead set: .010 on intake .026 on exhaust.
Fuel Pump: Pressure has increased from 1600 bar to 1800 bar.
Fuel Manifold: This has been eliminated. Injector sealing washer: New saucer design.
Oil pump: Mounting bore in the block for the oil pump was reduced in size to strengthen the block.
Water Pump: Increased pulley diameter.
VGT turbo
Grid heater: Incorporated into the intake plate. If the grids fail, the plate will need to be replaced. Since we are dumping EGR into the intake, the intake will self clean itself by energizing if the engine is running for 30 continuous sec. vehicle speed less than 18mph and intake temp is greater than 66 degrees.
Exhaust manifold: New 2 piece design.
After Treatment: There is enough info out there of what the components are in the system so I wont go through that. However, some info is left out concerning when a regen occurs and exactly how the fuel is injected.
Note: For every gallon of fuel burned in the engine, 1 gallon of water comes out the tailpipe in a vapor state.
Passive Regen: This will occur between 482 degrees and 1100 degrees. Fuel dosing is not needed.
Active Regen: If the system cannot maintain at least 482 degrees exhaust temp, an active regen will occur. This is when the fuel is added to the DOC.
Stationary Regen: Fuel dosing occurs and is activated by the driver or the technician using INSITE.
Ambient temp plays a big factor at how long the regen will take. In a nutshell:
Passive: Occurs naturally above 600 degrees (very common in a vehicle that is running down the road and the engine is under load constantly.
Active: Available if passive is unable to decrease soot loading in the DPF. Requires DOC inlet temps of 600 degrees which can be had by the use of fuel dosing.
Stationary: Sometimes you can get away without doing a stationary by increasing the duty cycle (taking the truck down the road and loading the engine in order to do a passive) Or, with stationary, provide notice to driver through the DPF lamp or regen switch.
Show Me The Money Stage: If other measures fail, or operator does not take action, severe engine derate and red stop lamp illuminate. There is no regen available, you have gone too long and the DPF needs replacement.
Temp Variations and conditions:
It takes 482-572 degrees at the inlet of the DOC for a regen to occur.
Over 1112 degrees, the precious metal (platinum) starts to crack.
Over 1382 degrees, the catalyst and filter start to melt.
This system in a good running state will regen between 600 and 1050 degrees.
Fuel Dosing how and what happens: Basically with these injectors, you have a pilot, main, and post injection event. The pilot will occur just a slight amount before TDC, Main will occur at TDC and post will occur while the piston is traveling down on the power stroke.
Now, with this in mind, we can now throw 2 more events in the equation in order to use the in head injectors to dose the DPF. These 2 events are:
Very Late Post BBDC of the power stroke and Very late Post ABDC of the exhaust stroke.
When these two events happen, the EGR valve is shut closed so we do not send fuel back to the intake manifold and all 6 injectors are used in order to dose the DOC.
Hope this sheds some light on the 6.7. Monty
