John Deere 6M Series Tractors feature the reliable and proven PowerTech PVS 6.8L and PSS 4.5L and 6.8L engines. These air-to-air aspirated engines deliver a power bulge above rated power to provide excellent torque in demanding applications.
- Series turbochargers (PSS only)
- Variable geometry turbocharger (VGT)
- Air-to-air after cooling
- High-pressure common rail (HPCR) fuel system
- Engine control unit (ECU)
PowerTech PSS/PVS engine identification
- S – Exhaust filter and selective catalytic reduction (SCR)
- X – Exhaust filter
- V – VGT
- S – Series turbochargers
- W – Wastegate turbocharger
- P – PowerTech Plus
- E – PowerTech E
PowerTech PSS 6.8L engine
- A constant power range of 2100 rpm down to 1500 rpm
- Power bulge of 10 percent
- Greater tractor productivity
- Responsive power reducing the need to downshift the transmission
To match the engine power characteristics and improve the operation economy of the machine, the rated engine speed is 2100 rpm.
The PowerTech PSS 4.5L and 6.8L engines utilize two turbochargers – a VGT and a fixed geometry turbocharger. This provides the torque rise and engine response needed to meet varying load conditions.
Fresh air is first drawn into the low-pressure fixed geometry turbocharger and compressed to a higher pressure. The compressed, higher pressure air is then drawn into the high-pressure VGT where the air is further compressed. By splitting the work between two turbochargers, both can operate at peak efficiency and at slower rotating speeds.
PowerTech PSS engine series turbochargers
- Deliver high-power density
- More low-speed torque and responsiveness to meet varying load conditions
The VGT is electronically controlled and actuates the turbo vanes as required to maintain peak engine performance. PowerTech PVS 6.8L engines only have a VGT turbocharger.
The turbocharger’s vanes are in the exhaust flow. The opening or closing of the vanes changes the outlet volume and airflow speed against the turbocharger turbine. When exhaust flow is low, the vanes are partially closed. This partial closure increases the pressure against the turbine blades to make the turbocharger spin faster and generate more boost pressure.
The ability to keep the airflow at optimum levels provides more consistent engine boost pressure and the ability to respond to load quickly across the entire engine rpm range. This system is without the turbo lag that can be found on some engines.
- Increased low rpm torque
- Quicker response to load
- Increased peak torque
- Improved fluid economy
- Improved performance at high altitudes
Air-to-air after cooling
Air-to-air after cooling lowers the intake manifold air temperature and provides more efficient cooling while reducing cylinder firing pressure and temperatures for greater engine reliability. Since lower temperature air is denser, a higher volume of air flows into cylinders so the engine is capable of meeting the increasing horsepower demands. Lowering the intake manifold and cylinder temperatures also aids in lowering the combustion temperature, which lowers the NOx produced as a result.
- Higher horsepower
- Less NOx production
HPCR fuel injection system
Every PowerTech PSS 4.5L and 6.8L engine utilizes a HPCR fuel system to efficiently supply fuel to injectors. The high-pressure fuel pump instantly responds to requirements for more or less fuel flow or pressure. This electronically controlled, high-pressure pump delivers pressure on demand according to the application requirements. Pressure on demand ensures an efficient injection system resulting in high-injection pressure independent of engine speed.
High-pressure common rail
- Instantly respond to load changes reducing the need to change gears
- Improved fluid economy
Engine control unit (ECU)
The ECU uses signal inputs from sensors and pre-programmed performance modeling to control critical engine functions such as fuel quantity, injection timing, air-to-fuel ratio, multiple fuel injections, amount of cooled exhaust gas recirculation (EGR), and a host of other control parameters.
- Optimized fluid economy
- Maximum engine performance
Each injector is controlled individually by the ECU. The ECU turns the injector on and off during each firing cycle to control the fuel delivery into each cylinder.
Load and speed sensing allows each cylinder’s fuel delivery rate to be adjusted independently at the individual injector. With each injection cycle, the ECU can make the following adjustments on the go:
- Number of injections
- Fuel pressure in the common rail
- Start of injection
- Duration of injection
This management system is connected to the transmission, allowing the engine and transmission to respond simultaneously.
Cold weather and high-altitude compensation are also precisely controlled for quality starts regardless of weather and maximum performance at high elevations. The ECU also features improved diagnostic capabilities. It is faster, has more working memory, and is responsible for monitoring and executing all aspects of the integrated emission control system.