PowerTech PSS 13.5L (824 cu. in.) engine
John Deere has engineered the PowerTech PSS 13.5L (824 cu. in.) engine to meet the high expectations for fuel economy and performance that operators expect.
Selective catalytic reduction (SCR) is an exhaust filter option that reduces NOx emissions. SCR technology increases in cylinder combustion temperatures to reduce particulate matter (PM) output but as a result of these higher combustion temperatures, it increases the NOx (smog) emission levels. To keep the NOx levels within acceptable standards, a urea-based additive, sometimes referred to as AdBlue® system or diesel exhaust fluid (DEF) is added into the exhaust stream to low NOx emission downstream of the engine. The urea mixes with engine exhaust gases in the catalytic converter. The resulting reaction of adding urea (NH3) (or purified fertilizer) into the exhaust stream and passing through a catalyst transforms the NOx which results in harmless nitrogen gas and water vapor.
Series turbochargers
Series turbocharging delivers higher power density, improved low-speed torque, and improved high-altitude operation. By splitting the compression of the charge air between two turbochargers, both can operate at peak efficiency and at slower rotating speeds. This lowers stress on turbocharger components and improves durability.
Series turbocharging works when fresh air is drawn into the low-pressure turbocharger (fixed geometry), where air pressure is boosted. This pressurized or boosted air is then drawn into the high-pressure turbocharger (VGT or WGT), where air intake pressure is further raised. The high-pressure air is then routed to an air-to-air aftercooler, where the air is cooled and routed to the engine’s intake manifold.
Series turbochargers
- High-pressure turbocharger
- Low-pressure turbocharger
The PowerTech PSS 13.5L (824 cu. in.) utilizes two turbochargers – a variable geometry turbocharger (VGT) and a fixed geometry turbocharger, providing the torque rise and engine responsiveness 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 air is then drawn into the high-pressure VGT where the air is further compressed. The compressed air is then routed to the charge air cooler, and then to the intake manifold. By splitting the work between two turbochargers, both can operate at peak efficiency and at a slower rotating speed.
VGT
The VGT is electronically controlled and hydraulically actuates the turbo vanes as required to maintain peak engine performance.
VGT vanes in exhaust flow
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 impeller. When exhaust flow is low, the vanes are partially closed. This partial closure increases the pressure against the turbine blades to make the turbine spin faster and generate more boost pressure. The ability to keep the airflow flowing 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 turbo lag as can be found on some engines. Boost pressure in the intake manifold is controlled at its optimum point for added fuel economy and performance regardless of rpm or load.
The overall benefits:
- Increased low rpm torque
- Quicker response to load
- Increased peak torque
- Improved fuel economy
- Improved performance at high altitudes
Air-to-air aftercooling
Air-to-air aftercooling lowers the intake manifold air temperature and provides more efficient cooling while reducing cylinder firing pressure and temperatures for greater engine reliability. Since low temperature air is denser, a higher volume of air flows into cylinders so the engine is capable of meeting the increasing horsepower demands.
ELECTRONIC UNIT FUEL INJECTION SYSTEM
Electronic unit injector
Electronic unit fuel injection system on the 13.5 L (824 cu. in.) engine provides the following benefits:
- Variable timing control for improved emissions
- Better control at start of fuel injection for improved starting
- Elimination of nozzle service
- Camshaft-driven transfer pump draws fuel through the fuel filter
- The single fuel rail is a drilled passage in the head, eliminating the need for external lines for reduced service through the fuel filter
The electronic control unit monitors various sensor inputs from the tractor and automatically changes the sheave ratio to change the fan speed. Hydraulic oil pressure is directed to the pistons that push the top inner sheave out (A), to close the gap and create a larger working diameter.
The bottom sheave (B) responds by compressing the coil spring, widening the gap between the two sheave halves, and creating a smaller working diameter to increase the fan speed.
To slow the fan, the valve opens, allowing oil to leave the piston, widening the upper sheave halves.
Automatic shutdown function
This feature monitors engine coolant temperature, engine oil pressure, and transmission oil pressures while the transmission is in the park position, and the operator is out of the seat. If any of the systems reach undesirable levels, the tractor will shut down, to help prevent further tractor damage.
AdBlue is a trademark of German Association of the Automobile Industry (VDA).
ENGINE CONTROL UNIT (ECU) - FULL AUTHORITY ELECTRONIC CONTROLS
This engine control unit 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 to deliver peak fuel economy and 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. The ECU can sense engine speed and load changes at a rate of 100 times per second and respond instantly to them. 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 proper power levels at high elevations.
Noise reduction
The injection system also contributes to the engine running at a decreased noise level by a process called pilot injection. The precise fuel injection capabilities allow a small amount of fuel to be injected early in the combustion process. This helps lessen the combustion knock that is commonly heard on many diesel engines. While the combustion noise reduction is most obvious at lower engine speed, pilot injection continues to function at any engine speed.
VARI-COOL™ SYSTEM
9R cooling package
The Vari-Cool fan drive system precisely controls the speed of the fan in relation to the cooling requirements to maximize efficiency of the engine. The Vari-Cool system is efficient for two primary reasons:
- The belt drive used in the Vari-Cool system transfers almost 100 percent of the power from the engine to the fan.
- The variable fan speed sheave is electronically controlled only operating at the necessary speed to cool the engine and other auxiliary components.
Vari-Cool is integrated into the hood design
The Vari-Cool system is an integrated part of the hood design. Intake and outflow of air from the coolers is diverted to key openings in the hood structure. The design allows for airflow dispersion that lessens dust and crop kick-up by discharging the airflow away from the cab.
How Vari-Cool works
This electrohydraulic system uses variable speed drives. Actual fan speed is determined by the ratio differences of the top fan drive sheave to the bottom sheave.