One of the things that set Cummins apart from other manufacturer's engine products was and historically, still is, its unique PT Fuel System. Although this system is being phased out by electronic engine management technology, it remains a fascinating and yet so simple central characteristic of the Cummins diesel design.
The PT system is not the original fuel injection system used by Cummins. Before PT, Cummins had a distributor type fuel pump with external flyweights like a steam engine.However the PT fuel system, once introduced, served Cummins well for four or more decades and was applied to every Cummins engine produced during most of that time.
"PT" stands for "Pressure/Time".
Fuel is supplied by a pump at low pressure (typically <200 psi) to a common drilling along the cylinder heads and adjacent to the direct injection injectors. From this drilling, essentially a fuel manifold, the injector is supplied fuel in an amount determined by a combination of both engine speed (time) and fuel pump pressure, at any particular phase of engine operation.
The mechanical injector is camshaft driven, thus the length of its delivery stroke is fixed by the cam lobe profile. As the injector plunger rises (from its seat aided by a return spring) it uncovers a port which accesses the fuel supply and fuel is allowed to enter the lower cavity between the end of the plunger and the injector nozzle ("cup" in Cummins speak). As the camshaft then forces the plunger down again, the fill port is blocked by the plunger movement and the trapped fuel is forced and through a small number of spray holes (6-10) and introduced into the particular cylinder. Pressure developed at the cup courtesy of the mechanical action is sufficient to atomize the fuel spray thus enabling compression ignition and combustion. That is the simplistic version but it really is not much more complicated than it sounds.
The fuel pump is a simple gear pump, the output of which is determined in the first instance by engine RPM (directly driven, usually at crankshaft speed) and in the second instance by a flyweight actuated governing valve. A delicate balance is achieved as four different sized springs (weight assist, torque, governor and idle) act in a single line, albeit in different phases of engine operation. Between the springs are a governing valve and idle plunger.
As the name suggests, engine performance is then achieved by a unique balance of fuel pressure (determined by the fuel pump mechanism, throttle position and engine rpm) and the time opportunity afforded the injector.
In a system such as the basic PT automotive governing system, the engine rpm is not directly relevant to the throttle position. With no engine load, 5% throttle application from idle will likely achieve 100% rated rpm - whereas at full load 5% throttle application (from idle) will certainly not sustain even engine idle speed itself. Notwithstanding the latter extreme example, the governing system works fine in an automotive application however something different was required for other applications such as marine, agricultural and generators.
Modified PT fuel systems therefore include additional governing capabilities - to make the engines behave more like, say, an agricultural tractor, where 50% throttle application might reasonably deliver 50% of the rated engine rpm while the load, or power required, may vary within a designed and controlled range. Higher throttle settings (read "rpm") results in higher power availability.
Some applications require constant rpm and variable load, maintained within a specified "droop" or rpm range. Such is the case with generator sets for example.
To address these applications, Cummins designed and implemented VS (variable speed); MVS (Mechanical variable speed); SVS (Special variable speed) and later EFC (Electronic Fuel Control) versions of the PT fuel system.
The last era of the PT fuel system involved HVT (Hydraulic Variable Timing), MVT (Mechanical Variable Timing) and STC (Stepped Timing Control) injector systems. These each represented different modifications to the basic PT principles, but all with a common purpose and that was to vary the injection timing typically for a balance of better emission control at low engine speeds and sufficient power under load.
In 1989, Cummins released the first of the Cummins Celect fuel systems which would signal the beginning of the end for the PT mechanical products. Celect (Cummins Electronic) utilizes a solenoid switched (camshaft operated) mechanical fuel injector and a simple mechanical gear type fuel supply pump. Fuel Pump supply pressures are typically lower than they were under the full mechanical system however different camshaft characteristics provide higher injection pressure while an engine mounted Electronic Control Module (ECM) with data supplied by various engine sensors, determines and controls injected fuel volume and timing.
In 2006-2008 Cummins rolled out new engine systems that incorporate technologies such as Common Rail fuel injection and Exhaust Gas Recirculation (EGR) in order to keep pace with ever increasing demands for better emission controls, better power and improved fuel efficiencies. Make no mistake that emissions drive technology today like never before.
As far as the mechanical systems are concerned, Torquepower has its own PT Fuel Injection Service Facility, the best of its kind in Australia. Cummins PT injectors and Fuel Pumps are remanufactured to original calibrations right on site. Each Fuel Pump is carefully calibrated so that the performance criteria of the Cummins engine are as close as possible to when it was delivered from the factory. A wide range of exchange items ensures that you can always get the right injectors or fuel pump for your specific application in the shortest possible time.
Torquepower carries a broad range of exchange assemblies for Cummins engines and among these is a comprehensive range of Cummins PT type Fuel Pumps and Fuel Injectors. These assemblies are reconditioned in our own well appointed fuel rooms using the industry standard Hartridge and Bacharach test and calibration equipment.
All PT (mechanical) injectors from small V6/V8 through to NTC444 STC and K/KT/KTA injectors are remanufactured and held in stock ready for immediate installation.
Cummins PT Type Fuel pumps are available on a factory calibration exchange basis and include options for all major applications for on-highway, industrial, generator, agricultural and construction engine models.Dozens of remanufactured fuel pumps are specifically calibrated and ready for immediate service while dozens more are remanufactured but remain un-calibrated until the customer specification is advised. This enables us to meet EVERY exact calibration need on a fast turn-around basis.
Torquepower carries the widest range of calibration component part numbers to ensure that your EXACT specification can be delivered to Cummins factory specifications. We will never "make do" with a component that is "near enough". Your investment depends on our investment and we have invested well in our fuel room capability since 1985.
EVERY Torquepower re-manufactured Cummins injector includes a NEW injector cup (nozzle). Torquepower does NOT "re-qualify" such critical parts by inspection or any other means. The injector cup is responsible for proper atomization of the fuel into the cylinder and therefore impacts both fuel economy and exhaust emissions most directly.
Torquepower re-manufactured Cummins Fuel Pumps are thoroughly overhauled and no corners are cut here either. Throttle shafts, governor shafts and air fuel control shafts are sized to ensure as-new performance. Gear Pumps are NOT repaired but are replaced with either new or Cummins ReCon gear pumps as required.
With undisputed quality and competitive pricing, you can be confident that a Cummins PT Fuel Pump overhauled by Torquepower will provide precise engine performance in all respects. That is our mission and it is at odds with independent fuel rooms that may want to give you "more fuel" at the often unstated expense of shorter engine life.
Torquepower was the first (and perhaps remains the only) Cummins fuel injection service facility to install the Hartridge HK860 Celect Injector calibration phasing device as an enhancement to its Hartridge HA290 Test Bench. The combination of these two Hartridge systems allows us to test Cummins Celect injectors for ongoing serviceability. If one or more injectors fail to deliver to Cummins specifications, then we will offer to replace it with a Cummins ReCon Celect injector from our inventory. Torquepower does not offer in-house re-manufactured Celect injectors.
All exchange items purchased from Torquepower are offered on a Core Return basis. Provided your old core meets published re-use or rebuild guidelines, your core deposit will usually be returned in full. In the case of unacceptable damage to the trade-in item, a lesser value than the core deposit will mostly apply. If you wish to retain your old unit rather than return it as a core, we can often offer the exchange unit on an outright basis at a value that is less than the sum of the exchange price plus core deposit.
Torquepower carries the largest range of exchange Cummins product of any Cummins dealer in Australia.
Pricing is competitive and service is exceptional.
Exchange assemblies can only be purchased via the traditional supply model, that is, by speaking with one of our highly trained parts interpreters, or sending your Purchase Order by fax or email. All Exchange items are available through Clessie OnLine on an exchange basis only. Because of freight complications, Cores cannot be returned for Core credit.
So call Neil, Tony or Ken for your next Cummins parts requirement - or visit Clessie Online anytime.
