#How chip tuning works in engine with VP44 pump

11 / February 2022
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How chip tuning works in engine with VP44 pump

Seletron Performance

How our chip tuning units for engines with VP44 radial piston injection pumps work.

Here we are with the second installment related to the specific operation of our power-boosting chip tuning units on diesel engines that mount an injection system consisting of the more complex VP44 radial piston injection pump.


Perhaps we should speak in the past tense, as cars with this injection system have not been produced for many years, and, as a result, the demand for chip tunings to upgrade these engines has decreased to rare requests. Now let's discuss the construction differences of these injection pumps compared to the previous rotary pumps we discussed in the previous article. (Here is the link to the article vp37 chip tuning modules)


How do radial piston injection pumps work?

The previous article showed how a single pumping element acts as both a pressure generator and a distributor in rotary injection pumps. In practice, the (single) pumping element makes two movements: one alternating (pumping) and one rotary (distributor). This means that while compressing the diesel fuel, the piston rotates to distribute the flow of pressurized diesel fuel to the corresponding injector through a series of holes (one for each cylinder of the engine).



Electronically controlled rotary injection pumps, mainly manufactured by Bosch, are made for both indirect and direct diesel injection systems. The relatively more modern radial piston injection pumps use one pump (a small piston) for each cylinder. These pistons are radially fitted to the camshaft that drives them, hence the name "radial piston pumps." This type of pump originated exclusively for direct diesel injection systems, has a higher (even double) injection pressure than that generated by rotary pumps, and has a different electronic control system.



These pumps already had some electronics built into the mechanical body, from which four wires led out to two solenoids controlled in PWM by the same electronics. The control of the injection pump by the ECU (at least in the more complex versions) was handled via CAN-BUS (Controller Area Network). This was a standard bus protocol used predominantly in the automotive field. We have two additional chip tuning models for this type of pump.


The first chip tuning module connects to one of the wires of the injection flow control solenoid and the power supply, grounding, accelerator pedal position signal, and MAP sensor signal connections for turbo pressure sensing in certain models.


The second model of chip tuning additional unit, on the other hand, connects directly to the pump connector where there is CAN-BUS communication, power, and grounding.


How does a wire model radial piston injection pump chip tuning unit work?

The operation of the chip tuning units for radial piston injection pumps is partly similar to that for rotary injection pumps, at least from a general point of view. Based on the engine load demand coming from the driver (by reading the signal from the accelerator pedal position sensor), the unit implements an increase in injection delivery by following internal digital maps. What changes completely is the way the increment is implemented.


Through the connection on the wire controlling the injection delivery solenoid, the tuning senses the control signal determined by the car's ECU and extends its drive time to achieve higher diesel injection delivery. In practice, the connection between the radial piston pump and the chip tuning is both signal sensing and power output. Within the chip tuning unit, the parallel control of the injection delivery control solenoid is entrusted to a solid-state amplifier, specifically a Mosfet/Hexfet type semiconductor. This is because of the ability of these semiconductors to switch high current values quickly and to absorb reverse extra-voltage peaks without problems. In addition, the very low RdON value of these semiconductors (the resistance in milli-Ohms during the ON phase of the component) allows reduced values of power dissipation due to the Joule effect, thus a very low heating of the injection pump control amp.


How do chip tuning units for CAN-BUS model radial piston injection pumps work?

This model of chip tuning unit does not require external connections, but using the connector in the pump, it manages to take both the power supply, positive and grounding, and the can-bus signal, which supplies all the data needed to operate the pump.

In this case, the chip tuning operates by working in series. It receives signals from the main ECU, processes them, and gradually increases the output signal under the conditions of acceleration and full power.

It is no longer necessary to directly operate the pump's solenoids, as the electronic management will do so thanks to the new data that is sent via can-bus communication.

One of the advantages of this system is the speed of installation because you only need to connect the supplied connectors to the original pump system.


The first cars to feature diesel engines with radial piston injection pumps

The first cars to feature these radial piston injection pumps (and thus the first cars we processed with our chip tuning additional units) were the 136hp 2000 BMW 3 Series (320d), the 150hp and 180hp AUDI 2.5TDI V6s, the 82hp or 101hp OPEL 2.0 DTI 16Vs, and the 90hp FORD 1.8 tddis. The power increases on the 2-liter BMWs were around 25hp, about 20hp on the 2-liter OPEL and on the 1800 FORD, and around 30hp for the V6 AUDI 2500. 


Let us also add that the chip tunings for some of these engines also required a serial connection on the boost pressure sensor (MAP). This was to avoid ECU recovery resulting from turbo pressure spikes that were deemed inconsistent with the software within the memory of the engine control unit. For the early 2000s and up to and beyond 2005, there were many requests for this type of diesel tuning kit. BMW 320d 136hp E46s were often the subject of electronic tuning with this system, and many OPEL customers turned to us to increase the power of their 2.0dti mounted mainly on Astra, Vectra, and Zafira models.


In the 2000s, some sooner and some later, BMW, AUDI, FORD, OPEL (and the other automakers that shared the same engines) switched to the more refined and flexible common-rail, which we will discuss later after addressing the interesting topic of injector-pumps!


Until next time!


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