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• by Brian Weatherley According to Giran Blomberg, Scania's product manager for HPI engines, the original project partners of Cummins and Scania took their time when deciding which engineering direction to take before finally going down the HPI route.
Initially, Iveco was also part of the fuel-system project; it backed out before 1992 when the main HPI agreement was signed between Cummins and Scania.
Organic development
The first full application of HPI was in Cummins' 15-litre Signature in 1998, although elements of HPI had previously been applied to some highhorsepower Cummins engines using the PT fuelling system. This was based on a variable pressure system, but with constant timing of the metering system. The PT system operated at up to 1,800 bar (normally 1,400 bar under full load); idle pressure was very low.
According to Blomberg, PT "was a lazy system—response was bad. Then we changed to the TP
system with vari
able timing and constant pressure."
The TP concept features in Scania and Cummins HPI engines, operating at up to 1.800 bar with an electronic solenoid controlling the opening of the injectors.
Blomberg reports that the downside of moving to such high pressures is that while NOx is contained along with other emissions, "you get problems with smoke emissions. We name and a lead to a lighter E are currently use 1,500 bar for Euro-3 and less compli but the intention is to go to 2.400 bar. Gated design.
although we can live with 2,000 bar and with EGR you can get rid of the smoke."
Scania will adopt EGR for Euro-4, Blomberg adds: "We don't need it till then but we are running EGR trials at the moment." The 12-litre is likely to be the first engine in Scania's diesel family to have EGR.
With the advent of its 470 turbo-compound engine, Scania has also introduced its own engine control unit, based on a