Workshop: Diesel Tuning


Words and image by Martin Pretorius

Diesel Dilemma

Turbodiesel drivers can find the promise of a whole lot of extra engine power in the classified-ad sections of most motoring magazines. Power purveyors claim output improvements of up to 20% on a modern, common-rail-equipped vehicle, along with sharper accelerator response – all thanks to a few relatively minor changes to the operation of the vehicle’s Engine Control Unit (ECU).

The temptation is hard to resist. Who would say no to a little more “oomph”? turbo has enough reserve capacity, the boost pressure can be increased slightly (typically by 0.2 bar), to cram more air into the engine. All this extra air now allows for more diesel to be injected, which generates more power – and all without raising the EGT.

Clever. But that’s not all there is to it, right?

It is, indeed, a little more complex than it sounds, because the ECU needs to inject more fuel into the cylinders. This can be achieved in three ways. First prize is ECU re-mapping, which refers to the technique of directly changing the programming in the ECU, either by physically replacing a chip inside the computer, or by accessing the ECU through the car’s diagnostic port, which is a mandatory fitting in modern cars, located within 60cm of the steering wheel.

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