Mazda BT50 chip and rail pressure

Q. I’m considering buying a plug-in tuning chip for my Mazda BT-50 and I’ve heard that some of these work by changing the rail pressure and that this can have a detrimental effect on the engine, maybe even damaging the rail or injectors. Can you shed some light on this?

A. If you look at the injector signal and the fuel pressure you would notice that the duration of a CRDi injector doesn’t change a lot, from maybe 900ms to 1200ms.  On the other hand if you were to measure the fuel pressure in the common rail, you will see it changing all over the place from a mere 5,000PSI at idle right up to over 30,000PSI at full load. Basically, this speaks for itself in that you have very little time to get fuel through an open injector. You can’t just keep opening it earlier and earlier as revs and load picks up, or it would rattle from way too advanced timing. You also can’t just hold the injector open longer and longer to get more fuel in, otherwise the extended injector duration would be just pouring in fuel onto a piston already heading down the cylinder bore.

To get more fuel in quickly and precisely, you’re best doing exactly what the manufacturer does; increase fuel pressure under demand. This topic is widely debated and is used in some very unscrupulous ways by some chip makers to confuse the customer.

Correct control of the amount of fuel comes with a good chip. I have found a lot of European or UK-based chips just make a ‘fixed change’ to the fuel pressure. In other words, once the chip starts working, it adds a flat 10% more pressure. The problem with these sorts of chips is that they don’t reduce the fuel pressure as it reaches its maximum. They just keep it going higher and higher until something leaks.

A DPChip on a Mazda BT-50 is plugged in to the vehicle’s wiring loom with factory plugs. DPChip, for example, varies the engine’s factory signal in a way so as to make the engine’s ECU make controlled changes to fuel timing and pressures. These areas when correctly controlled allow safe increases to be made to power and torque, leading to a much more nimble engine and adding to the potential for better fuel consumption.