With mostly well-known rail pressure/untunable “chips” (that are unfortunately very common in the diesel market), generally what happens is that the chip is plugged into your fuel rail pressure sensor circuit, which interferes with the fuel pressure signal to give a false reading to the ECU, to fool it into thinking that the engine has low fuel pressure. The ECU will then raise the fuel pressure to compensate for this & therefore spray more fuel into the engine cylinders. This generally will give it slightly more power (sometimes NO more power & in some cases will give it LESS power!) & make it use a lot more fuel; however most do not monitor throttle position so the ECU will just wind the fuel pressure right up at any throttle pressure – as it thinks that you have your foot flat the whole time. Most of these common “chips” also do not alter the turbo boost level either.
Installing a pre-done “chip” into your engine’s ECU is a very basic method of increasing its performance (very “old school”, even the brand new chips are!) & as mentioned above, a very substandard result is usually achieved. A far better method of increasing an engine’s performance is a REAL custom dyno tune/ECU re-map. Here at UDT we carry out full custom dyno tuning of the standard ECU here via our software & hardware & in-house dynos. Our experienced engineers will have complete control over manipulating & custom tuning the standard maps inside the standard ECU, giving a MUCH better result – excellent gains & power & torque across all rev ranges, excellent throttle control, less lag, more response & improved economy.