As European members will be aware, turbo diesel engines are deliberately detuned by manufacturers for a host of reasons, including emissions regulations, insurance and mechanical reliability. Retuning them is relatively simple and very popular, because generally power goes up and fuel consumption drops (due to the extra 'free' torque available).
I had my previous e39 530d (193hp stock) custom remapped to 220hp, but this time, after much research & deliberation (thanks to all those on this forum who provided input), I decided to order the
TuningBox solution.
This is basically an extra box that you plug into the engine management system. It's only a generic remap (i.e. not specific to my individual car) and less sophisticated than the custom remaps, but the advantages, IMO, are lower cost and the fact that I can remove it if I am not happy, or before taking the car into the dealer (thus avoiding any warranty 'issues'). I was also concerned that a custom remap may be wiped out by the dealer when they plugged in their diagnostics/upgrade computer...
Being a cautious bunny, I was also sold on the TuningBox's relatively modest power upgrade. They claim 276hp & 562Nm torque, which based on my personal experience & other manufacturer's claims, seems quite feasible and shouldn't pose any problem to the Steptronic gearbox, which has a breakage factor of 1.7 (i.e. it can handle 500 x 1.7 = 850Nm). Installation should be straightforward and I have already successfully tried a similar box on my VW Golf TDI.
I am expecting delivery early next week and will endeavour to take photos of the install and, of course, post a subjective report on how the car feels after the surgery.
Cost for those interested was €420, or approx. $530.