Deeyup - you dont get much economy from the diesel tuning box.
If a 'real' remapper opens a file and highlights the injection duration areas - he will show you the figure for rail pressure, and if he increases the data 'inside' that map, you will have a faster car.
I call this a 'tuning box remap' - and I have purchased files from so called tuning companies on ebay and their remaps represent this same, shoddy version of a real remap... where areas like 'drivers wish' (throttle maps), 'torque limit' (where the power is mostly controlled), 'airflow vs injection' (known as the 'smoke' map), SOI (similar to IQ/Injection Duration), along with a few minor changes here and there for a decent, all round increase in power - while maintaining good economy.
The problem with the tuning box (shoddy) remapping, and the tuning boxes, is that they trick the rail into thinking it isn't providing enough pressure.... so, the box will make the pump work harder (as explained by Scoop) and it isn't the pump I worry about from a tuning perspective - it is the injectors that leak and cause most damage - even on low tuning box settings I have seen engine problems after fitting them.
The boxes are cool, in their own light. You get people who fit boxes because their vehicle is under warranty - and they dont want to be stung for servicing if something goes wrong with the car. They generally represent the people who own 'fleet' vehicles and aren't responsible if it breaks....
Most people with common sense would have a tuning box - keep it on a low setting, and enjoy the increased power responsibly, just as people should when having their vehicle remapped/chip tuned for more power.
As for economy. The Injection Duration/Injection Quantity maps I mentioned are connected to the MPG display inside your car (and data logging, if you have this feature). When a tuning box/crap remap is done - the car 'thinks' it is still using the same amount of fuel as before - and when you cruise with the tuning box it thinks everything is REALLY AMAZING and you should see a better figure on the display.
So. People 'think' they are getting better MPG after fitting a tuning box. The more likely story is they aren't... because they are using more power (and thus more fuel), but are fooled by the MPG reading and claim the best figures on earth.
It isn't easy getting better MPG from any vehicle after tuning.
Petrol cars - FORGET IT. You cannot make a naturally aspirated engine better on fuel, but you might see a slight improvement because more torque is available, and you dont have to floor the throttle as much as before.
Petrol turbo - YOU MUST BE JOKING!! For these vehicles to make power, you need BOOST!! Boost = EXPENSIVE FUEL BILL, and when you increase the wastegate opening (along with fuel and maybe some timing advance at lower revs before the turbo kicks in... this is what makes the cars power feel more linear after writing a modified file) then you will never see better MPG. If somebody has a 1.4t fiat with a tuning box a test driving the car with and without will prove this. I would fill the tank twice with the box on and off and see the change in economy.
Turbo Diesel - YOU CAN SAVE FUEL WHEN CRUISING, BUT MOST PEOPLE WANT 40HP+++ INCREASE AND PUT THEIR FOOT DOWN MORE BECAUSE THERE IS MORE POWER THERE.... So in short - most turbo diesel engines get the same MPG as before once tuned, but if the driver changes his style the MPG figure will increase without the need for a remap.
Tyre Pressures/Tyre Choice/Less Weight in the Vehicle/Accellerating Slowly/Letting the car slow down when you see a Red Traffic Light/Only putting half a tank of fuel in the car (less weight) - will all help towards a better MPG figure.
If its power people want, vehicle tuning is cool. If it is economy, there are other things that will cut your fuel bill. Buying a Diesel/Turbo Diesel would be my advice.
Hope that helps. Sorry if I went on a bit - I dont get on this site often.
