Drop in mpg after remap

torque is a fine balance between air / fuel matching this efficiently (trying to avoid wastage) gives a stronger quicker torque curve
horse power in diesels comes from more fuel at higher revs and also can put a strain on the already high pressure fuel pump
when i had my petrol V6 mondeo mapped via unichip dastek it produced 10lb/ft more torque @ 2k revs whilst using less fuel than previously, its a lot more complicated than just fuel / air mixture, altho thats what most mapping controls especially in diesels :)
 
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UKDTweak said:
Im no car mechanic, did gcse car engineering at school and have serviced (and changed a few engines with help etc)... but how on earth does increasing the cars BHP improve MPG??? that makes no sence what so ever, sounds like you should have got one of those piggy back resistors LOL...
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If you have a turbo charged car (either petrol or diesel) for the most basic remaps there will be no changes to the engine other than increasing the boost and the altered timing/fuelling to suit. When cruising you will be not using the extra power and so fuel economy wouldn't be expected to drop.
 
I think the idea behind increased MPG after a remap is that during town driving you can get away with changing gear a little less due to more power being available lower down the rev range, reducing the need to change down so much.

My car was remapped by the same guy and I've not noticed a decrease in economy, so it could be specific to Joe's car.
 
Taken from the website of a local, very reputable mapping company:

The Overall consumption is governed by the average RPM over a Journey. With more torque you can stay in a higher gear for longer and so maintain a lower journey RPM and improve economy.
 
also bare in mind more power = more heat, so more stress/wear on things. 'remappers' say its within the engines tolerances, but i think thats a un-accaptable, un-professional oninion.

my oil used to steam after a 20 minuite trip on my focus tdci, i've never seen this on any other car.
 
It's really only going to increase mpg if the car's original map was in need of improving in the first place.

I very much doubt a 330d's standard map is going to need improving on.
 
DannyW said:
also bare in mind more power = more heat, so more stress/wear on things. 'remappers' say its within the engines tolerances, but i think thats a un-accaptable, un-professional oninion.

my oil used to steam after a 20 minuite trip on my focus tdci, i've never seen this on any other car.
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The 330d engine is pretty detuned as standard. The biggest strain after the remap is on the turbo. The remap only increases boost at by about 15% on full throttle (which is still WELL within its tolerance).

Antandpete ran a 330d at over 300bhp/700Nm torque (my remap is 210bhp/475Nm) for over 30,000 miles with no issues which says a lot about the rest of the engine.
 
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