I have to dissagree with the Only Fuel statement pretty strongly. I can't speak for a power box on a P38 as I have never fitted one, but
a remap on a turbo diesel works in the following way.
The ECU controls all elements we are talking about. Fuel, boost pressure and turbo initiating settings.
The remap does the following. lowers the initial turbo 'switch on' by somewhere between 2 and 500 revs, model depending.
on a variable speed turbo, such as on the X5, it increases the turbo spin rate for a given revs, probably mostly as a direct result of initiating it sooner.
increases the peak boost level achievable, to match the additional fuel being fed.
By simply throwing more diesel into the cylinders you would not achieve the the power gains you can get.
Now, it may be different using an inline power box, that I don't know, but a true ECU remap done on a rolling road like Evolve Automotive do does more than just fuel.
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Who said anything about the ECU controlling the Turbo.....what a numb nuts.
I never said the ecu adjusted the boost to match fuel.
When in an hole stop digging for christ sake.