Sorry to butt in when my car is not an MB, but Experience of using these boxes on the VW forums seems a bit sparse.
I have recently purchased a TDI-tuning.co.uk box for my MK7 VW Golf GTD. Stock 181BHP (184PS) and the dual channel box ramps it up to 239BHP (243PS) apparently, with mpg gains. I have been scrutinising my mpg as it is 30% off published combined figures. On paper it is 20% more efficient than my last car, a 170TDI VW Scirocco, yet cannot even match what the Scirocco was doing in the same usage. I’m getting an actual (brim method) 42.5mpg consistently (which must mean not much variance in my driving style), but indicated varies from 44 – 50mpg. The Scirocco was 50mpg indicated and 45mpg actual on short journeys and 10% more for longer journeys. I drove the Scirocco a lot harder than the GTD too. To say I feel a bit diddled by VWs claims is an understatement.
The TDI-tuning box was applied and I ran it on the middle setting for a tank, not altering my driving style. Brim results confirm 42.5mpg, although indicated mpg discrepancy increases. No actual increase in mpg at all. Top setting is savage on power and torque, but comes at some mpg cost and more frequent regens.
The only thing these boxes seem to do for mpg (in my case at least) is increase the MFD calculated mpg because the box is altering the signal that the ECU sends out to the common rail to calculate mpg. The car ends up using more fuel at any given throttle opening than it thinks it is, due to the modified signal which is invisible to the ECU and MFD, if you use less throttle (with the box) to achieve the same cruising speed etc then the car will be thinking it is using less fuel and put up higher mpg readings.
The only gains I could see really happening are those down to increased torque allowing you to be in a higher gear than you otherwise would be, so we’re talking those who cruise at a speed that would generally be in a lower gear than you are actually using, maybe in the 30-40mph range rather than full motorway/highway speeds whereby you would always be cruising in top gear. Would that really add up to 10% for most drivers? Unless the box manages to provide a better injection cycle/spray pattern etc than standard (which it doesn’t claim to), I can’t see the car getting appreciably more efficient at burning fuel.
Are all these gains people are seeing down to actual (brim method) or indicated MFD figures?
I would say, based on my own experiences that torque and output are well up – buy the unit for that rather than false high MFD indicated mpg gains.
