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Diesel Tuning and MPG Improvements revealed

31st March 2009 | Share:

With the current state of the world economy at the moment, everyone is looking to save the pennies where they can. One large cost of living that people are always looking to save on is fuel. The current cost of diesel is back up around the £1/litre mark and any savings that can be had would no doubt be very welcome.

Where does diesel tuning fit in?

Diesel tuning boxes can make a huge difference in fuel economy and should definately be considered when looking to save those extra few pounds. However, you need to first establish if you will be the type of driver who will be able to benefit from the increase in MPG.

It is a common misconception that those who drive economically will see the best MPG improvements with a diesel tuning box. And similarly those who have a heavy right foot will not see so much improvement in MPG. It is this common misconception that has led to many other sellers of tuning boxes to produce so called Eco units.

In reality this is actually the opposite to what actually happens. Diesel tuning boxes work by increasing the torque characteristics of the engine. This increase in torque obviously results in an increase in power. This in turn results in the driver being able to reach the same speeds in a shorter time, using less total revs to get to that speed and hence saving fuel. Also manouevers like overtaking can be achieved easier and often without the need for gear changes. All this results in a improvement in fuel economy.

However, as these benefits are seen due to the increase in torque, the people who will see the MPG improvements are those who USE the torque of the engine. So those pulling heavy loads, or with a heavier right foot or live in hilly surroundings etc. are the ones who benefit the most. Those drivers who are already very defensive will not be using the torque of the engine so will not see as much MPG improvement.

Diesel Tuning boxes are fantastic for MPG however it needs to be kept in context. There is little point in a defensive driver purchasing a diesel tuning box for the sole purpose of improving fuel economy. A diesel tuning box should be installed for the purpose of making the engine more efficient and therefore improving the enjoyability of the drive. Fuel improvements, while important, should always be considered as a very nice bonus rather than a requirement for performance of the box.

In our time of supplying these tuning boxes we have seen MPG improvements in excess of 20%, and also customers with almost 0% improvement in fuel economy. The level of improvement you get is dependent on so many different factors from engine condition to driving style to quality of fuel etc that it is impossible to predict.


26 Responses to “Diesel Tuning and MPG Improvements revealed”

  1. john elliot says:

    have had speedhawk fitted for severale weeks power is rather lively fuel consumption is in excess of 38% on my bmw 320d over a 2 week period

  2. John Roberts says:

    Have you been able to fit one yet to a citreon c4 Grand Picasso ?

  3. BHP Plus says:

    Hi John, if you want to email us the engine size and bhp of your Citroen C4 Grand Picasso at, we will be able to advise if there is a Speedhawk tuning box available for it.

  4. Tony says:

    I’m a driving instructor, running Pug 207 1.6 hdi (the 90 bhp unit).
    From your comments, I’d be unlikely to get any fuel improvements from my driving … but to would be interesting to see what happened with learners. If there is no improvement, I could always return it of course …

  5. Peter Clothier says:

    Hi, I have one of your Tuning boxes on a TDi 140 Golf. I started with it’s “fine tuning” notch in the middle which seemed to work well with about 10-14mpg improvement and a lot of power extra.

    I switched the fine tune down to “-30%”, and so far it seems to use more fuel and has the same power, or feels like it – is that right?

    The other question is I read somewhere that the in car mpg calculator will be inaccurate with a tuning box, and you therefore need to measure it tank to tank. Is that correct ?


  6. BHP Plus says:

    @Peter Clothier
    With our tuning boxes, it is all about finding the settings that make your engine the most efficient. If you edge down the tuning then you can be making your engine less efficient and therefore using more fuel.

    With the onboard MPG reading, this will no longer be accurate after the installation of a tuning box. Therefore you need to measure tank to tank.

  7. dragos says:

    I own a mazda 3 2.0 diesel sport 2007 model. I would appreciate if you could benefit from installing one of your tuning boxes.

  8. BHP Plus says:

    Thank you for your enquiry Dragos. If your car is the 143bhp model then we have the following box available. Please see link to discover how your car would benefit!

  9. Reg Worthington says:

    I have a 2006 facelift Honda Accord 2.2 cdti sport and will be using the car to tow a caravan from time to time. Will the tuning box be suitable for normal use ( non towing ) and towing. What wil be the pro’s and cons of fitting a tuning box? Do you have dyno readouts/graphs ?

  10. BHP Plus says:

    Hi Reg,
    Thank you for your comment, as you will be towing the tuning box will help you a lot with the extra torque, but even when you are not towing you will still benefit from an inprovement in power and trorque, on average 25-30%, our tuning boxes are suitable for any aspect of driving. The pro’s for our boxes are that they are fully tunable with 9 settings and also the ability to been tweaked more or less if need be via a simple email, they are also quick and easy to fit or remove by a small electrical plug. With a 28 day guarantee there really is no ‘con’.
    We don’t have readouts or graphs as all cars are different as are peoples driving styles so the benefits vary from box to box but from customer feedback we have always seen improvements.

  11. Keith Robertson says:

    Hi, I have a Seat Altea 1.9 tdi (bhp103) with a DSG gearbox. I see your statement that the Speedhawk Diesel Tuning Box works with automatics. Please confirm that this is also 100% suitable for DSG boxes. I find the current mapping to hold high gears (seems to change up as soon as it can, and then hold the high gears for a long time). Therefore in town the revs are often below 2,000 and this to my mind feels as if the car is pulling under load as opposed to free revving. What can I expect from a Speedhawk DTB, ( I am refering to when in DRIVE not SPORT although I would be interested to learn how that will likely run too. THX

  12. Keith Robertson says:

    Looking deeper at your site, it seems to me that the PD boxes appear to come with 4 mappings and no remote, is this the case and if so how come more money? As there is no remote, then how are the settings changed and why are there only 4 tunings?

  13. MH says:

    Hi there,

    I own a Golf V 1.9 TDI and have recently fitted a Speedhawk box. I have to say that there was an immediate difference in the pull of the vehicle, and it seems to be performing much better. My question is this: I live in a very hilly part of the country (Devon) and as such the car sometimes struggles up these hills. Would it be better for me to set the power increase to 30% and potentially use more fuel, or leave it at 0%, so using less power but with a saving on fuel?

    Sorry if this sounds a bit vague, but I hope you get what I’m asking!

  14. Matjaz says:

    I have Laguna Coupe (180hp 2.0l diesel).
    Do you think that tuning can help lowering the consumption and/or increase top speed. If yes, please describe expected gains?



  15. BHP Plus says:

    Hi Matajz,

    It should certainly show some gains in economy, it also may well add an extra couple of MPH to the top speed, to give you exact gains on economy is imposible as it depends on where and how the vehicle is driven.

  16. BHP Plus says:

    Hi MH,

    The theory is infact the opposite of that, the more power you have means that the vehicle doesn’t have to labour quite so hard, meaning that it should pull more effciently up hills with less revs therefore using less fuel, rather than having to rev it quite hard to get it to go up the hill, if you then however use the extra power to drive everywhere faster then you will use more fuel.

  17. BHP Plus says:

    Hi Keith,

    The PD box was designed for a group of 4 engines that work in a completely different fashion to the common rail box that you are referring to, because it uses different hardware to achive its results it only needs the 4 programs to gain the same results, it also has an adjustment of plus and minus 30% going in steps of 10% so has 7 different settings of fine tuning as a result, this is effectively what the 9 settings do on the common rail tuning box, because of the hardware involved this also relates to the increase in price as they are more costly to produce.

  18. I have a Citroen Grand Picasso (110bhp) can this motor be remapped and at what cost, regards,
    Nigel Mitchell

  19. john says:

    i have a mk4 mondeo 20lt tdci 140 i am a taxi driver would one of these boxes work for me

  20. Craig says:

    I got vauxhall zafira 120 bhp so it will save fuel cos i drivin 100 miles a day ????

  21. BHP Plus says:

    In short yes, as you do so many miles it would reduce fuel consumption. However this is down to your driving, if you drive economically it will further reduce your fuel consumption.

  22. Ray Jelley says:

    Hi, I have a 2005 audi allroad 2.5tdi 180bhp and use it frequently for towing my caravan, would the fitting of a tuning box improve the economy of my car when towing?

  23. BHP Plus says:

    It will give you the ability to have greater economy yes but this is down to your driving style, if you drive hard it will use more fuel but if you drive eco you can significantly improve your economy. We get very good reviews about increased economy from people towing caravans and trailers.

  24. gurshinder says:

    Hi, i have skoda octavia 1.9 PD AT should i go for some tunning box,are they safe for the engine or i stick to my original setting.

  25. Brian Paterson says:

    Hi Do you do a box specifically tailored for a 2013 Kia Pro-Ceed CRDi 126 bhp engine?


  26. Mr Nicoloau says:

    I have a 2007 E320 CDI Mercedes and have fitted a tune it box. I have seen a slight improvement but reading about the brabus Speedhawk, is this a better box for performance & fuel economy?

    I would appreciate your advice.


    Mr Nicolaou

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