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Old 03-21-2011, 10:06 PM   #1
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Reprogramming car computer to improve fuel efficiency

My friend told me that he took his VW Passat to a racing shop and had the computer setting changed to make the car more fuel efficient. He said that all cars come with factory settings that allow them to be shipped to countries that have less refined fuel. So, cars that go to places that have high quality fuel have programmed settings that allow for less fuel efficiency. Is this true?

If it is true, what kind of shop (more specific than "racing") would I take my car to and what would I ask the people to do to it?

Right now I have a Prius but besides the amazing MPG, I dont like it. So, I am considering getting a different car IF I can get it modified to have better fuel efficiency.

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Old 03-22-2011, 12:13 AM   #2
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Re: Reprogramming car computer to improve fuel efficiency

Post in the appropriate forum here based on the car you want and they will be able to point you to shops or individuals who do that kind of programming.

Vehicles are tuned with a fuel curve that has to suit many parameters - the most important one being emissions. The second most important one is warranty repair. Modern tuning (including higher compression ratios these days) often use slightly richer mixtures to reduce NOx emissions and prevent detonation. Some cars can benefit from leaning out the fuel curve a bit but whether or not it will improve MPG is anyone's guess.

MPG is mostly determined by your right foot. Without physically changing the engine's properties, it takes X amount of fuel to make X amount of power, so if you change the power by altering the fuel curve, you will likely end up using more right foot to get the same driving style you had before and negate any MPG increases.

Those modifications to the computer very rarely increase MPG, they are usually part of a performance tune. I have done it several times on my car. I was hacking in to change the computer for different gears so I used a leaner/performance tuning on my car. All it got me was 10 hp and the need for premium fuel

If you are truly seeking MPG, there are many vehicles that will meet or beat the Prius without tuning.
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Last edited by curtis73; 03-22-2011 at 03:24 AM.
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