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Now what have I done????
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Discussion Starter · #1 ·
With all of the attention these days on improving economy and reducing CO2 emmissions, here's a question - is there any data published anywhere that advises what the differences might be between driving with the top up or top down in the convertible?

I assume all manufacturers data is based on the roof up, (as would be the case for all manufacturers), but I would certianly be curious to discover if having the roof down (also with or without wind-deflector) makes any significant difference.

Ian
 

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I wondered that myself yesterday when driving (in the freezing cold, but hey, it was sunny!) with the top down...If anyone finds out let us know!
 

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Rocking the F57
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I guess the factor that needs to be considered is the drag increase on the vehicle....

At slower speeds the fuel ecomomy lost would not be so bad, as drag has a lesser role to play, however as speeds increase and drag becomes a more prominant factor, the margin between roof up and roof down will increase.

I've never seen it tested - I guess the scientists have too much fun in their cabrios to stop and take measurements ;)
 

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You've just been totalled
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Our Merc (okay different car) but thirstier with the roof down over distance than with the roof up. French motorways with roof up returns about 31-32, but with roof down about 29-30. At speeds less than about 40, there is no visible difference.
 

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Now what have I done????
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Discussion Starter · #5 ·
OK, have sent an email to BMW/MINI. If they reply, will publish here!

Ian
 

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clubMINI Master
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Our Merc (okay different car) but thirstier with the roof down over distance than with the roof up. French motorways with roof up returns about 31-32, but with roof down about 29-30. At speeds less than about 40, there is no visible difference.

I would agree with similar figures. I have both the cab and the hardtop and there is about a 100km difference in a full tank between them. Also the cab drinks like anything with the roof down on the highway.

I have the wind deflector and tbh I think that it drinks more because of it!

Just filled up today so will do some testing!
 

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Here in Portugal I almost always have the roof down as you will expect. I've converted this to UK currency and miles.
I get 10 miles for one UK pound. MINI One cabrio with Bluefin and Pipercross intake.
Or 10 miles from 1 litre.
 

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Now what have I done????
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Discussion Starter · #9 ·
Now they have replied (for what it's worth!):

"I am able to advise that although more drag is created by having the roof down on a MINI Convertible, this measurement is so minimal that it is not documented.

This therefore would suggest that the roof down would very slightly affect the fuel economy but that this effect would be negligible."

So now you know - driving with the top down is not going to trash the planet any quicker......:D
 

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Excellent news - I got the roof down today as we had a bit of sunshine (if you ignore the fact that it was about 5 degrees C outside!). I would've thought (not that I'm a physicist or anything) that fuel economy would be affected a bit less than 'negligible' but I guess not! :D
 

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clubMINI Master
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Excellent news - I got the roof down today as we had a bit of sunshine (if you ignore the fact that it was about 5 degrees C outside!). I would've thought (not that I'm a physicist or anything) that fuel economy would be affected a bit less than 'negligible' but I guess not! :D
I would have to agree......however I have noticed that a on a beaut day, roof down, music loud, no wind.....that I do tend to drive just a little more.....urm how do you say........positively! :biggrin:

That may have something to do with my increased fuel consumption!:aargh:
 

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Now what have I done????
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Discussion Starter · #12 ·
And a further clarification:

"There is a legal requirement we must adhere to when testing our vehicles fuel consumption, a law set by the EU to ensure all vehicles are tested equally. This ensures no manufacturer can provide fuel consumption figures that are false to the consumer, or tested in a certain way to achieve higher figures.

The fuel consumption is tested at certain speeds in a laboratory, on a fully run in vehicle that has covered 1200 miles. As these figures are recorded in a laboratory, roof down figures would be identical. If we were to test the vehicle for fuel consumption out on the open road with the roof down and publish the results, we would be breaking the regulations set by the EU. You are more than welcome to test drive a MINI Convertible at your local MINI Dealership, with the roof down, to determine what mpg figures you achieve with your driving style on roads familiar to you."

So there you have it!
 

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totalMINI punto com
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Roof up, Roof Down fuel consumption comparison conundrum

"There is a legal requirement we must adhere to when testing our vehicles fuel consumption, a law set by the EU to ensure all vehicles are tested equally. ...The fuel consumption is tested at certain speeds in a laboratory, on a fully run in vehicle that has covered 1200 miles. As these figures are recorded in a laboratory, roof down figures would be identical. ... You are more than welcome to test drive a MINI Convertible at your local MINI Dealership, with the roof down, to determine what mpg figures you achieve with your driving style on roads familiar to you."

So there you have it!
My mission: to test drive a convertible with 1200miles on it with the roof down.
Mission obstacle: no dealerships have convertibles to test drive now.

This issue could be unresolved for quite some time.... and so we wait....
Anybody want to do a little comarison driving for the good of MINI Kind?
 

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Now what have I done????
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Discussion Starter · #16 ·
For me, the most inetresting point is that the tests done in a lab means no wind resistance? In which case, they will NEVER be achievable under real-world conditions! Or do they have a big fan blowing air at the required speeds to complete the simulation???? :confused:

Good point Derepente makes about going to a dealer to test a cabrio - I will respond back accordingly!

Watch this space......;)

Ian
 
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