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Translucidus Profile
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X-TRAIL LEGEND
 


Date Registered: 05-2010
Location: Adelaide
TOTAL POSTS: 599
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Wind Deflector on Car for towing a Caravan etc


I've just purchased one of these second hand for $150.

Please read my questions and comments after the videos.

Image

Here is a video of it:



Video without a deflector:


Video with air deflection (not a wind deflector but you'll get the idea)


I've also bought a set of ProRack roof racks to mount it on.

My question is whether anyone here has used something like this to reduce drag, decrease fuel consumption etc.

(Various forums report 2-3 less Litres/100kms and less buffeting from passing Trucks etc.)

Also I'm wondering if the X-Trail's roof rack mounting plates are strong enough for the wind forces that will tend to twist the roof rack and pull it rearwards.

I'm thinking of using the two roof racks and running 2 one inch square tubes between them to reinforce the rear one against the twisting loads.

Any comments?

Last edited by Translucidus, 16/Feb/2015, 3:18 pm


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2007 X-Trail T31 ST-L

Xy going vertical at Bendleby Station . . .

16/Feb/2015, 2:34 pm Link to this post Send Email PM   Send Private Message
 
tj81 Profile
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X-TRAIL NEWBIE
 


Date Registered: 05-2014
TOTAL POSTS: 55
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Re:


2-3 Litres per hundred less in fuel consumption hardly seems worth the effort.

Ive yet to tow my caravan with the X-trail, as im just finishing off the brake controller, but from all reports i should get around 10l per hundred, in my Diesel, which will be awesome.


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Member # X-3683

T31 Xtrail, 4wd TS, 2.0 Diesel Manual. Tempest Blue
Lightforce 170 HID, Nudge Bar
Geelong VIC
16/Feb/2015, 5:27 pm Link to this post Send Email PM   Send Private Message Blog
 
DogTrail Profile
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X-TRAIL FANATIC
 


Date Registered: 05-2012
Location: Sunshine Coast
TOTAL POSTS: 481
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Re: Wind Deflector on Car for towing a Caravan etc


quote:

My question is whether anyone here has used something like this to reduce drag, decrease fuel consumption etc.



Yes. I suggested an airfoil should be fitted to my brother's campervan to reduce the drag engendered by his roof carrier.

He reckoned there was a significant fuel saving after it was fitted.

For ti81: Perhaps he/she has not traveled long distances where a fraction of a litre/100Km is significant over the journey?

Also, over 40,000 km I've averaged 8.3 L/100km in my petrol 2.5L so I'm not persuaded that 10 L/100 km is 'awesome' for a diesel.

Should that be hard to believe, all the figures are readily available on Spritmonitor.

Back to the point: The concept is sound.

Imagine a drive of 5000 Km. Saving that lowest estimate of 2L/100Km gives an overall saving of 100 L over that journey. At 3l/100 it is 150 litres saved.

At Outback prices, that could be $2-300.

Better in my pocket than in theirs.


It is only an air foil & the wind force is directional and stable and will tend to push the car down (for better traction) rather than twist and pull rearwards, so I wouldn't be fussed about that unless you intend to hit 140+ kph.

There will be a sweet point - at a guess, maybe around 90 kph.

I vaguely remember rule of thumb that it takes about 20% more fuel to run a car at 100 kph than at 80 kph and a further 20% on that, to run it at 120 kph.

The airfoil should slide the curve of the graph into your favour


Last edited by DogTrail, 18/Feb/2015, 4:45 am


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2011/12 Australia:- 2.5 litre petrol 4WD, Series IV ST, CVT : + some gadgets and cosmetic add-on's. Dirt, (it protects the paintwork) X-2429(c).
18/Feb/2015, 4:23 am Link to this post Send Email PM   Send Private Message
 
tj81 Profile
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X-TRAIL NEWBIE
 


Date Registered: 05-2014
TOTAL POSTS: 55
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Re:


Ive towed campers for years over many 10s of thousands of k's with my 4.2 Turbo Diesel Patrol, 10l per hundred sounds good to me.

Im talking towing here, not average consumption over the life of the vehicle, mine routinely gets 6.5 around town and lower on open road...if i get 10/ph towing my van, i will be very happy.

Last edited by tj81, 18/Feb/2015, 11:53 am


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Member # X-3683

T31 Xtrail, 4wd TS, 2.0 Diesel Manual. Tempest Blue
Lightforce 170 HID, Nudge Bar
Geelong VIC
18/Feb/2015, 9:19 am Link to this post Send Email PM   Send Private Message Blog
 
Translucidus Profile
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X-TRAIL LEGEND
 


Date Registered: 05-2010
Location: Adelaide
TOTAL POSTS: 599
Reply | QUOTE
Re: Wind Deflector on Car for towing a Caravan etc


I've just created Air Flow simulations.

First is for a T31 X-trail towing a caravan similar to mine:


Second is for the same setup Plus an Air Deflector on a rear roof rack:


It would seem the Air Deflector creates a better airflow with much less Turbulence between the Car and the Caravan

Last edited by Translucidus, 20/Feb/2015, 1:29 am


---
2007 X-Trail T31 ST-L

Xy going vertical at Bendleby Station . . .

20/Feb/2015, 1:12 am Link to this post Send Email PM   Send Private Message
 


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