50 mpg at 80 mph (project 2013 Golf TDI aero mods)
 

This is going to be my project thread. My goal is to average 50mpg at 80mph in my TDI Golf. I am currently averaging 47mpg at 70mph. This project will strictly be aerodynamic widgets to achieve this goal.

I will initially be starting with the current car in CAD. Running a cfd analysis on it and comparing to analytical data found on the car.

My goal will be to have all the aero widgets under the car so they cannot be seen :D

CAD: Solidworks 2013
CFD: OpenFOAM

Current CAD Model:
http://i1291.photobucket.com/albums/...ps8694fd21.jpg

The CAD model still needs wheels modeled and such but it is close. I have access to a 3d scanner and a 3d printer. All widgets will be 3d printed and tested before actual parts will be made :D

mighty impressive !

Check out member Vekke's work with his VW. 50 at 80 is a tall order but good luck trying!

regards
Mech

If you are willing to add an aero widget that can be seen (a boattail), you could raise your goal even higher. The Aerocivic gets lower 60's mpg at 80mph.

50 at 80 is a tall order when restricted to "hidden" aero mods, but should be fun trying for it.

I've been waiting for someone to take this approach. This will be the best route to sharing mods in the future.

Watching with interest!

i know you are only talking aero at this point, but i would love to see 80mpg at 50 mph. i wonder which you would get to first?

Did anyone fancy evaluating this statement with the appropriate tool ?
I threw some numbers at it and found out the following is required to hit 50mpg @ 80 mph
Vehicle weight [1]: 1200 Kg
Crr - Coefficient of rolling resistance [2]: .008
Cd - Coefficient of drag [3]: 0.30
A - frontal area [4]: 2 sq meters
CdA 0.60 m2 / 6.46 ft2
Fuel energy density (Wh/US gal.) [5]: - or -
Engine efficiency [6]: 0.35
Drivetrain efficiency: 0.95

One should try with the actual frontal area of the Golf.

What's the required Cd bump ?

AFAIK the European 1.6 L TDi version will do close to that target ...

Do modern engines have that high efficiencies at medium load ?

widgets
 

VW has already optimized everything you see on the Golf.I'm pretty certain that the car's visible ' look' will have to change in order to achieve your goal.

Important question : how do you measure your average mpg and average distance and above all, on which distance ?
Or is it purely academic Cd boost and relevant mpg estimated through this site tool ?

This is not true

Purely academic with Cd as the means of improvement. I will test when I drive on the interstate for 100 miles. No way to really test on the street accurately since the conditions change so much.

cfd, I wish you luck on achieving your goal with your VW. I am working toward my personal goal of 70@70 but I am not there yet. I have done some extensive stealthy mods but I think I am about at my max unless I do more visible mods such as fender skirts and a boat tail. I have a full belly pan, inner and outer side skirts and a homemade diffuser underneath. I am closing in on 60 mpg but at about 60 mph.

Also, my wife's 2011 A3 TDI with DSG does not get as good mpg as my older TDI with the 5 speed manual transmission. I will be eager to see your mods. Good luck.

Thanks for your post. Most of my work will be the diffuser and bits to feed the diffuser with more air. I feel like that will be the biggest gain.

Aerodynamic drag caused by cooling package and rear axle alone is HUGE on these cars.
I have a Skoda clone of this Golf and grill block + rear axle coved made really big difference in aero drag.

I have 2.0 16V PD engine and currently achieve 60MPG at 68MPH indicated.
Good luck with your goal and I will definitely follow this thread :)

I am eager to follow progress. Thanks for sharing. This should be enlightening.

Sam

I forgot to mention that I have the upper grill blocked year round, the lower grill partially blocked depending on outside temperatures and the lower left grill flush covered. These diesels run pretty cool, especially when hypermiling so you don't need as much grill opening.

true
 

Okay,you're the boss of this one,so I'll wait for your images.
Just bear in mind that Volkswagen 'invented' aerodynamic optimization in the 1970s.
I'm just having difficulty imagining things which will 'show' aerodynamically,which don't 'show' visually.:)

some 'rough' numbers
 

I messed around on the calculator to get a rough feel for the Golf.
Loose Specifications:
*Cd 0.30
*Projected frontal area 20.7 sq-ft
*Curb weight 2,800 pounds
*Coefficient of rolling force 0.015
*47 mpg at a steady 70 mph
*1.4893 gallons/hour
*10.173 pounds diesel/hour
*Aerodynamic Road Load @ 70 mph 77.882 pounds/14.539 hp
*Friction and tire losses @ 70 mph 7.84 hp
*Total Road Load @ 70 mph 22.379 hp
*Required engine power @ 70 mph 24.325 bhp
*BSFC 0.4182 lbs/bhp-hr
--------------------------------------------------------------------------
If I leave the car alone,but increase the velocity to 80 mph the engine power requirement rises to 33.328 bhp.
*Rolling resistance tractive power is up to 8.96 hp.
--------------------------------------------------------------------------
To achieve 50 mpg @ 80 mph requires:
*1.6 gallons/hour
*10.9286 pounds/hour
*dividing by BSFC = 26.133 bhp
*= 24.042 hp
*minus 8.96 hp rolling resistance leaves 15.082 hp for aerodynamic drag.
*Solving for the Cd using the standard aerodynamic power equation yields Cd 0.208 necessary to produce 50 mpg @ 80 mph.
-------------------------------------------------------------------------
*Cd 0.208 is 30.5% lower than Cd 0.30.
*A 'typical' belly pan would yield about a 12% drag reduction and 7.2% mpg improvement @ 70 mph.
*Even the 1982 Audi 100 III with Cd 0.30 yielded only Cd 0.23 with a full belly pan with diffuser.
*The Golf has a smoother underside than the 1982 Audi to begin with and the best underside would yield less of an improvement than what Buchheim et. al. achieved with the Audi after $1.5 million in wind tunnel time (1982-Dollars).

Finished my initial test model. I am going to clean up the model a little and get it ready for cfd. I will post data when I finish the the initial run :turtle:

http://i1291.photobucket.com/albums/...psaa5fa056.jpg

Since I have basicly the same car, hope I can share my underbody modifications here. I'm not trying to hijack thread or anything :)

I raised stock engine cover about 3cm (less frontal area and more air going under the car), removed central portion of stock "airdam", covered whole exhaust and rear axle and created something that resembles a diffuser.

For those wondering what car it is, it's a Skoda Octavia AKA Jetta Station Wagon with slightly different body :)

EDIT: I attached two pictures with my reply but I can't see them in the post.
Could someone help me with this, please?

Just sold my 2003 JSW and bought a 2012 Jetta.
The 2012 Jetta is larger than a friends 2004 Passat.
Your wife's 2011 is much larger than your MKIV.

Are the pictures in a Ecomodder album, other online source or on your hard drive? Do the pictures appear in a Preview of the post? It should look like this, unobfuscated:

[I*M*G]http://i1291.photobucket.com/albums/b551/paul-hanchagroup/initial_assembly_zpsaa5fa056.jpg[/I*M*G]

—using cfd_guy's example.

wait with interest.

Actually they are pretty similar. The A3 is the baby Audi here in the States. I took a tape measure to them both in the garage the other night and they are essentially the same width. The Audi is 2" lower roof height so less frontal area. The Audi is slightly longer but has better plan taper than the Golf.

I believe the biggest difference is the particulate filter/regeneration and increased use of EGR on the Audi affecting the mileage.

Good luck! I like to see what these TDI's are capable of, but for my part I'll just keep my speed down. I've seen averages around 60 mpg at 60 mph.

So sorry, my mistake.
I was comparing mkiv jetta to mkvi jetta.
Completely missed that out was a3.

Anyone willing to share pictures of their diffusers ?

With a Malone stage 2, dpf delete and intake flappers delete I'm hearing of 6-9mpg increases......of course not on USA/EPA regulated roads ;)