Project EconoPolo (aeromodding a VW)
 

Hi folks,

I've been driving a Subaru Impreza WRX STI for a while now, and I've just bought an economical car for doing most of my daily driving. I plan to do a fair bit of eco-modding with the goal of making improvements to the economy without making the car look "ghetto". I'm pretty sure my wife will refuse to drive it if I cover the car in coroplast!

It's the 1.4 TDI (3 cylinder turbo diesel, 6 valves). 1258kg according to the manufacturer, and I hope to get it beyond the 61.8 mpg advertised.

Anyway, here are the cars at the moment, and mods are underway!

http://i4.photobucket.com/albums/y14...er/th_ebay.jpg http://i4.photobucket.com/albums/y14...dewaysabit.png http://i4.photobucket.com/albums/y14...h_IMG_1054.jpg

I'm using SolidWorks and it's FlowSimulation tools to build a 3d model of the polo so I can test out aerodynamic theory and cut down on drag before I get out the duct tape and glue.

Here's a sample of the model as it stands right now. Lots of work to be done and lots of testing.

http://i4.photobucket.com/albums/y14..._v_default.jpg

Today I completed blocks to both side of the lower grilles on the Polo. The one on the left needs to remain open as it supplies air to the intercooler, so I've actually cut that open a bit more. But now both sides are blocked, photos below:

http://i4.photobucket.com/albums/y14...h_IMAG0664.jpg http://i4.photobucket.com/albums/y14...h_IMAG0663.jpg

Nice! Welcome to EM. Check out what Vekke has done to his Lupo. Since yours is a diesel you will find you need very little grill opening as these cars do not generate as much waste heat as a petrol car. I block the upper grill on my Golf year round with black foam "pipe insulation" stuffed between the grill bars and part of the lower middle one too in winter. Speeds warmup times and helps reduce aerodynamic drag through the cooling system. I have done a full belly pan and a passenger side mirror delete but otherwise my car appears pretty stock on the outside. Check out photos in my albums on this site.

Aerocivic
 

you could skip all the theory and copy the AEROVIVIC.Copy everything!

Nice side-grill blocks... Mine are not quite so fancy, but accomplish something similar... I had to leave a hole on the driver side so I could access the bolt that holds the bumper cover on ... as you can see, I cover nearly everything (upper and middle); only the lowest lip is still open (black part of the bumper) ...

https://lh5.googleusercontent.com/-i...llBlocks-2.jpg

BTW - How did you attach your driver side block?

As much as I admire the design, I find the execution a bit... umm... rough. Anyways I like the theory :)

All the blocks are attached using this plain old superglue, cut to shape and then glued into the hole.
http://i4.photobucket.com/albums/y14..._IMG_10901.jpg

So do you not have any airflow onto the intercooler then?

On regular driving you dont need any cooling air to the intercooler. If you drive over 120 km/h in hot summer days then the intercooler is actually needed. On winter conditions it should be also blocked on the front side or even take it fully out.

Also you can block all the cooling holes in the bumber if the temperatures are under +5 celsius. or if you drive under 100 km/h in summer. On the hottest day you need to make small holes or take the upper block off.

Smooth underside is a also a nice mod.

http://www.youtube.com/watch?v=fySDCXrY0e4

For tires I recommend to front 175/80R14 Continental ecocontant3
And to rear 165/70R14. This setup need 30 mm lowering kit to front or 60/30mm.. These tires and lowering alone will reduce fuel consumption about 10% ;). Check out my lupo thread and Seat cordoba vario threads for more info.

Oh and welcome.

edit: Oh and remember to take out the rear muffler. It should help a lot.

Nice car! It looks pretty slick to start with.

In fact, I do leave an opening on driver's side for the intercooler (where it is not pink, it is open :p ). But watching the intake temperatures using the Scangauge II, I would agree with Vekke... the area could probably be blocked completely in winter.

So yesterday I went through a few stages of grille blocks.

First off I made a top grille block by gluing glossed rubber to the back:
http://i4.photobucket.com/albums/y14...h_IMG_1072.jpg http://i4.photobucket.com/albums/y14...h_IMG_1071.jpg

However after seeing some other blocks, I did a little bit of CFD and discovered that the blocked version still created turbulence and drag. So I decided to go for a full on cut to size and smoothed in version.

http://i4.photobucket.com/albums/y14...h_IMG_1092.jpg http://i4.photobucket.com/albums/y14...h_IMG_1093.jpg http://i4.photobucket.com/albums/y14...h_IMG_1094.jpg

By the way this material is actually armoured mudflap rubber which I bought for my Subaru and didn't fit ;)

http://i4.photobucket.com/albums/y14...h_IMG_1095.jpg

http://i4.photobucket.com/albums/y14...h_IMG_1097.jpg


I knew I'd be ecomodding this car, and now I'm REALLY glad I decided to get it in black!

Here's a shot of the CFD from the first blocked (but not smoothed) grille.

All the twisty turbulent red velocity lines are bad, even if it's only on a small area I'd rather not have my grille creating drag.

http://i4.photobucket.com/albums/y14...lleblockv1.jpg

That really looks nice with the smooth lines of the Polo. I take it the Polo doesn't have the engine air intake at the top slat of the grill like my Golf does? (I left one side of the top grill bar open for that reason.)

I did this on the diesel Golf and replaced it with a straight pipe. I don't have any test data to show if it helped horsepower or mpg but it didn't hurt any. The noise level in the cabin is virtually unchanged. With the turbo and the cat dampening the exhaust pulses it is not loud.

It does, but I've removed the cold air feed so the airbox takes air straight from the engine bay. It'll help the car warm up faster on short journeys and I'm not bothered about slight power drop. Intake temp monitor reads about 15c, so about 10 degrees above ambient.

Upper block looks very nice! Great job!

The flush grille block looks completely stock ( and in my opinion, even better than stock.)

Thank-you for that. That's what I was hoping for! I took some inspiration from the Bluemotion and decided to just block the whole thing in gloss black.

http://upload.wikimedia.org/wikipedi...11-08-07_A.jpg

This may be the best looking grill block I've seen.

Block sure looks cool. If you want to make it perfect you need to take about 10mm out from the cars left side piece to make them symmetrical ;).

Yes when you take out the rear muffler you wont even notice it while driving.

When you say take out the rear muffler, do you just mean unbolting it and dropping it? I've heard of swapping to aftermarket parts but never just taking it off.

Take the old muffler out and replace it with straight pipe to back. If you plan to put it back use the braking point which is already there. If you dont need it just use hacksaw to cut it off just before the muffler begins so you will only need straight 1 meter pipe like I did on my seat:

https://skydrive.live.com/?cid=acb1f...3BAC776768!163

First two fill-ups have given me 55mpg and 58 mpg (UK) - both are short on the 61.8mpg combined that the factory suggests. I've been carrying a fair bit of weight around but as it's mostly long motorway journeys I'm surprised it isn't higher.

I wonder if I ought to reconnect my cold-air feed to see if the engine is starved of oxygen. I have a feeling I'm having to work the engine quite hard to get it to climb hills etc and the cold air feed might help with that.

Everything I have read and experienced about diesels says to supply the engine intake with as much cool air as possible. Block the radiator because they are so efficient they don't generate much heat but I would keep the cold-air intake in place and free flowing. Warm-Air Intake mods may work in gas (petrol) vehicles because they are fighting against the throttle plate at low load situations. The warmer air is less dense and allows gas engines to run with the throttle a little more open and operate more efficiently at hypermiler cruising speeds. It hurts their power too but some people may get a few mpg out of it. Not for diesels though. Diesels don't have a throttle and can work at very lean injection rates.

Apologies for the absence, I've been moving house, job, and internet providers. I've made a few changes since I last posted.

Wheel "spats" are now in place for all 4 wheels - just a 5 inch piece of mudflap rubber in front of each wheel. Simple but the CFD work I did said they helped, so on they went!

http://i4.photobucket.com/albums/y14...h_IMG_1103.jpg http://i4.photobucket.com/albums/y14...IMG_1101-1.jpg http://i4.photobucket.com/albums/y14...h_IMG_1100.jpg

I managed to get hold of some very large sheets of acrylic thanks to my dad, so I got 4 of them and set to work to create underbody panelling (belly pan). I used two pieces (about 3 feet X 4 feet each) and cut them to shape to fit the suspension components. This stuff is pretty heat resistant so I didn't even need to cut a space for the exhaust.

http://i4.photobucket.com/albums/y14...sunderside.png http://i4.photobucket.com/albums/y14...h_IMG_1132.jpg

I've just completed CFD work on some test side sills - which I've posted here:
http://ecomodder.com/forum/showthrea...tml#post289002

and tomorrow I'll try to fabricate something.


In other news, I experimented with a very small rubber roof spoiler in CFD to see if I could promote "detaching" the air at the back of the car. This was a fail though, as the results on the right show more turbulence and drag (in red) at the back of the vehicle. Still - at least I didn't have to get the glue out and test it with A-B-A, I tested it from my desk :P

http://i4.photobucket.com/albums/y14...oofspoiler.png http://i4.photobucket.com/albums/y14...oofspoiler.png

Mudflaps are off! (based on CFD testing)

http://ecomodder.com/forum/showthrea...cfd-20690.html

I like the wheel spats... are they the width of the tire?

And with that in mind, I re-worked my cold air intake today. This was a bit tricky since I don't have an opening on the front grille any more so I had to get a little creative - or destructive actually.

The top of the grille is the only place to suck air in from now and unfortunately it looks like this:

http://i4.photobucket.com/albums/y14...h_IMAG0743.jpg

So I got trigger-happy with a jig-saw and opened it up.

http://i4.photobucket.com/albums/y14...h_IMAG0742.jpg

Now the air flows in through the VW badge (the badge was blocked behind but now it's an intake!

http://i4.photobucket.com/albums/y14...h_IMG_1095.jpg

Next step was to sort out the very restrictive cold-air feed which for some reason had a big plastic chunk blocking the flow of air. It also had an opening at the bottom about 15mm high and covered the full width of the intake section. In short, most of the air coming in the front would be directed out the bottom and didn't head towards the engine! WTF!

I've now cut out the restriction and taped the whole thing up so that the air can't leak, and the air pressure increases on the intake that goes to the engine. Here's the before and after. You can probably see the original gap from the height difference in the "after" pic below:

http://i4.photobucket.com/albums/y14...h_IMAG0738.jpg http://i4.photobucket.com/albums/y14...h_IMAG0741.jpg

No they're only 4-5 inches, I went for smaller ones as my CFD suggested I could get the air to divert around the wheels without having to go full width and impact my frontal area total.

VW badge
 

It would be instructive to do a small tuft test around the badge area.
On the 1st-gen Ford Taurus,air actually came out of the upper oval opening due to the accelerated flow in that vicinity.

Are you sure that those were acryl?
You can bend one corner with pliers to see if it will brake. Acryl wont work on underpalenels because they will get hit and they will brake if those were acryl.

I am using abs plastic on my smooth undertray.

Also you would want to check that your brakes arent dragging so lift each tire up and see how easy it is to rotate. On my seat cordoba rear wheels after adjusting the rear wheel bearings it would roll 20 seconds after it stopped. If wheel brakes are dragging it will roll just few seconds. When you get over ten seconds you are in proper range and there is no drag.

If your brakes rotors are twisted you can feel and most cases hear that also. That will slow you down.

Good call on the brake rotors - I think my front ones are warped/twisted as the brakes judder when used. I've just replaced the back ones, cos they were a bit uhhh.... spent. See below:
http://i4.photobucket.com/albums/y14...AG0669copy.png http://i4.photobucket.com/albums/y14...AG0668copy.png http://i4.photobucket.com/albums/y14...AG0674copy.png

It's breakable - but it needs a hell of a lot of force as it's 4mm thick. I would love to use ABS plastic but haven't found anywhere I can get it in the UK at a reasonable price.

I've had a productive weekend going crazy with silicon adhesive sealant. I looked for all the panel gaps on the car and smoothed them out where I could. Here are some of the nasty gaps which I was working with and how those gaps sealed up - some are awful grubby still (the car needs a good wash).

http://i4.photobucket.com/albums/y14...310_131322.jpg http://i4.photobucket.com/albums/y14...310_113718.jpg

http://i4.photobucket.com/albums/y14...310_132654.jpg http://i4.photobucket.com/albums/y14...310_113605.jpg

http://i4.photobucket.com/albums/y14...310_113905.jpg http://i4.photobucket.com/albums/y14...310_113849.jpg

http://i4.photobucket.com/albums/y14...310_112810.jpg http://i4.photobucket.com/albums/y14...310_113017.jpg

http://i4.photobucket.com/albums/y14...310_111809.jpg http://i4.photobucket.com/albums/y14...310_112607.jpg

Using the correct tools for the job:
http://i4.photobucket.com/albums/y14...311_173019.jpg

And some other bits I've sealed up, like the gap between the roof and the rear spoiler:
http://i4.photobucket.com/albums/y14...310_113836.jpg

Gap at the side of the bonnet/hood, using a length of rubber vacuum pipe to fill one side has actually shifted the bonnet slightly, thus closing the gap on the other side too!
http://i4.photobucket.com/albums/y14...311_181532.jpg http://i4.photobucket.com/albums/y14...311_181609.jpg

Even the wing mirrors got the treatment, for what its worth. These gaps are no longer there :)
http://i4.photobucket.com/albums/y14...310_114048.jpg

Have you any plans for the flow from the belly pan out under the bumper?

I'm not finished with the belly-pan yet I've just received an 8ft x 4ft abs plastic sheet so I'm gonna re-do the whole undertray. Do you mean at the rear of the car? If you mean a diffuser or anything then no I'm not planning anything like that, however I might fit a couple of side pieces to the back bumper like the Prius has:

http://i4.photobucket.com/albums/y14...r_20071025.jpg

That is... if my modelling in CFD proves it's a good idea for my car.

Yes, try to optimize flow top and bottom to minimize separation.

Just did a little Google reading on flow separation (as I didn't know what it was lol). It sounds like there would be a case for a rear tray that actually extends past the rear of the bumper at the bottom, does that sound right?

I've just finished a further section on my grille block on the front bumper. The engine is still running cool so I'm blocking more up to reduce drag.

http://i4.photobucket.com/albums/y14...311_172718.jpg

I used some adhesive sealant called Teroson Terostat to glue the new insert onto the front bumper slats, then duct taped it till it dried. Then a bit of hammerite black paint to disguise its presence!

http://i4.photobucket.com/albums/y14...311_181324.jpg

Yes, some of the newer Dodge Caravans have a lip molded into the rear bumper facia.

Look at smoothing the internal ducting to the radiator ala Hucho or Katz pictures.

I don't think there is any ducting, just a big space behind the grille there. Do you have a link I could go look through so I can understand what you mean?