What to improve in VW Golf Mk4?
 

Currently I'm achieving around 4L/100km(59MPG) at 90km/h(55mph).

Is there any way to improve this with stealth aero mods?

with stealth
 

No.

I was thinking in grill blocks, underbody smoothing with flat panels, airdam,..
Isn't it effective in this kind of car?

this kind
 

Volkswagen wrote the book on aerodynamic detail optimization,beginning in the mid-1970s.It's extremely unlikely that you could improve on what they've already done,short of spending $100,000 US in a full-scale wind tunnel,doing tweaks.And none of that would really show in fuel economy.
That said,you could do some things that would really make a difference,but none of it would be stealthly.All the mods would be immediately obvious to the most casual of viewers.
Lower drag is about the 'look.'
From where you're starting from,all the low-hanging fruit is already picked.

Ok, I didn't knew it was already that optimized. I used to think that my Golf was a brick with wheels.

What you think about using using CFD analysis to try some tiny bits and see how effective they are?

I already have a model of my car that I could use for that, but need some ideas to start.

https://imagizer.imageshack.com/img921/6470/VXNWxG.png

CFD
 

All you need to do is build that blue area behind the GOLF,along with rear wheel skirts and you're done.It's pre-engineered.It's been a fact since 1922.

Thanks, so nothing I can do. I can't make it road legal here in Portugal that way.

can do
 

Are you allowed to attach a cargo rack to the back of a vehicle? If so,perhaps it could be streamlined and at least you'd get 610mm additional length.You'd see a difference at the gas pump with that for highway driving.

aerohead's trolling you. I completely support that, it's not personal. Just that the answer has dependencies. Like local regulation. And what is exactly stealth.

Who defines stealth? As they say you can not see what you do not know.

Stance and plasma actuators* might do a lot. VW engineered to a general use case. Your example might be re-optimized for a more specific case.

Countershaded camouflage*?
Nothing worth doing is easy. Boxed cavity*?
This is of interest to me, but I'm just following developments. Those are VDB* and Blender 2.8*.

*Details on request.

Mk4 like the 1.8L turbo motor?

I think I'm allowed to attach that but it's not an option for me. It would be a problem to find a place to park.

Stealth for me are airdams, small deflectors, underbody panels. spoilers.

The local regulations here are pretty rigid , I can't lower the suspension for example.

Mine is a diesel, 1.9TDI 81kw

Larger intake piping may help.
I drove a 2004 1.9l jetta for a little while that had some funky small squareish intake piping that looked like a restriction.

Box cavity.
https://ecomodder.com/forum/member-f...31-1-26-08.png
The variations are stepped or angled, and the trick is to not block the tail lights.

edit:
Would this (Rocket Bunny-style) pass regulation?
https://www.thesamba.com/vw/gallery/pix/318725.jpg
https://www.thesamba.com/vw/forum/po...uote&p=1911182
Maybe without the extra width but with rear fender skirts?

More on the plasma actuators please...

This does indeed look interesting:

https://youtu.be/DUzHF17UC2g

https://youtu.be/GZWiysLd6jUThis video smells more like BS.

But... if i know how to fabricate the actuator, the voltages and the app could be a pleasant weekend project for me.


How did we attach youtube videos. I have done it in the past but have forgotten mow

Plasma Stream Technologies- 720P
I see what you mean. The first is raw data collection, the second shows the avenue out of super-secret aircrafts.

Attach vs embed: Copy and paste the URL and it displays as //youtube/ (you don't even have to wrap it in a Link tag, it's added atomagically), click on the video and Copy URL or copy URL At Present Time and it displays as //youtu.be/.
https://www.youtube.com/watch?v=GZWiysLd6jU
https://duckduckgo.com/?q=phys.org+plasma+actuator

The first result is Phys.org (https://phys.org/tags/plasma%20actuators/) but there are other research results (www.researchgate.net, iopscience.iop.org) on the first page.

edit: There is also this: A Magic To Improve Aerodynamics : TOYOTA PATENT

Pre-heating the fuel (not to the point of vaporising it) might be interesting. It's been widely used in those vegetable oil conversion kits, because they're harder to vaporise while injected at ambient temperatures. Better vaporising may lead to a more complete combustion. Other approach that might be useful is water injection, eventually also using the residual water taken out of the interior by the air conditioner.

I had a 2003 Jetta Wagon TDI that is the same body style. The TDI had an plastic underbody tray to closed off the bottom of the engine bay to pass USA noise standards. If you don't have one already it should be an easy bolt on modification.

http://thumb3.zeppy.io/d/l400/pict/2...w-high-quality

There are aftermarket metal plates too

https://cdn.shopify.com/s/files/1/25...g?v=1527375431

can't get panzer plates anymore, but can off & on get the metal ones as a replacement for that thing they use now.

My plastic tray lasted the 10 years / 240K miles I owned it. However, plenty of used cars are missing the tray because the owner takes it off to change the oil and then never puts it back on.

Actually intake manifold is quite ok for this engine.

I think that to get better I need to improve aero since I can squeeze 3.5l/100km(67MPG US) if I slow down a bit to 65km/h instead of 90~100Km/h. Road speed is what affects me the most.

I have one like that, it's still in good shape.

I'm looking to more discrete things. Spats, dams, smooth underbody,... but need some ideas if possible from more experienced people. Don't know what to do first and how to do it right.

Original filter already have a thermostat, it maintains the fuel at about 50ºC. And I believe it heats further inside the injector body.

The Scirroco is extreme to cover the wheels and tires. A normal eyebrow trim tapers out at the bottom, but if it was no wider than necessary but extends downward and in, in a similar manner, it would be more effective.

The box cavity is certainly more discrete that a full boat tail and is can be almost as effective. Many people wouldn't even see it because as they say 'the eye cannot see what the mind does not know'. Excepting those darned novelty seekers. :)

There's only so much you can do to the visible parts, they didn't leave a lot of low-hanging fruit.

https://i.pinimg.com/originals/57/4d...b15def42bd.jpg

The parts not visible are the underside and the engine bay. You can make as much difference there as on the outside. Generally, a smooth underbody is better than an airdam, but much more work. Air curtains are one opportunity. For the engine bay a thermostatically operated radiator block or outlet vent reduces drag. Then you get into 4-into-2-into-1 anti-reverionary headers and on down the rabbit hole.

I won't drop names but there are extremely knowledgeable people here, I just repeat stuff I've heard. My VW is stock except for the stance.

But does it have some auxiliary heater to prevent the Diesel from jellying inside the tank in the winter? I'm aware it's not an uncommon feature in some European trucks and bus frames.


Not so likely, unless it had some electric heating element similar to the injectors of some Brazilian port-injection flexfuel cars.

Nice car you have :)

I will probably try to smooth the underbody first, with some cheap plastic sheets.

It's a direct injection diesel, so the half injector's body is inside the head. Since the flow inside the injector is very slow I believe it heats the fuel a little more to 60~70ºC maybe after the engine reach full working temperature.

Sorry, I failed to annotate that. It was from Pinterest (apparently— I snagged it from DDG Images). Here's mine:

https://ecomodder.com/forum/member-f...5-100-1036.jpg

Not so sure if that would lead to a consistent heating of the fuel. Otherwise, any pre-heating to allow a safe usage of vegetable oils throughout an entire run even after engine temperatures stabilized would become redundant. So I'd still consider pre-heating even using regular Diesel fuel.

Heated tanks and lines are pretty common on heavy duty diesels but most people in the USA with diesel cars or small trucks just use an anti-gelling additive in the winter.

This $10 bottle treats 320 gallons of fuel.

https://www.amazon.com/Howes-103060-...omotive&sr=1-4

In Brazil it was common to mix kerosene on Diesel fuel, with many gas stations formerly having a kerosene pump beside the Diesel pump. AFAIK now only some Petrobras stations still have it. Regarding heated tanks, IIRC some Scania bus frames imported from Sweden had it as an option, even though the locally-made ones didn't.

Hi,

If your are not stuck to aero mods you could use a tune , larger injectors, hammer mod to increase power and fuel economy (of course not at the same time ...increased power means increased fuel usage BUT if you drive like normal those mods will help fuel economy (other mods include gutting the muffler and cat) but if you get smog checked that may not fly.

A flat under car pan may help , side skirts that deflect air round the rear wheels may help too (large road tractor trailers find it helps)....

Welcome Jorge. I have done “stealthy” aerodynamic mods to my Golf TDI and improved my mpg and coasting distances significantly. From outside the car you would only see the deleted passenger side mirror (and the folded driver’s on the lightly traveled highway). I blocked the upper grill with black pipe insulation stuffed between the grill bars. There seems to be plenty of airflow through the bottom grill. I have a Panzer plate that starts a bumper to bumper belly pan. I installed Votex side skirts painted to body code and used plastic rain gutter halves for inner and outer side skirts like the Aerocivic. I deleted the muffler mostly to make the rear diffuser angle better. I used rain gutter to make strakes that line up with the rear spring perches to complete the rear diffuser. I have small spats ahead of the front and rear tires. Please check out my albums and fuel log for more details.

https://ecomodder.com/forum/member-c...n+install.html

VW did a pretty good job on the outside but the underside is a mess. My coasting distances are much, much better than before the underbody aero mods. Good luck with yours.

https://ecomodder.com/forum/member-c...4-img-0146.jpgAlso, I sealed up around the rear wheelwells with aluminum flashing.https://ecomodder.com/forum/member-c...5-img-0140.jpg

I'm sure the OP would get in trouble with such mods