What to improve in VW Golf Mk4?

[JSH]

Originally Posted by jorgemiguel4

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.

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.



There are aftermarket metal plates too

[Piotrsko]

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

[JSH]

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.

[jorgemiguel4]

Originally Posted by oil pan 4

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.

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.

[jorgemiguel4]

Originally Posted by JSH

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.



There are aftermarket metal plates too

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

[jorgemiguel4]

Originally Posted by freebeard

Box cavity.

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/forum/po...uote&p=1911182
Maybe without the extra width but with rear fender skirts?

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.

[jorgemiguel4]

Originally Posted by cRiPpLe_rOoStEr

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.

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

[freebeard]

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.

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.



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.

[cRiPpLe_rOoStEr]

Originally Posted by jorgemiguel4

Original filter already have a thermostat, it maintains the fuel at about 50ºC.

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.

And I believe it heats further inside the injector body.

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

[jorgemiguel4]

Originally Posted by freebeard

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.



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.

Nice car you have

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