Project EconoPolo (aeromodding a VW)

[viio]

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.

[Vekke]

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

[viio]

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.

[COcyclist]

Originally Posted by viio

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.

[viio]

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!



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.



I've just completed CFD work on some test side sills - which I've posted here:
CFD modelling results on side skirts/sills

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

[viio]

Mudflaps are off! (based on CFD testing)

Mudflap delete modelled in CFD

[NachtRitter]

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

[viio]

Originally Posted by COcyclist

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.

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:



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



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



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:

[viio]

Originally Posted by NachtRitter

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

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.

[aerohead]

Originally Posted by viio

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:



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



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



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:

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.