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Old 06-22-2009, 07:49 PM   #1 (permalink)
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Join Date: Jan 2008
Location: Mirabel, QC
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The Guzzler - '08 Hyundai Elantra GL
90 day: 33.12 mpg (US)

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Tas's 2000 Jetta TDI Build Thread

Ok, I haven't done much yet, but I just want to document what I've done and talk about what I want to do before before I "race" in the AMEC Fuel Economy Run III which I will get to attend this year.

Some of you might remember my previous car, which I was able to push to 79.9 MPG over 1000 km in two days.

So now that I got the following model year, I had to mod it so I can eventually beat my record.

Thanks to the VGT turbo, fuel economy at highway speeds is better even if the frontal area of the car is a bit bigger. The Cd is supposed to be the same.

So, here are's a gimped pic of what I wanted to do aerowise.

But first, I have to talk about the car a bit. I got this car with 200k miles for $3500 CAD last december, which you know is cheap if you are into TDIs. This car had a brand new head and turbo, but it was still a dog off the line and it had a check engine code, and the owner was tired of spending cash on it, hence the price.

So I checked the code and it was an overboost condition which I traced to the a check valve in the vac line to the turbo vacuum actuator, which was backwards on the wrong line, causing the vanes to never move and stay put in max boost condition. So I flipped the valve around on the right vac line and problem solved. But the car was still a dog. The problem was eventually traced to the injector nozzles which were extremely dirty, clogged and not spraying right. So I replaced the stock 0.184 um nozzles with a set of 0.216 um I had bought for my previous car but never got to actually install.

Those nozzles are usually quite a good power upgrade, flowing roughly 37% more fuel than stock nozzles. I thought that since they would allow the end of injection to be closer to TDC, I could get better fuel economy. But that was not counting smaller nozzles atomize fuel better. So at low loads it is a wash at best, and I might very well be penalized over smaller nozzles. But at higher loads I believe larger nozzles are serving me well, especially when pulsing and gliding. My best tank so far was done with P&G 3/4 of the time at speeds varying between 80 and 55 mph. I also tuned the EGR on my car so it is increased at low loads. Not only does it warm up faster, but I believe it increases FE at low loads.

Aerowise here is what I have done so far.

I started by adding a lower grille block and wheel deflectors made of 1/8" abs plastic.

Those are really close to the ground and rubbing at the slightest bump, but they seem to divert the airflow around the wheels and tires quite wheel. You can also see the lower grill block on that pic, although it's taped while the silicone sets.

Next were the mirrors. My driver side mirror base was broken, the cheap white alloy inside had vanished and what was left of it was shattered, and the glass was completely blurred. Since a new mirror on a vw is not cheap, and lets be frank, I had an excuse to buy something else, I decided to get DTM cup style mirrors from ebay UK. Both mirrors with adapter plates cost me less than just an OEM driver side mirror. I only installed the driver side mirror, with a smaller frontal area than stock, and decided to use the adapter plate on the passenger side to make a block off plate.

There's a depression in the adapter plate to accept the cup mirror which I just taped on the passenger side, but eventually I'll cut a piece of abs that cleanly fits the hole.

As far as future mods go, I need to get a belly pan in there, especially considering even the stock belly pan was gone when I got the car. So there's room for improvement there. I also have blocks made for the lower side grilles I need to install. The top grille will also be sealed. Before the fuel economy run I will also get side skirts, rear wheel skirts, and I'm working on a plexiglass kammback.

__________________ - Quand chaque goutte compte...

Last edited by tasdrouille; 06-22-2009 at 08:28 PM..
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