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Old 09-03-2008, 03:51 AM   #11 (permalink)
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Hey Jake. Well done; that's quite the improvement. That generation of Accord looks like it has pretty good aerodynamics, I'll bet with a belly pan and your full grille block you could glide pretty far in between pulses.

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Old 09-24-2008, 08:53 PM   #12 (permalink)
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A belated welcome to the forum, Sayyad. Nice to have another aero enthusiast who isn't afraid of a little duct tape residue.
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Old 09-24-2008, 10:55 PM   #13 (permalink)
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Hi,

You know what take off the tape residue? Goof-Off solvent -- I got mine from Home Depot.

On the grill blocks, you may find that leaving some of the lower radiator grill open, and closing off the top opening completely works better for FE. Also, some foam gasket tape (with adhesive on one side, again from your local hardware store) might work very well to seal the hood gap at the front edge. I think this is a critical point, because the air pressure is highest on there.
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Old 09-24-2008, 11:51 PM   #14 (permalink)
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Thanks; I've been reading the threads on here since the site started; I just started posting once I figured I had something to contribute.
I used Goo Gone and my favorite solvent, Elbow Grease, to remove whatever residue remained.
My car needs a paint job. It looks like the whole car was painted with a spray can of silver and a paintbrush of clear coat. Parts of the car always look wet due to the runs in the topcoat hanging down below the lower edges of body panels. The rubber seals around the doors have, on average, 2mm of silver overspray on them. In short, pretty terrible. I don't respect my paint.
Still, be careful when removing duct tape from a cheaply painted plastic surface. I managed to peel little bits of top coat and paint off the bits of the front bumper that were obviously not sanded before being painted (no primer either, as I can now see). Perhaps I should have removed the tape sooner or warmed it up before peeling it off.
On my bumper a few more tiny chips aren't really noticeable beside the rest of the rock chips and paint flakes.
No paint was removed from any metal body panels, and all the remaining tape residue came off easily.
I consider duct tape to be a very useful tool for repairing, modifying or prototyping many things. It has its downsides but a lot of the time cardboard and duct tape are the quickest and easiest tools for simple jobs.
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Old 09-25-2008, 06:31 AM   #15 (permalink)
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Hiya,

I should've said that the wheel opening covers look functionally great -- they do not stick out any farther than the body, and they cover the critical areas where most of the drag around the wheel openings occur, I think.

Did you put them all on at once (front and back)? I'm contemplating using Coroplast on the front wheels, smiliarly to what you've done -- what do you estimate is the effect of the front mods?
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Old 09-25-2008, 07:33 PM   #16 (permalink)
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One benefit of the tape is that it has a really low profile. It doesn't add any protrusions to the surface of the car.
I was up late reading this site one night and I had found a big roll of duct tape earlier in the afternoon. I applied all the tape to the car within an hour or so in the garage with a flashlight at around 3AM, using a washcloth and a bucket of hot water to wipe any dust or dirt off the car that could have affected the tape's adhesion.
The front wheel skirts are complicated. Look at the third image from the first post in this thread. It shows the partial front wheel skirt. Notice the notch in the skirt's lower edge about halfway along it's length. That notch is from the front tire rubbing against the skirt when some set of conditions are present, perhaps accelerating around a turn while going over a bump.
So if you are going to install front wheel skirts you'll have to figure out the full range of motion of your front wheels to get the size just right, especially if you're using coroplast, which could easily melt. Or you could build a flexible skirt which would work better anyway.
I only know how much of an improvement there seemed to be with all the duct tape on at once. Reducing airflow in and around the wheel wells is always a good thing, so go for it anyway and if you do just the front ones please tell us your results.
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Old 09-25-2008, 10:36 PM   #17 (permalink)
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Quote:
Originally Posted by Sayyad View Post
The front wheel skirts are complicated. Look at the third image from the first post in this thread. It shows the partial front wheel skirt. Notice the notch in the skirt's lower edge about halfway along it's length. That notch is from the front tire rubbing against the skirt when some set of conditions are present, perhaps accelerating around a turn while going over a bump.
So if you are going to install front wheel skirts you'll have to figure out the full range of motion of your front wheels to get the size just right, especially if you're using coroplast, which could easily melt. Or you could build a flexible skirt which would work better anyway.
I had to replace one of my inner fender skirts in August, and there are a few mounting screws on the Jetta fenders along the edge that could be used to hold brackets that secure a more permanent skirt.

Back on the GasSavers forums, there was a fellow that made a full rubber and Coroplast front skirt. With the mounting points available, I'm thinking that a gap-filling partial skirt for Jettas that covers the top and front edges is feasable.

If only that one portion contacts and wears in the center, then it seems likely to me that coroplast + rubber edged top, or top and front skirt would work. After prototyping, to figure out the right shape to avoid rub points, a more permanent material (ABS plastic?) could be used for the hard portion of the skirt.

My only BIG concern about this approach is how a front skirt will change the fenderwell behavior in winter (since we three Jetta owners commenting in here all live well into the snow belt).

I'm not so sure I want to be a guinea pig for this, because I know the worst situation would be that a front skirt would promot more fender "filling" with snow and ice while driving long distances on the highway... which may fill enough to impact steering.

I'd love to hear any input on the winter situation, either to confirm or allay my concerns.

And on the weekend, I might go and try to snap pictures showing the screw in points on my A4 fenders. I'm assuming there'd be similar points (maybe, possibly identical positions) on the A3 that Sayyad and tasdrouille have.
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Old 09-25-2008, 11:04 PM   #18 (permalink)
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Hiya,

I get the "fender filling" frozen gunk already, even without any wheel skirts. The tire wears it away -- until it melts, or I kick it out of there. I'm not sure that I'll be able to leave the Coroplast mods in place during the winter -- they might fall victim to the weight of the ice?
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Old 09-26-2008, 01:06 AM   #19 (permalink)
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If a belly pan were installed, blocking off airflow exiting from the lower rear of the engine compartment, would the hot air from across the radiator and through the underhood area be forced out along the driveshafts and suspension in the wheel wells? Maybe this would keep the tires warm in the winter. In the summer the extra heat would improve tire traction though it would probably decrease braking performance at low speeds, but all the while would keep air from ending up under the car where we don't want it anyway. Maybe some kind of sliding vent under the car to control where the air can most easily flow.
Something that I really don't understand about cars is why, if they can modernize the interiors and engineer safer windows and better paint and electronic everything, they haven't changed the basic design of the engine compartment. Not just recently; not ever. It seems to me that the engine is still basically a block of metal with dozens of messy wires and pipes, all supported by two metal beams running from the wide open grille to the flat, protrusion-studded firewall. Install a hood and fenders, some kind of bumper, and you have the basic engine compartment design of all front-engined vehicles that I've ever heard of.
Why not build a sealed compartment with variable openings for air ingress and egress? Instead of a flat firewall that impedes airflow, use a panel shaped in such a way as to direct air out hood vents at the base of the windshield. A sealed and aerodynamically optimized engine bay would control component wear by reducing rust and dirt contamination on all those hoses and pipes and electronic bits while allowing precise control of heat and aerodynamics for any driving situation.
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Old 09-26-2008, 05:56 AM   #20 (permalink)
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Hrm, I replaced most of the stock plastic undertray with a coroplast one before taking a trip. On the return trip, it was removed by a roadkill raccoon or porcupine (didn't stop to ask what it which one it was).

With just the undertray replacement (like OEM), I found that my water temperature was elevated at highway cruise speed into the high 70s, Celsius -- 74-78, in September, with air temperatures in the 10-20C range, while at 100kph

When I added a lower grille block for the radiator... I found my temperature rose much higher - Scanguage said I peaked at 96C at 110kph (legal limit for divided highways in Alberta), and 85C steady for 100kph.

I'll see about my fenderwells no matter what this year -- one is new as of August, the other is original, and the car was built in late 1999. The older ones are quite rough from all the debris flung up into the fenderwell over 8 years. Maybe the new one is the answer, and I'll get the driver's side replaced before winter. I'll probably try "greasing" the plastic inner fenders with a spraycan of kitchen vegetable oil (a.k.a. PamŽ, but I'll go generic) if I find the newer one has clogging problems still.

Looking in atop and underneath my engine bay ... things are so crowded up. I'm not sure how sealing the compartment will do regarding coolant temperatures. Does anyone know what temperature the cooling system for a TDI can take, until it's liable to overheat? Unless my sensors are out, 80C and 90C from the Scanguage is still safe; 70C and up seems to give better mileage, too.

I'm not sure what the cooling system can take during warm weather. In winter, I'd be much more game to seal things up well, especially since I know I'm headed for some LOVELY -30C and -40C weather this winter.

I'm thinking next year, after the snow's gone, I'll be investigating a way to seal up the radiator better, so that there's proper ducting both into and out of the rad. Perhaps exiting the air out to the fenderwells, perhaps out along the exhaust to cool the turbo. Part of the reason to leave it, is to think about the best approach, and to plan trips so I can get enough time and distance to test out any ideas I try

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