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-   -   Jetta TDI Duct Tape Mods (

Sayyad 09-01-2008 03:31 AM

Jetta TDI Duct Tape Mods
5 Attachment(s)
I'd like to thank all of you who post your vehicular modifications on this site. You all inspire me. This post is the beginning of my contribution to this community and the humble beginning of my car's transformation.
I used silver duct tape to update the aerodynamics of my silver Jetta, masking off most of the front grilles (leaving the intercooler air intake open), any possible gaps over the front wheel wells and as much as possible of the rear wheel wells. I also tried to make a front undertray but it sort of took itself apart within a few kilometers.
The tape isn't the greatest for this. I had to roll up the edges of the front skirts a bit (but that's okay; easy to do since the inside edges can be rolled in and stuck to themselves) because they rubbed the tops of the tires a bit. I'm also pretty sure the rear skirts got sucked in a bit towards the tires at speed. And the lower front grille block tore open just a little bit along a tape seam at around 400km into the trip.
Which brings me to what you're probably all wondering: did it work? Yes it did.
The car's previous best was around 4.8ish using dino diesel. With these duct tape mods the car used only around 4.3 litres per 100km using B20. Mostly highway, but all the rest was literally spent stuck in traffic, being tailgated by jerks who were really keen on getting to the next red light.
So I think my next move is to make these mods more durable.

tasdrouille 09-01-2008 08:21 AM

Now that's funny. We have exactly the same car. Good work on the car. Keep it up.

FunkSkunk 09-01-2008 07:52 PM

Careful, don't leave that on there too long or else you will have a heck of a time getting the duct tape residue off your TDI.

Sayyad 09-01-2008 08:00 PM

Yeah, I'm washing the car tomorrow and I'm sure I'll have a good time getting all the residue off. Apparently either Goo Gone or equivalent or good old WD-40 should do the job; just don't leave either sitting on the paint for long and wax the car after.

tasdrouille 09-02-2008 07:34 AM

BTW, I blocked the intercooler grill. You'd be surprised how good of a job it still do even without airflow rushing through it. Cruising on the highway at 60 mph on a fairly hot day, my IAT was 110 F.

ChrstphrR 09-02-2008 08:40 AM

On my A4 TDI, I've blocked underneath the valance - so that between the ground and the intercooler, there's not as nice a place to empty out the air that rushes through -- but I've kept that front grill closed.

I would like to figure out a better way - ducting the air out into the fender, perhaps (I'm missing side skirts yet, so intercooler air probably exits out there, but that cavity down by the intercooler is quite big.

A question, since I haven't seen an A3 engine under the hood - where does that model pick up it's air from the front? On my A4, it's on the upper corner of the upper grille.

I was thinking about that when looking at Sayyad's taped upper grill block: About 1/4 of the A4 upper grill feeds the air intake, so when I get to making a block, I won't be blocking that.

Sayyad 09-02-2008 09:40 PM

1 Attachment(s)
The A3 cars get their intercooler air from the lowermost driver's side grille, which has a duct directing all air from that opening (and rocks, and water spray, and the occasional bird) right into the intercooler. You may be able to see the duct and the intercooler at the end of it in the photograph I have attached to this post.
I don't know where the air exits; probably out the back of the front undertray along with the air that passes through the radiator. This probably isn't that efficient but it must work well enough if tasdrouille can block off the air supply and still have low intake temperatures.
Wait; tasdrouille, did you measure your intake air temperature before or after the turbocharger and intercooler?
A3 Volkswagens get their engine air from a hole in the passenger's side fender. This air then passes through a pipe with a few bends, a piece of mesh (the snow screen), a large airbox, the filter, the mass flow sensor and then on to the engine.
Anyway people have been known to drill holes or install a dryer vent grille through their fender liners right behind the intercooler with good results.
I seem to remember that wheel wells containing a spinning tire have low pressure in front and at the back and high pressure at the top and where the tire meets the road. If this is true then placement of the wheel well exit vent would have to be just right. Of course I'll bet the pressures in the wheel well would change completely if it was no longer a sealed area. Anybody have access to a supercomputer to run some calculations?:rolleyes:

tasdrouille 09-02-2008 10:00 PM

I got the temp from the IAT sensor which is past the intercooler. Ambient was 85F that day. Cruising at 60 mph average boost was roughly 1.5 PSI at the turbo outlet. As stated earlier IAT was pretty steady at 110F.

That would be a totally different story if I was putting a big load on the engine, but in my particular case with the way I drive, it does not make much of a difference.

Sayyad 09-02-2008 10:49 PM

That's quite good indeed if it's after the intercooler. I probably don't know enough about turbocharging but a rise of only 13 degrees Celsius through all that piping and the turbo and a sealed engine bay seems very good.

slipstreamer97 09-03-2008 12:12 AM

thats awesome,

I just did the same thing myself. made a full grill block and taped all the crevices and gaps in the front area. On my previous trip from LA to Sac i got 38, this time i got 43. Also employed some PnG as well (as much as you can with an auto tranny).

Good work


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