VW Passat air intake - front upper grille modification

difficulty: 1/5
back to 1000q: B5.5 VW Passat TDI "how to" index

Introduction

Some passat had blocked off air intake grilles, some had open grilles.  There doesn't appear to be any logic to which part got onto which car - it could have been as simple as the guy on the assembly line grabbing something from the box on the left vs. box on the right.

A blocked off grille will help give more water splash protection but an open grille will give less resistance to the engine air intake.  Enough water getting into the intake air could damage the turbo or hydrolock the engine, causing severe damage.  Since the air intake is at a high spot and the intake air box has a water trap, I feel that opening the grille won't cause any problems, especially since many passat have open grilles stock from the factory.

On the other hand, plenty of air still gets to the cold air snorkel through the lower grille.  If it didn't then your engine would have problems running normally.  Opening the grille should reduce air resistance but there might be added turbulence from being broken up and passing past the grille slots (instead of staying in 1 mass and moving through the top large grille).

For a very good air intake you would have to make a custom cold air snorkel with a velocity stack underneath the air filter like the one pictured below.  Although you'd only get a few horsepower at this level of modification, every little bit adds up.  I do not suggest putting on an aftermarket oiled air filter on your TDI because it runs by throttling fuel not air and VW MAFs tend to be very sensitive to contamination.  See 1000q: MAF FAQ for more details on the hot film sensors and why they are differnet than old style sensors.

Lastly, the same exact air filter used on your 138 hp VW Passat TDI is also used on the 1.8T Passat and Audi A4, various V6, and even the high performance Audi S4 and V8 engines.  If it flows enough for an engine with twice the horsepower, it flows enough for your TDI engine.

Air grille modification procedure

Dremel out some of the holes.

Before:

After - I didn't remove all the slots to prevent weakening the cheap replacement replica grille's plastic.  The replica grille looks flawless from a foot away and was half the price of a new OEM, but copycat parts tend to have more brittle plastic.

Did this do anything for you?  Did you notice any difference?  Share your experience in the myturbodiesel forums, linked at the top and here.