Can I block part of my grille?

I have speculated before that the air flow allowed to the TDI engines is excessive, probably scaled for the gas cars. In another thread, it's mentioned that a sizeable share of drag is added by the air to the engine-- this is a generally acknowledged fact.

So, I want to cut drag here if practical. I will try for a mileage record in my 2003 Beetle, driving on cruise at maybe 50 mph. The drag component is still about 60% of load at that speed. Can I block off part of the grill on the front?

I can check coolant temperature while I'm driving, with a ScanGauge. My temperature range on slow cruise is presently about 180 degrees F.

Ernie Rogers

Two things pop in my mind.

First I block my radiator 100% (except where the intake is) in winter and it still takes 15 miles to get to 190. On my way to work it is pre-heated with the tdi-heater and it slowly drops until I am about 1/2 to work.

Secondly in the summer if you block the grill you will likely have the coolant fan running more and adding a power load to the alternator and if you run the AC you need to leave that open.

If it were me I would leave it, but if you want just slowly cover the openings and see what it does to the coolant temp, go for it. I would start with the lower openings first. A piece of 1/2 inch black pipe insulation fits perfect and is hard to even see in there. But something smoother like black duct tape or gaff tape would work better for air flow.

Yes, try it. I've left my wifes Jetta lower inlet blocked with pipe insulation since winter!!! She makes short trips so I want the car to warm up quicker. Not had a problem with overheating.

as stated the MKIV platform includes AWD automatic V6 gas engines and pd150 AWD automatics. also larger station wagons. so a little 90hp tdi at 50mph will not need the same air flow as that vr6 station wagon with AWD.

based on energy use. gasoline cars get about 50% less MPG thus they will burn more fuel per mile. Fuel = heat. so perharps the TDI could use much smaller inlets.