[MTXA]

Pretty soon, I'm going to be experimenting with some aerodynamic mods on my car. Some of the mods will include grill blocking, a front under tray, smaller door mirrors, partial kamm back. I want to collect empirical data supporting whether or not the modifications are a net loss or gain. I'm self teaching myself about aerodynamics as they relate to automobiles, and am still in the early learning stage. I would like to know how, for instance, the under tray effects under hood pressure and temperature change.

To the point, I have a few novice pressure reading questions.

1. I want to keep my test equipment costs low and prefer to only have to purchase one magnahelic gauge. How many inches of water scale would serve both interior and exterior testing? 0 - 1 wg? 0-3 wg? Higher?

2. Are pitot tubes necessary for measuring the air in the slip stream?

3. Is there a range of selection in pitot tubes or does one size fit all?

4. I would assume that when measuring pressure in a slip stream, I would position the hose end of the gauge directly downstream as indicated by tuft testing, correct?

Thanks in advance!