If you guys are at all like me, and living at a higher elevation, you need to adjust your boost pressure to allow for elevation changes. I finally found a calculator where you plug in your elevation, what your boost gauges reads, and then just any number for temperature and dew point and it will give you an approx boost based on elevation. Pretty cool

So my 21 psi is actually only 17.2. Oh well, I guess I'll go turn it up tomorrow.

http://wahiduddin.net/calc/calc_da_em.htm

___________________________________

That's a neat little calculator!

One interesting thing about flying small aircraft at high altitudes is that you have to lean it out as you go higher, because most small aircraft run a carb, and will continue to dump about the same amount of fuel regardless of outside air pressure.

For a fuel injected engine with speed density, this is corrected for automatically. I am not very familiar with a mass airflow systems - I'm not quite sure how those compensate for altitude changes, but I doubt they have to very accurate as far as altitude correction is concerned because you're not going to be going from sea level to 6000 feet in a matter of minutes with a car

2016 WRX STi Limited (current)
2001 A4 1.8tqms (donated)
1991 GVR4 #1933 (sold)
old.dsmregistry.com/detail.php?carid=218 (dismantled)

Mass air is simple. It doesn't care what the outside pressure is, as it is measuring the amount of air passing by the sensor, where speed density requires a pressure reading.

1998 GS-Turbo KANDY -- For Sale
1999 GS-Non Turbo 10th anniversary Edition

I have been in bed with Dino.....ask me for a picture!

I didn't think that was rude... it was just to the point. Mass air is very direct in how it measured air. It measures air by quantity, where speed density extrapolates air quantity by other factors.