I'm trying to figure out why my Vortech went from boosting 9.23psi to 7.78psi, and I was wondering about air density and temp. The car was boosting at the higher level when the weather was quite cold. Now that it's warmed up, we have the lower boost level. I'm also checking for leaks, worn/loose s/c pulley belt, and anything else I can think of.

SO, back to the question. My IAT's are running from 100-119 degrees F with about 60-70 degrees ambient. Is that OK for an aftercooled Vortech?

 

around 100F intake also....
anyway dedpending on weather i noticed up to 1.4psi difference..hotter is around 14 psi here and cold nights,with ice is 15.5 psi
check your belt if you didnt already.
Stefce

 

when the temperature is colder, the air is more dense. Which means there are more o2 atoms per square inch of air! This not only increases your overall boost pressure, but introduces more oxygen atoms into the motor, and with more fuel, produces a larger explosion and subsequently more torque etc...

You can see the relationship between temperature and air density here:
http://en.wikipedia.org/wiki/Density_of_air

Its a very interesting read! It also introduces humidity into the formula, which decreases air density as well!

 

Yep, good old PV=nRT. Just looking at that formula gives me PTSD from the 4 years of Physics at Johns Hopkins. Ugh.

Anyway, today it was 44deg (gotta love Texas - yesterday it was 80) and I'm back to boosting 9psi with IAT of about 75 after a few hard runs.

 

12.5 PSI, 86 deg F IAT, 65 deg F ambient temp on a dyno making a pull, small dyno fan in front, coolant temp 171 F, 16th run of the day, Koyo radiator.

GT3076R & Full-race mani, Precision 600 FMIC, Custom CAI (pics in link).

Granted it's a turbo, but it hopefully serves as a data point for discussion. Good thread.

Stanford