I haven't verified any of this, so let the buyer beware...

I do indeed think the WRX turbo gauge is calibrated in Mega Pascals (MPa), and the dial does indeed say "MPa".

I found this on the web:

Average atmospheric pressure at sea level is:
1 atm = 1.013 x 10 xx 5 Pa = 101,300 Pa = 14.7 lb/in xx 2.
Now 101,300 Pa is 0.1013 MPa.

The Turbo gauge goes from -0.1 to +0.15.

The crux to understanding the Turbo gauge is to realize that 0 means the pressure inside the intake manifold is the same as ambient (outside) pressure. This can be seen when the electrical system is active, but the engine is shut off.

+0.15 means the pressure inside the intake manifold is one and one half atmospheres above ambient pressure, for a total intake manifold pressure of two and one half atmospheres.

-0.1 means that the pressure inside the intake manifold is one atmosphere below ambient, i.e. there is total vacuum (zero pressure) in the intake manifold.

I thought this was really cool, and I wanted to share!

DannyB

 

 

HAHAHA, flux capacitor! but seriously thanks for the info. but what i was really wondering is how it compares to psi. how do the number relate? or don't they relate equally because one is based on atmospheric pressure and the other is based on....? i don't know. but what is the comparison between the 2?

 

I think he gave an explanation of converting between units, as well as why the gauge has both positive and negative readings. Searching Google will bring up a number of conversion calculators for anyone that's curious on the conversions for psi.

 

i looked it up. just so everyone knows. 15 psi is equal to .1 Mpa. which works cause i usually top out at just above the mark right before .1 and since the wrx runs 13.5psi it fits. also 75 psi is equal to .5. i know no one will be running 75 but that give you 2 points so you know they are on an equal curve.

 

It's mPa which is a multiple of BAR (kilopascals) 1 Bar = roughly 14 psi

 

Mpa 0.01

 

opps sorry typo