MYTTS

Is this correct? Did some searching and found something like this. Thanks.

quickaudi:STFA

1600 mbar = 1.6 bar, however, you have to remove atmospheric pressure.
From Google, 1 600 millibars = 23.206038 pounds per square inch, but you then have to remove atmospheric pressure, which is approximately 14.7 psi. So, if you do that, you get around 8.5 psi. Of course, you could use a different number for atmospheric pressure and get a number closer to 8.8, I'm sure.

Mark P

I believe, however, what you are asking is to find how much PSI you are making based on the "mbar" reading in VAG-COM, ECUx, etc.

Those tools read the car's ECU which has a value for the Manifold Absolute Pressure (MAP) sensor. The Absolute pressure, is just that, absolute. That is, it's the combination of the atmospheric pressure (pressure exherted on your body and everything around you) plus any additional pressure added by your turbos.

Atmospheric pressure + Boost pressure = Manifold Absolute Pressure

To find out how much pressure your turbos are adding, you have to take that value, and subtract out the atmospheric pressure. At or around sea level, this is near 1 bar (1000 mbar) [it's really 1 ATM, which is 1013 mbar, but we'll ignore that for easy math], and thus what led to you subtracting out that value in your statement. This will vary with elevation and other barometric conditions. When I log with ECUx, I also log this atmospheric pressure. I take the MAP value and subtract this to get the boost pressure - this way, if the atmospheric pressure is not 1000 mbar, I'm accounting for it.

So, what you need to know is:

1.) Your car reports Manifold Absolute Pressure
2.) Manifold Absolute Pressure = Atmospheric pressure + Boost pressure
3.) Atmospheric pressure is typcially near 1000 mbar, but best for you to log to find out.
4.) 1 bar = 1000 mbar
5.) 1 bar = 14.5 psi

So, if you are reading 1600 mbar from your car, and you're at approx 1000 mbar atmospheric pressure...

1600 mbar - 1000 mbar = 600 mbar Boost
600 mbar Boost = 0.6 bar Boost
0.6 bar Boost * (14.5 psi / 1 bar) = 8.7 psi Boost

quickaudi:STFA

i was first!!! :P

Mark P

you just wrote less! :P

quickaudi:STFA

true; would have been more accurate if I had found the correct number for atm psi.