How accurate is the ecu at measuring boost level?

[csosnowski]

howdy everyone.

i logged some data today on my way back from a client's house, and was trying to decipher how much boost my car is making while i wait to get my boost gauge.

here part of the data, but i logged a big chunk so it would be senseless to post it all.

the first column is specced boost and the second, of course, is the actual.


900 970
900 960
1040 920
1890 1290
1880 1880
1890 1940
1880 1920
1870 1870
1860 1870
1860 1850
900 1240
900 1020
900 970
900 950
900 950


this was a pull from a rolling 40.

what im trying to figure out is how many psi of boost that is. the google calc says something crazy like 28psi = 1940mbar

i am under the impression that i have a k03 car lol, so this seems ridiculous to me to have that high of actual boost level.

any input would be helpful, thanks!

[julex]

The pressure reading is an absolute reading which means it includes current atmospheric pressure, usually 960-1000 mbar. You need to subtract that value from the reading and then calculate the boost psi.

So in you case, 1940-1000 = 0.94 bar = about 14 psi.

You can see it when you idle and you get your boost reading. That is atmospheric pressure since you're not making any boost at idle.

[csosnowski]

thanks for clearing that up for me, i can actually figure out whats going on now!

i gotta say that for having 172k miles, all the graphs of the actual boost seem good and stable.

it does feel like my car pulls less sometimes though, could that be timing retard that im feeling? which block(s) should i log for that?