# determining boost pressure with a vag-com



## Sidewayzracer (Oct 30, 2007)

Is it possible to determine your boost pressure with a vag-com or is it gauge only?


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## hatetolovemydub (Oct 27, 2009)

vcds will do it more accurately than a gauge. It uses the map sensor.


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## xxsur3shotxx (Sep 24, 2009)

block 115. requested boost and actual boost.

Two things to know: 
1. The map sensor gives values in millibar. You need to convert to PSI if you aren't comfortable with those units.
2. It reads absolute pressure, so you will need to subtract atmospheric pressure from your numbers in order to obtain gauge pressure.


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## Sidewayzracer (Oct 30, 2007)

awesome thankx m8s, i was sure it was possible to get the readings but i was unsure of the measuring block


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## Cryser (Sep 9, 2009)

xxsur3shotxx said:


> block 115. requested boost and actual boost.
> 
> Two things to know:
> 1. The map sensor gives values in millibar. You need to convert to PSI if you aren't comfortable with those units.
> 2. It reads absolute pressure, so you will need to subtract atmospheric pressure from your numbers in order to obtain gauge pressure.


yup substract about 1000 mbar from the total to get your actual boost pressure

1 bar = 14.7PSI = 1000mbar


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## Sidewayzracer (Oct 30, 2007)

ok i had a chance to plug in the vag-com and run block 115 and it displays N/A across the board. This is a AEB b5


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## Sidewayzracer (Oct 30, 2007)

used some googlefu and it seems my car has no boost pressure sensor so looks like i will have to get a boost gauge.


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## Nevaeh_Speed (Jul 9, 2004)

Doesn't it only read up to 22 psi though?


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## Camride (Oct 16, 2005)

Nevaeh_Speed said:


> Doesn't it only read up to 22 psi though?


Yes, the MAP sensor only reads up to 2540mbar, which is 22.3psi.


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## elRey (May 15, 2001)

I like to use vagscope on 115 or 118. Then set the ranges for the boost channels as so:

2530
1151


what that does is scale the graph so that every horizontal line is 2psi. The very bottom 2psi and very top = 22psi.

So, if the boost hits the 2nd line (1st line above bottom) = 4psi, 3rd line = 6psi... and so on.


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## [email protected] (Jun 5, 2002)

AEB has no MAP sensor so you can't read boost via diagnostics. You'd need to install a gauge.


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