latest on boost saga

Ben Swann benswann at
Mon Dec 22 08:14:10 PST 2008

Just to support the other expanations, it works out like this.

2Bar / 3Bar * 2Bar = 1.33..where  2Bar is max boost via original 2bar pressure
transducer capability,  3Bar is new max boost via 3bar pressure transducer, and lastly
2Bar is max programmed value likely programmed into the ECU boost chip(substitute what
the max prgrammed value is or what you expect to see).  Basically the reaout on the dash
will be about .67 of the actual pressure that might be seen on a guage plumbed into the
manifold (teed off of the ECU line).  The dash readout reflects the voltage output of
the pressure transducer inside the ECU which has now been replaced by a 3bar unit and
therefore skews the voltage out to the digital readout in the instrument cluster lower
and results in a lower reading.  Any chipset that requires changing the pressure
transducer will result in lower reading on the dash.  The 2.5 bar readings are about .8
times the actual or conversly to get actual gauge reading multiply by 1.25, and for 3
bar multiply by 1.5.

Also keep in mind that these antiquated digital readouts react slower than analog and
also round down, so boost could be 1.3 or 1.399 yet reading will be 1.3 despite that at
1.399 that boost should really read 1.4 by most peoples math.  Also, the slow reaction
might show 25 PSI on a pressure guage for a 3 bar chip runninng not quite full
programmed boost - but by the time the boost has backed off to a lower reading which
typically occurs, the digital one never has time to react(compute the output).  So you
won't see a value that corresponds to 25 PSI which might otherwise be 1.1 on the boost
guage, but usually a lower reading.   You might ultimatly see the rounded down value
corresponding to 25 PSI if you were to hold that level for a few sec.   That is of
course if you were studying the digital readout instead of watching where you are going
while accelerating rapidly under boost.

Hope that clarifies more than confuses.


[Date: Fri, 19 Dec 2008 12:19:00 -0800 (PST)
From: robert weinberg <centaurus3200 at>
Subject: RE: latest on boost saga
To: 200q20V mailing list <200q20v at>
Message-ID: <496328.16228.qm at>
Content-Type: text/plain; charset=iso-8859-1

interesting. what's the math behind this?


--- On Fri, 12/19/08, YBK <ybk at> wrote:
From: YBK <ybk at>
Subject: RE: latest on boost saga
To: centaurus3200 at
Cc: 200q20v at, brogers at
Date: Friday, December 19, 2008, 11:18 AM

1.4 with 3.0 sensor is perfect. It could be anywhere from 1.40 to 1.49 which is similar
to 1.8-1.9 with 2.5 bar sensor.

What do you see with engine off and ignition on?

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