[s-cars] Stage 1 Expected Boost Levels

[Keith Maddock]

Cody,

Pure hypothesis/conjecture/opinion/food-for-thought here (keeping my foot close to my mouth for easy stuffing!), hoping someone with actual knowledge/data will kindly point out an error in my thinking ! :)

Assumption A:  Since your ECU that was previously running "3 BAR" software, I'm going to assume that your ECU still has the 3-bar pressure transducer.
Since 1) You don't mention using a different ECU, and 2) a guess that you didn't purposefully swap your 3-bar pressure transducer for a 2.5-bar pressure transducer in order to sell the 3-bar unit at a profit on the Bosch 3-bar pressure transducer black market :)

Assumption B:  Now you are running "2.5 BAR" software that was designed to be run on a ECU with a 3-bar pressure transducer.

My hypothesis being that running software that is expecting a different characteristic signal from the pressure transducer than what it is actually getting, will affect your boost levels, as it uses the signal from the pressure transducer to do "closed-loop" control of the manifold (implied boost) pressure.

By "characteristic signal" I mean the pressure transducer converts the pressure to a voltage,  Such that V~=mP+B in the linear rated region of the transducer (0-2.5 bar or 0-3.0 bar)  (where m is some slope and B is some offset, from the classic y=mX+b equation)  *** Anyone have the technical data for the 2.5 and 3.0 BAR sensors??? ***

So say that the 2.5 BAR software is trying to give you 21 psi boost.  The software essentially would calculate a voltage that it wants to see from the pressure transducer feedback circuit, and then regulate the WGFV to achieve that.  However since you have a different transducer, the calculated voltage desired is no longer accurate, and perhaps when the software is thinking its getting 21 psi boost, its only actually getting 18 psi...

Sorry to anyone offended by the lack of monkey or chrome mirror related content... :-D

Cheers
Keith "Pondering Pressure-transducers in rheinland-Pfalz" Maddock
93 S4 mit 3-bar transducer, 24-25psi (OR, USA)
95 968CS stock, ohne boost, but still fast  (R-P, DE)

****************************************************************
Keith Maddock, TRW Automotive,  Koblenz, Germany
Slip Control Systems, Systems Design, Traction Control
+49 (0)261/ 895 2474     -    -    keith.maddock at trw.com

>>> "Cody Payne" <Cody.Payne at bconnected.com> 21:36:27 07.10.2002 >>>
Gentleman,
	As you may or may not know I recently changed out my MTM Stage 1+ 3 BAR software to the ASW Stage 1 2.5 BAR software.  With the MTM I was getting around 26 PSI WOT...but didn't like the on/off throttle response.  So now I have a 2.5 BAR chip from ASW which is very smooth on the throttle response but on my boost gauge I am only seeing 18 PSI WOT.

Is this normal for you Lehmann and IA Stage 1 2.5 BAR ECU mods?

Thanks

Cody
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