Re: Turbo Boost

[Robert Myers <rmyers@inetone.net>]

At 08:17 PM 12/06/1999 -0600, you wrote:
>Hi
>I'am overhauling my 86  QT and when done I would like to increase the
>boost. I've been reading up on doing this which brings me to question.
>On my engine factory boost is around  1.3 bar (18psi) but on Scott M.
>web site it say not to pressure test the ECU above 15psi  or the
>pressure sensor could be demanged. I don't understand the factory boost
>is already above 15psi.
>Could someone shed some light on this for me.

Dave,

You are confusing absolute and relative pressures.  The 18 psi "limit" is
18 psi (psig) above ambient (which at average sea level is 14.7 psi
absolute [psia]).  This corresponds to 18 + 14.7 = 32.7 psi absolute
(psia).  The 1.3 bar "boost" is 1.3 bar absolute or 1 bar (= 14.7 psia)
plus 0.3 bar (0.3 x 14.7 =~ 4.3 psig) = ~18.3 psi absolute (psia).  This is
significantly below the 18 psi (= 32.7 psia) boost limit.

Scott's "18 psi" is psig.  Your "18 psi" is psia which is 14.7 psia below
18 psig.  You have *lots* of room to play with.  Another ~14 psi, in fact.

Definitions:
psia = pounds per square inch absolute (meaning measured relative to zero
pressure or total vacuum).
psig = pounds per square inch gauge (meaning measured relative to ambient
pressure - roughly one atmosphere or 1 bar).



>
>Thanks Dave Anseeuw
>1986 Audi 5000 CD Quattro Turbo
>
>Attachment Converted: "D:\EUDORA\ATTACH\Anseeuw.vcf"
>
___
   Bob
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