Boost levels

Smeins, Larry lsmeins at
Thu May 3 10:31:52 EDT 2001

What I stated is based on what I have observed and my analysis of what is
happening.  I posted some of my observations a few weeks back hoping to
either get confirmation or a "you're full of it" response.  I got no
response.  What really took me by surprise is it appears that the WGFV duty
cycle never goes above 50% and I've had that confirmed by two other listers
that have high boost mods on their cars.  My analysis says that with 50%
duty cycle the wastegate opens .2 bar above the spring setting which gives
1.2 to 1.3 bar at our altitude.  It also corresponds with 1.4 at sea level
which is the stock boost setting.  According to  Scott's site, the boost
bible,  the spring is set from 1.2 to 1.3 bar.  I read that as at or near
sea level.  I am quite confident in my statement about altitude dependence
of the spring pressure. I've been driving my Audi for over 200k miles at
this altitude and have never seen above 1.2.    It appears that in stock
trim boost is limited to 1.4 bar at sea level with or without feedback.  I
am considering making a duty cycle multiplier circuit to crank up my boost
to sea level boost pressure.  That would be an electronic Schrapnel Knobben
that retains the ECM protection features.  A slightly stiffer spring,
washers may accomplish this, is another possibility.  Presently I'd be happy
to just get sea level performance.  I don't want to risk melting pistons or
valves in my 260k miles+ daily driver.

Is there anybody is this great group that understands the altitude effect on
our boost?  Reading Bentley gives the impression that absolute boost
pressure should be constant but that is not what I observe.  It appears I'm
not the only one seeing 1.2 bar max at 5000 feet.  If I am wrong I have no
problem with being told that I'm full of excrement just tell me why as well.


> -----Original Message-----
> From:	Robert Deis [SMTP:rdeis at]
> Sent:	Thursday, May 03, 2001 8:39 AM
> To:	Smeins, Larry
> Subject:	RE:Boost levels
> On Wed, 2 May 2001, Smeins, Larry wrote:
> > I've observed a maximum WGFV duty cycle of 50% on my 5kt
> > which produces 1.2 bar.
> >
> > If working correctly the boost indicator should read 0.8 with the engine
> not
> > running and ignition ON, in Denver.
> Really? Wahoo!  Mine does that, but I've been under the impression that
> I'd see 1.3 if everything was good in stock trim...
> -Rob in Lafayette
> 86 5kTQw
> 83 Starion LS
> 94 Talon TSiAWD
> -- 
> --------------------------------------------------------------------------
> ----
>   Rob Deis                  "Let the people know beforehand what the law
>   MiB3347                      is and what they are to expect." 
>   rdeis at                              -- 18th Congress, Rec. 75

More information about the quattro mailing list