[200q20v] Boost

Brian.Link at Level3.com Brian.Link at Level3.com
Tue Oct 17 08:59:08 EDT 2000

I have installed a VDO boost gauge, and I can see the boost taper off very
repeatable in the same rpm range.  It could be heat soaking, but the next
shift up will make max boost until @5000 rpm and then it tapers back down.
Yes it does follow the graph on the SJM web page. 
So, is this a way to protect the turbo?  Or heat soaking of the IC?

Brian Link

-----Original Message-----
From: C1J1Miller at aol.com [mailto:C1J1Miller at aol.com]
Sent: Tuesday, October 17, 2000 6:29 AM
To: QSHIPQ at aol.com; Link, Brian; 200q20v at audifans.com
Subject: Re: [200q20v] Boost

In a message dated 10/17/00 4:33:45 AM Eastern Daylight Time, QSHIPQ writes:

> Let's not immediately assume that the drop in boost is a "chip thing".  
> most drops in boost occur from either high charge air temps (heat soaked 
> intercooler), or from high engine temps.  Both these inputs to boost will 
> revise the boost threshold, especially in the chipped cars.  Heat soaking 
> stock intercoolers on chipped cars, especially k24 equipped 200's/S4/S6 
> cars can happen in a matter of a couple hundred feet, btmt.
>  HTH
>  SJ

IME with the two mods (Hoppen/Lehman and IA) on the 20vt 200q, max boost is 
seen at the lower rpm range.  If you're on a highway, tooling along without 
boost in 5th gear at say 3000 rpm, then downshift to fourth and nail it, 
you'll be at higher rpms, and won't see the level of boost you'd see if you 
were in fifth and a couple thousand rpm lower.
So, what I see is peak boost levels at around 3k rpm or so, not sustained at

higher rpms (such as 4800 rpm up).

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