Combined boost mods (was Update and EFI ECU info)

Swann, Benjamin R. (BSWANN) BSWANN at
Tue Jul 31 15:00:43 EDT 2001

Not quite, as I'll clarify hopefully.

The chip in and of itself does not produce the boost, well maybe a little,
to around 1.6 BAR through frequency valve control - at least that's what I
confirmed when testing with no other modifications.  

The Shrapnel knob allows to adjust for the maximum boost attained.

The stronger spring also helps attain max boost, but more importantly, helps
get the boost up faster by keeping the wastgate clamped longer until control
limit is reached, normally by frequency valve control, or in my case the
knob setting.

The QLCC chip modification provides that: 
1. The overboost shutdown is raised to 1.9+ bar(just below the 2 Bar rating
of the pressure
transducer in the ECU.

2. The WGFV boost tables are modified to leave the WGFV open longer, until
the boost
gets up to at least the 1.6-1.8 bar level.  This feature is overidden in the
setup as I have it, so in that respect you are correct.

3. Timing and fuel values remapped to accomodate higher boost settings.
This is something the resistor mod. couldnt do, which is why I wanted to

The resistor value I am using is much higher than one used without a
modified chip - around 4Kohm.  It allows a bit more boost without shutting
the fuelpump down at 1.9 bar.  It retains the timing advance and additional
fuel map, skewed ever so slightly by the resistor mod.

It works far more cleanly than just the resistor mod, as the timing was way
too advanced with just the resistor.

I know it sounds like a kludge, but I did a significant amount of testing to
get the settings correct.  I have been using this setup for about 10 months
now, and drivability is better than  with only the resistor mod.  

With this setup, I am definately pushing the envelop of fuel and timing.  As
alway i'm looking for cost effective ways to get even more power without
blowing the engine up.  I think at this point the next thing I may expore is
water injection.  For now the car drives great and I'll likely not tackle
this project until long after finishing with Project GTQ - if that is

Hope this clarifies.


-----Original Message-----
From: Mike Del Tergo [mailto:mdeltergo at]
Sent: Tuesday, July 31, 2001 12:52 PM
Cc: quattro at
Subject: Re: Update and EFI ECU info

'87 5000cstqw Bossted with QLCC+Resistor Mod + 2Bar Spring and Shrapnel knob

to around 18 PSI - anymore and she detonates!

you seem to be running self cancelling boost mods?  With the QLCC you don't 
want/need the resistor mod and with the Shrapnel Knobben you don't need the 
extra heavy spring in the WG. BTDT 81 UrQ

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