[Vwdiesel] Limp Mode Frustration

Mon Mar 5 20:53:58 PST 2012

Very cool setup Andrew.  Clever way to get boost maxed quickly without
overfueling and when you need it.  Certainly replaces a lot of electronics
to effect the same thing.
-james

-----Original Message-----
From: vwdiesel-bounces at vwfans.com [mailto:vwdiesel-bounces at vwfans.com] On
Behalf Of Andrew .Libby
Sent: March-05-12 7:50 PM
To: Tad
Cc: vwdiesel at vwfans.com
Subject: Re: [Vwdiesel] Limp Mode Frustration

Here's a link to my current design:

http://www.vwdieselparts.com/forum/viewtopic.php?f=21&t=11042

I've made a couple since that one, but the design hasn't changed because I
can't see a way to make it better.  :-)

Because my control links the accelerator pedal to the vane lever, with my
foot I can feel any changes in the motion of the vanes.  Because I currently
work from home, almost all of my driving has been taking my kid to school
and getting them at the end of the day.  Flagstaff is COLD in the winter and
most of those trips are cold engine runs where it doesn't even make it to
normal operating temp.  I've noticed that after a couple/few weeks of that
sometimes I get the slightest hint of sticking when the engine is cold.  It
goes away within 30 seconds or so of running.  A decent longer drive will
eliminate the sticking.  If I go on an extended highway cruise with a few
grades, then it can be weeks/months before the vanes demonstrate any
resistance at all.

Andrew

On Mon, Mar 5, 2012 at 10:12 AM, Tad <tadc at europa.com> wrote:

> Andrew - not my car but I figure I'll chime in since I'm here:
>
> 16618 - Boost Pressure Regulation
>            P0234 -
> 35-00 - Limit Exceeded (Overboost Condition)
> 16492 - Manifold / Barometric Pressure Sensor (G71) / (F96)
>            P0108 -
> 35-00 - Signal too High
>
> are the codes, thrown variably.
>
> I'm curious about your VNT controller - what do you use to control the 
> vanes?  Stepper motor?
>
> I'm also surprised at your comment about extended highway runs 
> removing all carbon.  Not arguing, just I've never heard that before.
> Could you be more specific about that, like the duration, steepness, 
> aggressiveness of the run (WOT the whole way?)
>
> I wonder if injection timing might play a role as well - as I 
> understand it, retarded timing = higher EGTs, which would logically 
> tend to burn off the carbon more.
>
> One possible clue is the OP had a blown head gasket, which I think is 
> pretty rare for TDIs.  I wonder if that's a cause or effect of the 
> overboosting?
>
> On Sun, Mar 4, 2012 at 6:37 PM, Andrew .Libby <libbybapa at gmail.com> wrote:
> > I don't have a lot of experience with the computer controlled VNTs, 
> > but have a lot of experience with mechanical controls I've 
> > designed/built and pretty much perfected.  In my experience, lots of 
> > cold engine short runs will tend to cause the vanes to stick.  
> > Running the engine up to normal operating temp and then taking 
> > several trips up an extended highway grade will remove ALL the 
> > carbon from the vanes.  They can stick in any
> position
> > or even just be a bit sticky at one extent of the range of motion.  
> > In other words, I have seen them stick only at the fully wide open 
> > position
> or
> > the fully closed position.  My latest mechanical control has been
> fantastic
> > and has kept the vanes free, but the stock vacuum actuator/control 
> > is far less accurate.
> >
> > WRT this specific thread, I will admit I haven't kept up on it.  I
> haven't
> > read through quite a few of the posts.  Is it tossing a code for
> overboost?
> >
> > Andrew
> >
> > On Sun, Mar 4, 2012 at 7:06 PM, <LBaird119 at aol.com> wrote:
> >
> >>
> >> In a message dated 3/4/2012 1:49:39 P.M. Pacific Standard Time, 
> >> davevw at yahoo.com writes:
> >>
> >> I have  heard of people having success blowing the vanes clean by
> driving
> >> it  hard.  Is this at all effective if it is in limp mode and the 
> >> turbo is shut down by the computer?  Do I need to keep restarting 
> >> it to  clear limp mode (briefly...) or can I keep driving it hard 
> >> to try to blow  it clean even though it is limping?
> >>
> >> Also, if the vanes are stuck  from crud, will the actuator rod 
> >> move?  I
> was
> >> under the impression it  wouldn't
> >>
> >>
> >>   Andrew Libby is probably the resident VNT expert.  He'd likely  
> >> know
> best
> >> about what you might or might not do or expect, and what would fix  it.
> >>  I'd say that driving hot and hard won't hurt it.  Even in limp  
> >> mode,
> the
> >> turbo is working.  It may not be boosting all it should nor the  
> >> vanes moving as you'd like but you can still blow some carbon out
anyway.
> Hard
> >> and
> >> higher rpm can indeed clean stuff out.  Don't know if it'll fix it  
> >> but
> it
> >> shouldn't hurt.
> >>    Loren
> >> _______________________________________________
> >> Vwdiesel mailing list
> >> Vwdiesel at vwfans.com
> >> http://www.audifans.com/mailman/listinfo/vwdiesel
> >>
> > _______________________________________________
> > Vwdiesel mailing list
> > Vwdiesel at vwfans.com
> > http://www.audifans.com/mailman/listinfo/vwdiesel
>
_______________________________________________
Vwdiesel mailing list
Vwdiesel at vwfans.com
http://www.audifans.com/mailman/listinfo/vwdiesel