[Vwdiesel] Limp Mode Frustration

Tue Mar 6 09:07:10 PST 2012

I must say it works incredibly well.  Boost is always available.  Max boost
control is rock solid.  Power delivery with pedal position is fantastic.  A
well controlled VNT is almost as big of a performance jump over a
wastegated turbo as a wastegated turbo is over having no turbo at all.  :-)

Andrew

On Mon, Mar 5, 2012 at 9:53 PM, James Hansen <jhsg at sasktel.net> wrote:

> 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
> > >>
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> >
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