[Vwdiesel] smoke related to driving style
Val Christian
val at mongobird.com
Mon Nov 7 15:54:00 EST 2005
> Randy
> Can you compare 'big rigs' with lightweight cars? Maybe there would be
In the general case, they are diesels, although the trucks are
typically turbocharged. Since there is a much wider range of
technology implemented in trucks, the comparison might be
done on a particular technology level.
For example, in the case of the tractor that I had experience
with the visible carbon emisions occuring after an extended
"moderate throttle" run, the tractor is a NA IDI engine
running at about 3000 RPM. (It wasn't turbo'd, it wasn't
two-stroke, it was not IDI, etc.)
Since I have seen this behavior on IDI and TDI engines, I tend
to think it's not specific to the type of injection, or the
use of a precombustion chamber.
Mark, you might explain what you mean by inertia issues?
Bigger flywheels per HP? More RPMs at cruise? (0.5 m v**2 ?)
> inertia issues and isn't there lower emission restrictions with a big
> truck.
> Why should running steadily cause an injector to produce more crud when it
> is also running more 'efficiently'... Unless injector is producing crud at
Consider that crud can build at any time, but that high injection
rates "force out" crud. Then running at lower throttle settings
permits crud accumulation because the flow rate is reduced. When the
flow rate increases, there's an erosion of buildup at the pintle,
and after the crud erodes, then the visible carbon emissions are
reduced, presumably from a better spray pattern.
> all times but it only builds up at 'steady state'...
For most vehicles, steady state is a reduced power setting, which
translates to a reduced injection rate.
Again, I don't know the answer, I'm just exploring data which
supports or refutes the hypothesis.
Val
> Can't say I've noticed a difference with my 'Q's... Biggest change in smoke
> is outside air temp great improvement from 20 deg C to 10 deg C
> MTM
> ----- Original Message -----
> From: Randy Tyler
> To: Val Christian ; mark at shepher.fsnet.co.uk ; vwdiesel at vwfans.com
> Sent: Monday, November 07, 2005 2:14 PM
> Subject: Re: [Vwdiesel] smoke related to driving style
>
>
> I subscribe to the fouled injector theory.
>
> Improper spray pattern is causing unburnt fuel. If it were simply
> accumulated soot in the exhaust system, you would get caking of the carbon
> or coking in combination with the moisture in the exhaust. Applying power
> with the esuing rise in exhaust temperatures will start the carbon burning.
> My truck driving brother-in-law has seen muffler fires in the big rigs
> (jumbo lorries) especially at the top of long grades. Look at some of
> these trucks and the hot spots on the exhausts.
>
> IMHO I would back off the power and keep moving to get some air cooling
> around the outside of the exhaust system and look for a safe place to pull
> off. I would keep the engine running. I would check the cargo area of the
> vehicle for hot spots. What about those heat shields between the fuel tank
> and the exhaust system that were removed earlier because they were in the
> way?
>
> IMHO I think the black smoke is maintenance related not driving style.
>
> Randy
> Val Christian <val at mongobird.com> wrote:
> >
> > Could it just simply be gentle driving allows accumulation of soot in
> the
> > exhaust. Extra energy in flooring it loosens it off again. After all
> the
>
> Don't think so. It happened on a tractor I used, with only the
> exhaust manifold on. Not much to collect soot in, compared with
> the visible carbon emissions.
>
> > turbine manages to find the extra energy and turn it into mechanical
> > energy. So why can't the soot particles see this energy too.?
> > One of my paranoia's is that the annual opacity test involves
> flooring it
> > by the inspector. "Readings spoilt by loose soot?"
>
> I suggest driving it hard just before the test.
>
> My theory is that the hard drivin' stomps off the gunk
> on the injectors. Doesn't happen with brandnew injectors
> until they have 5 or 10K on them. Doesn't happen as much
> with newer injectors with conditioner in the fuel.
>
> Theory only.
>
> Val
>
>
> > MTM
> > ----- Original Message -----
> > From: Val Christian
> > To: Sandy Cameron ;
> > Sent: Monday, November 07, 2005 12:44 AM
> > Subject: Re: [Vwdiesel] smoke related to driving style
> >
> >
> > > The exact same symptoms occur on my car. The mileage reported is
> about
> > > the same as well. I have a 91 NA.
> > >
> > > No turbine wheels. We need a new theory.
> > >
> > > Strawman theory. Light foot allows carbon and longer chain
> molecules
> > > build on the pintle and other portions of the injector, and are
> knocked
> > > free with high fuel flows.
> > >
> > > Observations: Driving hard, keeps smoke clean all the time. Rara to
> the
> > > lead foot. Also, keytone and tolulene additives "injector cleaners"
> > > and "fuel conditioners" seem to reduce the intermittent lead foot
> > > smoke production. "Stomp smoke."
> > >
> > > Val
> > >
> > > >
> > > > At 05:40 PM 11/5/05 -0500, you wrote:>
> > > > >Is it a carbon build up issue? It only seems to do it when I
> drive it
> > easy
> > > > >and then push it hard.
> > > >
> > > > My TD does that. Reason says that carbon sticks to the turbo
> wheel with
> > easy
> > > > driving, and comes loose on high boost / high RPM
> > > >
> > > > Effective way to disuade tailgaters. I always seem to have a
> supply in
> > store
> > > > when needed.
> > > >
> > > > Sandy
> > > >
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> >
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