[Vwdiesel] smoke related to driving style

[Randy Tyler]

Mark;
 
I compared rigs and cars because they are familiar sights.  I know that smoke (any color white, brown or black) is costing extra money for the work being done.  Clear exhaust with as much heat extracted by the engine as work as possible is what I always wanted to see.  
 
Emission regulations are curious things and sometimes double edged.  California has strict emmission controls.  It is also energy hungry and water poor.  The  LM2500 I am told is the power plant of choice for pumping natural gas.  In order for the engine to meet enviromental regulations, water is injected.  I am told that each pumping station consumes a lot of water of which California is in short supply.  http://www.energy.ca.gov/papers/JANES-ASME-PAPER.PDF  See page 4 of 12
 
Injectors can go off even when running steady.  Crud getting through the filter is one culprit.  Varnish is another.
 
What I gleaned from the problem was that the car did a lot of driving at 55 mph (90 k/hr) .  While that is now at the low end of highway driving speed, still within the design envelope.  Injector cleaners cleared up the problem for periods of time so I would still look for reason crud building up around the sprayer nozzle or other reasons for incomplete combustion.  Don't know the complete design of the specific injector and how it operates.
 
Outside air temperature is a factor but do not confuse condensed water vapor with unburned combustion products.
 
And lastly, I like the rythum of my 95 Passat wagon running between 103 and 110 k/hr on the highway.  Subject to road conditions, the pony's like to run.  
 
Perhaps there is a balance to be met of injectors and driving style.  
 
Diesel engines like to work and they respond very well to clean fuel, regular maintenance checks, fluid and filter changes.
 
 
 
Mark Shepherd <mark at shepher.fsnet.co.uk> wrote: 
Randy 
Can you compare 'big rigs' with  lightweight cars? Maybe there would be 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 all  times but it only builds up at 'steady state'...
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








		
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