More Black Smoke than "Normal"

[johnbrowder]

Janene and I are on a 6 week western US trip that is scheduled to end up in Austin at POG. We have logged about 3500 miles and things are going well. I have noticed recently that on acceleration (or even kicking on high idle) I see a brief puff black smoke from the exhaust. There has always been a little, I would guess it is twice as much now. I never recall seeing ANY when turning on high idle. It still only last a second or so.

We have been in cooler temps, less humidity, and higher elevations than routine. No engine fault codes, and no change in mileage.

Should I be concerned?

[grantracy]

I had the same problem and went to a DD service facility, turns out defective injectors were the culprit. Also discovered hardware for Jake brake was broken...don't know if the two were related...anyway that was my experience.

[Jon Wehrenberg]

John,

When you get back to lower elevations see if it has gone away before considering remediation. I know DDEC is supposed to compensate for loss of boost due to altitude, but that might be normal.

[Larry W]

John
We live at 6000 ft above sea level. Our bus puts out more black smoke when starting from a stop or when I really ask for power with my heavy right foot. At lower elevations the smoke is a lot less. There is just not as much air at higher elevations. At 10,00 feet is is not possible to see 30 pounds of turbo boost. We are currently on the return leg of a trip of about 6000 miles. Here at 1200 feet there is very little smoke and it is easy to see 30 pounds of turbo boost. As Jon advised check all when you are at lower elevation.

[johnbrowder]

OK, if Jon W says it, I buy it! Plus, that's what I really wanted to hear. By the time we get to TX we will be back at "normal" elevations, and I should have a pretty good idea if smoke is back to baseline. I will try to post a followup.

[AmeriStar]

You might consider changing your air filter. Most people neglect this simple but important change.

[Mark3101]

Has it happened on more than one tank of fuel? I have seen similar smoke when I got a suspected bad tank of fuel, and it went away after the next fill. My mileage suffered as well until the next fill up.

I would tend to think it is elevation related, but the above could also be the culprit.

[Lawrence M.]

John,


FWIW department, I had the same situation at high altitudes during my trip back to CA from Sturgis. It subsided as I came closer to sea level.

[Jon Wehrenberg]

While maintaining a clean air filter is important, if my memory is correct I think DDEC adjusts fuel flow based on the mount of air available for combustion. If I could remember where I read this I would post it. A dirty air filter on later model DDEC coaches results in less horsepower because of fuel flow restricted to compensate for reduced air flow, but does not produce the clouds of black smoke associated with a dirty filter on older engines.

DDECI had the ability to roll out clouds of black smoke upon rapid throttle application because the injectors were responding to the throttle position with no compensation for the amount of air or boost that was available. As a result a driver could punish surly toll booth employees with air rich with black smoke, but the downside was that in Colorado Springs pulling away from a traffic light was a slow painful smoke filled process until the turbo boost kicked in. Later DDEC versions corrected that issue.

[AmeriStar]

Yes it is important to have clean filters. 'Black' smoke from a series 60 during operation is NOT NORMAL at any altitude.
This is one of the negative's associated with increasing the 12.7's horsepower to 500+.
The DDEC does make adjustments for air density and temperature, but only as a reaction.
The initial first burst of fuel after each idle period, signals the ECM and adjustments are made from there to the air fuel ratios.
It is our experiance from out fleet operation, that simple things like air filters, are the best place to start a diagnosis for black smoke.

[travelite]

Here's the sensors on John's S60:

turbo boost (TBS)
air temperature (ATS)
coolant temperature
oil pressure
oil temperature
fuel temperature
timing reference
synchronous reference

My DD manual says this about the ATS: "The ATS provides necessary input for various functions such as varying hot idle speed, fan control, and injection timing which results in improved cold starts and reduced white smoke".

The DD manual says this about the TBS: "The TBS provides data to the ECM for use in engine fueling (smoke control)".

The way I understand it, for a particular throttle position and engine rpm, the ECM modifies its fuel delivery to achieve a particular boost pressure. If boost pressure is low, then more fuel. If boost pressure is high, then less fuel. If at altitude, where the mass of O2 is less, then more fuel, more heat, and more black smoke to achieve the desired boost pressure. If the air cleaner is clogged, resulting in less O2 mass, then more fuel, more black smoke, more heat. If the CAC is cracked resulting in less O2, then more fuel, more black smoke, and more heat.

[Gary Carmichael]

Kevin, When you speak of 12'7's are you referring to liters? MY engine is 14 liters but still, I think 500hp. Are some engines different liters and all the same HP? probably a dumb question.

[johnbrowder]

My air filter has about 5000 miles on it and looks clean.
Kevin, to be clear, I am not billowing black smoke. It is just a little puff on initial acceleration, as I continue to accelerate, I see no smoke, at a steady power setting I see no smoke. I have seen this little puff from day one with my 2003, and previously thoughout my ownership of a 2001. I just see more now than before.

From your statement, I read that ANY black smoke is abnormal. As a fleet operator, I am inclined to listen to what you say.

[travelite]

John, If you want some folks to listen to, post your question to the experts over on dieselenginetrader.com:

http://www.dieselenginetrader.com/diesel_talk/categories.cfm?catid=9

There are a couple of S60 techs over there who are absolute gurus on the DD S60. That's where I go for my S60 related questions. I don't own a fleet, but I think what you're seeing is normal 'altitude' smoke.

[AmeriStar]

Ok,
An initial puff of dark smoke from a cool engine is normal for 1 to 2 seconds. I guess my definition of BLACK smoke is different than dark smoke so it is probably normal.
It's our experience that dirty air filters contribute to 'smoking'. Our home base is at 4000 feet above sea level. A bus from our fleet is in Denver (5280 feet), Cheyenne (6150 feet) and Laramie (7165 feet) on a daily basis. When we see smoke, we usually have a dirty air filter.

The 12.7 litre engine is what I'm referring to when I say 12.7. The majority of 12.7's were delivered at a horsepower rating of 430/470. Increasing the HP rating uses more fuel and creates more heat and wear. Our stock 12.7's deliver a fleet average mpg, based on 2 million miles per year, of 7.1 in summer to 7.5 in winter.

The 14 litre engine is designed for 500 HP and delivers it with ease.

Just my 2 cents worth.

[johnbrowder]

We were at the end of a long day, approaching Durango, mix of up and down grades... nothing severe. I got the same beep-beep that signal low air pressure gives. I looked at the LCD display and it said: Stop, Mid 166 fault. I immediately pulled over, but did not shut down. The fault went away. No stored codes (Silver leaf), nothing visibly amiss in engine room. Looked in Prevost manual, but could not find "166". Carefully resumed journey, no issue.

Help!