Why do big diesels belch black smoke - Page 2 - PeachParts Mercedes-Benz Forum

Cr from Texas · #16 10-02-2009, 05:21 PM

Big trucks, trains etc. belch heavy smoke under heavy load. Excess fuel trying to keep up speed or even accelerate. I would imagine a MB trying to pull a heavily loaded trailer would do the same.

swheele2 · #17 10-02-2009, 06:30 PM

Quote:

Originally Posted by lkchris

All vehicles with diesel engines sold in USA are REQUIRED to be fitted with a diesel particulate filter beginning model year 2007. ULSD is the concurrent requirement to provide protection to these filters. My GL320CDI produces no smoke and at 21K miles there is zero soot on the chrome exhaust extensions.

Black smoke is of course visible particulates, and there shouldn't be any emanating from MY 2007 and newer diesels, even the big trucks.

Sulfur content should have some effect on NOx emissions, but I do think the main reason of transitioning to USLD is to avoid spoiling new particular/soot filters.

cessna5354 · #18 10-02-2009, 07:18 PM

I think most of the trucks belching black smoke are old Detroit two cycle, which if you do not keep your foot out, they will "over fuel" and blow it our as unburned fuel. At start up I have minimal smoke, and around town if I mash the throttle, I will belch. Keeping a light touch will minimize the unburned fuel. I think the DDEC controlled engines and not as prone.

As, Kerry indicated watch out on a cold start however. I am able to preheat with the hydronic heater within the bus, with a circuit routed thru the engine block. I wake up warm & toasty, as does Mr. Detroit. That has been tested to 0*Deg.

rscurtis · #19 10-02-2009, 08:13 PM

The old Detroit 2-cycles are virtually extinct in OTR trucks. Keep in mind that some of the smoke you see could be from malfunctioning EGR systems- the law of unintended consequences. Any on-highway diesel built after Jan. 1, 1994, should not emit any visible smoke.

moon161 · #20 10-02-2009, 08:32 PM

Overfueling (insufficient air) results in incomplete combustion. In gassers, this gives a 'sweet' exhaust, in diesels, you get lots of soot (black stuff).

Brandon_SLC · #21 10-02-2009, 08:32 PM

Around here, almost everybody modifies their Turbodiesel pickups. They still belch black soot, but not as much as before the low sulfur fuel came out.

My next door neighbor has a Ford super duty that seems to be unmodified, because even under heavy load you barely see a wisp of smoke.

I am not sure if buy truck you meant semis. Most of them have cleaned up a lot too. Going up the big mountain passes in California you don't see the black smoke coming out of semis like you used too. I think they'll give you a ticket for that in CA these days. Last time I was down there I noticed the only vehicle dumping lots of soot going up Tejon Pass was a train.

I've been amazed how clean my 240D runs, because in the old days our 300SDs left black exhaust under full load.

Just thought of something. I'm sure all of us have now seen the videos of the Fins in the Super Turbo Diesels. They put out tons of soot, even though they are on ULSD.

Shawn T. W. · #22 10-02-2009, 09:19 PM

Quote:

Originally Posted by UriahT

I've seen trucks still belching smoke.
It must be that their max fuel flow rate is less restricted.
Similar to what our turbo cars could do if the IP rack limiter and alda were removed.

Most of these trucks also have manual transmissions, which means they can have very high fuel flow and high revs at the same time, which most of us don't do with automatics. The older trucks also have near no emissions controls, which means more particulate exhaust.

Our cars CAN belch heavy black smoke if they're not tuned well, or if someone unrestricts the fuel flow by the steps above. Why you'd want to, outside of a modest performance increase, I don't know. Black smoke=wasted fuel.

High rev's in a big truck? come on now! My cummins 14 liter 6 cyl was limited to 1800 rpm except in top gear only 1600 rpm

cessna5354 · #23 10-03-2009, 09:45 PM

Any on-highway diesel built after Jan. 1, 1994, should not emit any visible smoke.[/QUOTE]
The efficiency improvements in the newer engines will keep the 2 stokes off the road.
You are right, but I still see some COE's, which havn't been built in that time frame, and others.

I agree that with everything operating as it should, difficult to belch the blk smoke as years ago.

bobodaclown · #24 10-03-2009, 11:37 PM

Sulfur is a big contributor to acid rain. (Sulfuric acid). But it does increase the lubricity of the fuel.