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Topic: Generator Exhaust Soot (Read 733 times) previous topic - next topic

Generator Exhaust Soot

How much generator exhaust soot is normal?  Any?  On my last two coaches, the exhaust pipe went straight out and the FT angles toward the ground.  So maybe they all sooted and I just did not realize it.  The FT gen set does not have smokey exhaust but does have a fair amount of soot on the ground after a day or longer.  Other than that it starts and runs great.  Unlike my Aqua Hot...
Luke & Sandy (still many work years to go...)
1999 U320 36 Build #5387
2013 Jeep Wrangler Unlimited
Previous 1997 Winnebago Vectra Grand Tour 35WQ major interior remodel
Previous several SOB trailers, Class C, fifth wheels.

Re: Generator Exhaust Soot

Reply #1 –
My generator exhaust goes straight out the side, so if it does make soot I never noticed.  It doesn't smoke at all.

Black soot in most cases indicates a "rich" mixture.  Dirty air cleaner?  Worn injectors?

What engine do you have on your generator?

How many hours on your generator?

We have 1635 hours on our OEM Kubota 4 cyl diesel engine.  It has never had any work done to it, except normal maintenance.

How many hours is considered a "high" number for generator engines?  I don't know...

Also, see this article on "wet stacking" - something I had never heard of:

Diesel Generator Wet Stacking - What Is It & How to Prevent It?
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Generator Exhaust Soot

Reply #2 –
According to Powertech, this unit was built in 1997 with an Isuzu 3LD1 engine and has a 02GEN10TCGE generator end on it.  It has 1,178 hours on it.  The PO hardly used it, so the last service was a while ago...
Luke & Sandy (still many work years to go...)
1999 U320 36 Build #5387
2013 Jeep Wrangler Unlimited
Previous 1997 Winnebago Vectra Grand Tour 35WQ major interior remodel
Previous several SOB trailers, Class C, fifth wheels.

Re: Generator Exhaust Soot

Reply #3 –
Ours had about 1450 hours when I pulled it to change mounts and redo the compartment,the bearing was dry so we put a new one in,also installed new mounts,made a difference,would,nt hurt to replace the end bearing.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Generator Exhaust Soot

Reply #4 –
My Isuzu soots a bit on the ground but not excessively, no visible smoke after initial startup. My Kubota did a little as well. Clean air filter, may be a tad rich but my in house mechanic calls it a non issue. These power techs and kubota with Onan are not likely to be worn out by the typical motor home owner. My Kubota/onan had 7500 hours on it and Dave M said with good maintenance it should get 7500 more. I had trust in Dave on gen set opinions.
Dub McBride 1996 270

Re: Generator Exhaust Soot

Reply #5 –
Quote from: Chuck & Jeannie –
My generator exhaust goes straight out the side, so if it does make soot I never noticed.  It doesn't smoke at all.
Black soot in most cases indicates a "rich" mixture.  Dirty air cleaner?  Worn injectors?
How many hours is considered a "high" number for generator engines?  I don't know...
Also, see this article on "wet stacking" - something I had never heard of:
Diesel Generator Wet Stacking - What Is It & How to Prevent It?
Chuck,
Your exhaust and ours go out the side and while ours does not smoke at the altitude where we live, it will like all others that are non-turbo, up at altitude like Yellowstone. I've even had a tent camper bang on our door because of the smell. 

There is no such thing as a "rich" mixture in a diesel. The person who wrote the article you linked to has some points correct but misses the boat entirely when it comes to air/fuel ratio. Their quote: "In order for a diesel engine to run at maximum efficiency, it has to maintain an exact air-to-fuel ratio just like all other internal combustion engines."  The air/fuel ratio (by weight) constantly changes in a diesel engine depending on the engine load. While at full throttle, a diesel may use about 14 parts of air to 1 part of diesel (by weight), but it may be as high as 140 parts of air to 1 part of diesel at idle. This is why diesel cars were left running all night at ski slopes as they burned very little fuel idling all night and the owner didn't have to worry about starting in sub-freezing temps in the morning. This also gave diesel race cars at Le Mans a big advantage during yellow flag laps as they had a very high air/fuel ratio where the gasoline cars had to maintain an approx 14 to 1 A/F ratio.

So, diesels don't have a butterfly throttle and from the air cleaner to the intake valve or port, the passage is open. The injection pump is the throttle and as it injects more fuel, the engine speeds up, produces more power, etc. This concept is difficult for some to understand.

Black smoke is unburned diesel producing carbon out the exhaust. It may be caused by poor injector pattern, high altitude where the oxygen molecules are further apart, low compression, intake restriction (air cleaner) or over fueling where more fuel is injected than the engine can burn. Examples would be on a grade where the coach won't accelerate but the operator (on the mechanical injected diesels) pushes the throttle down further producing black smoke out the exhaust.

You generator should not "wet stack" as the thermostat will keep engine temps up to normal and internal friction, fan, etc. will produce enough heat to prevent W/S.

No wear limit on the generators. Scheduled oil changes should keep it in good shape the life of the coach and more. Generally, a worn out diesel just gets harder and harder to start. Bore wear is the cause, usually because the owner never changed the oil. I've purchased MBZ diesels in Germany with engines that had so much bore wear that they would not start even with glow plugs in winter that I would have to park it well above the road and coast it a couple blocks downhill in second gear before it would run. You could not park it for more than two hours or it would not restart. (Naturally, it got an overhaul before shipping back.} Once running, it got excellent fuel mileage, etc. The seller had cleaned the engine so it looked like new but the telltale was crankcase pressure forcing oil out the dipstick that gave it away.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Generator Exhaust Soot

Reply #6 –
Both of my coach generator will leave a little soot on the ground after a day or so of running. 

It was interesting starting the generator when we were at 7,000 ft.  Generator stubbled for a little while, blew a little smoke out and then settled down.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago