Re: What exactly makes a diesel smoke under a load

Posted by B-maniac on August 24, 2006 at 19:01:11 from (207.241.134.189):

In Reply to: What exactly makes a diesel smoke under a load posted by carpenter in belmont on August 24, 2006 at 16:43:51:

Used to rebuild and "dyno-test" these pumps for Diesel Equipment Sales-St. Louis Michigan. You have to remember,a diesel is a whole different animal than a gas engine.First of all the intake air way is always WIDE OPEN and therefore it's the amount of fuel and timing of injection that governs rpm and power.Even when the throttle is wide open with no load,it injects very little fuel.(fast idle)(no smoke) When the throttle is wide open under no load the governor weights are thrown all the way out,closing the fuel volume valve down--no smoke. Now,drop a plow in the ground and rpm drops,the weights come back in,opening up more fuel volume for more power. You have to understand,it has wide open air all the time and fuel oil burns dirty. It's just that at idle or fast idle it isn't injecting enough to smoke OR make any power. If you want power you have to have fuel and lots of it because remember,it has all the air it needs all the time.So contrary to popular believe,it ain't running "rich" when it smokes,rather it's running "lean" when it don't! People aquate black smoke with running rich,not ideal mixture for making power.Thet's correct,but only on a gas engine.Why do 1000 hp super-stocks smoke so bad and make so much power if black smoke = to rich to make power? The more fuel,the more power,up until you reach the limits of the stock intake manifold.THEN you put on the turbo and force even more AIR in so now you turn up the volume in the pump and the sky's the limit.The more fuel, the more power,and it will smoke because it's FUEL OIL. The computer controled engines were developed for emmissions standards and fuel mileage. You make a larger engine and run a leaner pump with infinite control capabilities and it doesn't smoke as much because it overcompensates for load with more cubic inches instead of more fuel. Go to a late model diesel pickup pull. Computers and all,the ones that full pull are the ones that smoke like a super stock tractor! Ineffecient? To much fuel for the air? I think not. The more power,the more fuel..the more fuel, the more smoke! It's the way diesels are. They don't have a throttle as most people think of it,they have a valve in the pump that controls fuel volume,dictated by a governor that senses engine speed and load,in turn connected by linkeage to an operators control. Computers do it all electronically fed by many inputs from the engine and drive train. Get and read any book on the theory and design of the diesel engine.

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