OP
dodge man
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I was trying to visual the intake path of a diesel. I take it that their is a intake manifold and the end of it is open to the outside air through the air cleaner.
Oil & Fuel General diesel question
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You can not compare the governor of a gasengine with the one of a Diesel. Also the Diesel has a kind of...sitting i the injection pump.
A Diesel engine is more complicated then a Gasoline engine but has higher torque at same hp. On the other side you can not compare an US gasser with 200 SAE hp in a car with a 55 DIN hp gasser in a european car or a 55hp Diesel.
The Diesel You can call a selfignition.
The Diesel only sucks clear air, that is the reason you always must have an airfilter.
The compression ratio is 20:1, so the air will get really hot. Guess 1200ｰC but I am not sure about...itｴs too long that I have learned about.
The ignition nozzles spread in the fuel into this hot air (120 bar pressure at the nozzls, not sure about measurements in US..pounds /sqinch?) and the fuel will explode.
Our teacher stated: "The Ignition pump of a Diesel engine has to distribute the right amount of fuel to the right place at the right time !"
A Diesel needs an expensive fuelpump, and nozzles, but it is more economic on fuel then a gasser is. For normal it has a longer lifetime.
For Europe a Diesel engine always has made sense, but You can not compare the USA cars with the european. You have speedlimit of 55 mph and engines of 3-5 litres.
On Interstates we have no speedlimit but small cars with 1-2 litres which als can reach 200000 miles with ease, if they always ran long distances..
A Diesel engine is more complicated then a Gasoline engine but has higher torque at same hp. On the other side you can not compare an US gasser with 200 SAE hp in a car with a 55 DIN hp gasser in a european car or a 55hp Diesel.
The Diesel You can call a selfignition.
The Diesel only sucks clear air, that is the reason you always must have an airfilter.
The compression ratio is 20:1, so the air will get really hot. Guess 1200ｰC but I am not sure about...itｴs too long that I have learned about.
The ignition nozzles spread in the fuel into this hot air (120 bar pressure at the nozzls, not sure about measurements in US..pounds /sqinch?) and the fuel will explode.
Our teacher stated: "The Ignition pump of a Diesel engine has to distribute the right amount of fuel to the right place at the right time !"
A Diesel needs an expensive fuelpump, and nozzles, but it is more economic on fuel then a gasser is. For normal it has a longer lifetime.
For Europe a Diesel engine always has made sense, but You can not compare the USA cars with the european. You have speedlimit of 55 mph and engines of 3-5 litres.
On Interstates we have no speedlimit but small cars with 1-2 litres which als can reach 200000 miles with ease, if they always ran long distances..
OP
dodge man
Super Star Member
I did a little reading on Wikipedia, and that helped my understanding a little.
A diesel has no air restriction after the filter to the valve. It will ignite all air fuel ratios. A large part of the higher mpg's you get with a diesel are from not having to draw a vacuum due to no throttle. Creating that much vacuum takes a LOT of power. You know how many watts a vacuum cleaner draws, now imagine 10x the amount. The power in a diesel is totally regulated by the amount of fuel with the amount of air being about constant.
People say that diesel are more complicated. Hogwash. If you compare a non-turbo diesel to a non-turbo gas engine they are identical in complexity. The differences are in how the air/fuel in each is managed. A single barrel updraft may have been less complex than a roosamaster pump, but not when compared to a computer controlled fuel injected modern engine. That old complexity saw has been strummed since the '50's and it hasn't been accurate since the early 70's!
The new common rail diesels ARE quite complex, but so is a fuel injected gas engine today.
Soundguy
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NO.. as others have said.. the intake manifold is a striagh shot ... it's open.. no butterfly. throttle controls fuel delivery only... that in turn controls power and speed. this is on naturally aspirated engines.. on units with turbo or superchargers.. there is extra air available.. thus more fuel can be used.. within reason.
think of a iesel as a big air pump..
soundguy
Here's my half-dollar's (as opposed to 2 cents' 
) worth concerning the operation of a diesel engine:
In normally aspirated engines (non-turbo, non-computer), when you change the "gas pedal" (or lever, on a tractor) on a diesel engine, you are changing the amount of delivered fuel only.
A gas engine would run at full speed if it weren't for the "throttle." Think of the British definition: "throttle" means "to choke," as in, "I'll throttle you!"
The gas pedal in a gas engine controls only the amount of air that is allowed into the engine, through the throttle plate; as the airflow increases, more fuel is sucked in through the carburetor along with it, resulting in more rpm and power (more air + more fuel).
A diesel's (mechanical) injector pump is built like a Swiss watch; each cylinder has its own dedicated injector and, generally, hydraulic ram. The ram (like a squirt gun) is necessary to provide sufficient pressure to overcome the very high pressures inside the cylinder while it's under compression. As you press down on the "gas pedal" (or raise the lever) on a diesel, you are actuating a complex bit of machinery that increases the length of the stroke of each hydraulic ram, resulting in more fuel delivered to each injector.
In a diesel, the air path is, in fact, wide open all the time. The only control is for fuel delivery on each stroke of the piston. (This is why diesels are very quick to develop problems when the air filter gets dirty!)
Rudolph Diesel was a thermal dynamicist who was convinced that an internal-combustion engine could be made to be more efficient than what was currently available in steam or gasoline engines of the day, that is, around the turn of the century. His idea was the compression ignition engine, or, as we call it today, the "diesel." (That's why diesel-rated oils carry a "C" designation, for "compression ignition," as opposed to "S" designated oils, for "spark ignition.")
It's interesting to note that Rudolph's invention of a 'compression ignition' engine had been demonstrated with a proof-of-concept design some years before the technology was developed to be able to inject the fuel on a continuous basis into the high-pressure cylinder.
The company that successfully developed this sytem was named "Bosch," and for years, all diesel injector pumps were made under license based on the original Bosch design.
The main reasons diesel engines are more efficient is because a) they use a higher compression ratio, and b) have a much longer stroke on their pistons, extracting more mechanical energy on each firing, with less waste heat. This is also why diesels are so well-adapted to turbochargers, as their exhaust gas temps are considerably cooler than on a gas engine, resulting in less stress on a turbo's bearing as well as on the oil. (I hate to differ with John_Bud, but diesel cars are all equipped with add-on vacuum pumps, to make up for their lack of ability to develop vacuum --to run heater controls, power brakes & such-- but they're still much more efficient in terms of mpg, even though being saddled with the additional load of their vacuum pumps.)
Modern diesel engines are equipped with electrically-operated injectors (along with extremely high fuel pressures) to control fuel delivery by computer. VW engineered a breakthrough when they successfully devloped a system that could not only control the amount of fuel delivered, but also its timing... Hence, the TDI diesels. (Mechanical diesel injector pumps are mechanically set & fixed as to their injection timing, and do not normally ever change unless something breaks or loosens up.)
Yeah, I'm a diesel fanatic... hope this helps some and doesn't offend anyone; mistakes are solely the responsibility of the author.... Comments? Additions?
) worth concerning the operation of a diesel engine:In normally aspirated engines (non-turbo, non-computer), when you change the "gas pedal" (or lever, on a tractor) on a diesel engine, you are changing the amount of delivered fuel only.
A gas engine would run at full speed if it weren't for the "throttle." Think of the British definition: "throttle" means "to choke," as in, "I'll throttle you!"
The gas pedal in a gas engine controls only the amount of air that is allowed into the engine, through the throttle plate; as the airflow increases, more fuel is sucked in through the carburetor along with it, resulting in more rpm and power (more air + more fuel).
A diesel's (mechanical) injector pump is built like a Swiss watch; each cylinder has its own dedicated injector and, generally, hydraulic ram. The ram (like a squirt gun) is necessary to provide sufficient pressure to overcome the very high pressures inside the cylinder while it's under compression. As you press down on the "gas pedal" (or raise the lever) on a diesel, you are actuating a complex bit of machinery that increases the length of the stroke of each hydraulic ram, resulting in more fuel delivered to each injector.
In a diesel, the air path is, in fact, wide open all the time. The only control is for fuel delivery on each stroke of the piston. (This is why diesels are very quick to develop problems when the air filter gets dirty!)
Rudolph Diesel was a thermal dynamicist who was convinced that an internal-combustion engine could be made to be more efficient than what was currently available in steam or gasoline engines of the day, that is, around the turn of the century. His idea was the compression ignition engine, or, as we call it today, the "diesel." (That's why diesel-rated oils carry a "C" designation, for "compression ignition," as opposed to "S" designated oils, for "spark ignition.")
It's interesting to note that Rudolph's invention of a 'compression ignition' engine had been demonstrated with a proof-of-concept design some years before the technology was developed to be able to inject the fuel on a continuous basis into the high-pressure cylinder.
The company that successfully developed this sytem was named "Bosch," and for years, all diesel injector pumps were made under license based on the original Bosch design.
The main reasons diesel engines are more efficient is because a) they use a higher compression ratio, and b) have a much longer stroke on their pistons, extracting more mechanical energy on each firing, with less waste heat. This is also why diesels are so well-adapted to turbochargers, as their exhaust gas temps are considerably cooler than on a gas engine, resulting in less stress on a turbo's bearing as well as on the oil. (I hate to differ with John_Bud
, but diesel cars are all equipped with add-on vacuum pumps, to make up for their lack of ability to develop vacuum --to run heater controls, power brakes & such-- but they're still much more efficient in terms of mpg, even though being saddled with the additional load of their vacuum pumps.)Modern diesel engines are equipped with electrically-operated injectors (along with extremely high fuel pressures) to control fuel delivery by computer. VW engineered a breakthrough when they successfully devloped a system that could not only control the amount of fuel delivered, but also its timing... Hence, the TDI diesels. (Mechanical diesel injector pumps are mechanically set & fixed as to their injection timing, and do not normally ever change unless something breaks or loosens up.)
Yeah, I'm a diesel fanatic... hope this helps some and doesn't offend anyone; mistakes are solely the responsibility of the author....
Comments? Additions?number two
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Let's not forget that diesel fuel contains more BTU's than gasoline,adding to the efficienty.Too bad it costs a buck more now-was sure great all them years with our M-B 240D and Chevy 6.5 pickup,when diesel was cheaper, even though I know it's a supply/demand thing now. Yeah,I've been a diesel nut for a long time also.
(I hate to differ with John_Bud
Yeah, I'm a diesel fanatic... hope this helps some and doesn't offend anyone; mistakes are solely the responsibility of the author....
You shouldn't hate to differ!
I didn't say that diesel don't have vacuum pumps. I said they don't have throttles, thus they don't generate vacuum "in the engine". The generation of vacuum takes a good bit of energy and there is an efficiency gain from having an open air track. I didn't mention the other aspects as it was already getting too verbose. (I have an issue with verbosity...
)By the way, the long stroke. It's not an aspect only of diesels. In fact, many gasoline engines have identical strokes as diesels. It's more of a design aspect based on target purpose. The slower the target rpm, the longer the stroke can be. Yes, diesels gain from it, but so do gasoline engines! Yeah, a nit, but when your as full of verbosity as I am you pick at them...
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Keep in mind that the diesel system fuel control is a closed loop system. The dynamics of closed loop systems can become extremely complex. We set up servo systems with feed forward as well as feedback and fuzzy logic to regulate speeds of servo motors very precise during load changes.
When the tractor encounters a hill or other resistance (extra load) at a given throttle setting the engine must slow down just a bit in order to generate the error that causes the extra fuel. This following error will vary depending on many factors. The error will be larger in mechanical systems since the power of a microprocessor is not available to apply sophisticated algorithms that can't be done mechanically. At least not at a reasonable cost.
In other words it is normal for the engine to slow just a bit under increased load. If the load is too extreme and the engine can't match the power needed at the given RPM set by the throttle lever, then it will be out of control and slow more than normal or even stall.
When the tractor encounters a hill or other resistance (extra load) at a given throttle setting the engine must slow down just a bit in order to generate the error that causes the extra fuel. This following error will vary depending on many factors. The error will be larger in mechanical systems since the power of a microprocessor is not available to apply sophisticated algorithms that can't be done mechanically. At least not at a reasonable cost.
In other words it is normal for the engine to slow just a bit under increased load. If the load is too extreme and the engine can't match the power needed at the given RPM set by the throttle lever, then it will be out of control and slow more than normal or even stall.
Redneck in training
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In the past the limitation of the diesel engine was the minimum amount of fuel delivered to the cylinder. In other words the problem was manufacturing of pump able to deliver small volume of fuel. Therefore old diesel engines used to have large volume per cylinder. The weight of the large piston limited rpm typically to about 2000 to 2500 rpm. Then advances in precise manufacturing of small pumps (electro spark erosion machining comes in mind etc) allowed designing diesels with much smaller cylinders and thus higher rpm. Later on advances in electronic injection allowed for precise measurement of even smaller volume of fuel and also timing based on rpm, throttle position, temperature, load etc to design diesel engines that behave more like gassers except they have much lower fuel consumption and high torque. Modern 80 HP diesel feels about the same at 150 HP gasoline engine with the exception of maximum speed (assuming the same car). 24 hours in Le Mans was won by a diesel.