Interesting car tidbit: The inventor the diesel engine was originally inspired by a simple fire starting gadget such as this one.
This seems to imply a diesel engine could work using a simple carburetor method, rather than direct fuel injection. Have there been any carbureted diesel car engines?
Charles, Boyle and Gay-Lussac walk into a bar. Clearly this is an ideal joke. But, after all these jokes are the lawâŠ
How would the ignition timing be controlled in a carbureted diesel?
I suspect that would be the major reason it wouldnât work.
Diesels are not carbureted. They donât need a narrow air fuel ratio to run properly. They almost always run lean - excess air - so they have no throttle plate. The speed znd load varjes by adding more or less fuel. Ignition happens when the temperature of compression rises high enough to ignite the mix and the timing is done by when the fuel is injected.
There is one type of diesel that uses a carburetor.
Fuel injection goes WAY back with diesel engines, starting with âair blast injectionâ in 1890:
Air-blast injection - Wikipedia
Direct injection with âunit injectionâ was patented in 1911:
Unit injector - Wikipedia
A blown oil seal in a turbo acts as a carburetor. The engine starts running off of its own oil.
I think this method doesnât work well because the ignition can take place too soon, so that ignition is happening while the piston is still going up. This reduces engine power!
Ingteresting. What is that engine used for?
Simple physics dictates the ignition would occur near the top of the compression stroke, which is approximately the correct time. But you are right that this may not be the exact time in the cycle for an automobile engine to yield the best power/mpg/emissions possible.
That glow-plug engine isnât what Iâd call a diesel, I donât think it would work without the glow plug, while a warmed-up diesel doesnât need one.
Glow plug (model engine) - Wikipedia
The small model-plane engines I used to enjoy as a kid required a special fuel. It smelled like gasoline w/some sort of additive, no a diesel odor. I think it might have been nitro-methane. They wouldnât start if glow plug failed, but they never stopped working once I got them started unless the plane ran out of gas or it crashed, the latter being the more common way the flight ended ⊠lol âŠ
An automotive diesel engine doesnât âneedâ a glow plug to start, even when cold. It is an aid, and greatly helps in start up emissions. This could be argued in certain climates, but as long as the batteries are strong enough, the engine will build the heat to start.
Yeah, thatâs not controlling timing, thatâs UNCONTROLLED timing. Exactly what I meant.
That is one reason diesel engines are built strong and heavy. They run a bit like a gas engine in detonation.
Yeah, agreed. But Iâd expect that they still need some control over ignition timing. At altitude, thin air would ignite later than sea level air, youâd also presumably want some different ignition at different engine speeds.
A carbureted diesel would allow none of this and I presume thatâs the reason they donât exist in the mainstream.
Years ago I suggested carburatediesel would be.tter than fuel injection because more fuel would be surrounded by O2 molecules.
Same with gasolinengines today.
Plus how much energy is expended compressing the fuel to inject against high cylinder pressures?
Once these engines are started, electric power to the glow plug is disconnected.
The diesel engine , named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is called a compression-ignition engine (CI engine).
Therefore, model airplane, boat, or car engines fall under the definition of a diesel.
Diesel is how the fuel is ignited, not what fuel is used.
Nope. The ignition in a glow plug engine comes from the continuously hot glow plug wire, which also is made from platinum, adding catalytic effects enhancing ignition. The Wikipedia article explains this:
" The glow plugs used in model engines are significantly different from those used in full-size diesel engines. In full-size engines, the glow plug is used only for starting. In model engines, the glow plug is an integral part of the ignition system because of the catalytic effect of the platinum wire. The glow plug is a durable, mostly platinum, helical wire filament recessed into the plugâs tip. When an electric current runs through the plug, or when exposed to the heat of the combustion chamber, the filament glows, enabling it to help ignite the special fuel used by these engines. Power can be applied using a special connector attaching to the outside of the engine, and may use a rechargeable battery or DC power source."
Diesel engines depend only on compression heat for ignition.
Also, the compression ratio in glow plug engines (7.5:1-9:1) isnât high enough to initiate combustion without the hot glow plug.
That is the most important statement about diesel technology.
Gasoline diesels have been and are being tested. With direct injection technology, the cold engine can be started with a spark and once warmed, continue as a compression injection engine making it a gasoline diesel. The very high compression ratios make the engines more fuel efficient. The direct fuel injection is the âtimingâ for the combustion.
Ainât nothinâ new.
My 1969 gasoline Ford County Sedan station wagon dieseled all the time!