Smallest Diesel Engine: How Tiny Can It Be?

Hello everyone,

A while ago, a post was made about the largest diesel engine, that massive "ship monster" motor with 100,000 horsepower. I want to explore the opposite: how small can a diesel engine be and still function while providing some reasonable amount of power?

While it's a rather theoretical question with no practical application in my case, I still find it to be an interesting topic.

I seem to recall reading somewhere (probably in the context of the tiny CDI from the Smart car) that it was stated that operation below 400...500 cm³ per cylinder is not feasible/was not possible, however, for example, the small 1.5-liter 4-cylinder engines from Renault are below this limit, and even the smaller Lombardini engines in the Enfield ( http://home.t-online.de/home/Beckedorf/enfield.htm ) are significantly smaller at 325 cm³, not to mention the Smart CDI (800 cm³, 3 cylinders).

Is this the lower limit, or is it possible to build a diesel engine with a displacement of 150 cubic centimeters or less?

What do you think?

Best regards,

January.

Hi Jan,

This favorite child of Ferdinand Piëch back then, the "1 Liter" cigarette, had a 300cc single-cylinder SDI engine. It actually ran, or was it only 250cc? Anyway, there are also the Hatz single-cylinder diesel engines, which are quite small. The Enfield Taurus motorcycle (more or less) uses a 300cc single-cylinder diesel engine, and let's not forget the engines from model making; most of those are diesels (although with very little power). In principle, the diesel process has its limits in terms of how much compression can be achieved. The smaller the engine, the more difficult, pointless, and especially expensive it becomes to use a diesel because it requires a high-pressure pump.


Matthias.

Hi,

The Enfield has the smallest engine size at 325cc - I've linked it in the text above so that it can be clicked on.

I had completely forgotten about the "1-liter car" – that was also in a similar direction.

The model engines probably don't have fuel injection, or am I mistaken (I've never worked on anything like that before)? That would make them something of a hybrid... isn't that also called a "glow plug" system?

Best regards,

January.

Model engine motors are carburetor engines. However, it should be noted that most of them are not diesel engines. Most are glow ignition engines. This means that a heating element (glow plug) is heated by applying an electric current. Once the engine is running, this glow plug continues to heat up due to the combustion temperature and provides the necessary ignition. In a true diesel engine, there is a counter-piston that is adjusted to change the compression. Then, everything works like in a 2-stroke diesel engine, after the compression has been appropriately adjusted and the device has ignited! But it's all based on carburetor technology.

Single-cylinder engines, and don't forget the engines from model making; almost all of those are diesel engines (although they have very little power).

Okay, I think 3.5 horsepower from 10cc is anything but a very small amount of power .
By the way, these are carburetor ignition engines, NOT diesel engines!


The limiting size for a diesel engine is the injection system!!

With such small engine displacements, it's simply not possible to measure the fuel injection volume with sufficient accuracy. Chamber diesel engines still have an advantage in this regard because the mixture formation is less dependent on the injector (i.e., atomization).
Back then, Mercedes and Bosch spent a long time figuring out how to finally get the diesel engine into passenger cars.

CU Gremlin.

Hello,

I believe it's just a matter of acceptable effort. Taifun produced diesel model engines with a displacement of 2ccm. Glow plug engines are available with a displacement of 0.16ccm. The problem is having a "proper" injection system. Today, this can be manufactured using nanotechnology with virtually any level of effort and cost. The question is, who needs something like that?

Best regards,
Christian.

Hello,

I believe it's just a matter of acceptable effort. Taifun produced diesel model engines with a displacement of 2ccm. Glow plug engines are available with a displacement of 0.16ccm. The problem is having a 'proper' injection system. Today, this can be manufactured using nanotechnology with virtually any level of effort and cost. The question is, who needs something like that?

Best regards,
Christian

Glow plugs have nothing to do with diesel engines. As I said: the glow plug is externally energized and then continues to glow due to the combustion temperature. If the heating element burns out while the engine is running, the engine will stall.
'Purebred glow engines (as I mentioned, with compression adjustment) were available in East Germany back then, starting from a displacement of 2.5ccm, manufactured by Zeiss. I don't think it can get much smaller than that, because the combustion would become even less clean. These engines already leaked oil quite badly. And their ease of ignition wasn't exactly great either.'

IIRC, the Taifun engine also only uses a 'glow plug,' meaning it receives a pre-mixed fuel and then ignites it using compression.
For a true diesel engine, a proper fuel injection system is necessary.

I'm just wondering how much pressure nanotechnology can probably withstand .

CU Gremlin.

Hello,

Why shouldn't we be able to design a high-pressure piezoelectric pump/nozzle? It doesn't necessarily have to operate in the kilobar range. There are also inkjet printers that use lower pressures.

The Typhoon engines were self-igniting due to the compression pressure (adjustable with counter-pistons, no glow plug required). They didn't have fuel injection, but instead used a "carburetor" for mixture formation.

Best regards,
Christian.

Gremlin wrote:

IIRC, the Taifun is also just an "igniter," meaning it receives a pre-mixed fuel and then ignites it using compression. For a true diesel engine, a proper injection system is absolutely necessary. I'm just wondering how much pressure nanotechnology can probably withstand . CU Gremlin

At the very latest, when a fuel molecule gets stuck and lodges in the nozzle opening, that's when things stop working.

It gets even worse when a fuel molecule collides with the bottom of the piston at one end during injection and remains stuck in the nozzle at the other end. People, please be reasonable and take this seriously.

Hi,

Before we start building microscopic motors, I want to take a step back and reconsider things. My focus was on motors that could deliver at least 1 to 10 horsepower, meaning they could be used to power larger objects like vehicles or generators.

Best regards,

January.

Hello,
"These types of engines have been around for a long time; brands like Hatz, Yanmar, and Honda, for example, use them as power sources for generators. Why would you need a diesel engine with such low power output? Is it due to fuel consumption? Diesel engines typically have roughly three times the peak pressure compared to gasoline engines, which is why they are also more robust (and heavier) in construction. A significant advantage is the much lower fuel consumption at partial load. At full load, there isn't a huge difference between a diesel and a gasoline engine."

Best regards,
Christian.

Hello,

Sure, here's the translation:

"Here's an example."
http://www.yanmar.nl/products/industry/indusrial/la_lee/la_lee_series.htm

or
http://www.hatz-diesel.de/deutsch/company/frame1.htm

or
http://www.justgenerators.co.uk/pages/Honda_EX4D.htm

Best regards,
Christian.

Why shouldn't we be able to design a high-pressure piezoelectric pump/nozzle? It doesn't necessarily have to operate in the kilobar range. There are also inkjet printers that use lower pressures.


Okay, but you always had to maintain a compression pressure above the end pressure AND be able to reliably resist the ignition pressure!

CU Gremlin.

Hi,

Quote:

Why would it be a diesel engine given the low power output?

That's not the point... I don't want to build anything or buy anything. It's more about the fundamental discussion.

Best regards,

January.