diesel engine "odd" sizes - why?

[Toilet Duck]

Seasons greetings all,

Why is it that diesel engines are often odd numbers in capacity, e.g. 1.7, 1.9, 2.7 litres etc and petrols are normally even e.g. 1.4, 1,6, 2.0 litres etc?

I know this isn't always the case by any length, but as a very general sort of guide, diesels more often than not seem to fit into the "odd" size and petrols "even."

Why is this? I ask only for curiosity as it puzzles me!

I thank you!

[DannyVTS]

I don't know the answer, but this is something that i have always wondered too.

My mind was blown when VAG released that 2.0TDi lump

[RB5]

There's no real reason for this. I believe some diesel engines were orignally based on petrol engines, but with increased stroke to increase the compression ratio to a level high enough to ignite the diesel fuel. Since the numbers you see are rounded to the nearest 0.1L, this may be just enough to push it up to the next figure (e.g. 1.8L to 1.9L).

[davepoth]

This. The engine block used in the MGB is the same block as used in the B-series diesel, which is a popular power plant for canal barges.

[eliot]

davepoth said:

This. The engine block used in the MGB is the same block as used in the B-series diesel, which is a popular power plant for canal barges.

Which is where diesel engines should remain.

[mad4amanda]

Honda have a 2.2 CDTI

[Toilet Duck]

mad4amanda said:

Honda have a 2.2 CDTI

I didn't say it was set in stone, I emphasised that it was just a very general rule of thumb guide. As posted above by DannyVTS, VAG use a 2.0 diesel which is very common. However, historically it seems that diesels have tended to be "odd" in capacity and petrols "even."

[mad4amanda]

Toilet Duck said:

mad4amanda said:

Honda have a 2.2 CDTI

I didn't say it was set in stone, I emphasised that it was just a very general rule of thumb guide. As posted above by DannyVTS, VAG use a 2.0 diesel which is very common. However, historically it seems that diesels have tended to be "odd" in capacity and petrols "even."

Think your just mistaken really: 1100, 1300, 1500 and 1700 ford engines, 900cc fiat and Austin ,1.1 and 1.5 rootes, peugeot, simca and talbot petrols lots of 2400, 2800 and 3000cc diesels over the years.

[CraigyMc]

Toilet Duck said:

mad4amanda said:

Honda have a 2.2 CDTI

I didn't say it was set in stone, I emphasised that it was just a very general rule of thumb guide. As posted above by DannyVTS, VAG use a 2.0 diesel which is very common. However, historically it seems that diesels have tended to be "odd" in capacity and petrols "even."

Pug do a 1.6 diesel
BMW do a 2.0 and a 3.0 diesel
MB do a 2.2 diesel.

I think VAG still do their ancient 1.9, but other than that I can't think of any.

[powerstroke]

eliot said:

davepoth said:

This. The engine block used in the MGB is the same block as used in the B-series diesel, which is a popular power plant for canal barges.

Which is where diesel engines should remain.

Yes but why would you want the best type of IC engine in something that's limited to walking pace speed???, you would think they would be better with one of those gutless petrol engine thingys, diesel is mans power trucks, tractors, bulldozers etc petrol is for hairdressers..