Engine size question

[daimatt]

This is a question that I have been thinking about for a while and although things have changed I'd still like to know if there is an answer.

Why are most petrol engined cars even sizes, for example, 1.2, 1.4, 1.8, 2.0 etc. etc..... and most diesel engines odd sizes, for example, 1.5, 1.7, 1.9?

I know that now there are a lot of diesel engines that are the same size as petrol now but it does seem a common thing.

I hope it makes sense as a question

[Gizmo!]

Sometimes it's taxation - in some countries cars "under 1500cc" or "under 2000cc" get better tax rates, so you get a clustering around 1496cc or 1997cc or whatever.

But mostly it's marketing and convenience. Why would you want the 1.425 model or the 2.136 model? 1.4 and 2.1 are easier.

There are some notable exceptions of course: the Ford Sigma engine was 1.25, the Mini 1275, Alfa 1750 (and new MultiAir 1750 TBi)...

[bikemonster]

It's because of the difference in the way capacity is calculated for compression (diesel) ignition engines as opposed to the calculation for spark capacity engines.

Basically, the spark plug intrudes into the combustion chamber and reduces the available capacity. This a 1.9 litre diesel engine equates quite tidily to a 1.8 litre petrol engine, even when made with the same block.

[Gizmo!]

Gizmo! said:

Sometimes it's taxation - in some countries cars "under 1500cc" or "under 2000cc" get better tax rates, so you get a clustering around 1496cc or 1997cc or whatever.

But mostly it's marketing and convenience. Why would you want the 1.425 model or the 2.136 model? 1.4 and 2.1 are easier.

There are some notable exceptions of course: the Ford Sigma engine was 1.25, the Mini 1275, Alfa 1750 (and new MultiAir 1750 TBi)...

Did you read the question? Divvy.

[daimatt]

^^^ thanks for the attempt anyway Gizmo.

Thanks for the reply. So the newish 2.0 diesel Audi's would make a 1.9 petrol engine if the same block were used?

[Ricky_M]

I thought the Peugeot 1905cc engine block was used in Petrol and Diesel engines?

[Papa Hotel]

I asked this a while ago, I don't think there was a definitive answer.

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[monthefish]

daimatt said:

This is a question that I have been thinking about for a while and although things have changed I'd still like to know if there is an answer.

Why are most petrol engined cars even sizes, for example, 1.2, 1.4, 1.8, 2.0 etc. etc..... and most diesel engines odd sizes, for example, 1.5, 1.7, 1.9?

I know that now there are a lot of diesel engines that are the same size as petrol now but it does seem a common thing.

I hope it makes sense as a question

It certainly does make sense as a question, just as it did the last time it was asked.

[daimatt]

[BOR]

bikemonster said:

It's because of the difference in the way capacity is calculated for compression (diesel) ignition engines as opposed to the calculation for spark capacity engines.

Basically, the spark plug intrudes into the combustion chamber and reduces the available capacity. This a 1.9 litre diesel engine equates quite tidily to a 1.8 litre petrol engine, even when made with the same block.

With all due respect, this is complete bks. Capacity refers to swept capacity and is calculated from the area of the cylinder bore x the stroke, regardless of the volume of the cylinderhead.

[bikemonster]

BOR said:

bikemonster said:

It's because of the difference in the way capacity is calculated for compression (diesel) ignition engines as opposed to the calculation for spark capacity engines.

Basically, the spark plug intrudes into the combustion chamber and reduces the available capacity. This a 1.9 litre diesel engine equates quite tidily to a 1.8 litre petrol engine, even when made with the same block.

With all due respect, this is complete bks. Capacity refers to swept capacity and is calculated from the area of the cylinder bore x the stroke, regardless of the volume of the cylinderhead.

Well, of course it is! As a matter of interest, does anybody know of a block that has done service as both an oil and a petrol burner? ISTR that diesel blocks are usually much heavier and stronger than petrol burners, in part because of the higher compression that they run.

I was just amazed that it took over an hour before somebody pointed the nonsense out. PH is slipping!

Then again, the question wasn't much better...Merc SLK230, BMW 320d, 330d, and 335d (mapped), BMW323i. Although at least some of those are prolly false clues to displacement anyway. Going back a bit, Mazda used to have 1.3 and 1.5 litre engines, and others did too.

[Ricky_M]

bikemonster said:

BOR said:

bikemonster said:

It's because of the difference in the way capacity is calculated for compression (diesel) ignition engines as opposed to the calculation for spark capacity engines.

Basically, the spark plug intrudes into the combustion chamber and reduces the available capacity. This a 1.9 litre diesel engine equates quite tidily to a 1.8 litre petrol engine, even when made with the same block.

With all due respect, this is complete bks. Capacity refers to swept capacity and is calculated from the area of the cylinder bore x the stroke, regardless of the volume of the cylinderhead.

Well, of course it is! As a matter of interest, does anybody know of a block that has done service as both an oil and a petrol burner? ISTR that diesel blocks are usually much heavier and stronger than petrol burners, in part because of the higher compression that they run.

I was just amazed that it took over an hour before somebody pointed the nonsense out. PH is slipping!

Then again, the question wasn't much better...Merc SLK230, BMW 320d, 330d, and 335d (mapped), BMW323i. Although at least some of those are prolly false clues to displacement anyway. Going back a bit, Mazda used to have 1.3 and 1.5 litre engines, and others did too.

Pretty sure the 1905cc block from Peugeot was used a Petrol in the 205 GTI and as a diesel unit in the 306, 405 etc.

[JB!]

high power VAG 20vt's run 1.9 diesel blocks, with uprated pistons and rods.

[Mr Dave]

bikemonster said:

BOR said:

bikemonster said:

It's because of the difference in the way capacity is calculated for compression (diesel) ignition engines as opposed to the calculation for spark capacity engines.

Basically, the spark plug intrudes into the combustion chamber and reduces the available capacity. This a 1.9 litre diesel engine equates quite tidily to a 1.8 litre petrol engine, even when made with the same block.

With all due respect, this is complete bks. Capacity refers to swept capacity and is calculated from the area of the cylinder bore x the stroke, regardless of the volume of the cylinderhead.

Well, of course it is! As a matter of interest, does anybody know of a block that has done service as both an oil and a petrol burner? ISTR that diesel blocks are usually much heavier and stronger than petrol burners, in part because of the higher compression that they run.

I was just amazed that it took over an hour before somebody pointed the nonsense out. PH is slipping!

Then again, the question wasn't much better...Merc SLK230, BMW 320d, 330d, and 335d (mapped), BMW323i. Although at least some of those are prolly false clues to displacement anyway. Going back a bit, Mazda used to have 1.3 and 1.5 litre engines, and others did too.

Im pretty sure the diesel 1.9tdi block and the 1.8 8valve/16valve/20valve block are very similar, maybe not cast out of the same stuff but very similar. BMW 335d is a 3.0 litre and most 323/523is are 2.5 litre. Same as the 316 and 318 were both 1.9 litre petrols.

[JB!]

JB! said:

high power VAG 20vt's run 1.9 diesel blocks, with uprated pistons and rods.

and the external casting/mouting points is the same on all 1.8+ VW 4cyl's

[wombat172a]

bikemonster said:

As a matter of interest, does anybody know of a block that has done service as both an oil and a petrol burner?

Land Rovers older 2.25 Petrol & Diesel engines used pretty much exactly the same block I think.

Not sure if that helps solve the question though.

[Huntsman]

The ford kent motor was built as a diesel for marine use, it was woefully inadaquate in that role, compression was far too low to help the bottom end survive and hence was really bad at starting.

[HellDiver]

Huntsman said:

The ford kent motor was built as a diesel for marine use, it was woefully inadaquate in that role, compression was far too low to help the bottom end survive and hence was really bad at starting.

The 1.8TD in Escorts, Fiestas and Mondeos in the 90's were still using the old Kent-derived Endura-DE engine. Piece of junk, only getting a smokey 75hp with a turbo.

[niva441]

HellDiver said:

The 1.8TD in Escorts, Fiestas and Mondeos in the 90's were still using the old Kent-derived Endura-DE engine. Piece of junk, only getting a smokey 75hp with a turbo.

Only the bore spacings were common, they built the diesels on the old Kent line.

[davepoth]

BMC B-Series engine block was used as a diesel, and it's popular still in marine applications. So it powered both MGBs and Narrowboats.