Why do we use litres and not Cubic inches in the uk

[pblake]

Having a discussion at work as to why in the UK we have always used Litres to describe engine capacity and not cubic inches as in the old 3 litre Bentley.
All the bolts shims and everything else was imperial so why not the CC

[craggers]

EEC ruling?

[trackerjack]

Because the Yanks started using cubic inches first we had to be different.

Just to carry on being stupid our media still insist on saying "half of one percent" instead of .5 percent.

[McHaggis]

Because the early production cars were German/French and they used litres - maybe they just set the precedent?

[Captain Muppet]

pblake said:

All the bolts shims and everything else was imperial so why not the CC

Doesn't "CC" stand for cubic centimetres? If so it's hard to have imperial ones.

[kambites]

Captain Muppet said:

pblake said:

All the bolts shims and everything else was imperial so why not the CC

Doesn't "CC" stand for cubic centimetres? If so it's hard to have imperial ones.

Cubic Capacity.

Well, it gets used for both.

[MiseryStreak]

Actually the US have been using the SI unit of cc or litres since the 1980s. Hence 6.1 litre Hemi, 7 litre Z06, 8.3 litre SRT-10 etc. All car manufacturers except the US before the 80s used SI units, cubic centimetres or litres. It's not a case of the British being different here.

[kambites]

MiseryStreak said:

It's not a case of the British being different here.

No, it's a case of the British not being different, which is unusual when it comes to measurements.

[pblake]

If the engine designeers were drawing everything else in Inches they then must have had to do calculations to get closest to the metric amount which seems like a lot of work.

[hyperblue]

pblake said:

If the engine designeers were drawing everything else in Inches they then must have had to do calculations to get closest to the metric amount which seems like a lot of work.

Converting between imperial and metric is piss easy. Engine capacity isn't precise anyway.

[Captain Muppet]

hyperblue said:

Engine capacity isn't precise anyway.

I'd be very interested to hear in what way you think that the capacity isn't precise.

(pi/4)*Bore^2*Stroke*cylinders = capacity

[FoundOnRoadside]

Perkins still use cubic inches for their engines. The AD3.152 is a 3 cylinder 152ci, which works out about 2.5 litres.

[eldar]

MiseryStreak said:

Actually the US have been using the SI unit of cc or litres since the 1980s. Hence 6.1 litre Hemi, 7 litre Z06, 8.3 litre SRT-10 etc. All car manufacturers except the US before the 80s used SI units, cubic centimetres or litres. It's not a case of the British being different here.

I had a 1989 Mustang. That had a 302 engine, and badges to prove it. Don't think it was CCs

[MaximumJed]

Captain Muppet said:

hyperblue said:

Engine capacity isn't precise anyway.

I'd be very interested to hear in what way you think that the capacity isn't precise.

(pi/4)*Bore^2*Stroke*cylinders = capacity

Presumably because what is referred to as a 2 litre engine may in fact be 1998cc, or 1996cc?

[pblake]

doogz said:

Really?

Multiplying by 16.4 when you're finished, so that you can tell the general public the capacity in metric, is a lot of work?

No thats not a lot of work but they would not have done it like that, it would have been designed in inches to give a metric result so the calculations would have been done before and not after the design. I know it just means a conversion but why bother is my piont when we could have just left it in inches.

[Megaflow]

FoundOnRoadside said:

Perkins still use cubic inches for their engines. The AD3.152 is a 3 cylinder 152ci, which works out about 2.5 litres.

Not any more... They are now something like 1104D-44T.

1100 = 1100 Series
4 = 4 cylinders
D = Tier 3 compliant
44 = 4.45 litres
T = Turbo charged

[McSam]

MaximumJed said:

Captain Muppet said:

hyperblue said:

Engine capacity isn't precise anyway.

I'd be very interested to hear in what way you think that the capacity isn't precise.

(pi/4)*Bore^2*Stroke*cylinders = capacity

Presumably because what is referred to as a 2 litre engine may in fact be 1998cc, or 1996cc?

Possibly. The statement "two-litre" is very rarely accurate, but the capacity itself is far more precise than the nearest cubic centimetre.

Only reason cars are quoted in "litre" engine sizes rather than cubic centimetres was originally to save badge material for the bootlid

[Captain Muppet]

McSam said:

MaximumJed said:

Captain Muppet said:

hyperblue said:

Engine capacity isn't precise anyway.

I'd be very interested to hear in what way you think that the capacity isn't precise.

(pi/4)*Bore^2*Stroke*cylinders = capacity

Presumably because what is referred to as a 2 litre engine may in fact be 1998cc, or 1996cc?

Possibly. The statement "two-litre" is very rarely accurate, but the capacity itself is far more precise than the nearest cubic centimetre.

Only reason cars are quoted in "litre" engine sizes rather than cubic centimetres was originally to save badge material for the bootlid

Unless you are BMW, in which case you just stick on a badge based on marketing and let the engineers worry about what the engine size is.

Engine capaciy of my cars is correct to the nearest CC on the V5. If they measured it in litres you'd expect some rounding.

[RenesisEvo]

Captain Muppet said:

hyperblue said:

Engine capacity isn't precise anyway.

I'd be very interested to hear in what way you think that the capacity isn't precise.

(pi/4)*Bore^2*Stroke*cylinders = capacity

Assuming the volume of air that is displaced takes the form of a perfect cylinder (for example, consider a wankel engine).

[McSam]

Captain Muppet said:

Unless you are BMW, in which case you just stick on a badge based on marketing and let the engineers worry about what the engine size is.

Engine capaciy of my cars is correct to the nearest CC on the V5. If they measured it in litres you'd expect some rounding.

Absolutely - or indeed Mercedes with the '6.3' badges on 6208cc, or Renault calling 1148cc Clios 1.2s.

But that wasn't my point - I meant that, while clearly everything is designed in cubic millimetres, the whole '1.6, 1.8 litre' etc. naming thing, rather than 1600cc etc. is down to allowing shorter badges on the back of the car.

Renesis, capacity is never determined by volume of air displaced, as that's affected by many factors, but is the difference in cylinder volume from bottom to top dead centres. For things without cylinders.. you're on your own

Edited by McSam on Wednesday 25th July 13:34