Engine capacities?

2.1td · Post by **2.1td** » 10 Aug 2006, 09:45

There must surely be some knowledgeable folks out there who can shed light on the following:-
Engine capacities, what's it all about eh? Why is my Xantia a 2.1 when it is clearly 2088 cc. Or my old BX 17RD was 1769ccs (which divided by four cylinders = 442.25cc for each one!), nearer to a 1.8! My 2CV is 602cc (0.6!) Of course it's not just the French. My neighbour has a new Polo 1.2 which is 1198cc and my Minis from way back were 1275cc (1.3) and 998cc (1.0)! Is it that car manufacturers just can't be bothered to get it right! I mean why 2088cc? Couldn't they manage the extra 12ccs? I guess that it is all down to taxation brackets (the original 2CV being the French Deux Chevaux, although that didn't last long and in fact the 602 cc ones were in fact Trois Chevaux!) )and I do remember a long time ago reading somewhere that in the days of decoking and reboring there was a margin left so that the rebore wouldn't take the capacity up into the "next" bracket. Or something like that! I'm sure that this will be a can of worms but should be quite fun to see what comes up!

dnsey · Post by **dnsey** » 10 Aug 2006, 12:10

I suspect the simple answer is that engine designers don't work towards a specific, 'round figure' swept volume. Why should they - it's just one factor amongst a large number of others which they have to juggle? They might just as logically work towards a nice-sounding oil pressure or crankshaft weight!
The naming of engine sizes is undoubtedly the work of marketing departments, who go for a 'snappy' figure which, where it's significantly different from the actual volume, is presumably calculated to appeal to the target demographic.
I don't know how governments arrive at engines sizes for taxation purposes, but I guess that they measure a number of random samples. Provided that these are 'within the bracket' the specification is met. There will, of course, be minor differences due to manufacturing tolerances, but these are very unlikely to be large enough to warrant making the engines a few ccs smaller 'just in case'.

Kowalski · Post by **Kowalski** » 10 Aug 2006, 13:56

Engine sizes are based on three measurements, the stroke length, the bore diameter and the number of cylinders. The engineers simply aren't concerned with getting the cubic capacity to a nice round number, they've got far more important concerns.

Post by **CitroJim** » 13 Aug 2006, 21:48

As Kowalski and Dnsey said,

You'll always find the bore and stroke measurements come out at exact figures. For instance the bore and stroke of an XUD9 engine is 83 x 88 mm which gives a capacity of 1905cc. The same goes for the XU5 1600cc engine with an "oversquare" bore and stroke of 83 x 73mm giving 1588cc.

I cannot think of a single engine in any vehicle ever that has precisely the same engine cc as advertised on the tailgate!

fastandfurryous · Post by **fastandfurryous** » 14 Aug 2006, 11:19

citrojim wrote:I cannot think of a single engine in any vehicle ever that has precisely the same engine cc as advertised on the tailgate!

I can, but only one.

CX 25. 2500cc exactly.

Post by **CitroJim** » 14 Aug 2006, 12:40

fastandfurryous wrote:
citrojim wrote:I cannot think of a single engine in any vehicle ever that has precisely the same engine cc as advertised on the tailgate!
I can, but only one.

CX 25. 2500cc exactly.

I knew someone would know of one

bxbodger · Post by **bxbodger** » 14 Aug 2006, 16:28

Sorry, here's another- BL's A series engine in 1275cc form, badged generally as a 1300 on ADO16's, Allegros,Marinas, etc,but when fitted to the 1275GT Mini clubman thats what it said all along the bottom of the doors....MINI 1275 GT....!!

It's strange that they put the actual capacity on the sporty car, but labled it as 1300 on the shopping cars, but that's BL for you!!

Village · Post by **Village** » 17 Aug 2006, 09:07

its not just engines sizes that have been got at by the marketing people. Landrovers used to be '88' or '109' (the wheel base of the vehicle) up until the series III model , but when the (retrospectively named) Defender came out with its new chassis they were named 90, 110 and 130. The 110 was honest, but the 90 has a wheel base of 91.9 inches and the 130 a 127 inch wheel base.

Thats marketing folk for you <loud marketing laugh>

thus ends my useless non-citroen related vehicular trivia for today, Join me tomorrow for more of the same.........

Pete

ps. Yes I am aware that the 130 was originally named the 127, but the marketing peeps got at it........

AndersDK · Post by **AndersDK** » 17 Aug 2006, 15:37

fastandfurryous wrote:
citrojim wrote:I cannot think of a single engine in any vehicle ever that has precisely the same engine cc as advertised on the tailgate!
I can, but only one.

CX 25. 2500cc exactly.

Not quite true.
Its still a rounded up figure from 2499.790407cc
Bore = 9.30cm
Stroke = 9.20cm

capacity = square(9.30/2) x pi x 9.20 x 4 ccm

bxbodger · Post by **bxbodger** » 17 Aug 2006, 15:52

And I was slightly out as well.... a BL 1275cc A series is actually 1274.48cc....

jeremy · Post by **jeremy** » 17 Aug 2006, 21:00

Ah yes - but - neither were actually that size were they? They both probably had different grades of bore and piston (due to tool wear during a shift)

f00lzz · Post by **f00lzz** » 17 Aug 2006, 21:53

Ho Hum!!

2.1td · Post by **2.1td** » 18 Aug 2006, 00:25

Ha, well there you are, I knew it would get some of you having a natter! Job done. Great forum!