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How do you calculate a modified engine's capacity
https://www.ausmini.com/forums/viewtopic.php?f=2&t=6835		 Page 1 of 1
Author:  71_mini_k [ Mon May 02, 2005 4:43 pm ]
Post subject:  How do you calculate a modified engine's capacity
Silly question time :oops:

Looking at people's signature blocks I have noticed that engine capacity varies from the standard engine a car orignally fitted with a 1098 has become a 1132, 1144 or 1152. And a 1275 becomes a 1310 or 1380 once modified

Hows is this determined?
Author:  fuzzy-hair-man [ Mon May 02, 2005 4:53 pm ]
Post subject: 
1/2 the Diameter of the pistons including overbores if any

square this number then multiply it by 3.14 (pi) (area of the circle that is the bore of piston)

now times this by the the stroke of the engine

and then times this by four cause you have four pistons

This is as far as I know how it goes.
Correct me if I am wrong as far as I know it doesn't take into account combustion chamber size
Author:  71_mini_k [ Mon May 02, 2005 5:07 pm ]
Post subject: 
Thanks Fuzzy but I think I'm more confussed now that before :roll: suddenly it sounds like a bad maths question.

Is there a easier way like 1275 +.020" (1293), +.040" (1310), +.060" (1330), or +.115" (1380)
Author:  fuzzy-hair-man [ Mon May 02, 2005 5:12 pm ]
Post subject: 
Yes I guess so but I don't know them so I can't say :wink: :P best ask Kev :P
Author:  1310/71 [ Mon May 02, 2005 5:17 pm ]
Post subject: 
71_mini_k wrote:
Thanks Fuzzy but I think I'm more confussed now that before :roll: suddenly it sounds like a bad maths question.

Is there a easier way like 1275 +.020" (1293), +.040" (1310), +.060" (1330), or +.115" (1380)


Wrong Kevin, but you're spot on with the 1275cc overbore capacities there. Answered your own question in fact.
KB
Author:  FatMaserati [ Mon May 02, 2005 5:23 pm ]
Post subject: 
1275 can become 1430 too... ;)
Author:  danidad [ Mon May 02, 2005 5:25 pm ]
Post subject: 
as this is being discussed here might as well ask here... whats an 1100 +40 thou
Author:  1310/71 [ Mon May 02, 2005 5:37 pm ]
Post subject: 
FatMaserati wrote:
1275 can become 1430 too... ;)


yes but we were talking about overbores, not stroking as well. :wink:
For that you'll have to use the formula the fuzzy haired one gave us.
:D KB
Author:  fuzzy-hair-man [ Mon May 02, 2005 6:06 pm ]
Post subject: 
OK using that formula and the bore size Kev gave in the other thread ( 65.6mm )and a 1100 stroke being 83.82mm

Ok so convert to cm 6.56 cm bore and 8.382 cm stroke

(6.56 / 2 ) ^ 2 * 3.14 = 33.79 square cm (X^2 means squared)

33.79 * 83.82 = 283.22778

283.22778 * 4 = 1132.9

1133 approximately

now lets see if Kev tells me if my calculation is right in practice :D :P
Author:  TheMiniMan [ Mon May 02, 2005 6:53 pm ]
Post subject: 
to work out any piston engine`s capacity--->

pie x r squared--- is the formula to work out the area of a circle (pie being 3.1412,,, & r being the radius of the cyl)

then times that by the length of the stroke of the crankshaft

Then times that by however many cyls there are

easy-peasy

:-)
Author:  fuzzy-hair-man [ Mon May 02, 2005 6:56 pm ]
Post subject: 
That's what I said :P :D Did I get it right :?:
Author:  danidad [ Mon May 02, 2005 9:23 pm ]
Post subject: 
thats a big thanks from me peoples
Author:  drmini in aust [ Mon May 02, 2005 10:16 pm ]
Post subject: 
Yes an 1100 bored to +.040" is an 1132. +.060" gives 1152.
Next stop is 68.0mm (Imp pistons) for 1220cc approx. For what a decent set of UK Imp pistons is worth now, you could buy a 1275... 8)
Author:  danidad [ Mon May 02, 2005 10:40 pm ]
Post subject: 
thanks again doc the previous owner said the motor had been rebuilt twice the most recent not that long ago mileage wise... motor looks good and everything else he said has checked out so far... (he was a good bloke) so i wont be touching the bore, only pulled it open to make sure things looked right. centre oil pickup is the only job im intending to do to the innards at this stage.
Author:  71_mini_k [ Tue May 03, 2005 9:23 am ]
Post subject: 
Thanks for everyone's input. :D

I just had my engine and gearbox rebuilt and during the process I was informed that my 1098 has been bored to +.040 and I wanted to know how to recalculate the capacity.

I am now looking forward to the next dyno day so I can see how much power I have gained as I had the diff changed, a road/rally cam fitted and I was already running twin SU and extractors.

:wink:
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