What a Question!!
Turbo Mini Forums

So this is one of the questions in one of my tests for college.

This shows you how competant the IMI really are!

A four cylinder engine has a capacity of 2 litres, it has a compression ratio of 10 to 1, calculate the volume of the combustion chamber in cubic centimetres - show formula and workings (4 marks)

well at least they give you all of the possible variables...

Deck height, ring lands, piston dish.....any more for any more...

I guess im just assuming flat top pistons, piston that comes level to the top of the head gasket, and no ring land volume! With square bore/stroke.

Edited by James_H on 10th May, 2009.

Think about it...it is easy.

They arent asking for ring lands etc etc etc....just the complete combustion chamber.

Which will be 1/10 the swept volume of any given cylinder.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Ive still got to go the long way around to write up all of the formula/workings out.

lame.

There are so many questions that are just vague! The online questions are the worst!

Im just having a rant because im stuck inside when its sunny doing tests with awefull questions.

How can there be a long way ?

2000/4 = 500cc

500cc/10 = 50cc chamber

You cant answer the question any other way ??

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

for some reason i wanted to go from the beggining. bore/stroke working out the cylinder size etc etc....im being a doofus.

its all already done for me in the question.

sorry, ive spent too long trying to sound clever in this crap and im losing touch with rational thinking!

time for a break i think.


EDIT: i know what i was doing, i was going about it the same way as you would to work out the CR. Im not thinking about what im doing.

looks like im the incompetant one not the IMI

Edited by James_H on 10th May, 2009.

50cc is wrong. It's 55.56cc because it (500cc + chamber size) / chamber size = 10

Jean

http://www.jbperf.com/

I'm with Jean on this one.

Jean your answer has me confused.

Could you explain it to me please? im abit slow compared to you lot!

The thing that is confusing me is how can you do 500 + combustion chamber when you dont know what the combustion chamber is.

EDIT: i guess that formula is you working backwards to double check that 55.56 comes out to 10:1 CR?

Edited by James_H on 10th May, 2009.

Enter X for the combustion chamber volume, then rearrange the formula to find X, basic algebra.

I always subtract 1 from the CR then divide the cylinder volume by the result.

CC/CR-1= 55.5555555555555555555555555

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

(500cc + X) / X = 10

500cc + X = 10X

500cc = 10X - X = 9X

X = 500cc/9 = 55.5555556cc

Simple algebra and equivalent to what Paul is saying.

Jean

Edited by jbelanger on 10th May, 2009.

http://www.jbperf.com/

To elaborate, you know that the volume in the cylinder at BDC is the swept volume (500cc) plus the chamber volume (X: what you need to find out) so 500cc+X. At TDC, the volume is X since this is the chamber volume. You know that the compression ratio is 10:1 which means:
(500cc+X)/X=10

Jean

http://www.jbperf.com/

perfect! in summary. I need to brush up on algebra. Last time i did algebra was school GCSE's.

to me algebra is mouldy underware.

I get 50cc tbh

Did you read what I wrote?

http://www.jbperf.com/

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi

Jean is right.

It is (swept volumne + chamber)/chamber

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Actually just realised 55 is 1/10 of 555...so yeah 55cc chambers! :$

Edited by matty on 10th May, 2009.

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi

Ooops my bad 55 it is

Edit
Hang on They say in the question the capacity is 2l is capacity not SV+CV
If it is then you must take CV from capacity so the answer would then be 50cc all depends on what you measure capacity as ?

Edited by PaulH on 11th May, 2009.

No. Capacity is swept volume.

Super thats great I always like to figure out where I'v gone wrong, I love this Site :)

glad to see it wasnt just me!

All sorted now. Done both the tests and its just a few online tests (really not looking forwards to those) left to do, but they have to be done in college.

I should be qualified in 4 weeks if all goes to plan! Then i can start thinking about sorting uni!