2494 vs. 2476???

Sun Oct 02, 2005 9:08 am

I have asked this before......why are some 2494 cc and others 2476 cc...I donÃƒ”šÃ‚´t get it!

(Admin...Steve or Adam....where did all my posts go?) I should be close to an "addict"!

Sun Oct 02, 2005 10:06 am

I think the answer to this is that 2476cc is the "swept volume" and 2494cc is the actual volume. Swept volume doesn't take into account the volume of the combustion chambers.
Usual rules apply here, if I'm wrong and someone knows different, I'll eat humble pie.
Stuart.

Sun Oct 02, 2005 5:08 pm

anderls wrote:
(Admin...Steve or Adam....where did all my posts go?) I should be close to an "addict"!

They didn't go anywhere, you must have only posted 7 posts on the new forum. If you didn't sign up to have your post count carried on from the old forum then you will have lost them.

Sun Oct 02, 2005 11:20 pm

essbee wrote:I think the answer to this is that 2476cc is the "swept volume" and 2494cc is the actual volume. Swept volume doesn't take into account the volume of the combustion chambers.
Usual rules apply here, if I'm wrong and someone knows different, I'll eat humble pie.
Stuart.

That would give one hell of a compression ratio! Can't be that.
Handbook says "displacement fiscal" 2476 cc, and "effective" 2494cc.
Bore and stroke calculations give 2494.
The only meanings for "fiscal" in my dictionary are money related, so perhaps it was something to with a taxation class.

Mon Oct 03, 2005 2:13 am

I heard there are two different m20b25's.
Earlier and later type.
Earlier has 9.7:1 compression ratio
Later one had 8.5:1 i believe

they used different heads... not sure about pistons... maby thays the difference ?

Mon Oct 03, 2005 7:25 am

Brianmoooore wrote:That would give one hell of a compression ratio! Can't be that.
Handbook says "displacement fiscal" 2476 cc, and "effective" 2494cc.
Bore and stroke calculations give 2494.
The only meanings for "fiscal" in my dictionary are money related, so perhaps it was something to with a taxation class.

Thanks for putting me right Brian.
Apologies for mis-information Anderls

Mon Oct 03, 2005 9:14 am

Mops wrote:I heard there are two different m20b25's.
Earlier and later type.
Earlier has 9.7:1 compression ratio
Later one had 8.5:1 i believe

they used different heads... not sure about pistons... maby thays the difference ?

early 325s, late 325s, even M50 325s are all 2494cc.
M10 and M40 1.8s have a slightly different capacity.