Page:
Home > Help Needed / General Tech Chat > Compression Ratio???

paul1986

User Avatar

80 Posts
Member #: 6234
Retard & Spaz

Yeovil, Zummerset

3rd Jun, 2009 at 05:21:21pm

hi all

i have started to put together my turbo engine only to find out that ontop the pistons there are marking saying +0.30 so i am assuming i have a overbore engine, so firstly is this a 1310?

secondly i do not have a clue how to work out my compression i have tried searching over and over again and it still confuses me lol so any help would be great, the engine spec as far as i can see is:

12g940 head possilbly skimmed as this measures 69.30mm
Engine bore of well maybe 1310 ( measures about 71.35mm )
dished pistons of 7mm
and a stroke of 78mm
i hope this sounds right, oh and its currently a n/a engine with std valves.
please help guys what is my compression ratio????*frown*

Currently building the new engine - 1312 t25 a series!

Mr Joshua

2497 Posts
Member #: 1954
Post Whore

Luton Bedfordshire

3rd Jun, 2009 at 05:30:07pm

Deck to piston height?
Head gasket being used?
Decompression plate fitted if so what size?
piston cc?
Combustion chamber volume?

Own the day


CR#

User Avatar

140 Posts
Member #: 1367
Advanced Member

Cape Town, South Africa

3rd Jun, 2009 at 05:31:10pm

Its as simple as the volume in the combustion chamber at the bottom of the pistons stroke over/divided by the volume at tdc.

Here are two calculaters after a quick search on google.
http://www.csgnetwork.com/compcalc.html
http://www.rbracing-rsr.com/compstaticcalc.html

Greg

Edited by CR# on 3rd Jun, 2009.


paul1986

User Avatar

80 Posts
Member #: 6234
Retard & Spaz

Yeovil, Zummerset

3rd Jun, 2009 at 05:37:27pm

deck to piston height is approx 4mm, i will use a std metty turbo head gasket, no decompression plate, piston cc unsure combustion chamber volume unsure

Currently building the new engine - 1312 t25 a series!

CR#

User Avatar

140 Posts
Member #: 1367
Advanced Member

Cape Town, South Africa

3rd Jun, 2009 at 05:42:57pm

well thats all stuff you will need to work out before you can calculate your CR.
gl

paul1986

User Avatar

80 Posts
Member #: 6234
Retard & Spaz

Yeovil, Zummerset

3rd Jun, 2009 at 05:47:38pm

lol ok sounds like fun, i am sure its easy really

Currently building the new engine - 1312 t25 a series!

paul1986

User Avatar

80 Posts
Member #: 6234
Retard & Spaz

Yeovil, Zummerset

3rd Jun, 2009 at 05:57:07pm

i think i may have worked this out right piston cc would be 11 skimmed head means 22cc cambers yeah? gasket i have been told will be 3 in the equation so i come up with 37? so 37-327= 8.8 does this look right? like i said i think piston cc is 11 if my maths are right 1310 so +30 overbore and 7mm dish?

Currently building the new engine - 1312 t25 a series!

Turbo Phil

User Avatar

4641 Posts
Member #: 20
My sister is so fit I won't show anyone her picture

Lake District

3rd Jun, 2009 at 07:35:43pm

You need to measure the chamber volume in the head properly. They are supposed to be 21,4cc as standard, but they can vary quite a lot from the factory.

WWW.TURBO-MINI.COM


Mr Joshua

2497 Posts
Member #: 1954
Post Whore

Luton Bedfordshire

4th Jun, 2009 at 11:51:44am

without knowing who made the pistons you will have to measure the cc the old fashioned way no point in guessing *wink*

Own the day

Home > Help Needed / General Tech Chat > Compression Ratio???
Users viewing this thread: none. (+ 1 Guests)  
To post messages you must be logged in!
Username: Password:
Page: