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Home > Help Needed / General Tech Chat > compression ratio help!!

Clubman_turbo

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Member #: 9692
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5th Jan, 2012 at 07:15:29pm

hi.

I am currently building a turbo engine but i can not get my head around the compression ratio calculating. currently my head is 25cm3 and i will be running 10cc omega pistons with a 3.8 head gasket

i would like to achieve an 8:5 ratio but i am unsure that my head has been worked enough for this?

any help will be great

cheers charlie

Craigie-B

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Wootton Bassett

5th Jan, 2012 at 07:30:20pm

http://turbo-mini.com/70947.html

:)

On 10th Mar, 2012 theoneeyedlizard said:
Hypothetically speaking, where would you stick your nozzle?


On 22nd Jun, 2012 apbellamy said:
my wife doesn't know what.head is never mind compression ratio.

Clubman_turbo

4 Posts
Member #: 9692
Junior Member

5th Jan, 2012 at 08:03:19pm

hi.

thanks, i have just done the calculation and i managed to get 8.7 i think if i did it correctly. would you recommend getting the head taken to 27-8cc size and keep the 10cc pistons rather than going for some 18cc forged pistons.

cheers charlie


wng691s clubby

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Cleethorpes

5th Jan, 2012 at 08:05:00pm

if you open the chambers out more you will be able to run higher boost. If you already have the 10cc piston then opening out the chambers of the head will also save you some cash

Edited by wng691s clubby on 5th Jan, 2012.

Done now needs redoing lol

BENROSS

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Resident Cylinder Head Modifier

Mitsi Evo 7, 911, Cossie. & all the chavs ...... won no problem

5th Jan, 2012 at 09:10:46pm

you need 25cc in the chamber for 8.5:1
heres my calc with for a +20 over boar with omegas 10cc dish

1293 cc

323.25 cc

25 cc Head Vol
10 cc Piston dish
3.8 cc Head Gas
4 cc Ring Lands
Total 42.8 cc

compression ratio is 8.55:1






bennyy

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Doncaster, yorkshire

5th Jan, 2012 at 10:26:46pm

What cc engine?

Audi s4 b5 - 470bhp & 486ft lbs

On 15th Mar, 2012 wil_h said:
Yes, Carl says he gets requests for rimming all the time

On 30th Apr, 2012 Brett said:
yeah stick the bit in and give it a wobble *wink*


Clubman_turbo

4 Posts
Member #: 9692
Junior Member

5th Jan, 2012 at 10:47:55pm

hi

thanks for the quick response really appreciated :) The engine has just been freshly bored and is 1293, so by the calculations i should be able to run 12-15 psi safely then.

i am in the process of building the engine at the moment and i have become stuck on which cam to use :S i have heard good things about the avonbar ph2 cam and 1:3 rockers! but i was wondering what you experts think on this set up?

cheers charlie

bennyy

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Doncaster, yorkshire

6th Jan, 2012 at 07:02:16am

For 1293 the ratio is 8.55:1 as Steve said, with a good intercooler 15psi is no problem

Cam wide the ph2 is a great cam, would be by choice, I have one in mine.

Audi s4 b5 - 470bhp & 486ft lbs

On 15th Mar, 2012 wil_h said:
Yes, Carl says he gets requests for rimming all the time

On 30th Apr, 2012 Brett said:
yeah stick the bit in and give it a wobble *wink*


Clubman_turbo

4 Posts
Member #: 9692
Junior Member

6th Jan, 2012 at 07:05:25pm

hi

cheers for all the help guys, i can now order the parts and get the engine done so its ready for summer *happy*

thanks charlie

theoneeyedlizard

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The Boom Boom speaker Police!

Essex

6th Jan, 2012 at 09:05:37pm

For reference, I use 20psi on 8.6:1.

In the 13's at last!.. Just
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