Unicorn :Compresion ratio [Update 1] - xBhp.com : The Global Indian Biking Community

viv.nomad · 06-06-2009, 02:56 AM

finally i have decided to try to increase compression ratio on my v1 uni and by the calculation and assumin the metal i m going to remove will result in volume change which would be equal to volume of cyllindrical shape of radius [bore\2] and length that i removed \ shaved from block .

for 9.6 : 1 compression ratio the length i should remove came out to be .4 mm

it is like

SV = pi*(57.3\2)^2*57.8*(1/1000) = 149.05 cc

default CR 9.1:1

so CV = SV \ (9.1 - 1) = 18.4 cc

now if i remove 0.4 mm from the block

volume change = pi*(57.3\2)^2*0.4 *(1/1000) = 1.03 cc

new CV = 18.4 - 1.03 cc = 17.37

hence new CR
(149.05/17.37)+1 = 9.58 : 1

should i go ahead any other adjustment required?????

and how much can i increase CR without worrying abt any thing!! max value??????

UPDATE 1:Compression ratio mod is complete , sattled for 10.1:1

Unicorn :Compresion ratio [Update 1]

MG · 06-06-2009, 08:49 AM

Query Approved

abhijeet080808 · 06-06-2009, 03:40 PM

Quote:

Originally Posted by viv.nomad

how much can i increase CR without worrying abt any thing!! max value??????

Just make sure that the engine is not knocking and valves do not bang into the piston. You can increase the CR to that limit.

viv.nomad · 06-06-2009, 06:08 PM

u sure??

share some exp!!

abhijeet080808 · 06-06-2009, 06:21 PM

I do not have any practical experience dude. But, AFAIK these are the two factors that limit the compression ratio. Maybe others with practical experiences can confirm.

And your calculations are correct!

viv.nomad · 06-06-2009, 07:04 PM

that are max physical borders.. i was talking abt limit where only increasing CR will give performance and it may not involve other component adjustment like valves..

abhijeet080808 · 06-06-2009, 09:46 PM

Quote:

Originally Posted by viv.nomad

that are max physical borders.. i was talking abt limit where only increasing CR will give performance and it may not involve other component adjustment like valves..

Increasing your CR up to these physical limits will improve performance irrespective of any changes in the valve timings. However, after a certain point, ignition timings will need to be changed to allow further increase of CR till the limits.

viv.nomad · 06-06-2009, 09:49 PM

woich to .. are bhai kab ignition timing change karne ki jururat padti hai....

kis CR k baad..

abhijeet080808 · 06-06-2009, 09:54 PM

Quote:

Originally Posted by viv.nomad

woich to .. are bhai kab ignition timing change karne ki jururat padti hai....

That depends on how the bike is currently set up. I do not have any idea about the unicorn. If ignition timings are not retarded, knocking may occur.

You can do one thing - go ahead and shave the 0.4mm from the head. If knocking occurs you will have two choices - use double head gasket to decrease the CR a bit, or use high octane petrol.

If everything is fine, go ahead and shave a bit more.

If knocking occurs again use double head gasket or high octane fuel.

So, the idea is to discover the limit of your bike with the current timings.

k_tornado_sj · 06-06-2009, 09:56 PM

you'll come to know when your engine knocks

06-06-2009, 02:56 AM	#1 (permalink)
viv.nomad free roaming! Join Date: Mar 2009 Location: Navi Mumbai Posts: 425	Unicorn :Compresion ratio [Update 1] finally i have decided to try to increase compression ratio on my v1 uni and by the calculation and assumin the metal i m going to remove will result in volume change which would be equal to volume of cyllindrical shape of radius [bore\2] and length that i removed \ shaved from block . for 9.6 : 1 compression ratio the length i should remove came out to be .4 mm it is like SV = pi(57.3\2)^257.8(1/1000) = 149.05 cc default CR 9.1:1 so CV = SV \ (9.1 - 1) = 18.4 cc now if i remove 0.4 mm from the block volume change = pi(57.3\2)^20.4 (1/1000) = 1.03 cc new CV = 18.4 - 1.03 cc = 17.37 hence new CR (149.05/17.37)+1 = 9.58 : 1 should i go ahead any other adjustment required????? and how much can i increase CR without worrying abt any thing!! max value?????? UPDATE 1:Compression ratio mod is complete , sattled for 10.1:1 Unicorn :Compresion ratio [Update 1] Last edited by viv.nomad; 06-09-2009 at 01:19 AM.

06-06-2009, 06:21 PM	#5 (permalink)
abhijeet080808 ElectroniX! Join Date: Sep 2008 Location: BLR/GHY/MAS Posts: 2,375	I do not have any practical experience dude. But, AFAIK these are the two factors that limit the compression ratio. Maybe others with practical experiences can confirm. And your calculations are correct! __________________ Your biking tells a lot about the person you are!

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06-06-2009, 08:49 AM	#2 (permalink)
MG Super Moderator Join Date: Mar 2006 Location: Maharashtra,India Posts: 5,900	Query Approved

06-06-2009, 06:08 PM	#4 (permalink)
viv.nomad free roaming! Join Date: Mar 2009 Location: Navi Mumbai Posts: 425	u sure?? share some exp!!

06-06-2009, 07:04 PM	#6 (permalink)
viv.nomad free roaming! Join Date: Mar 2009 Location: Navi Mumbai Posts: 425	that are max physical borders.. i was talking abt limit where only increasing CR will give performance and it may not involve other component adjustment like valves..

06-06-2009, 09:49 PM	#8 (permalink)
viv.nomad free roaming! Join Date: Mar 2009 Location: Navi Mumbai Posts: 425	woich to .. are bhai kab ignition timing change karne ki jururat padti hai.... kis CR k baad..

06-06-2009, 09:56 PM	#10 (permalink)
k_tornado_sj Demonic Flower ! Join Date: Dec 2008 Location: Jabalpur Posts: 87	you'll come to know when your engine knocks

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