CR math
Thread Starter
Melting Slicks
Joined: Jan 2002
Posts: 2,049
Likes: 1
From: kansas city MO
CR math
I used to have a 422 MTI dry sleeve w/ 11.25 CR, flat top pistons and the MTI stage 3 heads.
I have now used that set of heads in my Darton sleeve 427 w/ 22cc dished piston, my question is what's my current CR ?
Before I do FI I'll probably go w/ the AFR 225 w/ either the 67cc or 76cc depending on what my current CR is.
Anybody w/ the formula for calculating the CR ?
I have now used that set of heads in my Darton sleeve 427 w/ 22cc dished piston, my question is what's my current CR ?
Before I do FI I'll probably go w/ the AFR 225 w/ either the 67cc or 76cc depending on what my current CR is.
Anybody w/ the formula for calculating the CR ?
Melting Slicks
Joined: Mar 2003
Posts: 3,116
Likes: 10
From: Macomb MI
Formula for compression ratio
(CylVolume + ChamberVolume) / ChamberVolume
cylinder volume = pi/4 x bore^2 x stroke
chamber volume = cylinder volume / compression ratio - 1.0
dont forget to calc the volume of the head gasket and add the chamber volume
If milling heads
displacement ratio = cylinder volume / chamber volume
amount to mill = (new disp. ratio - old disp. ratio / new disp. ratio x old disp. ratio) x stroke
Also, this is still very crude as it doesnt take into account, deck height and top compression ring to piston deck volumes. but will get you close.
Phil
(CylVolume + ChamberVolume) / ChamberVolume
cylinder volume = pi/4 x bore^2 x stroke
chamber volume = cylinder volume / compression ratio - 1.0
dont forget to calc the volume of the head gasket and add the chamber volume
If milling heads
displacement ratio = cylinder volume / chamber volume
amount to mill = (new disp. ratio - old disp. ratio / new disp. ratio x old disp. ratio) x stroke
Also, this is still very crude as it doesnt take into account, deck height and top compression ring to piston deck volumes. but will get you close.
Phil
Last edited by RoadRebel; Nov 2, 2004 at 08:28 AM.
Burning Brakes
Joined: May 2000
Posts: 881
Likes: 0
From: Clearwater, FL, USA
Originally Posted by boblackhardtop
I used to have a 422 MTI dry sleeve w/ 11.25 CR, flat top pistons and the MTI stage 3 heads.
I have now used that set of heads in my Darton sleeve 427 w/ 22cc dished piston, my question is what's my current CR ?
Before I do FI I'll probably go w/ the AFR 225 w/ either the 67cc or 76cc depending on what my current CR is.
Anybody w/ the formula for calculating the CR ?
I have now used that set of heads in my Darton sleeve 427 w/ 22cc dished piston, my question is what's my current CR ?
Before I do FI I'll probably go w/ the AFR 225 w/ either the 67cc or 76cc depending on what my current CR is.
Anybody w/ the formula for calculating the CR ?
http://www.c5frc.com/calculators/Com...Calculator.htm
Le Mans Master
Joined: Jun 2003
Posts: 5,409
Likes: 0
From: Kentucky basketball is life the rest is just details
Originally Posted by FRC Tom
A little something I put together that might help.
http://www.c5frc.com/calculators/Com...Calculator.htm
http://www.c5frc.com/calculators/Com...Calculator.htm
That's pretty cool. Thanks for the link.
Drifting
Joined: Jun 2002
Posts: 1,340
Likes: 1
From: hamilton nj "Life's tough......It's even tougher if you're stupid."-John Wayne
Originally Posted by FRC Tom
A little something I put together that might help.
http://www.c5frc.com/calculators/Com...Calculator.htm
http://www.c5frc.com/calculators/Com...Calculator.htm
Thanks, it's a big help!
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