Raising Compression?
Thread Starter
Registered User
Joined: Jul 2003
Posts: 1,668
From: Cliffside Park, NJ
Raising Compression?
I know this is kind of a broad question but...
Lets say you have LE3 383 Setup... 6 Speed, 10 bolt.
11:1 CR puts out 430rwhp and 410rwtq.
What kind of numbers would you gain raising it to lets say... 11.8:1 or 12:1
What kind of numbers would you lose lowering it to 10.4:1 or 10:1?
I know dcr is more important, but I have no clue how that works. haha
Lets say you have LE3 383 Setup... 6 Speed, 10 bolt.
11:1 CR puts out 430rwhp and 410rwtq.
What kind of numbers would you gain raising it to lets say... 11.8:1 or 12:1
What kind of numbers would you lose lowering it to 10.4:1 or 10:1?
I know dcr is more important, but I have no clue how that works. haha
Registered User
Joined: Nov 2001
Posts: 3,515
From: Kansas
Re: Raising Compression?
People claim going from 10.5:1 to 11.0:1 will get you 2% increase in power.
BTW what you really need to be paying attention to is the DYNAMIC compression ratio.. not the static which you are asking about. Basically the more air you trap in the cylinder the higher the DCR and this is controlled by the closing point of the intake valve... typically the sooner it closes after the piston bottom dead center, the higher DCR youll see. It all has to do with the amount of AIR trapped in the cylinder instead of the physical volume of the combustion chamber... that is static CR.
BTW what you really need to be paying attention to is the DYNAMIC compression ratio.. not the static which you are asking about. Basically the more air you trap in the cylinder the higher the DCR and this is controlled by the closing point of the intake valve... typically the sooner it closes after the piston bottom dead center, the higher DCR youll see. It all has to do with the amount of AIR trapped in the cylinder instead of the physical volume of the combustion chamber... that is static CR.
Registered User
Joined: Oct 2001
Posts: 6,070
From: newton, kansas, USA
Re: Raising Compression?
Originally Posted by turbo_Z
People claim going from 10.5:1 to 11.0:1 will get you 2% increase in power.
BTW what you really need to be paying attention to is the DYNAMIC compression ratio.. not the static which you are asking about. Basically the more air you trap in the cylinder the higher the DCR and this is controlled by the closing point of the intake valve... typically the sooner it closes after the piston bottom dead center, the higher DCR youll see. It all has to do with the amount of AIR trapped in the cylinder instead of the physical volume of the combustion chamber... that is static CR.
BTW what you really need to be paying attention to is the DYNAMIC compression ratio.. not the static which you are asking about. Basically the more air you trap in the cylinder the higher the DCR and this is controlled by the closing point of the intake valve... typically the sooner it closes after the piston bottom dead center, the higher DCR youll see. It all has to do with the amount of AIR trapped in the cylinder instead of the physical volume of the combustion chamber... that is static CR.
Thread Starter
Registered User
Joined: Jul 2003
Posts: 1,668
From: Cliffside Park, NJ
Re: Raising Compression?
Originally Posted by turbo_Z
People claim going from 10.5:1 to 11.0:1 will get you 2% increase in power.
BTW what you really need to be paying attention to is the DYNAMIC compression ratio.. not the static which you are asking about. Basically the more air you trap in the cylinder the higher the DCR and this is controlled by the closing point of the intake valve... typically the sooner it closes after the piston bottom dead center, the higher DCR youll see. It all has to do with the amount of AIR trapped in the cylinder instead of the physical volume of the combustion chamber... that is static CR.
BTW what you really need to be paying attention to is the DYNAMIC compression ratio.. not the static which you are asking about. Basically the more air you trap in the cylinder the higher the DCR and this is controlled by the closing point of the intake valve... typically the sooner it closes after the piston bottom dead center, the higher DCR youll see. It all has to do with the amount of AIR trapped in the cylinder instead of the physical volume of the combustion chamber... that is static CR.
And I figured it'd be easier to get an answer using the scr.
Because i'm really curious to how much power i'm gaining from the extra .8-1 on the scr.
Banned
Joined: Oct 2002
Posts: 6,518
Re: Raising Compression?
Chris,
You can run anywhere from 11-12:1 compression on that setup and still have a relatively safe DCR even at the high end.
A 57-58cc chamber with flat top pistons and a zero deck block on a 383 will put you at the high end of that (12:1)
On that setup you are looking at 12hp difference from 11:1 to 12:1
Bret
You can run anywhere from 11-12:1 compression on that setup and still have a relatively safe DCR even at the high end.
A 57-58cc chamber with flat top pistons and a zero deck block on a 383 will put you at the high end of that (12:1)
On that setup you are looking at 12hp difference from 11:1 to 12:1
Bret
Last edited by SStrokerAce; Sep 5, 2005 at 03:03 PM.
Banned
Joined: May 2003
Posts: 6,661
From: LA (lower Alabama)
Re: Raising Compression?
It's not so much the DCR ya have now as it is the extra things that happen and ya can do with the extra static and DCR. The closer ya can keep it to the high end the more HP ya can make on pump gas or fuel.
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