Any good threads or info on compression, quench, DCR?
Thread Starter
Joined: Apr 2007
Posts: 9,711
Likes: 999
From: Evansville,IN
Any good threads or info on compression, quench, DCR? I have been searching for a while online tonight. I haven't seen any threads recently so I am going to start a new one. I normally try to search before I ask a question.
I'm in the process of trying to finish gathering parts/info for my H/C/I swap next month. One thing I know absolutely nothing about is quench and DCR. I know what compression is but not much past that.
I am using the TR230 cam and TEA 5.3 1.5 heads(which I am sure you know if you have seen my other two threads recently)
I am trying to find out what chamber cc and gasket I should go with. I have found out more than likely I will have to flycut the pistons which is fine.
I was talking to Frost through emails about the highest compression I can run and he said as long as the DCR is 8.7 or lower I should be fine.
What the hell is DCR?
I'm in the process of trying to finish gathering parts/info for my H/C/I swap next month. One thing I know absolutely nothing about is quench and DCR. I know what compression is but not much past that.
I am using the TR230 cam and TEA 5.3 1.5 heads(which I am sure you know if you have seen my other two threads recently)
I am trying to find out what chamber cc and gasket I should go with. I have found out more than likely I will have to flycut the pistons which is fine.
I was talking to Frost through emails about the highest compression I can run and he said as long as the DCR is 8.7 or lower I should be fine.
What the hell is DCR?
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
DCR is Dynamic compression ratio. While SCR (static compression ratio) is only true at TDC, DCR is a constant calculated with .006 lift cam values.
DCR is pretty much a measuring yard to determine octane needed to run the motor and to a certain extend cylinder pressures.Its calculation is very complex and usualy done via calculators or excel sheets (to make it easier).
Quench is the distance between piston deck at TDC from head deck. It is calculated as follow:
Q= Compressed gasket thickness - piston deck height (in/out of hole)
For a street LS motor best quench is in the .035>.045 depending on SCR. The more compression the tighter quench to reduce detonation potential and increase fuel burn efficiency.
PM me I'll give you the values you want.
DCR is pretty much a measuring yard to determine octane needed to run the motor and to a certain extend cylinder pressures.Its calculation is very complex and usualy done via calculators or excel sheets (to make it easier).
Quench is the distance between piston deck at TDC from head deck. It is calculated as follow:
Q= Compressed gasket thickness - piston deck height (in/out of hole)
For a street LS motor best quench is in the .035>.045 depending on SCR. The more compression the tighter quench to reduce detonation potential and increase fuel burn efficiency.
PM me I'll give you the values you want.
Last edited by PREDATOR-Z; Sep 15, 2009 at 05:39 AM.
Don't get caught up in the LS1Tech DCR bull$hit. DCR is a data point, but a small one. There is not a standard method to calculate DCR and there is no data to substantiate that DCR ALONE affects anything. Search the SAE archives for all the research papers written on the subject....DCR is such a mystery and so important to performance that not one contributing engineer has let the secret out of the bag. 
Set your SCR and quench to reasonable values for the intended application. If the combination is correct you will make gobs of power.
Set your SCR and quench to reasonable values for the intended application. If the combination is correct you will make gobs of power.
Last edited by 405HP_Z06; Sep 15, 2009 at 09:59 PM.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Don't get caught up in the LS1Tech DCR bull$hit. DCR is a data point, but a small one. There is not a standard method to calculate DCR and there is no data to substantiate that DCR ALONE affects anything. Search the SAE archives for all the research papers written on the subject....DCR is such a mystery and so important to performance that not one contributing engineer has let the secret out of the bag.
Set your SCR and quench to reasonable values for the intended application. If the combination is correct you will make gobs of power.
Set your SCR and quench to reasonable values for the intended application. If the combination is correct you will make gobs of power.
I do agree on not going over 9.0 DCR on the street. I had to put in TR-6 plugs to get my timing where I feel it should be on 92 octane. Anything over 90 degrees with the TR-55 plugs and my setup would always ping right @ 4000 rpm even with the timing at 20 degrees. My static compression is 11:1 with my dcr at 9.0:1 and it does make for great low end torque. My cranking compression is right around 225-230 psi for any type of reference.
