SCR's relationship to DCR
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SCR's relationship to DCR
Lets say you have two motors and both have 8.8 DCR but one has 11.6:1 SCR and the other has 10.4:1 SCR - will there be a difference in detonation resistance/vulnerability (assume quench is the same for both, cooling etc.)
Simple question: does scr have any role in determining detonation vulnerability/resistance or is this stictly related to dcr?
Also, how about increasing compression via decreasing the quench (0 deck gasket)? I had another thread where I noted that a cc464 (lt1 specific cam) has an ivc of 55 which puts the dcr at or above 9:1 (depending on specs you use on a stock motor). Leads me to believe running a 9:1 dcr with a quench around .035 better cooling and a tune should be no problem?
Simple question: does scr have any role in determining detonation vulnerability/resistance or is this stictly related to dcr?
Also, how about increasing compression via decreasing the quench (0 deck gasket)? I had another thread where I noted that a cc464 (lt1 specific cam) has an ivc of 55 which puts the dcr at or above 9:1 (depending on specs you use on a stock motor). Leads me to believe running a 9:1 dcr with a quench around .035 better cooling and a tune should be no problem?
Last edited by 1LESSZ28; Jun 25, 2007 at 01:04 PM. Reason: drunk
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Yes, there is a big difference.
Think of DCR as related to low rpm/high load detonation and SCR as playing a role at high rpm/high load conditions. When in the region of peak torque at WOT, the VE is at its' peak and cylinder pressures will be quite high. Due to increased cylinder filling and less time for the mixture to escape after BDC but prior to IVC. That's why you can't run 14:1 with a huge cam on pump gas. You would get excessive cylinder pressure and detonation at WOT, especially near peak torque rpm, even though it might run good at low rpm. This is even more the case with a boosted motor, which sees very high VE over a wide rpm range and needs a low SCR to run on pump gas regardless of DCR..
Rich
Think of DCR as related to low rpm/high load detonation and SCR as playing a role at high rpm/high load conditions. When in the region of peak torque at WOT, the VE is at its' peak and cylinder pressures will be quite high. Due to increased cylinder filling and less time for the mixture to escape after BDC but prior to IVC. That's why you can't run 14:1 with a huge cam on pump gas. You would get excessive cylinder pressure and detonation at WOT, especially near peak torque rpm, even though it might run good at low rpm. This is even more the case with a boosted motor, which sees very high VE over a wide rpm range and needs a low SCR to run on pump gas regardless of DCR..
Rich
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Joined: Jan 2002
Posts: 1,935
From: Mobile, Ala..USA
Yes, there is a big difference.
Think of DCR as related to low rpm/high load detonation and SCR as playing a role at high rpm/high load conditions. When in the region of peak torque at WOT, the VE is at its' peak and cylinder pressures will be quite high. Due to increased cylinder filling and less time for the mixture to escape after BDC but prior to IVC. That's why you can't run 14:1 with a huge cam on pump gas. You would get excessive cylinder pressure and detonation at WOT, especially near peak torque rpm, even though it might run good at low rpm. This is even more the case with a boosted motor, which sees very high VE over a wide rpm range and needs a low SCR to run on pump gas regardless of DCR..
Rich
Think of DCR as related to low rpm/high load detonation and SCR as playing a role at high rpm/high load conditions. When in the region of peak torque at WOT, the VE is at its' peak and cylinder pressures will be quite high. Due to increased cylinder filling and less time for the mixture to escape after BDC but prior to IVC. That's why you can't run 14:1 with a huge cam on pump gas. You would get excessive cylinder pressure and detonation at WOT, especially near peak torque rpm, even though it might run good at low rpm. This is even more the case with a boosted motor, which sees very high VE over a wide rpm range and needs a low SCR to run on pump gas regardless of DCR..
Rich
Really it depends on the whole combination of parts that get you there....tight quench and VE play a HUGE part when dynamic compression limits are being pushed. 9.0 to 1 DCR is the understood limit on pumpgas, I am running 13 to 1 SCR with a DCR of 8.7 to 1....I am at the limit for my climate. But I got a BIG cam, tight quench and a BIG cooling system.....I am still in the phase of working the bugs out...but it does run warm.
David
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From: Mobile, Ala..USA
If you really want to know the combo I will pm you.
David
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