Will 11:1 compression ratio be good to run?
12-21-2008, 10:49 AM
#16
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Join Date: Dec 1969
Location: Buffalo, New York
Posts: 10,745
Read what I wrote on DCR here: http://www.kennedysdynotune.com/Dyna...ion%20Tech.htm
What you need to keep in mind is that detonation is a problem primarily at two points in an engines operating regime. Low speed/high load (opening the throttle at low rpm) and at round peak torque (at WOT). The first situation is one where you should not operated a high performance engine anyway, and it is where the DCR concept has the most utility. So, you can't take an idea like "8.5:1 DCR is ok" very far. For example, if you had a 12:1 350 and a cam with the IV closing point at ~80 degrees ABDC (~310 degrees advertised duration on the intake) the DCR would be 8.4:1. On pump gas you could drive it around at low speeds w/o problem, but it would detonate at WOT near peak torque. It would not be a good combination in a number of other respects.
Basically, you should choose your CR based on the cam choice and fuel to be used, which in turn depends n the desired rpm range. Doing it any other way is bass ackwards.
Rich
PS: If you give me the cam specs, I will tell yu if I think it will work. Or just ask Lloyd.
What you need to keep in mind is that detonation is a problem primarily at two points in an engines operating regime. Low speed/high load (opening the throttle at low rpm) and at round peak torque (at WOT). The first situation is one where you should not operated a high performance engine anyway, and it is where the DCR concept has the most utility. So, you can't take an idea like "8.5:1 DCR is ok" very far. For example, if you had a 12:1 350 and a cam with the IV closing point at ~80 degrees ABDC (~310 degrees advertised duration on the intake) the DCR would be 8.4:1. On pump gas you could drive it around at low speeds w/o problem, but it would detonate at WOT near peak torque. It would not be a good combination in a number of other respects.
Basically, you should choose your CR based on the cam choice and fuel to be used, which in turn depends n the desired rpm range. Doing it any other way is bass ackwards.
Rich
PS: If you give me the cam specs, I will tell yu if I think it will work. Or just ask Lloyd.
Last edited by rskrause; 12-21-2008 at 10:56 AM.
12-21-2008, 02:58 PM
#17
Registered User
Join Date: Oct 2006
Location: Rochester Hills, MI
Posts: 746
Rich, very interesting insight as always. Seems like I'm learning something new here, so I want to make sure I am interpreting you correctly. This isn't stuff I've figured out on my own, I'm just trying to pass along what I know, so more experience is nice to learn from.
Are you saying DCR really only applies at low RPM and CR dominates at peak torque? So STATIC CR is more critical at peak torque than DCR? During my build I was led to believe high CR was fine as long as DCR was not too high. I thought that applied throughout the RPM range. Is is a blend of the 2, such that a good balance is required?
Don't have much time right now, leaving town, so I'll admit I did not read your link to refresh what you have already written. So, apologies if it's covered there.
Thanks.
Are you saying DCR really only applies at low RPM and CR dominates at peak torque? So STATIC CR is more critical at peak torque than DCR? During my build I was led to believe high CR was fine as long as DCR was not too high. I thought that applied throughout the RPM range. Is is a blend of the 2, such that a good balance is required?
Don't have much time right now, leaving town, so I'll admit I did not read your link to refresh what you have already written. So, apologies if it's covered there.
Thanks.
12-21-2008, 06:56 PM
#19
Registered User
Thread Starter
Join Date: Mar 2005
Location: Memphis, TN
Posts: 1,076
Read what I wrote on DCR here: http://www.kennedysdynotune.com/Dyna...ion%20Tech.htm
What you need to keep in mind is that detonation is a problem primarily at two points in an engines operating regime. Low speed/high load (opening the throttle at low rpm) and at round peak torque (at WOT). The first situation is one where you should not operated a high performance engine anyway, and it is where the DCR concept has the most utility. So, you can't take an idea like "8.5:1 DCR is ok" very far. For example, if you had a 12:1 350 and a cam with the IV closing point at ~80 degrees ABDC (~310 degrees advertised duration on the intake) the DCR would be 8.4:1. On pump gas you could drive it around at low speeds w/o problem, but it would detonate at WOT near peak torque. It would not be a good combination in a number of other respects.
Basically, you should choose your CR based on the cam choice and fuel to be used, which in turn depends n the desired rpm range. Doing it any other way is bass ackwards.
Rich
PS: If you give me the cam specs, I will tell yu if I think it will work. Or just ask Lloyd.
What you need to keep in mind is that detonation is a problem primarily at two points in an engines operating regime. Low speed/high load (opening the throttle at low rpm) and at round peak torque (at WOT). The first situation is one where you should not operated a high performance engine anyway, and it is where the DCR concept has the most utility. So, you can't take an idea like "8.5:1 DCR is ok" very far. For example, if you had a 12:1 350 and a cam with the IV closing point at ~80 degrees ABDC (~310 degrees advertised duration on the intake) the DCR would be 8.4:1. On pump gas you could drive it around at low speeds w/o problem, but it would detonate at WOT near peak torque. It would not be a good combination in a number of other respects.
Basically, you should choose your CR based on the cam choice and fuel to be used, which in turn depends n the desired rpm range. Doing it any other way is bass ackwards.
Rich
PS: If you give me the cam specs, I will tell yu if I think it will work. Or just ask Lloyd.
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