Extended duration..why?
Extended duration..why? Looking to purchase a race kit for my bike and most of the kit has items to increase CR and reduce squish height and PV clearance but then goes about including revised intake and exhaust cams with extended duration b/c increased lift would become a PV problem right... but from my understanding extended duration will take away from your DCR or reduce it. So wouldn't this be counter productive?
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
At high rpm time is short, so extended duration cam allows sufficient air/fuel to be pulled in and exhaust gases pushed out...
PV clearance becomes more critical not with lift and duration, but with lsa getting closer (and overlap getting bigger).
PV clearance becomes more critical not with lift and duration, but with lsa getting closer (and overlap getting bigger).
Ok so let me run 3 scenarios by you guys.
Scenario 1.
What would happen if I were to raise compression using the gaskets and milling the head but continued to use the Stock cam? I would imagine this would cause too much DCR and would lead to detonation issues correct?
Scenario 2.
Raise compression using the same methods above but used an extended duration intake cam and stock exhaust cam
Scenario 3.
Opposite of 2. Use a stock intake but extended duration exhaust
Thanks
Scenario 1.
What would happen if I were to raise compression using the gaskets and milling the head but continued to use the Stock cam? I would imagine this would cause too much DCR and would lead to detonation issues correct?
Scenario 2.
Raise compression using the same methods above but used an extended duration intake cam and stock exhaust cam
Scenario 3.
Opposite of 2. Use a stock intake but extended duration exhaust
Thanks
Trending Topics
TECH Fanatic
Joined: Jun 2002
Posts: 1,979
Likes: 3
From: Upstate NY
Ok so let me run 3 scenarios by you guys.
Scenario 1.
What would happen if I were to raise compression using the gaskets and milling the head but continued to use the Stock cam? I would imagine this would cause too much DCR and would lead to detonation issues correct?
Scenario 2.
Raise compression using the same methods above but used an extended duration intake cam and stock exhaust cam
Scenario 3.
Opposite of 2. Use a stock intake but extended duration exhaust
Thanks
Scenario 1.
What would happen if I were to raise compression using the gaskets and milling the head but continued to use the Stock cam? I would imagine this would cause too much DCR and would lead to detonation issues correct?
Scenario 2.
Raise compression using the same methods above but used an extended duration intake cam and stock exhaust cam
Scenario 3.
Opposite of 2. Use a stock intake but extended duration exhaust
Thanks
IOW, don't get lost in the details and lose sight of what you are trying to accomplish. Don't use late IVC to reduce cylinder pressure; rather use it for better cylinder filling.
I'm not sure that your analysis of the cam change in the "kit" is for the reasons you cited. You might ask those who developed the kit. Not necessarily someone who just markets it, but the person who did the development work on it. You might be surprised.
My $.02
Jon
How about Scenario 4: Choose valve events (duration, centerlines and lsa) and lift that compliment the intake and exhaust tuning lengths to make best torque/power in your chosen rpm operating range, and then adjust SCR to run with your chosen fuel and do whatever is necessary for PV clearance.
IOW, don't get lost in the details and lose sight of what you are trying to accomplish. Don't use late IVC to reduce cylinder pressure; rather use it for better cylinder filling.
I'm not sure that your analysis of the cam change in the "kit" is for the reasons you cited. You might ask those who developed the kit. Not necessarily someone who just markets it, but the person who did the development work on it. You might be surprised.
My $.02
Jon
IOW, don't get lost in the details and lose sight of what you are trying to accomplish. Don't use late IVC to reduce cylinder pressure; rather use it for better cylinder filling.
I'm not sure that your analysis of the cam change in the "kit" is for the reasons you cited. You might ask those who developed the kit. Not necessarily someone who just markets it, but the person who did the development work on it. You might be surprised.
My $.02
Jon