Cam gurus inside
TECH Fanatic
Joined: Jun 2002
Posts: 1,979
Likes: 3
From: Upstate NY
You don't have to go camless to get variable overlap.... just have two cams for intake and exhaust and you can vary each centerline. You could just vary the exhaust cam like the Vortec 4200 I6 does. 50 crank degrees (25 cam degrees or LSA) is available there.
As for the square wave valve motion... that would be great if you didn't have inertia, both the physical parts and the air/fuel have inertia. You might also have a PV clearance problem banging the intake open near TDC of the intake stroke. Isn't it strange how all this stuff works together?
As for the square wave valve motion... that would be great if you didn't have inertia, both the physical parts and the air/fuel have inertia. You might also have a PV clearance problem banging the intake open near TDC of the intake stroke. Isn't it strange how all this stuff works together?
Last edited by Old SStroker; Apr 25, 2006 at 01:22 PM.
On The Tree
Joined: Jun 2003
Posts: 150
Likes: 0
Sad to say, this issue is too complicated to be solved by words. There are too many factors involved. I think anything short of a very complicated spreadsheet will be superficial at best.
As for piston speed vs valve lift, acceleration means nothing, speed means nothing, pressure means everything. If you didn't open your intake valve until BDC at the very end of the intake stroke, you would have severe low pressure in that cylinder (1/10 of atmosphere even). If you opened the intake right then, the gas velocity would be like nothing you'd ever seen. It would also be too short of an intake cycle to be worth anything. "Area under the curve" can make your brain hurt.
gas volume = gas speed * time
gas speed =? pressure difference / restrictions / inertia of air * a whole bunch of other crap that all changes contantly over time, while trying not to break your valvetrain off.
Please, someone post a spreadsheet.
As for piston speed vs valve lift, acceleration means nothing, speed means nothing, pressure means everything. If you didn't open your intake valve until BDC at the very end of the intake stroke, you would have severe low pressure in that cylinder (1/10 of atmosphere even). If you opened the intake right then, the gas velocity would be like nothing you'd ever seen. It would also be too short of an intake cycle to be worth anything. "Area under the curve" can make your brain hurt.
gas volume = gas speed * time
gas speed =? pressure difference / restrictions / inertia of air * a whole bunch of other crap that all changes contantly over time, while trying not to break your valvetrain off.
Please, someone post a spreadsheet.
11 Second Club
iTrader: (20)
Joined: Sep 2002
Posts: 2,684
Likes: 3
From: Albuquerque NM - The Land of 8000ft DA
Originally Posted by steve2001sh
Sad to say, this issue is too complicated to be solved by words. There are too many factors involved. I think anything short of a very complicated spreadsheet will be superficial at best.
As for piston speed vs valve lift, acceleration means nothing, speed means nothing, pressure means everything. If you didn't open your intake valve until BDC at the very end of the intake stroke, you would have severe low pressure in that cylinder (1/10 of atmosphere even). If you opened the intake right then, the gas velocity would be like nothing you'd ever seen. It would also be too short of an intake cycle to be worth anything. "Area under the curve" can make your brain hurt.
gas volume = gas speed * time
gas speed =? pressure difference / restrictions / inertia of air * a whole bunch of other crap that all changes contantly over time, while trying not to break your valvetrain off.
Please, someone post a spreadsheet.
As for piston speed vs valve lift, acceleration means nothing, speed means nothing, pressure means everything. If you didn't open your intake valve until BDC at the very end of the intake stroke, you would have severe low pressure in that cylinder (1/10 of atmosphere even). If you opened the intake right then, the gas velocity would be like nothing you'd ever seen. It would also be too short of an intake cycle to be worth anything. "Area under the curve" can make your brain hurt.
gas volume = gas speed * time
gas speed =? pressure difference / restrictions / inertia of air * a whole bunch of other crap that all changes contantly over time, while trying not to break your valvetrain off.
Please, someone post a spreadsheet.
assuming conservation of mass
On The Tree
Joined: Jun 2003
Posts: 150
Likes: 0
Originally Posted by sscam68
gas volume = gas velocity * cross sectional area.
assuming conservation of mass
assuming conservation of mass
On The Tree
Joined: Jun 2003
Posts: 150
Likes: 0
Originally Posted by SStrokerAce
Why post a spreadsheet? You don't get the concepts of how all of this works. A spreadsheet doing so would just be useless.
Bret
Bret
Originally Posted by steve2001sh
A spreadsheet would be good, because I could see all the formulas that went into it. I could figure out the math if I saw the equations. I think any good answer to your question won't be "at this degree" or "at that degree". It would be a rather long equation that I think would be easier to understand in spreadsheet form. Plus, if you don't understand the spreadsheet, you can still use it.
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