what is seat-to-seat vs cam timing @.050
11-21-2003, 09:26 PM
#2
Race Director
Re: what is seat-to-seat vs cam timing @.050 (bhmyers)
Seat to seat is the advertised duration of the cam ie: XE268 is advertised as
268 degrees duration. Since cams have different shapes or ramps they needed better place to measure the duration more accuratly for comparison
of one cam to the other so the usual starting and ending point is 0.050in. :D
268 degrees duration. Since cams have different shapes or ramps they needed better place to measure the duration more accuratly for comparison
of one cam to the other so the usual starting and ending point is 0.050in. :D
11-22-2003, 09:37 AM
#3
Race Director
Member Since: Mar 2001
Location: Living in the Hartland
Posts: 11,322
Likes: 0
Received 1 Like
on
1 Post
Re: what is seat-to-seat vs cam timing @.050 (MotorHead)
Seat to seat is the advertised duration of the cam ie: XE268 is advertised as
268 degrees duration. Since cams have different shapes or ramps they needed better place to measure the duration more accuratly for comparison
of one cam to the other so the usual starting and ending point is 0.050in. :D
268 degrees duration. Since cams have different shapes or ramps they needed better place to measure the duration more accuratly for comparison
of one cam to the other so the usual starting and ending point is 0.050in. :D
11-22-2003, 10:58 AM
#4
Le Mans Master
Member Since: Oct 2002
Location: Las Vegas - Just stop perpetuating myths please.
Posts: 7,098
Received 373 Likes
on
356 Posts
Re: what is seat-to-seat vs cam timing @.050 (bhmyers)
Seat to seat is measured differently from manufacture to manufacture. That’s why they try to use 0.050” for a comparison. What is significant is you need to look at seat-to-seat timing to figure out the amount of overlap (in degrees) for your lobe separation angle (LSA). Cams with the same 0.050” numbers can behave entirely different with different LSAs.
The tight LSA means more overlap – rougher idle, more mid-range torque, less top end rpm.
The wide LSA has less overlap – smoother idle, less max torque, more rpm and top end horsepower.
Good overlap numbers for the street? 40 to 60
Read this in the David Vizard books if you are interested. :seeya
The tight LSA means more overlap – rougher idle, more mid-range torque, less top end rpm.
The wide LSA has less overlap – smoother idle, less max torque, more rpm and top end horsepower.
Good overlap numbers for the street? 40 to 60
Read this in the David Vizard books if you are interested. :seeya
11-22-2003, 11:03 AM
#5
Re: what is seat-to-seat vs cam timing @.050 (MotorHead)
Seat to seat is the advertised duration of the cam ie: XE268 is advertised as
268 degrees duration. Since cams have different shapes or ramps they needed better place to measure the duration more accuratly for comparison
of one cam to the other so the usual starting and ending point is 0.050in. :D
268 degrees duration. Since cams have different shapes or ramps they needed better place to measure the duration more accuratly for comparison
of one cam to the other so the usual starting and ending point is 0.050in. :D
It is quite habndy for comparing ramnp designs however, if you have two 274 cams and one has a longer duration @ .050 that can has more aggressive lobe profiles.
