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paulyg · 02-10-2003, 09:21 PM

geerboy, I'll give this a go at explaining the benifit's of cam gears. The cams have lobes that stick out from the round shaft. Imagine an egg rotating on a stick. The top of the egg is what pushes the rocker up which then pushes the valve down. The rocker acts like a sea-saw, the cam end goes up, the valve end goes down. Now every cam "profile" or lobe has a centerline.

The lobe center is either the highest point on the lobe OR exactly in the middle (measured in degrees of cam rotation) of the start and end of valve lift. The reason I qualify the two different senarios is b/c we usually think of the cam profile as symetrical, but it may not be. So the purpose of the cam gears is to move the "lobe centerline" just a little to the "left" or to the "right". We say you are advancing or retarding the the centerline b/c it is happening sooner in the cam's rotation (advance) or later the the rotation (retard).

How does this help you tune your car. Well you are effectively changing when you engine breathes in & out. If you advance the intake cam, you make the engine take in air 1, 2, 3 degrees sooner then it normally would. At higher RPMS, you want the intake to open sooner, at low RPMs it might hurt. Now also take into account that you are making small adjustments so you get a small effect.

The other thing this does is change the amount of time the intake and exhaust are open together. This can also change the dynamic of the enigne. Engines like small over lap at low RPMs and low throttle openings, and larger overlap at high RPMs and wide open throttle.

Now for the other benifit of cam gears. When cams are made they are ground into proper shape. Like all machining processes, there is some error and variation involved. The cam profile may be a little "off" from perfect. The cam gears help make up for this. This is why cam gears are really good if you have aftermarket cams. Aftermarket cams are suseptable to more variation b/c they use the same machine to grind an H22 cam and a mustang cam. Every time an H22 can is made, the machinist has to "set up" the equiptment. On Honda's production line, the same machinies do nothing but produce the same cam over and over. And honda can afford to invest in "jigs" which can take much of the human "set up" out of the eqation. That is why cam gears are really good on aftermarket cams.

Hope all this helps, and please correct me if I have missed or misconstrued anything.

02-10-2003, 09:21 PM	#8 (permalink)
paulyg loving and hating my Lude Join Date: Nov 2002 Location: Terrorizing other drivers in Killadelphia, PA Posts: 1,455 iTrader: (0)	geerboy, I'll give this a go at explaining the benifit's of cam gears. The cams have lobes that stick out from the round shaft. Imagine an egg rotating on a stick. The top of the egg is what pushes the rocker up which then pushes the valve down. The rocker acts like a sea-saw, the cam end goes up, the valve end goes down. Now every cam "profile" or lobe has a centerline. The lobe center is either the highest point on the lobe OR exactly in the middle (measured in degrees of cam rotation) of the start and end of valve lift. The reason I qualify the two different senarios is b/c we usually think of the cam profile as symetrical, but it may not be. So the purpose of the cam gears is to move the "lobe centerline" just a little to the "left" or to the "right". We say you are advancing or retarding the the centerline b/c it is happening sooner in the cam's rotation (advance) or later the the rotation (retard). How does this help you tune your car. Well you are effectively changing when you engine breathes in & out. If you advance the intake cam, you make the engine take in air 1, 2, 3 degrees sooner then it normally would. At higher RPMS, you want the intake to open sooner, at low RPMs it might hurt. Now also take into account that you are making small adjustments so you get a small effect. The other thing this does is change the amount of time the intake and exhaust are open together. This can also change the dynamic of the enigne. Engines like small over lap at low RPMs and low throttle openings, and larger overlap at high RPMs and wide open throttle. Now for the other benifit of cam gears. When cams are made they are ground into proper shape. Like all machining processes, there is some error and variation involved. The cam profile may be a little "off" from perfect. The cam gears help make up for this. This is why cam gears are really good if you have aftermarket cams. Aftermarket cams are suseptable to more variation b/c they use the same machine to grind an H22 cam and a mustang cam. Every time an H22 can is made, the machinist has to "set up" the equiptment. On Honda's production line, the same machinies do nothing but produce the same cam over and over. And honda can afford to invest in "jigs" which can take much of the human "set up" out of the eqation. That is why cam gears are really good on aftermarket cams. Hope all this helps, and please correct me if I have missed or misconstrued anything. __________________ Paul 1990 Mazda Miata - #181 STS2 1999 Crystal Blue Base - Retired to Daily Driver