Little help someone?, Mechanical question Options

[Wishful3S-GTE]

My knowledge on mechanics is very limited but I'm not completely in the dark. I was just wondering what the measurements of the cam gears represent. Like 256 for example and why tuners use diff sizes or angles or whatever it represents for each cam.

[SpedToe169]

There are a number of different parameters that define a cam. Just a few of them are: Lift, duration, duration at 0.050, IVO angle, IVC angle, EVO angle, EVC angle, overlap, and a few others.

Lift is just the total lift of the cam lobe, i.e. the difference between the base circle radius of the cam and the radius of the point of max lift. Duration is how long (in degrees that the valve is open. It can also be defined as the number of degrees where the lobe radius is greater than the base circle radius. Duration at 0.050 is just used to get an idea of how steep the ramp on the lobe is. The four different angles are Intake Valve Opening and Closing angles, and Exhaust Opening and Closing angles. Overlap refers to the number of degrees that the exhaust valve remains open after the intake valve has begun to open.

Different values of these parameters will produce vastly differently behaving engines as well as producing different power and torque numbers at different rpm. There are a lot of things that will determine what cam will work best for what application. I really don't have time to go in to it all, there have been many books written on the subject, its that complex.

Also check out:

http://auto.howstuffworks.com/camshaft.htm

for answers to some other questions you'll probably have. If you have more specific questions, let me know and I'll try to help you out.

[Wishful3S-GTE]

Thanks for the explanation on the terminology. I've been to howstuffworks before and read that already but I read it again and it makes a helluva a lot more sense all of a sudden. I'm still interested in what the measurements represent. Like when you see cam gears that are labeled 256 or somethin to that effect. Any explanations on this?

[SpedToe169]

No problem.

You'll probably never see cam gears stamped with a 256 or anything. You might see something like that on the cam itself. Manufacturers often don't want to divulge the exact numbers for the cams they've developed. It would make it way too easy for the competition to copy them and all their R&D money would be lost. As a result they often just give it a number....kinda like a part number that kinda means something. Sometimes is the max lift, sometimes the duration but its usually not enough information to really tell whats going on.

Cam development is a really complex undertaking. I'm an engineer for a world challenge touring car team and I know of some competing teams that have spent huge bank in this area. Its possible to get an idea what a particular cam grind will do using engine simulation software. This is where most cams are born. Then they're gound, dyno tested, degreed, dynoed, degreed, etc until the desired result is achieved. At this point it depends on how serious the tuner is. It often takes several iterations to get one just right. So to really develop a cam for our cars, you'd have to do that whole process at least 6 times (3 for intake and 3 for exhaust) to really tweak it out. Many companies don't take things near this far but most race teams do. We've got 3 sets of cams that were $5k each. Most of that cost is because of the development, not the actual parts.