what does a cam do?

[quader400]

what it says. what does getting a better cam do. what gains do you get?

[TCracin440ex]

a cam takes pictures











j/k no a cam opens and closes the valves....

[TCracin440ex]

i think having a better cam either opens and closes the valves faster or it opens the valves up more...im not sure which 1 it is...

[nosliw]

depends, i guess.

lobes designed for different lift/duration pretty much tell your engine what kind of power it is allowed to have. not an expert though.

[duke416ex]

Duration has to do with the length of time between when the intake and exhaust valves open. Lift has to do with how much the valves open. Different combinations will give you different amounts of power at different times throughout the rpm range.

[2004exrider]

pretty much, a bigger cam will let in more air and for a longer amount of time compared to a stock cam. the lift decides how much air will go in, the duration will decide how long it will let the air in.... so much more power

[wilkin250r]

Ok, first of all, forget everything everybody else just typed. It's not all false information, it's just really hard to understand.

To explain a camshaft, you need to understand how your engine works, the piston, intake valves, and exhaust valves. Learn what makes a 4-stroke engine work.

The camshaft will control the opening and closing of the valves. In theory, the intake valves should open when the piston is at the top, and close when the piston reaches the bottom. The opposite is true for exhaust, the valves should open when the piston is at the bottom, and as the piston moves up it will push all the exhaust out, and they close when the piston reaches the top.

Well, this is all well and fine up to about 2000rpm, barely above idle speed. Any faster, and a different set of physics begins to have more effect. Lie down and put a baseball on your head, and no problems. Drop that same baseball from 2ft on to your head, and you begin to appreciate the physics of MOVING objects, dynamics. Now, drop that baseball from 30ft, and you REALLY begin to understand. Even air has inertia.

To explain all the different effects is very difficult and time-consuming. You can do research on the net, or search for threads here in this forum. But, in a nutshell, an aftermarket camshaft will have different profiles, different ways of adjusting the valve timing. However, it's often a trade-off, the way to make good top-end power gives poor low-end power. That's why you have different cam profiles, for different engine characteristics.

[duke416ex]

I was trying to just explain it in a little simpler way, I just figure if you are asking what a cam does they don't have the whole engine process down. I was going to try to leave out all the in depth physics of everything about the inertia and floating valves, but however you want to explain it.

[wilkin250r]

Well, you can say that the cam controls the valve timing, but if they don't know how the valves work, then how useful is the information?


I realize you're trying to explain it in simple terms. I am trying to paint the picture that it cannot be explained in simple terms.

[duke416ex]

Not trying to argue, I just use it as a way to explain to someone who has no idea, but not saying this guy has no idea. But a cam controls when, how much and how long the valves open. I always saw that as a pretty straight forward very watered down explanation. I know that the cam does this based on yadda yadda yadda, but I was just saying what the cam did.

[wilkin250r]

If what if I told you that a higher AL value means a larger inductance. Does that clear everything up, as far as your knowledge of electronics?

It's a very simple explanation, and it's absolutely accurate. However, you don't know what the AL value is, what it means, or the effects of it, and aren't all too clear on exactly what inductance is. So my little, over-simplified explanation really hasn't helped you one bit.

Do you see the correlation? If he doesn't KNOW how the valves work and what they do, then what good is the information about the camshaft and the timing?

[duke416ex]

Like I said I don't care to argue, you do it your way and I'll do it mine. Hopefully someone said something that helped, that's all I was trying to do, as you and everyone else were too.

[sickstrtcar]

calm down wilkin, and ur kinda wrong on the hole valve opening and closing deal...intake is open on the down stroke of the piston(sucking air and fuel in)...the exhaust valve is open on the up stroke of the piston(pushing the gases out of the engine)

[wilkin250r]

Not wrong. Read again.

[400exrules]

Originally posted by sickstrtcar
calm down wilkin, and ur kinda wrong on the hole valve opening and closing deal...intake is open on the down stroke of the piston(sucking air and fuel in)...the exhaust valve is open on the up stroke of the piston(pushing the gases out of the engine)


uh....thats wut he said:huh re-read it

[sickstrtcar]

my bad... read it wrong

[F-16Guy]

I'm just waiting for the quad world to catch up to the import world. Imports, like the Civic, have variable valve timing (V-TEC; valve timing electronically controlled). That does essentially what ignition advance does for spark. It allows the ideal time for the valves to open and close, with regard to engine RPM, to change. That's why, among other things, different cam grinds give you different power curves. The valve timing is effectively locked in place, and the engine must reach the RPM range that the intake and exhaust flow most efficiently at. It's give and take without variable valve timing. If you have a grind that flows well at low RPM, it probably won't flow so well at high RPM, and vice versa.

[wilkin250r]

That's not easy to do. It's not just timing for opening, but also variable duration, so you can't just have a solid camshaft and advance or retard it. You would need to be able to indepentently control both timing AND duration, like a solenoid on each valve, and a microprocessor to manage it. As if 4-strokes aren't heavy and complicated enough, now you want to add MORE to the cylinder head, and make the motor even taller and heavier than it already is?

[wvspeedfreak]

I just had a baseball dropped on my head from 30 ft. up and .........................................hold on what were we talking about?