Hey, i was just wondering about cams in general and how there timing plays such a crucial role in power, bassically i want to know what aftermarket cams do to free up power if anyone has time to explain id love to learn.

 

in a very quick nutshell, aftermarket cams are engineered to open the valves longer and more or at different intervals that are more beneficial to power.

 

What he said, and ya, basically more lift on the valves means more flow in and out=more air+more fuel=more power
they can also give you a really mean sounding idle

cheers
sohc

 

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

 

You're better off buying a book on cam function than trying to get someone to explain it to you. There's just too many variables that go into cam design. The main thing to keep in mind is that every cam is a compromise. Some target good gas mileage and smooth idle, while some are more geared for performance.

Stock cams are designed to please the most people and still get the best gas mileage possible. This means a smooth idle and good midrange power. After that, the engineers try to extract as much power as they can. But power isn't the primary function of a stock cam.

Performance cams come in a wide range of compromises. Street/strip cams sacrifice some idle and gas mileage for more horsepower, but still keep things relatively mild for decent street manners. All-out race cams sacrifice everyting for power. They're great at the race track but:

*you'd never pass emissions
*get horrible gas mileage
*have to set the idle around 2-3000 rpm to keep the engine running
*have no low end power to speak of

VTEC is Honda's effort to meet the EPA's mileage requirements while still providing enough power to satisfy the enthusiasts. It's like having a normal cam for street driving but being able to switch over to the race cam when the need arises. However, it's still possible to extract more power from the engine. Honda designed for reliability, but also to save money. Think about it - if the cost of a car rises by $1, it costs Honda millions. Anyway, by upgrading things like valve springs along with the cam, you can install a good street/strip cam and not affect reliability all that much. Or, if you're willing to accept a reduction in reliability (i.e., replace the valve springs once or twice a year), you can get a lot more power.

Your best bet is to call a couple of different cam companies and get their recommendations for your performance goals. But be realistic. If you're not going to mess with the bottom end for a while, tell them. Tell them if the car will need to pass emissions. Crane actually has a questionaire you can fill out. http://www.cranecams.com

Like I said, for a good explanation of cam function, you need to buy a book. But in a nutshell, longer duration equals more power up top but sacrifices power down low and hurts idle quality.

Higher lift makes more power, but is hard on valve springs and valve guides.

Lobe separation angle controls the power band somewhat. Narrowing the LSA raises peak power but narrows the power band. It also hurts emissions and idle quality. Widening the LSA broadens the torque curve but at the expense of peak power. Turbos and nitrous also benefit from wider LSA's, as the wider LSA helps dump the extra exhaust generated by power adders.

Advancing the cam improves low end power at the cost of high end. Retarding the cam does the opposite - it pushes the torque band higher up the rpm range for more horsepower, but costs you on the launch.

There's an old saying - "Speed costs money. How fast can you afford to go?" Assess your budget realistically and choose your cam accordingly.

HTH,

Stonebreaker




[Modified by Stonebreaker, 4:17 AM 1/6/2003]