How do cams work?

[1sty]

Answer these questions and win NOTHING (thumb)

I want to get this info centralized.

1. Why does changing a cam add any benifit?

2. How can the car accmidate a difference in cams if it is timed very stricly to work with the stock ones?

3. Can cams cuase detonation in the wrong installation?

4. Is changing an intake cam useless without changing the exhuast cam?

Feel free to add your questions and answers!

 

[JunkPunch]

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

 

[1FASTMP5]

well, i do have cams in and there is no detonation going on. the affects have been:
my power curve moved up 500rpm's i shift @6900rpm's when im racing now.
it seem's that the cams make the most differance after 4000 rpm's
my strongest gears used to be 1st & 2nd....now 3rd and 4th fell a hell of alot better.
i did notice something stange though... my car doesnt cold start idle high anymore. when i start it in the morning it just idle's @1100rpm's until it warm's up then it drop's down to 700rpm's.
the idle's fine cold, warm or when ever i start it, it just doesnt idle @2000rpm's at cold start like it used to????:wtf:

 

[changedman]

cool, good info, ive been looking for some new ones and this info is mucho helpful

 

[DooMer_MP3]

well, i do have cams in and there is no detonation going on. the affects have been:
my power curve moved up 500rpm's i shift @6900rpm's when im racing now.
it seem's that the cams make the most differance after 4000 rpm's
when i go on the freeway now crusin @ 80 mph my car only tac's @3500rpm, as were before i got the cams i would almost be tacing 4000rpm's.
my strongest gears used to be 1st & 2nd....now 3rd and 4th fell a hell of alot better.
i did notice something stange though... my car doesnt cold start idle high anymore. when i start it in the morning it just idle's @1100rpm's until it warm's up then it drop's down to 700rpm's.
the idle's fine cold, warm or when ever i start it, it just doesnt idle @2000rpm's at cold start like it used to????:wtf:

I agree that the cams most likely moved your powerband up, but they are NOT going to change the RPMs at which you cruise etc. The only way to change that is through gearing (ie the tranny). Regardless of what performance mods you add to an engine, the RPMs will still be the same at a certain speed.

Chris

 

[1FASTMP5]

I agree that the cams most likely moved your powerband up, but they are NOT going to change the RPMs at which you cruise etc. The only way to change that is through gearing (ie the tranny). Regardless of what performance mods you add to an engine, the RPMs will still be the same at a certain speed.

Chris

i agree with you completely, i know that gearing changes these things. im just trippen right now.... because i just remembered that i changed my rims two at the same time. and didnt even think about it. (lol) (hand)

 

[122 Vega]

1. Cams can change the amount of time a valve stays open, therefore letting more air/fuel in or out, changing volumetric efficiency. The one spec that makes the most difference is intake valve close degree.

2. Accomodate? The ECU may alter timing to accomodate the increase or decrease in air/fuel. The o2 sensor readings may change, causing the ECU change. But this is not likely.

3. I do not believe that cams can cause detonation, however, if the duration is so far off or the overlap is so great, you could have ignition when the valve is open and that would case a few probs, maybe burned exhaust valves or intake backfiring. Any properly installed cam from a reputable cam company should be just fine. Keep in mind with turbo cars, 110-112 degrees of overlap is best.

4. Most cars flow better of the exhaust side, mostly due to the fact that exhaust gas is hot and can move at high velocity. It cools later, this is why you often see stepped diameter headers. Buy the intake first, then add the exhaust later if you want.



p.s. There is no possible way that changing cams will change engine RPM whild cruising, this is more likely the effect of changing tire diameter or something else. This is simply against the laws of mechanics and physics.

Britt

 

[1sty]

How do you determin cam overlap?

 

[122 Vega]

That is the center line difference between intake valve max lift and exhaust valve max lift. THis is one of the thing that is modified when you add adjustable cam gears. It is usually determined by the manufacturer, this has a big effect on emissions as well.

Britt