A stupid question - what do uprated cams do?

[paz]

Hi All,

Apologies for what some will see as a stupid question, but I'm interested and have always wanted to understand this better.

In the simplest terms possible, what is it that uprated cams do? Do the cams on their own give you more power once fitted, or do they mean that you can change your mapping etc to increase power?

Also whats the degree measurement on the cams for? I know roughly its something to do with how extreme the cams are, but don't fully understand what it means.

Alternatively if you can point me in the direction of some good reading material that would do me a treat.

Thanks

Paz

 

[djdoc360]

In basic terms, Bigger cams will allow more air to enter the combustion chamber.

 

[rams_pulsar]

cams..

uprated cams give more power as the lobes on the camshaft are bigger and a different shape to the ones on the standards cams, with the lobes been bigger the allow the valves both inlet and exhaust to be open wider and for a longer period of time (were talking miliseconds but still longer than standard) at each revolution of the engine therefore giving more BHPs lol.

 

[frp]

http://en.wikipedia.org/wiki/Camshaft
http://auto.howstuffworks.com/camshaft.htm

steve

 

[gtir_pimp]

all of the above! they make your engine idle roughly depending on how wild the cams are, but its not an issue. you should have head work done to help

 

[EVOBAD]

not rally worth having only if your running over 400bhp as the strd cams are very good,i used strd cams on both of the 400bhp gtir i had

 

[Fast Guy]

Uprated cams can be longer duration and/or higher lift and of differing profiles. That effectively changes when the valves open, how much they open and how long for and allows more air into the cylinders and more exhaust gases out when running. As a result the engine often loses alittle power lower down the rev range and gains higher up the rev range. The amount of losses and gains depend how wild the cams are. Wilder cams can give you a limpy idle.

Vernier cam sprockets are recommended for dialling in uprated cams to get the most from them.

 

[paz]

Thanks chaps, much appreciated

Paz

 

[Jon Olds]

rolling road power curves, before and after

I would be appreciative if I couls see any before/after comparisons of the affect of a cam swap from std. If anybody has some graphs they would share. My interest is for a rally gtir. Alternately, if anybody has compared std cams with a bit more advance dialled in