Cam, Camshaft and Campro...

Published: Thursday, 31 December 2009 Written by Abang Wan

Salam all,

Now I've been in a dilemma for a while, cause I was thinking, What I want to write about?? ZzZZz... As a lazy human being, I dun want to write something that is some what too long and too complex even I don't understand, but also not to simple that the people at kedai makan already knows. Ya ya I know some of you guys might say, " Don't blog la if like that, go sleep better..." Actually I wants the things I blog is useful to you and me, a new knowledge to some and notes for me...

Ok enough mumbling, the topic for today is Cam or Camshaft, what is it? What it does?.

Explanation of camshaft that commonly being told is:

A valve train consists of valves and a mechanism which opens and closes them. The opening and closing system is called a camshaft. The camshaft uses lobes (cams) that push against the valves to open them as the camshaft rotates; springs on the valves return them to their closed position. This is a critical job, and can have a great impact on an engine's performance at different speeds.

The key parts of any camshaft are the lobes. As the camshaft spins, the lobes open and close the intake and exhaust valves in time with the motion of the piston. It turns out that there is a direct relationship between the shape of the cam lobes and the way the engine performs in different speed ranges.

Lift
Lift refers to maximum valve lift. This is how much the valve is "lifted" off its seat at the cam lobe's highest point. The intake and exhaust valves need to be open to let air/fuel in and exhaust out of the cylinders. Generally, opening the valves quicker and further will increase engine output. Increasing valve lift, without increasing duration, can yield more power without much change to the nature of the power curve. However, an increase in valve lift almost always is accompanied by an increase in duration. This is because ramps are limited in their shape which is directly related to the type of lifters being used, such as flat or roller.

Duration
Duration is the angle in crankshaft degrees that the valve stays off its seat during the lifting cycle of the cam lobe. Increasing duration keeps the valve open longer, and can increase high-rpm power. Doing so increases the RPM range that the engine produces power. By increasing duration without a change in lobe separation angle will result in increased valve overlap.

A matspeed cam with 275 degree

Overlap
Overlap is the angle in crankshaft degrees that both the intake and exhaust valves are open. This occurs at the end of the exhaust stroke and the beginning of the intake stroke. Increasing lift duration and/or decreasing lobe separation increases overlap. At high engine speeds, overlap allows the rush of exhaust gasses out the exhaust valve to help pull the fresh air/fuel mixture into the cylinder through the intake valve. Increased engine speed enhances the effect. Therefore increasing overlap, increases top-end power and reduces low-speed power and idle quality.

Timing
The relationship between the rotation of the camshaft and the rotation of the crankshaft is of critical importance. Since the valves control the flow of air/fuel mixture intake and exhaust gases, they must be opened and closed at the appropriate time during the stroke of the piston. For this reason, the camshaft is connected to the crankshaft either directly, via a gear mechanism, or indirectly via a belt or chain called a timing belt or timing chain. Direct drive using gears is unusual because the frequently-reversing torque caused by the slope of the cams tends to quickly wear out gear teeth. Where gears are used, they tend to be made from resilient fibre rather than metal. In some designs the camshaft also drives the distributor and the oil and fuel pumps. Some General Motors vehicles also have the power steering pump driven by the camshaft. Also on early fuel injection systems, cams on the camshaft would operate the fuel injectors.

In a two-stroke engine that uses a camshaft, each valve is opened once for each rotation of the crankshaft; in these engines, the camshaft rotates at the same rate as the crankshaft. In a four-stroke engine, the valves are opened only half as often; thus, two full rotations of the crankshaft occur for each rotation of the camshaft.

The timing of the camshaft can be advanced to produce better low end torque or it can be retarded to produce better high end torque.

{youtube}nsa6kq-qqIE{/youtube}

Hopefully with that explanation, some enlightenment has occur. Now, in relation to campro I'm going to tell a bit of what I know about the many varieties of cam for campro. The 1st and foremost as we all know is Matspeed, they are workshop/machine shop that have the tools to regrind the original cam to a different degree. Matspeed have quite few variant or degrees for campro. If I remember correctly, in the year 2007 they start with 258 degree for both intake and exhaust then move to 260, until 272 but then suddenly all people start reverting back to smaller degrees, why? Because at this time not many campro were equip with standalone so the stock ecu can't handle the air-cond and lumpy idle so generally people thought that campro can't used a very high degree cam. After some time someone has come up with scatter cam for campro and then the cam scene erupt again with new degree of scatter. The 1st set of scatter cam that have a good result with campro are 266/260 for intake and 260 for exhaust, there are other before this but this setting are proven in SDB(Sepang Drag Battle) at the time.

Now(2010) the list of scatter cam that I know of are(it could be more):

intake exhaust
258/262 260
262/266 262
260/278 260
268/272 260

Others then Matspeed what else? I've heard of powerzone but that was a long time ago, start from 2008/09 I seldom heard about it anymore. There are also R3 cams, and they are famous at the time they come up with it. I've a friend that used this cam, even though the degree was not that high but the performance on the road was surprisingly good. I've been told the degree was 258 intake and 260 for exhaust.

The last but not least, Works Engineering billet cam, this cam is for me a very-very new, only a few month since launch. I have never seen the actual performance of a car that is equip with this cam, all I've heard was only the rough dyno figures. In term of theory billet cam is better then regrind but for now we just have to wait and see and hopefully in drag scene especially MUSC, Works Eng cam will show their best results. The specs for this cam, 267 degree for intake and exhaust with 10.6mm lift, that's quite a high lift and that means a very-very good news.

I think thats all for now.

Salam.