Hi guys

I have been looking at the idea of having some new columbo and barini cams fitted to my coop(although they are proving quite difficult to source).Could somebody explain to me the difference between the standard cams and the above?

Thanks for your help

"bariani"

C&B are slightly higher lift and longer duration (as well as differently timed)

sorry nigel,stupid mistake. could you simplify that for me?What are the benefits of the different timing?

I might learn to spell one day

I believe these cam advance your ignition giving more power and a better mid to high range and some more horses

higher lift and longer duration means the valves open more and stay open for longer.

ninja

Cams have nothing to do with ignition

basically, an engine is a pump - the more air you can get in (and out), the more efficient it will be (or the more power it will give)

Think of it this way - a standard Coupe will produce about 220bhp at its peak - ie its working absolutely flat out.

My Coupe will produce 220bhp at about 2/3 throttle and at far less revs than standard, so its using less effort (and thus, less fuel) to produce the power.

The way to achieve these gains is to make the 'pump' more efficient - to do this, we remove as many restrictions as is possible. One of the biggest restrictions is the cylinder head, and particularly, the valves.

Valves are measured in three ways - lift, duration and timing. Lift is how far they open and duration is (predictably) how long they are open for and timing is when they open (and close)

the standard cam timing is designed to produce adequate power with decent torque and OK(ish) fuel consumption.

Changing any (or all) of the cam's attributes can change the way an engine behaves. It might produce more power. It might produce less power, but with more torque. It might increase the revs needed to produce the power, or it might extend the rev range over which it makes the desired power.

Note that cam timing is critical, but it also has funny effects, dependent on revs. At low engine speeds, timing of the valve needs to be very different to high engine speeds. This is all to do with the speed of the inlet charge entering the cylinder. At low speeds, there is no problem filling the cylinder, but at higher engine speeds, the pistons are moving much more quickly, meaning there's far less time (like 1/200 of a second at 6,000rpm) to open the inlet valve, get the fuel/air mixture into the cylinder and get the valve close again. This is why many modern engines use camshaft variators to alter the timing of the inlet cam (and sometimes, but rarely, the exhaust cam) to provide different characteristics at different revs.

For a truly innovative design, look at the new Fiat MultiAir engine, which doesn't use an inlet cam at all - it now uses pnuematically-controlled valves to deliver the air to the cylinder (and at some revs, the valve opens and closes more than once per cycle - very clever)

There - Sunday AM tech lesson

Nigel, that's excellent and very informative

RPM is obviously fixed constant in power/ torque and power is derived from torque and RPM, so all these cams do essentially, is move the torque curve around a bit.

I was talking to Rog about C&Bs yesterday night, and he was saying that there's no loss of torque in the rev range, only gains. If so, then why don't manufacturers just fit more aggressive cams to all cars? Fuel economy?

They do fit them if you buy a ferrari or a zonda but not a 20k fiat there built to be eco friendly and as safe as posible and at cost

Trappy - agressive cams often lead to an aggressive power curve. Its all very well having a high peak power, but if there's bugger all below 3,000rpm, it won't be a pleasant drive.

Most cams are a compromise, its just that for standard road cars, the compromise is towards low and mid power, and smooth delivery.

If you can put up with worse fuel consumption, peaky power delivery and a shorter powerband, there are almost always some useful power gains to be made.

Personally, I prefer a big, broad spread of power, but unfortunately, I can't afford to run a big-cube engine, so a turbo small-block is the next best thing

From my mini days i got quite serious into engine building(spent some time with a partner of David Vizards in the states and picked a few things up) and all i can say about cams is:

Never buy cams from a manufacturer that doesnt give advice on the compression ratio you should run or doesnt ask you what compression ratio you are running

Cams have a direct link to your compression ratio, the first being your dynamic compression ratio and the second being what static compresion ratio you should run.

A big reason people lose alot of grunt in the lower revs is because they havnt fitted the cam properly, in some cases on a NA engine all that is needed to regain the bottome end is an increase in the static compression ratio by about 0.2/3 points.

On turbo engines its a different ball game all together and best left to a specialist that does ask about your static compression ratio in order to be sure the cams will work to the best of their abilities sometimes just a tweak on the timing is all that is needed rather than altering the static compression ratio.

People that say cams are not worthwhile im afraid have not got a clue, well designed and installed cams can give an increase all across the board but most of the time with a better urge at the top depending on duration and lift.

In fact if you wanted more grunt from the lower revs this can be made possible with a well designed cam profile although you will lose out at the top and cannot gain that back unlike the previous situation i mentioned above where you can have your cake and eat it.

Davie

thats very informative lads,thanks very much.
I have learned quite a bit their.

OE manufacturers are not really driven by out and out performance, they are more worried about meeting emissions and durability. They don't want any nasty recalls if they can help it and tend to play safe. There are loads of considerations on their list before providing more than ample performance, that's easy enough at high street levels.

Nik