Camshaft/Breathing question

[Chassis 33]

Hi folks, sorry for all the recent questions doing a lot of ummm'ing and argh'ing at present.

If you have an engine built with a camshaft that has a listed usable rev range of 1200-6200rpm but peak power is reached before 6200rpm does this indicate that the rest of the engine is not optimised for the cam, either in terms of breathing (both volumes and lengths), ignition and/or fueling? (All assuming the cam is correctly timed)

Regards
Iain

[stevieturbo]

I guess it could mean a lot of things....


And the only "correct" cam timing, is that found on a dyno. Simply installing to reccomended numbers, is not optimising the cam for the setup either.

[Snake the Sniper]

The usable band will nearly always extend (slightly) beyond peak power, but depends upon how quickly the engine falls off the cam. Some can carry 90+% of the power on for 1000RPM, some may be a few rpm. Usable revs and peak power are rarely at the same place. IE, it may be worth driving the engine past peak power (but still within the usable revs) to allow you to drop back to a better point on the torque curve.

[Chassis 33]

Cheers folks, I'm just looking at my last RR print out and seeing if I can get anything meaningful out of it in terms of where performance can best be improved. The engine runs a max of 243hp and is above 240 from 5100 to 5900 so has as decent plateau, but I'm wondering if I could get more power if the peak was moved up towards the maximum usable limit of the cam, revs x torque and all that.

Regards
Iain

[GreenV8S]

Two thoughts:

the rev range should extend beyond peak power. As a rough guide you should be able to take the engine up to the red line, change up and have a similar power available in the 'new' gear. What this means in terms of numbers depends on the gearing and the shape of the power curve, but you should be planning to take the engine past peak power before changing gear if you're trying to extract maximum performance.

1200 - 6200 doesn't sound like a particularly revvy cam, but what are the maximum revs your engine can sustain? No point putting a cam in that has a power band from 4000-8000 rpm if the mechanical red line is 6200 rpm.