- for a DOHC engine, 1600cc, 4 speed automatic transmission.
- what benefits are there if the camshafts were upgraded from the stock unit to a high performance unit?
- highcams have longer duration and higher lift... higher valve lift means more air/fuel mixture can flow into the combustion chamber... more air/fuel, more bang, more power.... longer duration means the valve is allowed to open as long as possible... same theory, to allow more air/fuel enters ur combustion chamber... its the same application as for exhaust valve (since u using DOHC, intake and exhaust valve is independently controlled by different camshaft)
- what shortcomings will there be? (example, increase in petrol consumption?)
- depending on what camshaft u using... race-cams (272degree above) usually will have more power increase at higher rpm, less stable idle rpm, abit higher fuel consumption... half-race cams (272degree below) will have less significant power increase, but powerband starts at a much lower rpm range, better stability of ur rpm at idle and aircond switched on, less effect on fuel consumption...
- what about ported & polished cylinder heads? What does it do?
- to maximize volumetric efficiency flow into ur combustion chamber... in other words, to allow air/fuel mixture to flow more freely into the combustion chamber... over ported heads can cause less power increase and worse fuel consumption... this is because velocity of liquid flow doesnt necessarily increase with the size of the pipe/hole...
- adjustable cam pulleys? What does it do?
- to adjust ur camshaft settings... either advance or retard... advance for better pickup, retard for better top end... people usuall retard it for higher bhp gain at peak power rpm.... advancing the timing till help throttle response at low end, but sacrifice top end power... adj campulley is important to get a good tuning for high camshaft...
