When to open the intake valve on a fixed camshaft?
Also, a fixed camshaft might open the intake valve 10° before TDC (BTDC) and close it 5° after bottom dead center (ABDC) and open the exhaust valve 15° before bottom dead center (BBDC) and close it 5° ATDC. This is referred to as valve opening duration. This works well on average but doesn’t excel in any one driving situation.
How does the timing of the camshaft affect the engine?
Timing is important. Valves must open and close at specific intervals in relation to cylinder position. For example, as cylinder #1 is coming to top dead center (TDC) on the exhaust stroke, the camshaft is opening the intake valves and closing the exhaust valves.
How does the camshaft synchronize with the crankshaft?
This is a process that synchronizes the camshaft with the crankshaft. For best engine performance, builders use a degree wheel to dial in this measurement. Most manufacturers will list the exact specifications for each cam on the cam card. The length of time the valve is held off the valve seat from the cam lobe.
How are intake and exhaust points calculated on a cam card?
Cam cards publish these points based on the manufacturer’s chosen reference points: typically 0.006 inch for advertised duration and 0.050 inch for a universal checking reference based on an agreed amount of lobe lift where reasonable flow is initiated. The following formula is used to calculate intake and exhaust duration.
What should the intake centerline of a cam be?
The cam manufacturer has a pretty good idea where the cam should be installed, and you frequently see this listed in the cam specs. If a cam has a recommended intake centerline of 110 degrees and the LSA is 112 degrees, the cam is 2 degrees advanced (112 degrees – 110 degrees = 2 degrees).
What happens to the intake valve when the cam is advanced?
When the cam is advanced, the intake valve closes sooner, so you get more power at the low end. Reducing the lobe separation anglealso causes the intake valve to close sooner, so you again get more low end power.
When does a cam line up with the crankshaft?
When a cam is installed “straight-up,” the imaginary centerlines of the two shafts line up exactly. Advancing or retarding the cam pushes the centerline of the camshaft to one side or the other of the crankshaft centerline.
What happens when a cam is installed straight up?
When a cam is installed “straight-up,” the imaginary centerlines of the two shafts line up exactly. Advancing or retarding the cam pushes the centerline of the camshaft to one side or the other of the crankshaft centerline. This changes the Timing of the valve opening and closing events, in relation to the position of the piston in the cylinder.