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Is valve overlap good?
Valve overlap is designed into the engine and is most useful at higher speeds. At higher speeds, the extra amount of intake charge brought into the combustion chamber provides a substantial increase in available power. The amount of time that both valves are open in directly related to engine rpm.
What results in the used of a high degree of overlap in at lower engine speed?
Generally, the torque at higher engine speeds and loads can benefit from increased overlap due to pressure waves in the exhaust manifold aiding the inlet of fresh charge. Large amounts of overlap result in poor emissions at lower speeds as fuel from the inlet charge can flow directly into the exhaust.
What does valve overlap do?
As discussed previously, valve overlap is the time when both intake and exhaust valves are open. In simple terms, this provides an opportunity for the exhaust gas flow and intake flow to influence each other.
What keeps the engine running faster under a load?
Force is mass*acceleration; the mass of the piston is constant, it means there is an increase in the acceleration of the piston and hence the speed. So with nodoubt, it can be said that ‘The speed of the engine increases due increase in the load (air+fuel) on the engine”.
How can you tell if a valve is overlapping?
Overlap can be calculated by adding the exhaust closing and the intake opening points. For example, a cam with an exhaust closing at 4 degrees ATDC and an intake opening of 8 degrees BTDC has 12 degrees of overlap.
Is it good to put an oxygen sensor on exhaust?
Adding an oxygen sensor to the exhaust is a great tuning aid if it is used properly. However, it isn’t a magic cure-all and you need to understand how the sensor works to truly get the most benefit out of one. Overlap is defined as the amount of time (in crankshaft degrees) that both the intake and exhaust valves are open simultaneously.
How does overlap affect the performance of an engine?
Generally, the torque at higher engine speeds and loads can benefit from increased overlap due to pressure waves in the exhaust manifold aiding the intake of fresh charge. Large amounts of overlap tend to result in poor emissions at lower speeds as fuel from the intake charge can flow directly into the exhaust.
Why does my car have a lot of overlap?
Overlap is what creates that desirable lumpy idle for street engines. The problem occurs when an excessive amount of oxygen makes its way from the intake port directly into the exhaust at idle and low engine speeds because of overlap.
How does a comp CAM work on an O2 sensor?
This Comp Cams drawing reveals the relationship of exhaust closing and intake opening to overlap. As overlap increases, that little triangle becomes larger, which will allow more free oxygen into the exhaust and fool the O2 sensor at idle. This will compare the overlap of two camshafts. Most cam cards will deliver all the information you need.