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Having the exhaust valve still open when the intake starts to open uses the exhaust "pull" out the exhaust port to help start the intake charge entering the chamber -- before the piston has started down and has generated it's own vacuum. Also, leaving the valves open longer (duration) increased the density of the intake charge and allowed the headers to better scavenge the exhaust gasses out.
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How important to change PCV valve Nissan pickup 1994?
It is very important to change PCV valve. If valve is old it will plug or seize. This will cause oil pressure to rise and may cause leaks. Most likely the valve cover gaskets will leak if PCV valve is plugged.
What is overlapping of valves?
Valve overlap occurs in a four-stroke engine at the end of the Exhaust stroke and at the beginning of the Induction stroke; and is when both the exhaust and inlet valves are open at the same time. At the end of the Exhaust stroke, the Exhaust valve is closing and the Inlet valve is starting to open in preparation for the induction of fuel and air into the cylinder. It is common knowledge that in vehicles that cannot alter the valve timing, the Inlet valve opens approx 6 degrees before top-dead-centre and the Exhaust valve closes at 9 degrees after top-dead-centre
What makes flames come out your exhaust?
Usually a product of valve overlap and exhaust. It's basically unburnt fuel coming through and igniting on the hot exhuast tip when it hits the air at the end of the exhaust pipe. In aspirated cars it's large valve overlap which helps scavenging and performance in the top end. Turbo cars, due to the large amounts of fuel at full noise. Normally happens after high RMP then throttle snapped shut.
For what reasons may an aortic valve replacement surgery be needed?
Aortic valve replacement surgery will be required if the valve in the heart is either too narrow for all of the blood to pass through or if the valve is leaking. This valve is very important as it prevents blood from rushing back into the heart after it has been pumped out.
What is the prognosis for aortic valve insufficiency?
The faulty working of the aortic valve can be caused by a birth defect; by abnormal widening of the aorta (which can be caused by very high blood pressure and a variety of other less common conditions).
