Knowledge on Exhaust Manifold For A Wiser Purchase

The exhaust manifold is present in automotive engines. It accumulates the exhaust gases from the multiple cylinders into one pipe.  

Made from either stainless steel or cast-iron materials, the gas is transmitted to the exhaust pipe. The headers from each cylinder  

converge in the collector tube or zoomie headers.

The headers are either made of mild steel or stainless steel. They are coated with ceramic finish, heat resistant paint or are chrome plated. 

What is the function of the exhaust manifold?

Exhaust manifolds decrease low resistance and increase the engine's volumetric efficiency.  

Helps the engine to gain its power output. 

The process is governed by gas laws.  

How does savaging work?

• When the exhaust stroke of the engine starts the piston is pushed up the cylinder bore minimizing the chamber volume. 
• The exhaust valve on opening diverges the high-pressure exhaust gas into the header or the exhaust manifold. 
• A huge pressure difference is created from within the exhaust in the combustion chamber and the atmospheric pressure outside the exhaust system. 
• With a balance and equalization of the pressures both within the combustion chamber and the atmosphere the pressure also lowers the exhaust velocity to a medium.
• The residual exhaust gas settles in the tail component in low pressure and in the earliest stages compares with the favorable atmospheric pressure. 
• However, the sudden change from the high to medium pressure affects the pressure in the combustion chamber lowering it to lesser than the atmospheric pressure level. 
• The lowering of the pressure absorbs and extracts the combustion products from the cylinder and during the span often overlaps with the induced intake charge from the partially open intake and exhaust valve. 
• This process of extraction is called scavenging and its degree is dependent on the shape of the exhaust ports, pipework and the engine speed.
• The exhaust velocity is increased by the exhaust manifold or the header. 
• Each exhaust pulse is timed to appear in close sequence. 
• The low exhaust pulse pressure tail creates a wider pressure difference between the next pulse and the high-pressure head, increasing the velocity of the exhaust pulse. 
• V6 and V8 engines include more than one exhaust bank and follow the same principle of increasing the next exhaust pulse using the low-pressure units of an exhaust pulse. 
• The length and width of the primary tube must be carefully selected as a difference in the size, will affect the performance of the exhaust gas and the scavenging system. 
• If large, the exhaust gas will expand slowly; if small, the resisted flow will make the engine work harder and at a higher speed to expel the exhaust gas out of the chamber. 
• The reduced power will dilute the intake charge it receives. 
• The engines are created to produce more intake gas at a high speed the headers are designed to respond to the speed range.
• Therefore, you should depend on primary tubes that offer sturdy torque power at higher engine speed. 
• For lower speed, narrow tubes are best suited. 
• For resonance tuned headers long primary tubes at low engine speed perform better. 
• Modern exhaust headers come with ceramic coating preventing rust and reducing heat radiation in the engine bay. 
• This decreases the air temperature entering the engine.

Exhaust manifolds in V8 Engines

• In crossplane V8 engines, both the right and the left bank contain 4 cylinders each. 
• The engine pistons fire in the order that they maintain. 
• If there are two consecutive pistons moving in close at a time, then the firing will accumulate greater pressure within the exhaust pipe. 
• With the movement of the two pulses, the exhaust pipe will be the H or the X pipe. 
• The pulse is partially diverted to the H and X pipe lowering the pressure marginally.
• The decreased pressure fluid will travel through the pipe and at the crossing will use the path offering minimum resistance and drop off some of the fluid lowering the pressure in small amounts. 
• Without the H-X pipes, the exhaust flow will be irregular with jerks and reducing the efficiency of the engine. 
• With the double exhaust pulse, depending on the amount and mixture of the pulse, the next exhaust pulse in the bank will not exit the cylinder and due to a lean air-fuel ratio (AFR) detonate or misfire from rich AFR.

When should you replace your exhaust manifold?

• If the engine is noisy that could be a sign of a deteriorating exhaust problem. 
• If the gasket is faulty, it can cause leakage and a hissing or tapping sound especially in a cold start acceleration emerges clearly. 
• The engine performance with slow acceleration or very quick acceleration without the desired acceleration speed is a clear sign. 
• A difference in fuel efficiency as the engine will work harder using more fuel. Replacing the exhaust manifold would be the best decision.
• If there is a leakage from gasket failure, plastic parts, even wiring under the hood can burn from the heat of the exhaust gases. The burning smell released with smoke tells you that your vehicle could be in serious trouble. You should have it checked and replaced.
• Sometimes the exhaust pipe breaks and hangs under the vehicle, if that happens then it should be immediately addressed as not only are you at risk but those driving near you are at equal risk. 
• If you smell gas inside the car when driving, have your exhaust manifold checked. One of the exhaust pipes or tubes may be damaged, releasing the fumes from the gasoline from all vents. 

When purchasing a used exhaust manifold what to check?

• Choose the one which has a thick casting as that will keep the strength of the manifold housing gasket intact regardless of the stress that the parts must endure.
• Inspect the ball and socket joint areas between the head pipe and the manifold. They should be strong and secure. 
• Look for signs of wear and tear, cracks, damage, leaks. 
• Carefully inspect the manifold housing, resonator, and converter joints. 
• Check the exhaust pipe hump covering the real axle. 

Why buy your used exhaust manifold from Big Mouth Direct?

• Big Mouth Direct sells used exhaust manifolds at the cheapest prices.
• All the Exhausts are fully inspected by our highly knowledgeable technical engineers. 
• You will be advised and guided all through your purchase if you require their assistance. 
• Big Mouth Direct is connected with 4000, junkyards and salvage yards and you will receive your exhaust manifold without any delay. 

Visit the website for details, https://bigmouthdirect.com/ or call (844) 205-7332.