BASIC PARTS IN EXHAUST SYSTEM

          Generally, we all have known that how much important the exhaust system is.
        Suppose if u have your favorite bike or car, if u want to increase its performance then we can always go for changes in the exhaust System not go for changes in other factors like compression ratio, engine size etc.that's crazy of thinking about all these things studied in Engineering like compression ratio, engine size. So we have to remember that, what we have known the factors related to increasing the performance are not actually enough. Here you will know, what parts in the exhaust system mainly affects the performance of your partner.As I mentioned above, changing the compression ratio will never work out in real practice.But INFINITI (the luxury vehicle division of Japanese cars manufacturer NISSAN) had invented the variable compression ratio engine which is the first production engine in the world.People are so crazy to build beyond belief!!!

     Line diagram of basic exhaust system 

    turbocharger is present in between the exhaust manifold and the cat.Through the down pipes, the turbo is connected to the cat

From the beginning, I am saying that "better performance".What I mean is  

- More Torque@speed(in Torque vs speed graph).

- More HorsePower@speed (depends on speed and torque).

- More MPG(Miles per Gallon) / better fuel economy.

PARTS IN THE EXHAUST SYSTEM:

1.Exhaust manifold/Header

2.Turbocharger(next to the header)

3.Downpipes(connects turbo and cat)

4.catalytic converters(with oxygen sensors if needed)

5.Cat deletes or test pipes(uses when cat is not used)

6.Mid pipes or intermediate pipes

7.Resonator

8.Muffler

9.Tail pipe

Let's know about the purpose of some main parts in a simple way. 

1.EXHAUST MANIFOLD:      

It is the first part of the exhaust system. It collects the exhaust gases from multiple cylinders into one pipe.Usually made up of Simple cast iron (or) stainless steel.

Advantages: low cost

Disadvantages: heavyweight, won't give better performance

In the above image top, one is generally called as header(aftermarket manifold), bottom one as a stock manifold. Since stock manifolds are usually won't give better performance, so go for headers leads to getting better performance.

2)TURBOCHARGER/SUPERCHARGER:

                 These are actually present after the exhaust manifold or header.The purpose of both the devices is same.They are for force the intake air into the cylinder making the system as forced induction. They both compresses the intake air and send it into the cylinder with the pressure more than the atmospheric.As their purpose is same but their design and principle of operation is different.

TURBOCHARGER :

1.Uses exhaust gas to run the turbine.The turbine rotates the compressor results in breathing of compressed intake air.

2.Turbo lag is present due to inertia force of turbine initially.

3.Occupies less space.

SUPERCHARGER:

1.Uses engine power to rotate.

2.No lag is here.

3.Highly responsive.

4.Cost is high.

5.Occupies more space.

Examples: Roots blower, centrifugal compressor, Lysholm twin-screw, Scroll-type supercharger, sliding vane type.

NOTE: Supercharger is basically not a part in the exhaust system.Since it's purpose is same as like a turbocharger, I mentioned here.Actually it comes under the part of intake system while turbo belongs to both the systems like intake and exhaust systems.

3.OXYGEN SENSORS: 

        These are the two important sensors, the name itself indicates that they work based on the percentage of oxygen.These will detect the percentage of oxygen in exhaust gases by comparing with atmospheric oxygen. These are placed on either side of CAT(catalytic converter).

1ST OXYGEN SENSOR (BEFORE CAT):

It will find the amount of oxygen left in exhaust gases. If more oxygen(lean mixture) is there then it will send a signal to ECU( Electronic Control Unit) by saying that there is more oxygen left means less fuel is injecting. Then immediately ECU sends signals to the required components here fuel injector to open for more time so that more fuel will inject.If less oxygen(rich mixture) is there then it will send a signal to ECU by saying that there is less oxygen means more fuel is injecting.Then by the help of ECU fuel injection time will be less.The whole aim of the 1st oxygen sensor is to produce a stoichiometric mixture in order to happen complete combustion so that engine efficiency increases.

2ND OXYGEN SENSOR(AFTER CAT):

This is mainly used to check the efficiency of CAT means to know how well the CAT is working. If the amount of oxygen is less (more amount of toxic gases still present) that means the proper conversion of toxic gases is not happening. so we will find that there is a need to replace the CAT ... Sometimes due to lack of oxygen present in catalytic converter after conversion of NOx gases to Nitrogen and oxygen, the possibility of converting other toxic gases like CO, hydrocarbons is less, so in that case, this sensor will help to send more oxygen through air pumps by sending signals to ECU.

4.CATALYTIC CONVERTER: 

           Used to eliminate toxic gases such as HC(Hydro Carbons); NOx gases (NO, NO2), CO(Carbon Monoxide).

Basic chemical reactions occur in the catalytic converter.

1.Reduction Reaction: 2NOx = N2 + XO2

2.Oxidation Reactions:

#2CO + O2 =2CO2

#CxH(2x+2)+{(3x+1)÷2}O2=XCO2+(X+1)H2O

 Types:

- 2 way: only oxidation reactions take place.

-3 way: both oxidation and reduction reactions take place.

             

       "  INSIDE CATALYTIC CONVERTER "

TWO BLOCKS ARE THERE, FIRST ONE IS COATED WITH PLATINUM AND RHODIUM, SECOND ONE IS COATED WITH PLATINUM AND PALLADIUM. IN FIRST BLOCK REDUCTION TAKES WHEREAS IN SECOND BLOCK OXIDATION TAKES PLACE. THE MIDDLE PIPE IS TO SEND EXCESS OXYGEN (By Using Air-Pump) FROM ATMOSPHERE FOR FURTHER OXIDATION IN THE SECOND BLOCK.

5.MID PIPES/INTERMEDIATE PIPES:

                        In V6, V8, V12 engines the exhaust gases are exiting individually through 3,4,6 cylinders on either side of the engine.Due to fact that these cylinders are all firing at different points in time, there is an inequality in the pulsating exhaust gases coming from the engine. So a MIDPIPE is used to equalizes the exhaust pulses before they travel through the rest of exhaust system.

 TYPES:     Y PIPE, H PIPE, and X PIPE

1.Y PIPE(STOCK MIDPIPE):
            Exhaust gases coming from either manifold are joined together into one pipe that is followed by a muffler and exits out.
     Doesn't help for scavenging usually.It won't give better results when compared to H, X pipes but remember, that doesn't mean it won't suits your vehicle.Depends on the engine you are using, compression ratio like so many factors we have to consider.For example for small engines go for either Y, H is better than X.

                

2.H PIPE(AFTERMARKET MIDPIPE):         It equalizes the exhaust pulses but doesn't improve scavenging effect very much. Because it doesn't exactly draw all the gases and force the pulses don't work off one another, in the end, to really improve exhaust flow.

3)X PIPE(AFTERMARKET MIDPIPE ): 

              It equalizes exhaust pulses and also improves scavenging.

• For less than 4 cylinder engines, single straight(stock) or curved(performance) midpipe is used.

6. RESONATOR: 

           It is to decrease the frequency of sound waves when traveling at low constant speed.For eliminating certain frequency ranges of sound waves which are creating irritating buzz.It has less baffling.

- Almost straight pipe sound level

-Cancel certain frequencies to stop droning and obnoxious noise 

- Not adjustable at all, you either like it or don't

-Decreases engine Back Pressure, Improves performance.

7.MUFFLER: 

       A device used to decrease the amount of noise emitted by the exhaust of an IC engine. Generally, most of these are for eliminating high-frequency waves coming from the engine exhaust gases.But some mufflers like CORSA'S RSC MUFFLER can be used to cancel both low and high-frequency sound waves.So basically this muffler will act as both resonators as well as the muffler.You will see various types in future. 

- Lowers sound level

- Usually packed with fiberglass

-Does not eliminate certain frequencies of sound (droning) except CORSA RSC etc

-Increases engine Back Pressure, hampering performance

8. TAILPIPE: 

                 Used to allow the flow of Exhaust gases smoothly with high velocity.

"MUFFLER WITH TAIL PIPE"

EXHAUST SYSTEM WITHOUT HEADER AND TURBO:

EXHAUST SYSTEM WITH TWO CATS, X PIPE, TWO RESONATORS, TWO MUFFLERS WITH TWO TAIL PIPES.( CAT BACK EXHAUST )