Engine Muffler

Why do Engines make noise?

You would have seen lots of vehicles on road that make different noises. An engine makes a lot of pulsating noise as the exhaust gas escapes the exhaust valves at a very high pressure. These sounds bounce around the inner walls of the tail pipe and can create a loud and annoying noise. A muffler is used to minimize the sound and also tune the sound before the exhaust exits the tail pipe.

Where is a Muffler installed?

Mufflers are installed usually at the end of tail pipe. You can actually spot it as a big box and it does not treat the pollutants in the exhaust gases. It acts as an acoustic soundproofing device designed to reduce the loudness of the engine noise.

How does a Muffler work?

Mufflers are lined with baffles. As the exhaust enters the muffler, the sound waves bounce off these baffles, thereby creating opposing sound waves that cancel each other out. The baffles and chambers can also be tuned to get the desired sonic effect. We can either cut the sound as much as possible or focus on the desired sound with amplified growl range.

Can a Muffler affect engine performance?

Yes, a muffler can affect engine performance. The engine requires fresh charge as soon as the exhaust escapes the exhaust valves. The faster we can get rid of the exhaust from the exhaust pipe, the faster we can supply fresh charge to the engine and can improve its performance. Installation of muffler shouldn’t affect the flow rate of the exhaust from the system.

Kinetic Energy Recovery System (KERS)

Kinetic Energy Recovery System (KERS) is commonly used in Formula 1 cars as a device for recovering kinetic energy in the form of electrical energy when brakes are applied. In addition to the 1.6 liter V6 engine which can produce 600 hp, KERS can provide an additional 160 hp which can boost the speed of the car to overtake or to increase the lead from the other cars.

Why is KERS required?

The introduction of the new KERS system has significantly reduced the size of the Formula 1 engines from 2.4 liter V8 to 1.6 liter V6. This has resulted in higher efficiency and reduced the fuel consumption by approximately 35%.

FIA allowed the use of KERS in Formula 1 cars for the first time in 2009. At that time, the system could only produce 80 bhp and was also not mandatory for the teams to install in their cars due to space and weight constriction.

However in 2014, all companies agreed to install the new KERS which could generate 160 bhp and also to balance the shift from 2.4 liter V8 to 1.6 liter V6 engine.

Working of KERS:

The KERS introduced in 2009 was used to draw energy from rear axle of the car and could store 400 KJ of energy per lap, which can be reused in the form of boost to add 80 bhp to the wheels. The energy is recovered during braking and is reused as a boost for 6.6 seconds per lap. The recovered energy can be stored electrically, in a battery or a supercapacitor or mechanically, in a flywheel. The energy can be recovered by the driver by using a ‘Boost button’ on the steering wheel.

The new system introduced in 2014 allowed the system to recover energy from all four wheels and also from the exhaust gas. It consists of two separate Motor Generator Units (MGUs). The MGUs in the form of generator generates electricity and it can also function as a motor generating mechanical energy.

MGU-K (where ‘K’ stands for kinetic energy) can convert the kinetic energy generated during braking into electrical energy and store it in the supercapacitor. It also acts as a motor to power the drivetrain by returning approximately 160 hp. This unit can recover a maximum of 2 MJ of energy.

MGU-H (where ‘H’ stands for heat energy) can convert the heat energy from the exhaust into electrical energy. This unit is connected to the turbocharger and also controls the speed of the turbocharger. The energy recovered by this unit is used to power the MGU-K unit and further transmitted to the drivetrain. The maximum amount of energy that can be recovered by both the MGUs is 4 MJ, which is 10 times higher than the 2009 model.

The driver can use an additional boost of 160 hp from KERS for 33 seconds per lap.     

The power unit consists of 6 components:

·         Internal combustion engine

·         Motor Generator Unit (MGU-K)

·         Motor Generator Unit (MGU-H)

·         Energy Store ( Supercapacitor)

·         Turbocharger

·         Control Electronics

The teams are allowed to use only 5 of the 6 power units during the entire championship season. If they use all 6, grid penalty will be imposed on the driver. 

How to Calculate Vehicle Speed

Car transmissions can look complicated, and the actual working can seem to be even more complicated. A conventional constant mesh gear box consists of an input shaft from the engine, a counter shaft and a main shaft which delivers power to the differential via propeller shaft. To know more in detail about the working of a constant mesh gearbox, please visit the page on the following link: 

• How manual transmission works

As you can see in the diagram, a 4-speed constant mesh gearbox consists of a set of 11 gears (including the gears between the input shaft and the counter shaft). Now let’s calculate the gear ratio between the gears and how a gear ratio can affect the final drive given to the wheels? How to calculate the speed of the vehicle?

1^st gear:

Let’s say the gear A (driving) has 10 teeth and gear B (driven) has 35 teeth. Gear ratio is the ratio of number of teeth in the driven gear to the number of teeth in the driving gear.

Gear ratio = number of teeth in the driven gear / number of teeth in the driving gear

Therefore, 1^st gear ratio can be calculated as

G1 = T_B / T_A

G1 = 35/10 = 3.5 : 1

T_B = Number of teeth in gear B

T_A = Number of teeth in gear A

The differential has its own gear ratio which is known as the Differential gear ratio (G_D). In this case, let’s assume that G_D = 3.5. Now the G_D is fixed and cannot be altered.

Now to calculate the speed at which the wheels are rotating, we need to bring into picture the final gear ratio. Final gear ratio decides at what speed the wheels are driven. It is a product of both transmission gear ratio and the differential gear ratio together.

Final Gear Ratio (G_F) = G1 X G_D

G_F = 3.5 X 3.5 = 12.25

Yes, I know it is very complicated and you are lost somewhere in understanding the whole concept. To explain you in simple words, the final value of G_F = 12.25 indicates that for 12.25 revolutions of the engine crankshaft, the wheels will revolute only once.

Consider your engine running at 2000 rpm, then wheels will rotate at (2000/12.25) rpm.

To calculate the speed of the vehicle:

Let’s consider the tire is 0.35 m in diameter, therefore the circumference of the tire is 

C = πD

C = π(0.35)

C = 1.1 m (approx.)

Hence, for every 12.25 revolutions of the crankshaft, the wheels will cover 1.1 m.

Now let’s consider the engine speed in revolution per hour (rph) = 2000 x 60 = 1,20,000 rph.      

Now the vehicle speed can be calculated using the above values. The vehicle speed at 1^st gear at an engine speed of 1,20,000 rph is

Vehicle speed = (Engine speed in rph / final gear ratio) X circumference of the tire

Vehicle Speed = (1,20,000 rph / 12.25) X 1.1 m

= 10,775 meters per hour (approx.)

= 10.775 km/h

The vehicle speed for the other gear ratios can be calculated by following the same procedure as above. Let’s calculate:

2^nd Gear:

Let’s assume the 2^nd gear ratio, G2 = 2.5 : 1.

Differential gear ratio (G_D) = 3.5 : 1

Final gear ratio = 2.5 X 3.5 = 8.75 : 1

Engine speed = 200000 rph          

Vehicle speed at 2^nd gear = (200000/8.75) X 1.1

 = 25142.85 m/h 

= 25 km/h (approx.)

3^rd gear:

Let’s assume the 3^rd gear ratio, G2 = 1.8 : 1.

Differential gear ratio (G_D) = 3.5 : 1

Final gear ratio = 1.8 X 3.5 = 6.3 : 1

Engine speed = 200000 rph          

Vehicle speed at 3^rd gear = (200000/6.3) X 1.1 

= 34920.63 m/h 

= 35 km/h (approx.)

4th Gear:

Let’s assume the 4^th gear ratio, G2 = 1 : 1.

Differential gear ratio (G_D) = 3.5 : 1

Final gear ratio = 1 X 3.5 = 3.5 : 1

Engine speed = 200000 rph          

Vehicle speed at 4^th gear = (200000/3.5) X 1.1 

= 62857.14 m/h 

= 63 km/h (approx.)