This is the 2^nd part of the three article series and in this article I will cover dyno testing of a vehicle. If you missed out 1^st article then just go through that once before you read this one as it covers the basics. Here is the link           https://torqueorpower.blogspot.com/.  

Ok, so let’s move on. You are already clear with torque vs. power curve but how do you get it? A modern m/c which is build specially to test a vehicle is called a dynamometer and testing is often referred to dyno testing. It calculates power with the help of rpm and torque readings. Instantaneous power is calculated later as it cannot be measured directly.

hp(horsepower)= (torque*rpm)/(5252)

Where did this 5252 come from? Why 5252 in particular? Long back when a horse which was the only means of transportation then, was experimented by James Watt(Scotland). He found that it could do 33,000 ft-lbs of work(power produced) in a minute. If you want to know more then just go through the screenshot below or else just stick to the point where I said that I won’t use math.......sorry for that!!

The calculation is already fed into the system. Dynamometer also tests emission, speed, mileage, exhaust noise, brakes, air-fuel ratio etc other than just power.

Dissection!!

A basic dynamometer that is found mostly in service stations, garages is the chassis dynamometer. It is a massive machine situated inside a closed room to keep enormous engine sound within the confines of the hall or room. From a distance it looks like a long elevated platform.

A strong steel chassis forms the foundation of the dyno with a high strength steel sheet that covers the dyno chassis and forms a primary surface on which a bike(even a 4-wheeler) is placed. Whole platform is designed in such a way that it could absorb the forces produced by a running engine and in turn provide a stable base. Ramp is fixed on one end which is used to roll a bike on to the dyno. Two parallel roller drums perpendicular to the axis of the bike are located on the same end. One of the two drums is free to roll and the other one has all the circuits with the electronics attached to it. The second drum is responsible for detecting performance of the bike. To the other end, there is a sliding lock arm which locks the front wheel. It could slide and reposition itself according to the wheel base. The same side is where the engine cooling system basically comprising of a blower fan is present. It could also be adjusted according to a bike dimensions. There are strap hooks on either ends to strap the bike. An adjustable driver display screen is provided which displays detailed performance information. 👇This is what is going on the screen  while a dyno test.

Whole unit is connected to a computer which basically makes necessary adjustments to the engine according to the displayed information. The process is often known as tuning/modifying/upgrading. Of course, an operator must keep emergency kit nearby i.e. fire extinguisher as dyno test sometimes end up in engine blowups or blasts causing flames coming out of it. So many times it has happened that a bike if not locked properly jumps off the dyno after reaching high speed due to the vibrations. It is a highly dangerous m/c and should be touched only after professional training and under expert guidance.

 Dynamometer is used in various fields. You won’t believe but there is a specific dyno which calculates human energy levels. There are only three types of dynos in an automobile world:- 

1) Chassis dyno

This is the most widely used dyno. That is because of the ease of operation in which the operator just drives the car onto the platform, straps it up and starts the test right away. The name is due to its capability that is used to develop a vehicle which involves a wide portion of it without removing engine from the chassis. The idea is very simple, when a car starts to accelerate, the rear wheel starts exerting downforce which often is known as g-force. This downforce is what the m/c measures. The rear drum is a smooth, free spinning rotor and is just to support the wheels. The front drum however has rough surface to provide enough grip to the wheels and does the main job. It is connected and controlled by an external motor usually known as eddy current controller which is located on the side of the dyno platform. The drums could be braked or accelerated to any desired speed. A common shaft runs right from the controller to the other end on which the rotor drum is attached. In between the dyno chassis and eddy current controller is a load assembly. The load assembly has force transducer that measures the force exerted on the front rotor drum by using spring mechanism. To be précised, it measures the amount of transducer that got pressed when the wheel exerted force on the drum. Engine wastes some power in form of heat which results in heated up engine while performing a dyno test. M/c has a smart thermostat cooling system which has either one or two blowers depending on the need, turns itself on as soon as the heat level crosses the pre-set temperature. This keeps a car well in the heat bandwidth. The display screen is generally fixed at a place comfortable enough for the operator which is to the front corner. It is used to test vehicles upto 1000 hp. Usually in a chassis dyno, a driver is required to operate the car. In case of a bike, often a rider is required but sometimes an automatic riding system controlled precisely by a computer is installed. This system is capable of operating a bike just like a human. Well this reminds me of a famous brand slogan “ITS A HUMAN THING”. Anyways, a car while getting tested experiences a close on-road conditions. Automobile giants never compromise with even a mm of error and so Bugatti, Lamborghini and many others construct a special dyno room which has temperature control features. In here, the room could be set to -10 degrees to test the performance of the car in snowfall. The room literally sprays snow just the way natural snowfall occurs. On the other side, the temperature could be raised to 50 degrees with mud spray to test the performance of the same in hot deserted conditions. The operator never forgets to wear ear plugs or headphones to avoid hearing problem under constant high noise testing.

Demo                          

Drive the car using the ramp till the live axle wheels get fixed in between the two rotor drums. Fix the dead axle wheels to lock wheel arms. Strap the car properly which would hold it in place. This is easy and quick to setup. Set the gear to 4^th and start throttling the car. This will exert downforce on the drum rotors which in turn will be shown on the display screen with other calculated details based on the measured values. Simultaneously, the cooling system activates by its own. Whatever adjustments are to be made is done on the main computer system on the basis of displayed information. Why 4^th gear? Well, if you look at the diameter of an engine input shaft gear carefully then you would find it nearly equal to 4^th gear on the transmission output shaft ultimately making the gear ratio 1:1. Also, this gives a much lazy increase in the rpm even when the throttle is pressed hard and helps to display a much detailed curve and reading.

2) Engine dyno

The name itself states that the test is done only on the engine. By engine I mean that whole engine is removed from the vehicle and then tested. M/c is enclosed inside a soundproof cabin to avoid ears from getting harmed. The sound is reduced to a great extend when it is inside the hood because of the insulation present inside and muffler. It works on the same braking principle i.e. water molecule inside the impeller tries to resist rotation of the engine shaft. The m/c has additional cooling supply, air-fuel supply through different hoses that are all connected to engine. A separate ignition system that produces spark inside the cylinders is connected as well. Crankshaft or the engine shaft is connected to the impeller that has water inside. The impeller rotates with the rotation of crankshaft. Water is made to flow inside the impeller. Rotating impeller makes the water molecules to clash against the casing walls and oppose the motion. Clashing acts like a small brake and eventually heat up the water molecules. Braking force or torque load is measured by a force transducer attached to the impeller unit. The whole assembly is wired to a computer located outside the cabin. The force is detected with rpm which help to calculate horsepower and other values. Everything is displayed on the screen for analysis. Heated water is sent back to the water tank while fresh water is circulated to the impeller for the next testing. Exhaust hose ejects waste gases to the chimney which then releases out to the atmosphere. This type of dyno test is a time consuming and effortful one which is why new engines or engines under development are only tested. It might take weeks or in some cases a month. It gives more accurate readings which makes it hot favourite for manufactures producing new engines in manufacturing plant before they get assembled in a vehicle. They check the engine for any leaks, weird noises etc.

Demo                         

Remove engine from the vehicle and clamp it on an engine holding table. Secure the table legs tightly and make sure it does not vibrate under high engine revving. Connect cooling hose, ignition unit, air-fuel hose and exhaust hose to the engine. Connect the impeller shaft to crankshaft. Complete all the necessary cable connections and lock the room. The operator carefully starts the test and by the end he gets all the detail on the screen.

3) Power hub dyno

The most portable type of dyno is a hub dynamometer. It could be carried anywhere due to small size of its components. Hub dyno is a mix of both engine and chassis dyno. For a 2-wheel rear drive car, rear end is jacked which keeps the car at the same height with the front end. Wheels are removed from the car which free up both the wheel hubs. 2-wheel or all-wheel drive cars both could be tested using a hub dyno. It depends on the number of power absorber module. Special steel adaptors are provided for each wheel hub and bolted on them.

The main power absorption module has a shaft with a similar sized steel adaptor at the end. It has small rollers to bring it close and adjust it to the wheel hub height for bolting purpose. Jack helps to align wheel adaptor with dyno adaptor. Module adaptor could be bolted to the wheel hub adaptor securing both adaptors together. There is a separate module for each wheel.  Each power absorption module has a powerful motor or eddy current retarder that requires AC power supply to turn itself on. Necessary harness helps it to connect to the power supply. Retarder is a braking motor which works on electromagnetism and is a similar one which is found in a chassis dyno. The retarder rotors experience magnetism when electricity is induced to the coils as soon as the brakes are applied. Magnetic field is developed such that it tries to stop the retarder due to induced eddy currents which slows down the rotor(magnetic field and eddy current oppose each other due to their opposite movements). When the brakes are released, retarder again starts spinning. This is friction-less braking force that is finally measured by the computer. In this way, rotors convert rotational energy into heat energy. A separate thermostatically controlled cooling blower helps to keep the engine well within safe temperature range. There are several sensors to detect different engine characteristics. A car could be tested for any rpm range and has nearly no limits. A car with well over 7000 hp could be safely tested and modified accordingly and that is why Nascar, dragsters, rally cars and other super performance vehicles are tested using a power hub dyno. This is generally not possible in other types of dynos. Measured torque, rpm and other details are displayed on the display screen located on the front. Whole assembly is harnessed to data fetching computer where the car could be tuned or detuned accordingly. Due to small sized components, serious tuners and technicians carry it to the race events where on spot tuning could be done according to the current climate and other conditions. Computer is sometimes installed with virtual reality road conditions to make the test realistic as if the car is really getting ridden on the road to give out accurate results. The main advantage with the dyno is that there is no traction loss as the drive axle has its wheels removed.

Demo                         

Jack the car and remove the live axle wheels. Bolt both the adaptors to both wheel hubs on the same axle. Connect force absorber module to the wheel hub securing both adaptors. Deploy module feet to give a firm and vibration free base to the system. Connect the cooling unit separately with all the necessary cables. Connect aluminium hoses to the exhaust and place the end at a safe open area due to devastating heat and flames shoot out by cars while testing. Turn the power on and start the test. Detailed information is displayed on the screen while computer on the other hand has all the values accurately recorded. Later on, simply tune the car accordingly. Tune the car then test it on the dyno and the process is repeated until the car cranks out desired performance.

by AutoVogue