This article is the 3^rd of the three article series on how engine modification is done right from its initial stage to where a car/bike is converted into a high performance demon. To refer 1^st and 2^nd article, just go to the link https://thedynamometer.blogspot.com/2020/08/this-is-2-nd-part-of-three-article.html. Everyone likes to play video games when small and some even play even after getting older. Specially racing games which have been offering high detailed game visual graphics. The hierarchy is what everyone enjoys which is to initially start with a low powered car and complete the game with a high performance car. Of course, most credit is shared by the player having skills to win the game. You might be wondering why this blog mentions computer games and not about mods. Everything is connected and besides that what is the fun if a movie begins without an intro!! Just kidding, the reason behind mentioning racing games is that firstly you cannot deny the fact that in the game, sneaking inside the garage was fun where it had various options to install better parts. The quality improved with the increase in price tags. After moments of scrolling, it showed that there were heck of branded parts which could be installed in your car/bike to improve its performance and help you win the next race. You might have observed that how the performance meter improved after each modification and most of you might had no idea what the parts actually did but just wanted to fill up the performance meter as early as possible to make your car unbeatable. Also, I am sure about you coming across mod options like stage 1 modification, stage 2, stage 3, stage 4 and so on depending on the game. What are all these in real and what are the processes going behind the scene? I will help you understand all about these things. Earlier the car was driven mechanically i.e. everything worked independently with levers and arms connecting them together. Modern cars still have these parts but now sensed and controlled by a brain. ECU forms the brain and sensors help it to command; now making the whole process accurate, quick and self reliable. The car/bike is dyno tested which gives a particular performance output in form of graphs on sheets. A technician notes down all the faults carefully after the graphs are thoroughly studied. Air-fuel ratio is regulated, sensors are replaced and other normal service is done if customer is facing any trouble. This is called engine tuning. Since 1996, almost all cars are installed with onboard diagnostic system (OBD) with the increase in the use of sensors. Just plug in the OBD unit to the computer. This gives a direct access to reads all the sensors and finds the fault rather than the long old procedure of removing and checking the parts one by one and repeat the process on other parts if the fault still persists. It has a reader which is connected to the laptop and helps to control the system. Connect the reader output to the port which is often under the dashboard or under the hood depending on the model.

Start the engine scan just like you scan your laptop using an anti-virus system. Summary of scanning is displayed. Basically, an OBD system is scanning all the sensors in that particular car during a scan. So now a technician could understand the car much better with data available in hand. There are more than 10 sensors in a commuter car/bike out of which some basic ones are:-

🚦Air-flow sensor

🚦Engine rpm sensor

🚦Oxygen sensor

🚦Spark knock sensor

🚦Coolant sensor

🚦Load sensor

🚦Fuel temperature sensor

🚦Voltage sensor

🚦Camshaft position sensor

🚦Throttle position sensor

🚦Speed sensor and so on.....

Sensor?

In general, it is a device that detects any change in physical properties, records it and responds accordingly. Car has different sensors to control different areas of a car just the way we have 5 types of sense organs that help us understand and make our lives easy. ECU(engine control unit) or ECM(engine control module) which are basically the same, becomes the brain of these sensors. Sensors sends signal in form of electric current. ECU reads the signal and signals the sensor to respond. The process is very quick and takes less than a second to activate. Overall, it could be concluded that a car with electronics has its own brain.

But this is only diagnosing the car and till now the car when rolls out of the garage is the same when it was rolled in. To increase torque, power and other vitals, engine goes through modification. Improving an engine’s capability to enhance its performance is called modification or tuning.

 

Stage I tuning

This is the lowest level of tuning where a bike undergoes some basic upgrades that makes it better than the stock version. Stage I tuning is often preferred as a low cost modification. Being the lowest also forms the inception for other higher stage modifications. Rider who wants to enhance the bike in terms of performance, looks and sound could go for stage 1 mod. The sound of a bike totally depends on the number and arrangement of cylinders, type of air filter and most important one....the exhaust pipes. But stage 1 is the most simple way to tune up a bike and it undergoes:-

🚲Air filter change

🚲Exhaust system replacement

🚲Engine remapping

Atmospheric air is a homogeneous mixture of several particulates which makes it unsuitable for the engine. Air is sent into the cylinder where it is compressed and converted into power which we could feel at the moment we twist the throttle. Air filter is used to purify air and is a part that prevents dust, bacteria and other foreign particles to a greater extend from entering into the cylinder. A stock air filter is generally small in size that allows sufficient but comparatively less air into the cylinder which limits engine performance to a certain range. Aftermarket performance air filter is bigger in size that allows greater volume of air into the cylinder. A performance air filter has more oiled cotton filter area which is also called open area than the stock one. More air means more power output. There are different shapes and sizes of air filter in the market. Rider just has to make the selection according to the type of bike and level of performance he wants. Same story follows when it comes to stock exhaust pipes which are designed to minimize the sound which result in loss of power due to the arrangement of baffle. Inside the exhaust pipe, air is made to cover long path and in a zigzag pattern to diminish the output sound. The next part to be replaced is of course the exhaust pipes from header till muffler. After market/performance exhaust has better sound and exhaust gas flow characteristic that provides much straighter or uninterrupted passage.

Different exhaust shapes could manipulate the flow even further. Rider could select the exhaust system that suits the type of bike he rides. Now the exhaust along with air filter has increased the sound and made the bike a heavy sounding m/c. After the installation, the bike is rolled on to the dynamometer. Dyno test not only shows the parameter increment but also helps to tune up the bike. A modern bike has sensors and ECU as mentioned earlier. But these are configured with the stock parts and even after the bike got replaced its stock parts with the aftermarket market ones, ECU is still unaware of this replacement and works in the original manner. Engine remapping/retuning is done in order to configure ECU with the new characteristics. Basically, air-fuel ratio setting is changed to allow more air to mix with fuel and enter the cylinders in the end. The bike with remapped engine is then tested for the final time to record new performance figures. The main motive is to make the engine breathe better and not dirty the hands much. Stage 1 tuning increases overall torque and power up to 15 percent. Of course, this is on the cost of fuel economy where it suffers a pocket decrease. The difference between overall performance of the car that rolled in and the same when rolls out is indicated by the meter below.   

Stage II tuning

The next level of modification is stage II which is higher in cost and requires precise input of what the rider actually seeks from his bike. Stage II focuses purely on engine hardware modification to give a better dose of torque and power output. Mileage and power cannot go side by side. One of the two would suffer a decline if the other is increased or vice-versa. The engine undergoes:-

🚲Camshaft change

🚲Adjustable pushrod installation

The above photo is just a sample of a camshaft and not the actual one that is used in the bike. Camshaft comprises of small egg shaped profile cams that control valve lift. How long, how high are some characteristics which these cams describe. Short profile stock camshaft is replaced with a long profile one. Cams with long profile permit valves to stay open for longer duration of time. Also, it would lift to a much greater height and together both of these parameters allow more mixture to enter into the cylinder. More mixture allows the cylinder to burn more volume and ultimately produces more power. The motive of this stage is to increase compressive ability of the engine. This increases the engine redline which means now the bike could be revved beyond the previous limit giving a much better top speed. There is an increase in peak torque and peak power so now the bike could reach a much higher top speed than the previous top speed with a much greater overtaking capability. Stage II affects mid range power and torque so now peak values is achieved in 4000-6800 rpm range. This mid range rpm helps in easy cruising and overtaking with just a little twist in throttle. Rider who plans to go for stage II mod already is aware about a greater fall in fuel economy compared to stage I mod. A new pro-mapping kit is installed and synced with the upgraded parts to reach higher level for higher performance. This on board pro mapping kit also adjusts its setting according to the road conditions. The bike experiences a performance increase of 30 percent with stage II tuning. A sample graph would give you an idea about the increase in the peak output values. 

Stage III tuning

A much higher stage tuning is the stage III where the engine hardware goes through some serious replacements. From here, tuning is taken to a serious level and is recommended only for professional and sensible riders. Cost of tuning/modifying increase rapidly from here as this stage and the following one involves total dismantling of the engine and assembling along with repeated dyno testing. This is done in order to make the engine reach its limit and also for add precision and accuracy. The engine cranks out even more horsepower and torque after undergoing stage III tuning. The stage focuses more on mid range performance which is basically acceleration. A huge amount of time is demanded in this stage mod as it undergoes parts replacement. Stage II engine is replaced with a cylinder with a bigger bore diameter or the same cylinder is rebored to allow more air-fuel mixture to enter inside.

Reboring an engine means to increase the diameter of the cylinder. Bigger cylinder requires bigger sized piston for balanced functioning. Regular cast aluminium alloy pistons are replaced by a much higher strength, low weight titanium pistons which work better at high speeds and temperatures.

The shape of new piston is such that it increases squish effect for better mixing of the air-fuel mixture with increased flame front. Titanium plays an important role due to its suitable properties and that’s why connecting rods made of titanium are assembled instead of the conventional aluminium ones.

 Valve springs with more coil gap help to open the valves to a greater height.

Other small components like clutch, bearings, gaskets etc go through some changes or replacements to fit and work properly with the new assembled parts. These significant changes are followed by engine remapping to let the engine know that it has gone through a serious modification. Remapping the ECU allows the engine to work suitably and crank out even better torque and power output. How these changes affect the engine is actually shown by a true test called dyno test. The sudden jump in the graph curves is the increase that is observed in the test after the engine is configured to stage III which is about 40 percent and is really high making the bike a fast going m/c. If economy is your aim then refrain yourself to stage II because the fuel economy bar below would show you the fall in mileage. Stage III as well IV are both on the costlier side of modification as the parts along with ECU are not cheap and replacing them could easily empty ones pocket.

                      

Stage IV tuning

It occupies the highest spot of the tuning hierarchy. The last edge of the performance(horsepower) that a particular engine could crank is achieved in this stage. Going beyond this would ultimately blowup the engine that is why this is maximum anyone could modify an engine to. If you need even more then switch the whole engine to a more powerful one or buy a better m/c. Stage III engine undergoes:-

🚲Engine head replacement

🚲Installing bigger fuel injection unit

🚲Inlet manifold replacement

New engine head is installed with improved inlet ports that increase squish and flame front and also velocity of air flowing in for faster and better combustion. Stock stainless steel valves would start an adverse floating and wear out ultimately. These valves can not operate at such high temperatures and speeds which is why titanium valves are installed in this stage.

 

With light weight and high speed operation, it could work precisely and perfectly with the high revving rpm as revving is controlled by valves. Fuel injection unit that is connected to the engine head is replaced with a bigger diameter inlet manifolds one to increase the volume and velocity of fuel flow. The new installed throttle body controls flow of the mixture which is designed in such a way that the mixture not only allows increased flow but also velocity. This ultimately increases the relining limit of the engine and the engine could enjoy more power at high rpms. Stage IV tuning has all earlier stages involved in it so you could now enjoy acute performance rise overall the whole range of rpm. When the bike rolls out of the garage, it has 50 percent increase in horsepower which is a huge hike in the performance. Now the bike is tuned upto its full potential which is indicated below by the performance meter. The m/c is meaner, furious, challenging and aggressive and could be easily felt just by twisting the throttle in neutral gear. Now the engine reaches a much higher rpm with a little throttle twist which is what in technical term is called throttle response.

After stage IV tuning, the m/c with the stock look would surprise others if challenged. Now, you could observe how two same bike give two different performance output with one having stock and other having stage IV tuned engine and not to mention which one starts off the line first and finishes first as well. If I have missed anything in the stage modification then do let me know in the comment section below. Thank you for stopping by and making my efforts valuable.  

         by AutoVogue

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