Automobile Technology DPI

What's is torque?

Answer :Torque is a twisting force that speaks to the engine's rotational force and measures how much of that twisting force is available when an engine exerts itself.

2-stroke engines
Main article: 2-stroke engine

The defining characteristic of this kind of engine is that each piston completes a cycle every crankshaft revolution. The 4 process of intake, compression, power and exhaust take place in only 2 strokes so that it is not possible to dedicate a stroke exclusively for each of them. Starting at TDC the cycle consist of:

Power: While the piston is descending the combustion gases perform work on it—as in a 4-stroke engine—. The same thermodynamical considerations about the expansion apply.
Scavenging: Around 75° of crankshaft rotation before BDC the exhaust valve or port opens, and blowdown occurs. Shortly thereafter the intake valve or transfer port opens. The incoming charge displaces the remaining combustion gases to the exhaust system and a part of the charge may enter the exhaust system as well. The piston reaches BDC and reverses direction. After the piston has traveled a short distance upwards into the cylinder the exhaust valve or port closes; shortly the intake valve or transfer port closes as well.
Compression: With both intake and exhaust closed the piston continues moving upwards compressing the charge and performing a work on it. As in the case of a 4-stroke engine, ignition starts just before the piston reaches TDC and the same consideration on the thermodynamics of the compression on the charge.

While a 4-stroke engine uses the piston as a positive displacement pump to accomplish scavenging taking 2 of the 4 strokes, a 2-stroke engine uses the last part of the power stroke and the first part of the compression stroke for combined intake and exhaust. The work required to displace the charge and exhaust gases comes from either the crankcase or a separate blower. For scavenging, expulsion of burned gas and entry of fresh mix, two main approaches are described: 'Loop scavenging', and 'Uniflow scavenging', SAE news published in the 2010s that 'Loop Scavenging' is better under any circumstance than 'Uniflow Scavenging'.[citation needed]
Crankcase scavenged
Diagram of a crankcase scavenged 2-stroke engine in operation

Some SI engines are crankcase scavenged and do not use poppet valves. Instead the crankcase and the part of the cylinder below the piston is used as a pump. The intake port is connected to the crankcase through a reed valve or a rotary disk valve driven by the engine. For each cylinder a transfer port connects in one end to the crankcase and in the other end to the cylinder wall. The exhaust port is connected directly to the cylinder wall. The transfer and exhaust port are opened and closed by the piston. The reed valve opens when the crankcase pressure is slightly below intake pressure, to let it be filled with a new charge; this happens when the piston is moving upwards. When the piston is moving downwards the pressure in the crankcase increases and the reed valve closes promptly, then the charge in the crankcase is compressed. When the piston is moving upwards, it uncovers the exhaust port and the transfer port and the higher pressure of the charge in the crankcase makes it enter the cylinder through the transfer port, blowing the exhaust gases. Lubrication is accomplished by adding 2-stroke oil to the fuel in small ratios. Petroil refers to the mix of gasoline with the aforesaid oil. This kind of 2-stroke engines has a lower efficiency than comparable 4-strokes engines and release a more polluting exhaust gases for the following conditions:

They use a total-loss lubrication system: all the lubricating oil is eventually burned along with the fuel.
There are conflicting requirements for scavenging: On one side, enough fresh charge needs to be introduced in each cycle to displace almost all the combustion gases but introducing too much of it means that a part of it gets in the exhaust.
They must use the transfer port(s) as a carefully designed and placed nozzle so that a gas current is created in a way that it sweeps the whole cylinder before reaching the exhaust port so as to expel the combustion gases, but minimize the amount of charge exhausted. 4-stroke engines have the benefit of forcibly expelling almost all of the combustion gases because during exhaust the combustion chamber is reduced to its minimum volume. In crankcase scavenged 2-stroke engines, exhaust and intake are performed mostly simultaneously and with the combustion chamber at its maximum volume.

The main advantage of 2-stroke engines of this type is mechanical simplicity and a higher power-to-weight ratio than their 4-stroke counterparts. Despite having twice as many power strokes per cycle, less than twice the power of a comparable 4-stroke engine is attainable in practice.
Blower scavenged
Diagram of uniflow scavenging

Using a separate blower avoids many of the shortcomings of crankcase scavenging, at the expense of increased complexity which means a higher cost and an increase in maintenance requirement. An engine of this type uses ports or valves for intake and valves for exhaust, except opposed piston engines, which may also use ports for exhaust. The blower is usually of the Roots-type but other types have been used too. This design is commonplace in CI engines, and has been occasionally used in SI engines.

CI engines that use a blower typically use uniflow scavenging. In this design the cylinder wall contains several intake ports placed uniformly spaced along the circumference just above the position that the piston crown reaches when at BDC. An exhaust valve or several like that of 4-stroke engines is used. The final part of the intake manifold is an air sleeve which feeds the intake ports. The intake ports are placed at an horizontal angle to the cylinder wall (I.e: they are in plane of the piston crown) to give a swirl to the incoming charge to improve combustion. The largest reciprocating IC are low speed CI engines of this type; they are used for marine propulsion (see marine diesel engine) or electric power generation and achieve the highest thermal efficiencies among internal combustion engines of any kind. Some Diesel-electric locomotive engines operate on the 2-stroke cycle. The most powerful of them have a brake power of around 4.5 MW or 6,000 HP. The EMD SD90MAC class of locomotives use a 2-stroke engine. The comparable class GE AC6000CW whose prime mover has almost the same brake power uses a 4-stroke engine.

An example of this type of engine is the Wärtsilä-Sulzer RTA96-C turbocharged 2-stroke Diesel, used in large container ships. It is the most efficient and powerful internal combustion engine in the world with a thermal efficiency over 50 %.[5][6][7][8] For comparison, the most efficient small four-stroke engines are around 43 % thermally-efficient (SAE 900648);[citation needed] size is an advantage for efficiency due to the increase in the ratio of volume to surface area.

See the external links for a in-cylinder combustion video in a 2-stroke, optically accessible motorcycle engine.

4-stroke engines
Main article: 4-stroke engine
Diagram showing the operation of a 4 stroke SI engine. Labels:
1 ‐ Induction
2 ‐ Compression
3 ‐ Power
4 ‐ Exhaust

The top dead center (TDC) of a piston is the position where it is nearest to the valves; bottom dead center (BDC) is the opposite position where it is furtherest from them. A stroke is the movement of a piston from TDC to BDC or vice versa together with the associated process. While an engine is in operation the crankshaft rotates continuously at a nearly constant speed. In a 4-stroke ICE each piston experiments 2 strokes per crankshaft revolution in the following order. Starting the description at TDC, these are:[3][4]

Intake, induction or suction: The intake valves are open as a result of the cam lobe pressing down on the valve stem. The piston moves downward increasing the volume of the combustion chamber and allowing air to enter in the case of a CI engine or an air fuel mix in the case of SI engines that do not use direct injection. The air or air-fuel mixture is called the charge in any case.
Compression: In this stroke, both valves are closed and the piston moves upward reducing the combustion chamber volume which reaches its minimum when the piston is at TDC. The piston performs work on the charge as it is being compressed; as a result its pressure, temperature and density increase; an approximation to this behavior is provided by the ideal gas law. Just before the piston reaches TDC, ignition begins. In the case of a SI engine, the spark plug receives a high voltage pulse that generates the spark which gives it its name and ignites the charge. In the case of a CI engine the fuel injector quickly injects fuel into the combustion chamber as a spray; the fuel ignites due to the high temperature.
Power or working stroke: The pressure of the combustion gases pushes the piston downward exerting more work than it was made to compress the charge. Complementary to the compression stroke, the combustion gases expand and as a result their temperature, pressure and density decreases. When the piston is near to BDC the exhaust valve opens. The combustion gases expand irreversibly due to the leftover pressure—in excess of back pressure, the gauge pressure on the exhaust port—, this is called the blowdown.
Exhaust: The exhaust valve remains open while the piston moves upward expelling the combustion gases. For naturally aspirated engines a small part of the combustion gases may remain in the cylinder during normal operation because the piston does not close the combustion chamber completely; these gases dissolve in the next charge. At the end of this stroke, the exhaust valve closes, the intake valve opens, and the sequence repeats in the next cycle. The intake valve may open before the exhaust valve closes to allow better scavenging.

Hero Honda CBZ Xtreme Atft Ownership Review
Hi Everyone! This is my first ever review of a bike in a website. As I am a regular reader of BikeAdvice.in, I have decided to publish it here. I thank BikeAdvice million times for all of the valuable reviews and the ownership experiences.

Let me tell all of you that my review would be based on my feeling, observations and it may be biased due to my love that I have for my bike. Here goes my review.
Year 2002: Learnt bike driving on my father’s Honda CD80 and started to become passionate about bikes. Then I started to ride one of my friend’s Splendor. Then I started to beg to my father for a bike.
Year 2004: I got my Bajaj Caliber 115 was really amazed by it for its acceleration because displacement was only 110CC but delivered power like a 125CC bike. It was may be due to its engine producing 9 BHP and had a top speed of 100KMPH.
Year 2006: Sold my bike due to some unavoidable circumstances.
Year 2010: After waiting for almost 4 years finally bought another bike and that is none other than CBZ- Xtreme. Well, I live in Bangladesh & bikes over 150CC are not legally available here. I had the following choices only:

Hero Honda hunk
Hero Honda CBZ-Xtreme
Honda Unicorn
TVS Apache 150/ RTR 160
Yamaha FZ16/FZ-S/Fazer
Yamaha R15
Baja Pulsar 150 UG4.5

After researching for almost 6 months & test riding all of them I selected Hero Honda CBZ Xtreme. Well many of you may ask why didn’t you select other options? Here goes my answer but it’s just my personal opinion and no offends to anyone.

My first choice was Hunk but I didn’t go for it because I felt pronounced vibrations after crossing 6000rpm and it was very hard to take it to 9000rpm. I really like Honda Unicorn because of its super refined mill; its smoothness just blows me away.
But I don’t like its styling. About Apache 150, it was not refined & it produces the least power among all of the above. RTR 160, it has got great power but sporty riding position has never been to my liking because I go for long trips every now and then and the vibration issues.
About the FZ? Well it’s a real fun to ride but because of the mileage factor, pillion comfort and stressed engine after crossing 90kmph I removed it from my list. R15 has always been my favorite but I just can’t afford it.
About Pulsar? Reliability, maintenance is a great factor in case of Bajaj and also never liked the handling, feels too heavy. So finally settled down for CBZ Xtreme & this are the following reasons why…

eid Mubarak to all fb friends..

Guess this custom motorcycle...
a. Suzuki
b. Honda
c. Yamaha

PeoplelovePretty SsangYongcarcamping

Na NOW!! Preparing to drive GT-R In
order to drive competition

working of 4 stok engine....

Volvo V60 diesel plug-in hybrid, can
now be powered by the Sun

Mercedes-Benz Sprinter 2013