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Rotary Engine how it works

The Rotary Engine explained, how it works and use in cars.
The chief limitation of modern piston engines is the stress set up in components between piston and crankshaft when they change direction of movement. The stress
increases rapidly as the engine speed rises until a point is reached at which moving parts would disintegrate. For this reason, the distance travelled by reciprocating parts has been kept to a minimum as engine speeds have increased, resulting in the "over square" design of today.

Two successful types of engines have resulted from a complete change of design that eliminates reciprocating motion. The gas turbine, for example, is virtually commonly employed in modern aeroplanes. The other is a rotary member unit, which has a triangle rotor that moves in an oval housing and is powered by a spark plug. During development, the latter kind had a number of issues, including rotor sealing, cooling, noise, and lubrication, but they have now been completely resolved.
Early engines employed the two-stroke cycle, but in common with piston counterparts suffered from poor breathing as engine speed increased; this in turn resulted in poor thermal efficiency and short component life. The successful unit which is now used in current production road vehicles, has, for this reason adopted the four-stroke cycle. When the power desired is fairly high, more than one rotor is used in the same way as cylinders are multiplied with piston engines. No valves are incorporated.
Maximum power output was initially produced at a rotor speed considerably higher than a normal piston engine but lower than a gas turbine.
In service, the stresses produced on rotor seals and casing led to a comparatively short engine life coupled with starting difficulties.
Alterations in design have subsequently reduced the operating speed to that of normal piston engines. To improve the combustion efficiency, two spark plugs are sometimes fitted. These are arranged to spark separately, one slightly after the other to lessen the distance of flame Advantages over piston engines include smoother power delivery and more compact construction coupled with a much-improved power to weight ratio, especially in the larger engines.

How the Rotary Engine works.

Intake is starting between 1 and 3 Compression is occurring between 1 and 2
Power is being produced between 2 and 3 Exhaust is finishing between 3 and 1

Intake is finishing between 1 and 3 Spark is occurring between 1 and 2. Exhaust is occurring between 2 and 3.

Intake continues between 1 and 3 Compression continues between 1 and 2 Power is finishing between 2 and 3

Intake is finished between 1 and 3 Power is being produced between 1 and 2 Exhaust is continuing between 2 and 3

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Four-stroke engine explained

How a four stroke engine works. There are two basic types of engines in common use today, namely two stroke and four stroke. These take their names from the number of piston strokes necessary to complete the cycle between the introduction of the fuel and its exhaust to atmosphere. The four-stroke cycle demands more mechanical components in the engine but gives a higher thermal efficiency. It is therefore the more commonly used, except for some small motor-cycle, scooter, lawn mower and motorboat engines and at the other end of the scale, in some large diesels.

THE FOUR STROKE CYCLE

 1 -Induction, 2 - Compression, 3 - Power, 4 - Exhaust.

In the four stroke or "OTTO" cycle — so called after the inventor - there is only one power stroke per cycle. The remaining three are referred to as idle strokes although they each form an indispensable part of the cycle. The power impulses from each piston in the engine are exerted in turn on the common crankshaft, the flywheel absorbs any variations in power and enables the motion of the connecting rods, pistons and valves to be continuous. The four strokes refer to intake, compression, combustion (power) and exhaust strokes that occur during two crankshaft rotations per power cycle.

The cycle begins at Top Dead Centre (TDC), when the piston is farthest away from the axis of the crankshaft. A stroke refers to the full travel of the piston from Top Dead Centre (TDC) to Bottom Dead Centre (BDC). 

The compression stroke compresses the mixture and places the crank in the best position to receive power. The power stroke exerts a thrust on the piston which, travelling downwards, applies the power to the crankshaft. The exhaust stroke scavenges the burnt gases from the cylinder and returns the piston to T. D. C. ready for the next cycle. It can be seen that there is only one power stroke and consequently one spark per cycle and the intake and exhaust valves open and close once. The crankshaft completes two revolutions every cycle, therefore the valve camshaft and the mechanism which produces the spark, are geared to revolve at half crankshaft speed.
We have mentioned the fact that the exhaust valve does not close until a few degrees after top dead centre and the inlet valve opens a few degrees before. The interval during which both valves are open, known as the angle of overlap, is used to ensure efficient gas charge and adequate scavenging of exhaust. The exhaust gas is expelled from the cylinder at a high speed and thus creates a partial vacuum in the cylinder which encourages the inflow of new mixture. The exhaust valve is closed in time to prevent the new mixture from leaving the cylinder.
Let us consider a single cylinder and assume that the parts which move are already in motion. The four strokes may be described as follows:

Induction Stroke.

At the start of this stroke the exhaust valve is closed, the inlet valve is already open and the piston is at its highest position. While the piston is at this point, known as top dead centre (T. D. C.), only a small space, the combustion chamber, is left between the piston crown and the top of the cylinder. The piston is drawn down by the turning cranks and as the space above the piston increases, the pressure falls, thus creating a partial vacuum. Atmospheric pressure forces air in through the carburettor system, picks up vaporised fuel on the way and passes into the cylinder via the open inlet valve. When the piston reaches bottom dead centre (B. D. C.), the internal gas pressure is
still less than the atmospheric pressure. The inlet valve therefore remains open until the crank has passed through B. D. C., and turned approximately 50 beyond. At this point the inlet valve is arranged to close by the action of a spring.

Compression Stroke 

The pressure of the gas trapped in the cylinder increases as the piston rises. At, or just before T. D. C., the plug sparks and ignites the mixture. Combustion occurs while the crank is turning from the instant of ignition to the most effective thrust angle.

Power Stroke 

The high pressure generated by the combustion of the mixture exerts a thrust on the piston and forces it downwards. The gas is burnt and most of its expansion pressure is exhausted by the time the crank has turned approx. 120 from the point at which thrust was applied. This crank angle is such that further thrust would have no effective turning power. The exhaust valve is therefore arranged to open before the crank reaches B. D. C., enabling the remaining pressure, no longer useable for thrust, to be utilised to drive out the burnt gases from the cylinder.

Exhaust Stroke.

The revolving crank moves the piston on through B. D. C. and then pushes it up the cylinder. The exhaust valve opens some degrees before B. D.C. by a mechanical action. Any remaining pressure is released through the exhaust port and the rest of the burnt gas is pushed out by the rising piston. The exhaust valve is closed by its spring when the crank has just passed T. D. C. once more. The inlet valve opens at approx. 10 before T. D. C. by a similar mechanical arrangement to that opening the exhaust valve and the whole cycle is repeated. 

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Connecting rods

manufacture size comparison Guide

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Engine Firing order

 

The firing order is the sequence of power delivery of each cylinder in a multi-cylinder reciprocating engine.

This is achieved by sparking of the spark plugs in a gasoline engine in the correct order, or by the sequence of fuel injection in a Diesel engine. When designing an engine, choosing an appropriate firing order is critical to minimizing vibration, to improve engine balance and achieving smooth running, for long engine fatigue life and user comfort, and heavily influences crankshaft design.

Ignition

In a gasoline engine, the correct firing order is obtained by the correct placement of the spark plug wires on the distributor. In a modern engine with an engine management system and direct ignition, the Engine Control Unit (ECU) takes care of the correct firing sequence. Especially on cars with distributors, the firing order is usually cast on the engine somewhere, most often on the cylinder head, the intake manifold or the valve cover(s).

Cylinder numbering and firing order

Notes on left/right and front/rear

When referring to cars, the left-hand side of the car is the side that corresponds with the driver's left, as seen from the driver's seat. It can also be thought of as the side that would be on the left if one was standing directly behind the car looking at it.

When referring to engines, the front of the engine is the part where the pulleys for the accessories (such as the alternator and water pump) are, and the rear of the engine is where the flywheel is, through which the engine connects to the transmission. The front of the engine may point towards the front, side or rear of the car.

In most rear-wheel drive cars, the engine is longitudinally mounted and the front of the engine also points to the front of the car. In front-wheel drive cars with a transverse engine, the front of the engine usually points towards the right-hand side of the car. One notable exception is Honda, where many models have the front of the engine at the left-hand side of the car.

In front-wheel-drive cars with longitudinally mounted engines, most often the front of the engine will point towards the front of the car, but some manufacturers (Saab, Citroën, Renault) have at times placed the engine 'backwards', with #1 towards the firewall. One notable car with this layout is the Citroën Traction Avant. This layout is uncommon today.

Cylinder numbering and firing orders for various engine layouts

In a straight engine the spark plugs (and cylinders) are numbered, starting with #1, usually from the front of the engine to the rear.

In a radial engine the cylinders are numbered around the circle, with the #1 cylinder at the top. There are always an odd number of cylinders in each bank, as this allows for a constant alternate cylinder firing order: for example, with a single bank of 7 cylinders, the order would be 1-3-5-7-2-4-6. Moreover, unless there is an odd number of cylinders, the ring cam around the nose of the engine would be unable to provide the inlet valve open - exhaust valve open sequence required by the four-stroke cycle.

In a V engine, cylinder numbering varies among manufacturers. Generally speaking, the most forward cylinder is numbered 1, but some manufacturers will then continue numbering along that bank first (so that side of the engine would be 1-2-3-4, and the opposite bank would be 5-6-7-8) while others will number the cylinders from front to back along the crankshaft, so one bank would be 1-3-5-7 and the other bank would be 2-4-6-8. (In this example, a V8 is assumed). To further complicate matters, manufacturers may not have used the same system for all of their engines. It is important to check the numbering system used before comparing firing orders, because the order will vary significantly with crankshaft design (see crossplane).

As an example, the Chevrolet Small-Block engine has cylinders 1-3-5-7 on the left hand side of the car, and 2-4-6-8 on the other side, and uses a firing order of 1-8-4-3-6-5-7-2. Note that the order alternates irregularly between the left and right banks; this is what causes the 'burbling' sound of this type of engine.

In most Audi and Ford V8 engines cylinders 1-2-3-4 are on the right hand side of the car, with 5-6-7-8 are on the left.

This means that GM LS V8 engines and Ford Modular V8s have an identical firing pattern despite having a different firing order.

An exception is the Ford Flathead V8 where the number 1 cylinder is on the right front of the engine (same as other Ford V8's) but this cylinder is not the front cylinder of the engine. In this case number 5 is the front cylinder. A similar situation exists with the Pontiac V8's 455 etc. where the cylinders are numbered like a Chevrolet V8 but the right side bank is in front(like a Ford), this puts cylinder number 2 in front of number 1.

Odd and Even Firing Order

Firing order affects the balance, noise, vibration, smoothness, and sound of the engine.

Engines that are even-firing will sound more smooth and steady, while engines that are odd, or uneven firing will have a burble or a throaty, growling sound in the engine note, and, depending on the crankshaft design, will often have more vibrations due to the change of power delivery (with the exception of the Crossplane crankshaft, which has an uneven firing order, found in most V8s . Most racing engines such as those in Formula One often have an even firing order, mostly for quicker acceleration, less vibrations, and more efficient exhaust system designs. Most engines that utilize the Big-bang firing order system will often have an uneven firing order.

Examples of odd-firing engines are any crossplane V8 (such as the GM LS engine), All Ford V10 engines, Audi V10 FSI, GM Vortec 3500 Inline 5, Viper V10, Mercedes-AMG V12s, Aston Martin 6.0L V12, Buick 231 Odd-Fire V6, and Chevrolet straight-6 engines.

Examples of even-firing engines are most current production inline 4s, most current production V6s, all Ferrari production engines, Lotus Esprit V8, Porsche 918 Spyder, McLaren M838T engine, Toyota LR engine, and all Lamborghini production engines (with the exception of stroked Audi FSI V10 engines).

Various firing orders for different engine layouts

number of cylinders	firing order	example
3	1-2-3 1-3-2	Saab two-stroke, Perodua Kancil engine BMW K75 engine, Subaru Justy engine
4	1-3-4-2 1-2-4-3 1-3-2-4 1-4-3-2 1-2-3-4	Most straight-4s, Ford Taunus V4 engine Some British Ford and Riley engines, Ford Kent engine, Riley Nine Subaru 4-cylinder engines, Yamaha R1 crossplane Volkswagen air-cooled engine Proton Wira VDO engine
5	1-2-4-5-3	Straight-five engine, Volvo 850, Audi 100
6	1-5-3-6-2-4 1-4-3-6-2-5 1-6-5-4-3-2 1-2-3-4-5-6 1-4-2-5-3-6 1-4-5-2-3-6 1-6-3-2-5-4 1-6-2-4-3-5 1-6-2-5-3-4	Straight-6, Volkswagen VR6 engine, Opel Omega A Mercedes-Benz M272 engine, Volkswagen V6's (both engines are 90-degree V6's) GM 3800 engine General Motors 60° V6 engine Mercedes-Benz M104 engine, Ford Cologne V6 engine Chevrolet Corvair Subaru Alcyone/XT-6/Vortex ER-27 Flat-6 Porsche Boxster Flat-6 Maserati Quattroporte IV V6-4AC-24
7	1-3-5-7-2-4-6	7-cylinder single row radial engine
8	1-8-4-3-6-5-7-2 1-8-7-2-6-5-4-3 1-3-7-2-6-5-4-8 1-5-4-8-7-2-6-3 1-6-2-5-8-3-7-4 1-8-7-3-6-5-4-2 1-5-4-2-6-3-7-8 1-5-6-3-4-2-7-8 1-5-3-7-4-8-2-6 1-2-7-8-4-5-6-3 1-2-7-3-4-5-6-8	1988 Chrysler Fifth Avenue, Chevrolet Small-Block engine GM LS engine, Toyota UZ engine Porsche 928, Ford Modular engine, 5.0 HO BMW S65 Straight-8 Nissan VK engine Ford Windsor engine Cadillac V8 engine 368, 425, 472, 500 only Ferrari V8's, (all are flat-plane crank) Holden V8 Cadillac Northstar Engine
10	1-10-9-4-3-6-5-8-7-2 1-6-5-10-2-7-3-8-4-9 1-8-7-6-5-4-3-10-9-2	Dodge Viper V10 BMW S85, Ford V10 Izusu v10
12	1-7-5-11-3-9-6-12-2-8-4-10 1-7-4-10-2-8-6-12-3-9-5-11 1-4-9-8-5-2-11-10-3-6-7-12 1-12-5-8-3-10-6-7-2-11-4-9	2001 Ferrari 456M GT V12 1997 Lamborghini Diablo VT 3412E Audi VW Bentley Spyker W12 engine
14	1L-1R-2L-2R-4L-4R-6L-6R-7L-7R-5L-5R-3L-3R	(Wärtsilä)-Sulzer 14ZV40/48 V14 marine diesel
16	1-12-8-11-7-14-5-16-4-15-3-10-6-9-2-13	2003 Cadillac V16 engine

 

Although the vast majority of automobile engines rotate clockwise as viewed from the front, some engines are designed by the manufacturer to rotate counter-clockwise to accommodate certain mechanical configurations. In these applications, the firing order is shown in a reverse order (though it still starts with 1). For the most common inline configurations, this gives firing orders of 1-3-2, 1-2-4-3, and 1-4-2-6-3-5. In addition to the reconfiguration of the plug wires or injector tubes, the valve timing must be accordingly modified.