A reconditioned engine is a rebuilt engine. A used engine is taken apart, cleaned and reassembled with new bearings, rings, valve guides and other worn parts replaced. It is just as good as a new engine, since anything that could wear out has been replaced.
After that the engine is dismantled for reconditioning.
DETAILS OF ENGINE IS GIVEN BELOW
v Type- 4stroke cycle
v Water Cooled SOHC(1C2V)
v Number Of Cylinders-3
v Piston Displacement -796CC
v Max Output 37bhp at 5000rpm
v Max Torque 59 Nm at 2500 rpm
There are separate sets of pipes attached to the cylinder head which carry the air-fuel mixture and the exhaust gases. These are called manifolds.
I. INTAKE MANIFOLD
The intake manifold is a tube type hollow casting of cast iron or aluminium. As shown in Fig. It consists a inlet port to receive the air and fuel mixture from the carburetor. The carburetor is attached to it by means of studs. The outlet ports of the intake manifold are attached to the intake ports of the engine block or engine head by means of studs and clamps. A good design of the intake manifold consists of a smooth and short path from the carburetor to the cylinders thereby minimizing the chances of condensing and collecting the fuel on the manifold walls.
II. EXHAUST MANIFOLD
The exhaust manifold is similar to the intake manifold but it carries the burned gases away from the engine cylinders. It is also attached to the side of the engine head. The inlet ports of the manifold are clamped to the outlet ports of the exhaust valves by means of studs and clamps. The gaskets are provided between the seats of the engine block and manifold ports to prevent the leakage of the gases. As shown in Fig it consist a outlet port from where the burned gases are passed to the exhaust pipe, muffler and tail pipe and finally to the atmosphere.. The material used for exhaust manifold is cast iron or aluminium alloy.
The exhaust manifold is so designed that it may avoid the possibility of overlapping of exhaust strokes thereby minimizing the back pressure.. Back pressure is also minimized by providing large-radius bends thereby eliminating restrictions and obtaining a streamlining flow of the burned gases through the exhaust manifold.
STEPWISE PROCEDURE OF ENGINE DISMANTLING
1. Drain oil sump.
2. Remove subassemblies like generator, starter motor, oil filter and engine flywheel.
Note: Put mark on flywheel and crank shaft flange as they are dynamically balanced in assembled condition.
3. Remove cylinder head cover, rocker-shaft assembly and push rods.
4. Remove manifolds.
5. Remove high pressure fuel lines.
6. Remove all studs at the cylinder block cylinder head.
7. Keep the engine in upside down position.
8. Remove oil sump.
9. Remove oil strainer and oil pump.
10. Remove connecting rod caps.
11. Remove pistons and connecting rods from topside of cylinder bore (engine in normal position).
DISMANTLING AND ASSEMBLING OF MARUTI 800 PETROL ENGINE CYLINDER HEAD
REMOVAL OF CYLINDER HEAD
All components and parts fitted to the cylinder head as well as valve operating gear were removed carefully by loosening the holding bolts first at the centre and then working outwards. All the external conduction cable to resist the removal of cylinder head also disconnected. The spark plug should also be removed.
REMOVAL OF VALVES
Each valve is marked suitable to refit it to the same valve seat. To remove easily the collects or pins retaining the valves in the springs, a special valves spring depressing tool is used to squeeze the springs.
REMOVAL OF CARBON
Care should be taken not to scratch or damage the parts while removing carbon deposits from the cylinder head, the top of the piston and the valve parts. In order to retain the seal between the piston and the cylinder, leave a ring of carbon around the edge of the piston by placing an old piston ring over each of the piston when it is brought to the top of the cylinder for cleaning. Blow out all the loose carbon deposit with an air jet. Emery paper is used to clean the rust off the head. The valves, valve springs and valve seats may be cleaned using cotton waste and kerosene and checked for good condition.
For checking and inspection of valves, valve springs and valve seats.
The valve face is checked for distortion and burning, for pits, roughness and pocketing. Lapping of the valves to the seat is done to remove very slight pits. To remove deep pits, roughness and pocketing, a valve grinder may be used with care. The thickness of the metal at the edge of the valve is also checked. The condition of the valve stems may be checked for scoring and scratching.
To check the length of the old valve spring, they are compared with new one with the help of a spring tester. Tension of the shorter springs also tested
The faults like roughness, pitting also removed by re cutting the valve seat with a special valve seat cutter.
3. LAPPING THE VALVE
For lapping the valves to the seat, proceed as under:-
Clean the valves and valve seat. Before placing the valves in their original valve guide, a small amount of carborundum may be put. Lap the two together using a slight pressure by means of a screw driver or section placed on the top of the valve. The valve may be moved quarter of a turn in each direction till it turns smoothly. Now lift the valve.
Mark the valve face, continue lapping and testing till all marks disappears. Otherwise stop lapping further. Now all carborundum around the valve seat and the valve may be cleaned.
Before assembly, clean and oil all parts thoroughly. Make sure that the valves are in their original valve guides, while fitting the valve, valve springs and new rubber springs when refitting the collects or pins to the valve and the springs, use a valve spring depressor tool. In case cylinder head gasket is in good condition, fit it before refitting the cylinder head by tightening the nuts. Then refit various parts removed from the cylinder head.
ENGINE VALVE RECONDITIONING
As you take the valve out of the head , inspect each valve. Decide whether or not it can be serviced and used again. IF the valve looks good enough to use again, put it into its proper place in the valve rack. IF the valve looks too bad to be cleaned up for further service, discard it , put a new valve in the appropriate place in the valve rack.
PROCEDURE FOR RECONDITIONING OF VALVES
1) Clean each valves, Remove carbon with a wire wheel. Polish the valve stem, if necessary, with a fine grade of emery cloth. Do not take off more than the dirty coating on the surface. Do not take metal off the stems.
2) As you clean the valves, re examine them to make sure all are usable. Small pits or burns in the valve face can be removed by refinishing the valve. Larger pits or burns require that the valve to be discarded. After grinding the valve margin must be at least 1/32 inch, If the margin is any thinner, the valve will run too hot. Eccentricity or run out can be checked in the valve refacer itself .If the run out or eccentricity is excessive, discard the valve.
3) REFACING VALVES
This requires a valve refacer. The valve refacer has a grinding wheel, a coolant- delivery system, and a chuck which holds the valve for grinding. Set the chunk to grind the valve face at the specified angle. This angle must just match the valve seat angle. Then put the valve into the chuck so that the part of the stem that runs in the valve guide is gripping by the chuck. Then start the machine (both wheel head & work head motors) coolant pump is also started along with these motors. Move the lever to carry the valve face across the grinding wheel. The first cut should be light one. If this cut removes, metal from only one- half or one- third of the face, the valve may not be centered. Or the valve stem is bent and the valve should be discarded. Do not take cuts heavily otherwise the margin will be lost. Sometimes the new valves are refaced slightly provided they are not of the coated type. Never reface coated valves.
Dress the grinding wheel as necessary with the diamond- tapped dressing tool. As the toll is moved across the rotating face of the grinding wheel, the diamond cleans and aligns the grinding face.
SPARK PLUG CLEANING AND TESTING
(1).INTRODUCTION TO SPARK PLUG
It is an important as well as the well as the weakest component of the ignition system after the contact breaker. Its main purposes are to provide a gap across which a high tension spark jumps to ignite the fuel mixture in the combustion chamber of the engine. By screwing the steel body into the combustion chamber of the engine, it is mounted there. It is usually designed to operate under 20,000 to 30,000 volts .It can withstand a high pressure of 42 kg/cm².
(2).CLEANING OF SPARK PLUG
First the cleaner unit assembly should be filled with sand in the following manner. The adopter steel cap and rubber adopters are not to be taken out. After closing the mouth of the rubber nozzle, the sand should be slowly poured inside the cleaner unit assy .Next the unit has to be connected to the compressed air system which is capable of the minimum pressure of 5kg/cm² . Next turn away the protective shield In cleaner unit assembly and fix the dusted spark plug in the rubber adopter(depending upon the plug thread i.e.M10, M14 & M18 the rubber adopter can be chosen) and operate the double action valve knob a-t Abrasive Blast Position for 10 to 15 seconds by rotating the plug so as to clean in all position followed by operating the Double action valve knob to Air Blast Position to remove the sand particles in spark plug for 5 seconds. The specified pressure should be maintained while cleaning the spark plugs and also ensure cleaner unit contains 500 gms of sand.
(3).CHECKING AND IDENTIFICATION OF GOOD SPARK
A hot intense spark igniting the maximum and penetrating a compressed mixture quickly is known as a good spark. A spark existing between two steel ball electrodes has n intense white appearance and a purplish corons(intense heat). The spark should be fat, voluminous as well as thin intense, so as to produce a hot intense spark.
An ignition spark consists of two parts – a snapy centre N ( called the nucleus) indicating intensity and a corona (c ) surrounding nucleus and indicating volume or heat radiating quantities .A spark having snapy nucleus and a co luminous blue N purplish red corona is intense and hot spark.
Heat of ignition of spark is based upon the current value (amperes) and its intensity in the potential value (voltage). The combined effect of both is based upon the battery voltage, the winding of the coil, absence of any type of unnecessary resistance in the primary circuit like loose connection, insufficient tension at the interrupter points, oxidized, interrupter points, uneven surfaces, pitted points etc. as well as the time of interruptions, quick opening of the interrupter points and the lengths of the time the contact points are closed for proper build up of a magnetism.
(4) . SETTING OF SPARK PLUG GAP
The nature and compression of the fuel mixture as well as distance between the electrodes known as gap are the factors which affect the electrical resistance of a spark plug. The manufacturer usually recommends the correct spark plug gap size. It generally varies between 0.6 to 1 mm. For new spark plugs, the gap is usually 0.6 mm which gets increased with the use and requires higher voltage for jumping of the spark across it. The efficiency of the entire ignition system is generally reduced both by very large and very small plug gaps. In turn the losses in engine power and operating efficiency are caused by this. Carbon particles or some other foreign materials like dirt particles deposit on the insulator between the electrodes or on the outside of the insulator between the plug terminal and the shell. They provide alternate paths for the high voltage current to bypass the gap causing the maximum voltage to get limited to a lower value. This results in voltage surge of lower which may be insufficient for the spark to jump across the plug intensity gap points to cause the plug to missing and may result in stoppage of cylinder functioning as a power unit. In case , some foreign material or carbon particles gets lodged in between the electrodes, plug may be short circuited.
In order to allow the voltage to built up to high value which is sufficient for jumping across the air gap sometimes an auxiliary air gap is introduced in the plug circuit. This high value of the voltage would be sufficient for the spark to occur at the plug points to provide an adjustable air gap is generally used based on this basic principle of air gap.
DISMANTLING AND ASSEMBLING OF MARUTI 800 PETROL ENGINE CYLINDER BLOCK
Remove all nuts using spanner set. Remove all the components like crank shaft, piston and cam shaft. Remove crank using loosening all nuts holding it while remaining case should be taken not to drop anything. All external connection tables to resist the removal of piston should be dismantled.
The crank shaft, cam shaft, piston...etc is inspected carefully for wear and tear. All the bearing of the crank shaft are inspected carefully for wear. Remove all the worn out bearing and use new one reassembling. The piston rings are checked for wear the cylinder block is inspected carefully for overtly. The crank is also checked.
ENGINE CYLINDER RECONDITIONING
INSPECTION OF CYLINDER WEAR
At the start of the power stroke, pressures are the greatest. The compression rings are forced with the greatest pressure against the cylinder wall. At the same time, the temperatures are highest while the oil film is least effective in protecting the cylinder walls. Therefore the most wear “Taper” takes place at the top of the cylinder .As the piston moves down on the power stroke, the combustion pressure and temperature decreases. Less wear takes place. The cylinder tent to wear irregularly and slightly oval shaped. . If the bores are not excessively worn, and can be honed or rebored within limits, the clean and service the block. Cylinder- block service is often performed b an automobile shop using cylinder- bore gauge, the cylinder wear (uniform) taper and out of round (ovality) is measured.
The cylinder wear is measured by moving cylinder bore gauge down in the cylinder and rotate at various positions to detect wear.
A quick way to check taper is to push a compression ring down to the lower limit of ring travel. Measure the ring gap with a thickness gauge. Then pull the ring up to the upper limit of ring travel. Re measure the gap, the top gap minus the bottom gap divided by three gives the appropriate cylinder taper. This can also be done by measuring cylinder bore using bore gauge in lateral ad longitudinal axis at top and bottom positions. If you minus top and bottom measurements, it gives taper and if you minus lateral and longitudinal measurements it gives ovality.
As a first step, the block should be cleaned. The decision on whether the cylinders are to be honed or bored depends on the amount of cylinder wear; the hone uses a set of abrasive stones which are turned in the cylinder. Honing should leave a cross hatch pattern in the cutting tool where cylinder wear is not excessive, only honing is enough .But if wear is excessive, then cylinder must be removed and oversize pistons installed.
PROCEDURE FOR CYLINDER REBORING
Mount the machine on the cylinder block as shown in figure 3. With the help of centering jaws, fitted on the boring spindle, the spindle position has to be centered. Once it is centered, insert the Jacky in the 2nd or 3rd cylinder (If the 1st cylinder has to be bored) and tighten the clamping setup to firmly hold the clamping with the machine on the block so that the position of the spindle does not change .Then set the tool length with tool holder using a micrometer .Then the tool is mounted and the boring is done to remove required material.
INSTALLING CYLINDER SLEEES
The sleeves are pressed into the cylinder if the cylinder is excessively worn out or scored cylinders and in case of cracked blocks. The cylinders are over sized to make the sleeves. by using pneumatic hammers, the sleeves are hammered in to the cylinder . The sleeves are then finished to the proper size to take a standard piston and set of rings.
Before assembling, clean out oil, all the parts using oil can. Make sure that the pistons are fitted in their respective cylinders by using piston ring compressor. Then refit various parts removed from the cylinder block.
5. 3-D MODEL OF STAND
The cooling system used here is indirect or water cooling (Thermosyphon system)
Referring Fig, this system does not consist of water pump but the circulation of water through the jackets and radiator is maintained only by means of natural convection which is called Thermosyphon.
This system is very simple and cheap but has some disadvantages by which it could not be much popular. Its cooling rate is slow. It always needs a particular or minimum level of water. It needs a big size radiator which requires more space. Therefore these are the main drawback of this system.
Reconditioning of 3-Cylinder Maruti 800 engine was carried out in this Mini project and made it in working condition. Worn-out parts were replaced and all electrical and mechanical accessories were fitted and made it functioning.