MARMARA ÜNİVERSİTESİ TEKNOLOJİ FAKÜLTESİ

Transkript

1 MARMARA ÜNİVERSİTESİ TEKNOLOJİ FAKÜLTESİ Motor Testleri HAZIRLAYAN: Yrd. Doç. Dr. Abdullah DEMİR

2 TYPICAL ENGINE-RELATED COMPLAINTS Engine Performance Problems No-start Hard starting Stalling Misfire Hesitation Surging Lack of power Ping (spark knock) Rod Knock Backfire Induction Backfire Excessive Oil Consumption Over Heating Tip-in WOT Vapor Lock Run-On Intermittent

3 TYPICAL ENGINE-RELATED COMPLAINTS Diagnostic Tools Vacuum gauge Compression tester Cylinder leakage tester Stethoscope Crankcase pressure tester Oil pressure gauge Cooling inspection tools Spark plug condition

4 TYPICAL ENGINE-RELATED COMPLAINTS Typical engine mechanical-related complaints include the following: 1. Excessive oil consumption 2. Engine misfiring 3. Loss of power 4. Smoke from the engine or exhaust 5. Engine noise

5 ENGINE SMOKE DIAGNOSIS The color of engine exhaust smoke can indicate what engine problem might exist. Blue - Blue exhaust indicates that the engine is burning oil. Black - Black exhaust smoke is due to excessive fuel being burned in the combustion chamber. White (steam) - White smoke or steam from the exhaust is normal during cold weather and represents condensed steam. FIGURE: White steam is usually an indication of a blown (defective) cylinder head gasket that allows engine coolant to flow into the combustion chamber where it is turned to steam.

6 Note: The Driver is Your Best Resource The driver of the vehicle knows a lot about the vehicle and how it is driven. Before diagnosis is started, always ask the following questions: When did the problem first occur? Under what conditions does it occur? Cold or hot? Acceleration, cruise, or deceleration? How far was it driven?

7 VISUAL CHECKS Oil Level and Condition The first and most important test that can be performed is a careful visual inspection. The first area for visual inspection is oil level and condition. Oil level oil should be to the proper level Oil condition Using a match or lighter, try to light the oil on the dipstick; if the oil flames up, gasoline is present in the engine oil. Drip some of the engine oil from the dipstick onto the hot exhaust manifold. If the oil bubbles or boils, there is coolant (water) in the oil. Check for grittiness by rubbing the oil between your fingers. Most mechanical engine problems are caused by overheating. The proper operation of the cooling system is critical to the life of any engine. Grittiness = kumluluk, macunsu yapı.

8 VISUAL CHECKS Oil Leak Oil leaks can lead to severe engine damage if the resulting low oil level is not corrected. Besides causing an oily mess where the vehicle is parked, the oil leak can cause blue smoke to occur under the hood as leaking oil drips on the exhaust system. FIGURE 3 The transmission and flex plate (flywheel) were removed to check the exact location of this oil leak. The rear main seal and/or the oil pan gasket could be the cause of this leak. FIGURE 4 What looks like an oil pan gasket leak can be a rocker cover gasket leak. Always look up and look for the highest place you see oil leaking; that should be repaired first.

9 ENGINE NOISE DIAGNOSIS An engine knocking noise is often difficult to diagnose. Several items that can cause a deep engine knock include: Valves clicking Torque converter Cracked flex plate Loose or defective drive belts or tensioners Piston pin knock Piston slap Timing chain noise Rod-bearing noise Main-bearing knock

10 ENGINE NOISE DIAGNOSIS FIGURE 6 An accessory belt tensioner. Most tensioners have a mark that indicates normal operating location. If the belt has stretched, this indicator mark will be outside of the normal range. Anything wrong with the belt or tensioner can cause noise. FIGURE 7 A cracked exhaust manifold on a Ford V-8.

11 OIL PRESSURE TESTING Proper oil pressure is very important for the operation of any engine. Low oil pressure can cause engine wear, and engine wear can cause low oil pressure. If main thrust or rod bearings are worn, oil pressure is reduced because of leakage of the oil around the bearings. FIGURE 8 To measure engine oil pressure, remove the oil pressure sending (sender) unit usually located near the oil filter. Screw the pressure gauge into the oil pressure sending unit hole.

12 OIL PRESSURE WARNING LAMP The red oil pressure warning lamp in the dash usually lights when the oil pressure is less than 4 to 7 PSI, depending on vehicle and engine. The oil light should not be on during driving. If the oil warning lamp is on, stop the engine immediately. Resim: Resim: 1 bar equals 14.5 psi

13 Oil Pressure Test This is where the oil pressure sender is removed from. This test accurately measures engine oil pressure. Remove the car s sender unit and attach the shop pressure gauge. Can indicate a variety of engine problems. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

14 Oil Pressure Test Reading Text Oil pressure testing Oil pressure testing is another strong indication of your engines overall internal health. Just as blood pressure can be used to determine the health of a human being. Excessive clearance is most often caused by worn bearings and will cause a decrease in oil pressure. The most common worn bearings would be either the crankshaft main bearings or the connecting rod bearings. In some cases I have also seen worn camshaft bearings cause a low oil pressure reading. Reasons for oil pressure testing A loss of engine performance, flickering pressure warning light, excessive engine noise, and even poor starting can be caused by abnormal or low oil pressure. When the engines oil pressure is too low, premature wear of its internal parts can be one of the results. Any of the above listed problems mentioned will cause me to break out my mechanical pressure gauge and get a reliable reading. Personally I do not trust the oil pressure gauge on the dash. This is because there is a lot of room for error between the electronic sending unit and the gauge itself. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

15 Oil Pressure Test Reading Text (Cont.) Oil pressure testing procedure The easiest way in my opinion, to be sure that you will get an accurate mechanical reading from your oil pressure tester is to remove the factory installed sensor. Whether your vehicle has an idiot light or gauge, you will have an oil pressure sending unit. You will want to make sure that you follow the instructions provided with the fluid pressure tester. Remember if you do not have a good connection you may have a large mess to clean up. I use Teflon tape on the connection fittings. You should also look up the specifications for your engines pressure in a car repair manual. Also note that the pressure is read when the engine is at normal operating temperature and results are recorded at idle speed, and usually around 2000 RPMs. Excessive bearing clearances are not the only possible causes for low oil pressure readings. Sometimes they can be oil pump related problems. An example would be a restricted pump pickup screen. This can be commonly blocked by sludge from lack of maintenance. Also note that a week or broken pressure relief valve, low oil level, contaminated oil, or even a low viscosity oil (wrong weight) can all cause low-pressure readings. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

16 Oil Pressure Test Örnek ÖRNEK: Yağ basıncını kontrol edilmesi: Yağ basıncı; motor devri, yağ sıcaklığı, yağ akışkanlığı, yağ filtresinin kirlilik derecesi gibi çeşitli etkenlere dayanmaktadır. NOT: Yağ basıncını verilen motor devirlerinde kontrol edilmelidir. Yağ sıcaklığı 80 C iken yağ basıncını ölçülür. NOT: Yağ basıncını rölanti devrinde ve 2000 d/d'de ölçün. Focus Atölye El Kitabı, 2001 Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

17 COMPRESSION TEST An engine compression test is one of the fundamental engine diagnostic tests that can be performed. An engine can lose compression by leakage of air through one or more of only three routes: Intake or exhaust valve Piston rings (or piston, if there is a hole) Cylinder head gasket

18 COMPRESSION TEST Step 1 Remove all spark plugs. Step 2 Block open the throttle. Step 3 Thread a compression gauge into one spark plug hole and crank the engine. Step 4 Record the highest readings and compare the results. FIGURE 10 A two-piece compression gauge set. The threaded hose is screwed into the spark plug hole after removing the spark plug. The gauge part is then snapped onto the end of the hose.

19 WET COMPRESSION TEST If the compression test reading indicates low compression on one or more cylinders, add three squirts of oil to the cylinder and retest. This is called a wet compression test, when oil is used to help seal around the piston rings. FIGURE 12 Badly burned exhaust valve. A compression test could have detected a problem, and a cylinder leakage test (leak-down test) could have been used to determine the exact problem.

20 RUNNING (DYNAMIC) COMPRESSION TEST A compression test is commonly used to help determine engine condition and is usually performed with the engine cranking. A running compression test, also called a dynamic compression test, is a compression test done with the engine running rather than during engine cranking as is done in a regular compression test. Typically, the higher the engine RPM, the lower the running compression. For most engines, the value ranges are as follows: Compression during cranking: 125 to 160 PSI Compression at idle: 60 to 90 PSI Compression at 2000 RPM: 30 to 60 PSI

21 RUNNING (DYNAMIC) COMPRESSION TEST Performing a Running Compression Test With one spark plug removed from the engine, use a jumper wire to ground the spark plug wire to a good engine ground. Start the engine, push the pressure release on the gauge, and read the compression. Increase the engine speed to about 2000 RPM and push the pressure release on the gauge again. Read the gauge. Stop the engine, reattach the spark plug wire, and repeat the test for each of the remaining cylinders.

22 Kompresyon Testi - Özet Kompresyon testi, motorun üst kısmının mekanik durumu - pistonlar, segmanlar, supaplar, silindir kapağı contalarıhakkında bilgi verir. Özellikle de segmanların aşınması, arızalı supaplar ve yuvaları veya özelliğini kaybetmiş kapak contaları nedeniyle ortaya çıkan sızıntı nedeniyle basıncın düştüğünü bildirir. Note: Things that can cause low compression are burned valves, a blown head gasket and worn rings. Also a slipped timing belt or chain that holds the valves open during the compression stroke. Three more I can think of would be worn valve seats, a cracked cylinder head, or even an engine block crack can also cause compression problems. Motorlardaki ne gibi durumlar kompresyon kaçaklarına sebebiyet verir. supap saplarının fazla aşınması, supaplarda boşluk olmaması, supap yaylarının ters takılması, piston-segman-silindirlerin aşınması, segman ağız aralıklarının üst üste gelmesi, bozuk conta veya arızalı silindir kapağı Bozuk conta veya arızalı silindir kapağı gibi durumlar silindirlerde sıkıştırma ve ateşleme zamanlarında silindir içerisinde oluşan basıncın (kompresyonun); soğutma suyuna, kartere, diğer silindirlere veya dışarıya kaçmasına neden olur.

23 Kompresyon Testi - Özet Supaplar ve Kompresyon Kaçakları Supap saplarındaki fazla aşıntı supapların kapanması sırasında supap yuvasının bozulması ve zamanla kompresyon kaçaklarının oluşmasına neden olmaktadır. Supaplar uzun süre çalıştıktan sonra, supaplar ve yuvaları aşınarak genişlikleri artar. Belirtilen değerlerden geniş supap yuvasında, supap kapandıktan sonra birim alana düşen yay basıncı azalacağı için supaplar sızdırmazlık görevini yerine getiremez ve kompresyon kaçağına yol açar. Kompresyon kaçağı sırasında, sıcak gazlar supap ve yuvasını yakabilir. Supap yaylarının ters takılması durumunda da zamanla benzer durumlar görülebilir. Ayrıca yay basıncının düşmesi, supapların yuvasına belirli bir basınçla oturmaması ve supap boşluğunun olmaması durumlarında da, supap yuvasına oturamaz, motorda kompresyon kaçakları meydana gelir. Note: If the reading increases more then 10 psi with the presence of oil in the cylinder the most likely cause of the low compression reading was a poor piston ring sealing. Kompresyon ölçümünde, motorun en az 4 sıkıştırma zamanı yapmasına dikkat edilir. Kompresyon manometresinin ucunda bulunan adaptörün buji yuvasına tam oturması ve kompresyon basınç değerinin tam okunmasına dikkat edilir. Kompresyon muayenesi sonucunda değer katalog değerinin altında ise silindire yağlı kompresyon testi uygulanır. Silindire buji deliğinden bir miktar yağ sıkılarak motor tekrar çevrilerek en az 4 sıkıştırma yapması sağlanır. Bu sıkıştırma sonucunda elde edilen değer, yağsız kompresyon muayenesindeki değerden farklı ise arızanın silindir-piston-segman grubundan olduğu, eğer değerde bir değişme olmuyor ise arızanın supaplardan kaynaklandığı anlaşılır. 1 bar equals 14.5 psi

24 Kompresyon Testi Reading Text Engine compression test The engine compression test will bring you back to the basics of engine diagnosis. Sometimes do it yourself Auto mechanics will start looking for the root cause of their problems in high tech automobile systems. Even if this test does not uncover your problem, it will still give you a great indication of your engines overall health. I also recommend it for people buying high mileage used automobiles. Why perform a compression test? Internal combustion engines depend on the compression of the air fuel mixture to maximize the power produced by the engine. The upward movement of the piston on the compression stroke will compact the air fuel mixture within the sealed chamber raising the temperature of the charge. This makes it easy to ignite and supports complete combustion. An engine with poor compression, uneven results as in different readings from cylinders above or below 30 psi or low total compression can get very poor fuel economy and may not be able to pass a required state emission smog test. It will also not run correctly and can't be tuned properly. You cannot make adjustments on modern engines to compensate for low compression. If a rough running engine condition is present this might be considered a symptom that suggests the cause of the problem might be poor compression. Keep in mind other problems can cause this condition.

25 Kompresyon Testi Engine compression test procedure A compression gauge is used to check the cylinder sealing capabilities. Before conducting a compression test, it is recommended to disable the ignition and the fuel system so the motor does not fire up during testing. It is also recommended to prop open the throttle plate into a wide-open position to allow an unrestricted amount of air to enter the cylinder during the engine test. I like to mark the spark plug wires and remove all the spark plugs. Connecting a remote starter button to the starter system will allow you to perform the tests on your own instead of having someone crank over the engine for you. Install the compression gauge/tester on the number one cylinder. Most compression gauges are easy to use and have the same size thread as the spark plug and just screws into the spark plug hole. Next crank the engine over and allow it to turn at least four revolutions. Then write down the reading after the fourth. After you perform this procedure on all cylinders, you can then compare the pressure readings. Note that before you remove the compression gauge from each cylinder, make sure you release the pressure by using the release valve on the tester.

26 Kompresyon Testi Engine compression test low readings If you have several cylinders or even one cylinder with a low compression reading a wet compression test is then recommended. The procedure performed above is called a dry engine compression test. A wet test is when you squirt a small amount of engine grade oil into the weak cylinders. Reinstall the compression gauge into that cylinder and then conduct the test the same way as above by cranking the engine at least four revolutions. Document the reading next to your dry compression reading that you recorded earlier. If the reading increases more then 10 psi with the presence of oil in the cylinder the most likely cause of the low compression reading was a poor piston ring sealing. This is an indication that the rings are simply worn, often found on engines with high miles. The engine compression test is quick and easy to perform on some cars. The results obtained from the procedure can give you an over view of the engines health. If a cylinder has low compression there could be a few other reasons for the low readings.

27 Silindir Sızıntı Testi Cylinder leakage test / Silindir Sızıntı Testi Bir kompresyon testi, silindirlerde düşük okumalar gösterirse, silindir sızıntı testi yapılmalıdır. Sızıntı testleri, kompresyon kayıp yüzdesini ölçmek için yapılır. Bir sızıntı test cihazıyla, buji deliğinden bir silindire sıkıştırılmış hava uygulanır. Hava silindire uygulanmadan önce, bu silindirin pistonu üst ölü noktada olmalı ve bu silindirin supapları kapalı olmalı yani kompresyon/sıkıştırma ÜÖN de olmalıdır. Compressed air (80 to 90 psi) is then fed into the cylinder.

28 Silindir Sızıntı Testi Cylinder leakage test / Silindir Sızıntı Test Okumaları Bir okuma %0 olursa o silindir içinde hiçbir sızıntı olmadığı anlamına gelir. %100 bir okuma olursa, silindir hiçbir basıncı koruyamıyor anlamına gelir. %0 dan az fazla olan herhangi bir okuma bir miktar sızıntı olduğunu gösterir. The location of the compression leak can be found by listening and feeling around various parts of the engine for air leaks. If air is felt or heard leaving the throttle plate assembly a leaking intake valve is indicated at that point. If a bad exhaust valve is responsible for the cylinder leakage air can be felt and heard leaving the exhaust system during the test. When air is heard escaping the cylinder head area than an inspection of the head itself must be performed and may indicate a cracked cylinder head. Compressed air (80 to 90 psi) is then fed into the cylinder.

29 Silindir Sızıntı Testi Head gasket problems cause cylinder leakage On the subject of head gaskets when you apply compressed air to a cylinder and you hear air leaving the radiator this is a good indication of a faulty head gasket or even a cracked block. You may also notice bubbles in the radiator overflow tank. Compression should be completely sealed from the cooling system and no air should enter any parts of the engine cooling system. If the cylinder leakage test reveals a problem another possible cause could be worn piston rings. In this case air can be heard, rushing down past the Pistons and flowing into the crankcase and in extreme cases, you can feel air leaving the valve cover breather or vent tube. I use compressed air when testing for a leaking cylinder. As I mentioned earlier the sound of rushing air out of the exhaust means a leaking exhaust valve. The more air volume the easier to hear it. The rushing air through the intake means a intake valve problem. Internal engine diagnosis using compressed air can be very accurate and easier then other methods such as dis-assembly and inspection. It is the repairs needed that will be the hard part. You will need an automotive compressor. Bigger is better but you do not need a giant one to test. The volume of air required is small because you are only filling the combustion chamber not the whole cylinder.

30 CYLINDER LEAKAGE TEST This test involves injecting air under pressure into the cylinders one at a time. The amount and location of any escaping air helps the technician determine the condition of the engine. To perform the cylinder leakage test, take the following steps: For best results, the engine should be at normal operating temperature (upper radiator hose hot and pressurized). The cylinder being tested must be at top dead center (TDC) of the compression stroke. Calibrate the cylinder leakage unit as per manufacturer s instructions. Inject air into the cylinders one at a time, rotating the engine as necessitated by firing order to test each cylinder at TDC on the compression stroke. Evaluate the results: Check the source of air leakage. FIGURE 13 A typical handheld cylinder leakage tester.

31 CYLINDER LEAKAGE TEST FIGURE 14 A whistle stop used to find top dead center. Remove the spark plug and install the whistle stop, then rotate the engine by hand. When the whistle stops making a sound, the piston is at the top.

32 CYLINDER LEAKAGE TEST Evaluating the Results If the leakage is 20% or less the cylinder is OK. If the leakage is greater than 20% check the following: Air escaping from the tail pipe. Burnt exhaust valve. Air escaping from the throttle body. Burnt intake valve. Air escaping from the oil filler. Bad piston rings.

33 Silindir Sızıntı Testi

34 Silindir Sızıntı Testi Reading Text - Cylinder testing tips Note that most engines even new ones will experience some cylinder leakage around the piston rings. And up to 20% is considered acceptable during your cylinder leakage test. You can check your online car repair manuals for the specs on your engine. This is because when the engine is actually running the rings will seal much better due to the up-and-down movement of the piston and the presence of oil lubricating that cylinder. Also note that there should be absolutely no leakage into the cooling system and also the cylinder head. The intake and exhaust valves should also seal at 100% with no leakage into the intake or exhaust systems. In order of importance I perform a complete compression test first and then I performed a cylinder leak down tests as described above. The combination of these tests can often point to the area needing repair.

35 Silindir Güç Denge/leme/ Testi Cylinder balance test - Silindir güç denge/leme/ testi Bir motor kaba bir çalışma koşuluna sahip olduğunda, bu durum motorun bir silindirinin diğer silindirler gibi performans göstermediğine işaret olabilir. Motorun silindirlerinin tümünün aynı miktarda güç üretip üretmediğine bakıldığından bu test için uygun ad silindir güç denge testidir. Normal koşullarda ve düzgün bir motor çalışmasında bütün silindirler aynı enerjiyi üretecektir. Bu teyit ve test edilebilir. Motorun güç dengesini kontrol etmek için bujiler üzerinden kısa devre veya silindirde ateşleme olmayacak şekilde önlem alınır. Sonra, motor hızındaki değişme saptanır ve karşılaştırılır. If all of the cylinders are producing the same amount of power the engine RPMs will drop exactly the same amount on each cylinder that is canceled. The cause of unequal power balance can mean a problem in the cylinders themselves, as well as in the piston rings, valve train, head gasket, fuel system, or even the ignition system. Be careful not to run the engine with a shorted cylinder for more than 10 or 15 seconds. The unburned fuel in the exhaust can damage the catalytic converter and create an unsafe situation.

36 CYLINDER POWER BALANCE TEST Most large engine analyzers and scan tools have a cylinder power balance feature. The purpose of a cylinder power balance test is to determine if all cylinders are contributing power equally. Power Balance Test Procedure The acceptable method of canceling cylinders, which will work on all types of ignition systems, including distributorless, is to ground the secondary current for each cylinder. The cylinder with the least RPM drop is the cylinder not producing its share of power. FIGURE 15 Using a vacuum hose and a test light to ground one cylinder at a time on a distributorless ignition system. This works on all types of ignition systems and provides a method for grounding out one cylinder at a time without fear of damaging any component.

37 Silindir Güç Denge/leme/ Testi A cylinder power balance test gives an indication of each cylinders power, testing its power and effectiveness compared to the others. Each cylinder is tested at a particular speed ( RPM) and the RPM drop is recorded. The test is best performed with an engine analyzer. If an analyzer is unavailable, the technician can momentarily (a few seconds) disconnect the plug wire from its corresponding spark plug or distributor connection to disable the desired cylinder. On a distributorless system the culprit will be a coil, wire, or module. If two cylinders are dead and share a common coil, it is likely the coil is at fault. These are known as waste spark ignition systems. They use group firing. Newer cars may compensate. A prolonged open in the secondary ignition system may cause damage to the coil or ignition module. Sometimes you will need to disconnect a sensor like an O2 sensor so the computer will not try to compensate for the sudden drop in RPM. If in doubt go ahead and check the manufacturers specifications before removing the spark plug boot and remember safety first. Use a grabber or a tool that will protect your hand from shock. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

38 Silindir Güç Denge/leme/ Testi Notice the RPM drop as the plug wire is removed from the plug. If a cylinders RPM drop is not consistent with the others, this indicates a problem with that cylinder. An engine analyzer tests each cylinder and then compares the results. An engine analyzer or dedicated tool is best used for testing COP ignition systems. This is because coil damage may result from removing a coil pack while the engine is running. Check with the manual, there are many ways to cancel a cylinder such as removing an associated connector. Look for anything that would effect a cylinders power. A leak in the intake at that cylinder or a clogged fuel injector. The ignition system is often at fault. Look for crossed wires or a weak coil on a coil on plug ignition system. This is common these days and has taken over the distributor as an "easy to identify" source of so many ignition problems throughout the years. The engine intake and exhaust valves, piston and piston rings, or the head gasket may be at fault as well. Anything associated to that particular cylinder or cylinders. A faulty head gasket or crossed ignition wires will cause two adjacent cylinders to fail the balance test. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

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42 VACUUM TESTS Vacuum is pressure below atmospheric pressure and is measured in inches (or millimeters) of mercury (Hg). An engine in good mechanical condition will run with high manifold vacuum. Manifold vacuum is developed by the pistons as they move down on the intake stroke to draw the charge from the throttle body and intake manifold. Vacuum tests include testing the engine for cranking vacuum, idle vacuum, and vacuum at 2500 RPM. There are a number of Vacuum Tests including: Cranking Vacuum Test Idle Vacuum Test FIGURE: An engine in good mechanical condition should produce 17 to 21 in. Hg of vacuum at idle at sea level.

43 VACUUM TESTS Low and Steady Vacuum If the vacuum is lower than normal, yet the gauge reading is steady, the most common causes include: Retarded ignition timing Retarded cam timing Fluctuating Vacuum If the needle drops, then returns to a normal reading, then drops again, and again returns, this indicates a sticking valve. A common cause of sticking valves is lack of lubrication of the valve stems. Önemli not: 20 C de atmosfer basıncı 761 mm Hg sütunudur. An engine in good mechanical condition should produce 17 to 21 in. Hg of vacuum at idle at sea level. FIGURE : A steady but low reading could indicate retarded valve or ignition timing. Not2: Vakım basıncının 0,3 atm olması demek mutlak basıncın 0,7 atm olmasıdır.

44 VACUUM TESTS Fluctuating Vacuum FIGURE 18 A gauge reading with the needle fluctuating 3 to 9 in. Hg below normal often indicates a vacuum leak in the intake system. FIGURE 19 A leaking head gasket can cause the needle to vibrate as it moves through a range from below to above normal.

45 VACUUM TESTS Fluctuating Vacuum FIGURE 20 An oscillating needle 1 or 2 in. Hg below normal could indicate an incorrect air fuel mixture (either too rich or too lean). FIGURE 21 A rapidly vibrating needle at idle that becomes steady as engine speed is increased indicates worn valve guides.

46 VACUUM TESTS Fluctuating Vacuum FIGURE 22 If the needle drops 1 or 2 in. Hg from the normal reading, one of the engine valves is burned or not seating properly. FIGURE 23 Weak valve springs will produce a normal reading at idle, but as engine speed increases, the needle will fluctuate rapidly between 12 and 24 in.hg.

47 VACUUM TESTS Fluctuating Vacuum FIGURE 24 A steady needle reading that drops 2 or 3 in. Hg when the engine speed is increased slightly above idle indicates that the ignition timing is retarded. FIGURE 25 A steady needle reading that rises 2 or 3 in. Hg when the engine speed is increased slightly above idle indicates that the ignition timing is advanced.

48 VACUUM TESTS Fluctuating Vacuum FIGURE 26 A needle that drops to near zero when the engine is accelerated rapidly and then rises slightly to a reading below normal indicates an exhaust restriction.

49 EXHAUST RESTRICTION TEST If the exhaust system is restricted, the engine will be low on power, yet smooth. Common causes of restricted exhaust include the following: Clogged catalytic converter. Clogged or restricted muffler. Damaged or defective piping.

50 TESTING BACKPRESSURE WITH A VACUUM GAUGE A vacuum gauge can be used to measure manifold vacuum at a high idle (2000 to 2500 RPM). If the exhaust system is restricted, pressure increases in the exhaust system. This pressure is called backpressure.

51 TESTING BACKPRESSURE WITH A PRESSURE GAUGE Exhaust system backpressure can be measured directly by installing a pressure gauge into an exhaust opening. This can be accomplished in one of the following ways: With an oxygen sensor. With the exhaust gas recirculation (EGR) valve. With the air-injection reaction (AIR) check valve. FIGURE 27 A technician-made adapter used to test exhaust system backpressure. The upstream oxygen sensor is removed and the adaptor is threaded into the opening in the exhaust and then a pressure gauge to connected to the hose fitting so that backpressure can be measured.

52 DIAGNOSING HEAD GASKET FAILURE Several items can be used to help diagnose a head gasket failure: Exhaust gas analyzer Chemical test Bubbles in the coolant Excessive exhaust steam FIGURE 28 A tester that uses a blue liquid to check for exhaust gases in the exhaust, which would indicate a head gasket leak problem.

53 DASH WARNING LIGHTS Most vehicles are equipped with several dash warning lights often called telltale or idiot lights. These lights are often the only warning a driver receives that there may be engine problems. A summary of typical dash warning lights and their meanings follows. Oil (Engine) Light The red oil light indicates that the engine oil pressure is too low (usually lights when oil pressure is 4 to 7 PSI [20 to 50 kpa]). Normal oil pressure should be 10 to 60 PSI (70 to 400 kpa) or 10 PSI per 1000 engine RPM. Coolant Temperature Light If the coolant temperature warning light comes on during driving, this usually indicates that the coolant temperature is above a safe level, or above about 250 F (120 C). Normal coolant temperature should be about 200 to 220 F (90 to 105 C).

54 SUMMARY The first step in diagnosing engine condition is to perform a thorough visual inspection, including a check of oil and coolant levels and condition. Oil leaks can be found by using a white powder or a fluorescent dye and a black light. Many engine-related problems make a characteristic noise. A compression test can be used to test the condition of valves and piston rings. A cylinder leakage test fills the cylinder with compressed air, and the gauge indicates the percentage of leakage. A cylinder balance test indicates whether all cylinders are working okay. Testing engine vacuum is another procedure that can help the service technician determine engine condition.

55 Crankcase Pressure Test - Blow-by Test This test checks the amount of gases passing the piston rings (also called a blow-by test). The tester connects in place of the PCV valve. The engine is run and the amount of blow-by it measured. This test is weird, but it really shows if an engine has bad rings.

56 Oil Pressure Test Daha önceki slaytlarda anlatıldı

57 Cooling System Inspection Check the following: Coolant level Coolant condition Anti-freeze protection Hoses and belts Check the water pump Radiator fins Pressure test for leaks Test cap Determine thermostat condition Check fan for proper operation

58 Cooling System Inspection Loss of Coolant Leaks Loss to combustion chamber Block Test This test is used to determine a cracked head, block or head gasket. This test is performed by taking vapor from the top of the cooling system and running it through a blue liquid. If the fluid stays blue the engine is OK. If the fluid turns yellow the coolant is leaking into the combustion chamber.

59 Cooling System Inspection Damaged Cylinder Head

60 REVIEW QUESTIONS Describe the visual checks that should be performed on an engine if a mechanical malfunction is suspected. List three simple items that could cause engine noises. Describe how to perform a compression test and how to determine what is wrong with an engine based on a compression test result. Describe the cylinder leakage test. Describe how a vacuum gauge would indicate if the valves were sticking in their guides. Describe the test procedure for determining if the exhaust system is restricted (clogged) using a vacuum gauge.

61 Morse testi Motor fren gücünün indike güçten daha küçük olmasına sebep olan güç kayıplarının temel nedenleri; motor yataklarındaki, supaplardaki, pistonsegman ve silindirlerdeki sürtünme kayıplarıdır. Morse testi, sürtünme kayıpları ve aynı zamanda çok silindirli bir motorun indike gücü için yaklaşık değerler sağlayan bir motor testidir. Morse testi, bir dinamometrede sabit motor devrinde yürütülür. Testin birinci fazında tüm silindirler ateşlediğinde motorun fren gücü kaydedilir. Devamında bir silindirin ateşlemesi devre dışı bırakılır ve dinamometrenin yükü; motoru, tüm silindirlerde ateşlemenin olduğu durumdaki hıza getirilmesi için ayarlanır. Sonra fren gücü kaydedilir. The Morse test is applicable only to multicylinder engines. In this test, the engine is first run at the required speed and the output is measured. Then, one cylinder is cut out by short circuiting the spark plug or by disconnecting the injector as the case may be. Under this condition all other cylinders motor this cut-out cylinder. The output is measured by keeping the speed constant at its original value. The difference in the outputs is a measure of the indicated horse power of the cut-out cylinder. Thus, for each cylinder the ip is obtained and is added together to find the total ip of the engine. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

62 Morse test Definition 1: This method is used in multi-cylinder engines to measure I.P with out the use of indicator. The BP of the engine is measured by cutting off each cylinder in turn. Definition 2: In such cases the morse test can be used to measure the indicated power and mechanical efficiency of multi cylinder engines. Reading Text For slow speed engine the indicated power is directly calculated from the indicator diagram. But in modern high speed engines, it is difficult to obtain accurate indicator diagram due to inertia forces, and therefore, this method cannot be applied. In such cases the morse test can be used to measure the indicated power and mechanical efficiency of multi cylinder engines. The engines test is carried out as follows. The engine is run at maximum load at certain speed. The B.P is then measured when all cylinders are working. Then one cylinder is made in operative by cutting off the ignition to that cylinder. As a result of this the speed of the engine will decrease. Therefore, the load on the engine is reduced so that the engine speed is restored to its initial value. The assumption made on the test is that frictional power is depends on the speed and not upon the load on the engine. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

63 Morse test Reading Text Frictional losses in the engine bearings, the valve train and the piston and piston rings are the main causes of the power loss that makes the brake power of an engine smaller than the indicated power. The Morse test is an engine test that give an approximate value for the frictional losses and which also provides an approximate value for the indicated power of a multi-cylinder engine. The Morse test is conducted at constant engine speed on a dynamometer. The first phase of the test records the brake power of the engine when all cylinders are firing. Subsequently, one cylinder is prevented from firing and the dynamometer load is adjusted to bring the engine up to the same speed as it was when all cylinders were firing, the brake power then being recorded. The difference between brake power with all cylinders working and that obtained when one cylinder is cut out is the indicated power of the cylinder that is not working. This procedure is repeated for each of the cylinders and the indicated power for the whole engine is the sum of the power of the individual cylinders. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

64 Dinamometre Testleri Testing Commonly Measured Parameters 1. Torque 2. Speed 3. Fuel Consumption 4. Emissions 5. Temperatures (head, exhaust, coolant) Occasionally Measured Parameters 1. Combustion Pressure 2. Ignition Timing 3. Dynamics (accelerations, vibrations, stress) 4. Knock 5. Intake/Exhaust Pressures 6. Valve Lift 7. Acoustics Note: These parameters can be measured manually or automatically. Dr. Horizon Gitano-Briggs, Dynamometry and Testing of Internal Combustion Engines Seminar; University Science Malaysia, June Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

65 Motor deneyleri genel olarak a) Bir motorun; yapımcı firmanın garanti ettiği karakteristik özellikleri gerçekleyip gerçeklemediğinin kontrolü, b) Motorları geliştirme çalışmalarında; çeşitli yapısal (konstrüktif) ve işletme özelliklerinin motor karakteristikleri üzerindeki etkilerinin belirlenmesi, amaçları ile yapılır. Motor Deneyleri arfoyleri/lab18.pdf Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

66 Motor Deneyleri Bu amaçlarla; motorların istenen bazı işletme büyüklüklerinin sabit tutulabildiği ve istenen bazı büyüklüklerin değiştirilebildiği bir deney düzeneğine bağlanmaları ve çalıştırılmaları gerekir. Böylece motor çeşitli koşullar altında çalışırken gerekli bilinmeyen büyüklükler ölçülür. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

67 Motor Deneyleri Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

68 Motor Deneylerinde Çeşitli Büyüklüklerin Ölçülmesi: 1. Motorun yüklenmesini ve döndürme momentinin ölçülmesini sağlayacak bir yükleme elemanı, 2. Devir sayısını ölçmeye yarayan bir takometre, 3. Yakıt tüketimini ölçmeyi sağlayan bir ölçekli kap, 4. Hava debisini ölçmeye yarayan bir orifıs veya lüle ve bir sıvılı manometre düzeneği, 5. Soğutma suyunun debisini ölçmeye yarayan bir lüle ve manometre veya rotametre düzeneği, 6. Egzoz gazlarının sıcaklığını ölçmeye yarayan bir termokupl termometre ve göstergesi, 7. Emme havası giriş, soğutma suyu giriş ve çıkış sıcaklıklarını ölçmeye yarayan termometre ve göstergeler bulunan bir deney sistemi kullanılmalıdır. Motor Deneyleri Rotametre: Rotametre; içinden debisi ölçülecek olan sıvının aktığı, düşey konik bir silindir ve silindir içinde hareket edebilen bir topaçtan oluşur. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

69 Motor Deneyleri İndikatör diyagramı: Silindir içindeki basınç değişimini gösteren indikatör diyagramı günümüzde elektronik yollarla duyarlı bir şekilde belirlenebilmektedir. Elektronik yöntemle indikatör diyagramının belirlenmesinde, silindir içindeki basınç değişimi bir transducer ile elektrik sinyallerine dönüştürülmekte, daha sonra bu sinyaller bir amplifikatörde yükseltilerek bir bilgisayara aktarılabilmekte veya bir osiloskoba gönderilebilmektedir. Basıncın krank açısına veya silindir hacmine göre değişimi osiloskobun ekranında gözlenebilmekte, istenirse fotoğrafı da çekilebilmektedir. Bu yolla çeşitli motor karakteristiklerinde yapılacak değişikliklerin indikatör diyagramı üzerindeki etkileri deneysel olarak incelenebilmekte, ayrıca indikatör diyagramı ile teorik hesaplama yöntemlerinin doğruluk derecesi kontrol edilebilmektedir. Transducer: Bir sinyali istenilen sinyale çeviren etkin devre elemanıdır. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

70 Egzoz gazları: Egzoz gazları çeşitli kimyasal, optik veya değişik yollarla analiz edilerek motor karakteristiklerinin egzoz gazları ve dolayısı ile yanma üzerindeki etkileri incelenebilmektedir. Motor Deneyleri Sıcaklık dağılımları: Değişik motor elemanları üzerine yerleştirilen elektronik termometrelerle sıcaklık dağılımının, ısıl yüklerin çeşitli karakteristiklere bağlı olarak nasıl değiştikleri incelenebilmektedir. Gaz akışı olayları: Motorların emme ve egzoz kanallarındaki gaz akışı olayları ve silindir içindeki gaz hareketleri; kızgın tel anemometresi veya laserdoppler anemometresi yardımı ile deneysel olarak incelenebilmektedir. Böylece motorların emme ve egzoz donanımlarının ve yanma odalarının geliştirilmesine çalışılmaktadır. Anemometre, rüzgar/hava hızını ölçen alettir. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

71 Motor Deneyleri Motor Deneyi Çeşitleri: Motorlar uygulamada çoğunlukla ya taşıtlarda ya da stasyoner olarak (generatörlerde veya inşaat makinelerinde) kullanılmaktadır. Bu kullanım alanlarına göre motorlardan beklenen özellikler farklı farklıdır. Örneğin; bir taşıt motoru sabit gaz durumunda motor yüküne göre belirli bir alt ve üst devir sayısı aralığında çalışmalı ve bu aralıkta özellikleri bilinmelidir. Öte yandan bir santral motoru; üretilen elektriğin belirli bir frekansta olması için, sabit devir sayısında çalışmalıdır. Motorların bu farklı tür çalışma koşullarına uygun olarak, motor deneyleri de farklı olabilir. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

72 Motor Deneyleri 1. Taşıt Motorları Deneyleri: Bu amaçla motor çalıştırıldıktan sonra; bir taraftan gaz arttırılırken, araç bir su freni veya jeneratör aracılığı ile yavaş yavaş yüklenir. Gaz kolu istenen konuma getirildiğinde motor uygun şekilde yüklenerek en düşük devirde kararlı çalışması sağlanır. Bu yük altında motorun devir sayısı en düşük (minimum) devir sayısıdır. Daha sonra yük yavaş yavaş azaltılarak motorun devir sayısının artması sağlanır. Her adımda; devir sayısı, döndürme momenti, gibi motorun istenen karakteristikleri ölçülür. Her hızdaki ölçüm yapılırken motorun en az 1 dakika kararlı olarak çalışması gerekir. Böylece, belirli gaz konumunda, en düşük devirden en yüksek devire kadar motorun karakteristikleri belirlenmiş olur. Benzer işlemler istenirse değişik gaz konumlarında da yinelenir. Ölçülen değerler kullanılarak efektif güç, ortalama efektif basınç, özgül yakıt tüketimi, efektif verim vb. gibi çeşitli teknik büyüklükler hesaplanır. Daha sonra hesaplanan bu değerler devir sayısına bağlı olarak eğriler şeklinde veya performans eğrileri biçiminde çizilir. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

73 Motor Deneyleri 2. Motorların Geliştirme Deneyleri: Motorları geliştirme çalışmalarında; motor belirli bir gaz konumunda çalışırken sıkıştırma oranı, ateşleme avansı, yakıt-hava oranı vb. gibi teknik özelliklerden biri değiştirilir. Örneğin her sıkıştırma oranında yükleme ayarlanarak motorun devir sayısının sabit kalması sağlanır. Her adımda gerekli büyüklükler ölçülür. Elde edilen sonuçların değerlendirilmesi ile sıkıştırma oranının motorun çeşitli teknik özelliklerini nasıl etkilediği ve en uygun sıkıştırma oranının ne seçilmesi gerektiği belirlenmiş olur. 3. Stasyoner Motor Deneyleri: Elektrik santralleri, şantiye ve inşaatlar gibi alanlarda kullanılan stasyoner motorların yükleri en düşük değerden başlamak üzere yavaş yavaş arttırılır ve her yükleme durumunda gaz ayarlanarak devir sayısının sabit kalması sağlanır. Böylece sabit devir sayısında çeşitli yüklerde motorun karakteristik değerleri belirlenir ve daha sonra gerekli işlemler yapılarak istenen büyüklükler hesaplanır. Ölçülen veya hesaplanan bu değerler motor gücüne bağlı eğriler şeklinde değerlendirilir. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

74 Motor Deneyleri 1. Taşıt Motorları Deneyleri: Taşıtlarda, motorun ürettiği güç, güç aktarma organları (kavrama, dişli kutusu, diferansiyel ve akslar) tarafından tekerleklere iletilir ve taşıtın hareketini sağlar. Taşıtların kalkış ve duruşlarında ve çeşitli yol koşularındaki hareketlerinde gerekli döndürme momentleri ve devir sayıları farklı farklıdır. Motorun, taşıtın çalışma koşullarına uyum sağlayabilmesi için, değişik gazlarda ve devir sayılarında çalışması gerekir. Bu nedenle taşıt motorları, sabit gaz durumlarında değişik devir sayılarında denenir. Taşıt motorlarının değişik hızlarda denenebilmesi için; tam gaz, 3/4 gaz, 1/2 gaz, 1/4 gaz gibi istenen gaz durumlarında en düşük ve en yüksek hızların aralığında çalıştırılmaları gerekir. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

75 Motor Deneyleri Bu düzeneklerde gerekli büyüklüklerin ölçülmesi ve hesaplanması: 1. Yükleme Elemanları ve Momentin Ölçülmesi: Motor deneylerinde üretilen gücü yutan ve yüklemeyi sağlayan başlıca iki tür yükleme elemanı kullanılır Jeneratör ile Yükleme (Elektrik Dinamometresi): Motorun mili bir jeneratöre bağlanırsa, motorun ürettiği güç elektrik enerjisine çevrilmiş olur. Bu elektrik enerjisi paralel bağlı dirençlerde ısıya dönüştürülerek harcanabilir. Anahtarlarla kumanda edilen dirençlerden istenilen kadarı devreye sokularak motorun yükü ayarlanmış olur. Elektrik dinamometresinin rotoru denenecek motorun miline, statoru ise bir dengeleme düzeneğine bağlanmıştır. Dinamometre (Jeneratör) çalışırken, yani elektrik üretirken statorda bir zıt elektromotor kuvvet oluşur ve stator rotorun dönme yönünde dönmek ister. Motorun mekanik gücü veya dinamometreden çekilen elektriksel güç arttıkça, etki eden döndürme momenti de büyür. Demek ki statorda bu şekilde oluşan moment; motor milindeki döndürme momentine eşittir. Dinamometrenin statoruna etki eden bu moment bir dengeleme sistemi ile dengelenebilir ve ölçülebilirse, motorun döndürme momenti belirlenmiş olur. Bu amaçla stator, iki ucundan serbestçe dönmesine olanak sağlayan yataklar üzerine oturtulur. Öte yandan statora etki eden moment, bir ucu moment koluna bağlı ve diğer ucu yere sabit olarak tutturulmuş bir yaylı terazi ve moment koluna asılan ağırlıklar tarafından dengelenir. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

76 Motor Deneyleri 1.2. Su Freni ile Yükleme Motor deneylerinde yükleme ve moment ölçümü için uygulanan en yaygın yöntemlerden biri de su freni (hidrolik fren)dir. Hidrolik frenlerde genellikle sıvı olarak su kullanılır. Su frenleri motor yüküne bağlı olarak çeşitli tiplerde yapılmakta ise de çalışma ilkeleri tümünde aynıdır. Su freni motor miline bağlı olarak dönen özel kanatlı bir rotor ve rotoru çevreleyen, yataklar üzerine oturtulmuş bir statordan oluşur. Statorun iç tarafında da kanatlar olabilir ve statora elektrik dinamometresindeki gibi bir moment ölçme düzeneği eklenir. Motor; rotoru çevirmeye başladığında, rotorun kanatları suyu dışa doğru fırlatır ve çevrede girdap hareketleri yapan bir su tabakası oluşur. Böylece girdap, dönme hareketleri ve radyal hareketler gibi karmaşık hareketler yapan su bir taraftan ısınarak motorun ürettiği mekanik enerjiyi yutarken, öte yandan motorun döndürme momentine eşit bir momentle su freninin statorunu çevirmeye çalışır. Stator iki ucundan rulmanlı olarak yataklanmıştır ve üzerine etki eden momentin etkisi ile dönmek ister. Statora eklenen yaylı bir ölçme düzeneği ile hem statorun dönmesi sınırlanır, hem de motorun söz konusu döndürme momentine karşı gelen ve moment koluna etki eden kuvvet ölçülür. Deneyden önce J koluna asılan, bilinen ağırlıkların moment etkilerinden yararlanılarak, motor dururken transducer in kalibrasyonu yapılır. Su freninin içindeki su zamanla ısınacağı için sürekli olarak değiştirilmelidir. Frenin içindeki su miktarı arttıkça yutulan enerji de artar. Su girişine yerleştirilen ayarlanabilir bir A vanası ile, su miktarı ve sonuçta motorun yüklenmesi istenilen şekilde ayarlanır. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

77 Motor Deneyleri Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

78 Motor Deneyleri Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

79 Motor Deneyleri Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

80 Motor Deneyleri Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

81 Motor Deneyleri Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

82 Dinamometre A Dynamometer is a LOAD device It applies a load to an engine so we can test the performance of the engine under a variety of circumstances (Power, Speed) Dr. Horizon Gitano-Briggs, Dynamometry and Testing of Internal Combustion Engines Seminar; University Science Malaysia, June Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

83 Dinamometre Testleri Reading Text: A Dynamometer is load device used to measure an engines torque and speed. We often measure Fuel Consumption, Emissions and other parameters as well. A dynamometer can also be used to control the speed of the engine by varying the load placed on the engine. Dynos are often used to test different engine designs at the same load settings (Torque and Speed) for comparison purposes. We want to test the engine under conditions similar to the actual conditions (speed, torque) in the field, or even simulate an actual drive cycle with the dynamometer Dr. Horizon Gitano-Briggs, Dynamometry and Testing of Internal Combustion Engines Seminar; University Science Malaysia, June Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

84 Dinamometre Testleri Dynamometers There are 2 basic kinds of dynamometers: Absorption Dynamometers: These are devices that absorb the mechanical power from the test engine. Transmission Dynamometers: These are basically torque measurement devices placed in a power transmission link (ie. a shaft). They can be used to measure torque and speed, and thus power. All Absorption Dynamometers share some basic features: The shaft is connected to a Rotor housed in a Stator. There is some form of coupling (mechanical, hydraulic, aerodynamic, electromagnetic) between the Rotor and Stator. Equal and opposite torques are induced on the Rotor and Stator: Dr. Horizon Gitano-Briggs, Dynamometry and Testing of Internal Combustion Engines Seminar; University Science Malaysia, June Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

85 Dinamometre Testleri Various Dyno Designs There are many different designs used in dynamometers. Here are the most common ones: 1. Frictional 2. Hydraulic 3. Generator 4. Eddy current 5. Fan 6. Vehicular 7. Motored Dynos Comparison of Dyno Designs Dr. Horizon Gitano-Briggs, Dynamometry and Testing of Internal Combustion Engines Seminar; University Science Malaysia, June Frictional: Oldest design. Hard to control. Wear on frictional surfaces is a problem. Hydraulic: Highest power in smallest package (pump). Generator: Inexpensive and easy to control. Fairly large for a given power. Eddy current: Easiest to control. Low Inertia and bearing losses. Fan: Very inexpensive. Needs careful calibration. Less accurate. Vehicular: Requires measurement of vehicle mass. Ignores air drag. Good for vehicular studies. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

86 Dynamometer Makine Mühendisliği Automotive Engineering - Powertrain, Chassis System and Vehicle Body Edited by David A. Crolla, 2009 Yrd. Doç. Dr. Abdullah DEMİR

87 Dinamometre Testleri Engine Dynamometer Couples directly to the engine No gearbox or transmission Engine speed = Dyno speed A Dynamometer may also be coupled to the output of a transmission or gear box. Speed and Torque of the engine and dyno are different by the gear ratio (Speed, Torque ). Dr. Horizon Gitano-Briggs, Dynamometry and Testing of Internal Combustion Engines Seminar; University Science Malaysia, June Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

88 Dinamometre Testleri Bearings The body of the dynamometer must be free to rotate, so it is supported on bearings. Dr. Horizon Gitano-Briggs, Dynamometry and Testing of Internal Combustion Engines Seminar; University Science Malaysia, June Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

89 Load Cell Mounting The rotation of the dynamometer housing is resisted by a load cell which measures the force. The Load cell should be loaded in only one direction (ie. axially) to avoid biasing the output. Generally the load cell is mounted so the force is perpendicular to the axis of the shaft. Dinamometre Testleri Torque Measurement Torque is almost always measured with a strain gage instrumented load cell or force transducer. This is a mechanical member which undergoes significant strain with an applied force. Dr. Horizon Gitano-Briggs, Dynamometry and Testing of Internal Combustion Engines Seminar; University Science Malaysia, June Load Cell mounts via ball-joint ends Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

90 Durability is usually expressed as a minimum time or vehicle mileage before the occurrence of any major type of structural failures (e.g., wear-out). For example, a B10 durability life is the expected life (e.g., 20,000 hours or one million miles) at which 10% of the population fails. A B50 durability life is the expected life at which 50% of the population fails. Engine durability testing A durability specification of B10 life at one million miles (or equivalent number of engine hours) represents that 10% of the engine population will fail within one million miles. The equivalent reliability specification can be stated as the reliability is 90% or the probability of failure is 10% at one million miles. Engine durability testing is the most important development work to validate the design after the prototype is available. Typical engine durability tests include full-load test in the lab, over-fueling test, loadcycle tests, field test in vehicles, etc. Motor dayanıklılık testi (Engine durability testing) B10 olarak tanımlanan dayanaklılık ömrü (B10 durability life) beklenen ömürdür. B10, saatlik ya da 1 milyon millik çalışma anlaşılır. 10 ifadesinden bu ömürde üretilen motorlardan %10 nun başarısız olabileceğini göstermektedir. B50 ise belirtilen ömürdeki motorlardan %50 sinin başarısız olabileceği anlamına gelir. Diesel engine system design, Woodhead Publishing Limited, 2011 Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

91 Temel Bazı Kavramlar Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

92 Kütlesel ve Hacimsel debi Dr. M. Azmi AKTACİR-2010-ŞANLIURFA, Harran Üniversitesi Makine Mühendisliği Bölümü Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

93 Kütlesel Debi Ölçme Düzeni Belirli bir zaman aralığında akan akışkanın kütlesinin tartılarak tespiti en basit ve en hassas yöntemdir. Atmosferik şartlarda buharlaşmayan sıvılar için oldukça kolay bir yöntem olmasına rağmen buharlaşabilen sıvı ve gazlar için bu yöntemi kullanırken özel önlem alınmalıdır. Dr. M. Azmi AKTACİR-2010-ŞANLIURFA, Harran Üniversitesi Makine Mühendisliği Bölümü Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

94 Hacimsel debi ölçme düzeni Belirli bir zaman aralığında akan akışkan, hacmi belirlenebilen bir kapta toplanarak veya hacmi belirli bir kaptan, belirli zaman aralığında bu akışkanın kullanılması ile hacimsel debi bulunur. Hacimsel debi ölçümü, kütlesel debi dışında pratikte kullanılan diğer bir yöntemdir. Dr. M. Azmi AKTACİR-2010-ŞANLIURFA, Harran Üniversitesi Makine Mühendisliği Bölümü Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

95 Rotametre: Rotametre; içinden debisi ölçülecek olan sıvının aktığı, düşey konik bir silindir ve silindir içinde hareket edebilen bir topaçtan oluşur. Termokapl: Kısaca Isıl çiftdir. Sıcaklık algılamaya yarayan bir sensördür. Bu sensörler termal potansiyel farkını elektriksel potansiyel (Voltaj) ya da mv değerinde elektriksel potansiyelleri termal potansiyel olarak algılayabilirler. Termokupllar -200 'den 2320 C'ye kadar çeşitli proseslerde yaygın olarak kullanılır. Thermocouples are the most popular temperature sensors. They can measure a wide range of temperatures. The main limitation is accuracy, system errors of less than 1 C can be difficult to achieve. How they work In 1822, an Estonian physician named Thomas Seebeck discovered (accidentally) that the junction between two metals generates a voltage which is a function of temperature. Thermocouples rely on this Seebeck effect. Although almost any two types of metal can be used to make a thermocouple, a number of standard types are used because they possess predictable output voltages and large temperature gradients. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

96 Seebeck effect / Seebeck Etkisi: 1821 de Seebeck, kapalı bir devre iki aynı metalden oluştuğunda ve metallerin farklı sıcaklıklarda iken devreden elektrik akımının aktığını keşfetmiştir. Tel uçlarının bükülerek veya lehimlenerek meydana getirildiğini kabul edelim; bu tellerin birisi bakır, diğeri demir olsun. Bir ucu, oda sıcaklığında tutulurken diğeri daha yüksek bir sıcaklıkta ısıtılırsa sıcak uçta bakırdan demire, soğuk uçta ise demirden bakıra bir akım üretilir. Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

97 Strain-Gage (Gerilim Ölçer) Sensörler Günümüzde teknolojinin ilerlemesi ile sensör teknolojileri de önem kazanmıştır. Bunlardan biri de Strain-Gage sensörleridir. Pek çok ismi vardır. Gerilim ölçerler, gerilim pulu ve şekil değişikliği sensörleridir. Strain-Gage Nedir? Temel çalışma prensibi olarak, direnç değişiminden yararlanarak boy değişimin elektriksel bir sinyal olarak algılanmasına dayanır. Asıl olarak strain gauge'ler özel olarak üretilmiş elektriksel dirençlerdir. Transducer: Bir sinyali istenilen sinyale çeviren etkin devre elemanı. Transduser, elektronikte bir enerji türünü başka bir enerji türüne çeviren aygıttır. Dr. Horizon Gitano-Briggs, Dynamometry and Testing of Internal Combustion Engines Seminar; University Science Malaysia, June Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

98 Reading Text What is the difference between an AC motor and a DC motor? / July 29, 2011 Q&A While both A.C. and D.C. motors serve the same function of converting electrical energy into mechanical energy, they are powered, constructed and controlled differently. 1 The most basic difference is the power source. A.C. motors are powered from alternating current (A.C.) while D.C. motors are powered from direct current (D.C.), such as batteries, D.C. power supplies or an AC-to-DC power converter. D.C wound field motors are constructed with brushes and a commutator, which add to the maintenance, limit the speed and usually reduce the life expectancy of brushed D.C. motors. A.C. induction motors do not use brushes; they are very rugged and have long life expectancies. The final basic difference is speed control. The speed of a D.C. motor is controlled by varying the armature winding s current while the speed of an A.C. motor is controlled by varying the frequency, which is commonly done with an adjustable frequency drive control. 2 1.Saeed Niku. Introduction to Robotics: Analysis, Control, Applications. 2nd ed. John Wiley & Sons, Inc., Page Robert S. Carrow. Electrician s technical reference: Variable frequency drives. Delmar Thomson Learning, Page 45 Published by Ohio Electric Motors: Makine Mühendisliği Yrd. Doç. Dr. Abdullah DEMİR

99 ÖZETLER Reff: Tim Gilles, Diagnosing Engine Performance Problems- Chapter 48, DELMAR, 2012

100 Introduction Engine and ignition system problem results Poor fuel economy High emissions Poor driveability Requirements for engine to run and start properly Sufficient compression Timed spark Fuel and air mixed in the correct ratio

101 Visual Checks Perform visual check when an engine does not start or is running poorly Vacuum line Electrical wires Fuel gauge Believe it or not, sometimes the vehicle is out of gas

102 Ignition System Checks Ignition system must produce a strong spark at the correct moment Checking for spark is quickest thing to do Fuel injection Easier to test compression than check for fuel on port injection engines Sometimes engine starts and runs but one cylinder has a dead misfire Ignition or mechanical problems

103 Engine Performance Testing Fuel problems Dry black soot at exhaust pipe Fuel in the crankcase Air-fuel mixture Can be affected by air leaks Other problems and causes Poor quality fuel blowby and EGR gases cause gummy deposit behind throttle plate Dirty fuel injectors cause driveability problems Plugged fuel filter causes starvation at high rpm

104 Compression Loss Causes of low compression Engine breathing problems Compression leaks Breathing problem causes Carbon buildup around neck of valve Intake restrictions Blocked exhaust Catalytic converters operating for a long period when there is a misfire Become plugged

105 Vacuum Testing Intake manifold vacuum readings Useful in determining engine problems Leaking intake manifold Causes rough idle Low, steady vacuum Check ignition timing Leaking valve Indicated when needle drops at regular intervals Restricted exhaust systems Cause hissing sound Cranking vacuum test Performed to check for internal leaks or incorrect valve timing

106 Other Vacuum Tests V-type engines Can have a vacuum leak Test: pinch off PCV valve hose to the manifold and breather hose to the air cleaner Vacuum at oil filler opening: internal vacuum leak Vacuum signals Can be used with a digital storage oscilloscope Smoke tester Finds vacuum, exhaust, cooling, and oil leaks

107 Compression Problems Compression leak causes Blown head gasket Burned valves Worn or broken piston rings Fast way of locating a weak cylinder Cylinder power balance test Compare performance of cylinders Compression test Pinpoints compression problems

108 Compression Problems (cont'd.) Causes of variations in cylinder Ignition or fuel system Engine vacuum leaks Compression problems Hand-held scan tools Have power balance test capability Compression tester Common piece of equipment

109 Compression Problems (cont'd.) Compression test procedure Twist rubber boots on spark plug cables Before removing spark plugs, blow dirt away from their base Block the throttle in wide-open position Connect remote starter switch Insert compression gauge into spark plug hole and crank engine When cranking, disable ignition system

110 Compression Problems (cont'd.) Interpreting compression test results Check manufacturers tolerance specifications Two cylinders next to each other have low compression: indicates blown head gasket Burned exhaust valves: can cause of one or more cylinders with low compression All cylinders have low compression: incorrect valve timing could be the cause Cylinders with compression higher than specified: can result in carbon buildup

111 Compression Problems (cont'd.) Wet compression test Used if all cylinders show poor results Oil is squirted on each cylinder Running compression test Measures how well the cylinders can draw in air and fuel Running compression should be about 80% of cranking compression

112 Cylinder Leakage Test Used to pinpoint causes of leakage in a combustion chamber Leaks can be pinpointed by listening in different places Oil filter: leaking rings or pistons Air cleaner: leaking intake valve Exhaust: leaking exhaust valve Bubbles in radiator: blown head gasket or crack in head or block

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114 Cylinder Leakage Test (cont'd.) Advantages of leakage test Performed on an engine removed from a vehicle Performance of camshaft will not affect the results Source of leakage pinpointed before engine disassembly

115 Carbon-Related Problems Carbon causes performance problems Increased compression ratio Fuel absorption Blocked air and fuel flow Kinds of deposits Oil based and carbonaceous Carbonaceous deposits Result from fuel Are difficult to remove and cause driveability problems