Makine Mühendisliği

Transkript

Makine Mühendisliği

MARMARA ÜNİVERSİTESİ
TEKNOLOJİ FAKÜLTESİ
Motor Testleri
HAZIRLAYAN:
Yrd. Doç. Dr. Abdullah DEMİR
TYPICAL ENGINE-RELATED COMPLAINTS
Engine Performance Problems
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No-start
Hard starting
Stalling
Misfire
Hesitation
Surging
Lack of power
Ping (spark knock)
Rod Knock
Backfire
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Induction Backfire
Excessive Oil Consumption
Over Heating
Tip-in
WOT
Vapor Lock
Run-On
Intermittent
Diagnostic Tools
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Vacuum gauge
Compression tester
Cylinder leakage tester
Stethoscope
Crankcase pressure tester
Oil pressure gauge
Cooling inspection tools
Spark plug condition
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
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.
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?
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
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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.
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.
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
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.
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.
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: www.lexusownersclub.co.uk
Resim: www.lexusownersclub.co.uk
1 bar equals 14.5 psi
Oil Pressure Test
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This is where the oil pressure sender is
removed from.
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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.
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.
http://www.youfixcars.com/engine-compression-test.html
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.
http://www.youfixcars.com/oil-pressure-testing.html
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
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
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.
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.
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
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
FIGURE 13 A typical handheld cylinder leakage tester.
 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 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.
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.
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.
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.
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.
•
•
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 (800-1000 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.
http://www.freeasestudyguides.com/cylinder-balance-test.html
•
•
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.
http://www.freeasestudyguides.com/cylinder-balance-test.html
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
Oil Pressure Test
Daha önceki slaytlarda anlatıldı
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
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.
Damaged Cylinder Head
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.
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.
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.
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.
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 26-2008
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.
http://makina.ktu.edu.tr/dosyalar/lisans/laboratuv
arfoyleri/lab18.pdf
Motor Deneyleri
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.
http://makina.ktu.edu.tr/dosyalar/lisans/laboratuvarfoyleri/lab18.pdf
Motor
Deneyleri
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.
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.
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.
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.
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.
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.
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.
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.
1.1. 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.
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.
Motor Deneyleri
www.directindustry.com
Motor Deneyleri
www.directindustry.com
Motor Deneyleri
www.dynesystems.com
Motor Deneyleri
www.dynesystems.com
Motor Deneyleri
www.sciencedirect.com
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)
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
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:
Comparison of Dyno Designs
Frictional: Oldest design. Hard to control. Wear on
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
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.
Dynamometer
Automotive Engineering - Powertrain, Chassis System and Vehicle Body Edited by David Yrd.
A. Crolla,
Doç. Dr.2009
Abdullah DEMİR
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 ↑).
Bearings
The body of the dynamometer
must be free to rotate, so it is
supported on bearings.
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.
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.
Load Cell mounts via ball-joint ends
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.
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.
Engine
durability
testing
Motor
dayanıklılık
testi
(Engine durability testing)
B10
olarak
tanımlanan
dayanaklılık
ömrü
(B10
durability
life)
beklenen
ömürdür. B10, 20.000 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
Temel Bazı Kavramlar
Kütlesel ve Hacimsel debi
Dr. M. Azmi AKTACİR-2010-ŞANLIURFA, Harran Üniversitesi Makine Mühendisliği Bölümü
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.
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.
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.
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.
http://elektroteknoloji.com/blog/seebeck-etkisi-nedir/
http://www.engadget.com/2008/10/09/researchers-say-spinseebeck-effect-could-lead-to-new-batterie/
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.
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., 2011. Page 280 ↩
2.Robert S. Carrow. Electrician’s technical reference: Variable frequency drives. Delmar Thomson Learning, 2001. Page 45 ↩
Published by Ohio Electric Motors: http://www.ohioelectricmotors.com/what-is-the-difference-between-an-ac-motor-and-a-dcmotor-673#ixzz2ezsrNvI3
ÖZETLER…
Reff: Tim Gilles, “Diagnosing Engine Performance Problems- Chapter 48”, DELMAR, 2012
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
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
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
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
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
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
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

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
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

 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
 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
 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
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
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
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

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