Serving the Gainesville and Hawthorne Florida Area
Engine Compression: Compression tests
An engine with low compression will make an uneven
"da-dadada,WHEEE!,da-dadada,da-dadada,WHEEE!"
sound when you engage the starter.
Compression which is too low can result in poor running, high emissions, and bad fuel mileage.
Low compression can be caused by cylinder head problems or bad piston rings (or apex seals in rotarys).
A more accurate test is the leakdown test. This blows compressed air into each cylinder. Not only can the percentage of compression loss be measured, you can determine the cause of the low compression by seeing where the air leaks out. Bad rings will leak into the crankcase and you can hear the air blow out when you remove the oil filler cap. Cars with a bad exhaust valve will blow out the exhaust pipe, and a bad intake valve will blow back through the air cleaner.
WHAT IS COMPRESSION RATIO?
The compression ratio of an engine is determined like this: the volume of the combustion chamber with the piston all the way down at the bottom of the cylinder (bottom dead center) is divided by the volume of the combustion chamber with the piston all the way at the top of the cylinder (top dead center). The lowest compression ratios are around 8 to 1. The highest stock compression ratio (found on 60's muscle cars) is around 12 to 1. A higher compression ratio makes more horsepower. It can also make you burn high octane, premium gas, even racing fuel. Few modern cars exceed 10 to 1 compression ratios.
Here's a video on how to do a compression test
A
ABS: Anti-Lock Brake Systems
ADVANCE: Car ignition timing
ALTERNATORS and Car Battery
AUTOMATIC TRANSMISSIONS
B
BAD CAR DESIGNS
Bad Drivers: How NOT to drive
BATTERIES: Auto, Car or Truck
BELTS AND HOSES
BEARINGS
BODY AND BUMPER REPAIRS
BRAKE REPAIRS: Car or Truck
C
Car Washing and Care
CARBURETORS:Car & Truck
CHECK ENGINE LIGHT
CLEANING: Engine Cleaning
CLUTCH REPAIRS: Car & Truck
COIL (IGNITION)
COMPRESSION: Car Engine
COMPUTER CAR CONTROLS
CRUISE CONTROL / LANE GUARD
CV JOINT OR CV AXLES
D
DISTRIBUTORS (IGNITION)
E
ELECTRIC WIRING REPAIR
ENGINES: Car & Truck
ENGINE CLEANING
EXPANSION PLUGS
F
FILTERS: OIL, AIR, ETC.
Flywheels, dual mass flywheels
FREEZE PLUGS
FUEL AIR MIXTURE
FUEL INJECTION: Car & Truck
FUEL PUMPS: Car & Truck
G
GAGES AND "IDIOT LIGHTS"
GASKETS AND SEALS
GLASS: WINDOWS AND WINDSHIELDS
H
HEADS & HEAD GASKET
HOSES AND BELTS
I
"IDIOT LIGHTS" AND GAGES
IGNITION COIL
IGNITION TIMING: Car & Truck
J
AUTO JACKS: lifting cars safely
K
L
LEAN "Car runs lean"
LIGHTS: WARNING OR "IDIOT LIGHTS"
Limp Home Mode
M
MIL Light
MANUAL TRANSMISSIONS
N
NO START: Car Won't Start
O
OIL CHANGES
OIL: What's right for your car?
OIL LIGHT ON OR GAGE LOW
P
PCV Valve
Q
R
RADIATORS: Car and Truck
RICH: Car runs rich
S
SEALS AND GASKETS
SELF DRIVING CARS / CRUISE
SERVICE ENGINE SOON LIGHT
SPARK PLUGS
STARTERS: Auto, Truck
T
THERMOSTATS
TIMING: IGNITION TIMING
TIMING BELT & TIMING CHAIN
TIRE REPAIR
TRANSMISSIONS: AUTOMATIC
TRANSMISSIONS: MANUAL
U
V
VACUUM ADVANCE
WARNING LIGHTS OR "IDIOT LIGHTS"
Car Washing and Care
W
Washing and cleaning your car
WATER PUMP REPAIR
WINDOWS AND WINDSHIELDS
WIRING REPAIR
X
Y
Z
RETURN TO THE ECONOMECHANIX HOME PAGE
Thank you for visiting the ECONOMECHANIX WEB SITE. Please feel free to comment.