Sunday, September 19, 2010

Lubrication Oil Meaning Number SEA 20W-50 and other

When you see a W on a viscosity rating it means that this oil viscosity has been tested at a Colder temperature. The numbers without the W are all tested at 210° F or 100° C which is considered an approximation of engine operating temperature. In other words, a SAE 30 motor oil is the same viscosity as a 10w-30 or 5W-30 at 210° (100° C). The difference is when the viscosity is tested at a much colder temperature. For example, a 5W-30 motor oil performs like a SAE 5 motor oil would perform at the cold temperature specified, but still has the SAE 30 viscosity at 210° F (100° C) which is engine operating temperature. This allows the engine to get quick oil flow when it is started cold verses dry running until lubricant either warms up sufficiently or is finally forced through the engine oil system. The advantages of a low W viscosity number is obvious. The quicker the oil flows cold, the less dry running. Less dry running means much less engine wear.
SAE Viscosity Chart (High Temp)
100° C (210° F)
SAE
Viscosity

Kinematic
(cSt)
100° C Min

Kinematic
(cSt)
100° C Max

20 5.6 <9.3
30 9.3 <12.5
40 12.5 <16.3
50 16.3 <21.9
60 21.9 <26.1
Winter or "W" Grades
SAE
Viscosity

Low Temp (°C) Viscosity cP
Kinematic
(cSt)
100° C Min

Cranking
Max

Pumping
Max (NYS)

0W 3,250 @ -30 60,000 @ -40 3.8
5W 3,500 @ -25 60,000 @ -35 3.8
10W 3,500 @ -20 60,000 @ -30 4.1
15W 3,500 @ -15 60,000 @ -25 5.6
20W 4,500 @ -10 60,000 @ -20 5.6
25W 6,000 @ -5 60,000 @ -15 9.3
Obviously, cold temperature or W ratings are tested differently than regular SAE viscosity ratings. Simply put, these tests are done with a different temperature system. There is a scale for the W, or winter viscosity grades and, depending on which grade is selected, testing is done at different temperatures. See the Tables to the right below for more information.
Basically to determine non-winter grade viscosity using a viscometer a measured amount of oil at 100° C is allowed to flow through an orifice and timed. Using a table they determine SAE viscosity based on different ranges. Thicker or heavy viscosity oils will take longer to flow through the orifice in the viscometer and end up in higher number ranges such as SAE 50 or SAE 60 for example. If an oil flows through faster being thinner/lighter then it will wind up in a low number range such as SAE 10 or SAE 20 for example. Occasionally it is possible for an oil to barely fall into one viscosity range. For example, an oil is barely an SAE 30 having a time that puts it on the very low side. Then another oil is timed to be an SAE 20 on the high side not quite breaking into the SAE 30 numbers. Technically speaking these oils will be close to the same viscosity even though one is an SAE 20 and the other an SAE 30. But you have to draw the line somewhere and that's how the SAE system is designed. Another system takes more accurate numbers into account known as cSt abbreviated for centistokes. You'll see these numbers used often for industrial lubricants such as compressor or hydraulic oils. The table at the right, SAE Viscosity Chart (High Temp), shows the equivalents for cSt and SAE viscosity numbers. You'll see the ranges for cSt compared to SAE numbers. An oil that is 9.2 cSt will be nearly the same viscosity as an oil that is 9.3 cSt, yet one is an SAE 20 and the other is an SAE 30. This is why the cSt centistokes numbers more accurately show oil viscosity.
Now if you look at the table labeled Winter or "W" Grades, you can get valuable information on how the W or winter grade viscosities are measured. Basically, as shown by the chart, when the oil is reduced to a colder temperature it is measured for performance factors. If it performs like a SAE 0 motor oil at the colder temperature, then it will receive the SAE 0W viscosity grade. Consequently, if the motor oil performs like a SAE 20 motor oil at the reduced temperatures (the scale varies - see the chart), then it will be a SAE 20W motor oil.
If a motor oil passes the cold temperature or W (winter grade) specification for a SAE 15W and at 210° F (100° C) flows through the viscometer like a SAE 40 motor oil, then the label will read 15W-40. Getting the picture? Consequently, if the motor oil performs like a SAE 5 motor oil on the reduced temperature scale and flows like a SAE 20 at 210° F (100° C), then this motor oil's label will read 5W-20. And so forth and so on!
I can't tell you how many times I have heard someone, usually an auto mechanic, say that they wouldn't use a 5W-30 motor oil because it is, "Too thin." Then they may use a 10W-30 or SAE 30 motor oil. At engine operating temperatures these oils are the same. The only time the 5W-30 oil is "thin" is at cold start up conditions where you need it to be "thin."

Source: http://en.wikipedia.org/wiki/Motor_oil

Saturday, July 17, 2010

ELECTRONIC FUEL INJECTION (EFI)

Electronic Fuel Injection works on the some very basic principle. This system can be divided into three basic sub-system. These are the fuel delivery system, air induction system and the electronic control system.

The Fuel Delivery System:


  • The fuel delivery system consist of the fuel tank, fuel pump, fuel injector, fuel delivery pipe (fuel rail), fuel injector, fuel pressure regulator and fuel return pipe.
  • Fuel is delivered from the tank to the injector by means of an electric fuel pump. The pump is typically located in or near the fuel tank. Contaminants are filtered out by a high capacity in line fuel filter.
  • Fuel is maintained at a constant pressure by means of a fuel pressure regulator. any fuel which is not delivered to the intake manifold by the injector is returned to the tank through a fuel return pipe.
 Air Induction System:

  • The air induction system consists of the air cleaner, air flow meter, throttle valve, air, intake chamber, intake manifold runner, and intake valve.
  • When the throttle valve is opened, air flows through the air cleaner, through the air flow meter, past the throttle valve and through a well tuned intake manifold runner to the intake valve.
  • Air delivered to the engine is a function of driver demand. as the throttle valve is opened further, more air is allowed to enter the engine cylinders.
 Electronic Control System:


  • The electronic control system consists of various engine sensors, electronic control unit (ECU), fuel injector assemblies and related wiring.
  • The ECU determines precisely how much fuel need to delivered by the injector by monitoring the engine sensors.
  • The ECU turn the injectors on for a precise amount of time, referred to as injection pulse width or injection duration. To deliver the proper air/fuel ratio to the engine.

Friday, July 16, 2010

Petrol Engine (Internal Combustion)

A petrol engine (known as a gasoline engine in North Amerika) is an internal combustion engine with spark-ignition, designed to run on petrol (gasoline) and similar volatile fuels.
It differs from a diesel engine in the method of mixing the fuel and air, and in the fact that it uses spark plugs to initiate the combustion process. In a diesel engine, only air is compressed (and therefore heated), and the fuel is injected into the now very hot air at the end of the compression stroke, and self-ignites. In a petrol engine, the fuel and air are usually pre-mixed before compression (although some modern petrol engines now use cylinder-direct petrol injection).
The pre-mixing was formerly done in a carburator, but now (except in the smallest engines) it is done by electronically controlled fuel injection. Petrol engines run at higher speeds than Diesels partially due to their lighter pistons, conrods & crankshaft (as a result of lower compression ratios) & due to petrol burning faster than diesel. However the lower compression ratios of a petrol engine gives a lower efficiency than a diesel engine.


Petrol engines may run on the four-stroke cycle or the two-stroke cycle

Two Stroke:


1. Intake
2. Compression
3. Power
4. Exhaust




Four Stroke:

Sunday, July 4, 2010

Spark Plug

A spark plug is an electrical device that fits into the cylinder head of some internal combustion engine and ignites compressed fuels as such aerosol, gasoline, ethanol and liquefied petroleum gas by means of an electric spark.


Spark plugs have an insulated central electrode which is connected by a heavily insulated wire to an ignition coil or magneto circuit on the outside, forming, with a grounded terminal on the base of the plug, a spark gap inside the cylinder. Picture below shows part of spark plug:-


Diagram 1: Single-ground spark plug


How Do You Adjust Spark Plug Gap?

  1. Check the owner's manual for your car (or any appliance with spark plugs) to find out the recommended gap setting.
  2. Use a gap tool to check the gap of the spark plug. Slip the tool between the ground electrode and center electrode. The gap tool should fit snugly at the recommended gap width indicated on the tool
  3. Push the tool between the electrodes a few times to ensure proper gap. If the gap is too wide, push the ground electrode firmly against a flat surface to narrow the gap and then check again with the gap tool.

 

Resource: e-How, NGK SPARK PLUG


  • Step 4
    Use a gap tool to check the gap of the spark plug. Slip the tool between the ground electrode and center electrode. The gap tool should fit snugly at the recommended gap width indicated on the tool.

  • Step 5
    Push the tool between the electrodes a few times to ensure proper gap. If the gap is too wide, push the ground electrode firmly against a flat surface to narrow the gap and then check again with the gap tool.