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If your Mfgr. says:

That motor's 7 years old.
Part is no longer available.
We lose $$ on service!
EPA made me do it!
Parts at central warehouse, you'll get them next month.
We don't make parts for those.
We only do warranty work.
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ENGINE TECHNOLOGIES MADE EASY!

HERE IS HOW IT WORKS

The most common internal combustion engines of today can be defined as either four-stroke or two-stroke cycle. Two-stroke or four-stroke refers to the number of strokes the piston makes in the cylinder to complete one power cycle. A stroke is the movement of the piston in one direction, moving the piston from the top to the bottom of the cylinder is one stroke. A running internal combustion engine continually repeats a power cycle called: intake, compression, power and exhaust. Your automobile or stern drive engine is most likely a four stroke design. The majority of existing outboard motors use two stroke technology. However the current movement in emissions regulations is pushing the design of current outboards towards the 4 stroke and direct injection two stroke design. Efforts to build a 4 stroke outboard in the past have been many and varied, mostly unsuccessful as the design technology and precision production that can be achieved today were impossible to achieve then. Resulting motors were bulky and unreliable. Those motors that were viable were for the most part rejected by the boating public.


Section Three

DIRECT FUEL INJECTION or DFI

is as the name implies, a process of injecting a fuel charge directly into the combustion chamber. Not to be confused with electronic fuel injection (EFI) or programmed fuel injection into the intake passages of a four stroke.

 

 

DIRECT FUEL INJECTION
DIRECT FUEL INJECTION COMPRESSION IGNITION
COMPRESSION & IGNITION


DIRECT FUEL INJECTION
DFI POWER EXHAUST
POWER & EXHAUST

 

Up Stroke - Intake and Compression

On the up stroke the top side of the piston is compressing only air in the cylinder. At the same time the bottom side of the piston is pulls more fresh air into the crankcase past a one way reed valve. Near the top of the stroke, the direct injector sprays a plume of fuel directly into the cylinder after the intake and exhaust ports are closed. This is accomplished in several ways depending on the engine manufacturer, all serve the same purpose and have more or less the same components. That fuel/air mixture is ignited by the spark plug. The rapidly burning fuel expands and begins forcing the piston down.

 

 

 

 

Down Stroke - Power and Exhaust

On the down "power" stroke the piston is forced toward the crankcase. As it continues its downward travel it starts first to uncover the exhaust ports. Exhaust gases begin to rush out of the cylinder. The intake ports then uncover; fresh air compressed on the downstroke is then forced into the cylinder and continues to push the remaining exhaust out of the cylinder. Since there was only air in the crankcase the cylinder is cleaned very effectively and readied for the next injection of fuel.

More on the subject of Direct Injection, Electronic injection as well as an overview of the various systems coming soon. Mastertech will attempt to unravel the claims made by the motor manufacturers. Stay tuned!!

Back to TWO STROKE ENGINES, PAGE 2

 
 

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DISCLAIMER

The information provided on these pages is correct to the best of my knowledge, however the MasterTech makes no warranty, express or implied, regarding the use of, results of, or liability created from, application of this data. This information is disseminated in good faith, however MasterTech assumes NO LIABILITY whatsoever in regard to this service. The information, software, products, and services published on this web site may include inaccuracies or typographical errors. Changes are periodically added to the information herein. Mastertech may make improvements to this site at any time. Parts ordered from this website may or may not be in dealer stock at the time of order. Thank you for reading.