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Advantages of Direct Fuel Injection
|Author||Topic: Advantages of Direct Fuel Injection|
posted 12-12-2009 05:10 PM ET (US)
In an ongoing discussion with a friend regarding DFI marine injectors I could use some help to a few questions. Is the main advantage to direct fuel injection marine injectors like Yamaha HPDI, Mercury OptiMax, and Evinrude E-TEC in the cleaner emissions? Seems like the former EFI versions of these outboards had the all the advantages of DFI, but without the higher Three-Star rating.
Second, is the E-TEC injector unique from the other DFI outboards in that it doesn't need an onboard compressor for high pressure like the the HPDI and OptiMax? Does the E-TEC injector design by itself atomize the fuel and also create the pressure needed without a high pressure fuel rail or air pressure?
Third. How are these DFI two strokes lubercating their critical crank, connecting rods and other bearing surfaces since there is no crankcase oil or crankcase or sump or oil pump? I understand how they are lubericated in a carb two stroke, but in thinking through the DFI process I am lost in how that critical oiling takes place
posted 12-12-2009 08:59 PM ET (US)
Standard EFI does not work as well on a 2-stroke because without valves both intake and exhaust port are open together for a short time allowing un-burned fuel to escape. EFI gets a better fuel mixture for the conditions, but fuel is still wasted as it was with the carbs and that un-burned fuel leads to worse emissions and economy. 4-strokes on the other hand do not suffer from this issue and standard EFI works well.
DFI solves this nicely for a 2-stroke because fuel is not injected until after the exhaust port closes, prevent -unburned waste. In essence the DFI injector becomes a intake valve for fuel. The higher the pressure this injector is the later in the compression stroke fuel can be injected.
E-TEC's injectors a similar to a speaker voice coil and can be finely controlled by a computer and produce significant pressure right in the injector, forgoing a high pressure pump before them as with other systems.
The E-TEC and other oil-injected 2-strokes only have intake air pass through the crank case but lubricate by injecting oil directly at various points where it is needed, this oil still ends up getting combusted eventually since the crank is not sealed, but much less is needed, so much less is burned.
posted 12-12-2009 09:24 PM ET (US)
One other interesting note about 2-strokes that seems to go unused anymore is that that can run in reverse nearly as well as forward.
The old Mercury Mark 75 actually did this, in order to reverse the engine shut down and the starter re-started the engine in reverse. I don't think this worked too well because of the lag time when you quickly need to shift into reverse docking.
You would think and E-TEC with it's ability to quickly start in one revolution could use this system, allowing for a simpler smaller and lighter lower unit with no reverse gear.
posted 12-12-2009 10:28 PM ET (US)
I wanted to clarify something mentioned above:
"The E-TEC and other oil-injected 2-strokes only have intake air pass through the crank case but lubricate by injecting oil directly at various points where it is needed, this oil still ends up getting combusted eventually since the crank is not sealed, but much less is needed, so much less is burned."
I didn't know this. Is this the Evinrude X-100 oil that is being injected on the various points? Does it drain and collect anywhere down below in a sump of some kind and recirculated?
Also, in the E-TEC, what is the ratio of oil/gas that is injected into the cylinders? From what I hear from E-TEC owners they seem to use very little oil in comparison to older systems
posted 12-12-2009 11:17 PM ET (US)
The E-TEC can either use standard tw3 or xd-100 oil. With xd-100 it will use less oil, therefore higher ratio than tw3.
The oil does not collect or recirculate, it bascially ends up in the intake air and then gets burnt, just like a normal old 2-stroke, but since it's injected directly on the parts that need it most, much less is used.
The ratio is not fixed and is based on RPM I believe, and on the E-TEC with xd-100 it is around 300:1 at idle but ramps up as rpm goes up.
posted 12-12-2009 11:40 PM ET (US)
In an E-TEC engine the gasoline is sent to the injectors without mixing it with oil. As already described, the oil is pumped to a distribution manifold and fed to various points in the engine where it provides lubrication. For example, in a 225-HP E-TEC the oil distribution system is composed of the following components in this order (and with hoses connecting all of them):
The primary manifold feeds oil to a crankcase fitting for each cylinder, and to the secondary distribution manifold. The secondary distribution manifold feeds oil to a cylinder fitting for each cylinder.
The oil injector pump is controlled by the engine management module, and pumps oil in proportion to the engine speed and other factors, such as hours of running time, winterization program, grade of oil being used, and so on.
Also, there is recirculation of the oil. In general the oil accumulates in the lower cylinders. From there it is suctioned out and fed back to upper cylinders and the upper main crankcase bearing, controlled by one-way check valves.
The amount of oil used is in proportion to the engine speed. Since the amount of gasoline used is also in proportion to the engine speed, you might think the oil was being mixed with the gasoline, but it is not. If you really pour the coals to an E-TEC, the engine management module will correspondingly increase the oil flow rate. If you idle around all day, the E-TEC is very stingy with oil. The overall ratio of oil used to gasoline used tends to be somewhere between 1:50 and 1:100, and depends on two principal factors, the grade of oil used and the engine speeds run.
posted 12-13-2009 09:49 AM ET (US)
The E-TEC injector is different from many other injectors in its electromagnetic arrangement. Most fuel injectors use a fixed coil to create an electromagnetic field. When movement in the injector is needed, a current is fed to the coil, creating a magnetic field. The field attracts or repels a magnetic rod, creating the movement needed to inject the fuel. The coil is stationary, the magnet moves.
An E-TEC injector reverses the arrangement. A large stationary permanent magnet is used to create a stationary magnetic field. A coil of wire, like a voice coil in a dynamic loudspeaker, is made to move in this field by passing current through it. The magnet is stationary, the coil moves.
The weight of a coil of wire is less than the weight of the magnetic material in a conventional injector. The E-TEC plunger is therefore light and able to be accelerated faster. The strength of the permanent magnet's field is much greater than the magnetic plunger in a conventional injector, and the field is permanent. It does not have to build up when current flows, or collapse when current stops. The force developed is proportional to the current in the wire and the strength of the magnetic field. A moderate current in a very strong field can produce plenty of force.
The electrical circuitry controlling the movement of the E-TEC injector is also quite interesting (and covered by a patent). A coil moving in a magnetic field generates electrical current, and this current is used to help run the injector. The injector can also be slowed down on its return trip to create a soft landing, reducing the noise generated.
Controlling an E-TEC injector requires some sophisticated electronic circuitry, but these days the cost of sophisticated electronic circuitry is extremely low, perhaps just a few pennies for hundreds of transistors. Electronic circuits can operate at very high speeds. The speed of operation of a fuel injector is really quite low. If we consider a six-cylinder engine operating at 6,000-RPM, this implies that an individual cylinder will perform 6,000-cycles per minute. The frequency is thus:
6,000-cycles/1-minute x 1-minute/60-seconds = 100 cycles/second
Experience with loudspeakers has shown us that a magnet and voice coil arrangement can operate at frequencies 100-times greater ( e.g., 10,000-Hz) than this, so even at maximum engine speed the E-TEC voice coil injector is loafing along.
posted 12-13-2009 12:23 PM ET (US)
Let me dispel some incorrect notions presented above about fuel injectors used in outboard motors. The fuel injection technique used in the Mercury OptiMax engine is not Mercury's, but Orbital's. The model name for the engine is OptiMax but the name for the injection process is the Orbital Combustion Process. For more information on the Orbital Combustion Process (OCP), see
Mercury did not develop this system. They license it from Orbital. They also buy the injectors from Orbital's injector manufacturing subsidiary. The OCP injectors are made by Synerject, a joint subsidiary of Orbital and Continental. Continental is a conglomerate of automotive related manufacturers that acquired VDO-Siemens, who was a global manufacturer of fuel injectors.
See these resources for more on Synerject and Continental:
Curiously, Synerject purchased a manufacturing facility from Bombardier Recreational Products in Wisconsin, where the E-TEC injector was being manufactured. That facility still makes the E-TEC injector, but Synerject now manufactures it for Bombardier. Bombardier holds the patents and intellectual property of the E-TEC and Ficht injector systems. Bombardier bought Ficht from its German inventor and namesake.
On the topic of the E-TEC injector and how it differs, in most conventional injectors the forward motion to deliver the fuel is created by the electromagnetic force, but the reverse motion is from the expansion of a spring. The force of the spring has to be overcome during the downward motion, and the spring expansion controls the speed of the injector during the retraction or upward movement. In contrast, in an E-TEC injector the current in the voice coil can be reversed, resulting in a very fast reversal of the injector, and again the light weight produces better acceleration. I believe there is a small spring to be overcome in the E-TEC, but it is just to hold the injector closed when no power is applied, and the forward motion does not have much spring force to overcome. In a conventional injector the spring force is higher because it must be able to quickly close the injector.
The timing of the injector opening and closing is important to the combustion process and controlling emissions, I imagine, but, again, I am not an automotive engine designer, so more investigation might be needed.
I don't have any basis to comment about the high speed hydrodynamics of fuel behavior from an injector and how well the various designs can create a combustible fuel mixture in the combustion chamber, but, as you observed, apparently the OCP technique requires that pressurized air be provided to aid the injector in dispersing the fuel while the E-TEC does not. About all I know about HPDI is that HP is an acronym for high pressure, and the fuel is raised to a high pressure. In this way the injector acts like a gate valve, and the pressure of the fuel entering the combustion chamber comes from a high-pressure fuel pump and distribution system, not from the force of the injector. The E-TEC, in contrast, distributes the fuel at a modest pressure using rubber hoses and a moderate pressure fuel pump. The stroke of the injector imparts the pressure to the fuel.
The OCP technique actually uses two injectors for each cylinder. On this I am a little fuzzy, but apparently one injector injects air (under pressure) and another injects fuel (under pressure) and at some point they mix. The obvious disadvantage to this systems is twice as many injectors are needed per cylinder and two rail distribution systems are needed per engine (or four for a V-block engine), one for fuel and one for air. The OCP system also robs power from the engine to run the air compressor (usually mechanically from a belt drive), to run the high pressure fuel pump (usually electrical from the engine alternator), and needs double or more electrical power needed to run twice as many injectors. As a result, the OCP technique seems to be more common in higher power motors, and about 75-HP seems to be the lower limit of its application to Mercury outboard motors. The E-TEC technique has already been used from 25-HP to 300-HP with the same fundamental design, and I believe the same fuel injectors. The electrical power needed in an E-TEC engine is low and the engine can easily self-generate all the power. E-TEC engines can be pull started and run without a battery. As far as I know, there is no Mercury OptiMax that can be pull started (as the air pressure needs to build up) nor can they run without a battery (as the electrical load is high during starting and sufficient power cannot be generated by the engine alone until the engine speeds comes up to about 1,500-RPM).
The E-TEC injector was refined in c.2008 and has a new design, called the BIP or ball-in-plunger E-TEC injector. Bombardier have also carried their E-TEC technology to other applications, include two-cycle and four-cycle engines on snow mobiles and other engines.
OCP seems to have withered on the vine as an engine technology, and other than Mercury (and Tohatsu) with outboard motors, I do not think there is widespread application of it. HPDI is now reduced to application on one model of Yamaha outboard, so I think you can say it is a niche technology. E-TEC seems to be growing in application among Bombardier division, but I do not believe it has been licensed to anyone else.
E-TEC is somewhat unique in being developed and owned by the engine maker, Bombardier Recreational Products, as most of the other fuel injector technology is developed by companies that specialize in fuel injectors. I think Continental nee VDO-Siemens is probably the leader.
posted 12-13-2009 12:51 PM ET (US)
Another striking and very unique difference in the E-TEC injector from every other fuel injector (at least that I have ever heard mentioned) is the use of individualize component characterization to provide ultra-fine tuning. Every E-TEC injector is tested and its fuel delivery characteristics described in a series of coefficients for a polynomial equation that models the fuel delivery. Each E-TEC injector carries these coefficients with it, and when installed in a particular engine, the engine management module is informed of these values. An algorithm in the engine management module uses these values to compute the timing and duration of the control signals that operate the injector so its fuel deliver is consistent with the ideal injector profile.
The engine management module (EMM) also modifies the fuel delivery on a per cylinder basis as needed to account for various engine speeds and loads. For example, upper cylinders which tend to run hotter can be given richer fuel mixtures in certain conditions to avoid problems with pre-ignition. The EMM can also compensate for wear in the injector as it ages; another algorithm corrects for that. There is a lot of engineering built into the EMM.
I don't know exactly what goes on in an OptiMax engine with its OCP process. Mercury engine controllers are developed by Moto-Tron. The history of Moto-Tron is a bit hazy to me at the moment. I think at one point they were an independent company, then later bought out by Brunswick. At the moment they appear to be a division of another company, Woodward, an independent company in Colorado that specializes in control systems. I assume Brunswick sold them off. After George Buckley, Ph.D Electrical Engineering, left as CEO of Brunswick, the Brunswick corporation's interest in owning high-tech electronic companies seemed to decline and they sold off assets like Moto-Tron and NAVMAN and bought great brand name fiberglass boat companies like Sea-Pro and Palmetto instead.
posted 12-13-2009 01:45 PM ET (US)
To correct jimh. There is a small amont of oil being introduced to the fuel supply ahead of the fuel pump. The purpose is to keep the injectors clean and provide the needed top end lubrication. It is metered through a check valve as an extra line from the oil distribution manifold.
The powerhead has oil recirculation lines running from various points near the main bearings. One line rins to the atmospheric area ahead of the throttle butterflies.
All recirculation oil lines have ONE WAY check valves,while oil delivery lines to the crankcase are flow through.
posted 12-13-2009 08:42 PM ET (US)
Does the E-tec actually "recirculate" oil? From what I understood it is a one-way "circulation" where the oil ends up combusted as it must since new oil is coming in behind it.
Just semantics, but recirculation would denote reuse of oil, the E-tec like most 2-strokes is a total loss lubrication system right?
Oil is constantly pumped in, and must be removed at an equal rate, or it would collect and fill the engine.
It is like a sink with a running faucet and an open drain, if the drain drain is smaller than the faucet some of the water will recirculate for a time in the sink until it overflows, if they are equal in size the water will pass with minimal recirculation.
Besides why would you want to recirculate old oil when you have new oil coming in, it would be preferable from an engineering standpoint to use the new oil instead.
posted 12-14-2009 10:07 AM ET (US)
Re mixing of oil and fuel in an E-TEC: The oil system diagram for the 2008 225-HP E-TEC shows no oil distribution to any connection with the gasoline fuel line. I cannot speak for all prior models, all prior years, all power ranges. It may very well be that on some model, some year, some power range that some oil from the distribution pump--a very small fraction--was mixed with the fuel so that the fuel contained oil and gasoline in a ratio of something like 1:350. I do not think this is done in current models.
Rre-circulation has been used in two-cycle engines for decades. Most all OMC engine have re-circulation systems. It is by no means anything unique or specific to the E-TEC. On a classic two-cycle the recirculation is mainly gasoline and oil mixed. On an E-TEC the re-circulation would likely be mainly oil. Recirculation is like a postive crankcase ventilation system on a four-cycle engine.
In an E-TEC the oil that is used up goes into the combustion chamber and is burned. Again, this is nothing new--all two-cycle engines do this.
posted 12-14-2009 11:11 AM ET (US)
The prior generation Ficht DFI system recirculated oil between the motor and the oil tank. The E-TEC system does not do that.
On the 225 HP Ficht DFI system, in the tube connected between the outlet side the fuel lift pump and the fuel filter there is a tee that is connected to the oil pump to provide the incoming fuel with a little bit of oil. I don't see this in the parts diagrams for the 225 E-TEC.
posted 12-14-2009 12:49 PM ET (US)
I believe the e-tech is only supposed to use XD-50 oil or XD-100,...not the regular TCW3...[ XD 30 ].
The engine [ e-tech ] "MUST" be programed according to what oil you choose to run,[ either XD 50 or XD 100 ].
It's my under standing the regular TCW3 can only be used in an emergency.
All though some people concider everyday an emergency, & use the cheapest TCW3 oil they can find, than they come on all the boards, & say the engine is junk, because it broke down.
posted 12-14-2009 01:37 PM ET (US)
No Sal they can be run on XD30. My neighbor was doing it and I looked it up online at Evinrude and was amazed to see it.
|L H G||
posted 12-14-2009 02:04 PM ET (US)
In an Optimax or E-tec, how does the oil that gets burned (as all the oil you pour into the reservoir does) actually get into the combustion chamber? Why does a 2-stroke DFI burn more oil than a 4-stroke? When a worn out 4-stroke burns some oil, it's considered high emissions.
posted 12-14-2009 02:33 PM ET (US)
I guess it is just a semantic issue.
What you refer to as a re-cirulation system I knew as a scavaging system.
It picks up the minimal amount of oil that has not made it's way to the combustion chamber and gets it to the combustion chamber. After all you don't want old partially burnt oil lubricating your components or filling the engine.
Either way the E-tec does not reuse oil, all that is injected is combusted as in any 2-stroke.
As far as modern 2-strokes producing low emissions while burning oil vs a 4-stroke, has to do with the oil itself, normal motor oil is not designed to burn clean, 2-stroke oil is made to burn much cleaner, its one of the primary difference between the two types of oil. That and less of it is used in a oil injected 2-stroke, plus more complete burning of oil and fuel in a DFI.
posted 12-14-2009 04:50 PM ET (US)
Nick, thanks for clearing that up for me on the e-tech.
My 200 hp Evinrude FICHT can only use XD 50 or XD 100, & only XD 30 in an emergency.
My engine has 2000 hours on it now, & was running pretty rough between 3000 & 4000 rpms, so I squirted a can of Sea Foam through the 6 air intakes [ while at idle ] , another can in my Racor [ at idle ], pulled the plugs & squirted another can in the spark plug holes & turned it over by hand & let it sit over night.
Oh boy, I am amazed someone didn't call the fire dept, because I couldn't see a 747 if it were parked 5 ft away.
The engine likes to over rev when she has that much Sea Foam in her, so I had to keep shutting her down about 6 - 7 times.
I put new plugs in.
This engine runs better now, than ever before, absolutely smooth as glass at all rpms.
Really amazing what that stuff [ Sea Foam ] can do.
posted 12-14-2009 05:17 PM ET (US)
LHG Q1: In an Optimax or E-tec, how does the oil that gets burned (as all the oil you pour into the reservoir does) actually get into the combustion chamber?
Comes in with the air stream.
LHG Q2: Why does a 2-stroke DFI burn more oil than a 4-stroke? When a worn out 4-stroke burns some oil, it's considered high emissions. (Assuming this 2nd part is a question).
The oiling system is not closed as it is in the 4-stroke. The oil in the crankcase can and does migrate into the combustion chamber. The emissions certification of an Optimax or E-TEC takes the lubrication oil burned into account. The 4-stroke emissions certification does not.
posted 12-14-2009 05:28 PM ET (US)
Here's some information on the HPDI oil delivery system from service manual covering my 2003 150HPDI. There's not much information in manual or found online.
Standard engine mounted oil pump with throttle linkage to control mixture. Injects oil at engine side of intake manifold. One oil fitting for each cylinders intake. Recirculation unknown.
Electric oil pump, pumps oil to vapor separator, mixes oil with fuel prior to high pressure pump. Mixture or if variable unknown. Probably uses small amount to lubricate HP pump and injectors.
posted 12-14-2009 09:14 PM ET (US)
To correct Whaler Auctions: there is no connection between the oil distribution system and the gasoline fuel rail on a 2008 E-TEC 200, 225, or 250-HP engine. At least, it is not shown in the service manual. The oil hose routing has a feed to every cylinder. On cylinder #2 the upper cylinder on the port side of the engine, the oil distribution hose joins a T-fitting at the cylinder. The oil recirculation hose from lower in the engine also joins this T-fitting.
The oil hose distribution never connects to the gasoline hose distribution. Refer to diagram 003985 in the service manual, titled FUEL SYSTEM HOSE DISTRIBUTION. There is no connect of any oil supply or any recirculation hose to the fuel distribution system. A small amount of oil is NOT introduced ahead of the fuel pump. At least not on this engine, or at least not as the service manual indicates.
1 -- Fuel supply from boat fuel system
posted 12-14-2009 10:26 PM ET (US)
On the prior generation Ficht DFI, there is a tee fitting in the fuel hose going to the inlet (suction) side of the fuel lift pump (2). I mistated earlier that the tee was between the pump and the filter. That tee is connected to the oil pump.
One other notable difference between the Ficht and the E-TEC is that the injectors in the Ficht are fed fuel in parallel from a feed manifold and extra fuel is drained from the injectors in parallel to a return manifold. In other words, each fuel injector has its own fuel loop between the inlet and return manifolds. In contrast, the E-TEC injectors are fed and drained in series. Instead of six loops, there are only two loops with three injectors in each loop. This requires much less tubing.
posted 12-14-2009 10:54 PM ET (US)
Is the fuel hose diagram you posted from the service manual? Do you have a similar diagram showing the oil routing you could post? Thanks.
posted 12-15-2009 12:11 AM ET (US)
posted 12-15-2009 12:49 AM ET (US)
Will you please post the oil flow diagram? Now that we know you have it. thanks.
posted 12-15-2009 01:31 AM ET (US)
Be aware that oil flow diagrams are different for the various E-TEC engine sizes and sometimes vary by model year.
A flow diagram is only accurate for the specific engine model and year for which it is intended.
posted 12-15-2009 04:16 PM ET (US)
Understand a diagram may be specific to only one year and model. That was my reasoning when adding my reply on the HPDI system. Often times though a diagram may be specific for many years and models.
Irregardless it's always a good idea to identify year and model the information is known to be specific to. The diagrams are also of interest to many to see the various methods employed.
posted 12-15-2009 04:29 PM ET (US)
So which particular model and year E-TEC are you interested in seeing the oil diagram?
posted 12-15-2009 09:39 PM ET (US)
2008 E-TEC 200, 225, or 250-HP would be good to see since much of the discussion has concerned them and the fuel diagram has been posted. Thanks.
posted 12-15-2009 11:16 PM ET (US)
This is a trick, right? You're trying to get us to post the entire contents of the E-TEC service manual on-line so you can copy it. We're on to you.
posted 12-16-2009 01:02 AM ET (US)
The copies will be sold to the N. Koreans.
|L H G||
posted 12-16-2009 04:12 PM ET (US)
Compared to the traditional oil injection systems of OMC, Mercury and Yamaha, how reliable is a complicated system like that? Sure seems like a lot of yellow hoses, oil line connections, filter, pump and manifold components that could fail and blow the engine.
posted 12-16-2009 05:52 PM ET (US)
I am going to withhold comment about the proposed comparison (of the E-TEC V6) to the oiling systems of Mercury and Yamaha until I see their oil routing distribution pictorial diagrams.
posted 12-16-2009 06:20 PM ET (US)
Yamaha and Mercury DFI outboards don't have the rear manifold. Otherwise, they have the same concept of a main oil manifold with six oil tubes running out of that to the intake manifold or engine block. Thus, unlike the E-TEC, the Yamaha and Mercury DFI outboards do not appear to have any means for providing oil directly to the cylinder sleeves.
posted 12-16-2009 10:11 PM ET (US)
If simpler wins, then we all would be buying 1930's outboard motors.
posted 12-16-2009 11:01 PM ET (US)
Does the manual or Evinrude better describe the crankcase portion of the oil system? Does it just inject the oil into the individual cylinder intake airstream at the manifold or is there a more complex system?
Is there a better description of the sleeve lubrication? How it's designed to work? Are the fittings all located on the upper cylinder as you described the #2 having the t-fitting to recirculation hose?
posted 12-17-2009 12:05 AM ET (US)
I don't know the details of the fittings. I posted the diagrams to provide evidence for my statement the oil and gasoline distribution systems are separate. Another reader indicated my statement was incorrect, so I though it reasonable to demonstrate the information on which I based my statement. I posted the gasoline distribution diagram which showed no connection to the oil distribution. Then I posted the oil distribution diagram which showed no connection to the gasoline distribution. As I have said already, it may very well be that on some model in some model year the E-TEC might mix some oil into the gasoline. But they appear to not do it on the model (2008 V6 200 through 250-HP) that I am using as a basis for describing how a direct-injection two cycle engine works and what its advantages are compared to other types of two-cycle engine.
Regarding the notion that oil mixed in the fuel and they carried through the fuel induction path being a better approach to providing lubrication (apparently on the basis that it is simpler to implement), I don't understand how the oil being carried along with the fuel can know where precisely it should go to lubricate the engine. With the E-TEC the engine designers have provided a distribution system where the fresh new oil is delivered to 12 places in the engine. In addition, because there is no gasoline in the crankcase, the lubricating oil is not continually being diluted and washed away by the solvent effect of the gasoline. I mention this explicitly because apparently some critics of the direct-injection engine do not realize the advantage provided by this type of lubricating system. The goal on all lubrication systems is to deliver oil to the areas that need oil the most. I imagine that is what BRP has done in the E-TEC.
As for comparisons to other direct-injection engines, we could get some hose diagrams of these engines, say an Optimax, and see how the fuel hoses, air hoses, and oil hoses are routed. We could see how they compare.
Re the terms recirculation and scavenging and which is preferred, I have used recirculation because that is the term BRP uses in their technical literature to describe the hoses that recirculate the oil. The term scavaging seems to be used more often as a description of what occurs in the combustion chamber. As already mentioned, all reasonably modern two-cycle engines also have recirculation hoses to move oil (or any liquid that has come out of suspension in the air stream, which in conventional two-cycle engines could be a mixture of oil and gasoline) to other places that has collected in low areas of the fuel induction path.
posted 12-17-2009 11:12 AM ET (US)
Perhaps a diagram of the re-circulating system would help complete the path of oil flow through the engine in relation to the fuel flow?
posted 12-18-2009 02:35 AM ET (US)
Re-circulation is not a technique of direct injection. As I mentioned already, at least twice I think, re-circulation is used in two-cycle engines of all kinds. Re-circulation is also used in four-cycle engines, where it is called positive crankcase ventilation. The technique in a four-cycle engine was probably adapted from the wide use in two-cycle engines. I don't see the point of publishing more hose diagrams for a particular E-TEC. They really do not have anything to do with direct fuel injection techniques.
posted 12-18-2009 01:42 PM ET (US)
I would disagree that PCV is the same as oil re-circulation or savaging, they serve two entirely different purposes.
In a 4-stroke PCV is NOT designed to pickup oil, instead it is designed vent combustion gases that make it by the rings into the crank building up pressure that must be relieved. While some small amount of oil makes it through a PCV, it is designed to minimize oil pickup to prevent burning oil fouling emissions more than necessary.
2-strokes have an open crank for intake air and therefore have no need for a PCV, however savaging systems are there to remove as much oil as possible that collects and has not burned so that it can be burned, this is the exact opposite goal of a PCV.
Lastly oil injection is not a function of DFI either and present on no DFI 2-strokes, yet you choose to post pics of that system. I simply thought it would be help to get a complete picture the oil circulation system in the E-tec from injection to combustion since that was central to the discussion and debate. Too bad you disagree.
posted 12-18-2009 01:44 PM ET (US)
Correction "Lastly oil injection is not a function of DFI either and present on no DFI 2-strokes"
Should read "Lastly oil injection is not a function of DFI either and present on some non-DFI 2-strokes"
posted 12-18-2009 01:58 PM ET (US)
PCV is positive crankcase ventilation. It allows not only gases and pressure to escape but also moisture. When your PCV valve goes south you can usually tell by the milky oil on your oil cap. If it goes south the other way it can force oil back into your induction system and cause your engine to smoke a bit. I agree it is totally different than oil scavenging on a 2 stroke which usually helps oil your top crank bearings
posted 12-18-2009 10:13 PM ET (US)
Been following this topic with particular interest in the 2-stroke DFI's oil injection systems since it's a departure from introducing the oil as a mixture with gasoline. My DFI HPDI has a similar oil system to BRPs.
It has been said that lubrication is the lifeblood of the outboard. Injecting 2-stoke oil into the engines without mixing is relatively new so it's natural for some to be interested in the specifics. We have some replying who have posted a diagram of one series of E-Tec and may have a better understanding or access to descriptions not easily found online. Please share what you know. The BRP site has parts catalogs which can give some ideas of how it works.
After taking a look at catalogs, it appears the portion of the injection system targeting the crank related bearings uses 6 individual ports/nipples in the intake side of the crankcase assembly. The oil is simply injected into each cylinder's intake and dispersed by the incoming air. Six additional oil lines target the cylinder sleeves with a lesser amount of oil per cylinder. Where exactly the ports/nipples are located is in question.
posted 12-19-2009 03:47 AM ET (US)
I'd like to correct the last reply. The 2-stroke oil injection system that injects undiluted oil has been with us at least as long as the mid 1980's on many carbed Yamahas. Referring to some 150 hp Yamahas, they injects oil into the inlet/crank case like the BRP but not to cylinder sleeves. They also have a similar recirculation system.
Found it interesting their carb and DFI both use undiluted intake oil but their EFI models only mix oil with gas at the vapor separator.
posted 12-19-2009 08:45 AM ET (US)
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