posted 02-24-2012 04:47 PM ET (US)            

Yamaha HPDI is a high pressure system which uses one or two pumps to pressurize the fuel centrally in the rail to very high pressures, something close to 1000 PSI if I recall correctly. That high pressure fuel is then introduced, atomized of course, into the cylinder when the injector opens.

Mercury and Tohatsu use a form of Orbital's air compressor system to blow a stream of pressurized air through the fuel in the injector to atomize it while its being introduced into the cylinder.

All three systems are quite different systems.

posted 02-24-2012 09:41 PM ET (US)            

Bombardier uses their own E-TEC technology, including their patented E-TEC voice-coil injector.

Yamaha uses their own technology, which they call HPDI, for high-pressure direct injection.

You should visit the various manufacturers' websites to learn more about their methods. They typically will provide information about them. The information they provide will be much more reliable and informative than what you might get here from anecdotal remarks.

For the E-TEC you may find my article informative. It also contains a number of links to other informative articles. Rather than try to recount all of that information here, just follow this link and read all of that article, and then follow all the included links and read all of those articles:

posted 02-25-2012 12:16 AM ET (US)         

It's also probably the most conventional of the three, being a high pressure common rail system just like the ones used in diesel's and gasoline direct injection in automobiles for for some time. With diesel's the common rail operates typically above 15,000-20,000 psi or more so 1000 psi is not significant.

posted 02-25-2012 09:02 AM ET (US)            

The Orbital Combustion Process is a rather complex arrangement of pairs of injectors for each cylinder. There is a fuel injector and an air injector, so in a V6 engine there are a total of twelve injectors. The air being injected is raised to an elevated pressure before reaching the air injector. This requires an air compressor and a high-pressure air distribution system. The air compressor is typically driven by a belt from the crankcase pulley of the main engine. The air compressor is a parasitic load on the main engine and probably takes off three to five horsepower to operate. The fuel is also raised to an elevated pressure before distribution to the fuel injectors. Both the air and the fuel in their distribution systems have to be held at a regulated pressure, so this requires pressure regulators in each system. The injectors operate electrically, so the engine control module has to provide electrical power and electrical impulses to operate the injectors. Again, because of the need for twin injectors, everything is doubled compared to simpler systems. The engine controller in a V6 OptiMax is running 12 injectors, not six. Much like Yamaha, Mercury uses the Orbital Combustion Process on only a segment of its product line. I believe that the Orbital Combustion Process in outboard engines made by Mercury has been limited to engines of about 90-HP or higher.

posted 02-25-2012 09:39 AM ET (US)            

http://continuouswave.com/ubb/Forum1/HTML/011847.html

where some of the changes are described. In general, the biggest change seems to have been the cowling graphics.

After announcing the new model as the OptiMax The Next Generation, that designator seems to have been dropped, and the engine name reverted to just OptiMax.

posted 02-26-2012 12:42 PM ET (US)         

Diesel engines need much higher injector pressures so driving the unit injectors purely by electricity is not feasible; typically they are primarily powered by a cam or hydraulic [pressure] and a small electronically controlled solenoid actuates a valve to precisely time the injection.

posted 02-26-2012 12:55 PM ET (US)         

Although the advantages are not as great for a 4-stroke to use DI given that the valves provide the primary benefits that DI is needed for in a 2-stroke. There still would be some good performance and efficiency gains for a DI 4-stroke outboard, the same you see in some of the modern automobiles which are now going to DI in increasing numbers.

posted 02-26-2012 02:53 PM ET (US)            

There's a lot more to direct injection technology than I ever considered and other types I didn't even know about. I haven't had time to research everything yet, but I'm slowly learning as I go and have time to read.

I'm sure it's better to look directly to the manufacturers to learn about the varuous technologies, but I'm a bit lazy and a "Cliff Notes" kind of reader. I guessed that many on this site would know more than I ever wanted to learn about direct fuel injection and could summarize pretty well....I think I guessed right!

I wonder about the pros and cons to HDPI vs. low pressure systems? Must be something there for Yamaha to hang on to this technology and maybe not enough for others to change to it?

Anyhow, thanks again to all. It is certainly an interesting learning experience and will certainly give me more to consider if and when I purchase my next outboard.

posted 02-26-2012 03:14 PM ET (US)            

With a solenoid actuator there are typically only two states: on or off. The motion is only one way, and the return is typically created by a spring that has been compressed and stored the rebound energy. When actuating the solenoid has to overcome the spring and compress it to store the energy needed for the rebound. In a voice coil the movement can be in either direction by reversing the current in the voice coil.

Advances in the field of permanent magnets have allowed for the creation of many very small but powerful electric motors. Good examples are the small electric motors in many consumer devices, such as the electric power window actuators in your car or the the auto focus motor in your camera.

The technology of magnets is advanced recently. It is common now to find magnets so small yet so powerful that a grown man cannot pull these small magnets apart without using a lever to gain mechanical advantage. It is quite astonishing how much magnetic power can be created in a small magnet. This sort of permanent magnetic energy is utilized in the E-TEC injector.

In addition the E-TEC makes very clever use of the regeneration of electricity that occurs when the voice coil is moving in the magnetic field to actually generate and store some of the electrically energy it will use on its next operation. This technique is also patented. Further, the control of the E-TEC voice coil injector is very sophisticated and allows for a reversal of electrical current to create a braking effect, removing some of the clatter noise of the injector by creating a softer landing of the plunger on the rebound stroke.

I am not inclined to dismiss the E-TEC injector as just some relic of the 1970's that has not been improved or advanced, or in some way is lacking in its suitability for the task of injecting fuel directly into the combustion chamber of a gasoline engine. That it has not been applied to diesel engines is of no concern to me. I have not studied the technology of diesel engine injectors. While I am sure it is a rich field of endeavor, I don't see precisely how it affects two-cycle gasoline outboard engines with direct injection technology.

Another more astonishing characteristic of the E-TEC injector is it individually measured and calibrated characteristics of fuel flow. Each injector is supplied with a thorough description of its actual performance in the form of 33 coefficients. This data is supplied to the engine controller so that the control of the fuel flow into the combustion chamber can be made even more precise. And even more amazing is the inclusion of algorithms in the control system to account for aging of the injector and variation in performance after running for millions of cycles. The E-TEC is quite sophisticated in this way.

posted 02-26-2012 03:25 PM ET (US)            

quote:

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None of the 4-stroke makers will do DFI until the EPA regs push them to do so.

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Yikes, can you imagine what such a motor would cost? (and weigh)? Add the cost of high pressure direct injection to the cost of the complex and expensive DOHC 4-stroke valvetrain--I don't want to contemplate it.

posted 02-26-2012 05:02 PM ET (US)         

quote:

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None of the 4-stroke makers will do DFI until the EPA regs push them to do so.

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I disagree, the performance and efficiency gains would be enticing to consumers in it's own right. Imagine Yamaha 350hp DI 4.2L V6 motor with even better economy than the current 300hp version, I think it would be well received so long as it proved reliable.

Time will tell though.

quote:

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I am not inclined to dismiss the E-TEC injector as just some relic of the 1970's that has not been improved or advanced, or in some way is lacking in its suitability for the task of injecting fuel directly into the combustion chamber of a gasoline engine. That it has not been applied to diesel engines is of no concern to me. I have not studied the technology of diesel engine injectors. While I am sure it is a rich field of endeavor, I don't see precisely how it affects two-cycle gasoline outboard engines with direct injection technology.

---

I never dismissed the E-TEC injector technology, or even came close to implying it was not up to the task. It is however important to keep in perspective the shoulders of giants that all modern inventions rest upon. Evinrude did not invent 2-stroke direct injection nor the unit injector(which combines the pump and injector in one device allowing a low pressure fuel rail). Instead they applied a clever use of existing voice coil technology to the FICHT system which in itself used a solenoid instead of cam to generate pressure in the unit injector. They patented the modifications and used it to build a good engine, good for them. None of it would have been possible without the many years of existing hard won progress in engine technology. It is too bad you have no concern for diesel direct injection application since almost all direct injection techniques where first developed for diesel many years ago as it is a requirement for that engine cycle. By the way the unit injector was first developed in the early 1900's not in the 1970's, however the first electronically controlled one did not arrive until the 1990's. Nearly all the algorithmic control techniques you describe for wear and calibration are used in other types of fuel injectors, typically referred to a as fuel trims.

[quote]Yikes, can you imagine what such a motor would cost? (and weigh)? Add the cost of high pressure direct injection to the cost of the complex and expensive DOHC 4-stroke valvetrain--I don't want to contemplate it.[/quote[

posted 02-26-2012 05:35 PM ET (US)            

I think you were attempting to school me in how the strategies and sensors in 1000+ psi direct injection systems is very similar to that in the 40 psi SEFI systems. Are you claiming the parts cost of the 1000+ psi DI systems are not significantly higher than the parts costs of the 40psi SEFI systems?

posted 02-26-2012 07:55 PM ET (US)         

I am not claiming a DFI system wouldn't cost more than an EFI system. I do however disagree that they are not similar mechanically. Direct injectors are usually solenoid actuated pintle just like most EFI injectors, they are of course made with more material and with tighter tolerances because of the pressure differences. The fuel pumps are usually mechanically driven to obtain the high pressures rather than electrical. The delivery pipes and rails are more robust again to deal with the higher pressures.

posted 02-26-2012 09:09 PM ET (US)            

quote:

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I disagree, the performance and efficiency gains would be enticing to consumers in it's own right. Imagine Yamaha 350hp DI 4.2L V6 motor with even better economy than the current 300hp version, I think it would be well received so long as it proved reliable.

---

What enticing performance and efficiency gains would there be? At what cost? There is a big difference between putting DFI on a 2-stroke and putting DFI on a 4-stroke. You're not going to get a 600+ percent improvement on fuel efficiency at idle like you do going from a carb or EFI 2-stroke to a DFI 2-stroke. As evidenced by the automakers like Ford and Audi, on a 4-stroke with DFI, the big performance and efficiency gains come from using smaller displacement, fewer cylinders and turbocharging or supercharging.

Both of my cars have DFI 4-stroke engines, one is naturally aspirated and the other is turbocharged. I don't have any good comparison for the turbocharged motor. But on the naturally aspirated car, both the city and highway fuel efficiency improved by 1 MPG (6 percent and 4 percent respectively) over the prior naturally aspirated EFI motor in substantially the same version car. It isn't clear that all of the gain came from just a change in the motor.

posted 02-26-2012 09:42 PM ET (US)         

If I where to guess based on the injector price differences I would say it's 2-3x the cost for the fuel system in a GDI engine.

posted 02-26-2012 10:04 PM ET (US)         

quote:

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There is a big difference between putting DFI on a 2-stroke and putting DFI on a 4-stroke. You're not going to get a 600+ percent improvement on fuel efficiency at idle like you do going from a carb or EFI 2-stroke to a DFI 2-stroke.

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No disagreement here, it's exactly what I said in my first post, 2-strokes definitely gain the most from DI, while the valving in 4-strokes accomplishes much of the same thing even when carburated.

quote:

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Would the promise of 6 percent better fuel economy at idle for a boat at low wake speeds and 4 percent for the boat on plane be enticing? How much more would you pay for that over the EFI version of a motor that has an MSRP of something like $26,000?

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I don't think that kind improvement would be enticing enough, although typically with DFI you not only gain economy but performance as well. If economy went up 6% and horsepower went up by 50, that might be more reasonable.

The 5.6L Nissan DI V8 that is in the new QX56 has fuel economy went up by more than 10% while having a more than 20% increase in horsepower over it's non DI predecessor.

posted 02-26-2012 10:29 PM ET (US)            

quote:

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It is too bad you have no concern for diesel direct injection application ...

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I never said that. What I said about diesel direct injection was:

"I have not studied the technology of diesel engine injectors...I am sure it is a rich field of endeavor..."

I have read about new methods of fuel injection in diesels, but the explanations are not very good. They seem to assume that the reader already know what the new invention is, what it does, and how it works, and simply giving the generic name of the technique will be enough to impress people. I really know little about diesel direct injection methods and innovations. Perhaps you can start a new thread and explain all about diesel direct injection technology and how it has advanced in the past few years. I do appreciate technology, so I would be interested to know about it.

My point was--and I thought I make it clearly--that I don't see that the inability of the E-TEC injector to be used on a diesel represents some sort of drawback for the E-TEC injector. The E-TEC injector seems to be doing a good job in the low compression two-cycle engine application that it was developed for. That application, by the way, is the topic of this discussion.

posted 02-26-2012 11:36 PM ET (US)         

You also said "I don't see precisely how it affects two-cycle gasoline outboard engines with direct injection technology."

I am not sure where you got the idea I was trying to disparage the E-TEC injector because it cannot produce the required pressures for diesel operation. I was actually trying to explain why you cannot find pure electrically driven diesel unit injectors and how Ficht and later Evnirude/Bombardier must have seen this as an opportunity when applying existing DI technologies to lower pressure gasoline operation. They used this opportunity to design a purely electrical unit injector and obtain a patent on the technology locking it into their 2-stroke engine offerings for the time being. I would say a very good business move.

I have found BRP themselves referring to the E-TEC injectors as unit injectors in their own literature: "electronically controlled unit injectors individually pressurise fuel to 550 - 700 psi and inject it directly into the combustion chambers
just like a direct injection diesel engine". http://www.brp.com/NR/rdonlyres/DBADEF58-926B-4631-82E5-DE85800314EC/0/GUIDE_ETEC75.pdf

Even Orbital's low pressure air injection system used on the Optimax is related to Diesel's original air injection system on his first engine.

posted 02-27-2012 07:30 AM ET (US)            

I'm not sure I follow that. The 6 and 4 percent increases in fuel economy are measured using the same city and highway test loops so presumably the same amount of HP is required to complete those tests if the car is substantially the same which in my example is about as close as it gets given that it was a mid term refresh of that model's 6 year production run. Maximum HP went up but the displacement of the engine went up as well.

quote:

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The 5.6L Nissan DI V8 that is in the new QX56 has fuel economy went up by more than 10% while having a more than 20% increase in horsepower over it's non DI predecessor.

---

From what I've read regarding the Nissan QX56, in addition to adding DFI, Nissan added varible valve timing and went from a 5 speed to a 7 speed transmission. Also, the newer version of the motor makes its peak HP at 5800 RPM versus 5200 RPM. Peak torque is up 20 ft-lbs but at a higher RPM.

If DFI ever makes it to a 4-stroke outboard, and that is a big if, it will probably show up on a Honda or Suzuki first given their use of automobile engines as powerheads. But this won't happen until Honda or Suzuki adopt that technology for their automobiles from which they borrow the motors. They won't design/build a system for outboards, the production volumes are just too small when they don't currently need such to meet emissions regulations.

posted 02-27-2012 08:02 AM ET (US)            

That a direct-injection method designed for a two-cycle gasoline outboard engine with low compression is not applicable to a diesel engine with high compression does not surprise me, nor does it make me think that somehow the gasoline engine method or art must be held in a lower opinion. The methods used for direct-injection in gasoline engines may be different from diesel, but I believe they may be just as skillfully designed, engineered, and manufactured. I don't know what special benefit is obtained when comparing them with diesel, other than to gain a historical perspective. Diesel direct-injection came first. I think we can agree on that.

The inquiry was in regard to how the E-TEC, OptiMax-TLDI, and HPDI systems were alike or different. The initial assumption was they might really be all the same. I believe it has been demonstrated that the three methods are different. Of course they all end up injecting fuel directly into a cylinder, but they accomplish it in different ways.

In regard to the various methods, at least two of them, E-TEC and Orbital, are protected by patents, and thus it is reasonable to assume that there is something about them that did not exist in the prior art of diesel direct-injection technology. If the E-TEC system or Orbtial system were not new, useful inventions, then it is unlikely they would have been granted the protection of patents to prevent unauthorized copying.

posted 02-27-2012 08:52 AM ET (US)            

http://www.brp.com/NR/rdonlyres/DBADEF58-926B-4631-82E5-DE85800314EC/0/ GUIDE_ETEC75.pdf

posted 02-28-2012 03:23 AM ET (US)            

quote:

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I think that DFI on 4 stroke motors is the way to go and agree with Peter that it will probably take Honda to adapt this technology to outboard motors. I only hope that they can do it without a substantial increase in weight.

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They will be able to do it without a substantial difference in weight. They will not be able to do it without a substantial difference in cost-- not if a 1000-20,000 psi fuel system is engineered to last the service life of the motor. You will either pay up front for a durably engineered, leak-free, high pressure fuel system, or you will pay out the back with more frequent and expensive service.

What do two-stroke E-TEC motors, which are GDI, cost, in comparison to equivalently powered, non-GDI, four-stroke motors? What would a motor cost that takes the most expensive parts of both concepts and add them together?

posted 02-28-2012 09:58 AM ET (US)            

In the diesel world we often oversimplify for convenience in discussions. We say "injector" when speaking of low pressure systems and we say "nozzle" when speaking of high pressure systems. Injectors pressurize and inject fuel while nozzles simply spray fuel. An example of a high pressure system is one used by CAT and a low pressure system is one used by Detroit Diesel.

posted 02-28-2012 11:46 AM ET (US)         

quote:

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What do two-stroke E-TEC motors, which are GDI, cost, in comparison to equivalently powered, non-GDI, four-stroke motors? What would a motor cost that takes the most expensive parts of both concepts and add them together?

---

I believe E-TEC injectors cost between $250-300 for replacements, while typical EFI injectors are are about $100 each. EFI needs a "high pressure" fuel pump after the lift pump but I believe E-TEC also have a similar pump separate from the lift pump just like an EFI system.

The 4-stroke's have the valve train, while the E-TEC's have Nasa alloy pistons and a stronger lower end to deal with twice the power strokes.

Not sure which costs more to produce here in total.

I do think the E-TEC injector would work well in a 4-stroke if it could be fit in between the valves. The valve train makes this challenging given the large size of the injector. Perhaps some changes like a longer neck where the coil can be located further away from the tip would help with the design.

quote:

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A significant advantage of DFI in a four stroke cycle engines is that it permits a much higher compression ratio with very tight control of the quantity and timing of the fuel injected during each revolution.

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Not only higher compression ratio but much leaner mixtures. In a 4-stroke DFI allows fuel to be injected after the intake valve closes, and with high enough pressure even during the power stroke, this impossible with standard EFI. By not injecting fuel until close to TDC with the proper stratified charge air fuel ratio above 50:1 can be used with no worry of pre-ignition. The down side of such extreme lean burn is higher NOx emissions.

To take advantage of the ability to go very lean and keep emission certification you would probably need to use a catalytic converter, which no outboard currently does, but most automobiles do.

Diesel's are even moving to selective catalytic reduction using exhaust fluid, this fluid is injected into the exhaust from a small tank at a ratio similar to two-stroke oil/gas ratio's, it reacts with NOx breaking converting it back into Nitrogen gas, water and CO2. This is why the new 2011 Ford power stroke diesels get such good mileage while having better power, the DEF allows them to run more compression and leaner mixtures.

I doubt such a system would go over too well in outboards. Imagine changing oil and still filling a small tank every so often, or a two-stroke having to keep two small tanks filled with different fluids. It would however allow better power and fuel use while still keeping emissions low.

posted 02-28-2012 09:33 PM ET (US)         

quote:

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The E-TEC fuel lift pump is very low pressure--it's actually below 0-PSI because it is a suction, not a pressure.

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It's hard not to be pedantic on this one, every pump has a suction side that would measure below zero pressure, if measured on the discharge side it will be positive. The E-TEC lift pump looks very similar every other outboards lift pump(vacuum driven diaphragm).

The vapor separator / "medium" pressure pump at 25 psi looks and costs just about the same as everyone else's EFI vapor separator fuel fuel pump assembly. Most EFI's use similar rubber hoses and clamps for their modest pressure. pcrussell50 said his racing EFI system's run at a modest 39 psi as a comparison.

Here is Evnirude's description from their own literature: "The remainder of the fuel system uses proven existing components. The fuel lift pump on the left will be familiar to many marine technicians, its most recent use was on the 55 HP commercial models. The vapour separator (right) is the same well proven water cooled unit, with integral electric fuel pump, as that used on current V4 and V6 DI models." http://continuouswave.com/whaler/reference/IAME44-1_e-tec.pdf

quote:

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How does fuel octane factor into all this DFI technology?

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DFI actually allows lower octane fuel to be used. Since fuel is not injected until much later in the compression stroke pre-ignition is basically eliminated and knocking is much reduced. Diesel fuel is actually extremely low octane and needs to be since it has no spark plug to ignite the charge and relies on compression alone.

posted 02-29-2012 07:51 AM ET (US)            

quote:

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EFI needs a "high pressure" fuel pump after the lift pump but I believe E-TEC also have a similar pump separate from the lift pump just like an EFI system.

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In the E-TEC (and Ficht) there is an electric fuel pump located downstream of the crankcase pulse driven diaphragm lift pump. It is a low pressure circulation pump. It circulates fuel through the feed and return lines running to and from the injectors. About 25 PSI is all there is in the fuel lines. All the heavy "lifting" is done at the injectors in the Ficht and E-TEC systems. In contrast, all the heavy lifting in the Yamaha system is done by a central belt driven high pressure pump. Fuel is pressurized to 700 PSI in the fuel rails.

With respect to an anticipated weight gain for an EFI 4-stroke to go to DFI, Yamaha provides some guidance. Their OX66 EFI 250 weighed approximately 500 lbs. The DFI 250 weighs approximately 540 lbs for a 40 lb increase. The weight gain on the smaller 2.6L HPDI was about 25 lbs.

As previously mentioned, it will be a long while before 4-stroke outboard makers adopt DFI as is evident by Yamaha developing an entirely new sleeveless cylinder 4.2L block rether than just adding DFI to the 3.3L block which would have added more weight to an already heavy 600 lb outboard motor. Merely adding DFI would not have made the 4-stroke outboard motor competitive with 2-stroke outboard motor of similar displacement. They still need more displacement than a 2-stroke to produce a similar power curve.

posted 02-29-2012 02:06 PM ET (US)            

quote:

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Now if they can make it run on Budweiser beer, then they really have something.

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Exactly! An engine that runs on water is something of a holy grail of engineering...

posted 02-29-2012 02:23 PM ET (US)            

Thanks Peter. Very interesting. I had no idea.

posted 02-29-2012 04:31 PM ET (US)         

The problem with diesel is weight, and it's not really from the fuel system. All the major mechanical component must be more robust to handle the very high compression and the heat generated by such lean mixtures. Diesel usually have large oil reservoirs as well to help with heat dissipation. The prototype above is 800 pounds for a 3.0L engine.