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Author Topic:   Why DFI-Engines Are Less Powerful

L H G posted 07-23-2009 07:32 PM ET (US)
Why do direct fuel injection engines of same displacement usually put out less horsepower than a conventional 2-stroke?
jimh posted 07-23-2009 07:33 PM ET (US)
This topic was introduced into another discussion on a different topic. I have separated it so that it can be discussed on its own.
jimh posted 07-23-2009 07:35 PM ET (US)
I think the premise is flawed here. Can you give an example where a direct fuel injection two-cycle engine has less power than a carburetor two-cycle engine of the same displacement? In my experience the opposite it true. For an example I would cite the E-TEC 250-HP 3.3-liter engine compared to the Evinrude 225-HP 3.3-liter carburetor motor. This example contradicts the premise of the question.
L H G posted 07-23-2009 08:25 PM ET (US)
I'm sure there are exceptions, but the premise is not flawed. I don't know much about Evinrudes, but the 3.0 liter 225's had to be increased 10% to 3.3 liters to get the same 225HP from an E-tec.
Mercury 2.5 liters were rated at 200 HP, and actally put out a little more, but they had to go to 3.0 liter block for the 200 Optimax. Highest 2.5 liter Optimax is 175HP.
It seems to be the HP at the top end of a given block that suffers, requiring a larger displacement to get the same HP. At the lower end, like the 150's, not a problem.
And only lately, newer technology like carbon fiber reeds is being used to boost the HP of the DFI's
To get 275 HP out of an Evinrude 250HO, they had to increase the cubes even more. And Mercury had to do this also for the 300 Optimax, where previously the 300 EFI used the 3.0 liter block.
So the question is still, why do DFI's require more displacement, and more weight and heavier engines, for the same upper range of HP on a given block size?
jimh posted 07-23-2009 10:25 PM ET (US)
In the OptiMax motors the engine has to run an air compressor. This probably robs some horsepower from the output shaft. The need to run the air compressor is unique to the OptiMax and not typical of every DFI engine. Since the air compressor in the OptiMax is made from a small outboard motor block, you could figure it probably need 3 to 5-HP to drive it. The belt and pulley have some losses, too, which might add more to the power diverted from the output shaft.
The DFI engines also generally meet more stringent emission regulations. We have learned from the VERADO engine experience that lowest emission output is not always coincident with most power or most efficiency.
Thus we have two factors operating in the typical DFI motor: it has a different fuel induction system and a different emission rating. To conclude that any difference in horsepower output compared to a carburetor motor with high-emission must be due to EFI is to overlook the influence of the emission rating. Lower emission from the engine may be responsible for lower power output per displacement, not the DFI technique itself.
boatdryver posted 07-23-2009 10:25 PM ET (US)
reduced fuel consumption pre cubic centimeter of displacement ? , i. e. less unburned fuel going out the exhaust into the water?
JimL
L H G posted 07-23-2009 11:13 PM ET (US)
So Jim, your comment, saying my premise is flawed, is actually the one flawed. Your later comment "Lower emission from the engine may be responsible for lower power output per displacement" is exactly what I was saying. With Optimax, the compressor is an obvious reason, but what is it with E-tec and HPDI?
Name me ONE engine, Evinrude, Mercury or Yamaha, where the DFI engine has less cubes than the old fashioned conventional 2-stroke they made at the same *TRUE* (not decal) HP, or great HP from the same block. I can't find any, except in the lower ranges of a given block where cubes are the same because the block is not being pushed for max output. I'm just talking HP.
As an example, could Evinrude have gotten 225 E-tec HP out of your old 3.0 liter 225 block (although the Mercury Optimax does)? Don't think so. They needed 10% more cubes to do it, just like Mercury did for the 300. When it comes to HP, the DFI systems aren't as strong per cubes. Performance wise, the only thing they are better at when compared to EFI or OX66 is fuel economy and a smoother idle.
jimh posted 07-23-2009 11:25 PM ET (US)
There are two assumptions needed here:
--that DFI engines are less powerful, which I don't believe is proven yet, and
--the DFI is the cause.
Low emission engines may be the cause of less power output per displacement.
Let me disprove your theory regarding the OMC 225 versus the E-TEC:
--the 3.0-liter carburetor OMC engine was available as a 175, 200, and 225-HP model.
--the 3.3-liter E-TEC BRP engine is available as a 200, 225, and 250-HP model.
There appears to be a completely congruent relationship between displacement and horsepower in both cases:
--carburetor 225-HP and 3.0-liter = 75-HP/liter
--E-TEC 250-HP and 3.3-liter = 75.8-HP/liter
I cannot see how citing this motor provides any manner of proof that the power output form a DFI motor is typically less than a carburetor motor of same displacement. In this case, we can't have exact same displacement, because the DFI motor is not the same. Let's turn to the smaller V6 motors:
--2.6-liter carburetor OMC engine was available as a 150 or 175-HP model;
--2.6-liter E-TEC BRP motor is available as a 150, 175, or 200-HP model.
There appears to be a relation ship between horsepower and displacement that contradicts the fundament assumption that began this discussion:
--carburetor 175 and 2.6-liter = 67.2-HP/liter
--E-TEC 200 and 2.6-liter = 76.9-HP/liter
QED.
Plotman posted 07-24-2009 12:14 AM ET (US)
Nobody uses QED anymore. I miss that.
seahorse posted 07-24-2009 12:32 AM ET (US)

quote:

As an example, could Evinrude have gotten 225 E-tec HP out of your old 3.0 liter 225 block? Don't think so.
For 1999 and 2000 the Evinrude FICHT put out 225hp out of the standard 3.0L block.
In 1991 the block was increased to 3.3L because that year they came out with the 250hp version, and used the 3.3L block for all the rest of the 200-225 V6 models for commonality of parts.
In 2008 they came out with a 3.4L block for the 300hp E-TEC. For 2010 both the 3.3L and 3.4L blocks will be in production, but that is subject to change.
David Pendleton posted 07-24-2009 12:34 AM ET (US)
What the heck was the air compressor for?
number9 posted 07-24-2009 12:44 AM ET (US)
L H G,
Yamaha SAME displacement, not more or less. HPDI is heavier and has their belt driven high pressure mechanical fuel pump.
In most cases DFI is used to improve fuel economy and lower emission. The components of a DFI system generally add weight and will rob some power due to increased electrical demand from electric fuel pumps.
10% increase increase in displacement adds little material weight and is a good marketing tool.
Since Merc doesn't market any small 2-stokes these days, who makes that compressor for the OptiMax?
So to answer your questions,
DFIs do not require more displacement.
More weight and heavier engines, yes.
jimh posted 07-24-2009 09:15 AM ET (US)
Re OptiMax air compressor:
As you probably know, the Mercury OptiMax uses under license the Orbital Combustion Process (OCP) from Australian ORBITAL. The Orbital Combustion Process requires that air at an elevated pressure (or compressed air) be available to be injected into the combustion chamber. In an OptiMax engine the compressed air is supplied from an air compressor that is driven by a fan belt from the main engine crankcase. The compressed air is then distributed around the engine to the air injectors for each cylinder where is it pre-mixed with fuel before the air-fuel mixture is injected into the combustion chamber by a second injector. Or something like that. It's kinda complicated. But, to use the Orbital Combustion Process you need compressed air.
Peter posted 07-24-2009 09:43 AM ET (US)
"I don't know much about Evinrudes..." -- LHG
That remains abundantly clear. ;)
"In 1991 the block was increased to 3.3L because that year they came out with the 250hp version..." -- Seahorse
I think you mean 2001. It would not surprise me if they simple moved the 200+ to 250 HP E-TECs over to the 3.4L platform.
seahorse posted 07-24-2009 09:51 AM ET (US)
Thanks, Peter,
That's what happens when I'm up past my bedtime.
2001 is correct
Tohsgib posted 07-24-2009 10:54 AM ET (US)
The fact that OMC has a 2.6L 200hp E-Tec I think "busts" this whole myth. Second, just because an engine goes from 3L-3.3L does not mean larger bore, it could be longer stroke. Lastly, with modern technology if you could make a larger displacement block with the same weight and dimensions of the old one...why not?
L H G posted 07-24-2009 11:18 AM ET (US)
No it doesn't Nick. That weak 200 needs some kind of special valve to even get close to a true 200 at the prop. I don't even think it makes it. I'd put my 2.5 liter 200 EFI's against one of those 2.6 liter 200's any day. Merc's 200 Optimax is 3.0 liters, and to run with it, Evinrude needs a 3.3 liter 200 HO. More cubes in both cases for 200 HP.
Since I don't care to know much about Evinrudes, how do the 90 Etecs compare to the old 60 degree 90 2-strokes of the 90's? But I do know the old carbed engine is faster, and puts out a true 90 HP at the prop. People who have repowered here have reported that fact. So DFI technolgy once again is slower and heavier.
And in spite of what Seahore and Peter say, I still say Evinrude needed 3.3 liters to get the 225 HP out of the E-tec technology. The OMC 3.0 liter 225 Fichts are the ones that put the company out of business, and not what I am talking about anyway. They are obsolete.
newt posted 07-24-2009 11:54 AM ET (US)

quote:
In the OptiMax motors the engine has to run an air compressor. This probably robs some horsepower from the output shaft.
This may be a stupid question, but if the air/fuel mixture is compressed prior to injection into the cylinder, than isn't less mechanical energy required of the piston during the compression stroke? I mean, one way or another, the air/fuel mixture must be compressed prior to ignition.
Is it reasonable to assume that most of the energy required by the OptiMax compressor would have been expended by the compression stroke anyways?
jimh posted 07-24-2009 12:29 PM ET (US)
Actually, the OptiMax needs even more energy than normal because the compressed air has to be forced into the cylinder as the cylinder is rising and compressing the air in the cylinder. Its a compressor feed into a compressor.
newt posted 07-24-2009 12:35 PM ET (US)
So now you have double compressed air that pushes back on the piston during the power stroke thereby saving on fuel needs.
I think the Optimax actually produces more energy than it consumes. :)
newt posted 07-24-2009 12:44 PM ET (US)
All kidding aside, I hypothesize that the net additional energy required by the OptiMax compressor is limited to minor friction, energy conversion, and heat losses due to the added machinery of the compressor.
Of course, I know very little about the OptiMax technology, and am basing my entire hypothesis on the principle that energy is neither created nor destroyed.
Tohsgib posted 07-24-2009 01:04 PM ET (US)
Don't look at the compressor like a supercharger. The DFI compressor atomizes the fuel charge into a fine mist that is shot out the injectors. The finer the fuel charge the more efficiently it burns. A supercharger just rams(literally) the fuel and air charge into an engine therfore giving it more hp but less efficiency. The reason superchargers are efficient is bacuase you can make more hp with a smaller displacement and when you don't need the hp, the supercharger is not working as hard. In other words a SC will make 300hp out of say a 3L engine where 300hp naturally aspirated would take a much larger engine with probably more cylinders to produce so they equal out for the most part but weight is much lighter, etc.
Jerry Townsend posted 07-24-2009 01:12 PM ET (US)
There are a few issues involved here - one, as JimH points out, the compressor draws power, but the choice of compression via the piston or a separate compressor is a toss-up - neither are 100% efficient.
One obvious unknown - is the fuel/air ratio - and I would bet the farm that the major difference in performance is attributed to a different air/fuel ratio. Each engine is designed to run at a specific air-fuel ratio. And, the engines are quite sensitive to fuel-air differences - well, it significantly alters the combustion process - and that is where the power/energy is developed. ---- Jerry/Idaho
Jerry Townsend posted 07-24-2009 01:18 PM ET (US)
One additional thought - I would fully expect the DFI engine would produce more specific energy - simply because the air-fuel ratio can be more closely controlled than via a carbreater. ------ Jerry/Idaho
number9 posted 07-24-2009 01:19 PM ET (US)
Just did a quick research on OPC. It is basically a DFI system that injects fuel into the cylinder close to the spark. From what I read it uses the compressed air at a relatively low pressure to enhance fuel atomization. Fuel and air are mixed at the injector. In contrast the Yamaha HPDI depends upon the fuel pressure and design of the injector.
Tohatsu TLDI, Two stroke Low pressure Direct Injection, is apparently licensed by Orbital also. Here's a link that that provides a decent illustration of how the process works.
http://www.tohatsu.com/tech_info/brochure_pdfs/2009_brochure/ Toh2009_115.pdf
It sounds like a great technology that allows the use of less sophisticated pumps and injectors.

number9 posted 07-24-2009 01:27 PM ET (US)
That's OCP and the compressor is driven by a compressor belt not a fan belt. All the fan belts were too long.
L H G posted 07-24-2009 03:02 PM ET (US)
Don't forget also that BAss and Walleye Boats Magazine did their last "shootout" on all makes of 50HP engines, all technologies.
The low technology 2-stroke Mercury 50 won, with the 4-stroke Mercury coming in 2nd. Fuel economy, running noise, acceleration and top speed were all a part of the testing formula. The E-tec 50 was a slug at 2nd last, and the slowest in top speed by 5 MPH. A pretty wimpy 50 compared to the top performing low tech Merc.
I think that's when Evinrude determined they weren't going to advertize with them any more, and the mag folded!
fourdfish posted 07-30-2009 11:06 AM ET (US)
Again, those Bass & Walleye tests were so flawed they could could not hold up in high school physics lab.
They were just OPINIONS like Larrys that Mercs are better.
They are folding because they just were not popular enough
to print. Merc is the one that cut back on the advertisments
and put them in the tank. BRP did very little advertising in that rag.
The only DFI engines that could be less powerful than a
4 stroke would be the Optimax. NO PROOF exists anywhere that the DFI E-TEC is less powerful than a 4 stroke. In fact just the opposite is probably true because of several factors
such as weight and friction.
andygere posted 07-30-2009 11:59 AM ET (US)

quote:
That weak 200 needs some kind of special valve to even get close to a true 200 at the prop.
What makes this motor a "weak" 200? It accelerates better than the 2.4L Mercury 200 it replaced, and has the same top end. Does that make the Merc a weak motor too? How would it stack up to something like a 2.5L Mercury EFI? Small displacement (and archaic fuel injection system) probably make that a weak motor too.
L H G posted 07-30-2009 04:01 PM ET (US)
Andy - I was not comparing the brand new, modern high tech Evinrude 200 to an old, low tech, carbureted, throwback 2.4 liter Merc 200 from 1986.
I was comparing it to it's current modern day competition. How would it run against the plain, vanilla, Mercury 200 Optimax (not the souped up 200 XS Optimax)? Is the 200 Optimax "weaker", or is the Evinrude 200 "weaker", considering that both cost the same money? Peter here likes to say cubes count. Well if so, Mercury's 200 has them.
Would your 200 Evinrude blow away one of my 200 EFI's? Not sure, but not likely. And it probably doesn't matter anyway.
Incidentally, I did not start this thread. Jim took it out of context from another discussion I was participating in.
Guess he liked the subject.
Peter posted 07-30-2009 05:28 PM ET (US)
"I was not comparing the brand new, modern high tech Evinrude 200 to an old, low tech, carbureted, throwback 2.4 liter Merc 200 from 1986."
Really? But this is what YOU asked Larry "Why do direct fuel injection engines of same displacement usually put out less horsepower than a conventional 2-stroke? There were no qualifiers on the question.
Perhaps the question only applies in the Mercury world. The conventional 2.6L Evinrude/Johnson engines that preceded the DFIs only made up to 175 HP. On the same block the DFI 2.6L makes up to 200 HP.
By all accounts I've read, the 2.6L 150/175 DFI motors are more powerful than their conventional counterparts like the one I have.

towboater posted 07-31-2009 12:49 AM ET (US)

Id like to see what a new etec could do if you removed the muffler restrictions and re programed the fuel/air mix?

andygere posted 07-31-2009 02:20 AM ET (US)

quote:
Why do direct fuel injection engines of same displacement usually put out less horsepower than a conventional 2-stroke?

quote:
I was not comparing the brand new, modern high tech Evinrude 200 to an old, low tech, carbureted, throwback 2.4 liter Merc 200 from 1986.
Larry, which one of these statements did you mean?
Having replaced a conventional 2-stroke of nearly the same displacement with a DFI 2-stroke, both mounted on the same boat, I can tell you that there is no loss of performance with the DFI, and in fact, the acceleration is better. I just got off the boat an hour ago, and it flat out moves! I'd take that drag race (my E-TEC 200 up against one of Larry's Mercury 200 EFI) any day!

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Author	Topic: Why DFI-Engines Are Less Powerful
L H G	posted 07-23-2009 07:32 PM ET (US) Why do direct fuel injection engines of same displacement usually put out less horsepower than a conventional 2-stroke?
jimh	posted 07-23-2009 07:33 PM ET (US) This topic was introduced into another discussion on a different topic. I have separated it so that it can be discussed on its own.
jimh	posted 07-23-2009 07:35 PM ET (US) I think the premise is flawed here. Can you give an example where a direct fuel injection two-cycle engine has less power than a carburetor two-cycle engine of the same displacement? In my experience the opposite it true. For an example I would cite the E-TEC 250-HP 3.3-liter engine compared to the Evinrude 225-HP 3.3-liter carburetor motor. This example contradicts the premise of the question.
L H G	posted 07-23-2009 08:25 PM ET (US) I'm sure there are exceptions, but the premise is not flawed. I don't know much about Evinrudes, but the 3.0 liter 225's had to be increased 10% to 3.3 liters to get the same 225HP from an E-tec. Mercury 2.5 liters were rated at 200 HP, and actally put out a little more, but they had to go to 3.0 liter block for the 200 Optimax. Highest 2.5 liter Optimax is 175HP. It seems to be the HP at the top end of a given block that suffers, requiring a larger displacement to get the same HP. At the lower end, like the 150's, not a problem. And only lately, newer technology like carbon fiber reeds is being used to boost the HP of the DFI's To get 275 HP out of an Evinrude 250HO, they had to increase the cubes even more. And Mercury had to do this also for the 300 Optimax, where previously the 300 EFI used the 3.0 liter block. So the question is still, why do DFI's require more displacement, and more weight and heavier engines, for the same upper range of HP on a given block size?
jimh	posted 07-23-2009 10:25 PM ET (US) In the OptiMax motors the engine has to run an air compressor. This probably robs some horsepower from the output shaft. The need to run the air compressor is unique to the OptiMax and not typical of every DFI engine. Since the air compressor in the OptiMax is made from a small outboard motor block, you could figure it probably need 3 to 5-HP to drive it. The belt and pulley have some losses, too, which might add more to the power diverted from the output shaft. The DFI engines also generally meet more stringent emission regulations. We have learned from the VERADO engine experience that lowest emission output is not always coincident with most power or most efficiency. Thus we have two factors operating in the typical DFI motor: it has a different fuel induction system and a different emission rating. To conclude that any difference in horsepower output compared to a carburetor motor with high-emission must be due to EFI is to overlook the influence of the emission rating. Lower emission from the engine may be responsible for lower power output per displacement, not the DFI technique itself.
boatdryver	posted 07-23-2009 10:25 PM ET (US) reduced fuel consumption pre cubic centimeter of displacement ? , i. e. less unburned fuel going out the exhaust into the water? JimL
L H G	posted 07-23-2009 11:13 PM ET (US) So Jim, your comment, saying my premise is flawed, is actually the one flawed. Your later comment "Lower emission from the engine may be responsible for lower power output per displacement" is exactly what I was saying. With Optimax, the compressor is an obvious reason, but what is it with E-tec and HPDI? Name me ONE engine, Evinrude, Mercury or Yamaha, where the DFI engine has less cubes than the old fashioned conventional 2-stroke they made at the same TRUE (not decal) HP, or great HP from the same block. I can't find any, except in the lower ranges of a given block where cubes are the same because the block is not being pushed for max output. I'm just talking HP. As an example, could Evinrude have gotten 225 E-tec HP out of your old 3.0 liter 225 block (although the Mercury Optimax does)? Don't think so. They needed 10% more cubes to do it, just like Mercury did for the 300. When it comes to HP, the DFI systems aren't as strong per cubes. Performance wise, the only thing they are better at when compared to EFI or OX66 is fuel economy and a smoother idle.
jimh	posted 07-23-2009 11:25 PM ET (US) There are two assumptions needed here: --that DFI engines are less powerful, which I don't believe is proven yet, and --the DFI is the cause. Low emission engines may be the cause of less power output per displacement. Let me disprove your theory regarding the OMC 225 versus the E-TEC: --the 3.0-liter carburetor OMC engine was available as a 175, 200, and 225-HP model. --the 3.3-liter E-TEC BRP engine is available as a 200, 225, and 250-HP model. There appears to be a completely congruent relationship between displacement and horsepower in both cases: --carburetor 225-HP and 3.0-liter = 75-HP/liter --E-TEC 250-HP and 3.3-liter = 75.8-HP/liter I cannot see how citing this motor provides any manner of proof that the power output form a DFI motor is typically less than a carburetor motor of same displacement. In this case, we can't have exact same displacement, because the DFI motor is not the same. Let's turn to the smaller V6 motors: --2.6-liter carburetor OMC engine was available as a 150 or 175-HP model; --2.6-liter E-TEC BRP motor is available as a 150, 175, or 200-HP model. There appears to be a relation ship between horsepower and displacement that contradicts the fundament assumption that began this discussion: --carburetor 175 and 2.6-liter = 67.2-HP/liter --E-TEC 200 and 2.6-liter = 76.9-HP/liter QED.
Plotman	posted 07-24-2009 12:14 AM ET (US) Nobody uses QED anymore. I miss that.
seahorse	posted 07-24-2009 12:32 AM ET (US) quote: As an example, could Evinrude have gotten 225 E-tec HP out of your old 3.0 liter 225 block? Don't think so. For 1999 and 2000 the Evinrude FICHT put out 225hp out of the standard 3.0L block. In 1991 the block was increased to 3.3L because that year they came out with the 250hp version, and used the 3.3L block for all the rest of the 200-225 V6 models for commonality of parts. In 2008 they came out with a 3.4L block for the 300hp E-TEC. For 2010 both the 3.3L and 3.4L blocks will be in production, but that is subject to change.
David Pendleton	posted 07-24-2009 12:34 AM ET (US) What the heck was the air compressor for?
number9	posted 07-24-2009 12:44 AM ET (US) L H G, Yamaha SAME displacement, not more or less. HPDI is heavier and has their belt driven high pressure mechanical fuel pump. In most cases DFI is used to improve fuel economy and lower emission. The components of a DFI system generally add weight and will rob some power due to increased electrical demand from electric fuel pumps. 10% increase increase in displacement adds little material weight and is a good marketing tool. Since Merc doesn't market any small 2-stokes these days, who makes that compressor for the OptiMax? So to answer your questions, DFIs do not require more displacement. More weight and heavier engines, yes.
jimh	posted 07-24-2009 09:15 AM ET (US) Re OptiMax air compressor: As you probably know, the Mercury OptiMax uses under license the Orbital Combustion Process (OCP) from Australian ORBITAL. The Orbital Combustion Process requires that air at an elevated pressure (or compressed air) be available to be injected into the combustion chamber. In an OptiMax engine the compressed air is supplied from an air compressor that is driven by a fan belt from the main engine crankcase. The compressed air is then distributed around the engine to the air injectors for each cylinder where is it pre-mixed with fuel before the air-fuel mixture is injected into the combustion chamber by a second injector. Or something like that. It's kinda complicated. But, to use the Orbital Combustion Process you need compressed air.
Peter	posted 07-24-2009 09:43 AM ET (US) "I don't know much about Evinrudes..." -- LHG That remains abundantly clear. ;) "In 1991 the block was increased to 3.3L because that year they came out with the 250hp version..." -- Seahorse I think you mean 2001. It would not surprise me if they simple moved the 200+ to 250 HP E-TECs over to the 3.4L platform.
seahorse	posted 07-24-2009 09:51 AM ET (US) Thanks, Peter, That's what happens when I'm up past my bedtime. 2001 is correct
Tohsgib	posted 07-24-2009 10:54 AM ET (US) The fact that OMC has a 2.6L 200hp E-Tec I think "busts" this whole myth. Second, just because an engine goes from 3L-3.3L does not mean larger bore, it could be longer stroke. Lastly, with modern technology if you could make a larger displacement block with the same weight and dimensions of the old one...why not?
L H G	posted 07-24-2009 11:18 AM ET (US) No it doesn't Nick. That weak 200 needs some kind of special valve to even get close to a true 200 at the prop. I don't even think it makes it. I'd put my 2.5 liter 200 EFI's against one of those 2.6 liter 200's any day. Merc's 200 Optimax is 3.0 liters, and to run with it, Evinrude needs a 3.3 liter 200 HO. More cubes in both cases for 200 HP. Since I don't care to know much about Evinrudes, how do the 90 Etecs compare to the old 60 degree 90 2-strokes of the 90's? But I do know the old carbed engine is faster, and puts out a true 90 HP at the prop. People who have repowered here have reported that fact. So DFI technolgy once again is slower and heavier. And in spite of what Seahore and Peter say, I still say Evinrude needed 3.3 liters to get the 225 HP out of the E-tec technology. The OMC 3.0 liter 225 Fichts are the ones that put the company out of business, and not what I am talking about anyway. They are obsolete.
newt	posted 07-24-2009 11:54 AM ET (US) quote: In the OptiMax motors the engine has to run an air compressor. This probably robs some horsepower from the output shaft. This may be a stupid question, but if the air/fuel mixture is compressed prior to injection into the cylinder, than isn't less mechanical energy required of the piston during the compression stroke? I mean, one way or another, the air/fuel mixture must be compressed prior to ignition. Is it reasonable to assume that most of the energy required by the OptiMax compressor would have been expended by the compression stroke anyways?
jimh	posted 07-24-2009 12:29 PM ET (US) Actually, the OptiMax needs even more energy than normal because the compressed air has to be forced into the cylinder as the cylinder is rising and compressing the air in the cylinder. Its a compressor feed into a compressor.
newt	posted 07-24-2009 12:35 PM ET (US) So now you have double compressed air that pushes back on the piston during the power stroke thereby saving on fuel needs. I think the Optimax actually produces more energy than it consumes. :)
newt	posted 07-24-2009 12:44 PM ET (US) All kidding aside, I hypothesize that the net additional energy required by the OptiMax compressor is limited to minor friction, energy conversion, and heat losses due to the added machinery of the compressor. Of course, I know very little about the OptiMax technology, and am basing my entire hypothesis on the principle that energy is neither created nor destroyed.
Tohsgib	posted 07-24-2009 01:04 PM ET (US) Don't look at the compressor like a supercharger. The DFI compressor atomizes the fuel charge into a fine mist that is shot out the injectors. The finer the fuel charge the more efficiently it burns. A supercharger just rams(literally) the fuel and air charge into an engine therfore giving it more hp but less efficiency. The reason superchargers are efficient is bacuase you can make more hp with a smaller displacement and when you don't need the hp, the supercharger is not working as hard. In other words a SC will make 300hp out of say a 3L engine where 300hp naturally aspirated would take a much larger engine with probably more cylinders to produce so they equal out for the most part but weight is much lighter, etc.
Jerry Townsend	posted 07-24-2009 01:12 PM ET (US) There are a few issues involved here - one, as JimH points out, the compressor draws power, but the choice of compression via the piston or a separate compressor is a toss-up - neither are 100% efficient. One obvious unknown - is the fuel/air ratio - and I would bet the farm that the major difference in performance is attributed to a different air/fuel ratio. Each engine is designed to run at a specific air-fuel ratio. And, the engines are quite sensitive to fuel-air differences - well, it significantly alters the combustion process - and that is where the power/energy is developed. ---- Jerry/Idaho
Jerry Townsend	posted 07-24-2009 01:18 PM ET (US) One additional thought - I would fully expect the DFI engine would produce more specific energy - simply because the air-fuel ratio can be more closely controlled than via a carbreater. ------ Jerry/Idaho
number9	posted 07-24-2009 01:19 PM ET (US) Just did a quick research on OPC. It is basically a DFI system that injects fuel into the cylinder close to the spark. From what I read it uses the compressed air at a relatively low pressure to enhance fuel atomization. Fuel and air are mixed at the injector. In contrast the Yamaha HPDI depends upon the fuel pressure and design of the injector. Tohatsu TLDI, Two stroke Low pressure Direct Injection, is apparently licensed by Orbital also. Here's a link that that provides a decent illustration of how the process works. http://www.tohatsu.com/tech_info/brochure_pdfs/2009_brochure/ Toh2009_115.pdf It sounds like a great technology that allows the use of less sophisticated pumps and injectors.
number9	posted 07-24-2009 01:27 PM ET (US) That's OCP and the compressor is driven by a compressor belt not a fan belt. All the fan belts were too long.
L H G	posted 07-24-2009 03:02 PM ET (US) Don't forget also that BAss and Walleye Boats Magazine did their last "shootout" on all makes of 50HP engines, all technologies. The low technology 2-stroke Mercury 50 won, with the 4-stroke Mercury coming in 2nd. Fuel economy, running noise, acceleration and top speed were all a part of the testing formula. The E-tec 50 was a slug at 2nd last, and the slowest in top speed by 5 MPH. A pretty wimpy 50 compared to the top performing low tech Merc. I think that's when Evinrude determined they weren't going to advertize with them any more, and the mag folded!
fourdfish	posted 07-30-2009 11:06 AM ET (US) Again, those Bass & Walleye tests were so flawed they could could not hold up in high school physics lab. They were just OPINIONS like Larrys that Mercs are better. They are folding because they just were not popular enough to print. Merc is the one that cut back on the advertisments and put them in the tank. BRP did very little advertising in that rag. The only DFI engines that could be less powerful than a 4 stroke would be the Optimax. NO PROOF exists anywhere that the DFI E-TEC is less powerful than a 4 stroke. In fact just the opposite is probably true because of several factors such as weight and friction.
andygere	posted 07-30-2009 11:59 AM ET (US) quote: That weak 200 needs some kind of special valve to even get close to a true 200 at the prop. What makes this motor a "weak" 200? It accelerates better than the 2.4L Mercury 200 it replaced, and has the same top end. Does that make the Merc a weak motor too? How would it stack up to something like a 2.5L Mercury EFI? Small displacement (and archaic fuel injection system) probably make that a weak motor too.
L H G	posted 07-30-2009 04:01 PM ET (US) Andy - I was not comparing the brand new, modern high tech Evinrude 200 to an old, low tech, carbureted, throwback 2.4 liter Merc 200 from 1986. I was comparing it to it's current modern day competition. How would it run against the plain, vanilla, Mercury 200 Optimax (not the souped up 200 XS Optimax)? Is the 200 Optimax "weaker", or is the Evinrude 200 "weaker", considering that both cost the same money? Peter here likes to say cubes count. Well if so, Mercury's 200 has them. Would your 200 Evinrude blow away one of my 200 EFI's? Not sure, but not likely. And it probably doesn't matter anyway. Incidentally, I did not start this thread. Jim took it out of context from another discussion I was participating in. Guess he liked the subject.
Peter	posted 07-30-2009 05:28 PM ET (US) "I was not comparing the brand new, modern high tech Evinrude 200 to an old, low tech, carbureted, throwback 2.4 liter Merc 200 from 1986." Really? But this is what YOU asked Larry "Why do direct fuel injection engines of same displacement usually put out less horsepower than a conventional 2-stroke? There were no qualifiers on the question. Perhaps the question only applies in the Mercury world. The conventional 2.6L Evinrude/Johnson engines that preceded the DFIs only made up to 175 HP. On the same block the DFI 2.6L makes up to 200 HP. By all accounts I've read, the 2.6L 150/175 DFI motors are more powerful than their conventional counterparts like the one I have.
towboater	posted 07-31-2009 12:49 AM ET (US) Id like to see what a new etec could do if you removed the muffler restrictions and re programed the fuel/air mix?
andygere	posted 07-31-2009 02:20 AM ET (US) quote: Why do direct fuel injection engines of same displacement usually put out less horsepower than a conventional 2-stroke? quote: I was not comparing the brand new, modern high tech Evinrude 200 to an old, low tech, carbureted, throwback 2.4 liter Merc 200 from 1986. Larry, which one of these statements did you mean? Having replaced a conventional 2-stroke of nearly the same displacement with a DFI 2-stroke, both mounted on the same boat, I can tell you that there is no loss of performance with the DFI, and in fact, the acceleration is better. I just got off the boat an hour ago, and it flat out moves! I'd take that drag race (my E-TEC 200 up against one of Larry's Mercury 200 EFI) any day!