Fritz
Active Member
No, no, no, no, prices go down when the patents wear out!
Toroidal propellers: gas burn reduction potential?
- Thread starter pescador
- Start date
kaelc
Well-Known Member
I think price will come down as other manufactures try new prop designs that compete. They mention it was a drone prop design this is based on. Here is a video showing another propellor design that lowers noise and likely energy consumption. The biggest take away is competition creates competition and innovation. This is why I love capitalism combined with the socialism that educates many engineers
Sharphooks
Well-Known Member
Yes....you’ll start seeing more interesting results....
Interesting.
Still not running in a range where the eco enertia is at its best but that's a slightly better comparison than the previous. The eco enertia is more for getting substantial boats on plane and offering good mid range economy. Not so much for go fast boats. These numbers suggest there's better Merc props for the hull than the enertia eco. The big fountain on our dock for instance does not do well with the ecos and sees better numbers with other Merc props. That's the only hull I can think off thats around me (tripple 300) that's somewhat similar to the test hull.
Still reasonable to expect improvement where most of us run our boats anyhow. Look forward to seeing these around the docks in the next couple years and getting some honest feedback.
Thanks for posting sharphooks.
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ship happens
Well-Known Member
Notice how there's no RPM on that graph
Why would rpm matter? You know the speed, you know the fuel economy? How does adding rpm to the equation shed anymore light?
There are concerns that some of the best gains are at lower than optimal RPMs and lugging the engines.
Sharphooks
Well-Known Member
ship happens
Well-Known Member
That makes more sense. In the nominal cruising speed /rpm range it's super minimal. That's where you want the engine to be. In its power ban. Singing songs. That RPM range is between 38 and 42 imo
Squire
Well-Known Member
This was my conclusion when I started a thread on these props last year; not enough gains in my optimum cruising range to justify the investment. At the time I figured 500-600 hours just to pay for the difference in price over my Powertech OFS4 spun at 3800 rpm by a Yamaha F300.
BC Coast Pilot
Well-Known Member
Eco.....Eco Enertia......
kaelc
Well-Known Member
Was going to tag you, you called it. I'm drooling over Mercury engine price cuts and some dealerships experience with their prop lines. Proven over promises go a long way when fuel is between 1.50 and 2.50 a litre.Eco.....Eco Enertia......
Max123
Well-Known Member
@ship happens - I'm curious, you mention RPM as the critical missing piece of information. I don't think fuel economy is neccesarily fixed based on rpm. The fuel injector can increase the volume of fuel sprayed irrespective of RPM. In a boat this isn't very pronounced since you only have one gear, however think about a car travelling at a constant speed in 1st gear @ 4000rpms vs the same car in 4th gear @ 4000rpm. The fuel injector is spraying a way higher volume per revolution at 4th gear due to the increase in load. Fuel injector spray volume is based on load and rpm to calculate pulse width (amount of time injector is open). In a boat, load would typically always be the same at a given rpm and your rule would hold true - unless prop slip has changed.
I think about it like this:
There are 3 variable: 1) Engine Power output, 2) peak engine efficiency 3) prop slip. Each of these variable is on a curve. At the point where all three curves intersect, you are in the sweet spot. In an ideal world, the the output/efficiency curves wouldn't just intersect, they would overlay exactly, and prop slip would stay constant.
I suspect that what we are seeing with the sharrow prop is a legit technical innovation, and it definitely seems to reduce slip across the rpm band - but particularly at low RPMs. Essentially allowing you to go faster and start loading up the motor at a lower RPM where the motor may also be in a more efficient part of its power curve. At some point the sharrow and the traditional more of less line up. In the example above, there isn't much difference at 5000rpms - but the sharrow prop seems to reduce slip across the entire range, which is a definite innovation - meaning you have a wider range of optimized speeds.
Anyway, I am curious if loading the engine up at lower rpm has any negative effects on the powerhead - essentially 'lugging' the engine. Also, I suspect some engines respond better than others - (for example SOHC, vs DOHC, vs forced induction).
I think about it like this:
There are 3 variable: 1) Engine Power output, 2) peak engine efficiency 3) prop slip. Each of these variable is on a curve. At the point where all three curves intersect, you are in the sweet spot. In an ideal world, the the output/efficiency curves wouldn't just intersect, they would overlay exactly, and prop slip would stay constant.
I suspect that what we are seeing with the sharrow prop is a legit technical innovation, and it definitely seems to reduce slip across the rpm band - but particularly at low RPMs. Essentially allowing you to go faster and start loading up the motor at a lower RPM where the motor may also be in a more efficient part of its power curve. At some point the sharrow and the traditional more of less line up. In the example above, there isn't much difference at 5000rpms - but the sharrow prop seems to reduce slip across the entire range, which is a definite innovation - meaning you have a wider range of optimized speeds.
Anyway, I am curious if loading the engine up at lower rpm has any negative effects on the powerhead - essentially 'lugging' the engine. Also, I suspect some engines respond better than others - (for example SOHC, vs DOHC, vs forced induction).
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ship happens
Well-Known Member
I can tell you've thought about this and done your homework. All great questions.
It's a great topic, and one I think there's alot to learn about for sure. I think if the engine is propped right, the OEM engine builders are very accurate with how much fuel they know it will burn at whatever RPM. Id also add that most boats are NOT propped for their best performance in the big picture so, I think theres also that to consider. I think with these props you can gain some efficiency for sure, I just think its not as much as they claim and im putting my money on they compared it with stuff that wasnt right in the first place or could have been alot better. Because your right its prop slip in the end. However that being said Lets go back to RPM real quick. Burn less RPM you burn less fuel. This is not an opinion its a fact. One that is not considered most the time. Especially when dealing with outbards, because they are compact, and they dont start making their torque usually until 4 grand ish. Not saying im 100 percent right, im just a mechanic boat builder who considers the facts and i'm always learning too. Those facts i consider to be fundamentals, because HP equals fuel burn and engine temp. You have your temp, fuel and RPM, that determines how much HP you have outside the crankshaft of that engine. In any combustion engine.
End of the day theres an issue and thats who wants to drive their boats at 40 MPH around here? Maybe on a perfect day but when does that ever happen on a regualar basis? So if these props get you in fact the percentage of fuel savings they are claiming then you would have to be doing 30 MPH at 3000 RPM.
I phone the company and talked with the rep about this and he didnt have an answer for me nor did he understand what I was asking. Nice guy for sure. Id like to see a side by side comparison. Same boat, same everything just the best wheel against one of these and see. I think thats how we get to the bottom of this. Then theres the fragility of these to also consider.
You really would have to get the dyno sheets and compare all the various OEM engines within the same class and compare apples to apples I guess. Thats a long conversation
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