Diesel Electric Propulsion

[socaldmax]

Originally Posted by DeepFrz

I notice that the new Common Rail engines from Yanmar have a very flat torque curve compared to older engines. I would assume that is the same for all Common Rail engines.

I'm not sure, possibly.

I have 3 reservations about common rail engines and they might not be an issue in the new Yanmars, but they were with the truck diesels.

1. They run at extremely high fuel rail pressure - 33K to 39K psi. That's almost as high as water jet cutting which runs at 40K - 94K psi and those are designed to cut through steel very efficiently. Even the slightest bit of particulates in the fuel will erode the injector passages causing them to dribble and burn holes through pistons - always under load. I'm on Duramax engine #3, and that's with 2 additional filters in addition to the stock filter.

2. Part of the allure of a common rail system is it gives the mfr or engine tuner very fine grain control over injector pulse volume, timing and width. They could also theoretically inject a series of short pulses over the duration of the combustion cycle and produce a long duration flame front (more power) yet without injecting fuel for the entire duration. Essentially a "hollow" fuel pulse that could save considerable fuel while providing equal or better power.

Instead, they chose to come up with "pilot injection" which is a small pre-pulse designed to gently push the piston and rod down onto the crank before the main injection pulse which drastically reduces the diesel "rattle" sound, but consumes fuel in the process. In the truck versions built since 2011, they've also added exhaust emissions regen, in which the computer injects extra fuel into a soot filter that's been trapping soot for a period. This creates extremely high exhaust pipe temps and burns even more fuel.

The net result is the potential was they could have provided a 1 ton truck that could get 21-22 mpg on the fwy. Instead, a stock 2002-2010 will get 16-18 mpg. A 2011 with the emissions regen will get 13-15 mpg on the fwy. Aftermarket tuners can modify all of that and give you a quiet truck with 21-22 mpg and virtually no smoke with more power, but I doubt they'd get into a small niche like yacht engines. I think you're going to see fairly disappointing fuel economy, especially compared to the promised potential of common rail.

3. Common rail injection is patented by Bosch, all of the light duty truck brands are using Bosch injection systems and injectors. Bosch isn't shy about bending people over for parts. A set of Bosch rebuilt injectors from the Chevy dealer is $4,000 for the set of 8. That's the best you can get. New ones are installed into new engines at the factory, rebuilt ones are sold at the parts counter. Aftermarket sources can get you the same injectors for about $1700 a set, but still, that's a lot of coin. The injection pump is allegedly $4,000 from the dealer as well. Since 2002, I've gone through 4 sets of injectors and 1 injection pump and I have another set of injectors to replace right now, which is a major ordeal. Keep in mind, my fuel is triple filtered.


I'm not saying that common rail injection is the devil, but my truck has been on a flatbed so often I've got all of the towing companies on speed dial. ALL of the problems have been either injector or injection pump related. Meanwhile, my 1984 Toyota Corolla diesel with mechanical injection starts right up and runs and always makes it to the auto parts store to pick up more parts for the $38,000 lemon. I mean truck.

[BigBeakie]

Back to EP matters for a moment, I just became aware of an electric conversion on a Leopard 40, using OceanVolt SD15 motors. The equivalent HP of those is about 20 HP diesels.

The boat now gets the same maximum hull speed as it used to get on 30HP saildrive diesels running WOT, using 75% power on the SD15's.

Let me repeat that so it is clear for those that had comments on this aspect of EP earlier in the thread ie that smaller electric motors can do the same work as larger ICE engines....

Actual on water data shows that smaller HP electrics running at 75% of full power give the same performance as larger diesel engines running at 100% power.

[tdominic_97]

I am trying to follow this, but I get more lost the more I read. How can the horse power of an electric motor and a gas or diesel motor be compared without knowing the torque or rpm of them. The electric motors of the same hp can't be compared without rpm or torque. If someone can clear this up. I would appreciate it.
Thanks,
Tom

[cwjohm]

I am trying to follow this, but I get more lost the more I read. How can the horse power of an electric motor and a gas or diesel motor be compared without knowing the torque or rpm of them. The electric motors of the same hp can't be compared without rpm or torque. If someone can clear this up. I would appreciate it.
Thanks,
Tom

Tom

You are correct. The problem with cruisers forum is that posters conflate many issues into the one argument and confusion results.

Actual on water data shows that smaller HP electrics running at 75% of full power give the same performance as larger diesel engines running at 100% power.

You cannot make this statement absolutely. It depends on the diesel and electric motors you are comparing.

However, given this issue really has nothing to do with the argument postulated by the OP we can assume that the statement is reasonable. I doubt anybody would really have an issue with this assumption as a precursor to a reasonable discussion on the subject.

On the other hand I would take SERIOUS issue with equivalent 20Hp diesels on a Leopard 40. I would not venture out without at least 40HP, which by your equation would point to 30HP electric motors.

Again, looking at battery sizing, motors, and generator and you are at 3 times the cost of diesels.

The thrust of your argument is that if you are prepared to seriously underpower your vessel you can get EP for a similar cost to the correctly sized diesels. This is true but quite unsafe, but of course you will once again designate this as FUD.

[DeepFrz]

I was thinking, and this is just an idea, that 30hp diesel motors through sail drive units are probably losing quite a bit of their power in the drive train. Couple that with the fact that engine shaft hp is less than advertised and maybe a 20 hp electric motor is delivering more power to the prop shaft than the 30 hp diesel.

[Stumble]

Originally Posted by DeepFrz

I was thinking, and this is just an idea, that 30hp diesel motors through sail drive units are probably losing quite a bit of their power in the drive train. Couple that with the fact that engine shaft hp is less than advertised and maybe a 20 hp electric motor is delivering more power to the prop shaft than the 30 hp diesel.

Not quite.

The Volve D1-30 saildrive has a rated 28hp at the shaft, and 27hp at the propshaft. Obviously there ar some friction losses, but they really aren't that much. And I am not sure it matters, even if you are going to install an electric drive, you still need the saildrive to connect the motor (of either type) to the prop.

[valhalla360]

Originally Posted by BigBeakie

Back to EP matters for a moment, I just became aware of an electric conversion on a Leopard 40, using OceanVolt SD15 motors. The equivalent HP of those is about 20 HP diesels.

The boat now gets the same maximum hull speed as it used to get on 30HP saildrive diesels running WOT, using 75% power on the SD15's.

Let me repeat that so it is clear for those that had comments on this aspect of EP earlier in the thread ie that smaller electric motors can do the same work as larger ICE engines....

Actual on water data shows that smaller HP electrics running at 75% of full power give the same performance as larger diesel engines running at 100% power.

Source? Conditions? Etc...

Boasts at the bar after a few too many don't count. Also, as stated before I'm not taking marketing propaganda at face value.

If I was marketing the system and was a little easy going with the honesty, I could come up with a scenario that fits with your description.
- Take the diesel out on day with 30kt winds bashing into 6fters and you are full throttle to get up to hull speed going dead into the wind.
- Take the electric out on a dead calm day or with a bit of a tailwind and you can probably make hull speed with 30hp.
- Forget to mention the conditions just that it took all the diesels had and the electric motors had no problem.
- Was the hull and prop clean and in good condition for both tests.
- Were these two identical boats loaded identically? I know I lose about a 1/2kt at the top end when I'm loaded for cruising. Doesn't sound like a big deal but when you are talking running at hull speed, getting an extra 1/2kt thru brute force will use a lot more HP.

Forgive me if I'm skeptical.

[BigBeakie]

CW,

Couldn't agree more that the 30HP on the Leopard 40 are undersized for challenging conditions that may be experienced by cruisers.

However the point of my post is just some evidence given to me by a senior executive of an EP technology company for a known boat.

And yes, the data were gathered with due considerations for the sea state conditions. It was a conversion, so the SAME boat.

But I suppose there will have to be video evidence of such, with affidavits sworn by an Archbishop.

[valhalla360]

Originally Posted by BigBeakie

CW,

Couldn't agree more that the 30HP on the Leopard 40 are undersized for challenging conditions that may be experienced by cruisers.

However the point of my post is just some evidence given to me by a senior executive of an EP technology company for a known boat.

And yes, the data were gathered with due considerations for the sea state conditions. It was a conversion, so the SAME boat.

But I suppose there will have to be video evidence of such, with affidavits sworn by an Archbishop.

So we are hearing this 3rd hand from the guy selling electric motors.

Yeah, I'll take what they say with a huge grain of salt when they claim things that don't line up with basic physics.

[BigBeakie]

Originally Posted by valhalla360

So we are hearing this 3rd hand from the guy selling electric motors.

Yeah, I'll take what they say with a huge grain of salt when they claim things that don't line up with basic physics.

Valhallal

Oh it will be so sweet when you apologise to the forum for questioning the integrity & ethics of someone you have no information whatsoever about simply based on your cynicism and naive scepticism.

You probably bought some dodgy product off late night TV con ads, and now everyone is out to get you with their lies and false advertising. Just curious, are there any products out there that actually work and do what their evil marketers say they do, or is everything just bunkum to you?

And like you can make claims about the physics, yeah right. Could you enlighten us with your technical qualifications in this field?

[valhalla360]

Originally Posted by BigBeakie

Valhallal

Oh it will be so sweet when you apologise to the forum for questioning the integrity & ethics of someone you have no information whatsoever about simply based on your cynicism and naive scepticism.

You probably bought some dodgy product off late night TV con ads, and now everyone is out to get you with their lies and false advertising. Just curious, are there any products out there that actually work and do what their evil marketers say they do, or is everything just bunkum to you?

And like you can make claims about the physics, yeah right. Could you enlighten us with your technical qualifications in this field?

So far we have nothing but your fourth hand claims that conflict with basic physics. Hardly naive scepticism.

My background is in engineering but this is basic physics. If these systems were half as great as you make them out to be, diesel powered boats would have been gone a decade ago.

[darylat8750]

We have to remember that all engines and motors can be rated several ways. In diesel prime motive boat engines they typically use one of the M1, M2, M3 or M4 ratings. (For instance the John Deere 4045 engine is available with HP ratings from 67HP to at least 159HP. It will produce 67HP for around 20,000 hours before needing major work.) Electrical motors can be rated for various uses also. If a motor is designed for and rated at a power that it can sustain 24-7 for months at a time in an industrial setting it may seem like it has more power per rating than a ICE that is rated at M4. If you develop that motor for drag racing and expect it to melt down if you try to operate it longer that 13 or 15 seconds at a time MUCH more power could be extracted from that unit. Obviously the motors we are interested in fall somewhere in between these extremes but lean towards the reliability end of the scale. Electric motors and ICEs have an operating speed that is most efficient use of energy. Transmission ratios are available to turn any motor or engine rpm into the rpm that will be suitable for the desired work.

Horse power is horse power. I see several times in this thread where it is said that torque is what moves something. Torque is force, not power. X foot pounds of torque is just pressure. Without movement no work is being done therefore no power is produced. Transmissions are routinely used with electric motors as well as ICE. In boat use it is easy to design a motor that is efficient in the rpm range that propellers are efficient.

[skipmac]

I have seen several posts that agree with my claims that going electric will cost at least double and more likely triple the cost of diesel.

BUT I have never seen any one address this question. Why is a "marine" electric motor so damn expensive?

A new +/- 60 HP electric motor/generator for my Prius is under $1000. I can buy retail a 60 HP industrial motor for around $2000.

So how come a 60 HP marine electric is $10,000 or more?

I understand Toyota builds thousands and thousands of motors but that certainly does not account for such a huge discrepancy.

[nimblemotors]

Because if you sold one, you'd spend your entire life explaining why someone should buy it, and not just collect the sales price and rinse and repeat.

Originally Posted by skipmac

I have seen several posts that agree with my claims that going electric will cost at least double and more likely triple the cost of diesel.

BUT I have never seen any one address this question. Why is a "marine" electric motor so damn expensive?

A new +/- 60 HP electric motor/generator for my Prius is under $1000. I can buy retail a 60 HP industrial motor for around $2000.

So how come a 60 HP marine electric is $10,000 or more?

I understand Toyota builds thousands and thousands of motors but that certainly does not account for such a huge discrepancy.

[skipmac]

Originally Posted by nimblemotors

Because if you sold one, you'd spend your entire life explaining why someone should buy it, and not just collect the sales price and rinse and repeat.

Perhaps all to true.

But on the other hand, sell one for a reasonable price and you might not have to spend so much time explaining and justifying the sale.