Speculation Alert - possible Harvester Engine Choices

[Harris005]

I'd suggest paying attention to this previous post:

https://scoutmotors.community.forum/threads/speculation-alert-possible-harvester-engine-choices.1085/page-10#post-12287

It contains this handy reference image. It's from Nissan, but all Series Hybrids work like this, but the post also has a nice explanation by a lead engineer:

Tough crowd.

 

[TigerScout]

Air-cooled flat-6 using old 911 castings, haha. No coolant plumbing needed either way, and with no water pump, power steering pump, A/C compressor, etc, it's a compact package. Pretty much just an engine with a big fan on one end and a generator on the other.

I'm not opposed to this. Check my avatar. In fact I have both a 1972 Porsche 2.2 and a 1977 2.7 engine blocks stashed in South Carolina. Hit me up Scout team if you need some pieces to work with.

 

[dearbulls]

Because they pay higher taxes on diesel fuel. This is why diesel is more expensive than premium in some states.

Do the math and see how many gallons you had to use for that much of taxes. In GA for example, my wife's EV pay 212 extra tax each year, that's equals to 5 years of gasoline use on my Maverick hybrid.

 

[dearbulls]

I've had to work my way up to it. And ask around, I still screw up the units .

So, here is how it maths. Sorry, words alert.

If we know that its 2 miles per KWh, then to go 500 miles, we need 250KWh of energy. And with the Harvester, we know we start with ~75KHw in the battery. That means we need to generate the other 175KWh of energy with the Harvester generator. But its how we do that that matters.

If we do the "start the generator the moment we leave, and let it slow down our battery drain", we don't need a huge generator.

500 miles at 70mph, is a smidge over 7 hours (70mph x 7hrs = 490 miles). Which means in theory we only need a generator to provide 25KW per hour, to keep up with that (7hrs x 25KW = 175KWh). That is a pretty small generator. Like the BMW i3 REX used a 0.6L motorcycle engine, that produced that much.

Alternatively, if we know that we have the "2 miles per KW" efficiency at 70mph (estimate, but makes for easier math), that means in an hour, we've gone 70 miles, but also used 35KWh of energy (70 miles/2 miles per KW == 35KWh). So on flat ground, we'd need a generator that can produce at least 35KW of output to keep up with 70mph cruising.

That said, the 35KW is the NET amount of power we need from the generator, not the gross. This is because there are electrical inefficiencies (converting the power). And obviously if you want to go up a hill, or tow, that number is going to increase. But the math says that in theory, in perfect conditions, you don't need a "huge" generator to slow down the drain.

Now, I think they're not going to design for flat ground, and I think they're "more likely" going to be doing something closer to the "gas and go" approach for the harvester. Which means I'm personally thinking the Traveler will be getting something more in the ~80-100KW output range myself, but thats totally speculation.

The Ramcharger is using a 130-190KW V6 as its generator. They're clearly getting it set to tow.

And also, to create a constant 35kw (without towing), you'll want bigger engine so it doesn't rev to 5-6k RPM to give you that 35kw. You'd want something capable of 90kw then run it at 1500-2000rpm to generate 35kw, for the NVH experience of the passenger

 

[dearbulls]

I should point out that 150 miles of battery range doesn't necessarily reflect on the battery size. There could be conditions where the engine/generator kicks on to start "extending range" before SOC reaches 20%. Make sense?

That will require a gas engine powerful enough to both maintain the energy loss on keep the vehicle going, and still have extra energy to charge the battery. If that's the case, then all discussions in this post would be solved.

 

[dearbulls]

Oh, one more thing I noticed yesterday while responding in yet another thread about this (but putting the thought here, as its larger/has more eyes).

We've all been theorycrafting about the engine sizes for the Harvester. And we've been comparing it mostly to the BMW i3, Chevy Volt, and upcoming Ram Ramcharger. The general consensus seems to be that the i3 REX had too small of generator, and that the Ramchargers 3.6L V6 is too large for packaging/placement in the rear of the vehicle, so maybe something between those makes sense.

In all of that, I had forgotten that the Ramcharger had a much higher towing rating than the Scouts are projected to have, at 14,000lbs. This is a full 40% higher than the Terra (10,000lbs), and ~87% higher than the Traveler (7,500lbs).

The Ramchargers 3.6L is rated for 174HP continuous output, with up to ~255HP under peak load.

If you try to use that, to help predict what power/size of engine you'd need for a Scout Generator, it is actually pretty helpful.

If you reduce the Ramchargers 174HP by 40%, you end up with ~105HP (174hp x 0.6 ~= 105hp, and max load of ~255hp x 0.6 ~= 153hp ). If you do it by displacement (not a great metric, as engines are not the same efficiency), then you get something a smidge over 2L. (3.6L x 0.6 = 2.16L).

I'm hopeful that this improves the chances that we'll see a generator that can handle the electrical load under a larger variety of use cases in the Scout. As while I know things don't scale perfectly like the math above, the difference in towing ratings was big enough that I thought it should be called out, because it does materially change the needed output for the vehicle, and therefore it does potentially change the packaging constraints quite a bit.

This sounds more like turbo charged EA888 then.

 

[DBHowe]

Why you ask? Great question... It's simple.

Because the Harvester motor will be quite small relative to the size of the battery pack and small relative to the size of the truck and its curb weight. And, if you go by CarTEchGeek and the i3 example, then you are essentially using a scooter battery (34 HP) to send power to a motor directly. Yes, 34 HP!

This is also why Scout has a stake in the sand and has stated a 500 mi estimated RANGE for these vehicles (which is absolutely phenomenal BTW). All the naysayers wants to be able to drive for 15 hours straight without stopping for gas or energy. Why they want to do this type of torturous driving, I dunno. That's not for me, and I am perfectly happy to stop, charge, pee and eat while road tripping. Right now there is not a nuclear-optioned Scout to drive for ever.

Now, if you want to take away the EV benefits (including HP, instantaneous TORQUE and all of the additional storage space Scout has planned for everyone), then you could put a giant V6 in the frunk and build a RAM and pretend its an EV. Or you could put a Scooter motor in and skip the whole battery thing.

Even if you went full MAD MAX and filled the bed with all the gas from GAS TOWN, you would be pulling MORE WEIGHT and you would not recoup enough energy to drive for 15 hours at HWY speeds. The truck would simply consume more than it receives from the Harvester. Again there is a stated range of 500 for a reason.
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I'm not a fan of the square headlights! *grin*