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Discussion Starter · #1 ·
Since buying my Promaster, and being a little disappointed about fuel consumption, I have wished there were some easy low-cost way to turn it into a hybrid. (Of course, there isn't.) I have wondered if there were some sort of aftermarket hub-motor wheel that could be purchased to give a low-speed boost for city driving, but I haven't found anything like that. Recently, when Obrian posted this picture of the rear drive train of a 4WD Ducato(?), I began to imagine a new hybrid approach.



What if one of the 4WD rear wheels and axles were used on a Promaster and, instead of being connected to a differential and drive shaft, it were connected directly to an electric motor. It could generate power (to an auxiliary battery) on braking and it could supply power from 0 to ~30 MPH, when the engine typically gets 4-10 MPG. Of course, power could be supplied to both rear wheels, but I'm just trying to envision a way to reduce gas consumption at a minimal cost. Making it cooperate with the other systems of the vehicle would probably be a headache for the software engineers, but it seems possible. Imaginary now . . . maybe we'll see something like that in the future?????
 

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Sure you could but consider an alternative. Diesel- cheaper, clean, 27mpg, pays for itself, no smoke, no soot, no smell. I LOVE it!
 

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Discussion Starter · #3 ·
At the time when I purchased, the overall costs/benefits of gas and diesel models seemed like kind of a toss-up to me. I could have gone either way, but a gas model was available at a good price. I'm not convinced about the cleanliness of diesel after VW's software tricks. In any case, for short trips and urban driving (my typical use) I think hybrids are hard to beat.

I just noticed that the idea of a Promaster hybrid was discussed in another thread a couple of days ago. I didn't see that thread before I posted, but I think a lot of people would be happy to see a more fuel-efficient version of the Promaster.
 

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At today’s diesel prices I’m thrilled to have a gasser every time I fill up;)
 

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Back to the Hybrid .... It really makes sense to do that in a truck as there generally is room for batteries and the weight would be no problem. Many are used for short runs between places in town too. My friend's new Jeep AWD (something) SUV has start-stop built in for stoplights too. That we could have today.
 

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It could generate power (to an auxiliary battery) on braking and it could supply power from 0 to ~30 MPH, when the engine typically gets 4-10 MPG.
What do you base these numbers on? I mainly drive at highway speeds, but my city mileage seems better than this. My experience is mileage is generally poor when the engine is pushed hard at high speeds and uphill climbs.

Per an imagined hybrid, passenger hybrids are highly tuned and refined affairs relying on many tweaks that are antithetical to truck use. (CVT, Atkinson cycle engines, low drag coefficients and rolling resistance, etc) While you see a number of SUV and Crossover hybrids, I'd lump these under the category of glorified passenger vehicles.

There are few pickup and truck hybrids and my guess is this is for various reasons: not a consumer or government (eg. CAFE) priority, available Diesel options (more common and refined for the Ducato platform in Europe), low volume sales, engineering challenges, etc.
 

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Hi,
We did our conversion rather than going with a commercial RV primarily to try and get a high mpg RV out of it. I was hoping for low 20's but go 19 mpg as the average of our road trips. A little less than our target, but nearly twice what our last 3 RVs got.

It would be nice to have the benefits of a hybrid, but I think Ziggy is right -- there is a whole lot of optimizing going on in the design of a good hybrid. We are on our 2nd Prius and its just amazing how many thinks they put together to get that 50 mpg - it gets into pracitally every detail of the car.

It would be great to get a little more mpg, but I think the hybrid conversion might turn out to be a lot of work for not a whole lot of return.

I'd just feel good that you are getting better than twice the mpg of the average RV out there :)

Gary
 

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Discussion Starter · #8 ·
What do you base these numbers on? I mainly drive at highway speeds, but my city mileage seems better than this. My experience is mileage is generally poor when the engine is pushed hard at high speeds and uphill climbs.
OK . . . here comes my uneducated, unqualified speculation :D :

When I watch my instant fuel economy reading as I accelerate from a stop, the readings are something like this:
1st gear - 5 mpg
2nd gear - 7 mpg
3rd gear - 10 mpg
4th gear - 13 mpg
etc.

That high fuel consumption is partly a matter of the energy required to put ~6,000# into motion, and partly a matter of gear ratio (feet moved per rotation of the engine). I agree that high speeds and hills burn a lot of gas. Accelerating from a stop puts a similar demand on the engine to climbing a hill (compared to cruising at a steady speed). Since DC motors function well under high torque, the low speed range seems like an area where there might be a good cost/benefit ratio for supplemental electrical power. For brief supplemental power, huge batteries would not be required.

Perhaps the mild hybrid approach that Chance discussed in another thread is more cost effective than adding any sort of rear wheel drive system(?). It just looks to me like adding an electric drive to one or both rear-wheels might make sense, since some of the parts are already in production for the 4WD Ducato.

I agree that trucks present some different considerations from cars in considering hybrid systems or other gas-saving measures. On the other hand, nudging a truck to get 20 mpg instead of 18 mpg has a bigger impact than tweeking a car to get 42 mpg instead of 40 mpg.

While you see a number of SUV and Crossover hybrids, I'd lump these under the category of glorified passenger vehicles.
True.
 

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Discussion Starter · #9 ·
Hi,
We are on our 2nd Prius and its just amazing how many things they put together to get that 50 mpg - it gets into practically every detail of the car.
I agree that a true, optimized hybrid vehicle is a complex tangle of design/engineering choices. We have a Prius too. Maybe that's part of the reason it is so painful for me to see that readout in the Promaster telling me that I'm getting less than 20 mpg. :laugh: A big factor for me in choosing the Promaster was the fact that it consumes less gas than the other options I was considering to meet my needs.
 

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When I watch my instant fuel economy reading as I accelerate from a stop, the readings are something like this:
1st gear - 5 mpg
2nd gear - 7 mpg
3rd gear - 10 mpg
4th gear - 13 mpg
etc.
I had this option for a short while, but it went away after replacing my bone stock radio. Not sure if I can get it back, but I decided I'm probably happier not knowing (I calculate MPG by the tankful). I'm not sure how accurate or helpful instantaneous "gamified" MPG readings are, but it's fun to watch on the SO's Prius C.

I agree that trucks present some different considerations from cars in considering hybrid systems or other gas-saving measures. On the other hand, nudging a truck to get 20 mpg instead of 18 mpg has a bigger impact than tweeking a car to get 42 mpg instead of 40 mpg.
Yes and this factors into the fleet CAFE numbers and is actually an impediment to developing hybrid trucks, if I understand correctly.

Much cheaper to get 1-2 MPG incremental improvements on trucks by conventional means rather than going full-hybrid and it has more impact on your fleet score. So you get things like aluminum hoods and beds, smaller more efficient engines, "EcoBoost" turbos etc.
 

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Discussion Starter · #11 ·
Much cheaper to get 1-2 MPG incremental improvements on trucks by conventional means rather than going full-hybrid . . .
I think it is great that manufacturers are scouring their designs for opportunities to improve fuel economy through "conventional means". The simpler the solution, the fewer the unintended consequences (such as environmental problems related to lithium batteries).
 

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OK . . . here comes my uneducated, unqualified speculation :D :

When I watch my instant fuel economy reading as I accelerate from a stop, the readings are something like this:
1st gear - 5 mpg
2nd gear - 7 mpg
3rd gear - 10 mpg
4th gear - 13 mpg
etc.

.....cut.....
As others have stated, the above data is meaningless on a practical basis. At "0" MPH, for example, MPG is zero, right? At very low speeds while accelerating MPG whether fuel or electric-equivalent will be very poor.

Many FWD-based AWD electric hybrids I've seen have gone with a high-speed motor with gear reduction, powering through a differential and delivering power to rear wheels through half shafts. To me that seems an easy way to keep it simple, low cost, low weight, and improve fuel efficiency.

A DIY modified ProMaster hybrid would likely never have an acceptable return on investment in my opinion.
 

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P.S. -- A Honda Accord-type hybrid which eliminates the mechanical transmission altogether may be another good option for a future PM van.
 

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Discussion Starter · #15 ·
As others have stated, the above data is meaningless on a practical basis. At "0" MPH, for example, MPG is zero, right?
I assume that the readout is not precise, but I also assume that it gives a general indication of consumption. It seems useful for thinking about one's driving habits.

At very low speeds while accelerating MPG whether fuel or electric-equivalent will be very poor.
That's why low speeds seem to me like the most advantageous time to use energy reclaimed from braking.

Many FWD-based AWD electric hybrids I've seen have gone with a high-speed motor with gear reduction, powering through a differential and delivering power to rear wheels through half shafts. To me that seems an easy way to keep it simple, low cost, low weight, and improve fuel efficiency.
I wasn't aware that was being done. I think you know a lot more about this than I do.

A DIY modified ProMaster hybrid would likely never have an acceptable return on investment in my opinion.
Ha-ha. I'm not interested in taking this on as a DIY project. I'm just intrigued by the possibilities.
 

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The new Pacifica hybrid uses a version of the Pentastar engine connected to the dedicated hybrid transmission, but it fits in the same space envelope as the conventional transmission on that van. I think the subframe was modified (a customer of mine fabricates the subframe for those vans!). I don't know the details of the modification, but it's likely to involve different transmission mounts and it's unlikely to be rocket science. Front-drive only on that.

Obviously the vehicle has a battery pack underneath. No Stow'N'Go seats on the hybrid because the battery pack ate up that space.

Now, as for the original poster's idea ... You do not want to drive just one wheel. But even better, obtain the complete 4wd rear suspension and the diff and halfshafts, and use the motor-generator to turn the input shaft of the diff (in place of the driveshaft). Bingo, rear wheel drive in EV mode, with both rear wheels driving, just as they should.

The challenge with ANY of this, is integrating it into the powertrain such that it all fits and works correctly and is safe.
 

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To keep weight and size down, electric motors are often designed for high speed with a fixed gear reduction before output goes to wheels. This particular unit is supposedly 60 kW, 240 nM, and has 10:1 reduction, so approximately 2,400 nM going to wheels.


One disadvantage of motors at wheels is that they add to unsprung mass. Obviously packaging and cost are probably better, but chassis mounted motors may make more sense in some circumstances, like when using large and heavy motors for greater power.
 

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As a very enthusiastic owner of a used Chevy Volt (2012; purchased for $12k; loaded with 60k miles - which is easy to duplicate via Autotrader etc) I can feel your pain about marginal economy of our vans (at least gassers), especially for urban driving. Kinda amazing no company has gotten serious about a hybrid or electric van in the US (even a PMC size) given that urban driving in delivery vans would be a great application of hybrid or electric drivetrain. (I did see Nissan NV200 electric rigs in New Zealand). A few years ago I drove an electric Ford Transit Connect that was for sale in Denver - it was impressive - but the lack of service/parts on that non-mass produced rig was non-existent and scared me away.

Just for fun I have zeroed out my electronic MPG reader on my gasser PM during winter driving for short trips in town and it can easily be below 10 MPG (including a brief warm-up, wasteful idling at stop lights etc) when I return. That is why whenever possible I take the Volt and go electric. Once you get used to the efficiency, instant torque, smoothness, and especially the regenerative braking of an EV it is hard to go back to a gasser. So yeah, lets see an EV/hybrid Promaster etc!
 

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Discussion Starter · #20 ·
Now, as for the original poster's idea ... You do not want to drive just one wheel. But even better, obtain the complete 4wd rear suspension and the diff and halfshafts, and use the motor-generator to turn the input shaft of the diff (in place of the driveshaft). Bingo, rear wheel drive in EV mode, with both rear wheels driving, just as they should.

The challenge with ANY of this, is integrating it into the powertrain such that it all fits and works correctly and is safe.
I agree that driving both rear wheels would offer better handling, traction, tire wear, etc. I just tossed out the idea of single wheel drive as a simple, low-cost approach with known compromises. I also agree that a fully integrated, well designed hybrid system is best, and mixing two drive systems presents numerous safety issues.
 
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