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Old 03-16-2017, 12:36 PM   #21
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Given the HP/torque numbers you provided (specially for when the batteries are discharged), I'd say just keep your X5 diesel. I doubt you'd be happy towing in the mountains with less HP/torque.

Also, selling your X5 diesel is not going to help the environment as someone else will be driving your X5 diesel. A 5 year old X5 diesel is not heading to the junk yard. It has at least another 10 years left in it.

Finally, with the amount of money you have to pay to upgrade, you can buy a very efficient new car (say a Nissan Leaf or Toyota Prius) to use as your daily driver. You can then keep the X5 diesel for just towing duties. Not sure if having 2 vehicles is an option or not.

Good luck!
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Old 03-16-2017, 03:40 PM   #22
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Our second car is a Mazda Miata Special Edition, in British Racing Green (2001). We find ourselves driving this very little, except for shorter trips on top down days. It is almost a collectors item, and i am reluctant to let it go. We are retired, so seldom need two cars - and could likely survive nicely with one and the occasional Uber call. The X5 diesel will tow the 23D over any pass at the speed limit with no strain, except I don't because the fuel consumption is so high - and we are in no hurry. It is overkill in the torque department.

I appreciate the suggestions to "rethink" my choices - that is always good. But I persist in determining if the hybrid will work as a tow car, and a ski car for 4 passengers, and an efficient local drive.

JCL, thanks for your experiences. We are willing to compromise on speed performance. We towed our 19' Bambi with a Volvo XC90 T6 with 268hp and 280ft-lb, which was just fine, except for one slow, worrying (will we make it?) haul over the Big Horn Mountains (we made it fine).
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Old 03-16-2017, 05:34 PM   #23
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Charlie,

I saw your note in my other thread. Interesting proposition. To your point about power limiting and the extent to which your battery will be depleted, I'm not an expert in hybrid load balancing, but here is what I can tell from published specs.

We know that the X5 has a range of 14 miles when on electric only. That equates to approximately 607Wh/mi assuming that there is 8.5kWh of battery usable (keeping the .5kWh aside to prevent bricking). That's higher consumption than my X uses while towing (575Wh/mi at 55mph), and about double what I use when driving without the trailer.

Of course, you won't be driving on electricity only. But the way that BMW appears to have implemented this system is to use the battery "when it is needed" to aid in performance. My guess is that as soon as you connect your trailer, it's going to be sensed as a need at all times.

What I take from this is that towing with the hybrid will chew through the battery readily on highways, and especially on any kind of climb. I don't think you can rely on it to help you in anything but stop and go traffic - the exact situation where it will be the least helpful from a torque/power perspective.

The question is more about whether towing without the battery assistance will be feasible, if limited. If so, you (and the rest of us) reap the benefits of the hybrid drivetrain all other times you're driving it.
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Old 03-16-2017, 08:50 PM   #24
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Thanks for your comments, ohmman. Your efforts are an inspiration and an example. Yes, I concluded the electric motor (which is built into the transmission) would consume about .5 KWh/mi, and I used your figures with the Tesla X and 22' Sport to guess the towing consumption would be 1.74 times higher, so .87 KWh/mi.

The work required to raise 1000lb up 1000ft of altitude is about .377 KWh. So my rig, at about 11,000lb would require 4,15 KWh to go up 1000' hill plus the level consumption of rolling friction and aero drag. For a 5% grade, traveling a distance of 3.78 mi, that would add 3.78X.87 = 3.29 KWh for a total of 7.4 KWh. Running only on electric motor, I would be limited to a pass that gained about 2400' or so. Of course, if the e-motor contributes only half of the energy, then I could tackle a 4800' elevation gain.

I also note that if the speed were 55mph, the 1000' 5% grade would take .0687 hrs, so 7.4KWh in that time would require a power of 108 KW, which is about 80hp. Do set me straight if any of this sounds wrong. Once I sort out some gear and axel ratios, I will compute some torque requirements as well as power requirements for different grades. Of course, I would love to hear from someone who has driving and towing experience with the car!

I do not yet own the X5 hybrid, but I think it uses software which looks ahead at the elevation profile of the Nav route, and manages battery charge accordingly. I believe it can charge on the level in addition to braking downhill. This certainly doesn't help fuel consumption, but could help fill the battery before the next mountain pass. There is also a manual "Save Battery" mode, which prioritizes charging and could be used to the same effect.

My enthusiasm for the hybrid is based on an expectation that we could tow with about the same mileage as our diesel, but short trips at any destination would be very low fuel usage. Around home, being retired with no commute, we would have little or no emissions.
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Old 03-16-2017, 09:06 PM   #25
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Oh, and the other advantage I expect from the hybrid: if it uses the electric motor for a lot of braking, maybe it would take longer for those front wheels to accumulate all that black brake pad powder. If you drive a any BMW or similar, you will know what i mean...
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Old 03-16-2017, 09:18 PM   #26
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rostam posted:

"Also, selling your X5 diesel is not going to help the environment as someone else will be driving your X5 diesel. A 5 year old X5 diesel is not heading to the junk yard. It has at least another 10 years left in it."

Well, actually, the buyer would send his V8 pickup to the junkyard and cut his/her towing fuel consumption in half - so that would help the environment!


(Please, no offense intended to roster -whose comments I appreciate - or anyone out there that loves their V8 pickup).

I do admit that yes, the X5 should be good for another 10 years - it is a bit indulgent to replace it with a new one...

Charlie
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Old 03-16-2017, 10:58 PM   #27
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My understanding is that it won't normally charge on a descent unless you are in Sport mode, as otherwise it will freewheel to save energy. That is from a detailed road test I reviewed.

Also, I don't think it charges the battery fully. The road test discussed how it charges (from the engine) up to a setpoint of 50%. If you want more charge than that, I presume you have to plug it in, and then you need to make sure the climb is right next to your last charge location. There are a lot of variables based on the drive mode selected.

I wouldn't count on any appreciable climb assist due to the electric drive. It just doesn't have enough battery storage. But around town not towing, yes.

Black wheel dust can be beaten. It isn't a BMW thing. It is a German TUV thing. Some BMW pads have been updated (on an X1 in the family, they were changed out due to a bulletin by BMW and there was no more dust). I have always just switched them out to a non-carbon pad (it is just the carbon black that causes the dust). I had the M wheels with narrow double spokes on the 535, and life was too short to clean them that often.

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Old 03-17-2017, 12:14 AM   #28
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Jeff,

I assume you found the non-carbon pads to perform well in braking? If so, I must look into that - I agree that life is too short to be constantly cleaning these filthy black wheels.

It would be disappointing to learn that only half the battery is available. I must learn more about that.

Charlie
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Old 03-17-2017, 12:18 AM   #29
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Correction to my earlier post:

"The work required to raise 1000lb up 1000ft of altitude is about .377 KWh. So my rig, at about 11,000lb would require 4,15 KWh to go up 1000' hill plus the level consumption of rolling friction and aero drag. For a 5% grade, traveling a distance of 3.78 mi, that would add 3.78X.87 = 3.29 KWh for a total of 7.4 KWh. Running only on electric motor, I would be limited to a pass that gained about 2400' or so. Of course, if the e-motor contributes only half of the energy, then I could tackle a 4800' elevation gain. "

I would be limited to about 1148 ft. But if battery supplies 1/4 of total power, I could tackle 4595 ft of elevation gain.
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Old 03-17-2017, 09:57 AM   #30
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I concluded the electric motor (which is built into the transmission) would consume about .5 KWh/mi, and I used your figures with the Tesla X and 22' Sport to guess the towing consumption would be 1.74 times higher, so .87 KWh/mi.
500Wh/mi would equate to a 7kWh battery (with the 14 mile electric range). Is your assumption that there is only 7kWh available in that battery? I assumed 8.5kWh, which is reserving just over 5% for bricking avoidance. That takes me to my number of 607Wh/mi. 1.74x for towing (assuming that ratio is applicable) would bring you to 1058Wh/mi. I would also argue that the efficiency curve is not going to be as favorable on the X5 electric motor compared to the Tesla electric motor. I base this on the fact that the X5 uses as much energy without a trailer as my X does witha trailer.

Quote:
Originally Posted by aircampr View Post
Correction to my earlier post:

"The work required to raise 1000lb up 1000ft of altitude is about .377 KWh. So my rig, at about 11,000lb would require 4,15 KWh to go up 1000' hill plus the level consumption of rolling friction and aero drag. For a 5% grade, traveling a distance of 3.78 mi, that would add 3.78X.87 = 3.29 KWh for a total of 7.4 KWh. Running only on electric motor, I would be limited to a pass that gained about 2400' or so. Of course, if the e-motor contributes only half of the energy, then I could tackle a 4800' elevation gain. "

I would be limited to about 1148 ft. But if battery supplies 1/4 of total power, I could tackle 4595 ft of elevation gain.
I think you need to tackle this again with revised numbers, but I also think the most important thing is figuring out how manageable the electric assist is. I believe you'd want to manually manage it, keeping it off until you absolutely need it. I worry that it will be a distraction while towing, but that may be unfounded.

I certainly don't want to discourage the purchase of a more efficient vehicle.
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Old 03-17-2017, 04:40 PM   #31
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This article has some information on the various charge/hybrid modes on the 40e.

http://insideevs.com/1200-mile-bmw-x...ance-delivery/

My earlier comment about half battery capacity wasn't in relation to plug in charging, when it can be fully charged, but to charging over the road using the gasoline engine. I had remembered reading about a 50% charge. Perhaps it is a function of which combination of modes is selected by the driver.

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Old 03-17-2017, 05:08 PM   #32
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ohmman, thanks for your input. I agree my numbers are likely conservative, and also I expect the Tesla would perform better. So your numbers are very helpful. I later corrected the 2400 ft estimate, in post above.

I have tried a different approach: forget the electric performance for now, and assess the towing performance using gas engine only. I want confidence that we can tow the 23D uphill in a headwind without stalling. And i want some feel for what speed, gear and rpm could be maintained on different grades.

I used the above numbers for 55mph to compute a thrust force (tires against the ground) of 436 lb. As rough estimates, I assumed this thrust force was 0 lb at 0 mph, and 850 lb at 80 mph. (I will not be driving at 80mph ground speed, but that would be the thrust requirement at 55 mph with a 25 mph headwind - and I can draw through three points with a French curve). For uphill grades, and an 11000 lb rig, the gravity component is for example 1100 lb on a 10% grade. So this lets me draw curves of thrust required vs mph for different grades. These curves may be shifted to the right for tailwind and to the left for headwind.

The spec for gas engine in the 40e shows 260 lb-ft from 1250 to 4000 rpm (which if true is quite impressive). For thrust available, I used final gear ratios and 28" rolling tire diameter to estimate thrust force at the max torque. I could then plot the available thrust in each gear as a flat line (simplified, I know) between the mph ground speed for each gear at 1250 and 4000 rpm.

Some example predictions (for no electric motor boost) from this: The car should do 55mph up a 5% grade in 5th gear at 2700 rpm, or possibly in 4th gear at 3465 rpm. It might do 55mph up a 10% grade in 3rd gear at 4290 rpm, but I would likely slow down for comfort and fuel consumption. It could manage 35 mph up a 15% grade in a 45 mph headwind.

So, if these numbers for gas only performance are in the ball park, I am willing to try towing with the hybrid. As for electric performance, the energy of a 1000' descent with 11,000 lb rig is 4.15 KWh. So the batteries could be fully charged at 80% efficiency, I would have 8.5 KWh after a 2048' descent. As mentioned an an earlier post, one reviewer said the cars software may stop charging at 50%. I don't know why they would do that, but I have a question in to BMW.

Charlie
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Old 03-17-2017, 05:16 PM   #33
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Thanks Jeff. Yes, I have seen that article. I am going to find a resource at BMW, or maybe get my hands on a manual.

I am tentatively convinced that the hybrid will work towing the 23D, and that we won't get stuck halfway up some steep mountain pass even if the batteries are depleted. That little 2.0 liter I4 twin-turbo appears to punch above its weight. It is no match for the 3.0 liter turbo diesel, but if makes it over the hill going slow, we don't mind.

Charlie
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Old 03-17-2017, 05:35 PM   #34
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Perhaps I missed it but does the door sticker show you have the payload capacity to legally and safely carry the weight. One thing to tow, another thing to carry.
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Old 03-17-2017, 06:46 PM   #35
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I am tentatively convinced that the hybrid will work towing the 23D, and that we won't get stuck halfway up some steep mountain pass even if the batteries are depleted. That little 2.0 liter I4 twin-turbo appears to punch above its weight. It is no match for the 3.0 liter turbo diesel, but if makes it over the hill going slow, we don't mind.

Charlie
I have driven that engine in other BMW vehicles. I found it responsive. To put it in perspective for towing with that hp, compare the hp and tow vehicle curb weight to a Ram 1500 ecodiesel. Lots of towing reports here on those. Some payload caution may be warranted, but owners don't appear to get stuck on mountain passes due to a lack of power, with the same 240 hp, and a heavier Ram truck, pulling up to a 25 foot Airstream (and some, larger). Your torque would come in sooner than most current diesels; my 535 with a twin turbo pulled very strongly from the 1250 rpm torque peak.

I will check the technical manuals and see if there is more on the 40e.

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Old 03-17-2017, 06:47 PM   #36
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I don't own this vehicle yet, but the manual says:

curb wt: 5220
front/rear: 2391/2829
approved gross wt: 6570
approved front axel load: 2750
approved rear axel load: 3870
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Old 03-17-2017, 06:56 PM   #37
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Thanks, Jeff. I did just find a Owner's Manual online. I am feeling more comfortable about this car the more I learn. I am getting some guidance from CanAm RV, and I will be looking for a local shop to install the Curt class III hitch, then reinforce it, as well as a brake controller. I have some Volvo towing mirrors which I have modified to fit the 2012 X5 and they are very nice. I will have to modify them again to shorten the upper arms due to the wider hood of the 2017.
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Old 03-18-2017, 07:39 AM   #38
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We use the Hensley Arrow hitch. When I took the 2007 Mercedes ML320 CDI to CanAm to have the hitch re-inforced, they also shortened the stinger (which required a new lock pin hole in the stinger) to bring the rig closer to the car for better control and pre-bent it to make loading the weight distribution happen in 3" of travel of the screw jacks versus 4 or more.

While we started towing a 25FB International Serenity with the 15" Michelin tires, we quickly decided that was too much and went to a 2012 Ram 2500HD Cummins that now tows the 31' Classic.

I kept the Hensley Arrow for some reason when the 25FB was traded in on the Classic , which has the ProPride hitch (second generation Jim Hensley design). The Hensley is now on the 23D which got a tire upgrade from the stock 14" tires and wheels to the same model 15" Michelins we used on the 25FB and using design matching SenDel wheels like on the Classic. Thus both trailers (25FB and 23D) were/are at the same elevation off the ground and all the Hensley settings from the 25FB are correct for the 23D. In 2017, Airstream is now installing the usual 15" GYM tires on the 23D.
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Old 03-18-2017, 11:24 AM   #39
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I have been reading the users manual for the X5 Xdrive40e and it is a very interesting design which partners a modest but competent ICE with an electric motor and modest battery pack. The two are designed to work together, and can be used to achieve a wide range of driving performance or fuel economy according to how the car is driven. There are an array of instrument and control screen displays (configurable) which can aid (and train) the driver in this tradeoff.

For short trips at home or at a travel destination, a charged battery can provide very low fuel consumption (or fairly high driving performance with 308 hp). The battery is not large enough to drive great distance on epower, but can be charged to recover energy on the downhill, which can be used either to reduce fuel consumption or enhance performance.

I expect there is potential to significantly reduce fuel consumption by rethinking how we drive and how we travel. This hybrid is not a direct replacement for our diesel X5, and could be disappointing if I tried to travel and drive it the same way. But I see this as an opportunity to learn how to travel more fuel efficiently, driving more conservatively and in shorter hops.

Charlie
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Old 03-18-2017, 11:32 AM   #40
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Switz, it is a long way from Apache, AZ to London, ON. I guess I might be willing to do that, but CanAm has been very helpful and forthcoming. I am waiting to hear from Andy of a shop near Seattle which can install and modify the hitch. Clearly Andy Thompson has and continues to contribute greatly to the RV towing community, and the world is a better place because of him.

Charlie
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