Rightsizing for downsizing

[Chance]

RV sales in 2016 suggest buyers are shifting somewhat towards smaller motorhomes. In 2016 Class B and Class C sales were up 13.1% and 12.7% respectively, while Class A sales were up 5.4%.

We've all probably already noticed that smaller/lighter Class B and C motorhomes are being powered by 4, 5, and 6 cylinder engines. Sprinter and ProMaster come with 4 or 6 cylinder engines, while Transit are 5 or 6 cylinder. Many of these are approximately half as large in displacement as the typical Ford V10 we drive.

This short article on rightsizing engines and powertrains in order to meet regulations, from the perspective of auto industry, may be of interest. Complicating matters is that it's not just about what will technically work, but what customers will buy.


The upside of downsizing: senior auto executives give their views - SAE International


Thoughts on how rightsizing may affect larger motorhomes?

[Chance]

On a related topic, Mercedes has developed a new modular engine family that includes both gasoline and diesel. I really like that they are going back from V-6 to I-6 (inline 6-cylinder). Some of the new engines will include electrification using 48-Volt power to augment performance and fuel economy. Use of electric air-conditioning compressors is of particular interest to me because it may eliminate the need for a secondary A/C for camping. Maybe a little wishful thinking there on my part.

Mercedes is reportedly doing a redesign of Sprinter for 2018, but I haven't found information on whether the Sprinter will get the new inline-six or not.


Mercedes extensively electrifies its new ICEs - SAE International

[JamieGeek]

Keep in mind that they want to use 48V so that they can do a mild-hybrid: Use the 48V to power a traction motor to get a low-cost mpg improvement. Granted that once the design moves to 48V all the other things will follow.

In addition, I would bet that the early cars with 48V systems will also have a 12V system to be backwards compatible with a bunch of existing parts (note that just about every electric vehicle also has a 12V system to go along with the high-voltage traction system).

A lot of traditional vehicles have been moving to an electrical A/C system simply to save a few mpg: (When the gas engine is running 2500 rpm going down the highway but the inside of the car is already at temp there is no reason to run the A/C compressor that fast--an independent electrically run A/C solves that issue.) I believe that a bunch of Ford's use an electric A/C (Focus, Escape, C-Max, Fusion, and their Lincoln equivalents). I wonder if the OEM's would build a slightly larger A/C for the stripped chassis units knowing that there will be a "big box" mounted on them (and also allow for control independent of the ignition switch).

The auto companies are also getting really good at eeking out those last few HP out of existing gas engines. Hence all the cars with smaller displacement engines with the same, or better performance.

[wredman]

one issue, or difference, I see with "smaller" RVs is that they are not much smaller from the perspective of the air resistance. They are lighter, and less engine is required for hills, but the bulk of the energy expended on a trip is against the air.


Where do you find yearly RV sales, your #s don't match the RVIA data.

[Chance]

Originally Posted by wredman

one issue, or difference, I see with "smaller" RVs is that they are not much smaller from the perspective of the air resistance. They are lighter, and less engine is required for hills, but the bulk of the energy expended on a trip is against the air.


Where do you find yearly RV sales, your #s don't match the RVIA data.

Valid point on wind drag, although I assume it works against larger motorhomes. When engine is sized for adequate acceleration and hill climbing, then it becomes too large to be optimized for fuel economy during level-road cruising. Additional overdrive gears help with that, but engines can only operate so slow before they become inefficient or create vibration problems, etc...

SSI: C’s Shine as ’16 Motorized Sales up 12.7% | RV Business

SSI: Class B Sales Roll to 13.1% Gain for 2016 | RV Business

Also show December sales versus previous year show Class B and C were up 7.1% and 3.6% respectively, while Class A sales were down 3%.

I'm curious what numbers you have in case these are off?

[Chance]

Originally Posted by JamieGeek

.....cut.....

In addition, I would bet that the early cars with 48V systems will also have a 12V system to be backwards compatible with a bunch of existing parts (note that just about every electric vehicle also has a 12V system to go along with the high-voltage traction system).

A lot of traditional vehicles have been moving to an electrical A/C system simply to save a few mpg: (When the gas engine is running 2500 rpm going down the highway but the inside of the car is already at temp there is no reason to run the A/C compressor that fast--an independent electrically run A/C solves that issue.) I believe that a bunch of Ford's use an electric A/C (Focus, Escape, C-Max, Fusion, and their Lincoln equivalents). I wonder if the OEM's would build a slightly larger A/C for the stripped chassis units knowing that there will be a "big box" mounted on them (and also allow for control independent of the ignition switch).

......cut.....

That's a safe bet. Information I've seen shows manufacturers will use a DC to DC converter to step down from 48 to 12 Volts for the few items that need lower voltage.

However manufacturers implement 48-Volt A/C, I'm just looking forward to the day when a Class B can just run the factory A/C using the factory-provided condenser, evaporator, fans, etc... We will just need to keep 48-Volt battery charged. Should be quieter, with no condensation drain issues, etc...

There are 48-Volt A/Cs now, but cost is prohibitive. Once compressors are mass produced, it should be easy to adapt them for additional RV cooling capacity if needed.

As I stated before, I'm fairly certain 12-Volt RV electrical will convert to 48-Volts; it's just a matter of a little time.

[wredman]

I found yearly/monthly data on this website. The December data will have the yearly total.

The Recreation Vehicle Industry Association: Current Month Summary

[Chance]

Originally Posted by wredman

I found yearly/monthly data on this website. The December data will have the yearly total.

The Recreation Vehicle Industry Association: Current Month Summary

Difference may be that one is listed as shipments, versus the other as sales.

Your numbers show much greater growth rate for Bs and Cs, and a greater decline for As. If I'm interpreting shipments versus sales correctly, it may mean that dealers are adjusting their inventory in anticipation of what's moving fastest.

I'm assuming shipments means from manufacturer to dealers, and sales from dealer to final owner. But I may have that backwards -- not sure.

[wredman]

still a relatively small player, but the class B is certainly growing in the past few years.

[CasaLoca]

I would keep in mind that the RV market includes many sectors. For instance, class B sales may grow as a portion of the total market but that is likely just growth on the size of the total market. Not offering any actual evidence but I would guess that there are few full timers or long termers in class B rigs. A few exceptions exist no doubt but those who spend major time in their rigs that I have met are all in class As or large trailers.
Chuck Peck in CasaLoca

[Chance]

I keep thinking that a 6.8-liter V10 can't be equally as efficient on a 20,000-pound Challenger as in a 12,000-pound Axis (aside from 2-valve versus 3-valve difference). One has to be too large or the other too small.

I'd guess there is a real technical opportunity to rightsize an engine for an Axis-size motorhome much below 6.8 liters of displacement. I also think buyers wouldn't want it unless it increased MPGs by an unreasonable amount. I can see where manufacturers are facing a tough marketing challenge versus regulation requirements.

[Chance]

Originally Posted by wredman

still a relatively small player, but the class B is certainly growing in the past few years.

This time period of fast growth happens to coincide with introduction of RAM ProMaster van platform in US that is more affordable than the Mercedes Sprinter, which was the only large Euro van in US before that as far as I know. A lower-cost option may have helped fuel the fast growth rate. Winnebago and Hymer, Class B leaders, now manufacture on that van platform in addition to Sprinter.

A video of the Sprinter redesign for 2018 shows what looks to me like a FWD van being tested (or could be electric). Maybe Mercedes is going to compete with Ford and Fiat with a FWD van. In many ways FWD vans make better camper conversions. And it's another way to improve fuel economy and handling.

Note in picture below that a standard RWD axle is missing. I'd bet it's either FWD or Electric drive.