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-   -   What's too big for gas. (https://www.irv2.com/forums/f59/whats-too-big-for-gas-489154.html)

jeddpearl 05-29-2020 10:46 AM

Our V10, 320hp, 6.8L gasser works great on our 38', 22,000# MH. We have the 6 speed transmission which helps quite a bit.

jeddpearl 05-29-2020 11:01 AM

Same exact MH and no problems here, as well.

Old Scout 05-29-2020 11:59 AM

To be fair, you probably need to do an "apples to apples" comparison of similar coaches in similar conditions--one a gasser and one a diesel....the problem with low expectations is that its harder to be disappointed.....[smile]

Azmiike 05-29-2020 01:20 PM

36 foot Workhorse pulling Wrangler. Never saw a gas station it didn't want to visit. However, with the trade of between fuel, DEF and maintenance costs, personally I am happy. This is one of those things that there will never be a total agreement on.

TimmyB 05-29-2020 04:16 PM

Quote:

Originally Posted by Old Scout (Post 5282819)
To be fair, you probably need to do an "apples to apples" comparison of similar coaches in similar conditions--one a gasser and one a diesel....the problem with low expectations is that its harder to be disappointed.....[smile]

We did that in our search. Fleetwood has a model in the Pace Arrow series which is pretty similar to our Bounder. It would gain us about 5,000 pounds of GVWR and an additional 5,000 pounds of towing capacity. Unfortunately, the price is approximately 35% higher! For us, that would be a huge deal-breaker. Again, would I love to have that engine in the back, instead of roaring under my feet? Sure. For an additional $40-50K, not a great value. Our rig does everything we want it to, and if it doesn't, we'll get creative!

Unplanned Tourist 05-29-2020 08:39 PM

We have a 2008 Winnebago Adventurer 38J that's just shy of 39 feet.

The 8.1 Chevy/6 speed Allison works just fine. (Full Banks intake, exhaust and PCM upgrade)

We pulled my 2010 Ranger with bicycles in the back to Nova Scotia and back without any problems.

Averaged just under 10 mpg (Imperial) for the >15,000 km trip.

I wouldn't want to be longer or heavier, but it goes along just fine for us.

The price is right too! :thumb:

I'm not looking forward to when we have to replace the 22.5 tires, but that's about the only expense that is even close to comparing with a DP. :whistling:

Happy Glamping.

hipower65 05-30-2020 09:58 AM

Interesting question that has no universal answer.

My personal break point would be about 34-36 feet and 22K gvw. What makes that decision for me is actually less engine and more chassis. As coach owners, we too often expect a coach to ride, handle and perform like a car or light truck. Sadly unrealistic expectations.

We currently have a 40 ft. Dutchstar 4050 with over 100k on it. It does everything we need and then some. It's not inexpensive to own and operate but also not beyond expectations either.

If I had the opportunity to design and build what I would call the ideal coach for us it would be this: 40 ft. gas pusher chassis, 22.5 rubber on aluminum wheels, two axles, 36,000 GVW on air ride with air brakes. At least two slides and a front entry door wide enough to get larger items through it than current designs afford. The problem with that thinking is the cost for it would be too close to a similar chassis powered by a diesel engine.

The Workhorse UFO chassis was as close to ideal as I have seen in my years of RVing. Unfortunately not enough manufacturers offered it and I wasn't in the market for a coach when they were available.

My opinions are certainly slanted by many years of owning and operating heavy trucks. Beginning in a time when diesel engines were just making a dent in the market at 190-205 hp and we were running many gas engines like 450 ci International inline six cylinders or 549 ci International, 534 ci Ford and 427 ci Chevy V8's loading steel out of Pittsburgh and Weirton, WVA at gvw's well into 70k + gross eirght. All backed by five speed transmissions and two speed rears or five speed and three speed auxiliary transmissions. Different times for sure, but far from bad times.

Jpcoleman 05-30-2020 07:08 PM

Suncruiser 38Q was too big.
 
Our first coach was a 2016 Suncruiser 38Q. Bought for price and “new”. It was way too big for the F53 chassis. We did go over Eisenhower pass on 70 towing a malibu on way to Las Vegas and it did make it, but barely. I averaged 5-5.8 mpg depending if I was towing. That was going 65mph. It sounded like it wanted to die, but I was told this was normal.

Our current coach is 2016 Entegra Anthem, bought used. No comparison.

turbobill 05-30-2020 07:45 PM

Quote:

Originally Posted by twinboat (Post 5282612)
Back in the day, turbochargers weren't always used on diesels. Lots of NA ( naturally aspirated ) diesel engines.

Most RV diesel generators are NA.

Its the cubic inch that makes torque. We had a bunch of NA 855 cubic inch Cummins that pulled 10 wheel garbage trucks everyday.

If you want long life, there is no replacement for displacement.




Back in the day, the naturally aspirated 4 cycle diesels were out powered by the same cubic inch gasoline engines too. The turbocharger saved the diesel from extinction in many uses. Cubic inch for cubic inch and manifold pressure being equal, a gasoline engine out torques AND way out horsepower's a diesel engine.



A naturally aspirated diesel today couldn't begin to compare in power output with modern gasoline engines (of equal displacement) first of all, and second of all without the excess air from artificial aspiration, would never pass emissions either.


Cubic inches isn't the only thing that makes torque. Torque is also a function of BMEP. BMEP varies mainly with aspiration pressure, irregardless of displacement.


Interesting you mention the 855 Cummins. My M923A1 military 5 ton has one (NH250) while the later versions or those trucks have the turbocharged 8.3 C series. Day and night difference between the two engines. The 8.3 feels much stronger and gets better mileage, despite it's smaller displacement and 240HP rating.



I also have a large dump truck with a gasoline engine rated at 257 HP. At the same weights, there is no difference in performance between the two trucks and the gasoline engine is 377 cubic inches smaller.



Long life has nothing to do with displacement. If that statement was true, then today's smaller turbocharged engines would have shorter lifespans than the old big diesels. In truth, they last longer.



In the days before artificial aspiration, diesels had to be large displacement to make enough power to compete with gasoline engines. AND the heavy duty gasoline engines back then seldom had compression ratio's over 7:1. With today's compression ratio's along with modern engine management systems, a naturally aspirated gasoline engine would put to shame a naturally aspirated diesel of the same displacement in horsepower and torque.



The diesel engines ONLY claim to fame is it's higher thermal efficiency, nothing else. And with the difference in fuel prices in many parts of the country, the fuel cost per mile is a wash between diesel and gas. And after you add in the maintenance/repair/emission equipment costs associated with modern diesels, for many, they are a money sucking money losing proposition all the way around!

Unicorn Driver 06-01-2020 08:00 PM

I have a 37 ft class A rear engine gas and its drives very well

Donskiman 06-01-2020 09:40 PM

Quote:

Originally Posted by kongmen (Post 5271964)
Can some of you tell me your opinions on what point is the RV too big for a gas engine? Thanks.

The answer seems to be 40 feet. Less than 40 feet can be handled with gas, more than 40 not so much. Since the biggest gassers don't tend to get much past 39 feet, there wouldn't be many options for a gasser over 40 feet. Gassers in the 37-39 foot range have been around for years. Many people like them. What are you looking for?


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