Question Towing Question

[OML]

Hi,

We have a 2019 Silverado RST, 2.7L Turbo.

Trailering info:
GVWR 6800 lbs
GCWR 12000 lbs
Max Payload: 1983 lbs
Curb Weight: 4817 lbs

We're towing a travel trailer which weighs 3700lbs.

The truck tows the trailer ok, however it stresses a lot while towing, especially going up hill. And the MPG is terrible (between 8-10. Took a whole tank to drive 160 miles).
I was wondering what are the considerations when pairing a truck to a trailer. Which specs should we look for in a truck so that the towing could be more efficient.

Thanks!

 

[Rich W.]

There are two immediate issues here:

1. Your 3700lb trailer probably weighs 5000lbs or more loaded
2. That 4 cylinder 2.7 is probably great for mpg in an empty truck, but does not have the power to pull much of a load, regardless of the rest of the specs.

So while you can legally, and probably safely tow that trailer, the truck will have to work at its maximum effort to do it, and yes mpg will suffer.

 

[Bigblockyeti]

That 4 cylinder 2.7 is probably great for mpg in an empty truck, but does not have the power to pull much of a load, regardless of the rest of the specs.

This.

There's no replacement for displacement. GM knows many are cross shopping a Civic with a Silverado and will use either for the same duties, so they made the tiny turbo Silverado. They also offer a 6.2L gas engine for those looking to use a truck as a truck.

 

[Rich W.]

I’m not a Chevy guy, but my fire dept command vehicle was a Suburban with a 6.2 and was very satisfying to drive with no shortage of power. It would be a great choice for a two vehicle.

 

[Joe Hogan]

Here is a video discussing and testing your situation. Looks like flat land MPG is decent at 14-16 or so. Roadway Grades are probably hard on fuel economy as engine has to work much harder to maintain speed. WHere as a big V8 has lots of spare torque the little 4 is having to rely on boost/fueling to make it.

 

[Joe Hogan]

Now for the technically minded, an engine is effectively an air pump.
The formula for effective displacement is as follows((14.7 + boost psi)/14.7) * displacement= will give you approximate displacement equivalent, all other things like atmospherics, friction, etc. being equal.

For example a 2.7l at 10 psi Boost is 14.7+10=28.7/14.7=1.68*2.7=4.5L approximate effective displacement.

The added displacement comes from extra air and fuel.

 

[OML]

Thank you all for your responses! Very helpful.

 

[Rich W.]

Now for the technically minded, an engine is effectively an air pump.
The formula for effective displacement is as follows((14.7 + boost psi)/14.7) * displacement= will give you approximate displacement equivalent, all other things like atmospherics, friction, etc. being equal.

For example a 2.7l at 10 psi Boost is 14.7+10=28.7/14.7=1.68*2.7=4.5L approximate effective displacement.

The added displacement comes from extra air and fuel.

That engine makes 310hp but it does so at 5600 rpm. So while that would be acceptable hp for a pickup thanks to boost from an otherwise small displacement engine, it is not realistic to assume you have all that hp on tap all the time because you cant run continually at that rpm and even if you could mpg would be horrendous because you are operating at max fuel use. Also these engines develop relatively little torque which is more important for towing, which the OP has found out.

 

[Rich W.]

All that said, I wouldn’t immediately go to the expense of changing trucks over this. I might just accept the fact that I’ll be going 40mph in a lower gear on the grades, cruise in the low 60’s on the flats, and make the relatively small investment in an auxiliary gas tank to gain some range.

That trailer isn’t overweight for the truck, its just a full load. As long as you aren’t in a hurry (and you shouldn’t be when towing anyway) you might find a happy medium, especially if you are just towing a few times each year. Full timing in the mountains would be a different story. But for a few camping trips during the season, I’d first try to make it work because its a nice relatively new truck and probably perfectly fine for the other 95% of your driving.

When I was driving gas motorhomes, I would gear down and slow down climbing the grades, finding the gear that would allow me to climb the hill comfortably at around 4000rpm, rather than push it at over 5,000 as many people do (and then complain that the engine is “screaming”). If that meant 40mph (or less), so be it - it was better than abusing the engine and I wasn’t in a hurry anyway.

 

[Joe Hogan]

Rich,

To your point, this is one reason the video example was able to get decent fuel economy. Cruising on a flat highway at say 65 mph does not use much horsepower. Accelerating a load does take power and lots of it. Also, as we see trucks struggling up grades, moving up a grade takes power, lots of it. It is the acceleration and road grades that will take all the horse power.

Here are some simple numbers to determine power needed for certain activities. Quote from a Post I came accross:

"A modern Diesel engine uses about 0.31 pounds of fuel per horsepower-hour. Let’s say our big truck averages 10 mpg at 65 mph. This works out to 6.5 gallons per hour. At 7pounds/gallon, this is 45.5 pounds/hour. Dividing by 0.31 gives ~146 hp. (~110 KW).

Smaller trucks use gasoline engines. A gasoline engine uses about 0.5 pounds per HP-hour. Let’s say our smaller truck gets 14 mpg. This is 4.6 gallons/hour. Gasoline is less dense than diesel fuel, at about 6 pounds/gallon. This is 27.8 pounds, ~57 HP. (~43 KW).

Both types of vehicles would typically have engines rated at higher HP. Diesel engines work best when operated continuously at about 65–80% capacity. Full power is needed only for acceleration and hill-climbing. Heavy duty gasoline engines (as found in pleasure boats) are typically operated at about 50–60% of full capacity. Light duty engines - as found in passenger cars - are normally operated continuously at only 10–20% capacity."