Engine liter size vs horsepower vs torque?

[flygal6]

Can any of you mechanical minded types out there explain the difference looking at a 3.0L, 3.5L and 4.0L engine size? For instance in researching various 6 cyl TV a 4.0L engine has less horsepower than maybe a 3.5 or 3.7L engine? How does the liter size, horsepower and torque relate to each other with regards to towing power? Is it better to have higher HP or torque for towing power? Am I right in the apparent relationship that as horsepower goes up, MPG goes down?

Can anyone shed some light on this whole issue and make it easier to understand?

I know my puny 220hp 3.0 V6 is one of the smaller ones and does ok out here in the relatively flat midwest, but wouldn't want to challenge it out west doing any kind of mountainous terrain. So as my overall trailer or tow weight increases, should I be looking for an engine that generates more torque or more horsepower?

Any help with this would be greatly appreciated

Carol

[flygal6]

Just one more thing. I am towing a 16 ft trailer now. I kinda grew out my teardrop. So the weight now is more of an issue than I had with my little TD.
Carol

[wagondude]

Torque does the work. That is the more important number. When looking at a 6 cylinder engine, an inline six will have more torque than the same displacement engine in a V configuration. My dad had an '84 ford f-150 with the six. It was rated at the same torque but only 10 less horsepower compared to the same truck with the 5.0 liter v-8. The v-6 that they put in the Mustang at the time wouldn't touch the inline for torque.

[caseydog]

Wow, you have opened quite the can of worms.

When it comes to towing a trailer with efficiency, torque matters. But, there is more that one way to get that torque. A small turbo diesel can tow a trailer with almost no loss in fuel economy, while a big six cylinder gasoline engine could deliver tons of low-end torque, and drink gas like a V8. I have a twin turbo V6 in my tow vehicle, and even though it is only 2.7 litres, it is rated to tow 3,500 pounds. But, towing a trailer, it uses a lot of 91 octane gasoline.

Towing a 16 foot trailer, you can't beat a diesel. Fuel economy with and without the trailer will not be much different.

My own personal experience with a 4.3 litre V6 in a GMC Jimmy towing a boat, was not what I would call impressive. I would have gotten the same fuel economy with a V8 pickup.

Of course, if you tow your camper ten days a year, and have to commute with the same vehicle the other 355 days a year, buying a V8 truck is a real waste of gasoline, and money.

Until more small turbo diesels are available here, without having to spend 50K on a Mercedes turbo diesel that can spank an American V8 and still go 600 miles on a tank of fuel, you will probably have to save up your pennies to go camping.

CD

[asianflava]

Just keep in mind that towing ability does not depend entirely on HP and Torque, don't get hung up on numbers. For example a Neon SRT-4 comes with 220hp from the factory, but it wouldn't be an ideal TV for a car hauler. Manufacturers also factor in wheelbase, frame strength, brakes, etc.

[Yota Bill]

Also, the rated torque or HP doesnt matter much if it is not usable. Transmission and axle gearing comes into play as well.
If you are looking for a more suitable tow vehicle, pay more attention to its rated towing capacity then either of the advertised torque or HP numbers. Then there are other things to consider, that help with towing. Transmission and power steering coolers, whether or not its pre-wired for a trailer (or can be added to the existing factory wiring easily) if there is a hitch avalable for the vehicle and what type, etc.

You could try to compare all of the available info (HP, torque, trans gear ratios, axle ratios, shock and spring rates, etc.) or you could just let the manufacturer do that for you and just go by what it is rated to tow. Also, that is the number the DOT will go by if they think you are over weight (and the tow rating does not change, regardless of modifications, in the eyes of the DOT)

[Larwyn]

Well, I thought I had a thing or two to say but I think Slowcowboy covered it........

Just one thing......................power comes from cubic inches not form liters.........

[jss06]

For those that are not aware. HP is derived from Torque and eninge speed. For towing low end torque trumps high end HP.

By that I mean. Higher torque at lower RPMs is better then High HP at High RPMs. What good does 300HP get you if you have to run the engine at 5000 RPM to make it.

Long stroke gas engines make a ton of torque. Unfortunatley they are a pain to clean up for emissions. So most auto manufactures are making short stroke high RPM engines to give you those all important high HP numbers and still meet government regualtions.

Remember, the slower you can run the engine to get the job done the better your fuel economy will be. (this is overly simplistic but I don't want write a 3 page article on engine performance.)

[wagondude]

The best thing to do is look for a TV with the towing capacity for your intended load (remember to leave some headroom). Then get the highest torque at the lowest RPM. But, you will also have to check the drive axle ratio as well. An engine with the torque 500 RPM higher in the band may pull better than the one with the lower RPM just because it is geared better.

[Woodbutcher]

Well Flygal, does all that answer your question? You may be better off telling these guys what tow vehicles you were looking at and let them make a suggestion. I have not met a car salesman yet that could tell me anything about torque at a certain RPM. But they could all tell me how many cup holders the car had!

[caseydog]

I understand a team of Clydesdales can tow just about anything. I can't say I want to own a team of Clydesdales. I live in 2011, where a 3.0 litre V6 turbo diesel can perform like a 5.0 litre gasoline V8, and travel 600 miles on a tank of fuel.

There must be some reason that 18-wheelers and trains run on diesel.

My only problem with diesel tow vehicles is getting one in the US that I like and can afford. There aren't many to choose from.

On another front, Ford is offering it's 3.5 litre Ecoboost twin turbo V6 in the F150 pickup. It puts up 365 HP and 420 lb/ft of torque. The torque peaks at 2,500 RPM, but 90 percent of the peak is available from 1,700 to 5,000 RPM. Like I said before, there is more than one way to get torque. It's not all about cubic inches in the 21st century.

BTW, the reason for twin turbos is that two small turbos will deliver boost faster -- less turbo lag -- than one larger single turbo.

For people stuck in the sixties, Ford still offers big V8s in the F150. But, with a towing capacity of 11,600 pounds, the Ecoboost V6 should tow most trailers, just fine.

CD

[Scooter]

Is diesel fuel universally available? I remember driving around Austin in 1997 and running out because we couldn't find a place that sold it. Stalled on the freeway in a Ryder truck in the middle of an unfamiliar town...never again.

Perhaps we didn't know what to look for??

[john warren]

ok,,, horsepower and torq are nice,,, but a 40 hp tractor can pull stupid amounts of weight. gearing counts a lot. BUT.......

the weight of your vehicle, its brakes, its transmission cooling can all be important.

for example, my v6 ford ranger is rated around 4000 pounds, and it will pull it just fine. till you add the wind resistance of a tall camper trailer. then your miles per gallon go in the toilet, it won't stop shifting in and out of overdrive and the trans starts getting hot, and i don't want to think about slamming my brakes on to avoid a deer.

so you need a safety margine. enough to pull the # of pounds you want to pull. gearing and brakes to do the job. trans cooling and even an extra oilcooler helps. trailer brakes. and enough extra to pull long hills and buck a stiff wind.

this is a case where the "MORE POWER" ARGGGG " thing really helps.

[Bikerman]

[quote="Scooter"]Is diesel fuel universally available? I remember driving around Austin in 1997 and running out because we couldn't find a place that sold it. Stalled on the freeway in a Ryder truck in the middle of an unfamiliar town...never again.

Perhaps we didn't know what to look for?? [/quote]

Yes, it's available anywhere semi's run. In neighborhood stores they may not have diesel but I can't think of a station along a highway that does not. It's even more prevalent in other countries.

[Gary and Cheri]

When I drove out to IRG from Wisconsin this past summer I had no problem finding diesel. It was a worry I had before the trip.. I remember that 20 years ago Mercedes actually put out a book detailing citys and stations that sold diesel but that is not needed today. In Wisconsin I will be able to find diesel in just about every town, can't speak for the other states.

As to is a diesel any good, well just a couple of weeks ago we had a little endurance race in Sebring Florida and the first three finishers after 12 hours all had diesels under the hood. The last few years the winner of the 24 hours of Le Mans have all had turbo diesels. If you want to win in long distance racing a diesel is what you need.

Gary