Why diesel trucks?

Ok, I may accept that a modern V6 <= 4L can produce as much power as "big block V8s" did 20yrs ago.

I have to ask at what RPM and MPG does it do that?

Coming from a underpowered multiport EFI 351C that would transverse a local pass in 2nd gear @ 45-50MPH, (@god only knows RPM!) after owning a PSD I would NOT BUY into a truck to haul my camper that was powered by anything less than a PSD.

I bought a diesel once. I liked it so much I bought 3 more.

jimh425 wrote:


Torque and hp don’t always go together. As most of us know, you can create lots of hp at the expense of torque, but in the same gasoliine engine both numbers generally go up if you raise one unless you change the cam which is almost never done anymore.

Technically they do. It is HP that generate the torque, but gasoline engine have very steep power/torque curve, when diesels have it flatter.
Let's say we compare diesel and gas engines both having 100 hp and both having the same gearing.
So when you cruise at 2000 rpm, the diesel will deliver (fictional) 100 ft-lb of torque, but gasoline engine only 40 as it needs 3500 rpm do get to 100 ft-lb curve.
Final result is that when you step on it slightly - the diesel will pull like a train, while gasoline engine need to drop gears to get to 3500 rpm for the same torque.
Diesels of last decade are IMHO under-geared. My Ford drops from overdrive at about 1200 rpm, when my (4 cylinder) diesel sedan will pull on 7th gear and 1050 rpm.
Don't try to run gasoline engine at those rpm on high gears.

jimh425 wrote:

As far as ecoboost goes, there are enough people burned by gasoline turbo engines in the past that many people would prefer the displacement in the v8s with less things to go wrong. The exception being elevation where the turbos have an advantage.

The funny thing most folks don't realize is that the Ecoboost can ether "ECO" or "Boost". (not both at the same time)

"ECO" = low fuel consumption
"Boost" = turbo engaged, not low fuel consumption

Empty going to the store? Possibly Eco. (possibly good MPG)
Full load or towing? Needing BOOST. (not good MPG)

I have a small Ford SUV that has a 2.0L "ecoboost" in it that rarely gets its EPA MPG. I guess that my "lead foot" has it mostly in boost most of the time. :(

Kayteg1 wrote:
Today's 4-cylinder engines have more HP than famous 454 Chevy engine from 1980's, but you still don't see them mounted in big motorhomes like 200HP 454 was.

True, but the only reason the 454 in the 80s was unnecessarily restricted with new smog equipment that manufacturers didn’t understand. On the other hand, new v8s nonturbo just over 300 ci engines have double the hp on those 80 era 454s. You don’t see them in motorhomes either.

Torque and hp don’t always go together. As most of us know, you can create lots of hp at the expense of torque, but in the same gasoliine engine both numbers generally go up if you raise one unless you change the cam which is almost never done anymore.

As far as ecoboost goes, there are enough people burned by gasoline turbo engines in the past that many people would prefer the displacement in the v8s with less things to go wrong. The exception being elevation where the turbos have an advantage.

"there is no replacement for displacement" apply to torque, where big engines always have it bigger.
Today's 4-cylinder engines have more HP than famous 454 Chevy engine from 1980's, but you still don't see them mounted in big motorhomes like 200HP 454 was.
When I had my 7.3 Powerstroke with manual transmission, I used it for pulling brick retaining walls.
On low gear I did it at idle - no need to tap the gas.

Exactly, and there’s a limit to how fast any rotating mass can turn before it comes apart. I’m certain that the Ecoboost V6 COULD be mated with the right transmission and dropped into a dually pickup with the available payload to haul a big TC, but the fuel mileage would suck big time. Probably worse than the average mileage my current truck gets that has the TC on it 99% of the time (~11 mpg). And that’s saying nothing about it’s reliability.

My 6.9L diesel truck had a manual transmission, and I was always able to get in the best gear available. More gears wouldn’t have helped much if the engine wasn’t able to sustain the RPM’s.

I wasn’t aware Ford was having trouble selling the Ecoboost powered F150’s. That’s news to me. I’m aware that the vast majority of them are nothing but grocery getters, but there are enough of them used for towing and hauling that I’m also aware of the common complaint: fuel consumption.

:):)

You can’t ever look at just torque and not RPM at same time.
That’s just like taking about amps, but not voltage.
“Wow, that thing makes 100 amps of power!” Is a meaningless statement.
100 amps at 12 volts is 1200 watts.
100 amps at 120 volts is 12,000 watts.
Because, watts are volts x amps.

Horsepower is similar to watts. It’s a calculated number, torque x RPM, divided by 5250.
You can lower the torque and raise the RPM at which it’s made and come out with the same amount of power.

Maybe the smaller turbo engines being discussed are low on torque but the power difference isn’t as much as just the torque number makes it seem, because they’re making it at a higher RPM.

NRALIFR wrote:

I respectfully disagree for several reasons, not the least of which is my personal experience hauling truck campers on various trucks. First of all, I think you’re underestimating what’s needed to comfortably haul a large TC that weighs 5-6k lbs and has the frontal area of a fifth-wheel in ALL driving conditions. Towing and hauling at low elevation and flatlands is one thing, but in the mountains, which I do regularly, requires more than just HP. It requires torque.

You’re correct that the V6’s available today can make an incredible amount of HP. I have one in a car, and I love it. It makes 305 HP, but.........only 268 Lb-ft of torque. That’s less torque than the first Diesel powered truck I owned years ago that had the lowly 6.9L. It only produced 170 HP, but the torque was 338 Lb-ft. I can tell you that there were definitely some times that truck was not fun to drive with the TC on it. On steep grades over about 5000 ft elevation, you just had to fall in line behind all the loaded semi’s chugging up the hill. My speed would be dictated by the slowest truck in front of me, because I didn’t have enough power to pass.

You’re also correct that hauling TC’s is probably not much of a blip on any truck manufacturers radar. But, there are plenty of commercial and vocational uses for F250-F450 pickups that are very similar to hauling a heavy TC. There’s nothing particularly unique about TC’s. I know for a fact that Ford uses a testing device that simulates the weight and physical profile of a large TC or cargo box on their Superduty trucks during development. They quit using actual truck campers for testing years ago because they were destroying them.

I would have a hard time believing that they haven’t already put a Ecoboost V6 in a Superduty truck for testing purposes to see how it would do. In my opinion, if there was a V6 gas motor that would work in the Superduties, there would be one available by now. In the trucks the Ecoboost is available in today, where the truck is generally lighter than the SD’s and the trailers being towed have a lower frontal area than a big TC, the owners complain about the poor fuel mileage they see when they use the truck for its intended purpose.

We can only buy what’s available when it’s time to buy a truck. As I said earlier though, I’m eagerly awaiting the new 7.3L gas V8 availability in Ford trucks, and I hope it’s an available option for all of the Superduty pickups. That sounds like it’s going to be a good (maybe even great) truck engine. There are definitely V8 gas motors capable of towing and hauling heavy loads. Because I know how much my camper and our gear weighs, I don’t know of any V6 gas motor I’d want in a truck capable of hauling it.

:):)

Engine torque doesn't matter....torque at the wheels counts and torque at the wheels can be achieved with gearing.

The problem with comparing torque is your old truck likely had a 3 speed transmission that would often find itself not able to use the HP because the torque available didn't have an appropriate gear...modern trucks have 6-10 gears, so they could match the gear to the HP/torque the engine could put out.

The last line of your comment is likely the reason you don't see a V6 in 3/4 & 1 ton trucks...you have an impression it's not going to work. Ford fought the same thing with the eco-boost in the 1/2 ton...people expected to need a V8 if they towed so it's a tough sell from a marketing point of view not a capability point of view.

valhalla360 wrote:
........

There are none because the truck camper market is such a tiny percentage of the 3/4 & 1 ton market, that the manufacturers aren't interested in producing one.

Modern NA V6 engines happily put out HP equal to what big block V8's put out 20-30yr ago. And with 6-10speed transmissions, they can utilize that HP...so that is all they really need. It's just that th base gas engine gives you more power...supporting the idea that diesel makes little sense if a truck camper is the limit of what you use the truck for.

I respectfully disagree for several reasons, not the least of which is my personal experience hauling truck campers on various trucks. First of all, I think you’re underestimating what’s needed to comfortably haul a large TC that weighs 5-6k lbs and has the frontal area of a fifth-wheel in ALL driving conditions. Towing and hauling at low elevation and flatlands is one thing, but in the mountains, which I do regularly, requires more than just HP. It requires torque.

You’re correct that the V6’s available today can make an incredible amount of HP. I have one in a car, and I love it. It makes 305 HP, but.........only 268 Lb-ft of torque. That’s less torque than the first Diesel powered truck I owned years ago that had the lowly 6.9L. It only produced 170 HP, but the torque was 338 Lb-ft. I can tell you that there were definitely some times that truck was not fun to drive with the TC on it. On steep grades over about 5000 ft elevation, you just had to fall in line behind all the loaded semi’s chugging up the hill. My speed would be dictated by the slowest truck in front of me, because I didn’t have enough power to pass.

You’re also correct that hauling TC’s is probably not much of a blip on any truck manufacturers radar. But, there are plenty of commercial and vocational uses for F250-F450 pickups that are very similar to hauling a heavy TC. There’s nothing particularly unique about TC’s. I know for a fact that Ford uses a testing device that simulates the weight and physical profile of a large TC or cargo box on their Superduty trucks during development. They quit using actual truck campers for testing years ago because they were destroying them.

I would have a hard time believing that they haven’t already put a Ecoboost V6 in a Superduty truck for testing purposes to see how it would do. In my opinion, if there was a V6 gas motor that would work in the Superduties, there would be one available by now. In the trucks the Ecoboost is available in today, where the truck is generally lighter than the SD’s and the trailers being towed have a lower frontal area than a big TC, the owners complain about the poor fuel mileage they see when they use the truck for its intended purpose.

We can only buy what’s available when it’s time to buy a truck. As I said earlier though, I’m eagerly awaiting the new 7.3L gas V8 availability in Ford trucks, and I hope it’s an available option for all of the Superduty pickups. That sounds like it’s going to be a good (maybe even great) truck engine. There are definitely V8 gas motors capable of towing and hauling heavy loads. Because I know how much my camper and our gear weighs, I don’t know of any V6 gas motor I’d want in a truck capable of hauling it.

:):)