Ram 1500 diesel review

bimbert84 wrote:
Sure, and I've not disputed that. But then again, choosing the right gear for the job doesn't bother me.

Believe me, I get it. And I know you do, too. But there are many, many people who don't. They just want to look at peak numbers and run with them. And for some reason, they're afraid of downshifting, and they learn that a diesel will keep them from having to do so. Then they notice on the spec sheet that the diesel has more peak engine torque, and they erroneously conclude that peak engine torque is what pulls a trailer up a hill. The article referenced by the OP does exactly that, and it's wrong. That's why I called it out.

It is peak torque that pulls the trailer up the hill and the lower RPM the engine makes that torque, the more power it makes at that RPM. Sure, if you increase RPM, you can put more torque to the ground with less engine torque by using the appropriate gear but that doesn't make it a better towing engine. If it did, a 3 liter F1 engine should be a towing beast if you just put the right transmission behind it, because it can make over 700 HP. Trouble is, it's at 19,000 RPM.


The statement isn't wrong, it is torque that gets the job done, HP is the rate at which the engine is applying torque.

I quoted your exact words above. But it's occurred to me there are two ways to interpret them:1.No one would argue against X, meaning "dispute"
2.No one would argue for X, meaning "claim"
where X = "the diesel is the more powerful of the two."

I interpreted it as the former (and I would argue against X). Did you mean the latter?

I said, no one would argue the diesel is more powerful. If I was arguing that the diesel was more powerful, that statement wouldn't be true, because someone would be arguing it was more powerful. Me.

jus2shy wrote:

All I was doing was showing that the two different engine types have a different delivery of horsepower

Yes, of course. And FWIW, I think your last post was most excellent, and I agree with most all of it.

jus2shy wrote:

In the case of Ford Superduties, the Diesel and Gas engines use the same exact transmission....

Although true, this does not mean those transmissions need to be operating in the same gear at any given road speed in side-by-side trucks.

jus2shy wrote:

So you get different behaviors out of these two trucks.

Yes! Unfortunately, your spreadsheet doesn't capture that.

jus2shy wrote:

As to the spreadsheet, it's easy to add another modifier line to it and chart out available power for given tire size, axle and transmission gear ratios. In the end, the transmission and differential are going to be multiplying the output from those base horsepower charts on the spreadsheet.

Yes, but the multipliers being applied at any given time won't be the same, and that's what's missing. Dynamically on the road, it would go something like this:

10 mph - Both trucks in 1st gear, diesel clearly producing more power.
20 mph - Diesel upshifts to 2nd, loses power, loses torque advantage of 1st gear. Gasser increasing power, maintains torque advantage of 1st gear.
30 mph - Gasser upshifts to 2nd.
40 mph - Diesel upshifts to 3rd.
60 mph - Diesel upshifts to 4th.
70 mph - Gasser upshifts to 3rd.

Now I don't know the exact speeds where those shifts would occur, but in this example, at 60mph the gasser will be in 2nd gear while the diesel is in 4th. They will not be spinning the same RPMs, so comparing them at the same RPM is meaningless.

If we could amend the spreadsheet to have columns for road speed, then populate that column with the maximum power available at each road speed, we'd get a much more useful comparison. Then we could draw a graph and very easily see which vehicle, not engine, provides more power across the entire speed range. But to get this we'd have to know all the other variables you mentioned, and we'd have to calculate which gear provides the most power for each vehicle at each road speed (they won't be the same). Any comparison that fails to account for that gear difference is of very limited real-world value. Unfortunately, those are the only comparisons we ever see.

-- Rob

wilber1 wrote:
No one would argue that the diesel is the more powerful of the two....

wilber1 wrote:
I didn't say the diesel was the most powerful of the two.

I quoted your exact words above. But it's occurred to me there are two ways to interpret them:

1. No one would argue against X, meaning "dispute"
2. No one would argue for X, meaning "claim"

where X = "the diesel is the more powerful of the two."

I interpreted it as the former (and I would argue against X). Did you mean the latter?

wilber1 wrote:
Because you can't run the gas engine at low RPM's and make the same power as the diesel.

Of course you can't. And you can't run the diesel engine at high RPMs and make the same power as the gasser. So what? That's why we have transmissions.

wilber1 wrote:
Below 3500 RPM the diesel will make more power in any gear.

Not if the diesel is in 4th and the gasser is in 2nd. Why do they have to be in the same gear?

wilber1 wrote:
The diesel makes more power at lower RPM allowing it to pull in higher gears at lower engine speeds more efficiently. True, you don't have the same maximum performance capability but it makes for a more relaxed drive and less shifting. Throw in 30% better fuel efficiency and it becomes pretty appealing to a lot of people.

Sure, and I've not disputed that. But then again, choosing the right gear for the job doesn't bother me.

Believe me, I get it. And I know you do, too. But there are many, many people who don't. They just want to look at peak numbers and run with them. And for some reason, they're afraid of downshifting, and they learn that a diesel will keep them from having to do so. Then they notice on the spec sheet that the diesel has more peak engine torque, and they erroneously conclude that peak engine torque is what pulls a trailer up a hill. The article referenced by the OP does exactly that, and it's wrong. That's why I called it out.

-- Rob

bimbert84 wrote:


It's not a deficiency. It's a difference in the way the engines operate.

I simply don't understand the compulsion to compare these engines at the same RPM. It's like comparing a running back to a wide receiver but never throwing a pass. That's not a deficiency of the wide receiver -- it's a misuse of his abilities. The same is true with running a gas engine at low RPMs when power is needed. Why would you do that?

The entire purpose of the transmission is to put the engine's power to the ground, yet so many people choose to ignore this. A better spreadsheet would be one that shows maximum available power at any given road speed. Do this and you'll find the diesel and gas engines will be running different RPMs (because they'll be using different gears) at the same road speed.

-- Rob

Maybe deficiency wasn't the best word choice. All I was doing was showing that the two different engine types have a different delivery of horsepower (I just noted the 1:1 ratio to make comparisons even on power delivery). Such as when 200 HP is needed to move a load, the diesels will have it at 1500 RPM, and the gassers will be either at 2500 RPM or 3100 RPM depending on which engine in the spreadsheet. I think Wilbert was trying to express why many diesel fans find a diesel more satisfying to drive with that lower end power. Not saying that one or the other is superior power wise when it comes to pulling a load.

In the case of Ford Superduties, the Diesel and Gas engines use the same exact transmission and the only differences are rear gears (gas motors typically have 3.73 or 4.10 rear ratios while diesels get 3.31 or 3.55). So you get different behaviors out of these two trucks. The gas motors have far more operation range (6,000 rpm redline or there abouts) than the diesels (roughly 3100 rpm) and can dig down all the way to 2nd gear at freeway speeds if they need more power to pull a load up. This allows a Gas Motor to multiply their output to the ground more when they get into their power band. Sure they'll be revving pretty hard, but they're designed for that. This is typically the reason why a gasser will out-accelerate and pass a diesel with similar horsepower figures on a flat road (once the gasser gets to its powerband). Diesels with their narrow power band don't have this flexibility, so they "feel" like they lose a bit of steam when they can't downshift to 2nd gear on the freeway and accelerate hard, instead they have to remain in a higher gear and lose the advantage of output multiplication from the transmission.

Unfortunately all gassers in heavy duty trucks (F-250/2500's) are naturally aspirated and lose a lot of power high in the mountains. Now if they were turbocharged like the Ecoboost motor from Ford, I'm pretty sure the truck would have no problem going up a mountain since the turbo's will ensure the engine gets close to the same amount of oxygen as it did at sea floor. If a diesel didn't have a turbo, you would experience the same power loss in the mountains as well, then you would be the one holding up traffic in the slow lane.

As to the spreadsheet, it's easy to add another modifier line to it and chart out available power for given tire size, axle and transmission gear ratios. In the end, the transmission and differential are going to be multiplying the output from those base horsepower charts on the spreadsheet.

Just from reading this thread there is going to be a lot of people that will lose their mind when the 8 and 10 speed trannies hit the market.

Look at all the people that are complaining about too much shifting with 4, 5 and 6 speeds. :R

jus2shy wrote:
To help illustrate wilber's point, I made a comparison on another forum showing the difference in HP generation between Diesel and Gas motors. As you can see, both 6.7's produce far more horsepower at far lower RPM's while the gas motors take a while before they hit their horsepower band. So say you need 200 HP to pull a trailer, the Diesels have that power available at 1500rpm up to their respective redlines. The ecoboost makes that power at 2500rpm while the 6.2L ford takes all the way until 3100 rpm before it's making that power. This is all assuming a 1:1 engine to drive ratio. Gearing makes up for these deficiencies though but it just shows shy Diesels have so much more oooomph!

Trying to stick a google sheet in here:


If that doesn't work, here's a link to a PDF of it:HP Spreadsheet

Another advantage of the diesel is average power under the curve. With a 6 speed and fairly loose converter, the diesel drops only 500 rpm per shift. The Cummins ISB might fall from 380 to 350 hp from a 2 - 3 gear upshift.

Whereas on a gasser, a gear shift can loose 2000 - 3000 rpm. The worst in a modern transmission is probably the RAM's ancient 545RFE, a 1st to 2nd shift will fall from 5500 to 3500 rpm, cutting the HEMI from 395 down to 250ish hp.

To simply math, you could say the an ISB would be averaging 365hp during a highway merge, and the HEMI averaging 325hp.

With the modern 8spd ZF though, the gap is getting closer and closer...

bimbert84 wrote:
I simply don't understand the compulsion to compare these engines at the same RPM. It's like comparing a running back to a wide receiver but never throwing a pass. That's not a deficiency of the wide receiver -- it's a misuse of his abilities. The same is true with running a gas engine at low RPMs when power is needed. Why would you do that?

The entire purpose of the transmission is to put the engine's power to the ground, yet so many people choose to ignore this. A better spreadsheet would be one that shows maximum available power at any given road speed. Do this and you'll find the diesel and gas engines will be running different RPMs (because they'll be using different gears) at the same road speed.

-- Rob

Totally agree with you, except when one specific set of factors are looked at: fuel efficiency and engine longevity.

Theoretically, you can put a 505hp LS7 smallblock into a Peterbilt, and it'll pull as well as a 500hp ISX, given proper gearing. But whereas the ISX gets 6 mpg an lasts 800k miles, the LS7 would be lucky to get 3 mpg and lasts 20k miles (the highest record for all track miles, similar duty cycle to heavy towing).

I've always stated, the day when we have an affordable generator-traction motor setup like locomotives, is the day when the torque vs hp argument will end.

A locomotive doesn't care if it's a diesel with 100,000 lb-ft, or gas turbine with 3000 lb-ft, you deliver 6000 hp, and it'll drag that heavy coal train up the grade!

bimbert84 wrote:
I did read it again. The 3.0L diesel makes 240 hp, the 5.7L Hemi makes 395 hp. I acknowledge that power doesn't exist across the entire RPM range, but it's just not accurate to say the diesel is the more powerful of the two.

I didn't say the diesel was the most powerful of the two. I said the opposite. Are you sure you aren't the guy who wrote that Chev quiet cab add? Read it again.

I simply don't understand the compulsion to compare these engines at the same RPM. It's like comparing a running back to a wide receiver but never throwing a pass. That's not a deficiency of the wide receiver -- it's a misuse of his abilities. The same is true with running a gas engine at low RPMs when power is needed. Why would you do that?

The entire purpose of the transmission is to put the engine's power to the ground, yet so many people choose to ignore this. A better spreadsheet would be one that shows maximum available power at any given road speed. Do this and you'll find the diesel and gas engines will be running different RPMs (because they'll be using different gears) at the same road speed.

Because you can't run the gas engine at low RPM's and make the same power as the diesel. Below 3500 RPM the diesel will make more power in any gear. That's the point. The diesel makes more power at lower RPM allowing it to pull in higher gears at lower engine speeds more efficiently. True, you don't have the same maximum performance capability but it makes for a more relaxed drive and less shifting. Throw in 30% better fuel efficiency and it becomes pretty appealing to a lot of people.

Why not compare them at the same rpm? Test 'em both at 4500. :)

jus2shy wrote:

both 6.7's produce far more horsepower at far lower RPM's while the gas motors take a while before they hit their horsepower band. So say you need 200 HP to pull a trailer, the Diesels have that power available at 1500rpm up to their respective redlines. The ecoboost makes that power at 2500rpm while the 6.2L ford takes all the way until 3100 rpm before it's making that power.

Sure.

jus2shy wrote:

This is all assuming a 1:1 engine to drive ratio.

And this is where this line of thinking falls apart.

jus2shy wrote:

Gearing makes up for these deficiencies though but it just shows shy Diesels have so much more oooomph!

It's not a deficiency. It's a difference in the way the engines operate.

I simply don't understand the compulsion to compare these engines at the same RPM. It's like comparing a running back to a wide receiver but never throwing a pass. That's not a deficiency of the wide receiver -- it's a misuse of his abilities. The same is true with running a gas engine at low RPMs when power is needed. Why would you do that?

The entire purpose of the transmission is to put the engine's power to the ground, yet so many people choose to ignore this. A better spreadsheet would be one that shows maximum available power at any given road speed. Do this and you'll find the diesel and gas engines will be running different RPMs (because they'll be using different gears) at the same road speed.

-- Rob