Mistaken ideas about how a diesel engine works

[Turtle_n_Peeps]

I've seen a lot of grumbling as of late about the power output of new diesel engines.
These same people complain and ask why the manufactures have to run the power up so much and why don't they work on fuel economy.

The answer is simple: A diesel engines power output is in direct proportion to the amount of fuel it burns.

In other words: If you have a 500 HP diesel pickup and you only use 100 HP, it will only burn 100 HP worth of fuel. If you're WOT, you will burn 500 HP worth of fuel.

Case in point: A friend has a Cummins that is bombed. Intake, twin snails, studs, exhaust, cam and a few other goodies. Dyno'ed at 525 to the rear wheels. This truck will pull down 23 MPG on the hiway all day long at 65 MPH. Why? Because he is only running about 60 HP worth of fuel through it at that speed and load. Now if he puts a heavy trailer on the tail and tries to climb a 12% hill at 75 MPH; guess what? He will burn 525 HP worth of fuel doing it.

Another case in point: I keep books on all of my fuel stops over the years when I'm on vacation.
I have a 93 200 HP 6.5 diesel and an 06 360 HP Dmax diesel. I have pulled my TT many years with both. The 6.5 would get 12 MPG pulling the TT. My Dmax gets........are you ready..........12 MPG pulling the same trailer.

The Dmax gets a little bit better mileage because it has a 6 speed tranny where the 6.5 has a 4 speed. The 6.5 gets a little bit better fuel mileage because it can only flow 200 HP worth of fuel at WOT where the Dmax can burn 360 worth of fuel. So all in all, over all the years they both average 12 MPG in 10's of thousands of miles.

So, if you buy a new diesel stop bitchin about the HP and mileage deal. You want better mileage with your new 440 HP pickup? Use only 275 or 300 or 325 HP worth of fuel. To do this you are going to have to slow down; even on the hills.

Remember; if you only flow 300 HP worth of fuel you will only burn 300 HP worth of diesel. IOW's "you" are in control of how much fuel your new high HP diesel burns, not the manufacture! 🙂

[ShinerBock]

Turtle n Peeps wrote:
That's true Shiner but that's a % number.

IOW's the 2500 lost 13 more HP than the ED. That 13 HP has to be accounted for in the burning of 13 HP worth of fuel.

And who knows if the fan was lockup up on the dyno? Big fans take big HP away from the engine. It's a lot easier to keep 240 HP cool instead of 370 or even almost 400 in the case of the newest HP Cummins. Another problem is the rea

Look at the chart on page 10 of this Cat study. Over a 50 HP loss on a RW pusher! That's a bunch! I know I have read dyno charts on my 06 Dmax and the fan on it will take away about 27 HP when it kicks on.


All of these things that help duty cycle on the 2500 will take away from efficiency. Lighter duty parts will help the efficiency of the 1500 big time.

At would be interesting to see the BSFC figures of both engines. Just the engines. No drive train or any of that. I know of no way to get those figures though. :M

So is 13 more hp and slightly lighter parts going to account for 8.5 mpg unloaded and 3.64 mpg loaded? I think not.

[Turtle_n_Peeps]

That's true Shiner but that's a % number.

IOW's the 2500 lost 13 more HP than the ED. That 13 HP has to be accounted for in the burning of 13 HP worth of fuel.

And who knows if the fan was lockup up on the dyno? Big fans take big HP away from the engine. It's a lot easier to keep 240 HP cool instead of 370 or even almost 400 in the case of the newest HP Cummins. Another problem is the rea

Look at the chart on page 10 of this Cat study. Over a 50 HP loss on a RW pusher! That's a bunch! I know I have read dyno charts on my 06 Dmax and the fan on it will take away about 27 HP when it kicks on.


All of these things that help duty cycle on the 2500 will take away from efficiency. Lighter duty parts will help the efficiency of the 1500 big time.

At would be interesting to see the BSFC figures of both engines. Just the engines. No drive train or any of that. I know of no way to get those figures though. :M

[ShinerBock]

Adam R wrote:
Shiner,

We keep talking past one another. I agree, the 3.0 Eco is better optimized for lighter loads, no disagreement there. There is a 7 mpg difference between a V-6 and V-8 Camaro too. Same chassis, different engine that is designed to provide a different driving experience. Hook 14K up to the Eco diesel and you've just become a public nuisance and a danger to others on the road and mileage will be nearly equal to a 6.7. Getting 30 mpg out of a 6.7 is going to be tough unless you can de-activate a few cylinders and yes, I've seen the article where they lowered the cD to the point where it could eek out 30 mpg. Not practical for most of us, but you'll always get better mpg by reducing the amount of air a vehicle has to move through.

Why would anyone hook up 14k to an Ecodiesel when it is only rated for 9,200 lbs at the most? That is not reality.

Think about what you just stated here. You stated "Getting 30 mpg out of a 6.7 is going to be tough unless you can de-activate a few cylinders". By taking away cylinders, you lower the engines effective displacement which is exactly what I have been saying that you would have to lower displacement in order to attain greater fuel economy as you increase the engines ability to burn fuel more efficiently. Also, you can do the exact same thing you are stating to an Ecodiesel and get even better fuel economy out of it.

Adam R wrote:
If an Eco does what you need a truck to do, then that is the tool for you. Bottom line is that a 3.0 Eco that puts out 900 ft lbs and backed up a factory warranty is not likely any time soon.

LOL! I don't own an Ecodiesel. I own a 2014 2500 6.7L Cummins. What I own does not change my argument because what I am arguing is based on facts and not bias. I am also not talking about getting unrealistic power levels out of the Ecodiesel and I am not sure why it is even apart of the your response. What I have been saying is....."As technology allows a big liter 6.6/6.7L diesels to gain more energy out of a drop of fuel, its power will increase along with a moderate increase in efficiency. If you want to keep the power the same while having a greater increase in fuel economy, then you would have to go to a smaller displacement engine as fuel efficiency technology improves(i.e. the more energy you are able to get out of a drop of fuel)."

Adam R wrote:

And, the there still a weight and cD difference in the comparison between the 1500 and 2500 so it's still not exactly apples to apples. Not necessarily a bad comparison, but I'll gladly give up a few mpg for a far more capable truck.

Adam

The example that RRinconVTR gave where you agreed and said "Yep, good comparison and more inline with what I've been trying to get the point across" was not apples to apples either yet you agread with that... In fact, I would argue that my example would be more comparable to the topic at hand.

[Adam_R]

Shiner,

We keep talking past one another. I agree, the 3.0 Eco is better optimized for lighter loads, no disagreement there. There is a 7 mpg difference between a V-6 and V-8 Camaro too. Same chassis, different engine that is designed to provide a different driving experience. Hook 14K up to the Eco diesel and you've just become a public nuisance and a danger to others on the road and mileage will be nearly equal to a 6.7. Getting 30 mpg out of a 6.7 is going to be tough unless you can de-activate a few cylinders and yes, I've seen the article where they lowered the cD to the point where it could eek out 30 mpg. Not practical for most of us, but you'll always get better mpg by reducing the amount of air a vehicle has to move through.

If an Eco does what you need a truck to do, then that is the tool for you. Bottom line is that a 3.0 Eco that puts out 900 ft lbs and backed up a factory warranty is not likely any time soon.

Is big hp doable out of a 3.0L engine? Look at what the Mercedes guys are doing with M606 engines. 500hp is doable with a few mods, so it can be done, but I'm not sure if the Eco 3.0 could be taken to the same levels and survive for long.

And, the there still a weight and cD difference in the comparison between the 1500 and 2500 so it's still not exactly apples to apples. Not necessarily a bad comparison, but I'll gladly give up a few mpg for a far more capable truck.

Adam

[ShinerBock]

Turtle n Peeps wrote:

ShinerBock wrote:

Adam R wrote:

RinconVTR wrote:
A C&D mag not long ago showed cars/trucks from 20 years ago compared to now. Time and time again, HP/TQ we vastly increased, and MPG was flat-lined.

Diesels pre-2006 we mostly true diesels and could deliver good power with good fuel economy. Today they deal with tough emission standards and have a scary and costly array of components to scrub and chemically clean what comes out the tail pipe. It's insane, and it doesn't result in loss of power exactly, it results in less fuel economy. They might beat gassers still, but the gap has closed drastically as I'm seeing real world towing reports that average only 10% better than gas, if that. Then enter the debate of cost to own.

Regarding MPG of various HP motors...first of all no one is using all available power unless they are WOT. Which SO many people are afraid to do, for fear they are hurting their motor. I am not afraid of WOT.

For more than 2 seasons each, I towed the very same aero shape TT weighing 4300lbs loaded, with a Honda Pilot and Toyota Sequoia.

The Pilot has a 3.5L V6 and the Sequoia a 5.7L V8. Roughly 250hp (Gen2 Pilot) vs 380hp.

They both returned the VERY SAME MPG AVERAGE while towing.

Not towing, I would commonly see 20-22mpg. The Sequoia I commonly see 15-16mpg.

Yep, good comparison and more inline with what I've been trying to get the point across. Comparing the 3.0 Eco to a modern 6.7, I would agree the 3.0 Eco would get slightly better mileage than the 6.7 in the same pickup if placed in a 3500 MC, until you put a huge load behind it. The 3.0 does not have any margin for carrying or moving loads at the upper end of a 3500's rated capabilities. The 3.0 is better optimized for smaller loads and commuting duties, but you cannot expect it to safely pull an 18,000 lb trailer which requires more HP, a heavier chassis, etc.

For another mileage comparison, I have a 1984 Toyota 2L (2.4L)diesel 4x4 pickup. It came NA and returned a whopping 20-21 mpg. I grafted a turbo and intercooler onto it, cranked up it's fuel screw and doubled it's rated hp output (21 lbs of boost) to achieve 28 mpg on the highway. This is 1984 technology mind you and since I've been driving it for 21 years, I'm pretty familiar with it. I now drive a 2007 Ford S-Max 1.725L turbo diesel and I get 40-42 mpg which is a little disappointing since the S-max is far lighter, smaller and much more aerodynamic than my clapped out Toyota. This all goes to say that other than exhaust cleaning advances, I would say the technology to burn fuel has not grown by leaps and bounds. A little yes, but not a lot.

Actually the loaded and unloaded testing of the two engines like RinconVTR is saying has already been done a few years ago by Truck Trend. They did a 500 mile test loop both unloaded with the Ecodiesel netting 28.47 mpg and the Cummins 19.97. That is in no way shape or form a slight difference in mpg.

Then they loaded up the same 7,020 lbs up to both trucks on a 260 mile test loop. The Ecodiesel did struggle a bit and lost speed going up a 7% grade, but it returned 19.46 mpg. The Cummins of course did not struggle one bit pulling it with ease, and it returned 15.82 mpg.

2014 Ram 1500 EcoDiesel vs. 2014 Ram 2500 - Sibling Rivalry

All of that energy (fuel) is being used up by the drive train. It takes a lot of energy to turn a super heavy crankshaft and torque converter and tranny internals and super big and heavy drive shaft and rear end gears and on it goes...........They need that super heavy crankshaft and everything in back of it to keep the duty cycle up. Can you make 450 HP from the 3.0? Sure! But the duty cycle would go to hell and it would no longer be a HD pickup.

In the dyno portion of that review, the Ecodiesel had a greater drive-train parasitic loss(19%) than the Cummins(16%) in comparison to factory crank numbers.

[Turtle_n_Peeps]

ShinerBock wrote:

Adam R wrote:

RinconVTR wrote:
A C&D mag not long ago showed cars/trucks from 20 years ago compared to now. Time and time again, HP/TQ we vastly increased, and MPG was flat-lined.

Diesels pre-2006 we mostly true diesels and could deliver good power with good fuel economy. Today they deal with tough emission standards and have a scary and costly array of components to scrub and chemically clean what comes out the tail pipe. It's insane, and it doesn't result in loss of power exactly, it results in less fuel economy. They might beat gassers still, but the gap has closed drastically as I'm seeing real world towing reports that average only 10% better than gas, if that. Then enter the debate of cost to own.

Regarding MPG of various HP motors...first of all no one is using all available power unless they are WOT. Which SO many people are afraid to do, for fear they are hurting their motor. I am not afraid of WOT.

For more than 2 seasons each, I towed the very same aero shape TT weighing 4300lbs loaded, with a Honda Pilot and Toyota Sequoia.

The Pilot has a 3.5L V6 and the Sequoia a 5.7L V8. Roughly 250hp (Gen2 Pilot) vs 380hp.

They both returned the VERY SAME MPG AVERAGE while towing.

Not towing, I would commonly see 20-22mpg. The Sequoia I commonly see 15-16mpg.

Yep, good comparison and more inline with what I've been trying to get the point across. Comparing the 3.0 Eco to a modern 6.7, I would agree the 3.0 Eco would get slightly better mileage than the 6.7 in the same pickup if placed in a 3500 MC, until you put a huge load behind it. The 3.0 does not have any margin for carrying or moving loads at the upper end of a 3500's rated capabilities. The 3.0 is better optimized for smaller loads and commuting duties, but you cannot expect it to safely pull an 18,000 lb trailer which requires more HP, a heavier chassis, etc.

For another mileage comparison, I have a 1984 Toyota 2L (2.4L)diesel 4x4 pickup. It came NA and returned a whopping 20-21 mpg. I grafted a turbo and intercooler onto it, cranked up it's fuel screw and doubled it's rated hp output (21 lbs of boost) to achieve 28 mpg on the highway. This is 1984 technology mind you and since I've been driving it for 21 years, I'm pretty familiar with it. I now drive a 2007 Ford S-Max 1.725L turbo diesel and I get 40-42 mpg which is a little disappointing since the S-max is far lighter, smaller and much more aerodynamic than my clapped out Toyota. This all goes to say that other than exhaust cleaning advances, I would say the technology to burn fuel has not grown by leaps and bounds. A little yes, but not a lot.

Actually the loaded and unloaded testing of the two engines like RinconVTR is saying has already been done a few years ago by Truck Trend. They did a 500 mile test loop both unloaded with the Ecodiesel netting 28.47 mpg and the Cummins 19.97. That is in no way shape or form a slight difference in mpg.

Then they loaded up the same 7,020 lbs up to both trucks on a 260 mile test loop. The Ecodiesel did struggle a bit and lost speed going up a 7% grade, but it returned 19.46 mpg. The Cummins of course did not struggle one bit pulling it with ease, and it returned 15.82 mpg.

2014 Ram 1500 EcoDiesel vs. 2014 Ram 2500 - Sibling Rivalry

All of that energy (fuel) is being used up by the drive train. It takes a lot of energy to turn a super heavy crankshaft and torque converter and tranny internals and super big and heavy drive shaft and rear end gears and on it goes...........They need that super heavy crankshaft and everything in back of it to keep the duty cycle up. Can you make 450 HP from the 3.0? Sure! But the duty cycle would go to hell and it would no longer be a HD pickup.

My 5.7 diesel can pull down 28 to 30 MPG in a six thousand lb car on the hwy at 55 MPH. It has a very small light duty tranny, (350L) and a tiny rear end. I'm thinking of putting that engine in my 56 Chevy sedan delivery and see what kind of mileage it will get in a 3000 lb car with a 700R4 in back of it. :E Of course it only has 105 HP so this car won't be setting any speed records. 😉 But 30+ MPG driving to work would be nice in that car. And I can even run it on UMO or ATF if I want. That would make driving to work almost free! Not a bad gig!

This is a diesel discussion but just to give an example of how good things are: I had to have my BMW smogged when I bought it. When the guy was doing the smog test I was standing right next to the machine. He kicked it on to do the test and the HC's were registering ZERO! Zero HC's were coming out of the pipe! I thought something was wrong with the machine and mentioned it to the guy doing the test. He said no, everything is fine and your car is in really good shape! I want everybody that says the manufactures need to make engines better to think about that. There were no HC's coming out of the pipe. None, zero. That means every single drop of fuel was being burned. Not even one one thousandth HC's was coming out of the pipe! That's crazy!

[ShinerBock]

Adam R wrote:

RinconVTR wrote:
A C&D mag not long ago showed cars/trucks from 20 years ago compared to now. Time and time again, HP/TQ we vastly increased, and MPG was flat-lined.

Diesels pre-2006 we mostly true diesels and could deliver good power with good fuel economy. Today they deal with tough emission standards and have a scary and costly array of components to scrub and chemically clean what comes out the tail pipe. It's insane, and it doesn't result in loss of power exactly, it results in less fuel economy. They might beat gassers still, but the gap has closed drastically as I'm seeing real world towing reports that average only 10% better than gas, if that. Then enter the debate of cost to own.

Regarding MPG of various HP motors...first of all no one is using all available power unless they are WOT. Which SO many people are afraid to do, for fear they are hurting their motor. I am not afraid of WOT.

For more than 2 seasons each, I towed the very same aero shape TT weighing 4300lbs loaded, with a Honda Pilot and Toyota Sequoia.

The Pilot has a 3.5L V6 and the Sequoia a 5.7L V8. Roughly 250hp (Gen2 Pilot) vs 380hp.

They both returned the VERY SAME MPG AVERAGE while towing.

Not towing, I would commonly see 20-22mpg. The Sequoia I commonly see 15-16mpg.

Yep, good comparison and more inline with what I've been trying to get the point across. Comparing the 3.0 Eco to a modern 6.7, I would agree the 3.0 Eco would get slightly better mileage than the 6.7 in the same pickup if placed in a 3500 MC, until you put a huge load behind it. The 3.0 does not have any margin for carrying or moving loads at the upper end of a 3500's rated capabilities. The 3.0 is better optimized for smaller loads and commuting duties, but you cannot expect it to safely pull an 18,000 lb trailer which requires more HP, a heavier chassis, etc.

For another mileage comparison, I have a 1984 Toyota 2L (2.4L)diesel 4x4 pickup. It came NA and returned a whopping 20-21 mpg. I grafted a turbo and intercooler onto it, cranked up it's fuel screw and doubled it's rated hp output (21 lbs of boost) to achieve 28 mpg on the highway. This is 1984 technology mind you and since I've been driving it for 21 years, I'm pretty familiar with it. I now drive a 2007 Ford S-Max 1.725L turbo diesel and I get 40-42 mpg which is a little disappointing since the S-max is far lighter, smaller and much more aerodynamic than my clapped out Toyota. This all goes to say that other than exhaust cleaning advances, I would say the technology to burn fuel has not grown by leaps and bounds. A little yes, but not a lot.

Actually the loaded and unloaded testing of the two engines like RinconVTR is saying has already been done a few years ago by Truck Trend. They did a 500 mile test loop both unloaded with the Ecodiesel netting 28.47 mpg and the Cummins 19.97. That is in no way shape or form a slight difference in mpg.

Then they loaded up the same 7,020 lbs up to both trucks on a 260 mile test loop. The Ecodiesel did struggle a bit and lost speed going up a 7% grade, but it returned 19.46 mpg. The Cummins of course did not struggle one bit pulling it with ease, and it returned 15.82 mpg.

2014 Ram 1500 EcoDiesel vs. 2014 Ram 2500 - Sibling Rivalry

[Dadoffourgirls]

It will be interesting to see when GM releases the 2017 Express with the 2.8 Diesel and 8 speed transmission in early 2017 what the fuel economy will be.

If the arguments are true, it should drastically improve the fuel economy and still allow the van to be utilized as a work tool.

[Adam_R]

RinconVTR wrote:
A C&D mag not long ago showed cars/trucks from 20 years ago compared to now. Time and time again, HP/TQ we vastly increased, and MPG was flat-lined.

Diesels pre-2006 we mostly true diesels and could deliver good power with good fuel economy. Today they deal with tough emission standards and have a scary and costly array of components to scrub and chemically clean what comes out the tail pipe. It's insane, and it doesn't result in loss of power exactly, it results in less fuel economy. They might beat gassers still, but the gap has closed drastically as I'm seeing real world towing reports that average only 10% better than gas, if that. Then enter the debate of cost to own.

Regarding MPG of various HP motors...first of all no one is using all available power unless they are WOT. Which SO many people are afraid to do, for fear they are hurting their motor. I am not afraid of WOT.

For more than 2 seasons each, I towed the very same aero shape TT weighing 4300lbs loaded, with a Honda Pilot and Toyota Sequoia.

The Pilot has a 3.5L V6 and the Sequoia a 5.7L V8. Roughly 250hp (Gen2 Pilot) vs 380hp.

They both returned the VERY SAME MPG AVERAGE while towing.

Not towing, I would commonly see 20-22mpg. The Sequoia I commonly see 15-16mpg.

Yep, good comparison and more inline with what I've been trying to get the point across. Comparing the 3.0 Eco to a modern 6.7, I would agree the 3.0 Eco would get slightly better mileage than the 6.7 in the same pickup if placed in a 3500 MC, until you put a huge load behind it. The 3.0 does not have any margin for carrying or moving loads at the upper end of a 3500's rated capabilities. The 3.0 is better optimized for smaller loads and commuting duties, but you cannot expect it to safely pull an 18,000 lb trailer which requires more HP, a heavier chassis, etc.

For another mileage comparison, I have a 1984 Toyota 2L (2.4L)diesel 4x4 pickup. It came NA and returned a whopping 20-21 mpg. I grafted a turbo and intercooler onto it, cranked up it's fuel screw and doubled it's rated hp output (21 lbs of boost) to achieve 28 mpg on the highway. This is 1984 technology mind you and since I've been driving it for 21 years, I'm pretty familiar with it. I now drive a 2007 Ford S-Max 1.725L turbo diesel and I get 40-42 mpg which is a little disappointing since the S-max is far lighter, smaller and much more aerodynamic than my clapped out Toyota. This all goes to say that other than exhaust cleaning advances, I would say the technology to burn fuel has not grown by leaps and bounds. A little yes, but not a lot.

[Lessmore]

dodge guy wrote:

sparechange wrote:

dodge guy wrote:
I think the big thing that some of us are saying is too stop with the HP wars, hold them where they are at and work on mileage instead. I see no reason why the new crop of diesels can't get at least 3+ more MPG! If they they put the effort into that instead of power lots more people would sit up and take notice.

Years ago they said a gas V-8 would never get better than 20 mpg. Guess what mid 20's is what they are now getting!

I agree with most everything you said accept the modern v-8 getting over 20. There's a website that tracks user uploaded mpg by vehicle and year (fuelly.com) and from what I've seen most on average are worse than diesels. Usually around 15-16 combined. I could be wrong but I spent a lot of time looking around on there and talking to guys at work with halftons a couple years ago when I was truck shopping

I had a 97 grand marquis that had no problem getting 26 mpg on the highway it had 2.73's. I also had a 93 mustang with the 5.0 and auto with 3.27 gears that would do 25 on the highway. Yes, these aren't trucks but a very modern V-8 or should not have a problem with low 20's in a truck! Even a diesel should be knocking down upper 20's by now. That is of course if they focused on mileage instead of power!

It's a lot about constant cruise. I find if I can keep my rpm at a constant rpm (sometimes easier said than done, but easier where I live ...the flat prairies) that mpg shows a significant improvement.

My wife and I did a 'test' a few years ago. At the time we had a 2007 Toyota Matrix with the 1800cc Toyota 4 cylinder and a 2007 Buick LaCrosse (still have the Buick). The Buick has a 3800cc V6.

On a prairie highway that has very few curves, no stops and on this day, no appreciable wind we found that by setting cruise control on both vehicles (@ 60 mph) and keeping our foot off the gas and the brake...the Buick came within about 1.5 mpg of the Toyota.

Why....the big Buick engine ran at much lower rpm than the smaller Toyota engine, the Buick is low, albeit wide, but has a more streamlined design in the front...the Matrix, kind of narrow, but high.

By keeping both engines at a constant cruise rpm...with little if any fluctuation, the Buick came very close to the Toyota...due to lower rpm (gearing), snippier shape.

Now in town it was a different matter with many a stop and go. The Buick had to move close to a 1000 lbs more from a dead stop...over and over again in heavy traffic. This is a MPG killer.

[RinconVTR]

A C&D mag not long ago showed cars/trucks from 20 years ago compared to now. Time and time again, HP/TQ we vastly increased, and MPG was flat-lined.

Diesels pre-2006 we mostly true diesels and could deliver good power with good fuel economy. Today they deal with tough emission standards and have a scary and costly array of components to scrub and chemically clean what comes out the tail pipe. It's insane, and it doesn't result in loss of power exactly, it results in less fuel economy. They might beat gassers still, but the gap has closed drastically as I'm seeing real world towing reports that average only 10% better than gas, if that. Then enter the debate of cost to own.

Regarding MPG of various HP motors...first of all no one is using all available power unless they are WOT. Which SO many people are afraid to do, for fear they are hurting their motor. I am not afraid of WOT.

For more than 2 seasons each, I towed the very same aero shape TT weighing 4300lbs loaded, with a Honda Pilot and Toyota Sequoia.

The Pilot has a 3.5L V6 and the Sequoia a 5.7L V8. Roughly 250hp (Gen2 Pilot) vs 380hp.

They both returned the VERY SAME MPG AVERAGE while towing.

Not towing, I would commonly see 20-22mpg. The Sequoia I commonly see 15-16mpg.

[drittal]

We are also forgetting the effect displacement has on idling or other low load situations. Like the effect of cylinder deactivation. In the same gear, same Rpm, at idle the 3.0l will use close to half the fuel of a 5.9 given similar efficiencybin those situations.

As pointed out, there are times when too little power is worse than having enough. The RR here used to get F350 with 5.4l for MoW trucks until they realized that loaded down with all their tools and hi-rail equip the v10 actually did better on mileage because the 5.4l was having to spin higher rpm all the time.

If we can get 440/925 and 17mpg out of a 6.7, why can't we get 350/725 and 20mpg from a smaller but capable modern diesel? Plenty of power for all but the biggest of RV.

[jus2shy]

ShinerBock wrote:

They do. The Ecodiesel makes about the same(if not more) horsepower and more torque than the diesels in 1997 and gets upper 20s mpg. While the diesels with same displacement grew in power to more than double of what they used to back then.

This goes back to what I stated earlier. As technology allows a big liter 6.6/6.7L diesels to gain more energy out of a drop of fuel, its power will increase along with a moderate increase in efficiency. If you want to keep the power the same while having a greater increase in fuel economy, then you would have to go to a smaller displacement engine as fuel efficiency technology improves(i.e. the more energy you are able to get out of a drop of fuel).

I was going to say, I think this is the exact approach Walmart took when they designed their "Supertruck" project. The thing gets roughly 10mpg while towing a fully loaded trailer according to the rags I read about it. Uses a smaller ISX12 versus the typical ISX15 (along with numerous other tech, but they down sized the engine).

[dodge_guy]

ShinerBock wrote:

dodge guy wrote:


I had a 97 grand marquis that had no problem getting 26 mpg on the highway it had 2.73's. I also had a 93 mustang with the 5.0 and auto with 3.27 gears that would do 25 on the highway. Yes, these aren't trucks but a very modern V-8 or should not have a problem with low 20's in a truck! Even a diesel should be knocking down upper 20's by now. That is of course if they focused on mileage instead of power!

They do. The Ecodiesel makes about the same(if not more) horsepower and more torque than the diesels in 1997 and gets upper 20s mpg. While the diesels with same displacement grew in power to more than double of what they used to back then.

This goes back to what I stated earlier. As technology allows a big liter 6.6/6.7L diesels to gain more energy out of a drop of fuel, its power will increase along with a moderate increase in efficiency. If you want to keep the power the same while having a greater increase in fuel economy, then you would have to go to a smaller displacement engine as fuel efficiency technology improves(i.e. the more energy you are able to get out of a drop of fuel).

I see your point. I'm just thinking of what hey could do with the current motors!

[ShinerBock]

dodge guy wrote:


I had a 97 grand marquis that had no problem getting 26 mpg on the highway it had 2.73's. I also had a 93 mustang with the 5.0 and auto with 3.27 gears that would do 25 on the highway. Yes, these aren't trucks but a very modern V-8 or should not have a problem with low 20's in a truck! Even a diesel should be knocking down upper 20's by now. That is of course if they focused on mileage instead of power!

They do. The Ecodiesel makes about the same(if not more) horsepower and more torque than the diesels in 1997 and gets upper 20s mpg. While the diesels with same displacement grew in power to more than double of what they used to back then.

This goes back to what I stated earlier. As technology allows a big liter 6.6/6.7L diesels to gain more energy out of a drop of fuel, its power will increase along with a moderate increase in efficiency. If you want to keep the power the same while having a greater increase in fuel economy, then you would have to go to a smaller displacement engine as fuel efficiency technology improves(i.e. the more energy you are able to get out of a drop of fuel).