We dumped our diesel for a gasser.

[mrmossyone]

Originally Posted by SARGE/AF

I think I have seen this in another thread where you have a point trying to be made only using one part of the solution, and not considering the other part that plays into it.
Fact 1; all engines have a power curve where it starts at operating low RPM (not idle) and then as the RPM increases so does power efficiency to peak then tapers off as the RPM continues to climb until the RPM peaks. An engine at max RPM has less power
Fact 2; An engine operating at max RPM will wear out its parts twice as fast as one operating at mid RPM, and 4 times as fast as one using low RPM.
Fact 3; a smaller displacment engine will have to use more power & gas longer to reach its operating torc point, where a larger displacment engine uses a little less power to reach torc but will reach it faster, both will use the fuel to reach that point.
Fact 4; that mentioned in #2 does not dictate fuel economy, what dictates the fuel economy is which one reachs that point the quickest thus easeing off the gas quicker.
Fact 5; it does not matter whether an engine is gas or diesel the fuel economy can not be found without adding the gearing into the solution. 3 engines exactly the same will have different results if one is attached to a low geared trans & rear end, the other to high geared trans & rear end, the other attached to mid range trans & rear end. Reason is because the gearing dictates whether they are operating below, above, in the max power curve. Another secondary solution to gearing is the set up between the trans & rear end:

Just thought I would throw this into the mix, now maybe a certified mechanic in here can give better explanations as to how these set ups have a influence on fuel economy as well as what the best set up for peak effiency, fuel, engine wear.

Sarge

Now this is what I have always heard, learned from experience and believed. I have had a few motorcycles dynotuned and all of them increase in power until a certain rpm and then level off or lose power. I had one bike in particular that I knew I needed to shift at or just before 5200 rpm's(this bikespeak in it's torque curve)otherwise I would lose a little power and acceleration.
Thought I was losing it for a while there.

[mrmossyone]

Originally Posted by Sky

Well done Sarge. I like facts. I have always contended, and stated this in other threads, that best fuel efficiency is achieved when the engine runs at peak torque (the high point of the power curve). Peak torque is ,"The maximum torque a machine can exert, achieved at a certain rpm. After torque peaks, it will decrease with increasing rpm."

The basic reason a peak torque exists, is that every engine has an RPM that it runs the most efficient at. With the hundreds of moving parts in an engine, with varying coefficients of friction, and all the parts reaching different temperatures and expansions, etc. etc., the peak torque is the RPM where all these factors combine to allow the engine to run most efficiently.

It is this RPM (or very close once air resistance is mixed in) that I believe peak fuel efficiency is realized. Just my 2 cents.

This also jives with my experiences. I am however only an amatuer mechanic at best.

[canadianguy]

Originally Posted by ROBERTSUNRUS

Hi, in relation to gas engines only, the best fuel economy would be at the highest vacuum reading and in the highest gear in relation to speed.

What I'm saying is that the best fuel economy is with the lowest vacuum. I think if you actually hooked a vacuum gauge up to your vehicle as you drove you would see that the highest gear ALWAYS gives you the lowest vacuum. Remember that like all good experiments you must only vary the one parameter you are testing for. So same speed, same grade, same temperature and wind directions. Just set cruise control and start shifting. Try it at different speeds.

I humbly ask that the line in bold above be established as fact until somebody states that they have personally performed this test and recieved contrary results. It would be much appreciated if somebody actually does this test so they we can move forward from this point and this can be established as fact based on more than just my integrity, which I'll admit is quite weak from your perspective.

[JimGolden]

I did not read this entire thread. Too long...

I had a Ford Excursion with the Triton V-10. Complete piece of junk. It blew up and Henry wouldn't cover it. No more FoMoCo for me, ever.

I have a Dodge Ram 2500 4x4 long bed quad cab and Cummins. All I do is change oil and drive. No problems at all. Ever.

I also subscribe to "Diesel Power" magazine. Dodge is indeed bringing out a diesel version of the Power Wagon. The review on it was awesome. A real piece of machinery!

The Hemi with the cylinder DeAct is an excellent engine. More power to you with it. (I plan to get a Challenger with that engine) But don't discount the Cummins. It is the only real diesel in a pickup truck out there. It is a true "Medium Duty" engine. I know many people who have owned them. They all say the same thing. Change the oil, put in fuel, and turn the key. That's it. That has been my experience for the past four years.

I pull a 34' Avion that weighs 9600lbs and I can accelerate up any hill I've ever encountered, including the great Smokies. I recently went up a hill in PA that was nearly 15% with a 15mph hairpin turn. I went from 15mph to 60mph in a half mile. The Cummins is a great mill. Period.

OK, off my soapbox

But seriously, you look in Diesel Power at the trucks that run 10 second quarter miles, and there are ten Cummins to any other brand. There's a reason for that. They are stout.

Back to our regularly scheduled programming...

[JimGolden]

OK, I read a few more posts...

Here's the deal: Best economy results when your air to fuel ratio is approximately 14.7 to 1

Best horsepower results when your air to fuel ratio is approximately
12.0 to 1.

As you can see, you need to run a bit rich for best power. You lean it out for best economy.

With a carb, you're stuck running a bit rich. With EFI, the computer should take care of this for you.

In general, an engine is a pump. And whether you have a V8 or a turobocharged 4-cylinder, it takes a certain amount of fuel to produce a certain amount of horsepower. There won't be a huge difference. A V8 has a little more internal friction than a 4-banger, but it's not that much.

That's why a modern Chrysler 300 with cylinder Deact can get 28mpg, yet still give you 350hp when you tromp on the loud pedal.

My wife's old Crown Victoria (soon to be replaced by MoPar) will routinely deliver 26-27 mpg on the highway when cruising at 80 mph simply due to the fact that it only requires X horsepower to go that fast, whether it be from a 4 or an 8. Aerodynamics and weight mean more than the number of cylinders... Power required = fuel burn regardless of configuration.

[RedSHED]

Originally Posted by canadianguy

What I'm saying is that the best fuel economy is with the lowest vacuum. I think if you actually hooked a vacuum gauge up to your vehicle as you drove you would see that the highest gear ALWAYS gives you the lowest vacuum. ...

Not every engine has vacuum at the intake manifold.
'specially the turbo'd engines

For the rest of them... wouldn't you want more vacuum? Or are we saying the same thing. My old Willy's had vacuum powered wipers & defroster which would go like the Dickens at a stop light, but would just about shut off if you tromped the power. In general, the trick is to drive using the least amount of power necessary to get the speed you want.


Actual formulas are pretty involved, I'd guess, although I haven't really done more than just think about it. Have read in a trade journal that 100-200 RPM either side of the peak torque spot is a good place to shoot for, both in steady state and during acceleration. That seems reasonable to me. Of course that number can be hard to pin down.

[canadianguy]

Originally Posted by RedSHED

Not every engine has vacuum at the intake manifold.
'specially the turbo'd engines

I'd like to keep the analysis to naturally aspirated spark ignited gasoline fueled reciprocating four stroke engines. This is proving complicated enough.

I originally brought up the pumping loss thinking that people would recognize right away what it is. I gave the example of how automakers are taking this seriously, I've made some predictions that people can test, such as that a diesel engine inherently has no engine braking, and that vacuum goes down when you shift up. This is proving to be a rather ominous task, getting people to put together what they know, and what they don't know, in the correct way to draw the correct conclusions.

I'll present another way to test the pumping loss: If you have a standard transmission, when your in some gear at high rpm simply release the throttle. That's the pistons trying to suck down on the intake stroke against the vacuum in the manifold. Please read a few posts back.

As far as people asking for equations: The pumping loss is basically [vacuum]*[displacement]*[rpm]
It's actually a little bigger because the vacuum on the pistons is a little higher because of the resistance of the valves. This is exactly the same as the exhaust pumping loss, replace vacuum with exhaust manifold pressure.

I recieved a private message from a forum member that was of a technical nature. I asked that he post it here for all to discuss, but he refused saying that I am being political. I assure you that what I am telling you is fact, and that it's very difficult to have a debate politely when fact is on your side.

[ROBERTSUNRUS]

Hi, some cars several years back had what they called an "Economy Gauge" It was just a vacuum gauge with green, yellow, and red on the face. Green being the highest vacuum reading and the best economy. Once again the best economy would be at the highest vacuum acheived in any given gear. Also, our supercharged Thunderbird had a Vacuum/Pressure gauge that showed vacuum until you gave it heavy throttle, of course, and then read pressure from the blower. As for your "Prediction" it is already a known fact that Diesels don't have any engine braking; That's why they made Jake Brakes.

[ROBERTSUNRUS]

Hi, it sounds good, but peak torque is not the best place for economy. At freeway speeds most gas engines are running at about 1800 to 2200 RPM. When does your engine get it's peak torque? My Navigator gets it's peak torque at a very low 2750 RPM, but most gas engines get their peak torque well above 4,000 RPM; That would put you at well over 100 MPH or more. Does that make sense that your best gas mileage would be at that speed? I don't think so!

[2airishuman]

the last 35 or so posts in this thread have been very weird.

and so far from the original premise that it is LOST from the exchange.

replaced with mixed examples and undefined terms and nonsense facts...

it all has me wondering if the posters aren't sniffing their fuel caps a tad too often...

phrases like best economy, max efficiency, vacuum (vs rate of change in vacuum), peak power, and so on...

actually have REAL definitions, but why go there right!

then there is the famous "all things being equal" phrase, which of course they never are in the many examples provided...

examples that disprove nothing, but also don't prove anything either.

those posts really deserve their own thread...

something like "mixed engine ramblings and other crock pot cooking secrets"...

now FINALLY robertsunrus makes an accurate statement in the sea of other stuff, .

so i'll provide these links again that actually DO have good stuff on this topic and amplify his point...

http://www.airforums.com/forums/586140-post100.html

what's the topic again?

never mind here are some facts to add to this collective...

-while mpg goes down as speed (and surface resistance) increases the curve isn't LINEAR...

-vehicles have a theoretical c/d but the effective drag changes with speed and conditions...

-and the LOWEST fuel economy doesn't come at high speeds, it happens at zero resistance while at idle.

all things being equal, of course.

-when fuel (g or d) is combusted with oxygen not all of the potential/stored hydrocarbon energy (or 02) is converted to heat energy...

-there are ways to IMPROVE this conversion or full extraction of energy, which do improve engine efficiency

-also, not all of the heat from combustion is converted to mechanical energy...

-and there are ways to IMPROVE this conversion too that IMPROVE engine efficiency...

-but regardless of these changes, the gallon of gasoline or diesel will last LONGEST when the engine is turned off

now i could provide an example to support these contentions using...oh,

-a rotary engine with only 1.3 liter of displacement, in a small aircraft that is climbing, but not changing speeds,

-versus a steam powered tractor dragging a plow at 7 mph, down a hill...

-vs a team of oxen pulling a barge over a HILL on the erie canal with 4.10 gearing ...

which runs really CLOSE BY j/c where the a/s factory is located....

and where they used to build mohos with carburated 454s that had a little 'vacuum gauge' on the dash...

the driver could use this gauge to fiddle with fuel economy...

or to watch the vacuum controlled automatic door steps go UP and DOWN...

but i won't.

cheers
2air'






cheers
2air'

[fastrob]

Originally Posted by TIMEMACHINE

I have to thank kevbo and bob for this thread.

After nearly 20,000 miles of towing our Safari 25 FB/SE around our beautiful country with our 2005 Ford PSD FX4 Crew Cab long bed, we said goodbye to the diesel and bought a 2008 Dodge Power Wagon with a Hemi gasser.

Why you ask, who would be stupid enough to go from an ultimate tow machine to a gasser?

.................................................. .................................................. .................................................. .................................................. ...............................................
I am ready for the flaming.

I deleted the meat of the origional post quote to reply to the point of the thread. Timemachine did the smart thing. He got rid of a lemon and bought something he hopes is better. I hope he gets many years of good service from the new rig.
From my point of view his logic sounds great!
Diesel has it's place in long distance, I heard over 25,000 miles per year, and heavy loads, you define a heavy load for yourself. USA Today had an article of a study that indicated that diesel was more efficient than hybrids or gas for energy efficiency. It would not matter what you had if it was a lemon.
A tank of stabilized diesel should last longer in storage than gas. When the poo hits the fan, like it is now, I want to be ready for a supply interruption.
We have both gas and diesel vehicles and a big tank of fuel oil in an energy emergency.
By all means get rid of lemons, make lemonade.

[Ike T]

Originally Posted by canadianguy

I assure you that what I am telling you is fact, and that it's very difficult to have a debate politely when fact is on your side.

Having facts on your side is meaningless if your audience cannot interpret the facts. Your seeming unwillingness to offer more details to your position naturally leads others to be less than enthusiastic in a conversation.

I could say "because 2x = 4, x = 2" all day long, but at some point I would have to explain it in greater detail other than "That's a fact" (Geez, I hope it really is a fact!).

You may be better served by saying what you mean and providing some detailed explanation rather than providing us open-ended questions that so we can figure it all out. People are thinking about your posts, but not from the same reference that you present your information. Some of us just don't quite put it together like you do, and our best efforts to understand fall a little short.

I also agree it's time for a different thread to have a meaningful discussion about some interesting information. Believe me.. I am all for understanding how to improve efficiency from our current 8 to 10 mpg in tow (we don't tow with the usual vehicles). If I could get to 12 mpg in tow, I'd feel at least 20% smarter.

[Safari-Rick]

Briefly, I have the 2007 Dodge 6.7L Diesel. In Los Angeles traffic I'm getting 17.5 mpg. Just finished a trip down to San Diego, CA. It has a few small hills on the way and back. I got 15.8 mpg.

Just saying......

[Sky]

Originally Posted by 2airishuman

the last 35 or so posts in this thread have been very weird.

blah blah blah

Weird! WEIRD! Who you calling weird??

[canadianguy]

Originally Posted by ROBERTSUNRUS

Hi, some cars several years back had what they called an "Economy Gauge" It was just a vacuum gauge with green, yellow, and red on the face. Green being the highest vacuum reading and the best economy.

These gauges really measure the load on the engine, and yes, the load affects the fuel economy. It takes more fuel to make 100HP than it does to make 50HP. I'm talking about the engine using the least fuel to produce a given horsepower. I've seen these gauges as well, and while the overall fuel consumption is going up because the power you are producing is going up, the specific fuel consumption in gallons of fuel per horsepower-hour is going down.

I am not talking about the fuel economy of vehicle as a whole. You're driving conditions determine how much power you need at the rear wheels. I am saying that the most efficient way to make that power is to gear the engine such that it is at full throttle.

So if eliminating the pumping loss doesn't improve fuel economy, then what is it that improves the fuel economy of these multidisplacement engines? I'm glad we have a lot of experts here, this should be answered quickly, and I can learn something new.

Originally Posted by ROBERTSUNRUS

As for your "Prediction" it is already a known fact that Diesels don't have any engine braking; That's why they made Jake Brakes.

Do you now understand why though? I'd like to point out that I never actually new that diesels lacking engine braking. The only difference between a diesel engine and a gasoline engine in braking mode is the intake pumping loss.

[canadianguy]

Originally Posted by Ike T

I also agree it's time for a different thread to have a meaningful discussion about some interesting information. Believe me.. I am all for understanding how to improve efficiency from our current 8 to 10 mpg in tow (we don't tow with the usual vehicles). If I could get to 12 mpg in tow, I'd feel at least 20% smarter.

If somebody starts the thread, I'll participate. Otherwise, I agree, it's best to leave it to rest if people aren't interested.

[ROBERTSUNRUS]

Originally Posted by canadianguy

If somebody starts the thread, I'll participate. Otherwise, I agree, it's best to leave it to rest if people aren't interested.

Hi, speaking for myself, only, I don't understand what you are trying to tell us or in which direction you are trying to lead us. If there was no interest, mostly trying to figuer out what message you are trying to convey, there would not be any responce to your posts. But it needs it's own thread.

And that being said ............................John & Cat / Timemachine I hope you are still loveing and enjoying that new red Dodge Power Wagon Hemi- Gasser.

[azflycaster]

I saw Time's truck at a rally in Quartzsite this past winter. It is one very good looking truck. The red that Dodge uses is very red.

How about an update now that you have been driving the Power Wagon for a while now?

[TIMEMACHINE]

Originally Posted by fastrob

I deleted the meat of the origional post quote to reply to the point of the thread. Timemachine did the smart thing. He got rid of a lemon and bought something he hopes is better. I hope he gets many years of good service from the new rig.
From my point of view his logic sounds great!
Diesel has it's place in long distance, I heard over 25,000 miles per year, and heavy loads, you define a heavy load for yourself. USA Today had an article of a study that indicated that diesel was more efficient than hybrids or gas for energy efficiency. It would not matter what you had if it was a lemon.
A tank of stabilized diesel should last longer in storage than gas. When the poo hits the fan, like it is now, I want to be ready for a supply interruption.
We have both gas and diesel vehicles and a big tank of fuel oil in an energy emergency.
By all means get rid of lemons, make lemonade.

fastrob, thanks for the vote of confidence. The original post really was all about the decisions many of us go through in regard to Tow Vehicles. Gas vs Diesel is just a part of that decision tree. As you pointed out, the Lemon part of my equation was a factor..why?...because for me, there was a significant doubt as to the reliabilty of the Ford diesel option as well as all of the "new" diesel variants due to the new emission standards and ultra low sulfer fuels. I think it is safe to say that most of the new diesels are not getting the same fuel economy of the earlier models..at least that is what I am reading and hearing from owners of 2007 1/2 and 2008 year model diesels.

As you mention, diesels are preferred for heavy loads and high mile usage, as it turns out, the later, high mileage usage, is not in the cards for many of us due to the massive increase in fuel costs. Many of us are taking shorter trips, or at least staying longer in one location once we get there to maximize the fuel spent. So for my situation, the change over to a gasser was good for this reason alone. I didn't use my diesel truck enough before the fuel costs went up, I certainly wouldn't use it enough now given the change.

Originally Posted by azflycaster

I saw Time's truck at a rally in Quartzsite this past winter. It is one very good looking truck. The red that Dodge uses is very red.

How about an update now that you have been driving the Power Wagon for a while now?

Richard,

Thanks for the qualitative support of our very Red truck...we like the color. Of course, most trucks look great pulling aluminum.

As I mentioned above, our travels are far less now with fuel costs taking such a large bite out of a long weekend budget for Airstreaming. It is sad when getting to the campground costs five times more than the camping fee, that is why our last mini-rally was in the alley next to our house. That example is extreme, but we are now pulling our AS no more than 200 miles (round trip) to rallys, where before 500 miles was not too far for a three or four day event. So this year so far, we have less than 2000 miles on the Power Wagon in six months, where last year we had 3000 miles in three months. The Power Wagon's use is about 90% towing.

Overall, we are very happy with the Power Wagon for towing and general around the house utility. The fuel economy is almost exactly what we had from our sick Power Stroke Diesel, 10 mpg towing and around town. The highway mileage is a little bit better at 14 mpg, where the PSD almost never passed 11 mpg. I must repeat for some readers, my PSD was not typical, I am not saying all PSD's get crappy mileage, but it is well know that on a average, PSD's are know to have higher failure/problems than other diesel engines.

The Hemi engine is a fine power-plant and has plenty of HP and torque to pull our Safari at around 7000 lbs, and there is still plenty of spare power, but I would not want to pull more than 8000 lbs in the mountains. The Hemi does have to run at higher RPMs to get to it's peak torque for climbing, but the darn thing kinda likes it, and most would agree that it is made to rev. When I am not towing, the Power wagon is the funnest truck I have ever driven, in fact, it is more fun than some "sports cars" that I have owned.

Dodge makes a fine truck, the looks are a matter of personal preference, the gadgets work great (navigation, bluetooth, remote start, sunroof, winch, locking differentials, disconnecting sway bar for off road crazy stuff) and believe it or not, the ride is firm but not bad for what it is capable of on and off road. As for reliability, oil changes and lube is all she has seen, no defects or problems. I stand by my decision and still happy to be riding in a big red truck.

John

[jacarape]

what the heck is pumping loss? does that happen over 50?

The Power Wagon was probably the coolest truck in American history. I drove one in Virginia, it had a can you believe it, a PTO! And a mechanically driven winch to boot. I believe it was made in the 1940s. I think it still had the original oil in it, farm trucks.