Diesel vs gas......................

[blt2ski]

OK folks, there have been a few to many diesel vs gas threads that have shall we say gone to "Hell and a hand basket"! So if all of you would put in you BEST, no flaming reasons for going gas vs diesel, pro and con, I will either leave your thread, or copy and paste pertinant info to the 4 posts of pro and con of diesel or gas. This can include the GM 8.1 vs Dmax or Ford V-8/10 vs PSD etc too.

Be real and honest in you answers, not hear say, flaming etc PLEASE!

If posts are good ones, I will leave, if inflamatory or trolling in nature, they will be deleted! I will get this stick'd to the top for future parusing for those that need this type of info.

Added 6-23-04

We are getting closer to answers I am looking for etc.

Stuff like Ken's - T-Bone posts are good. There are a few others of you that have not posted, some with a 9 point question and answer type to figure out how you went with one or the other. If you are one of those, PLEASE repost in this thread. I may have to look up whom has done this and PM you, but if you think this is you, you now know what to do.

Also, for those of you with $ per gallon for either fuel right now, I would prefer to see a post with ...."in my area, diesel is typically .10 less than unleaded" then explain your numbers. As currently in the Seattle area, diesel and unleaded are any where from 2.05 -2.30 per gallon, with mid test .10 more and premium about .20 more, with equal high low splits. Two weeks ago those prices were upwards of .30 -.40 per gallon more. people were posting $ per gallon that were for me. "I wish" If someone is reading your post a year from now, they may want to know where your paying 1.65, when the price of fuel is over $3 per gallon. Let's keep prices out of it if possible.

Bert and tin tipi, got into a good discusion on the pros and cons of RPM's, drive train etc. I would prefer to NOT see the quote of the other in responding threads, maybe just write a quick wording of re tranny gearing, instead of the whole 40 words or so in that paragragh, so the repsonse is shorter if possible quicker and easier to read etc.

I have deleted some 15+/- posts, that were off topic etc. Please note, I am trying to keep this at the top, as the ONLY gas/diesel thread in this area. So if one is trying to decide, we do not have to go thru this BS any more. As such, I will be deleting ANY future posts close to resembling this type of topic. I may have to change "this" title to a better one, if one has a better sounding title, to be more positive, better claification, let me know here, or in a PM/e-mail, what ever you feel most comfortible with.

Again thank you for all of you that are keeping responses positive, etc.

Also we could use a few more positive reasons to go gas, as many can see I have both gas and diesel, both have a place! Both have positive reasons to buy that fuel, lets keep the threads etc to that purpose only!

Marty

[BertP]

David, you said "The diesels max power output is at lower rpms" which is dead wrong. They develop their max torque at low rpm, but they develop their max power - measured in HP - at high rpm.

Bert

[DavidPhillips]

BertP wrote:

Jackjagt wrote:
I mean Diesel compared to Gas rigs. The explaination holds.
Your rig's max torque will be at a lower RPM, and thats where you will accelerate or climb fastest. You'll probably turn even lower RPMs at cruise on the level, but in high gear.
Of course at 3000RPM it certainly will sound like it's working harder!

You acellerate hardest at your engine's max HP point, not its max torque point.

Bert

Bert think about what you are saying.

You just got through proclaiming that the max hp is at 3000 rpm.

If the engine is already wide open at rev limit you can not accelerate at all.

You will accelerate more from 1600 rpm. That is where your highest output is.

Simply by law of calculating max hp it is going to be at redline on any engine. Therefore no acceleration at all.

[DavidPhillips]

BertP wrote:

DavidPhillips wrote:
The diesels max power output is at lower rpms (see above). The force is what maintains speed.

And there is the main problem with your argument. My DMax generates its max power at 3000 rpm. You are confusing torque with power.

Bert

Ok Bert,


I'm not confusing torque with horsepower.


The word power by itself does not mean the same thing as horsepower.

The word power by definition can mean controlling influence. it could also be defined as potential to bring about change.

When you tighten a bolt with a wrench you are applying some force to the bolt and it gets tighter. To most people that is considered bringing about change since the bolt is now tighter than it was before. I would also think that it could be called a controlling influence.

But, I will be careful to try and use force or torque if we are confusing it with horsepower.


Towing heavy enough loads you may not even reach max horsepower. The force that keeps the wheels turning is the output of the engine. It can be used to calculate a max horsepower if you want that information. Since we cannot get there towing a heavy load I would prefer to just use the real force calculation.



3000 rpm is the max rpm of the engine therefore it will do the most work at 3000 rpm. That rating is not power. It's horsepower.

Ever see this?

300 p @ 3000 rpm

no we don't. The term is horsepower. 300 hp @ 3000 rpm

Remember that it only relates to how much work could be done if you can stay at that rpm for an hour as compared to a horse.

300 hp means you have a max of the amount of work done by 300 horses that you can do if you stay at the rated rpm of 3000.

[BertP]

Jackjagt wrote:
I mean Diesel compared to Gas rigs. The explaination holds.
Your rig's max torque will be at a lower RPM, and thats where you will accelerate or climb fastest. You'll probably turn even lower RPMs at cruise on the level, but in high gear.
Of course at 3000RPM it certainly will sound like it's working harder!

You acellerate hardest at your engine's max HP point, not its max torque point.

Bert

[Jackjagt]

BertP wrote:

DavidPhillips wrote:
The diesels max power output is at lower rpms (see above). The force is what maintains speed.

And there is the main problem with your argument. My DMax generates its max power at 3000 rpm. You are confusing torque with power.

Bert

I mean Diesel compared to Gas rigs. The explaination holds.
Your rig's max torque will be at a lower RPM, and thats where you will accelerate or climb fastest. You'll probably turn even lower RPMs at cruise on the level, but in high gear.
Of course at 3000RPM it certainly will sound like it's working harder!

[BertP]

Jackjagt wrote:
Torque is what gives you your acceleration

If that is true, why is that when you stomp on the acellerator, the transmission downshifts? Since max torque is developed at a relatively low rpm (typically 1600 - 2000 in a diesel) then it would make most sence to leave the rpm low when you need to acellerate the hardest if max torque is what you need. Downshifting, on the other hand, moves the rpm up to where max HP is generated. Don't you find that odd?

Jackjagt wrote:
and pulling capacity.

Pulling capacity is defined by a whole bunch of things, but HP is more important than torque.

Jackjagt wrote:
HP and T go hand in hand. As the rpm's increase for a given torque, the HP must also increase, and as the HP increases for a given rpm, the torque must increase.

100% correct.

Jackjagt wrote:
Usually, in my engineering calculations, I determine what Torque I need at a given speed, and that gives me the required HP.

And how do you calculate that? The only engineering mesurement given by any of the engine or truck manufactures for a given situation is HP, not torque. Torque tells you nothing without rpm. And, as you pointed out above, put torque and rpm together and you have HP.

Jackjagt wrote:
Usually the max Torque and HP are determine by the required acceleration from zero to a certain speed. E.G. how many seconds do I have to accelerate this load (machine) from zero to, say, 1000rpm (which will represent some Feet-per-minute (fpm) machine speed).

Again, you cannot calculate how much torque you need from an engine to produce a particular rate of acelleration. Only HP can tell you that.

Jackjagt wrote:
Our diesels produce LOTS of torque at lower rpms. That's why they are geared differently than their gasser cousins... to take advantage of that torque.

Of course. So why is that when someone mentions that a gasser downshifts, it is seen as a weakness? The two engines work differently.

Bert

[BertP]

Jackjagt wrote:
The rig with higher torque will reach the top of the hill first. On the level their top speeds would be the same, but the higher torque rig would get there first. IMHO

Why?

Bert

[BertP]

DavidPhillips wrote:
The diesels max power output is at lower rpms (see above). The force is what maintains speed.

And there is the main problem with your argument. My DMax generates its max power at 3000 rpm. You are confusing torque with power.

Bert

[DavidPhillips]

I agree with your opinion.

[Jackjagt]

DavidPhillips wrote:
So Jack what's your opinion on the subject?

Two vehicles towing heavy rigs. Both have 300 HP.
Both pulling same weight. One has higher torque.

If the hill becomes very steep is it possible for one of the vehicles to slow down and the other keep going at the same speed even though they have the same horsepower?

The rig with higher torque will reach the top of the hill first. On the level their top speeds would be the same, but the higher torque rig would get there first. IMHO

[DavidPhillips]

So Jack what's your opinion on the subject?

Two vehicles towing heavy rigs.

Both have 300 HP.

Both pulling same weight.

One has higher torque.

If the hill becomes very steep is it possible for one of the vehicles to slow down and the other keep going at the same speed even though they have the same horsepower?

[Jackjagt]

Diesel vs Gas is partly a debate about Torque vs Horsepower.

Motorhomes find torque very usfull to get up to cruising speed.
But, not being racers, horsepower is less usefull above the level needed for your maximum speed.

Here's the scientific facts as quoted from Kugelsicher at www.thedieselstop.com

HP = (T x RPM)/5252, where T = torque in ft-lb.

Torque is what gives you your acceleration and pulling capacity. HP and T go hand in hand. As the rpm's increase for a given torque, the HP must also increase, and as the HP increases for a given rpm, the torque must increase. Usually, in my engineering calculations, I determine what Torque I need at a given speed, and that gives me the required HP. Usually the max Torque and HP are determine by the required acceleration from zero to a certain speed. E.G. how many seconds do I have to accelerate this load (machine) from zero to, say, 1000rpm (which will represent some Feet-per-minute (fpm) machine speed).

Our diesels produce LOTS of torque at lower rpms. That's why they are geared differently than their gasser cousins... to take advantage of that torque.

[DavidPhillips]

Thats a good point.


I think no one really cares because they have already got what they wanted or will get what they want.

This is basically just some weird form of entertainment.

Nothing against what someone has. As most other people I have several vehicles.

[desrcr]

I think this argument is stupid.
I tow around 10k so does my freind. We arrive at most places together, while drive same route together. Guess a funny thing is we are limited by speed limits and road conditions.
Guess which one I drive? Also who cares?

[DavidPhillips]

BertP wrote:

DavidPhillips wrote:
Commonly refered to as the power band, the rpm range where an engine makes at least 75% of its maximum torque.

OK, let me be more specific: What do you mean by "use up some force in the driveline" and "lower output from the engine at the point in time that it is out of it's peak operating range"?

That was in reference to the statement about nothing wrong with a gasser shifting to stay into it's power band. Every time you shift you use a clutch. This adversly changes the ratio of engine output to the ground no matter what gears you have.

I already explained the peak operating range, or power band.

BertP wrote:

DavidPhillips wrote:
Diesel engines have their torque peak quite low in their speed range usually between 1600-2000 rpm. This allows the diesel engine to be given higher loads at low speeds than a gasser.

What difference does the rpm make? We have transmissions to compensate for the lack of power at low rpm and both gassers and diesels need them.

For one, the shifting out of the peak rpm thing again.

Secondly you asked, so I told you.

BertP wrote:

DavidPhillips wrote:
We already agreed that enough resisting force would cause a vehicle to downshift. At some given resistance the diesel will not downshift and the gasser will. This is due to the greater force of the diesel.

BertP wrote:

And? What difference does that make?

Please read the downshifting answer again.

Bert wrote:

DavidPhillips wrote:
It looks like you already agreed to that as well.

BertP wrote:

Yes, we did.

BertP wrote:

DavidPhillips wrote:
It seems pretty clear to me, but I will try to elaberate.

An engine outputs more force in a certain rpm range also refered to as it's power band.

Even if it stays within that power band all of the time the power band
has a high point somewhere along it. When they rate an engine they give max values. At other rpms than the point where it is at the max output you will not get max output.

If you are dropping in and out of that rpm then the overall output of the engine will be lower than if you could run in one gear and maintain the rpm where the maximum output is.

So if you are changing gears you are droping into a lower part of the power band with a gasser.

Since a diesel's max power is always at its max rpm point, the shifting you are referring to will adversly affect a diesel more than a gasser. Be that as it may, though, what difference does it make? We have to have transmissions.

Bert

The diesels max power output is at lower rpms (see above). The force is what maintains speed.

resistance = force vehicle maintains speed


Not really concerned with what you are calling power here if it's horsepower. We cannot achieve max horsepower with enough resistance to force which is what we have towing up a hill.

Read the whole zebra story again.

We have transmissions to keep the engine in the power band, the more you use the clutch to stay in that power band the more loss of output you have. Shifting is not a good thing if it could be avoided.

We do not have the option of a transmission that does not shift yet in these trucks. One day we will.




Also, lets try not to keep bringing up the fact that if you modify the gears you can make the gasser better at towing.

We were trying to use identical rigs.

We are talking as is from factory. The gasser has a different diff so it gets the same tow rating.

Anyway by doing that you would really screw it up for normal driving.