Gas or Diesel

Vulcaneer wrote:

pnichols wrote:

tdeal823 wrote:
Once you have the torque of a diesel at your foot anything else will be like pulling with a KIA.

That's purely a matter of preference and not based on the physics of horsepower conversion.

The only torque that matters is the torque actually being applied to the drive axle(s) ... and what it takes to make that is horsepower conversion by the proper overall vehicle gearing so as to transform that horsepower into drive axle torque.

Diesels pull different than gassers, not intrinsically better than gassers. Thoroughly read and absorb this discussion thread to understand what's really going on with the two different ways of pulling a load:

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27698336/srt/pa/pging/1/page/1

Well....that is NOT the only thing that matters. Nor is the HP conversion. Another important thing is...at what RPM. If it makes the Torque (and HP) at a much lower RPM, then the comfort of towing is much better. And your seat of the pants feeling is much better. That is the biggest difference between diesel and gas towing capability and comfort.

Diesel produces the torque and HP at lower RPM. And the curves are much flatter...from bottom to top of the rpm range.

Vulcaneer, You are wasting your time and effort trying to explain the difference between towing with a lot of HP vs. a lot of Torque.
I move an 11,000# 5er without difficulty at highway speed on both interstates and two lane roads. I do this with about 270 hp and 530# of torque, and 3.55 gears. I can pull 6% and 7% grades at speed in 4th with my 5 speed manual.

You can do the math all you want, but not likely a 270hp gas engine with less torque could do that even with 4.10's or lower.

I rest my case.

rhagfo wrote:
I move an 11,000# 5er without difficulty at highway speed on both interstates and two lane roads. I do this with about 270 hp and 530# of torque, and 3.55 gears. I can pull 6% and 7% grades at speed in 4th with my 5 speed manual.

You can do the math all you want, but not likely a 270hp gas engine with less torque could do that even with 4.10's or lower.

My V10 will easily do the same on the same grades at the same speeds and at 9000 foot altitudes pulling our 11,800 lb. motorhome's weight - I just have put up with (enjoy!) the gear changes and it's 4800 RPM so as to tap more of it's horsepower (305 HP maximum). It's crankshaft torque is probably only around 420 lbs. when doing this -> but proper overall vehicle gearing leverages-up this crankshaft torque to the drive axle torque needed to do this.

So ... it seems that it is unfortunately impossible to discuss diesel versus gasser performance comparisons without throwing away logic/physics/engineering and eventually reverting back to good old preference. This is assuming that one leaves turbo charging out of the discussion - because it's "completely unfair" to compare a turbo charged diesel engine of X horsepower to a non-turbo charged gas engine of the same X horsepower. Engine manufacturers of course nowadays seem to always include turbo charging to their modern diesel engine designs, thus giving diesel owners another explanation as to why, in at least mountain driving, they feel that their diesels pull better - as their engines should do when the air thins out. A turbo charged gas engine continues to put out better horsepower as the altitude increases, too ... but just try to get turbo charging in a truck gasser engine.

pnichols wrote:

rhagfo wrote:
I move an 11,000# 5er without difficulty at highway speed on both interstates and two lane roads. I do this with about 270 hp and 530# of torque, and 3.55 gears. I can pull 6% and 7% grades at speed in 4th with my 5 speed manual.

You can do the math all you want, but not likely a 270hp gas engine with less torque could do that even with 4.10's or lower.

My V10 will easily do the same on the same grades at the same speeds and at 9000 foot altitudes pulling our 11,800 lb. motorhome's weight - I just have put up with (enjoy!) the gear changes and it's 4800 RPM so as to tap more of it's horsepower (305 HP maximum). It's crankshaft torque is probably only around 420 lbs. when doing this -> but proper overall vehicle gearing leverages-up this crankshaft torque to the drive axle torque needed to do this.

So ... it seems that it is unfortunately impossible to discuss diesel versus gasser performance comparisons without throwing away logic/physics/engineering and eventually reverting back to good old preference. This is assuming that one leaves turbo charging out of the discussion - because it's "completely unfair" to compare a turbo charged diesel engine of X horsepower to a non-turbo charged gas engine of the same X horsepower. Engine manufacturers of course nowadays seem to always include turbo charging to their modern diesel engine designs, thus giving diesel owners another explanation as to why, in at least mountain driving, they feel that their diesels pull better - as their engines should do when the air thins out. A turbo charged gas engine continues to put out better horsepower as the altitude increases, too ... but just try to get turbo charging in a truck gasser engine.

If your motor-home is 11,800# loaded then you are missing that my 5er is 11,000#, total GCW that I am moving is 19,000# with the TV.

Horsepower without torque with gears is still equal to horsepower with torque without gears.

As you probably know, many Class A motorhomes weigh what your total weight is and yet are powered by the higher horsepower (three valves per cylinder) 365 HP version of the V10 gasser.

By the way, when I said earlier above what our RV setup (lighter than your total RV setup) with only the 305 V10 version would do - I didn't mean to imply that I was pushing it anywhere near the limit during those times. It has plenty of pulling performance headroom left in any situation I've ever had it in.

(See .... I told you perceived diesel pulling advantage was purely preference based. ;) )

Here is my take on the difference and why people like there diesels.
I only have GM specs readily available.
Four motors crusing down the road at a approxamate 2000 rpm that most would or could cruise at and only needing, I do not know exactly but about 75 to 100 HP to Cruise along.
Now by just pushing the pedal down with no down shift the approxamate maximum HP available is.

2005 Duramax LLY about 225Hp @ 2000rpm

2005 8.1 L18 about 165hp @2000rpm

20?? 6.0 LQ4 about 125hp @ 2000rpm (similar HP on a 2010 L96)

2010 6.2 L9H about 140hp @ 2000rpm


Now as soon as the HP required to maintain that speed is exceeded a down shift would be required to maintain that speed. Now if the next lower gear is or has the required Hp to maintain that speed then there no loss but if the load continues and you have to drop down another gear there will and could be be a greater loss of speed especially with the gas engine.

Do to the higher torque of the diesel and with higher Hp levels availble from just throttle input they are going to pull and feel better doing it.
The gas engine because of its very wide operating RPM range will have or be in more areas were the gearing will not be as optimal, in all high load and speed situations. With that being said with proper gearing and not selecting or towing at the max tow rating the gas can manage very well.

For example the 6.0 dropping down to third on a four speed 4L80E/4.10 gear would be making about 190 HP and to second gear a possible 275 hp. Although these are good they are not near as much HP that the diesel can manage at highway speed limits.

But in the end as the load increases and both the gas and diesel start to slow the diesel has an advantage as the torque starts to climb at a faster longer rate than a gas as the RPM's slow down keeping more HP available.

I do think that part of the love of towing with diesel's is that most but not all are not towing at, or even near the max towing. People with gas seem to want or are stuck to, pushing up to, or tow lot closer to the max ratings.


(The other part is these HP levels they are at sea level, start at 3000 ft and go up to 5000 or 6000 ft and the difference in hp margins between the gas and diesel grow by quite a bit.)

pnichols wrote:
My "preference" is a high RPM engine - not a thumping/rumbling beast. I much preference the spirited whine of the V10 when pulling up grades and accelerating. Nowadays high RPM engines that are also reliable can be mass produced so as to last a long time ... Ford's truck V10 is an example. For several decades this was not the case - so low RPM diesels became popular all over the world for three reasons - reliably back then being one of them. The other two reasons probably being kick in the seat of the pants without gear changes and ease of production of diesel fuel all over the world as compared to the processes required for gasoline.

Having previously owned a 2006 V10 6.8 30V F350, I know where you're coming from. But I cannot agree with your preference. Spent too much time at 4000 RPMs pulling long hills in 3rd, or even second gear. Try pulling 13,000 pounds up over Donner pass sometime. You won't be able to hear your radio. Or much of anything else after you get over the top. Been there, done that, got the T shirt and the hat. My diesel does it so much better.

But I WILL agree there are times when I like the high whine of a gas engine. Like in an Indy or F1 race car, or a race boat, even a lower revving Nascar, a drag racer, and/or a hard accelerating 2 cycle motocross bike. These sound wonderful when each is up on their torque and Horsepower curve. Not so much when they are not.

But there are also times I like the lower rev'ing pull in low end high torque application. Like a 4 stroke enduro motorcycle clawing it's way through heavy trails, while maintaining tractability, a bulldozer pushing a very heavy load, and just digging in and going, and a diesel truck pulling a heavy load, without the noise and sweat of a gasser trying to accomplish the same amount of work in the same amount of time. And I can hear the radio, just fine.

Incidentally, thinking of my old 2 cylinder gas bulldozer. It had only 45 HP and a few hundred foot pounds of torque. But it also had a 120 pound flywheel. You could count the rpm's, when it really got it's back into it. But it just kept going. You could rarely stall it. In fact when the starter broke, I would kick start it by putting a pipe wrench on the PTO shaft and standing on it. Once you got that fly wheel to move, she was going to start. Even when it stopped on the compression stroke, all you have to do is stand on the wrench a little longer. It only had 6:1 compression.

I think it's just more enjoyable to climb a 6% grade and see if the Cummins will hold 6th. I don't find any enjoyment in finding out how high of rpms a gasser will need to keep up with a diesel in the mtns. Seems like a lot of work to me.

rhagfo wrote:
If your motor-home is 11,800# loaded then you are missing that my 5er is 11,000#, total GCW that I am moving is 19,000# with the TV.

Please strike this from the record. rhagfo has already rested his case...
;)

Find me a gaser that has 600# of torque at 1600rpm and still has it at 2500rpm the same year as mine. So far I have not found a hill, mountain that I can't pull at a speed I am comfortable with on any interstate. So far the current crop of trucks don't impress me for the price.

I think most diesel owners are more in love with the turbocharger than the fuel. They just don't realize it.

A NA diesel is a wheezing pig on mountain passes, same as gas. My late father in law pulled his TT with a 6.2l diesel Suburban and I can tell you from experience it was no powerhouse. The gas engines of the day would easily outrun it. They couldn't touch it for fuel mileage though. And diesel was much cheaper than gas back in the day.