Gas engine and Diesel of same specs.Pull the same.

I've owned and towed with an 01' Chevy 2500HD ex/cab/short bed 8.1/A and it was a HOSS!!! I out ran same year D/A's with the 8.1, (hey, I was only 51 then:)), BUT, the 8.1 got the worse mpg empty or towing than any diesel I've EVER owned, including dually's I've owned. I don't know anything about earlier 5.9 Cummins power trucks, other than thinking they were really loud. But dusted more than several of those with the 496 powered Chevy as well as many a Ford....hey, that truck could RUN!! BUT again, mpg was horrible. Thus, In 03' I went with same configured 3/4 ton Chevy with D/A and it ran really well, but no comparison for mpg...diesel won that hands down, towing, comparing the two, back then was about the same from what I remember.

Your decision, your money...go with your gut....Only negative I ever had with the 496 was the mpg

wnjj wrote:

ib516 wrote:
The diesel will pull at lower rpm with much less transmission shifting. It will also get 50% better mpg towing or empty.

Lower rpm = lower road speed, unless you run in a higher gear which means lower torque at the wheel. You can't have it all unless you've got HP. I seriously doubt a stock 235hp diesel with similar torque to a 345hp gas engine would pull as well but I can't say I've had first hand experience. Modded is another story for either engine.

I have had that experience. My '05 345hp/365ftlb Hemi powered 2500HD towed our 10,400 lb 5th wheel faster up the grades than my '03 duplicate 250hp/460ftlb Cummins powered 2500HD. It was at 4500rpm vs 2900rpm, not 5k rpm vs 1800rpm. And we got 2mpg better with the Cummins. Not twice the mileage. A stock 8.1 would run circles around a stock '01 Cummins.

people are crazy if they think a screaming diesel sounds horrible. tis a beautiful sound. should hear the ear piercing whistle coming from my truck going uphill at 45-50 psi. pullin a load. havent used my radio in a long time.

another thing to consider is the wgt of the rotating mass. That alone will give a diesel a big advantage towing. I have yet to have a gasser come close to keeping up on 6/7%. AINT GONNA HAPPEN.

Sport45 wrote:
Horsepower is horsepower. Two prime movers with the same HP will pull the same load up the same hill at the same speed. I don't care if it's gasoline, diesel, electricity, or steam powering them. Just let them operate at the speed they develope that power and ignore the sound they make.

Gasoline does loose some to diesel in thet more gear reduction can mean more parasitic losses and less HP delivered to the ground. The turbocharger also gives the diesel an advantage at higher elevations. the playing field may level if turbocharging becomes popular on larger displacement gasoline engines. A 5.0L ecoboost would be a good 3/4 and 1-ton truck engine for part time towing IMHO.

Sometimes the gasoline engine will win simply because the diesel can't spin fast enough to make the speed while delivering its extra torque to the ground.

Diesel will almost always win the fuel efficiency award. Whether or not it saves enough fuel to pay for itself has to be determined on a case by case basis.

Horsepower is horsepower but you need to look at the torque curve and consider the transmission ratios to have any idea how the truck is going to pull a trailer up a hill. My Ford which has a very flat torque curve will only make max HP at one rpm which means one speed per gear: 21 mph in 1st; 35 mph in 2nd; 54 mph in 3rd; 72 mph in 4th. A gasoline engine which makes its max HP at 4200 rpm (and likely also has a fairly flat torque curve) with the same transmission and rear axle would really only have 2 usable hill climbing speeds: 1st gear at 30 mph or 2nd gear at 51 mph. A highway tractor with a large Cat and an 18 speed transmission will have no problem putting max power to the wheels at any speed. (the big Cat has a torque curve which drops significantly as the engine rpm increases)

The no replacement for displacement is probably still true......BUT, if you compare todays motors to yesterdays. yesterday getting .5 HP per ci was normal, 1hp per cube was great! Today it seems that 1HP per cube is the norm, and getting 1.5 to 2HP is great! Torque is also up to a degree from yesterday too.

So while the quote is good, if you compare a motors of the same vintage, to compare a today motor with yesterdays is not always a good way to look at things!

BUT, as noted, two motors of equal HP, SHOULD pull a load up a given hill at the same speed. This does assume you have a drivetrain that explotes that motors HP strengths! Putting a 6000 rpm 300hp gas rig in a drive train ment for a diesel doing 300hp at 3000 rpm or vice versa, would do neither any good as a comparison. But put the proper setup in ea, both should be about the same speeds up a hill etc.

Also as noted, one WILL use more gas than diesel, but if one compares the BTU's of the fuel used, they should equal the same! Being as gas has 1/3 less btu per gallon, you will use more gas to accomplish the same task, same comparing alcohol, you will use more alcohol that gas which uses more than diesel to get the same job down!

Marty

ramyankee wrote:
By my sig, i pull with a 2002 8.1.....Its specs are roughly 340HP and 455 lb ft of torque. If a guy were to opt for a 2000-2002 Cummins, approx the same specs, does a Diesel pull any easier. Just a thought.
I realize they tow at a much lower RPM.
Thanks. Just curious.

Well many of the diesel heads missed the fact that you can't get a diesel and gas with the same specs, not even close!!
1. HP match 07 to 10 Cummins 6.7 350 HP and minimum 610 to 650ft. lb., then the 11 and 12 is still 350 HP, but up to 800 ft. lb. of torque!
2. Torque match 01 Cummins 235 hp and 460 ft. lb.
3. Displacement Cummins 8.3 240 to 330 HP and 660 to 950 ft. lb. it is at a disadvantage as it ONLY weighs 1,570# :B
4. Fuel economy not even close averages are 8mpg and 12 mpg, do the math at least 50% better and diesel only cost about 10% to 20% more.

The gasser's that have never pulled with a diesel, will never get it, simple as that.

I have a simple timing chip on my 01. state gains 50 hp and 125 ft. lb. so my 01 is theoretically at 285hp and 585ft. lb. of torque.
Still 50 hp short of the 8.1 HP rating, and I pull 11,000# 5er at speed up 6% and 7% grades, with a set of 3.55's!

Edit:

DSteiner51 wrote:
There is no replacement for displacement is what I've seen posted here numerous times. It will be interesting to see if they'll have any comments on this.

Well I would doubt that! My 5.9 (2.2 liters less than an 8.1, 27%)stock has more torque than the 8.1., but just 30% less HP. would agree with you, and it is a very de-tuned vintage.

DSteiner51 wrote:
There is no replacement for displacement is what I've seen posted here numerous times. It will be interesting to see if they'll have any comments on this.

I agree with you, with one exception, which is....unless the displacement is augmented by forced induction such as turbo charging or supercharging.

Cummins12V98 wrote:

JustLabs wrote:

ramyankee wrote:
By my sig, i pull with a 2002 8.1.....Its specs are roughly 340HP and 455 lb ft of torque. If a guy were to opt for a 2000-2002 Cummins, approx the same specs, does a Diesel pull any easier. Just a thought.
I realize they tow at a much lower RPM.
Thanks. Just curious.

You'll use more fuel and RPM to do it,but an 8.1 will run circles around a CTD of that era.

I really doubt that.

Doubt it if you want but that big block would smoke the oil burner of those years. The big block has more than a 1/3 more HP. Would not even be close.

JustLabs wrote:

ramyankee wrote:
By my sig, i pull with a 2002 8.1.....Its specs are roughly 340HP and 455 lb ft of torque. If a guy were to opt for a 2000-2002 Cummins, approx the same specs, does a Diesel pull any easier. Just a thought.
I realize they tow at a much lower RPM.
Thanks. Just curious.

You'll use more fuel and RPM to do it,but an 8.1 will run circles around a CTD of that era.

I really doubt that.