It is all in the gearing, when talking about how much power is getting to the ground.

 

I am asking how much better the Pickup truck diesels you owned that are 300 HP or so pulled over your 300 or so HP gas engines when going up a hill and accelerating ?. I know if you keep the revs up on a gas engine and stay in the power band it can go up a hill faster if rated at a higher HP that was stated in another thread for me when I was told the gas motor he was driving would out run the diesel up hill when HP was peaked out.

 

Well, I have a 350hp 5.8 gas motor in my f-100, I'm estimating it puts out around 400lb-ft.

And our 7.3 super duty is at about 320hp, probably around 650-700lb-ft

We went on a combined trip together, same route same time.

I had about a 4,000lb load on my truck, total combined weight of 8,000.

The super duty was pulling about 6,000lbs, and it weighs 8,000 itself. So about 14,000lbs combined.

We wernt racing up the hills, but the 7.3 had the power to leave me in the smoke! If I was able to keep moving, I was fine. I was pulling 50mph in 2nd gear. About 3,000rpm. I wasn't pushing it hard, just pulling...

If I slowed down, it took a LOT to get back up to speed. The diesel, pulling almost twice the overall weight, could speed up, pass, and had absolutely zero problems holding 65mph up the hills. But they were going slow waiting for me.

 

Pocket,
In no way was there an intent to compare or subsitute horsepower for torque or vise-versa just an over simplified way to differentiate kenetic energy - horsepower vs momentum/inertia - torque

 

A Cleveland isn't even a suitable boat-anchor (same as the rest of the 335-series junk) let alone an engine remotely capable of 350 HP in near-stock form.

 

Hey whoa hold on! I never said it was stock, and I happen to think they are amazing engines, as do a lot of ford guys. However the 351M and 400 were doggish, the cleveland was a pretty hot motor. Don't make assumptions and insult me without a clue what I have...

 

All the science aside, here's what counts to me: driving the gas rig over a mountain will be marked by high RPMs and lousy MPG. The fuel will be easier to find and, these days, cheaper. The diesel rig will have a more relaxed RPM with better MPGs, but the fuel will be harder to find and cost more. Overall fuel cost used to skew heavily in favor of diesel due to better MPGs, but I think a lot of that margin has evaporated as diesel cost has risen. I'd choose diesel again mostly since I dislike revving the snot out of a tow machine.

 

Thanks for the post that is what I wanted to know, no gearing is going to remotely make up for that kind of difference and the motor dyno tells you that but people do not understand what it is telling them.

People do not realize when they think their 400 HP geared correctly to pull Gasser is going to pull like a 400 HP Semi engine they do not realize it is like you pulling up at the light in your Mustang Street car and the guy in the other lane has a Pro Stock car and you are going to get smoked bad no matter how you slice the gearing.

 

I had a 460 gasser 1-ton van ("Tugly"), and forget about that 10 MPG pulling or empty. I'd get 10MPG while hypermileing at 55 MPH, and 4 MPG pulling the Vantage grade with a 8000 lb. boat/trailer in tow (and family inside) in second gear with the RPMs cranked up and the temp gauge poking me in the left eye.

My 444 diesel ("Stinky"), with the same combined vehicle weight (lighter boat, heavier truck) on the same run (same temperatures - it's boating season) would average 12-14 MPG... without the need to slow down or have the engine temperature issues.

I wanted to offer up near-equal-sized gasser with identical total load and same route/weather.

By my rudimentary calculations, the old fuel price differential made the diesel very attractive. The new price differential makes diesel a choice with no financial gain at all - if not a loss... unless you tow heavy a lot.

One might say "But Tugly, my math says the economy equalizes the cost." That doesn't compensate for 4 gallons of synthetic oil at 5000 miles or dead dinos at 3000 miles, plus all the other expensive maintenance items.

In my personal experience, it comes down to preference - not dollars. That being said - just try to beef up a stock gasser. In that department, Stinky kicked Tugly (or just about any other gasser) to the curb.

 

The diesels are way more efficient if designed to be but the new ones are designed to pick your pocket from stupid regulations. They want us walking and living in tents with no RV's to tow.

 

If both motors are running exactly 300hp at the exact same time, then they will pull up a hill at the exact same rate.

Because of torque differences, both motors will do it at different RPM's.

 

Right but the problem with the spinner gas motor is it can get in a pinch much much more easily loaded to where it will not be able to spin up to make the HP.

The Diesel is a beautiful work horse, a 600 HP rig is a Pro Mod engine with a governor that turns on at 90MPH when loaded with the Aero package of a semi and will do it for a million miles.

Diesels are BAD Mo FO's all things considered for working. It's a shame the new ones are to complex.

 

And now you're changing the parameters.

You need to understand that "X" horsepower means just that. Doesn't matter if it's gas or diesel, if both are at "X" horsepower at the same time, they are both doing the exact same work. One will not out-pull the other.

What you are talking about now is changing RPM's and taking one out of the peak power band and comparing it to another that is still in it's peak power band. Now one is running "X" horsepower, and the other is running "Y" horsepower. It's no longer the same comparison because you changed the RPM's, and at this point one will absolutely out-pull the other.

So change the gearing of the gas motor to keep the RPM's in a narrow range like the diesel, at the peak power band. Suddenly it's going to respond just like a diesel as you slow down and speed up.

But why doesn't this happen? Why aren't they built that way? It's because now you're going to use far more gas to stay at it's peak power output because the RPM's are now 3 times what it is for a diesel to do the exact same work. Yes, gearing does make a huge difference. Heck you can build a large gas engine and put it in a semi and it will pull a load up a mountain like it's diesel counter-part if it's geared correctly. But the difference won't be how fast or slow it does it. The difference will be how much fuel is consumed.

 

That's good that you understand. There are many other folks that don't and constantly argue horsepower vs torque thinking they are identical.

 

Go in your garage get a bicycle put a 1.5 HP 40cc weed whacker motor in it and make it work and pull you and guess what no problem. Do the same thing with a Small 1.5 HP RC model engine and you will have a big problem no matter how you gear it. It will not work for practical use.

The only reason a BB stock engine Gas can kinda a little compete with a PS in pulling is because it makes it's HP for the most part below the 5225 RPM mark.

The RPM torque curve does not matter to much as long as you gear to stay in max torque output of the engine.

Go put a 500 ci 600 HP gas engine in a 80,000 pound rig and good luck getting it to build HP. EXACT SAME thing as bicycle

It all depends on what you are doing and the engineers know that's why big rigs do not have a gas option.