large truck diesels are not rated in torque, they are rated in HP.
trucks today mostly come with 450 to 600 hp engines and 10 speed trans for flat lands, and up to 18 speed trans for hilly country.
my 79 had a 237 and a 5 speed. it was slower than molasses flowing uphill in winter.
my 2001 had a 400 with an 8 speed. much better because the extra 3 gears kept the engine in the power band...sorta.
the 05 mack has a 427 and a 9 speed. much better runner.
the 05 T-800 kenworth has a 470 Cat with a 9 speed.
the 07 W900 kenworth has a 600 hp Cat with an 18 speed. it will pull 80,000 lbs uphill outrunning most cars.
all the trucks are geared the same and have a top speed of 74 mph.
except for the W900. we have no idea how fast it will go. but one of the guys did have it up to 95 before he chickened out.
the hot ticket these days is an automatic trans with around a 400 HP engine for the flats, or a 500 HP engine for the hilly terrain. .

 

Thanks for the reply, in a truck when they have more HP they really just have more Torque because they do not turn any more RPM to make like the 600 HP the bad a$$ rig had.

No way no matter what your gearing a big block 600 HP Gas engine would never pull 80,000 pounds up a hill at a good clip? that is what all that torque allows you to do.

If you put each one of those truck motors on a dyno you would see all the extra HP being made came from more torque and no extra RPM being turned so you kinda made the point that torque determines how much weight you can pull under heavy load with out bogging down..

 

HP=(RPM x Torque)/5252

Diesel 600HP example - 12000 ft-lbs @ 2626RPM to a 1:1 transmission = 12000 ft-lbs driveline torque @ 2626RPM
Gas 600HP example - 600ft ft-lbs @ 5252RPM to a 2:1 transmission = 12000 ft-lbs driveline torque @ 2626RPM

 

What I am saying is you will never be able to get it their and keep the engine in the upper 5200 RPM range to make the 600HP required pulling a 80000 pound load up hill. What is on paper and what the reality is I think may be different. It's much easier to maintain 600 HP at the lower rpm on a diesel than the gas at the higher RPM. I am talking under heavy load it becomes obvious which motor maintains the HP with less effort.

Just like I was saying, try and run a moped with a model RC engine and see what happens ????? it does not have the torque required to spin up to the RPM to make the 1.5 HP with a 400 pound load on it.

If you put a 600 HP gas engine in a rig and tried to pull 80 grand up a good grade the 600 HP diesel engine would stomp it bad. I could be wrong but do not think so.

I know all about the formula.

What people do not take into consideration is torque earlier allows you to spin up to make the HP rating easier under a load. The shorter the RPM range to spin up under a load the easier the HP will be to make and maintain and not fall off the pipe.

Mario Andretti said it best when he said a high torque engine will reach terminal velocity faster than a Rever no matter what the gearing. He was basically saying a high torque engine will pull the max HP # much quicker under load.

I will research more and I could be wrong but just try and get a model RC engine to run a moped.

The model airplane engine could do it if there was a way to like build a 40 or 50 speed gear box to go with it so it would be reving at 40 grand all the time so it was always applying 1.5 HP to accelerate the load up to speed but in no way could it accelerate like the 50cc moped engine with just the centrifical clutch or pull the load nearly as efficiently.

 

Brute, out.

 

I am going to research this because I am interested because I was always curious about this myself. I am not saying I am right in no way. I read what you said about the F800 so you would know.

 

I had two different diesel pickups. Both were in the warranty shop as much as I got to drive them. Yesterday, I bought a 2014 F-350 DRW, crewcab, 4-wheel drive gasser for $32,000. The Ford dealership was hugely discounting this truck. I refuse to go back to a diesel pickup and the general public does not realize gas trucks are more reliable so I got a GREAT deal!

 

Nothing wrong with that, diesel is so pricey now, if aren't towing all the time, gas is likely the way to go.
The modern gas engines are getting pretty darn good now days, compared to the older generation.

 

You made the right choice, every mechanic I have talked to said the new diesels were crap. They did not come right out and say that but you had to read between the lines and the interesting thing was most of them said my old mechanical was the one to have and it was bullet proof because how easy it was to fix.

I also had the ones who do fleet service say the big companies who they serviced were going back to gas because the new ones were just to expensive to service and that is really why they said my IDI was best. You can build a IDI to make power and still be cheap to fix.

A diesel for pulling overall is still much better for pulling because it makes it's power through brute force torque rather than RMP. Take the Maxidyne 238 Mack I was talking about, it could probably pull 40 or 50000 pounds with a 5 speed and accelerate to 67 MPH with no problem with that load because it makes 1100 foot pounds of torque to assist to make the HP MPH under such a load. You would never get a 238 HP gas engine that turns a lot of RPM to pull 50000 pounds efficiently with a 5 speed to 67 MPH because it does not have the torque to be able to spin up under such a load to make the HP necessary to maintain the MPH.

HP is not HP and the motor that makes 238HP at 2500 RPM is going to be way more powerful than the one that does it at 10 grand but look at the motors weight compared to a 238 HP motorcycle engine. So for building a race machine a 3000 pound Diesel engine need not apply. If you put a 238 HP diesel engine in a light frame with just a seat you could put it in the Maxidyne 5th gear and start right off from a dead stop and smoke the tires with no shifting up to terminal velocity because all the torque in such a light package it would have no problem making the HP MPH but it would not handle near as good as the light weight 238HP motorcycle engine in a light frame so for a race track app the 238 HP Gasser would kill it.

It's all application dependent, just look what performance #'s a model RC airplane can do with it's 1.5 HP.

So I guess basically HP is MPH and torque is roll on acceleration to make the HP to run the MPH ?

Just babbling


I would love to go down and get a new truck but just cannot bring myself to do it, they are begging me to come down and get one.

 

Depend on which two motors you compare. Diesel is more expensive to maintain but will live twice to three times the life. Pulling torque and overall engine effectiveness including fuel mileage is going to be better with a diesel.

 

The conclusion I have come up with is the new diesels are being designed to pick your pocket and that is the problem. The new diesels could be way better than they were but we are not seeing that in is some regards..

Their is no reason the injectors and parts should cost so much, I opened this thread not looking for a argument but to learn about HP and how to understand HP and be able to read a dyno and understand it.

Both Brute Ford and TJC filled in the blanks so I now understand this gig. It can be read on a dyno spec sheet from a engine pull you just need to understand what it's telling you.

I never could understand why a 400 HP RIG could pull 80 grand up a hill and shift and accelerate while doing it and a 400 HP Gas car motor rated the same power cannot and the reason is simple the Diesel is way more powerful and the dyno tells you that but you have to understand what it's telling you.

TJC made the point a 600 HP diesel can accelerate a 80000 pound load up a hill but in no way could a 600 HP Nascar engine do that no matter what the gearing. I was not aware a 600 HP diesel was that powerful, that takes Brute Torque power to do that period!

He made the point they rate the Rigs in HP and not torque and the reason being is because your average Joe would not be able to read a DYNO chart spec sheet of a new Rig and understand what it was saying. So they just rate it in HP to make it easy. The Dyno torque curve tells the story and not the HP rating!

So a Big Block gas engine can kinda compete with a smaller diesel pulling as long as MAX hp is below the 5250 RPM mark because it makes relatively similar torque #'s to a small pickup diesel. But a big RIG motor that makes 1800 Ft of torque and 500 HP compared to a 500 HP 500 cubic inch gas motor is just way more powerful being able to spin up RPM and make the HP rating under a heavy load not matter what the Gearing for the gas engine.

I am just clearing this in my head because I finally understand what a dyno is telling you. This is after about 20 years of thinking about it off and on so that is why I am Realslowww.

Thanks for chiming in, it pisses me off they are messing up the new diesels in a lot of ways. To many mechanics I talk to shake their heads when I ask them about the complexity and expense of the new diesel truck engines. As stated I believe they are designed to pick your pocket intentionally.

 

the biggest reason for the complexity and expense of the new diesel truck engines is the EPA.
if you got rid of all the idiotic EPA rules, the newer engines would not need all the expensive parts, and get much better fuel mileage.

i know of a 2014 F-350 6.7 diesel with DEF, DPF, muffler, and cat delete.
it then had a tuner installed to keep the computer from setting trouble codes.
fuel mileage increased 5 MPG, and it does not smoke AT ALL.

 

Thanks for the info, I think the EPA is making it overly difficult on purpose, if you are not aware our industry is being destroyed on purpose.

Will a 600 HP semi really accelerate up a hill weighing 80 grand and you can shift and it will motor out?

I have never driven a Semi and I did not realize the big motored ones were that powerful. I never could truly understand HP and when you said that I finally understand HP now.

HP = MPH and Torque = ability to accelerate a load up to that MPH. The more torque the better the ability to accelerate the load to max HP MPH.

Thank you!!!!!!!


Which means a Pro Mod car really only needs 6 or 700 HP to go 250MPH in a 1/4 mile but it is 3 or 4 thousand HP because it needs the 2000 FT pounds of torque that comes with a 3 or 4 thousand HP light weight race motor so it can go 250 in sub 6 seconds. All the extra HP is wasted but you have to build the engine like that to get the torque you are after for that acceleration.

A Pro Mod car could run a rig correctly with pulling power like the 600HP diesel engine for about 2 minutes then you would hit the exit ramp and do a Don Garlits rebuild.

It makes me realize how awesome those big rigs are! they will pull like a Pro Mod car for a million miles, they are bad a$$.

The guys who think you can get a spinner to pull like a torque motor with gearing do not understand how to read a dyno or what it means. HP is not HP.

I could be wrong.

 

with the proper gearing in the rears and proper transmission. the mack with the 237 and 5 speed pulling 60k is a slug, because the gear ratios in the trans are way to wide.
put a quad box behind that engine and it will pull anything you want anywhere you want. it will just be as slow as a snail going uphill in molasses in winter.

now take a truck with a 600 HP engine and an 18 speed eaton/fuller trans, and it will pull 80K all day long at highway speed up or down hill, as long as you are in the proper gear.

 

This is repeated often.

Maybe if comparing a 7.3 vs 460 back in the 90s.

6.0 vs 5.4/6.8
Or
6.4 vs 5.4/6.8???

no mods and scheduled maintnance followed, th 6.0 or 6.4 lasting 2-3 times as long would be a bad bet.