Just stumbled across and interesting article that folks might be interested in seeing.Torque vs. HP

Here's the bottom line: horsepower = rpm x torque / 5252. Essentially, if you have low torque, you'll need to increase your RPMs to get higher horsepower. Think of a Formula 1 car with low torque revving up to 15,000 RPMs. Some have gone to 20,000 RPMs.I think Diesel folks like having more torque because the engine doesn't have to turn as fast to produce the same horsepower. Less RPMs equals less heat, noise, and friction. But the easiest way to increase horsepower is to increase RPMs.But the only time you are near your maximum horsepower is when you are close to redline. Usually during acceleration or climbing up a mountain.

holstein13 wrote:Here's the bottom line: horsepower = rpm x torque / 5252. Essentially, if you have low torque, you'll need to increase your RPMs to get higher horsepower. Think of a Formula 1 car with low torque revving up to 15,000 RPMs. Some have gone to 20,000 RPMs.I think Diesel folks like having more torque because the engine doesn't have to turn as fast to produce the same horsepower. Less RPMs equals less heat, noise, and friction. But the easiest way to increase horsepower is to increase RPMs.But the only time you are near your maximum horsepower is when you are close to redline. Usually during acceleration or climbing up a mountain.Very well said

Torque (at the wheel): Determines if you can get up the hill.HP: Determines how fast you get up the hill.Key point: Torque measured at the wheel. A gas engine with half the torque running twice the RPM thru a lower gear will go just as fast as the diesel. The question is does the gas powered truck have the gearing to do that.

Where gobs of torque seem to make a big difference is when starting from a standing stop on a steep grade. A big diesel has peak torque around 1300 rpm and peak HP at 2100. A gasser may be closer to 3000 for peak torque and 5000 for max HP.

Torque vs. HP | Good Sam Community

15 Replies

noteven
Explorer III
Jun 07, 2015
7ofus wrote:
10forty2 wrote:
Torque - What you feel in the seat of your pants when you push down on the pedal from a dead stop.

Horsepower - Something that gearheads measure to make themselves feel better...... ;-)

So according to this logic, drag racers should all convert over to diesel engines if they want an advantage:)

You don't think a big block gas/alchohol/nitro drag engine has much torque?
Cloud_Dancer
Explorer II
Jun 07, 2015
I care about the torque and HP curves in the turbo'd 8.3 Cummins diesel engine that's in the back of my motorhome. When I ordered it, I made sure that these curves were matched to the gear ratios, rolling tire radius, and weight. If only the roof design had been this good.
DSDP_Don
Explorer
Jun 07, 2015
Okay....It's been a month or two since the Torque/HP discussion has occurred. :)

I predict 10, no, make that 11 pages before it slows down! :Z
RCMAN46
Explorer
Jun 07, 2015
427435 wrote:
JetAonly wrote:

The essence of the difference between Gas and Diesel experience is this. The HP and torque curves of the gas engine are shaped the same, they just peak at different RPM's. The diesel has a torque peak early then falls off slowly with rpm, while the HP curve is more peaked at the upper limit of rpm. Since HP is a RPM based measure, as rpm drops HP falls. In a gas engine it may have to fall 1500 rpm to see the torque rise. In a diesel the torque rise is immediate. So, measured HP falls at slower rate in the diesel vs gas.

YMMV

Actually, the curves are not similarly shaped with today's turbo, intercooled, and computer controlled diesels. Their torque curves are flatter and longer. Also, the diesel's hp curve will often grow as the rpm's are lowered.

You need to take a look at the HO 6.7 Cummins. The tongue curve is no longer flat as with the older 5.9.

The Ford Ecoboost gas engine has a flatter torque curve than the HO 6.7 Cummins.
holstein13
Explorer II
Jun 07, 2015
Let's try another analogy. Imagine a stopped bicycle with the pedals horizontal to the ground. Now imagine putting the brakes on and standing on the pedal in an attempt to move the bike forward. The amount of force you apply on the pedal is called torque. The heavier you are, the more torque you can apply on that pedal.

Now for those of you who think torque gets you up the mountain. I'd like to challenge you to get a 250 pound athlete with more torque to compete against a 150 pound athlete with less torque on a similar bike. The lighter athlete will have two advantages, 1) they are lighter and will require less work to get up the mountain and 2) they can turn the pedals faster than the heavier athlete because their legs also weigh less.
7ofus
Explorer
Jun 07, 2015
10forty2 wrote:
Torque - What you feel in the seat of your pants when you push down on the pedal from a dead stop.

Horsepower - Something that gearheads measure to make themselves feel better...... ;-)

So according to this logic, drag racers should all convert over to diesel engines if they want an advantage:)
427435
Explorer
Jun 07, 2015
JetAonly wrote:

The essence of the difference between Gas and Diesel experience is this. The HP and torque curves of the gas engine are shaped the same, they just peak at different RPM's. The diesel has a torque peak early then falls off slowly with rpm, while the HP curve is more peaked at the upper limit of rpm. Since HP is a RPM based measure, as rpm drops HP falls. In a gas engine it may have to fall 1500 rpm to see the torque rise. In a diesel the torque rise is immediate. So, measured HP falls at slower rate in the diesel vs gas.

YMMV

Actually, the curves are not similarly shaped with today's turbo, intercooled, and computer controlled diesels. Their torque curves are flatter and longer. Also, the diesel's hp curve will often grow as the rpm's are lowered.
rgatijnet1
Explorer III
Jun 07, 2015
Getting up the hill faster also has a lot to do with the gear ratio of your differential and transmission.
You can have high HP and gobs of torque, but if the coach is not geared right, you will still be heading up the hill in the right lane. Your engine won't be straining, but you are still going slower than if things were set up right, like most over the road rigs are set up that travel the mountains on a regular basis.
10forty2
Explorer
Jun 07, 2015
Torque - What you feel in the seat of your pants when you push down on the pedal from a dead stop.

Horsepower - Something that gearheads measure to make themselves feel better...... ;-)
JetAonly
Explorer
Jun 07, 2015
Since a diesel has higher compression, it must also have a longer strike to make that happen. Longer stroke engines make higher revs hard on the moving parts, specifically the crank shaft. The physics of all this is pretty straight forward. HP is a time rate measure, torque is a force. Torque is a force. Force over distance is work. Work over time is Power, as in Horse power.

The essence of the difference between Gas and Diesel experience is this. The HP and torque curves of the gas engine are shaped the same, they just peak at different RPM's. The diesel has a torque peak early then falls off slowly with rpm, while the HP curve is more peaked at the upper limit of rpm. Since HP is a RPM based measure, as rpm drops HP falls. In a gas engine it may have to fall 1500 rpm to see the torque rise. In a diesel the torque rise is immediate. So, measured HP falls at slower rate in the diesel vs gas.

YMMV