What if Torque @ RPMs in engine specs was replaced with something else?

[dudejo]

I'm asking that because sometimes, in performance debates, there always seems to be someone who can't quite grasp why torque is important for work-related tasks. Like in a Ford 300 I6 vs Ford 302 V8 comparison.

Also, people in general tend to lack mechanical understanding to understand what's common knowledge to more mechanically inclined drivers. They generally stick to the peak HP of a car without looking at RPMs or Torque.

So my idea is to replace Torque @ RPM with something different that would make it easier to compare performance for work-related tasks. It would be 50 HP @ X RPM.

The earlier an engine generates 50 HP, the stronger it is for working.

For example, Viper 8.0l engine vs Caterpillar C15 engine. While both have a peak output of over 400 HP, the C15 will generate 50 HP a *lot* earlier than the Viper engine will. To be more precise, the RPMs at which the Viper 8.0l is generating 50 HP is the roughly same RPMs at which the C15 is generating its PEAK HP.

 

[PAPPACLART]

ALong with dyno curves, I would love to see thrust curves, it would never happen though!!


Thrust curves are best representation of what is happening at the wheels. Tho you could not use a blanket figure.

Thrust curves take into consideration your gear ratios and then show you how much thrust measured in either lbs or KG's in any gear at any road speed/rpm point.

People forget, power is just rpm and torque multiplied by rpm.

UK Motorcycle magazines have often used thrust curves to show the actual performance at the wheels of an engine.



Thrust curve of 600cc inline 4 road bike with approx 100bhp and 45 ft/lb. 1st gear to 6th gear, with 1st gear obviously having the most thrust. The torque curve will follow the exact same contours of each thrust curve.

Thrust curve of a early 1000cc Yamaha R1 that shows what effect lower gearing has on thrust and acceleration from a dig.

 

[dudejo]

Looks pretty nice.

While my idea isn't quite as detailed, I wanted to go for simplicity. Basically, they're two sets of numbers you can compare at a glance and have a rough idea of the engine's capabilities. And it works.

As for gearing, posting the top speed of each gear, along with a short explanation of "slow gear = high power", should be intuitive enough for most people.

Like I said, I'm trying to go for simplicity so that even someone who isn't well versed in mechanical terms will understand the difference between a 200 HP Diesel and a 200 HP Honda Civic.

 

[Bopop4]

Also, people in general tend to lack mechanical understanding to understand what's common knowledge to more mechanically inclined drivers. They generally stick to the peak HP of a car without looking at RPMs or Torque.

People? Knowing about engines?


All you have to do is tell/show them a power curve, but people generally don't care enough to grasp the basics of engines.

 

[LMSCorvetteGT2]

People? Knowing about engines?


All you have to do is tell/show them a power curve, but people generally don't care enough to grasp the basics of engines.

Exactly as seen a lot on the forum, there are too many that just care about the raw power and 0-60 mph times. If those are good then the car to them is obviously superior. They don't factor in torque and how it works overall for the car in certain scenarios while racing in GT or any racing game for that matter. Wish they did.

 

[Vegard]

The problem is, appreciating it requires a basic understanding of analytical dynamics, no matter how much you "dumb it down". In all likelihood your efforts will be in vein.

Just focus on expanding your own understanding is my advice.

 

[Vegard]

edit - double post.

 

[MrWednesday]

I'm asking that because sometimes, in performance debates, there always seems to be someone who can't quite grasp why torque is important for work-related tasks. Like in a Ford 300 I6 vs Ford 302 V8 comparison.

Also, people in general tend to lack mechanical understanding to understand what's common knowledge to more mechanically inclined drivers. They generally stick to the peak HP of a car without looking at RPMs or Torque.

So my idea is to replace Torque @ RPM with something different that would make it easier to compare performance for work-related tasks. It would be 50 HP @ X RPM.

The earlier an engine generates 50 HP, the stronger it is for working.

For example, Viper 8.0l engine vs Caterpillar C15 engine. While both have a peak output of over 400 HP, the C15 will generate 50 HP a *lot* earlier than the Viper engine will. To be more precise, the RPMs at which the Viper 8.0l is generating 50 HP is the roughly same RPMs at which the C15 is generating its PEAK HP.

That's all well and good for working trucks, but it's largely useless in any other application. And in point of fact, most of the time, peak HP (or, more strictly speaking, HP over the useful RPM range imposed by gearing) really is what's important for a car.

 

[Wolfe]

That's all well and good for working trucks, but it's largely useless in any other application.

I think that's all @dudejo is getting at, though. In a work/truck type of application, peak HP is commonly cited as it is with passenger cars, when peak HP has relatively little to do with utilitarian tasks and driving, compared to going fast in a car.

That said, I'm not sure 50hp @ X RPM is much more descriptive than peak torque @ X RPM. The latter at least describes the maximum twist an engine can generate while also implying what sort of rev range is available. A small modern turbocharged 4-cylinder that peaks at 146lb.ft in a band from 1800-4000RPM would generate 50hp @ 1800RPM while a larger naturally-aspirated engine could generate more peak torque later while still hitting 50hp @ 1800RPM -- if dudejo is correct about the Viper's torque curve, it wouldn't even generate 50hp until 2100RPM (per the Caterpillar's peak HP figure).

 

[dudejo]

I think that's all @dudejo is getting at, though. In a work/truck type of application, peak HP is commonly cited as it is with passenger cars, when peak HP has relatively little to do with utilitarian tasks and driving, compared to going fast in a car.

That said, I'm not sure 50hp @ X RPM is much more descriptive than peak torque @ X RPM. The latter at least describes the maximum twist an engine can generate while also implying what sort of rev range is available. A small modern turbocharged 4-cylinder that peaks at 146lb.ft in a band from 1800-4000RPM would generate 50hp @ 1800RPM while a larger naturally-aspirated engine could generate more peak torque later while still hitting 50hp @ 1800RPM -- if dudejo is correct about the Viper's torque curve, it wouldn't even generate 50hp until 2100RPM (per the Caterpillar's peak HP figure).

The problem with using foot/pound @ RPM is that you're getting an unfinished puzzle. Also, just because it hits peak torque at some RPM level, doesn't mean that the torque around that peak is useless.

That's why I want to interpret it as a horsepower figure. Horsepower is what the puzzle looks like after it's completed.

Also, I chose 50 hp @ X RPM because it sets a minimum threshold where the engine makes notable power. The earlier you get 50 hp, the more torque you have on hand. If it comes with a high peak hp, then you have one beast of an engine.

Heck, it's technically impossible to calculate the Bugatti Veyron's threshold of 50 HP because it makes 100 HP at *idle*.

 

[TouringBubble]

The issue I see is that HP is a calculation based on tq. So, you'd actually be adding another value to the equation. But, HP is actually a measure of work, so I see where you're going with this ...

I think people just need to understand torque.

 

[dudejo]

The issue I see is that HP is a calculation based on tq. So, you'd actually be adding another value to the equation. But, HP is actually a measure of work, so I see where you're going with this ...

I think people just need to understand torque.

My idea would replace Torque @ RPM. Having both would be redundant. As for understanding torque, I believe that my replacement spec would help in that regard.

After all, the only way to get more HP at low RPMs is to have more torque.

 

[TouringBubble]

My idea would replace Torque @ RPM. Having both would be redundant. As for understanding torque, I believe that my replacement spec would help in that regard.

After all, the only way to get more HP at low RPMs is to have more torque.

You're missing my point. Horsepower numbers are calculated from measured torque.

So, your solution requires that you measure torque, calculate horsepower and then ignore the torque value.

 

[dudejo]

I know how HP is calculated.

The issue is that you're telling me my method has a problem but I don't see a clear reason why.

The spec sample I have in mind would look like this :
Example 1 (Cummins 6BT)
Peak HP : 215 HP @ 2500 RPM
Baseline : 50 HP @ 1050 RPM

Example 2 (Honda 1.8 VTEC)
Peak HP : 200 HP @ 8000 RPM
Baseline : 50 HP @ 2300 RPM

 

[TouringBubble]

I just dont understand using a horsepower value to replace torque when horsepower is derived from torque in the first place.

Again, people just need to understand torque.

I see what you're tying to do, but here is my take. If car ads are quoting HP figures only, this doesn't help. If people researching only look at peak HP, this won't help. If people are researching and looking at TQ values, they likely understand it and this isn't needed.

Your logic is sound, and your approach is fine if someone chooses to only reference HP. I simply think you're trying to solve a problem that doesn't exist.

There is already a perfectly fine way to define torque/work of an engine. People just choose to ignore it. This won't change that. An ad for a truck could simply state "makes 340 ft/lb of torque" and accomplish what you seek with no changes to common terminology.

 

[dudejo]

I want to use horsepower because torque, by itself, means nothing. If that 340 ft/lb of torque is generated at 1000, 4000 or even 10,000 RPM, you have three drastically different engines.

And, like I said, the only way an engine can generate 50 HP at lower RPMs than other engines is to have more Torque. In one of my previous posts, I was saying how the Bugatti Veyron has so much torque that it generates 100 HP at its ~1000 RPM idle.

When a Honda Fit is making 100 HP, the driver has the throttle to the floor.

That's how my theoretical spec helps. You only need to explain how Torque and RPMs combine to create horsepower and, using a baseline (my 50 HP), you can directly compare engines characteristics, like I just did with the Bugatti Veyron and the Honda Fit.

 

[TouringBubble]

I'm with you on tq peaks alone mean nothing ... Just like HP alone means nothing. The curve is what matters. But your method still leaves out important info.

Its technically possible to have an engine make 50 HP at an earlier RPM but have less overall tq.

As an example ... An Evo makes 50 HP around 2500 rpm while a V6 camaro makes 50 HP around 1500 RPM. The Camaro makes power earlier but only reaches 250 ft/lb of total tq where the Evo generates 370 ft/lb.

Which is better? It depends on the task. But I dont think you can make a logical choice based on only one piece of that info. That's why there are curves.

 

[dudejo]

What's the peak HP for either? At what RPM is that peak?

And which models? Evo V? VI? VII? X?

And is the Camaro's V6 from 1997? 2001? 2010?

 

[TouringBubble]

It doesn't matter. That was a stock Camaro from a random dyno I found and a modified Evo.

Again, I see your point, and I like the idea ... but it's still an incomplete puzzle. Why 50 hp? What if the work you need done requires 200 hp ... is the 50 hp value still relevant? Why isn't the base 100 hp or 200 hp @ X RPM? It's a great way for people to look at graphs and gain some understanding from them, but it's not a complete solution.

 

[dudejo]

Don't forget those are merely engine specs.

If you need 200 HP to get your loaded truck moving, that generally means you shift your transmission into first gear. The multiplied power will give you your 200 HP.

In the Cummins 6BT example I showed earlier, it makes 50 HP at ~1050 RPM. The idle RPM is only a couple hundred below that. What does this mean? Your loaded truck, in first gear, will accelerate with only minimal throttle input (if any at all).

It's a similar deal with the Camaro V6 vs the modified EVO. The Camaro making 50 HP earlier than the EVO means it will get moving more easily. It won't go as fast as the EVO, since it has less peak output, but it'll be better for day-to-day driving.

And, I choose 50 HP because it's a good threshold value. It's weak enough to be under the peak torque's HP value but high enough so the output actually matters.

 

[Bopop4]

And, I choose 50 HP because it's a good threshold value. It's weak enough to be under the peak torque's HP value but high enough so the output actually matters.

But what matters for a Kei car isn't going to matter for a dually towing a 5th wheel trailer.

 

[dudejo]

But what matters for a Kei car isn't going to matter for a dually towing a 5th wheel trailer.

Technically, it would.
Since the engine output of a Kei car is heavily restricted by law, you pretty much need low-RPM power. Especially since none of them will ever see a highway.

 

[dudejo]

Barring that, another idea could be to display HP @ idle RPM.

 

[niky]

It's nigglingly difficult to get a measure of HP at idle... difficult to get constant load, and with electronically controlled idle, most cars have a throttle plate that responds to changes in the idle, opening up a little more if the car is in danger of stalling.

The lowest I'd say you could get decent readings would be around 1,500 rpm.

-

Very hard to reduce such a complex thing into a simple set of numbers. If you understand torque and horsepower, you can understand roughly how an engine behaves given peak torque and peak power and the rpm they occur at. People who don't understand will be even more confused by other numbers.

Engine power is most easily described visually, as a torque curve or horsepower curve. If you have to reduce that to one number, you could do average horsepower over a given range... something like 3-4,000 rpm worth for gasoline and 2,000 rpm worth for diesels.

 

[Aquarelle]

HP is the simplest thing to understand, I would imagine anyone who needs a vehicle for a specific task (Hauling heavy loads for instance) Will know enough about that sort of thing or would at least explain to the dealer what they're after in a vehicle and the dealer would point them in the right direction and explain why X car is a better choice than Y.

The thing is, to the general pop things like torque curves are incredibly dull and boring - Horsepower is something everyone tends to understand and if they need more information there's often an expert on hand (At least if you're using a good dealership)

I would like to see torque/power curves on those little window displays though.

 

[Eunos_Cosmo]

For most things, POWER is what matters. Any engine can accomplish any task (with a proper gear reduction, a Briggs and Stratton lawn mower engine could move a space shuttle) , but HP tells you how quickly it can accomplish this task.

 

[dudejo]

It's nigglingly difficult to get a measure of HP at idle... difficult to get constant load, and with electronically controlled idle, most cars have a throttle plate that responds to changes in the idle, opening up a little more if the car is in danger of stalling.

The lowest I'd say you could get decent readings would be around 1,500 rpm.

-

Very hard to reduce such a complex thing into a simple set of numbers. If you understand torque and horsepower, you can understand roughly how an engine behaves given peak torque and peak power and the rpm they occur at. People who don't understand will be even more confused by other numbers.

Engine power is most easily described visually, as a torque curve or horsepower curve. If you have to reduce that to one number, you could do average horsepower over a given range... something like 3-4,000 rpm worth for gasoline and 2,000 rpm worth for diesels.

Peak HP would still exist. The secondary power specification, if I had it my way, would either be 50 HP @ X RPM or HP @ idle RPM. The latter of which you just shot down.

My main issue with the current stat of peak torque @ X RPM is that the torque around that peak is not necessarily useless. For example, the peak torque of an older Honda 1.6l engine is only ~25% higher than its lowest torque output at reasonable RPMs.

 

[Eunos_Cosmo]

The answer is that power figures effectively explain torque across the entire rev range, which is why you can instantly compare engines by their power output, unlike their torque output. The thing that you are looking for does exist, it's called power! In classical physics power is how much work can be done in a certain amount of time. Work/Time. Torque is work. Therefore torque/time = power! Torque figures are given mainly to establish what type of powerband the engine has, which tells you essentially what it's suited for. While two engines of the same power output can do the exact same task at the same speed, there are other factors to consider. While a 200hp 1.6 liter Honda vtec engine with 130lbs*ft of torque might exactly match the abilities of a 200hp 7.3 liter diesel V8 with 400lbs*ft of torque (and with properly set gearing, it would exactly) the Honda engine will be screaming its head off and wear out prematurely while the big 7.3 will be turning probably 2,000rpm placing minimal wear on components.

Theoretically speaking, rated engine torque is completely meaningless, but it does matter in practice.

 

[dudejo]

The answer is that power figures effectively explain torque across the entire rev range, which is why you can instantly compare engines by their power output, unlike their torque output. The thing that you are looking for does exist, it's called power! In classical physics power is how much work can be done in a certain amount of time. Work/Time. Torque is work. Therefore torque/time = power! Torque figures are given mainly to establish what type of powerband the engine has, which tells you essentially what it's suited for. While two engines of the same power output can do the exact same task at the same speed, there are other factors to consider. While a 200hp 1.6 liter Honda vtec engine with 130lbs*ft of torque might exactly match the abilities of a 200hp 7.3 liter diesel V8 with 400lbs*ft of torque (and with properly set gearing, it would exactly) the Honda engine will be screaming its head off and wear out prematurely while the big 7.3 will be turning probably 2,000rpm placing minimal wear on components.

Theoretically speaking, rated engine torque is completely meaningless, but it does matter in practice.

What does any of that have to do with what I've posted? I know how HP is calculated and how gearing works.

The entire point of this topic is to talk about potentially replacing the secondary specification of Torque @ X RPM with 50 HP @ X RPM. Doing this would show how above-average torque influences HP output when not at full throttle. An engine that makes 50 HP at below-average RPMs obviously has more torque.

Also, it would solve the problem of peak torque @ RPM not showing the 25%-75% differences in torque below the peak, depending on engine. It would also provide a clear baseline, something peak torque @ RPM doesn't do.

 

[Zenith]

The entire point of publishing any of these numbers is to minimize the amount of extrapolation necessary to understand how the engine will behave and what performance the car is capable of. You may technically be able to calculate everything you need from other numbers or without the torque rating, but it's unnecessary and annoying.

Engine torque is also important for chassis engineering and safety, especially on live axle cars.