Its a hard thing for people to get

"HammerheadFistpunch" (hammerheadfistpunch) 11/19/2015 at 16:53 • Filed to: None

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And I understand, as I didn’t fully understand it until recently that torque is only a component part in HP and that HP is the thing that matters.

Whats amazing is how many car people still don’t understand the relationship between !!!error: Indecipherable SUB-paragraph formatting!!! .

The comments on the CX-9 story prove that there are still a LOT of car people in this world that still believe (as I did) that torque matters outside of the relationship it has to RPMS.

I’m not a engineer or some super smart person and never claimed to be...but it boils down to some pretty basic physics when you really stop to think about it.

Textured Soy Protein > HammerheadFistpunch 11/19/2015 at 17:00

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I think the common misconception is that torque = low-rpm power and hp = high-rpm power.

So like, the comments about the CX-9 mostly boil down to “the small turbo spools up at low RPM so when the mom-mobile CX-9 is driven at typical mom-mobile low RPMs, it will feel powerful.”

HammerheadFistpunch > Textured Soy Protein 11/19/2015 at 17:03

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Yeah, that about sums it up, because of the history of “low end torque” as being a desirable thing, people have somehow transmuted the meaning of torque to literally mean “low end power”. Which from a standpoint of physics and semantics is just nutty.

JawzX2, Boost Addict. 1.6t, 2.7tt, 4.2t > HammerheadFistpunch 11/19/2015 at 17:03

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High-torque low-moving-mass engines, like, say a 2.5L turbo 4Cyl: will always provide a larger portion of thier available horsepower (due to high torque at low RPM) at lower RPM compared to a similarly powerful NA V6 of larger displacement.

This leads to a “more responsive” feeling engine, with less “high RPM drone fatigue” as far as the driver is concerned, even if they ultimately have nearly identical capability (assuming appropriate gearing). The driver’s perception is king.

jariten1781 > HammerheadFistpunch 11/19/2015 at 17:03

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Yeah, but it’s because people only speak of peak torque and peak horsepower. It’s really unlikely, even in the enthusiast sphere, for people to look at and understand the curves. You’ve got to find an engineer (either professional or well versed arm-chair) to have that discussion.

uofime-2 > Textured Soy Protein 11/19/2015 at 17:06

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“mom mobile driving” aka automatic transmission habbits

RamblinRover Luxury-Yacht > HammerheadFistpunch 11/19/2015 at 17:08

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That being said, a car advertised with conspicuous HP rating only is the dog that didn’t bark, over and over again. An engine with any kind of design priority on torque that’s NA will develop reasonable low range torque, as will any kind of sporty setup turbo. A car that is deliberately hamstrung in the low revs for MPG numbers, not so much.

Montalvo > HammerheadFistpunch 11/19/2015 at 17:08

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Yep, 5252 RPM if I remember right was the magic number needed to convert from one to the other and that was the only relationship needed. If they don’t cross there something is up. If you are dynoing and that doesn’t happen its a quick way to tell if something is off.

Takuro Spirit > HammerheadFistpunch 11/19/2015 at 17:10

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as the former co-owner of a CX-7 (turbo) and a CX-9 (273hp) I cannot comment on these stories anymore.

it hurts insides

HammerheadFistpunch > Montalvo 11/19/2015 at 17:11

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The 5252 isn’t related to rpms, its just a conversion constant that James Watt (inventor of the HP unit) came up with. The lines cross there because the mathmatical formula demands they do

hp=[(torque x rpm)/5252]

KusabiSensei - Captain of the Toronto Maple Leafs > HammerheadFistpunch 11/19/2015 at 17:13

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I also take the unpopular opinion of “There is such a thing as Too Much Power.”

The Eurodiesel guys and gals also understand this. My E300 Merc had a whopping 177hp in a car that was the size of Mars, and weighed about as much (well, not really, but the analogy sounds cool).

But it made 243ft-lbs of torque at 1600 RPM, and had a nice flat torque curve. You might not use the word “fast” to describe it.

(It really wasn’t, getting to 60 in about 8.5 seconds. When the average Cam-cord-ion can do 0-60 in about 6ish seconds, it was only slow by comparison)

However, I challenge anyone who has driven a W210 E300 (or W211 E320 CDI) to use the phrase “lacking in oomph about town” to describe the driving experience.

uofime-2 > HammerheadFistpunch 11/19/2015 at 17:13

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I’ve tried a couple times to write a technical piece to explain how engines work in so far as the relationship between displacement, configuration, management and output, but what I want to explain always gets to long and complicated to be helpul.

Its really simple, but quickly gets complicated and sometimes unnecessarily so. Maybe I’ll try again, just wish I was better at illustrations I think that would help

Manwich - now Keto-Friendly > HammerheadFistpunch 11/19/2015 at 17:15

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I totally understand the difference. Power is something an engine makes and torque is something Canadians wear in the winter.

:-)

HammerheadFistpunch > KusabiSensei - Captain of the Toronto Maple Leafs 11/19/2015 at 17:15

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Same goes for my sportwagen TDI. 136 hp?! Weak sauce! Yeah, but drive it.

JawzX2, Boost Addict. 1.6t, 2.7tt, 4.2t > jariten1781 11/19/2015 at 17:17

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Top: Accord V6 Bottom VW GTI (2.0 turbo w/ mods)

you’ll notice that the peak HP is nearly identical between the two engines, but the 350lb/ft torque peak at 3000ish RPM means the 2.0T is already displaying about 200HP, the V6 has to rev to about 4750 before it’s making 200HP, in the real world, in stop and go traffic, the turbo 4cyl car will be faster because a larger proportion of it’s power is available earlier in the RPM range, removing the (however minor) delay of waiting for RPMs to increase, leading to greater initial acceleration and the ability to space gear ratios farther appart and decrease losses from shifting.

KusabiSensei - Captain of the Toronto Maple Leafs > HammerheadFistpunch 11/19/2015 at 17:18

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33,000 ft-lb/min = 1 HP(mechanical) (by definition)

Taking into account the conversion to radians (1 revolution is 2*pi radians), you get something that looks like:

Horsepower = Torque (ft-lbs)* 2 * pi * rotational speed (rpm) / 33,000 (ft-lb/min)

Rearranging terms we derive:

Horsepower = Torque (ft-lbs) * rotational speed (rpm) / (33000/(2*pi))

Simplifying:

Horsepower = Torque (ft-lbs) * rotational speed (rpm) / 5252

HammerheadFistpunch > KusabiSensei - Captain of the Toronto Maple Leafs 11/19/2015 at 17:21

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yes, 550 lbs-ft/sec or 746 watts if you prefer. The constant 5252 is the rounded value of (33,000 ft·lbf/min)/(2 rad/rev). Basically the 5252 is a way to fit the definition linear mechanical HP into an angular velocity equation.

RamblinRover Luxury-Yacht > Manwich - now Keto-Friendly 11/19/2015 at 17:22

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Ah yes, the random extra Rs added to vowels. Something I usually remember when doing a Monty Python Cornwall accent, but always forget about for Canada.

KusabiSensei - Captain of the Toronto Maple Leafs > HammerheadFistpunch 11/19/2015 at 17:23

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I think we just ninja-collided with our maths.

Berang > HammerheadFistpunch 11/19/2015 at 17:24

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horsepower matters for what though? ;-)

Ash78, voting early and often > Textured Soy Protein 11/19/2015 at 17:24

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I consider that to be the second best trick after the tactic of making the throttle unnecessarily punchy in 1st gear to give the car more “pep”

Seems like that’s a common trend these days, too. And people buy it.

HammerheadFistpunch > Berang 11/19/2015 at 17:26

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HP only pawn, in game of life.

KusabiSensei - Captain of the Toronto Maple Leafs > HammerheadFistpunch 11/19/2015 at 17:27

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Also, I chose the version of the constant that worked well with the other units in the equation.

Because why spend a ton of extra time needlessly converting in the equation when you can start from an easier place?

dogisbadob > Montalvo 11/19/2015 at 17:36

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If they don’t cross, it means the engine can’t spin past 5200 rpm! For example, most diesels redline below 5000 rpm, and many pre-LS small blocks can’t exceed it, either. The late 3rd-gen Firebird TBI’s redline is 4500 rpm.

Nibby > HammerheadFistpunch 11/19/2015 at 17:48

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bro if u dont hav at lest 500hp you a noob lol

DrScientist > HammerheadFistpunch 11/19/2015 at 17:50

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wait a minute, wait a minute, wait a minute...

i just read up to the second paragraph and saw this...

Torque is a force, but it doesn’t have a time component. Think about it like this, you can apply 150 lbs-ft of torque to a lug nut, but it’s not actually moving [in practical terms].

a pound (lb) is in fact measure of weight. weight is mass of the object x acceleration of gravity. and acceleration, as we know, does indeed have a time component. youre thinking of mass which is just mass, and property of the object.

now i’m going to have read the whole thing. and get my red pen out...

jariten1781 > DrScientist 11/19/2015 at 17:59

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Lb can be an abbreviation for a unit of weight or mass. They were conflated for ages. People who work in those units will often use lbm and lbf to keep them separate if there’s a potential for confusion.

HammerheadFistpunch > DrScientist 11/19/2015 at 18:07

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Your red pen will get use I have no doubt...as I’m no engineer...but the principles are all in there someplace.

DrScientist > jariten1781 11/19/2015 at 18:12

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right... but for the situation in question... torque specifications on a torque wrench: are those settings newton-meters or mass-meters?

Bytemite > HammerheadFistpunch 11/19/2015 at 18:18

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It took you this long to understand this?

HammerheadFistpunch > Bytemite 11/19/2015 at 18:19

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...no.

In all seriousness it was one of those things that you THINK you really understand, but I had to figure out a way for it to make sense to my brain.

Bytemite > HammerheadFistpunch 11/19/2015 at 18:21

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Ah...i think I can find a really long reply I posted a while back explaining to someone why they don’t want some “gobs of torque” diesel engine in their sports car. Maybe Ill make a post about it and enlighten some others.

KusabiSensei - Captain of the Toronto Maple Leafs > DrScientist 11/19/2015 at 18:56

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Pound is generally used for force, but in casual use it can be a substitute for mass (substitute for newtons or kilograms)

Now if you convert to slugs, then there shouldn’t be confusion there with pound-force.

BoxerFanatic, troublesome iconoclast. > Textured Soy Protein 11/19/2015 at 19:03

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Because the torque and horsepower measured curves cross at 5252 RPMs, and the horsepower peak is usually above that point, it follows that if the torque peak is below 5252 RPMs, it usually signifies a larger area under the torque curve, which means more horsepower at most RPM points under the peak horsepower RPM point.

An engine with a torque peak near the horsepower peak, above 5252 RPMS usually signifies an engine that requires high revs to reach that power output, usually smaller displacement and either atmospheric, or a giant turbo with lots of volume at high RPMs, but lots of lag at low RPMS, and usually engine tuning like that is characterized as somewhat gutless at RPMs well below the HP peak.

Typically superchargers, especially positive displacement screw-type blowers, supplement the lower-end of the RPM range, dramatically increasing the torque peak in the low to mid-range RPMs, and if truly efficient at that point, tend to restrict and run out of volume of flow at higher RPMS, unlike a big high-speed, high-volume turbocharger with a big impeller, and a big compressor.

New-generation engine tuning with small turbos with very little lag, smooth response, and generally intended as a substitute for displacement, are usually very healthy in the mid-range, but run out of volume at higher RPMS... which is why CX9’s new engine has 250 horsepower, rather modest for a 2.5 Turbo (Subarus were doing that or better 10+ years ago with port injection and rich mixtures)

But the torque is 31o lb-ft at an RPM level almost perfectly centered between idle and redline. That is usually the domain of V6s and V8s.

It is also going to make a big difference between the 2.oL atmospheric Miata, with a high-RPM, lower numerical output torque peak, and Fiat 124’s 1.4 MultiAir Turbo with ~40lb-ft more torque, well under 3000RPMs, even though the peak horsepower numbers are only ~5-10 horsepower different at high RPMs.

jariten1781 > DrScientist 11/19/2015 at 20:47

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Ah, roger, I see what you’re getting at. I just assumed his argument was an attempt to explain the time component of power.

Carbon Fiber Sasquatch > HammerheadFistpunch 11/19/2015 at 23:38

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I just want to say that posts like this and resulting comments such as these are why I’m on Oppo.

TheD0k_2many toys 2little time > HammerheadFistpunch 11/20/2015 at 00:36

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i like my diesel torque

davesaddiction @ opposite-lock.com > Takuro Spirit 11/20/2015 at 10:20

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Do you think Mazda has overcome its past troubles with turbo-ed engines, and this new motor will prove as reliable as the rest of the bunch? 17.4 peak psi is nothing to sneeze at. Those are some serious forces at work...

Compared to the above mentioned 5 Series he said, “At about half that we have the Mazda CX7 [from] 2007, which everyone knows is a really bad engine … It’s a known horror story.”