Why Do Horsepower And Torque Cross At 5,252 RPM?
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- เผยแพร่เมื่อ 20 ม.ค. 2018
- Do Horsepower And Torque Always Cross At 5,252 RPM?
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Horsepower and torque. They're interwoven, important for the speed and acceleration of your vehicle, and the desire of every gearhead.
You take your car to the dyno, and you notice that torque and horsepower cross paths at 5,252 RPM. You add some modifications to your car, increasing both power and torque, and yet again they both cross at 5,252 RPM. Why is this, and is it meaningful? This video discusses the physics, the theory, and the math behind this magical number.
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Hope everyone's having a wonderful day! If you're watching and confused about what the difference are between Horsepower and Torque, I have a previous video to sort that out: th-cam.com/video/u-MH4sf5xkY/w-d-xo.html. If you're watching this video and you're thinking, what the heck, math!? We all feel similarly haha. If you're watching this video and thinking, really I just want to see pictures of cars and the sort, here's my Instagram: instagram.com/engineeringexplained/
Long story short, it's just a side effect of the math used to calculate power.
hey the kilowatt formula is wrong i used it on my aprilia rs4 125. .
11nm at 8250rpm
15hp/11kw at 10500rpm
That was wonderfully pointless. Thank you !!
I followed all of this until you lost me. I'm just not saying where that was :) There's a reason why some of us chose law school, like almost failing freshman calculus.
hey i have a video idea, and a question that stems from this video. how does the outside tire diameter and potentially the rim size impact haw horse power and torque are delivered to the road to help accelerate a car?
Put a mic on that marker so we really hear that squeak good
is that a new fetish? interesting.. asmr? :D
Oh yeah, squeak it hard for me baby!
Easy upvote.
The squeaking is turning me on
Sha Dow I wish I was a marker
And if the lines actually cross at 9549 rpm you not only have a metric chart, but more importantly an amazing engine.
Someone's using a rotary engine lol
Hah, yes, that was my reaction. "They normally don't cross? o_O"
I mean hondas have an impressive high rpms dont know why people hate on the well build ones
Well. That isn't high at all for a motorcycle engine.
Depends on the bike. Mine redlines at 10,500
"it's completely pointless"...died laughing there and continued to watch :P
*presses replay button*
Steve Oswald me too! Lol
@@esunisen3862 Turns Loop on...
:-)
I dont see a standardization as meaningless
“There is nothing exciting about it” 🤣
As a Mechanical Engineer myself, believe me it took awhile to understand the concepts during the process of obtaining that degree. Curiousity with how things worked along with being a gearhead kept me in play. Its a matter of sticking with it and lots of study. Love the Channel !
Where did you get your degree? I'm interested in mechanic engineering but I have no idea of how to get started. I can't afford to go to a technical school and I'm 34 so it will probably never happen.
@@BadBusiness.357 I'm a mechanical engineer and I don't understand your question. I got my degree from Michigan Technological University. Mechanical engineering is a 4 year degree and is mostly theory (or at least it was when I was going to school in 1990-1994). When I hear "technical school" I usually think of a 2 year community college with practical degrees that will prepare you to be useful in the workforce, but don't involve a lot of theory. By "technical school" do you mean MIT, Cal Tech, Stanford? If so, I agree, that's A LOT of money if you don't have a serious scholarship. Many state schools offer degrees in engineering, total bill will be around $100K if you include everything (tuition, room and board, books, etc)
I can learn the math, but the tests are too quick for me. My hand writing just keeps getting worse, & I can't write small.
So you know his speed equation is extremely over simplified because there is no slip or deformation in his world.
Unit cancellation is so satisfying...
Looked at comments to see if it was just me that found this satisfying... Evidently not
that sounds painful
That's how you double-check that you set the equation up right.
sexually* satisfying
Yes, it is like a full row in tetris. Never gets old.
Pointless you say yet I feel smarter after this video...I'd definitely give this channel most informative award.
The relationship of power and torque comes up a lot in certain circles, but there is a heap of ignorance being spread at the level of folk lore "Torque wins races." etc. Being walked through the math is helpful to the internet at large. 5250 might be arbitrary; but pointless, this video, was not =D
I feel smarter too! Never quite understood when I was reading car specs what this meant. You satisfied my engineering car/geek question that I have never understood till now! Thanks!
So glad you actually put science behind it. So many do not understand tq, hp, and how a dyno works.
Different style dynos work differently. An old Clayton water brake chassis dyno works nothing like a modern Dyno Jet chassis dyno.
Different dyno = different numbers
Different dyno operators = different numbers
Dyno operator can manipulate the figures to make more hp/tq or less hp/tq as well from my understanding.
I've seen this on 2v 4.6 mustang forums .. full bolt on cars don't break 290hp even with cams they barely scratch 300hp without extension work on heads . When someone posts a 350hp or 400hp dyno graph people call them out or the dyno operator out pretty fast.
@@codyramos3200 Agreed. A dyno is really just an idea of where one is starting from. Any mods should be measured on the same dyno with the same operator.
This video is exactly why I love this channel, it's entertaining and informative and Jason is honest about how this doesn't really mean anything :)
Clips like this is why I watch.
Im off to spread useless but interesting knowledge
Ludacris Leon
If you understood this video, you would not call this knowledge useless.
Ray Truant I understand but I am not an engineer, mechanic, car salesman or anything. So yeah, for me this is useless but interesting.
@@ludacrisleon828 general knowledge will always come in handy
@@ploperdung lol, If only this Knowledge counted as general...🤣
@@markburkey6371 knowing about horsepower and torque doesn't mean you have 300 IQ, this knowledge is pretty general, this is just surface knowledge.
This was definitely a mathematic nerd out in which I enjoyed. :)
If it wasn't for you I wouldn't know half as much about cars as I do.👍🏻👍🏻 keep it up
Luke Cates I went to school for automotive but EE has great refresher courses for people who just want to hear it all again
Jack of Blades yes, he definitely is.
He reminds me of my fathers typical conversations, but in a younger brothers body.
Funny coincidence, we had been doing an assignment/having a discussion in class about horsepower vs. torque when your last video was published a few days ago. There were a few questions from my students about why you never mentioned the 5252 thing. Well, here ya go!
I think it's awesome that Jason's material is being used by educators. While I obviously hold that Teachers and Educators in general have a firmer understanding of the materials they teach, it has been my experience that the concept is oftentimes easier to digest when explained by someone of relative age.
Whether this has to do with words or analogues used or not I can't say, but I wholly approve of access to, at least potentially, complex concepts in digestible form; a skill at which our friend Jason seems quite adept.
@@Nikolai18A " I obviously hold that Teachers and Educators in general have a firmer understanding of the materials they teach" He has an engineering degree, he would know more about it than a school teacher.
@@ploperdung I disagree in part. Educators are necessarily more engrossed in not only the subject matter, but in breaking it down for others to comprehend. Such things are only possible when a comprehensive understanding of the underlying concepts is present.
I don't discount the potential of a "student" understanding better, or more completely; obviously every educator was at one time, a student. But by and large I find that educators grasp the subject matter far more accurately than their students.
@@Nikolai18A i agree with that but i said that the guy on this channel has an engineering degree and that he would understand better than a teacher.
@@ploperdung Who, praytell, would have taught him, certifying his degree? Professors; educators.
It's one thing to understand the material. It's quite another to understand the material in a way that enables you to accurately relay complex topics to others. That's not often an inherent trait (and I think our friendly neighbourhood engineer has this inherent quality), and is a difficult one to teach in its own right.
Always a well-made video. Good to see the whiteboard back in action!
She'll never retire! :)
Best way to spend 6 minutes learning something absolutely pointless xD
rainystorm88 Hardly pointless. It shows plainly the difference between using different units of measure, which helps any curious person. I submit you are actually very curious.
If anything it gives people who generally don't think, use, or may find, mathematics hard to understand an opportunity to flip light on... when someone is speaking about something they're generally uninterested in in a way that coincides with something they are interested in... it really helps....
Math is *never* pointless!!!! :)
rainystorm88 pointless? NO!
Maybe you should stick to making those pointless videos in your channel and leave those who are intelligent to these videos.
I love when formulas are explained in a way that I can grasp. Well done. I learned something and I enjoyed it.
You explain things with engineering basics that's the unique thing about ur channel. Satisfys that inner nerdy engineer in me who wants to know why and how based on facts. Grt job
Happy to hear it, thanks for watching!
My car's redline is 4800 rpm😹
is it a diesel?
Your horsepower is not as important as torque!
Faris Muhammad yes
shpyrko i know😂
And thats why your rated torque number is much higher than horsepower
I've never enjoyed a meaningless piece of information so much.
Haha, happy to hear it!
@@EngineeringExplained ok
Never knew this! Now I will have something to talk about at the dyno tomorrow instead of worrying if my BRZ will break 150ft.lbs of torque 😐
Jason is really a wizard, he just chooses to shave his silver beard to go incognito.
Gandalf
Great explanation. Please do a video on "why most cars develop maximum torque at mid-range RPM instead of at high-range RPM" and "why the best acceleration effort of the engine occurs when the engine is churning-out approximately half of its total power rather than when it's churning-out all of its power."
Once again, thanks for all your great videos. Please notify me when you do the video in suggesting.
That 1st question would be a good video
Funny, I was looking for this formula yesterday whilst working on my dissertation project. Decided to watch this on my lunch break today and voila!
I found it a few days ago and I'm just some guy. Coincidence? I think so
I had heard you refer to it before but had no idea what it was about. Great video, thank you for this.
Insightful, interesting, and informative as ever - thank you for the video!
I appreciate that you include the conversion in the metric system. Nice video, love this channel!
Nice. Just a little tidbit I never thought about before. Cool video.
Thank you for this video I grew up building engines my father was a racer and I learned that a properly designed engine would do as you say but I never understood why till now. No one taught us anything except the bare minimum back then.
Great video, in fact I was curious about this exact thing but now I know. This saved me the google search for that hp to ftlb/min conversion. Much appreciated.
If your kid hates math, but loves cars, show him these videos, and he will ace all tests:)
Zoltán Juhász unless its statistical maths 😂
Thomas Fooij See his videos for example about comparison of tires. He did multiple runs, and took the average of them. Engineering is also based on statistics
Yes - an IMPORTANT factor in effective learning - you need to have a real interest in the topic - then learning becomes FUN and not a chore. (and Zoltan - HA - it should be "...show him or her..." Some girls like cars as well, some boys do not like cars as well - HA)
Private Private (Ah, I hate that english is so gender biased, I never sure what is the best expression. In my first language, all pronouns are gender neutral...)
Yes - HA - easy to get someone all upset over nothing.
God I love this channel.
You are the Brian Cox of car stuff, and its AWESOME!!!
Jason, you have the power to make me feel smart because i understood your clear explanation.
engineering explained your all in one channel for car guys and everyone wants to be involve in automitive tech or industry
should have did a mic drop with the marker and walked off frame, nerd cred
I appreciate your simple explanations of the math involved n engine design. Being the nerd that I am I use these constants often. I am amazed that very few people understand BMEP.
You brought back some fond memories. In the late 80's I was a Dyno Tech in the engine overhauls shop at a Detriot Diesel dealership. My job was to take every engine that had a fresh out of frame major overhaul, do a break in run, then full load dyno tune (someone else ran the in frame overhauls on the chassis dyno). I vaguely recall using the Torque X RPM ÷ 5252 equation to figure HP because our dyno only displayed torque.
Thanks for this, and all your other videos.
Subscribed!
I would've ran the torque output graph through excel and made a HP graph using the same formula ;)
Interesting to note, if you use the proper Si unit of angular velocity (rad/s), kW and N*m should cross at exactly 1000 rad/s.
that's because a kW is 1000 Watts, if you used Watts you'd have 1 rad/s
Jason, you excel at what you do!
thanks a lot for all the great videos that you upload ! it is of great help .. keep the good working throttling 😇
This equation stuff is so satisfying, i get why my maths teacher makes a big deal about it
Kasam it does get exciting especially when you begin to understand it...
I'm pretty sure the intersection at 5252 (in imperial units) does allow me to make one assumption... When a vehicle's peak power rating is higher than it's peak torque rating, I know it's a relatively high performance engine (or at least that it's power peaks above 5252rpm).
I feel smart!!! I already knew the exacts reasons and maths behind this from engineering school. Always had an interest in both cars and engineering, and it was annoying in my youth not being able to explain to friends that hp and torque are related, and not independent.
Thanks so much for all your videos , you are a great ING.
You inspired me to become a mech-e!
That’s awesome to hear, appreciate you watching, and best of luck with your career!
Nothing quite like a 6 minute video that ends with "in the end, it's pretty much meaningless but thanks for watching"! Honestly though, it was an interesting video even if the magic number is meaningless.
interesting, as always! And thank you for thinking ot the outside world and including metric units :)
Thank you for the excellent explanation
Best 6 meaningless minutes I spend today. Good work!
Math is your thing, that's the thing that sets you apart from other channels. keep 'em going, It doesn't matter if it's pointless math, or if I get lost halfway of the video, I'll catch up with you eventually.
Best educational video i've ever seen :D
Your channel is a goldmine of informations, thanks for everything !!!
(I'm working at the French Motorsport Federation, and I sometimes watch your videos to give some technical advices ;) )
Keep up the good work \o/
Cheers,
Donnie
Thank you for explaining that this happens when they are using the same scale on the left. I looked at my dyno chart and they were crossing at the same point (both before and after a tune), but they were crossing around the 4800rpm mark. But torque was on the left and power was on the right. Different scales. Great video, thanks a lot.
That's when the VTEC kicks in!
"That's when the VTEC kicks in, yo!" Fixed it for ya.
Engineers. Putting two different units on the same axis.
It's just 2 graphs in 1
@@crashTestGuru then put two y axes with different units on them to the left and the right.
@@andraslibal there's no need to use separate y-axes if they're similar enough numbers. Them not being the same metric doesn't make a difference, in SI units you would need two Y-axes to make it readable but in imperial units a 100 ftlb engine produces close enough to 100 hp for it to not matter and they scale at that.
If you want to get accurate then you shouldn't have two separate y-axes, but two separate graphs instead, one for torque one for power, then each graph can have two y-axes, on in imperial and one in metric, or vice versa.
Some units are " dimensionless" in physics engineering equations .
It's so awfully convenient
Imperial user here , still watches. Nice video ! But in metric 1HP=749W, So how can it become 9549?
Jason, you salt & peppered genius. Thank you for answering my question.
At first I was like, "oh God algebra." And then at the end I was like, "oh that makes sense."
What algebra?
It's algebra. He's solving equations, which is algebra.
dont worry just remember your audio is 200 watts!!
Would it be any more efficient to have smaller pistons working together or fewer larger pistons?
Yeah? Like 2.4L 4cyl vs 2.4L V6 perhaps?
I'd like to know this as well, although the bore to stroke ratio will play a big factor. Difficult to have an apples to apples comparison, I would presume.
I'd also be curious to know if adding say 2 cylinders to an inline 4 (all else remaining equal) would increase power by exactly 50% or would there would be a greater increase by having more firing events per revolution...
It’s got to be 4 cylinder hasn’t it? Since there would be less parts to spin and move, less bearings causing friction, less pistons moving causing friction (admitted since it’s all oiled so makes minimum difference but surely does still make a difference)
Anton more like 8 2L cylinders vs 4 4L cylinders. That's what I think he meant.
Yes, or maybe even 20 smaller pistons? Is there any difference in getting the ignition to happen in smaller or larger chambers or could more smaller pistons be more efficient, lose less heat, or produce greater combined power perhaps? Basically, is there a specific reason for pison sizes and the 4/6/8 number of pistons in most vehicles?
Very nice explanation!. It's always interesting to know where the things come from. Thanks for teaching.
As always Jason, expertly demonstrated and explained. Sadly most car enthusiasts won't understand any of this, but what can you do...
But european often use other Units than kW like bhp in england or PS in germany
Yes, you can tweak the equation for any unit, and the RPM will be different.
Well, PS is Pferdestärke, wich is the direct translation of Horsepower
1 PS is not 1 Bhp its like 0,98 bhp
Those are very close to imperial Horsepower so the intersect value would be very similar either way, and he did mention in the video that units don't matter, since it's an arbitrary point anyway
PewPewLazors but 1 PS is 1 HP
Praise Be
Under his eye.
Mad Max Chumbucket reference?
Joe DeSalvo, to God.
Thank you again!
Great information!
I've learned so much from you. Thanks a million!
1 HP = 745,7 W
One metric horse power is 735.49875 watts.
@@okaro6595 Indeed Mechanical (or "imperial") ~ 746 watts vs Metric ~ 735 watts.
This video made me insanely excited. Todays my birthday and I woke up to the notification so I was like he knows lol. Great vid as always man! You shoud totally make a joke video explaining the cat/bread and butter perpetual motion machine lmao
Happy birthday!!
HAPPY BIRTHDAY
Thanks guys!
I really enjoy your channel because of your ability to explain the math and logic involved. I was blown away by all the dyno graphs showing a tq / hp crossing at 5252. I had not noticed this for many (many) years. If I understand correctly, a dyno only measures torque. It calculates hp based on TQ*RPM/5252 hence the 5252 crossing. Correct? Also, If you live in Boise, I would really like to meet you sometime. Alan
Best video yet! You should make more physics based car videoes.
My brain hurts now
Hi!
How is circumference(rpm)=velocity I don't get the logic behind it
The distance the tire travels with one rotation (distance) time the number of times that tire rotates per minute (rotations/time) ultimately gives you distance/time (velocity). Hope that helps!
If the tire would rotate once an hour, the speed would be: Circumference / hour, as the car would travel exactly that distance. It doesn't change anything if it is rotations per minute, as rotations per hour is just 60*Rotations per minute
louis chim
Velocity=distance/time
Circumference is distance and rpm is time also saying how much of that distance is being covered in the time.
For example:
V=circumference in meters x rpm
V=2πr × rpm
V=2π5 × 10
V=31.4 × 10
V=314 m/min = 5.233m/s
The circumference is the distance and the rpm is telling me that it's being covered a certain amount of times in a time frame, giving us asked. Speed is distance over time.
So, it's more like
Velocity= (circumference x rotations)/ minutes
In turn, meaning
Velocity= distance/time
Derpu Wolf best explanation...👆
Thanks guys, I like the way you guys explains stuff is exactly like my physics lecturer.
Nice explanation, thanks!
Saw this Video Title a week ago but never watched... Then I started noticing all Dyno Charts meeting at 5252 and it started to drive me crazy!!! So, here I am watching why! Thanks!!
it's not different for every engine ??
Works for any engine; the "why" is explained in the video. :)
no, but it's a meaningless number...
I ask because it don't work on my cars ... but they are not stock ...
It's a mathematical proof. Therefore it's true for any value. So no every engine is the same, and will cross over at that point
The only thing Jason didn't emphasise enough for the non-mathematical amongst us was that this number is DIRECTLY derived from the fact that one horsepower is 33,000lbft/min. He explained it above, but your question intimates you didn't hear that info.
Had James Watt decided that one horsepower was 40,000lbft/min then the 5252 number would be 40/33 times bigger, and the dyno graphs would cross at 40,000/2pi = 6366 rpm (to 4sig.figures)
Again, the silly part of all this is that its arbitrary to say the least. In Europe we mix Horsepower for Power units and Nm for torque, and don't see the graphs cross because they are not dimensionally consistent.
Wait, what?
?
Wait, Watt?
Wait, horsepower?
That was a great explanation, Jason. Whenever I'm asked, I usually just tell people that, basically, one is a force, and the other is a rate. Also, to answer one of your commenters, when you're talking about torque, it is lb-ft, and when you're referring to the unit of work, it is ft-lbs. The automotive engineering industry reversed it in order to distinguish what was being discussed... Thanks for another great video, Jason!
Back in a time before calculators I spent an afternoon at a car museum with an engineer who would do those calculations with a slide rule. It was all magic to me at the time and it wasn't until a couple of years later when I got to college that I figured out how he did it.
Great explanation.
Because horses
is this guy 25 or 45?
33.5
Both
Yes
You should consider doing a video on pounds mass (lb) versus pounds force (lbf) and also include the correct terminology for imperial torque (pounds force feet). This get messed up in conversation so many times and while most understand what is meant, it drives me crazy.
Good videos, fun to watch.
Nicely explained. I had not heard of this 5252 prior to your other video, but it appears I haven't been missing anything from my formula collection.
My redline is 5400 so does it still cross at 5252?
Yes
Yes.
How?? 😂
It would have if your engine would survive that many revs. Sounds like a diesel.
Basically your torque and horsepower curves are on the way to Crossing but your engine runs out of RPM before they do.
Napster6 it's a jeep grand cherokee 5.7 v8 2009
What about tiny cars that can't cross 5000 rpm?????
Tiny cars rev just as high try diesel Trucks.
they wont cross.
Raitzi that means tiny cars can't reach their peak power!!!
LOL. Of course they have a peak power. But before 5252 rpm. Btw, if you examine a dyno-graph of a diesel engine, the power and torque lines converge to each other around 5252 rpm.
Gabor Szabo I have never heard truck reaching 5000 RPM, max 2000 rpm only
Excellent explanation, very good to know!
helps me a lot! thank you
3rd view before the hundreds of thousands!!!
What a meaningless entertaining video, Jason 😂😂😂 But idc i like it anyway...
This has to be the first video of yours that went straight over my head.
VERY well explained and presented! Opened my eyes to a couple things....Thanks!
And we learned nothing today :D
lavix5 that’s your problem, if you already new that why did you expect to learn something new?
A meaningless video. Thanks, Jason! LOL
This channel is so awesome, a lot of help since im studying to be a mechanical engineer
this channel just keeps getting better
That is really well done and a most apropos subject to demystify dynamometer tuning. I never gave a thought to Imperial units vs. ISO metric units determining the "cross over" figure.
One thing I would like to have seen is the expression of R.P.M. as "R/M" - Revolutions over Minute. That would make the cancellation of the minutes unit more clear.
Compare how R.P.M. is expressed to the horsepower equation: 33,000 ft.-lbs./min. The "minute" unit is in the denominator.
Great explanation!
So glad you finally explained this.
great video.. as a mathematics/physics student, i like how you can simplify functions :)
this explanation is perfection. thank you
are all these videos one-takes? maybe I'm not watching close enough but that would be bloody impressive, especially with all the info that needs to be A, remmembered, and B, spoken about in a clear and coherent way, possible that there's a script or some sort being shown off-camera but even so, well done Jason!
perfect explanation!
What a brilliant lucid explanation. Many thanks. I love that in the end does it matter well no! Some useful maths though.