How Horsepower Affects Acceleration
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- เผยแพร่เมื่อ 23 เม.ย. 2013
- How does horsepower affect acceleration? How does more horsepower translate to a quicker car? This video explains at a basic level how an increase in horsepower will yield faster 0-60 times, thus better acceleration.
Note: This video assumes traction is not the limiting factor in acceleration. In reality acceleration times could be much different to due a lack of tire grip.
Be sure to check out:
HP vs. TQ: • Horsepower vs Torque -...
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Yeah I was getting a bit of a cold when I filmed this. I'm good now haha
Can i use this for finding acceleration of electric car?
Just looking at all those imperial units and arbitrary conversions makes me cringe. But the information is solid! Thanks! :D
Thanks for making this! I was always interested in this, and had a rough idea, but you've made it much clearer and ironed out a few mistakes/oversights I had imagined! Thanks!
I think you can use the aspect of kinetic energy. For an object to achieve certain velocity, that object has to be given some kinetic energy. An engine with more horsepower, meaning it can give vehicle more kinetic energy in SHORTER time, hence more horsepower=quicker acceleration.
hp can put energy into anything regardless of short of long term
The two come as a pair. But ultimately the force at the tires comes from a torque at the crank. Typically if you increase one, the other will increase as well. You may wish to check out my video "hp vs torque" if you haven't already.
I have been looking everywhere for this exact formula and I can't believe it was one of your first videos. I have watched every video you have ever uploaded and must have forgotten you did this. I have been working on a game/application to plug in vehicle weight, HP, gear ratios, drag, etc.. and then show an animation of your car realistically accelerating and giving you acceleration times and top speed. Then you can go back and tweak some things and see how it effects the results.
That is awesome! And very cool swap, do you by any chance have any videos or pictures of this? Would love to see it.
Good work. Now you can use these equations along with the torque curve and plot every gear in acceleration vs vehicle speed. This will show why a flat torque curve is so important.
Yes, though including downforce, and much stickier tires such as those used in NHRA drag cars, you can get up to 4-5 g's of acceleration. They post 60's under a second easily.
im trying to do my homework here...but im learning so much!...must...stop..watching
Either way you're learning, good for you!
Me too, I can't stop blowing off my homework to learn something I'm actually interested in.
Challenge complete. That's the playlist I'm working on now haha. Check it out on my channel page "How to increase horsepower"
Yeah as long as you can get up to the speeds you want, short gears are fine. And yes, those are topics I should eventually cover.
No idea, as I know nothing of the software. That said, if it takes into consideration other factors (friction, air resistance, altering torque curve, etc.) it could be more accurate.My video has several basic assumptions (so that the principles can be understood) which could make the conclusion unrealistic.
Your videos are great, keep up the good work!
Hey, i love your videos! How you explain everything. Simple and very easy to understand! Im right now really into automobile mechanics. Its very interesting and i just love it! Plan to keep studying it. But hey, a good suggestion for a new video would be on steering wheel. How does it work? What types of it are there? You should do a video of that. :D
The soft is just a vehicle dynamics tester, I just took your data in the video to feed the software and see if I could get the 1.3s. Would be awesome if you could make a Part 2 of this video trying to reach a more approximated value. Keep on the good work bro!. Thanks for the vid!.
Spoke too soon, you've got it on your channel. Awesome!
I tried these calculations for my 2012 Focus 5MT. I could only find torque values at 4450 and 6500 RPM (146 & 129 lb-ft), so I used the average of those two data points. Assuming I take 0.5 seconds to shift, I calculated 6.4 second 0-60mph. Car and Driver tested it at 7.3 seconds. Pretty cool math!
I know, I know, you're upset I used those darn American units. Hear me out - when I made the two separate videos for my video on weight differences, the 'Murica units received 4 times the views. I understand that the units make no sense, but converting really isn't that difficult. All of the equations are labeled without units. You use the metric system, so I know you're smart and capable of the quick conversion! :)
Thanks!
Thank you, this was very helpful👍
Thanks for understanding! What engineering are you going to school for?
Love the video , really surprised how much I forgot at college. Would you ever write a book to put all this information in ?
The feeling of getting pushed back to your seat during acceleration is caused by Newton's first law of motion, which is Inertia. You (the guy in the car) and the car are two seperate entities. When the car accelerates, you technically stay at rest while the car moves forward. The car will then "push" you so that you will be at the same speed as the it. You're not actually getting pushed against the car, rather the car itself pushes into you so that your body accelerates from rest to the speed that matches the car's current speed.
Wanted to say thanks for the videos, very enlightening and educational. I homeschool my 14 y/o sons and use your vids sometime to review concepts we've covered in geometry, physics and algebra. They can see direct applications and implement the concepts on our '68 Porsche+STi engine swap. Keep up the great work!
Hahaha, not quite! Perhaps I can do an update at some point on what I do. I work with forklifts, which do have many of the same systems. They're just much heavier, and can pick things up.
Yes, it's the basic principle of how dynos work actually, by accelerating a drum and seeing how long it takes, then back calculating the torque applied.
But how many elbows per lunar G does it take to reach 500 frog jumps???
+Sanjuro Makabe 42
Interesting topic, maybe one day!
Because it's very simple to have a high torque value with gearing, where as gearing will not affect the horsepower. The torque at the wheels could be a bit deceiving when you simply have to change gears at 10 mph because the gear is maxed out.
Some recognition of the 'Metric' system would be beneficial!
Well technically you have to include weight distribution, and weight transfer, which I have not yet covered. So the real answer is yes, but just from a basic point of view (like this video) I did not consider weight distribution/transfer.
Thanks, I would love to meet your engineers! I'll definitely check out the channel, feel free to PM if you would like to collaborate on anything!
No worries!
Nice video, thanks for making it
Could be almost anything. You can probably find a torque curve for your car simply by googling it, or at least get the max torque number.
Of course - one step at a time for understanding it though.
Yes, all I would add is the obvious statement that HP is calculated by measuring torque and RPM, not the other way around.
I have videos on both topics, just try searching my channel! :)
holy moly! you look a little different lol! thanks for making all of the super informational videos!
Engines don't need back pressure, they need the exhaust gases to have some velocity. Search my channel for "exhaust increase horsepower" I've got a video explaining further.
Freakin' love these videos!
Nice vid, but I think the more interesting question how it affects acceleration with a non-flat torque curve, as in all combustion engines
Yep that's a common misconception about needing backpressure. It's is perceived that way only on modern engines, because the ECU needs to be re-programmed to 'see' the difference. Once you do that, you'll see the gain of going to straight pipes. p.s thanks for all the informative vids!
Awesome vid dude, just a question, I used a software called nxgtr sim to test the learned theory, but I got massive different results, that same setup gives me ~2.25s in the 0-20mph, that's over 73% error-difference (seems too much), I may say for sure one of those results is wrong, any thoughts?
Ohh gotcha
Could you do a video about the braking system and the steering too?
Not really. But if someone has your same car with a dyno chart online that's a good place to start.
The 0.7g is obviously assuming no losses.
Ive tried these calculations for a few cars and they always give really high acceleration, ive even taken into account rolling res and drag
What other losses would need to be considered to give a more realistic value?
Drag, drive train loss, rolling resistance...anything else?
At the wheels, or theoretically at the engine with no losses.
hi, its my dream to become a mechanical engineer and work with cars, so i was wondering where you go/went to school cause you seem very smart with cars!
@pap lazaru, your number represents an upper bound on acceleration with weight transfer already all the way back. Most cars won't have the traction do a full on wheel stand (which is where you are at if you get 100% weight on the rears) so they can't even reach that let alone better. Having said that, the coefficient of friction in pneumatic tyres is an odd thing, and under the right conditions can definitely exceed 1.2G (e.g. warm drag slicks on tarmac).
Thanks a lot nice video ! Is there any way to find the avarge torque easily ?
That's about the same as my Integra (which is a bit slow).
If you think about the equation which you can construct a power curve, the equations already exist. You can plot the results for every step in some software like matlab, or even excel,and get the shape of the power curve, then you can easily get shape of torque curve also.
That's such a badass engine swap! both engine and car!
So shorter gears are better as long as you can keep a higher average horsepower and dont lose too much time shifting? Btw could you go over stuffs like powershifting, revmatching, double clutching etc. I find many people will find those techniques interesting. Thanks for a great channel as always. /swede
Hey bud! Two Video ideas.
1. Obviously we know dyno will read drastically different depending on brand, location, and environment variables. I know many people say you can accurately measure real hp by a cars et or trap speed calculated against its weight. Nobody has been able to accurately explain the math on this. There are variables on changing gearing to accelerate faster would change your hp calculation.. but there MUST be a way to calculate this.
Second. I think motor trend did a video back in the day but I can’t find it.. explaining why in a standing mile.. starting from a stand still vs starting at 60mph, or any speed for that matter,... your end speed really doesn’t change. I’ve seen this at the track with roll race events vs dig races. My et is obviously faster but my trap speed maybe increases by 1mph. Doesn’t matter if I’m doing 20...60..80... or whatever to start.
I think the first idea would be awesome for helping people figure out a more accurate way to compare friends actual hp numbers.. would be cool. Thanks bud!
What happened to the primary reduction discussed in car gears. Does your model assume crankshaft out rpm equal transmission in rpm.
could you make a video showing how straight pipes can lead to loss of horsepower? or basically' how engines need some back pressure. thanks
I have a question
I just rebuilt the engine in my 91 mr2 and I've noticed it sputters when I put power down off the start (when the engine is warm). I had the timing at 10° TDC and moved it to 12° and it helped a bit but it didn't solve my problem.
Could you do a Video on the true Liters of a Rotary? There is Major speculation on what it is.
well just saying that for people who doesn't know whether to choose for a engine with more torque or horsepower when buying a vehicle. I think EngineeringExplained (Jason) has a video of explaining HP & Torque
hi i have a bike and i would like to know witch gear should i change to get more acceleration, should i get a biger gear on the wheel or a smaller in the motor?
any link or video where you might have just described the FBD and calculative difference between RWD and FWD ??
The units here are figures. The concept is much more important. I don't care if you wrote the units in French, as long as I know which are greater, I would understand this video. Thanks for taking the time out of your day to do this.
I think from a standing start at idle speed acceleration is rooted in TORQUE. If an engine has enough TORQUE it needs NO series of gears in a transmission to begin forward movement and accelerate up to top speed. It just needs Park, Forward and Reverse. IF your engine has the space to lengthen the stroke, and increase the bore diameter of the pistons, but you want to do ONLY one or the other, I think increasing the bore diameter is the better way to raise your TORQUE number. Am I right about these things?
Also the wheel size is that including with the tire? So if i have 15" alloys i need to add a few more inches to take in count for my tire no?
I like your videos. Do you take requests? I have a specific horsepower related question that I am curious about but can't figure out myself.
Zack Hyde You can always ask here, if I can't answer someone else may!
Cmon ask
Is the hp at the wheel or at the flywheel? I want to calculare my 0-60 time with my mx5 turbo. I guess i could use this equation to do mine in kg?
wil there be a difference in calculation if i consider a rear wheel drive?
Not forgetting the maximum grip you can get from the tire and road surface, which will limit the acceleration.
That g-force is created by the torque of a heavy flywheel which pushes us back in the seat. We Americans and the Germans call THAT power It is actually a torsional momentum. Racers use high revs to get power which better controls sliding wheels or those that spin. I enjoy Gwrman style torque spinning wheels at 40 mpg
come on ofsoudminds
please help me out here and answer the questions so that I will not go about the rest of my life being misinformed
Use 202 since you know that's what it produces.
My car produces 202 whp which caculated to bhp is 241 bhp so which one should i use?
The torque is not really decreased, it's "moved" up in the revs range. That means the engine is more likely to stall on low RPM, but the engine will rev higher. Power is the product of torque times revs, so increasing revs increases power for the same torque.
You can't choose between horsepower and torque, you can choose between torque and red line. So if you want more horsepower, you have to increase one or the other. But increasing the red line is only worth doing up to a point, so you're best to increase torque by for example - adding a turbo charger.
its this equation able to be reversed to get a guesstimate of what your HP might be? such as my vehicle weighs 9,417Lbs, wheel diameter is 37", gearing is 4.11, and i can do 0-60 in roughly 7.5 seconds, first gear is 2.45 ratio. is this enough information to get an idea of my torque/hp?
Could you explain exhaust back pressure?
Yes, measure the tire not the wheel.
If you say max power is produced at 5252 rpm...which would be 9549 rpm if you calculate in metric units...then why do different vehicles have peak power at different rpms ??
Check out my video "how exhaust systems can increase horsepower"
can u please provide me the calculation of trailing arm and suspension geometry.how to decide angele btw two wishbones and A ,..
Doesn't finding the torque at the wheels and dividing by the radius to find the force tell you the force on the wheel (which ultimately comes from the engine) and not the force of the road onto the wheel/car? Knowing the torque exerted on the wheel from the engine etc. doesn't tell you the *net* torque on the wheel because you haven't accounted for the force of the road onto the wheel (static friction) which acts in the opposite direction.
Please clarify Engineering Explained.
Why do you plug in hp to calculate the torque the second time ?
I do '0-60' (0-100km/h here in Aus) in my GSR evo 3, red line at 7,500 :P and 15 pound of boost from 5,000 onwards
I don't know if someone asked this: do you have an equation to get your 0-60 if you know your torque curve (say you have the spreadsheet for each step of 100rpm)? I guess it involves some calculus but I wonder how complicated it would be if someone took the time to come up with such an equation. I was thinking you could average between 800(idle) and 7000 (peak hp) and consider it flat but then I thought you spend different time at each rpm as torque changes so a weighted average is more suited..
What's your opinion on the new BMW F30 320d acceleration 0-62, in just 7.9 seconds?
I’m so lost but I like this video
if my car have maximum power in low rpm and high torque, it will accelerate slower than a car with maximum power in higher rpm and lower torque than mine?
Considering the same gear ratios, wheels size, car weight.
for example: Car 1 have 128HP at 3800rpm and 29Kgf.m at 2000rpm
Car 2: 138 HP at 5600rpm and 19,6Kgf.m in at 4000rpm.
which one will accelerate quicker?
I think you misread my question. If you *already* have the torque curve (and implicitly the powercurve which is irrelevant in this case) how can you get your 0-60 time as accurate as possible considering torque varies throughout the rpm range? I know you can get shape of the power curve if you know the torque curve :)
Thanks, Great Video. But.... those units.... omg. Why so much trouble.
The sum of our weight is greater than the sum of your weight (in pounds, of course), hence this video.
So if you have bigger wheels the force decreases (F= torque/D) and that means a lower acceleration?
Yep
So why do sports car usually have big wheels? (Besides the fact that they look cool)
Due to contact with ground. The larger wheel has more traction due to increased contact area to ground. You can't put power down without traction hence the larger wheels on sports cars.
bezaldo7 Having a larger wheel doesn't increase traction or increase the contact patch. Having a wider wheel does.
@@LeoLeanty The major reason for using a bigger wheel is that you can fit bigger brakes on the car and you cool them down more easily.
the 5252 rpm is desame as the small motor cycle sir?
Well Washington is only 10 minutes away... and legal. But I don't smoke haha - my lungs prefer health.
isn't number 4th equation is just the max acceleration of the 1st gear? pls someone confirm it to me
I'm lost. to be honest I'm a business student. Quick question. I am planning to purchase a jeep compass which has 180 HP. The acceleration from 0-100Km/h is 10s. I want to install a cold air intake system which claims to increase HP from 180 to 185HP. Will this improve acceleration?
obviously... yes... More HP gives better acceleration.. Not much though, you probably won't be able to feel any difference
Assuming constant acceleration no matter the speed seems A LOT simplified. The effect of 0,7g at 60mph (sorry about using metrics and rounded estimates) would be:
F=m*a=3000kg*0,7*9,81m/s^2=20601N
P=F*V=20601N*(100kmph/3,6)=572kW
Or about 780Hp
Your car just got a lot more powerful during the race
Bro that's the acceleration at 1st gear....
Hello!
I really love this channel! Have learned a lot.
There is one question I wanted to ask someone, who knows better about cars than me.
So - I swapped my differential to a shorter one. 2,79 to 3,36. It seems for me that the car is overall quicker, but I have mesured the time to get to 62mph (100kmh) and the time has increased.
Is there someone who could help me a bit with comparison? (I don't have the time now to calculate it, and honestly, I think that I will get the calculations wrong :D )
I want to know if it is my lack of skill, or it really is slower to get to 62mph with the shorter differential.
My engine is: M41D17 1.7 L (1665 cc/101 in3) 66 kW (90 hp) @ 4400 190 N·m (140 lb·ft) @ 2000
Redline - 4800
gear ratios
I 5.43 (15.15)
II 2.95 (8.23)
III 1.81 (5.05)
IV 1.26 (3.52)
V 1 (2.79)
Tyre radius 25"
Thank you a lot in advance!
mazaispiileens I've got to tell you that it is probably your driving, going from 2.79:1 to 3.36:1 should increase the acceleration. It is probably to do with your shifting, either you are used to shifting at specific mph so you aren't shifting up quickly enough now (because the peak power now comes at speeds lower than it used to) or possibly you have to make an extra shift (perhaps you used to hit 62 in 4th and now you hit it in 5th?). The second one would make a big difference. Even if you're causing the problem by not shifting at the right time that's no reflection on you though, you are just going to have to get used to the new shift points and try to break old habits.