[Josh49]

Looks like you still haven't understood my situation.
Car A: 200 hp at Peak HP RPM, 170 ftlb of torque at Peak Torque RPM, NA
Car B: 200 hp at Peak HP RPM, 230 ftlb of torque at Peak Torque RPM, Turbo

I stated AT PEAK HP RPM, both engines are producing 200 HP. Read what I wrote.

[Josh49]

It seemed to me that the OP was looking for a way to look at car specs, "Car XY has xxx hp and xxx torque" and "Car XZ has xxx hp and xxx torque" and decide which car was faster. That is why I got into the discussion I did about why it is necessary to look at the numerical values for Torque and HP, and not just HP. I thought the OP was trying to look just at the peak values of hp and compare one car to another. Not the entire hp map.

[teknochild]

i dont care, where putting this to rest right here, answer my question dont dodge it

Originally Posted by Josh49

I think many people are missing the fact that an engine develops peak Torque and peak HP at different RPM's. Peak Torque is usually generated in the lower RPM band while Peak HP is usually generated in the high RPM band. An engine does not constantly put out 215 hp or 185 ftlbs of torque for instance. These are numbers specific to an exact RPM* for that engine.

fine ill kill you using your own statment, where is a car accelerating the fastest, while torque is increasing up to peak torque or between peak torque and peak horsepower where torque is decreasing and horsepower is increasing?


i have even made a cute little multiple choice question out of it using one of shivs dynos, since you know claim to know exactly how HP and tq effect acceleration order these from lowest to highest acceleration, i can do it, can you?

[teknochild]

Originally Posted by Josh49

It seemed to me that the OP was looking for a way to look at car specs, "Car XY has xxx hp and xxx torque" and "Car XZ has xxx hp and xxx torque" and decide which car was faster. That is why I got into the discussion I did about why it is necessary to look at the numerical values for Torque and HP, and not just HP. I thought the OP was trying to look just at the peak values of hp and compare one car to another. Not the entire hp map.

he never said or meant that, you assumed that

Originally Posted by Teknochild

if a car has more horsepower at any point vs a car with lower horsepower and more torque, at that point the car with more horsepower will have higher acceleration, this is whats meant by "horsepower is acceleration"

also please answer this

Originally Posted by Teknochild

furthermore "Rotational, Sum of all moments (torques) = moment of inertia x angular acceleration." out of curiosity how would you calculate the "sum of all moments"? yea thats what i thought, do u get it yet?

[Josh49]

Very easy.

Let's look at it linearly. To say F=ma is wrong. To be complete, I wrote ΣF = ma. I could put a 50 lb force on a wall, and the wall is not going to accelerate. That is because the wall is pushing against my hand with an equal and opposite force to my hand. The resultant force vector is zero, therefore the acceleration of the wall is zero.

Rotationally it works exactly the same. Opposite forces come in the form of friction. I used the summation in the equation to be complete.

[teknochild]

no answer the muliple choice question, quit dodging it because you know it proves we are right

[vladinecko]

very interesting discussion.

in short though, couldn't we say that acceleration depends on HP and TQ equally? we all know their peaks on the RPM range are at completely different points (TQ lower, HP higher). however, in very simple terms, we achieve the greatest acceleration when as much torque is applied as often as possible (HP). this would mean that engines whose average TQ and HP across all RPMs is the greatest have the higher acceleration, which would support my argument that both TQ and HP are equally important in the measurement of acceleration.

or not?

[Josh49]

Originally Posted by teknochild

he never said or meant that, you assumed that

Then I guess this is the mistake I made. I assumed he was talking about peaks.

[teknochild]

Originally Posted by vladinecko

very interesting discussion.

in short though, couldn't we say that acceleration depends on HP and TQ equally? we all know their peaks on the RPM range are at completely different points (TQ lower, HP higher). however, in very simple terms, we achieve the greatest acceleration when as much torque is applied as often as possible (HP). this would mean that engines whose average TQ and HP across all RPMs is the greatest has the higher acceleration, which would support my argument that both TQ and HP are equally important in the measurement of acceleration.

or not?

yes and no, you are right in everything you said. but remember that horsepower IS torque just with consideration of how often its applied, so you can and should, totally forget about torque when looking at horsepower

or to bring back soemthing i said before, you can determine which engine is faster by just having the hp on a dyno, once you have the HP numbers you can forget the torque numbers (since horsepower includes torque, but has more information (rpms) mixed in it as well)

"we achieve the greatest acceleration when as much torque is applied as often as possible (HP)" and this is exactly right which is what im currently trying to pound into joshes head

[teknochild]

Originally Posted by Josh49

Then I guess this is the mistake I made. I assumed he was talking about peaks.

avoided the multiple choice question again, come on, you can do it, just swallow your pride and answer it

[2007/335i/coupe]

lol, this is great! It's like asking someone if the sky is blue or red and he keeps on saying, well what shade of color are you talking about

[teknochild]

fuck it ill answer it myself, in order from greatest acceleration to lowest (assume E is flat after the peak or things get sketchy) EACDB, which goes from the highest HP output to the lowest, and surprisingly goes from the lowest torque output to the highest


and another nice statment, torque alone CANNOT tell you the acceleration of a car


and 2007 was that refering to me or josh?

[2007/335i/coupe]

tekno, it was directed at Josh since you were asking the question. I always find it amusing when people ask questions and others constant dodge it somehow. I will admit, some folks do it so well you never even notice it and think they actually answered your question, however josh doesn't have this skill yet No hard feelings Josh, I found this thread useful and gained additional insight from everyone contributing.

[Josh49]

I acknowledged that I made a wrong assumption, that the OP was interested in peak HP and peak torque numbers only.

I was not arguing the points brought up later in this discussion.

I am done in this thread. Thank you.

[teknochild]

fair enough, i actually read over that article again with the intent of determining if he was infact talking about peak numbers or not, and i admit it doesnt really specify either way, he said hes going to re write it though

[SapphireBlackG01]

Originally Posted by bavarian19

No offense, but you seem to be out of your league...

Isn't that just a bit pompous to suggest, given that you teach this crap to fourteen year-olds?

[SapphireBlackG01]

Originally Posted by danielrm26

If you don't know that 5252 is an intrinsically meaningful number in the equation then you probably shouldn't be asking questions with such attitude in your voice. Not only did you not know the answer, but it was right in the article that you are attacking.

""Below 5252 RPMs any engine's torque will always be higher than its horsepower, and above 5252 RPMs any engine's horsepower will always be higher than its torque. At 5252 RPMs the horsepower and torque will be exactly the same." -- revsearch.com"

As for the torque constant issue, the constant torque is used to illustrate the numbers. The fact that this varies a bit over the band doesn't matter much.

pwn.

[Top_Gear]

teknochild:

You are missing a simple but important point: ACCELERATION is a variable quantity just like speed is (albeit to a lesser extent). It changes with time and it's not constant -just like torque is not constant across the RPM band. Now if torque was constant across RPM so would the car's ACCELERATION over the amount of time the driver stays on the same gear. Once the gear shift occurs, torque drops lower and so does the car's acceleration.

Acceleration is NOT proportional to RPM, only to TORQUE. Don't be confused about that, physics tells us so. The bigger the torque the higher the acceleration. There is a catch however, as someone else said in this thread already, when the car manufacturers quote the TORQUE rating of their engines they only quote the largest value of the torque over the RPM range. The quoted torque is ONLY available at a SINGLE RPM (at a single instant in time) and is lower at all other speeds (or times)! A better measure of vehicle performance would be the AVERAGE torque at the wheels (not at the crank) divided by the weight of the car.

One more thing: The HP-RPM curve can be derived from the TORQUE-RPM curve so the HP curve is not independent! All you need is EITHER the HP-RPM or the TORQUE-RPM curve to know the performance of your engine. But the manufacturers don't provide either of these curves (which can be obtained from an engine dyno) opting instead to give us only two numbers: the max TORQUE and max HP which usually occur at two different RPMs (which they quote as well).

I hope this helps.

[BMW0]

Here's some good sources for your Torque and Horsepower definitions:

http://en.wikipedia.org/wiki/Torque

http://en.wikipedia.org/wiki/Horsepower

[Top_Gear]

Originally Posted by BMW0

Here's some good sources for your Torque and Horsepower definitions:

http://en.wikipedia.org/wiki/Torque

http://en.wikipedia.org/wiki/Horsepower

There is a lot of physics mumbo jumbo in these links that take the reader off topic. However, one of the referenced articles shows an excellent example comparing two different cars with identical peak horsepower. Take a read of the bottom half of the article in this link titled "A Complex Example"

http://craig.backfire.ca/pages/autos/horsepower

The example is really not that complex but requires a bit of patience when reading it. It describes two different cars called "ricer" and "redneck". The "rednceck" car has big torque but small rpm range (small redline) and the "ricer" car has small torque but huge rpm range (huge redline). The author goes on to show how the selection of proper gearing can make the performance of these two cars nearly identical.

It's a great read. If you can unserstand this one example you pretty much have understood the concepts of torque-power-gearing.

[teknochild]

Originally Posted by Top_Gear

teknochild:

You are missing a simple but important point: ACCELERATION is a variable quantity just like speed is (albeit to a lesser extent). It changes with time and it's not constant -just like torque is not constant across the RPM band. Now if torque was constant across RPM so would the car's ACCELERATION over the amount of time the driver stays on the same gear. Once the gear shift occurs, torque drops lower and so does the car's acceleration.

NO your an idiot, how are you going to tell people that acceleration is the same if the 335 exerts 300 pounds of torque on the wheels 1000 times a minute as 3000 times a minute

ive already explained in detail, and you are an idiot

Originally Posted by Top_Gear

Acceleration is NOT proportional to RPM, only to TORQUE.

your right, its proportional to torque and RPM, WHICH IS HORSEPOWER YOU SINGLE CELL IDIOT

Originally Posted by Top_Gear

One more thing: The HP-RPM curve can be derived from the TORQUE-RPM curve so the HP curve is not independent! All you need is EITHER the HP-RPM or the TORQUE-RPM curve to know the performance of your engine. But the manufacturers don't provide either of these curves (which can be obtained from an engine dyno) opting instead to give us only two numbers: the max TORQUE and max HP which usually occur at two different RPMs (which they quote as well).

I hope this helps.

your right 100%





just go back to that dyno i posted and rate the letters in order of acceleration, go on, (hint i already provided the answers)

by your reasoning it would be best for the 335 owners to shift between 2-4k rpms to go as fast as possible... and anyone that owns the 335 (or any car for that matter) knows thats not true

so again i say YOU KNOW NOTHING ABOUT CAR ENGINES STOP SPREADING YOUR HORRIBLE INFORMATION



here ill put it in here since i doubt your brain can handle drooling all over your keyboard and scrolling up at the same time

rank them in order of acceleration, go on, DB and C all have more torque than A and E so by your retarded reasoning your car is accelerating the fastest at those engine speeds

go on and actually try and tell me that acceleration is highest at D, B and C, this way everyone else can share in calling you a total idiot with me

[Top_Gear]

I see, you are obviously a confused teenager that dropped out of highschool. I am sorry I replied to your post.

My suggestion is you shouldn't worry about these issues, they require a bit more patience and maturity than you have. The good news is that you are still young and I am sure your behavior can only improve from here on.

Have a happy new year and best of luck to you.