blk~2000~Z28

Actually if you go back and read where this particular challenge "started" he said that given 2 car's torque curves w/o rpm scale he could determine the winner. I read your post and where you first asked him to give you an answer to this particular case (which is diff.) and in his response I got the impression he was thinking of the org. 2 car scenario.

I have to go with you that your case can not be done w/o rpm scale. I still am trying to determine if the "org. 2 car" scenario is possible as well but my brain is hurting

blk~2000~Z28

I think that you may have things backward here, unless you mean something different when you say imaginary. Torque can not be directly measured on an engine or wheels of a car. You can not go out to your car and measure how much torque the engine is producing or the wheels for that matter. But you can however calculate how much torque it is producing by doing the math/algebra/physics. Torque is only derived/measured by how much "work" an engine can do in a given time frame. when a dyno drum is spun to an rpm in a given time frame you calculate the torque or force required to make the "mass" move or "accelerate". Torque is not imaginary but Hp is . HP is a measure of work, that is not imaginary it is standard of measure. Just like ft/lbs is a standard of measure for torque. Both are real and both can be calculated or derived. But saying one is imaginary is not right because it is a given that a motor will do a certain amount of work over a given time thus we can derive its HP.


horse·pow·er ( P ) Pronunciation Key (hôrspour)
n. pl. horse·power
Abbr. hp A unit of power in the U.S. Customary System, equal to 745.7 watts or 33,000 foot-pounds per minute.
The power exerted by a horse in pulling.
Informal. Effective strength: political horsepower; computer horsepower.

Example:

My height 6' 2" or 74"
OR
(6*12")+2"=74"
OR
(12+12+12+12+12+12+2)"=74"
The latter 2 are imaginary becuase they were calculated

BigPlanTransAm

well, i read most of this thread but skipped page 3. anyway, i dont think anyone quite finished answering why a V8 would have less lag than a 4cyl. the reason a V8 would spool up a turbo (of ~= size) quicker is simply that it moves more exhaust at lower rpm and since it is exhaust that drives a turbocharger, more exhaust = faster spool. since there is more exhaust being moved at lower rpm the turbo will spool faster. now, if you put a bigger turbo on the V8 (a bigger turbo requires more exhaust to spool) it would take more time to spool. the fact is though it would take a much larger turbo on a V8 to have the same amount of spool time as a 4cyl which means more power and probably at a lower rpm which means you get into your powerband faster.
the only advantage i can see to having the high revving 4cyl is
1) it is probably somewhat lighter
2) you can run each gear to a higher mph - or - make up the tq difference with steeper gears and even then you may not regain all of the tq lost by having the smaller displacement.
as for the "calculating hp with torque and not rpm". i too do not think it is possible and though i could be wrong, i would be very surprised if if am.

ChrisB

There were 2 different challenges (which still come down to the same problem, you need rpm, and thus horsepower). The challenge I reiterated was the one that he claimed was "simple physics", so I was just hoping he could prove his claims.

Re: the 2 cars situation - I could stipulate 2 cars, one with an average flywheel torque of 400ft-lbs, the other of 800ft-lbs.

There is no way to see with will win without knowing the rpm (and stipulating an average torque output is the same as giving a curve, just easier. Just imagine a flat line).

If the 800ft-lbs was at an rpm that allowed an average of 2:1 gearing, then we would have 1600ft-lbs delievered. If the 400ft-lbs was at an average rpm that allowed 10:1 gearing we would have 40,000ft-lbs. On the other hand if the 400ft-lbs were at a 1:1 gearing we would only have 400ft-lbs, etc.

So as you can see average torque by itself will not tell you anything. If you look at it from this perspective you need to know rpm, to determine gear multiplication. And when you combine torque and rpm, you have a horsepower analogue.

Chris

25psi

I think all of you should read the latest edition of Hod Rod Magazine. It simply states the same thing I have been saying over and over again. It explains the advantages of having high rpm horsepower vs low end horsepower. Doug Deitweller(don't know how to spell his name), even suggested that it is best to have a linear power band(like 4cyl), opposed to a peak hp down low.

The reason why 4cyl enthusiasts tend not to look at torque figures, is one: They don't weigh as much. And two, torque is not a factor 80% of the time your flying down the quarter mile.

Let me ask you a question. If to opposing cars are doing a 40 punch, what would be the deciding factor? Torque or Horsepower!

ChrisB

That is BS - it doesn't matter where the horsepower is at - you simply select the approriate gearing to take advantage of the power.



Horsepower delivered - but if both make the same horsepower what difference does it make if you make it at 3000rpm or 6000rpm? If the area under the curve is the same for both than it is irrelevant. If one has a better area under the curve than that one will be faster.

That said, I would rather drive the car that made the power lower - since I don't spend most of the time driving at 6000rpm, but rather at 2000rpm, the car that makes more power there would be more fun to drive....

SuperTrooper

In all honesty, this is what it boils down too. Forget brand loyalty and all that domestic vs import BS. I love Muscle and you will never hear me say I'd take an import over a domestic. But in all fairness, somebody with a fat wallet can turn a 4 cyl, full interiored car into one hell of a street machine. Just drive what you like and **** the BS! I've been beaten by a couple of imports, but as somebody a couple quotes up....its far few and in between. Is it because it cost so damn much to make them worth a ****? I don't know. But none the less, I would have to agree. Every track day, all you see is one maybe 2 fast (streetable and full interiored ) imports...be it a supra, WRX, DSM, Honda. You hear about them all day long about beating this that and the other on the road....But the track is where its at! Buy what you want, but I will stick to my high reving low rpm torque making american V8!

SuperTrooper

Holy ****! But, can we say traction issues on the street?

Excal

this is still going?

I mean we could pull out "Joe blow's 9 second Caravan" and other bullshit like that but that's pretty much meaningless.

Obviously peaking at higher RPM is good (for a race application) and better than peakin at ******* 5000.

BUT it is better to have 300hp from 3000rpm to 6000rpm

than

to have 250hp at 6000rpm AND 350hp from 7000rpm to 8000rpm.

And as long as we pull hot rod Articles..how about the Hemi powered DOOR SLAMMER Corvette that broke the 5 second mark in AUS?

that thing barely got to 7k rpm if i remember, it had a Roots i believe. so that's obviously instant power.

Of course if u have FWD low end is not as usable. haveing low end grunt doesn't have to compromise top end performance..

the LS1 is the perfect engine to show case that.

DBR TSI

Oh yeah, he has some big *** slicks in the front and it even has wheelie bars in the back because of the power and he still spins through first and second. Pretty sick if you ask me.

ChrisB

Hey SS00Blue, it has been a few days now, still haven't heard back from you on this, it would be really great if you could demonstrate these "simple physics" for me? (i.e. 3000lb car making an average of 400ft-lbs of torque, estimated 1/4 mile time).

Or is it possible you were just full of crap? hmmmm....

SS00Blue

LOL!

Sir,
I have a family and a factory to which I must attend, though the recent worldly holiday has put others to rest in their homes. Believe it or not, my world is much larger than educating you.

The fact is that it should be painfully clear to you now (especially in light of the recent issue of HR- pg 42, second column, 3rd paragraph, 1st sentence; see also pg 44, upper and lower, right-hand pictures and text), I am correct on one point of our discussion. That is on my assertion that dynos do, in fact, measure torque, and using rpm data sampled, calculate horsepower. Horsepower is NOT directly observed.

On the latter issue, where I claim that I can create a formula that can approximate 1/4 mile runs, I still assert that I can provide a formula that is at least as accurate as the approximation given by the current hp-et formulas.

If one looks at the hp or tq curve, mass and gear changes alone, the formula for ET from either HP or TQ would be, at best, a complicated integral approximating average curve and their and plugging it into F=ma for acceleration, then solving for time. Remember, you assert that it cannot be done. I am saying that it is certainly doable, though it is not popular to guestimate et with peak tq, and frankly, I have neither the time, nor inclination to educate you (much less re-educate myself) on dynamics.

What I am trying to say, is that an approximate formula is out there, I am sure, but my time is limited, and so is my memory on the dynamics I took 17 years, ago.

So, Chris, I concede, therefore, that there is no possible way that an ET can be approximated by using a TQ curve. I can however tell much more about the performance of an engine from the tq curve.

Happy? I hope you enjoyed your weekend as much as I.

SC-

SScam68

iTrader: (20)

Yup, first thing they teach in dynamics. A lot of work though

Hey 25Psi, do you have any original thoughts about the formulas or example posted or are you going to keep coping and pasting from the internet?

25psi

I proved what I had to say 3-4 pages ago. Do you have anything to add?

ChrisB

Hmmm, according to you it was "Simple Physics" - now you concede it is impossible? So I was correct in the assertion that you were "full of it", at least with respect to that issue?



Again, just go to a dynojet, dyno your car without the rpm lead, and see what happens.

But what difference does it make if power is a "calculated value"? We are taking about which number is representative of the performance potential for a vehicle.

You have already conceded that you can not take a torque and weight value and determine the potential performance. On the other hand, you *can* take horsepower and weight, and from that determine a performance potential.

So doesn't it follow that power, is infact the best metric for determining a vehicles potential to accelerate, not torque (infact, the torque is irrelevant - it could be 100ft-lbs at 6000 rpm or 600ft-lbs at 1000rpm - either way the potential to accelerate is the same.

Which would be the argument.

ChrisB

Okay, tell me about the "performance" of these two engines - torque curves are below. RPM and HP are as of yet undefined, since you claim to be able to do it with torque only.

BigPlanTransAm

the top one is N/A and torque peaks ~5000rpm so i would say it makes about 440-460hp.
the bottom one is a poweradder so it is harder to tell.
i think he may be saying if he sees the torque curve he can approximate the rpm and calculate with that. thats what i did anyway. but i still think if you say a car makes xxx torque (avg or peak) ET cannot be determined because you have NO rpm data at all and the thing could rev to 5,000 or 50,000 for all we know

ChrisB

I agree 100%, and as you noted without an RPM value you can't determine anything. You can't really even estimate RPM as I haven't put any values on there - the scaling could be logarithmic on the second one, so it actually has a "broader" torque curve, etc.

Whatever conclusions are drawn, the rpm values can be set to invalidate that conclusion - which just goes to further illustrate that power is the best metric for performance.

Louis

iTrader: (7)

It depends on what turbo the GSX has.

I was looking at a few for an all around, fun, winter car.

I have a few friends in the NABR board- one has a 91 GSX, with a Green, front mount, and a nicely built 9:1 motor. Its fast. Sure it doesnt spool till 4k, but that doesnt matter when redline is 8500!

The other has an FP 3052, and a few other odds n ends, fast is an understatement.

They are unique cars, to each their own.

BigPlanTransAm

the only reason i said what i did about the top one was because it looks like N/A torque curves generally do and since we all know that hp and torque meet at 5252 then the torque should peak a little before that but, that could be a progressive controlled nitrous shot which would throw my theroy out the window.
one last thing: was i close with my guesstimation?