For a given vehicle the F1 engine will always be faster than the Cat engine because the F1 engine is more powerful.

 

I can do that. Gimme some time to draw the pic.

As for comments on your example anything in particular? The example's differences or merely which one will make the fastest car and why?

 

I suspected it might illustrate your point, despite both curves going to 8k.

 

Ok, Ill put it this way.

Take a motor. ANY MOTOR. Make it make... oh, 50 more foot lbs. Guess what? If theres more TORQUE at that rpm theres more POWER too.

Damn people readin way too much into a little quip of mine.

DamonB -

Same thing! Take any 8000 rpm motor. Put on a blower or something (whipple?) so the torque curve is pushed up x footpounds all over. Theres more POWER as well.

I SHOULD have said "all else being equal you cant make more torque without more power UNLESS You do it at uselessly low rpms for a car, but at good rpms fo say a tractor, boat, airplane, bla bla bla".

I am glad that you understand the whole concept of rate and time though, it seems everyone else is having trouble getting that. I sure did for a long time myself, and I agree completely with what you said.

 

the thread wins the award for most rotarded thread ever.

 

provided that the 8000rpm motor has gearin that will get the motor into those higher rpms. if the gearing aint there, the 5000rpm motor will win

 

I'm not getting involved because I admit I don't have the mechanical or even theoretical knowledge that some of you guys do. And I also think many of the arguments about this type of stuff is just for the sake of arguing, with no practical application in the first place. Take your statement here:
This statement is not true. Take the fastest F1 engine you can find and drop it into a Freightliner hauling a 30 ton crane.

The question is: Will it even move before the clutch burns out?
The answer is: Nope.

 

I'm a little late to this one. Haven't been on the forum for a while, but this is always an interesting discussion.

Yes, I agree. To the layperson who doesn't know anything about cars and is likely to buy a Ford or GM product, big torque numbers that make the car feel much faster than it actually is are a good thing.

I'm sorry, but I have no idea what you mean by "asymptote of acceleration over different road speeds." Do you know what an asymptote is? It's a limit, a value to which a function approaches but never reaches. To me, some sort of theoretical number, regardless of whether or not you can actually argue it to have relevance, that an engine will never reach is completely pointless and nonsensical.

It is about power band, and that is what DamonB is arguing. POWER involves the time dimension, which is the critical difference between it and torque.

Sigh... this coming from the guy who totally does NOT understand what constitutes a "peaky" power band. More off the line power, yes. What most people fail to understand is that turbos add TORQUE. The boost you feel from a turbo is a torque surge, and so if you fault a turbocharged engine for it's power band, there is likely a turbo to partly blame in that equation.

The fact of the matter is, you can't argue a turbo 13b versus an LS1 without defining the turbo setup.

Yes, it's kind of stupid to talk about in general terms, but that is because they are intrinsically related. Power band, gearing, and feasability are great real-world things but what some people don't seem to understand is that power band can exist without gobs of torque in different rpm spectrums, and appropriate gearing will help facillitate that. Perhaps I'm not giving you enough credit and you are in fact arguing the exact point I am.

Ooops, nope, you sure aren't. "Bigger" powerbands? Come on! What you really mean is LOWER powerbands. The problem with your argument is that many Honda engines can pull hard from 5k up to redline, which is typically above 7000 rpm. Now seeing as how we've all decided to concentrate on real world conditions and all, the real world sees Honda engines in Honda cars, which are typically much lighter than the pig vehicles that usually house V8's (I'm speaking stock vehicles, not the awesome swaps people have done with the LS1 in an RX-7). These cars are perfectly suited to that higher rpm power.

But the point is, a typical Honda powerband is at least 2000 rpm. They continue to pull (an idea that many V8 heads seem not to grasp, as they feel Honda engines to be "peaky") well towards their redlines, making their powerbands quite large. 2000 rpm is indeed a large band, because not very many transmissions I've ever experienced will place an engine 2000 rpm lower shifting into the next highest gear. I mean, we ARE talking realistically here, right?

To be honest, one of the things I've always felt lacking in the traditional Amercian V8 is how the torque drops off dramatically as the revs increase, so WHERE the power lies is naturally a matter of choice.

Right, but you're talking at one specific point. A 6.0L V8 will have more torque at 3000 rpm than a 2.0L Honda, DUH. But what about at 8000 rpm? The Honda will have more torque, and thus more power. The Honda is suited to making power at high rpms, the LS1 at lower. You are arguing two points ambiguously and trying to justify one with the other, when really they are unrelated.

You cannot argue torque versus horsepower without taking rpms into account. Otherwise, we're both just assuming a crapload of information and the argument is all baseless.

Yes, but read above. I believe the typical argument comes down to "down-low torque" versus "screaming rpm power." At least that's what I thought this was about. What is more effective, making more low-end torque or more high-end power? Naturally if you raise torque, you raise power at a given rpm. The same is true in reverse: We give that engine an extra 100 hp, guess what? It makes more torque. Problem is, you can't even calculate the torque without the time aspect.

I think what you're missing is that the power increase is what makes the car faster. Yes, it makes more torque. It also makes more power. Ultimately, the power matters more. The two are intrinsically related, as I stated before. If you're going to dwell on one, it should be the power.

I read this and I question whether you are arguing for or against the power side of the argument. I can't tell at this point, since I'm about three sheets to the wind. However, I will say that DamonB has had the most clear, concise argument in this discussion and I agree with what he says. Without further making myself look like an ***, I will bow out of this discussion for now.

 

I do think the critical thing that most people overlook when dismissing Honda engines are their ability to produce torque high in the rev band. This is their whole strength, and a lot of people do not give Honda the credit for it that they deserve, because they don't see the usefulness in it. This is also why the Renesis is as good as it is.

 

rarson you said so much that its impossible to address it all (no way am I gonna quote that up into chunks) so Ill try to make my points here.

"powerband" to me is a function of what band of rpms over the entire revrange of the motor does it have near peak power. Obviously, motors that excel at that are motors with small turbos and large displacement low revving ones... especially both, or the likes of a diesel.

A honda doesnt have a big powerband at all... if you look at a graph the near-peak horsepower figures are in a very small band. THAT is what we mean by a peaky powerband. Yes, it pulls the whole way to redline, as it has a nearly constnat torque line, but the POWERBAND is weak becuase its not MAKING max power throughout the acceleration in each gear for very long.

Also, when I mean if torque or power goes up, the other one does too, is becuase at any rpm, if you add more of either at one rpm point both go up. Duh. Everyone took taht WAY long.

Also Im FOR THE POWER SIDE OF THE ARGUEMENT.... which is why I make a big deal about POWER BANDS.

Assuming constant power, the acceleration of a car will be higher the slower it is, and the acceleration will taper as speed increases until it stops completely due to drag. Thats the most you can hope for from a v8 motor, basically. Big powerbands (descending torque slope on a graph) and gears that stay within that past 1st gear will match that the best, and thats the point Im making.

To maintain a steady rate of acceleration, power must constantly go up. However, if you look at a car that has power increase as it is in every gear vs one that has constant power in each gear (past 1st of course) uh.. guess what? Constant at 400 (for example) vs 350 up to 400 (for another) the constantly at 400 hp car will be faster, but will be decelerating in each gear! The 350-400 car will be pulling the same or even harder and harder as it reaches redline but wont be as fast, Why?

The constantly 400 hp car will pull harder from the get-go and will pull jsut as hard as the latter one will ever pull at the end of the gear.

This is the *RATE* thing people seem to overlook.

But yeah, Im all for the power side of the equation... and a 3-5K powerband is bigger than a 4-6K powerband, because one represents half of the engines rpm range, the other, a third.

Get my points yet?

 

Right, but what you're missing is that you're just looking at a picture. In reality, the rate of acceleration for the Honda curve will maintain a high number, while the V8 who's torque drops off will continue to decrease it's rate of acceleration. Now I'm not trying to argue that the Honda is better than the V8, I'm simply explaining why it's not peaky.

See the thing is, to maintain a rate of acceleration as rpms increase, power has to increase, so with the "peaky" Honda you're getting a much more consistent rate of acceleration.

Right, but why would you want to assume constant power? When you mod a V8 heavily, you're still shifting the power band higher. With a Honda, you start off from the get-go with that ability to hold torque. With the V8, when you mod it, you are only doing the same thing, helping it make and hold torque higher. The V8 just starts off with a lot more torque so that it doesn't have to rev as high. And that torque dropping off makes the car less fun to drive, IMO, than the alternative. The Honda is more linear than the V8.

Gearing is a rather random variable, since most of the time it is selected appropriately by the manufacturer. The point I was making was that the Honda powerband of 2000 rpm would be sufficient to gear shifts placing the next higher gear back into the power band.

You're twisting the argument around to argue down-low torque versus high-rpm power. Of course the rate of acceleration for a car that makes 400hp versus a car that makes 350 hp, at a given rpm point, will be faster. I don't understand why you're arguing these numbers (400 -> 400 versus 350 -> 400) when they're not very realistic concerning Hondas versus V8 cars. For one thing, the Honda will weigh a lot less and as such, the 350 hp car could very well be much faster than the 400 hp car. Let's not even get into the traction issue (if that power can't be put to the ground, it's useless).

Also, you said "the constantly at 400 hp car will be faster, but will be decelerating in each gear!" Uhhh, no it won't. If it's moving forward at WOT, it certainly won't be decelerating. I think what you meant was that it's rate of change of acceleration would be negative.

Regarding that picture on that piece of paper, sure. But what you're forgetting is the real world application, with gearing. That effectively renders a power band as a torque plateau over a given rpm range. The size of the range is the same, 2000 rpm. If that torque is able to be produced at higher rpms, then the engine can do more work, and so it is making more power. If the torque values of your two power bands are the same, obviously the one with the higher rpm band will be faster.

This argument is pretty convoluted, but I don't think there will ever be a definitive answer to the "torque versus horsepower" arguments. The fact of the matter is that torque only matters when time is involved, and when that is the case, then you are actually talking about horsepower. The two are constantly intertwined.

 

constant power as it accelereates will have a decreasing rate of acceleration. Aka DE-JERKING, but most people have trouble with rate at all, let alone the 3rd power.

Regardless, Ive explained it, Im not gonna do it again, either accept it or not.

 

You know guys, they make race tracks where we can all get together and test these theories at.........

Point being, V8 cars have a low trap speed for their ET compared to small displacement turbo cars and especially small displacement high revving uber tuned na cars. This illustrates the benefit of higher midrange torque with less top end power (which typically correlates with trap speed): same performance when the rubber hits the road for less peak power. Or in the case of the V8 swap crowd, lower ET *cough*more total acceleration integrated over 1320ft.*cough* and a more badass car in general for the same peak HP.

Calculus evades some, but when the green flag drops, the BS stops.

 

Actually, my experience has been that the V8 cars have usually had higher traps than my Eclipse. But I have a really strong midrange pull since my turbo is very small. I usually shift at around 7400 rpm since the power does start to drop off at about 7000 or so.

What it is though is that I can just get out of the hole faster, usually. My car has less power but rips out of the hole, so I really lose the mph at the top end. But yeah, I mean comparing cars like that is really dependent on the total setup, drivetrain, etc.

I don't know what you mean by "de-jerking." I understand decreasing rate of acceleration, I had 3 calculus classes in high school and college. Calculus is easy for me to understand, but when you attempt to put it in such simplistic and ambiguous terms, I can't make sense of what you're saying.

It's much simpler to look at velocity and acceleration in terms of derivatives. Take the acceleration and graph the derivative of it. Any points on that where acceleration is decreasing the derivative will be negative. The problem is that when most people hear "acceleration is decreasing" they are not comprehending the concept of the derivative. They assume that decreasing acceleration means deceleration, when it doesn't (not necessarily).

By the way, that is what acceleration is: the derivative of velocity.

 

So, then the all-motor V8's in drag racing producing over 1,500hp are peaky? You better let these guys know that they are spinning way too high of RPMs to do them any good, and should really put in a smaller cam to get a "broader" powerband out of them. You do realize it is possible to have a peak torque at more than just ONE rpm point? This is the hard part when building engines. Trying to let it carry peak torque, aka peak VE for a wide range of rpms. Before V-tec and variable lift, a cam only worked in a "narrow" range of rpms, thus making it a low rpm cam, or a high rpm cam ect. The ultimate engine is not a electric motor, and is not a constantly decreasing torque. ANY engine will be more powerful and less "peaky" if can hold its peak torque from very low rpms to insane rpms, period.

 

Yeah, that's the point I was trying to make. That's the nice thing about Honda engines, even though they don't make tons of torque (though they do make respectable numbers for their size), they can hold it for a long time, making the powerband pretty broad, and making a lot of power for what little torque they do have.

The newer K-series Honda engines though are a LOT more torquey than the old B-series. They can still produce the same kind of torque curves so some of these engines are really making lots of power (there are a lot of 11-second street-driven swaps popping up).

 

There are some (I thought) understood assumptions. The first is that transmissions (gears) serve the engine, they do not serve the chassis. That means if we did something truly radical like swap the Cat engine for an F1 engine we'd of course swap trans and rear end ratios as well in order to match engine RPM to the working speed of the mechanism.

There's no doubt an Olympic sprinter can beat me in the 100 yard dash. I could force the sprinter to run with his shoelaces tied together and then I'd whup his ***, but that's not a fair nor real comparison of our relative abilities.

 

Exactly.

 

i have a photo of a cummins motor in one of those top fuel looking cars (not actually a top fuel) that im pretty sure the motor is stock, running 8s

 

Jerk is the 3rd order... aka the rate of change of acceleration. http://en.wikipedia.org/wiki/Jerk

Notice how flat power = negative slope of the torque line? Right...

 

Constant acceleration is not constant power, constant acceleration is increasing power! Constant power = rate of acceleration goes down as speed goes up. Notice how you accelerate less in overdrive than you do in first?

Obviously, more power = more faster, DUHR, the illustration I was TRYING to make was if two cars have equal peak power figures, one of which had it for a wide plateau (many turbo cars, many v8s, the powerband you yourself described as not 'fun') of POWER vs one that had flat TORQUE and thus a peakier powerband.

You're talking about making more power by making the same or more torque at higher rpms. Nobody is disputing that fact, however, that increases the power so youre increasing average power per gear of the car.

Ugh.

Oh, and just so everyone can see this neatly...

A flat torque curved motor with a 'powerband' (pick an import motor, bla bla bla) vs a motor that has peak power at every single rpm... which one will be faster?

Hrm.... I dunno.

You tell me, assuming proper transmissions/gears are used in both cars, which will be faster, hrm? A X hp motor with a S2000's powerband or a X hp motor with a diesel motors powerband?

 

Nihilanthic, we already know that constant acceleration requires increasing power. We all understand the concepts of acceleration and flat torque curves. You're repeating yourself.

You're describing a car with constant acceleration as "peaky." Whereas, I feel a car whose acceleration peaks and then drops off is, by definition... ummm, well what else would you call it besides peaky? As I said before, sure the power graph, the nice paper picture, rises in a linear fashion to a "peak," but that's on paper. The power produces constant acceleration, the very opposite of what I consider "peaky."

 

Constant acceleration is not peaky in terms of acceleration, but the POWERBAND is peaky becuase the POWERBAND is not BROAD.

Im referring to the power band itself, not to the curve of acceleration.

The entire point of this thread is a car that makes 400 hp for half of its rpm range will out acclerate a car with 400 hp and the same weight and same gearing same tire sizes and same wind speed and direction that doesnt have as much midrange torque and thus only makes 400 hp for less than half of its powerband becuase its... not making it for as much of the rpm range.

Then again I guess this is a way to have a faster car with the same amount of power, huh. Regardless, now we're just splitting hairs :/

 

say you make an engine with an incredible torque curve. it makes an even 500 ft/lbs from 2000 to 5000rpm. go test it out. go into you 1:1 gear and cruise at 2000rpm. floor it. whats going to happen. your going to take off, accelerating at the same rate from 2000 to 5000rpm correct? the feeling at 2k will be same as at 5k, correct?

but at 2k your making 190 hp.
by 5k you making around 475hp.

if anything by 5k you will be pulling slightly less due to wind. certainly not much faster as the hp would make you believe. i think its pretty obvious. according to the hp guys, you will be putting down over twice the power at the higher rpms. do you really think that the car will accelerate any faster? it wont.

 

FLAT POWER NOT FLAT TORQUE DOOFUS

I also made it clear constant rate of acceleration = increasing power.

The REAL advantage of a huge power curve (and thus real high torque in the midrange) is that you can use longer gears and accelerate just as hard as with shorter ones... why?

Flat power = less torque at higher rpms.

And if you still dont get it realize this - if you know the power the engine is making, the rate of acceleration is dependant on road speed. If all you know is torque, then you hav eto know rpm and gearing and tire size.

I still dont understand why people can't comprehend this, but then again I guess I just get it easier.