mark kibort

Big torque viper vs little torque porsche

who has the advantage?? anywhere? anytime???

assume same weight cars and same gear spacing

have fun

Mark

Imo000

This is getting OLD! Too many variables and too little patience to care!

GlenL

Mark,

Stick the data into BenchRace.xls and you tell us. That was the whole point of that excersize.

bcdavis

Stick them on a drag-strip, and see who wins...

Again one has to take into account proper shifting, to stay in the power range, etc...

I know a couple guys with motorcycles.
One of them has a Ducati, which is all about the low-midrange torque.
The other guy has a 2-stroke dirt bike, that is street legal.
The 2 stroke has a *very* limited powerband, in the high-rpm range.

The guy with the 2 stroke often beats the guy with the Ducati, off the line,
where torque should be dominant. Maybe it has to do with weight, but
you really can't make these kind of comparisons. It all has to do with
weight, shifting, etc... The Porsche and Viper have different transmissions,
different weight, etc... If you really want to prove this point, you will
have to do it with two engines, swapped into the exact same car,
with the same driver, same weight, same transmission, etc...

Otherwise this debate is just an exercise in futility.

blau928

"Big torque viper vs little torque porsche who has the advantage?? anywhere? anytime??? assum same weight cars and same gear spacing have fun - Mark"

It depends on who is driving, the weather, tires, road conditions, experience and a few other things...! The HP/TQ curve can't tell you that.....!!

Ha...!

FlyingDog

Which has the better time at the 'Ring? That one wins.

mspiegle

I have a dream...
that someday, all 928s will have forced induction, or high-output strokers (or a combination of the 2?) and then it'll be the vipers that run and hide.

mark kibort

Then this should be interesting. I know this stuff is getting old, but it really makes the point. HP is what you need to look at!

In these two different set of HP/torque curves, they are more similar than you can see at first glance.
Actually, if you plot the hp curves on top of one another, they are almost identical, all the way to the bottom rpms use at any shift point. a closer gear set, just improves things for the porsche, but as long as the gear spacing is the same, the cars will accelerate the same. This is true, even though there is a dramatic difference in the Torque curve. Heck, one car has 450ftlbs and the other near 260ft-lbs!!!! But, thats really none of the story.

pick a speed, any speed. if the HP curves overlay on eachother and are close to equal, the cars will accelerate the same. why, as we just figured out, its the HP over the usable range. (area under the HP curve, average HP , etc) that determines TORQUE to the wheels.

so, say you have a viper that runs to 6000rpm. (this graph only goes to 5500 as it is at near max hp, but draw it out to 6000 and probably 400hp as thats the shape of most viper's HP curve. now, put the max rpm of the porsche of 8800rpm right at 6000rpm and then plot the porsche curve on the viper curve. you cand see that both curves are near identical . the viper shifts at 6000rpm down to 4500rpm, the porsche shifts from 8800rpm to 6800rpm. they both end up at the same HP, so the torque at the rear wheels is the same through the gear box!!

of course we have to say, same gear box proportions, and all other factors such as weight, drag, etc. however, even though these two cars have slightly different HP, the porsche makes up for it by using closer gears, and if the hp is even higher for the viper, then weight is used to equal things out.

In Speed World Challenge, a 415rwhp porsche at 2900lbs will have the same power to weight over a speed range as a 475rwhp viper at its heavier weight of 3200lbs . AND at no speed, does the viper have any "advantage" of torque to the driven wheels. Why, repeat after me. " HP is equivilant to torque through the gears at any speed." and that was the purpose of the previous exercise.

This is the fundamental error many in the motorsports profession make in talking about racing.

Mk

Herr-Kuhn

And I can assure you that the above is in the works!

IcemanG17

MK
Of course many of us have not had the pleasure of open wheel racing & are limited to a street driving experience....which of course is vastly different than real racing......Sure HP wins the battle...but torque is the fun stuff that slams you back in the seat! I guess thats why american drivers love old school V8's...lots of torque down low? Vipers are very fun to drive....horrible cars to live with on the street...but damm are they quick! Its amazing how easy 450hp 490torque can melt 335 tires!!

BTW my co-worker is selling his 98 GTS with 11K miles!

GlenL

So Mark,

We've got three values here: torque (ft*lbs), power (hp) and angular velocity (rpm). These are related by a simple equation:

hp = torque * rpm / 5250
or
torque = hp * 5250 / rpm
or even
rpm = hp * 5250 / torque

There's no magic here; it's just algebra. If you have two values, then the third is obvious. That is, syaing "torque and RPM" or "hp at RPM" is fully defining the situation. As it's torque on the axle that's important, having torque at the rpm gives the final result a bit easier that using hp.

Your last post was an example designed to be easy to use HP to analyze. Fine. It doesn't prove a "horsepower uber alles" theory.

Now in this one I'm not sure what you're getting at. The second graph doesn't even show a torque curve.

Here's an example to try: A flat torque curve that gives peaky HP or a broad HP curve with a declining torque curve (like the 4.5 chart showed). Which is better? Here's a hint: it depends on what you want.

And one more thing: Torque is much more interesting for analyzing engine performance. Why? Because the multiplication by rpm (above) that gives hp obscures the data. Look at an S4 graph with a working flappy. That's really clear in torque. Look at that 4.5 graph. The volumetirc efficiency is collapsing over half the range. This is why people talk about torque: it shows the engine performace charateristics more clearly. That maintaining, or achieving, high torque at higher RPMs is good is part of basic understanding.

mark kibort

Yes, the last post was easier to determine shift points. But, it does help in other areas. HP is everything. (it includes torque and rpm together) again, if you look at torque, you then need to look at gear ratios to understand the total torque at any speed. AND you need that to understand which car will be faster than another.

The second graph doesnt show a torque curve, but thats easy to fix. as you said, HP = torque x rpm/5250 or Torque = HP/5250 x RPM right????

So " what you want" is the most HP under the curve. you want to be "thrown in your seat" you want the most HP possible at any speed.

Ive shown below, what the torque curves of a Viper vs a GT3RS look like on top of each other. Clearly, you can see all that MASSIVE torque of a viper, down low , up top, it doesnt matter. Ironically, the porsche would have more torque net, to the driven wheels at lower rpms after a shift. there is no "low end Grunt" of a viper found here!

as far as your flappy comment. i have done the dyno with and without the flappy. Ive posted it as well. the HP dips in the same area, to the same degree, etc. as far as looking at torque in a micro analyical area, yes, Its like zooming in on a problem.... I agree. but that happens more rarely, than what most people look for when looking at torque. Just look at these two graphs. see performance differences by just looking at torque??? remember the shift point discussion? HP doesnt mask anything. it shows everything!

Keep in mind after checking the curves out below, the viper had 475ft-lbs torque and 451HP, while the porsche curves i found from GT3 showed only 438ftlbs, and 250ish on the torque. If i showed you the two torque curves of a 911 vs a viper, you would never be able to know which put more torque to the wheels at any speed. (assuming same gear ratio spacing). also keep in mind, the GT3RS has a .8 rpm drop for each gear, while the Viper is close to the 928 at .75ish. remember our exercise ?? area under the HP curve!!!!!

acceleration = Power/ (mass x velocity)

Mark

PS: as far as gearing:
max speed in each gear for viper vs GT3cup
Viper --- porsche
1st 57 --- 53
2nd 85 --- 78
3rd 116 --- 96
4th 151 --- 119
5th 201 --- 144MPH

so, besides the GT3 having 2 more gears between 85 and 150mph, at any speed , the GT3 will have at least, if not more torque, through the gears, to the driven wheels.

mark kibort

So Glen,

here is the hp vs torque curve from the flappy being held open vs closed.

i dont know about you , but looking a those curves, i see the same differences in both curves, but then again, why wouldnt you!

fortunately for me, i never race my car ever touching an rpm below 3700, so im good with it being stuck open. i really wouldnt have known the magnatude that it helped or hurted, without looking at and comparing the HP curves. because the HP curve gives the proper "weights" to the curve, it is more useful, in answering more questions about where you will have the most torque to the wheels. (through the gears) . As i always say, HP IS Torque through the gears at any vehicle speed!

MK
acceleration = Power / (mass x velocity)

GlenL

Mark,

My point was that if you had one graph of a normally-operaiting S4 you would clearly see the operation of the flappy and know that it was operating and at what RPMs it was actuating. Totally clear with torque. Obscured with HP.

That graph in your last post is really confusing. There are multiple scales on each axis? To make a complex analysis between cars with different tranny ratios, final drives, shift points and weights you need a more powerful tool than eyeballing a graph.

And, Mark, it's not "any vehicle speed" it's "the vehicle's speed." We don't have CV trannies back there.

mark kibort

tes, if you didnt have another graph to compare to, and we were talking about two identical S4s, but were only looking at one graph at a time, then yes, the characteristic "dip" without flappy working would be very apparent.

however, in looking at what will give you an indication of better acceleration for two cars, with either the same rpm range or totally different, the HP curve gives you all the information you need. Looking at torque only, you need to determine the slope change visually. looking at HP, just look at the arc of HP, and eyball your gear spacing range. its actually, as you saw before, very simple

Im trying to fight the "flat" torque curve, or "peaky" torque curve, this kind of venacular, is confusing and usually wrong. for a given HP , you want a flat HP curve, which really means your torque is falling (sloped down) if you have a peaky hp curve, you could have a peaky torque curve or a flat torque curve, neither is desirable. if you flatten out a torque curve, then the hp goes up and kind of changes the comparison doesnt it! what you want, is to flatten your HP curve. if you. if you try to raise torque at the end from falling, obviously, the hp will go up, but the torque always will fall in the usable range of the torque curve. why, because you always want to operate in the max hp range of the engine, why?? becuase acceleration = Power/(mass x velocity)

Getting back to the S4 and the flappy, i think anyone can see that the HP curves show clearly, the flappy not working. whats better about it, it more accurately proportionalizes its effect on scale. visually its a big torque change, but really a much smaller HP change. (but same percentages increase or decrease)

NOW, the last graph. its not confusing at all. there are not multple scales on each axis. its HP vs torque, and the only axis with a multiple scale is RPM. this is done so both cars can show their hp curve , scaled to their redline. (so they both are overlayed on eachother vs redline, because this is how the cars will operate.) check it out again. by looking at the torque curves, you could have no idea of which car is faster than the other (assuming same gear spacing and weight) however, by just eyeballing HP, its very clear. in this case, disproving ALL the torque crazed folks, both cars will accelerate the same from any vehicle speed.

(as a note, ive shown the MPHs in each gear and because the porsche has closer gears, it actually uses more area under the HP curve, and will have a distinct advanatage at any speed, especially after a shift at a lower rpm.. So much for that " low rpm GRUNT" of a V8 or V10!! and im not talking about driveability here)

so, you absolutely dont need "final drives, ratios, etc. sure, we have to compare equal weights or do a simple calculatoin of hp to weight to make sure thats constant. In this graph, a Viper could actually have 475 rear wheel hp and the porsche could have 438rwhp like this graph, and as long as the weights were 3200lbs vs 2900lbs like in SpeedGT, the comparison is valid and equal and the cars would have the same net accelerative forces at any vehicle speed.

mK

PS, acceleration = power / (mass x velocity) for any vehicle speed, two cars with the same power and mass, will have the same acceleration. same torque to the driven wheels (not flywheel rated engine torque). acceleration will go up porportionately with power. It also will go down proportionately as speed increases for a constant power.