Why can a 1400 lb F1 car handle 1000 plus horsepower but a Viper can't?

Vigo wrote: Think of torque in a very simple way.. Imagine your car sitting on the ground, and you put a torque wrench on the axle and try to spin the tire on the pavement (car is stationary and cant be moved in this example). Imagine you are a BEAST and you can put any amount of torque on the torque wrench. So you figure out that it takes, say, 1000 lb ft of torque to spin the tire on the ground. You decide to simulate a motor that makes 500 hp at 2000rpm.. thats 1310 lb ft. The tire spins. Now you decide to simulate a motor that makes 500 hp at 8000 rpm. Thats only 330 lb ft! The tire doesnt even come CLOSE to spinning. You can hit the tire with 1100 lb ft of torque one time per second, and it will spin every time. You can hit the tire with 900 lb ft of torque 875600 times per second, and it will never spin. HP is just an extrapolation of X torque @ X rpm. HP does not make you lose traction.. torque does.

I'm pretty sure you are wrong here. Stacking torque applications in your 875600 times per second example is like stretching a rubber band. The tire does not instantaneously recover after each torque application and regain full capability, it is still at mid or full stress from the previous one. If you apply small amounts of torque often enough you build up to a level where you will break traction. That's why horsepower is a useful measurement, not just torque.

MrJoshua wrote:

Vigo wrote: Think of torque in a very simple way.. Imagine your car sitting on the ground, and you put a torque wrench on the axle and try to spin the tire on the pavement (car is stationary and cant be moved in this example). Imagine you are a BEAST and you can put any amount of torque on the torque wrench. So you figure out that it takes, say, 1000 lb ft of torque to spin the tire on the ground. You decide to simulate a motor that makes 500 hp at 2000rpm.. thats 1310 lb ft. The tire spins. Now you decide to simulate a motor that makes 500 hp at 8000 rpm. Thats only 330 lb ft! The tire doesnt even come CLOSE to spinning. You can hit the tire with 1100 lb ft of torque one time per second, and it will spin every time. You can hit the tire with 900 lb ft of torque 875600 times per second, and it will never spin. HP is just an extrapolation of X torque @ X rpm. HP does not make you lose traction.. torque does.

I'm pretty sure you are wrong here. Stacking torque applications in your 875600 times per second example is like stretching a rubber band. The tire does not instantaneously recover after each torque application and regain full capability, it is still at mid or full stress from the previous one. If you apply small amounts of torque often enough you build up to a level where you will break traction. That's why horsepower is a useful measurement, not just torque.

And his example ignores gearing, the two examples given would never have identical gearing in the tranny or diff...

It isn't horsepower that spins tires but torque! Tell me how a 1.5L turbo engine is going to make the same about of torque as a 8.0L Viper engine with both making equal horsepower? Also what torque is does make is at much higher engine speed.

In reply to Vigo: in this vein, i think you mentioned a large part of it in your first post, OP.

Huh? I dont see any of my post addressed by the OP's first post. Maybe you left out something?

no way in hell this exact same car wouldn't be faster around a racetrack if they took away half the power.

Change that to half the torque and you're getting somewhere. No reason to take away power, though. Thats part of what i was trying to explain.

The answer is that Renault has an engineering team with singular focus, with no compromises.. to build a racing car.

Henessey is modifying a rolling example of compromise. His market does not require the car to do much more than turn tires to their gaseous form and post big dyno numbers regardless of whether or not he employed the services of a chassis engineer in any endeavor more than "Make sure this doesn't break in half".

Vigo wrote:

In reply to Vigo: in this vein, i think you mentioned a large part of it in your first post, OP.

Huh? I dont see any of my post addressed by the OP's first post. Maybe you left out something?

i'm sorry, i was speaking as if to the OP. my apologies for not wording that well.

Torque is fairly irrelevant when cars have gears. An 18000 RPM F1 engine that makes 800 horsepower might not have the torque of a Viper V10, but our friendly formula: drive wheel torque = flywheel torque x gear ratio x final drive x 0.85 means that the torque at the wheels is all the matters, and that's why revs are awesome.

Take my Type R, with its paltry 130 lb.-ft. of torque and its awesome ATS 4.9 final drive.

Flywheel Torque: 130

First Gear: 3.23

Final Drive: 4.929

Drive Wheel Torque: 1759.234035

Since it revs to over 8400 RPM, it can still get to a fair road-car speed in first gear, and just about hit 60 in second. It makes 1700 lb.-ft. of torque at the front wheels in first gear. Take that, V10!

F1 cars generate THOUSANDS of pounds of downforce at high speeds, and hundreds of pounds at fairly low speeds, and they're geared to make the most of their power curve.

I wonder if once traction is lost in both cars and all the zillions of lbs of torque twisting away at air and the 16k rev bouncing snarl are actually delivering "not much" to the tarmac. It would seem the lower mass of the f1 car would be accelerated (how much?) more effectively and regain traction more readily whilst the viper is a big fat pig bellowing as it drowns it's own melted rubber.

Power to weight is the real killer. F1 cars weigh about 1400 pounds in race trim. Assume unlimited traction and equal power, and the F1 car devours the Viper in a straight line, and it gets worse in the corners with the formula car's downforce, and it gets really unfair under braking. Same applies if the tires aren't totally hooked up. If a tire generates 70 percent of peak friction in a slide condition, it's still put to much better use on the lighter car.

You can't cheat mass, which is why lighter=better in race cars.

Glenn Bunch's Challenger has gobs of power, yes, but it runs away from a Viper ACR-X on the back straight of VIR because it has all that power AND it only weighs 2600 pounds, which is crazy for a car that massive.

http://www.youtube.com/watch?v=GUlT8_Z07L4&feature=related

I'm pretty sure you are wrong here. Stacking torque applications in your 875600 times per second example is like stretching a rubber band. The tire does not instantaneously recover after each torque application and regain full capability, it is still at mid or full stress from the previous one. If you apply small amounts of torque often enough you build up to a level where you will break traction.

Take the 900 (out of necessary 1000) number and drop it to 2. Let's say you apply that 2 ft lbs a million times a second. There is the implication there that you are letting off in between hits. If the intervals are 50/50 you are putting that torque in 50% of the time.. Well, if i just put a wrench on it and put a constant 2 lb ft into it, i am actually putting the torque in 100% of the time, or the equivalent of hitting it 2 million times a second. It's still not moving. My example is not like an impact gun because there is no kinetic energy being accumulated BEFORE the torque is transferred. Even in a real car there is no recurring impact effect other than the minor deflection and elasticity of the driveline parts between the piston and the tire, unless someone is saying the power pulses coming off the crank are breaking traction when the same torque averaged out over time wouldnt.

As for the gearing thing, thats basically true, except that theres a really steep diminishing rate of returns with trying to gear your way out of lack of torque at the wheels. F1 cars can afford NASA-style metallurgy in all their engine parts and they dont have to be effective in lower speed ranges (ever seen the episode of top gear where hammond stalls one like 15 times before getting rolling?). To make the F1 car as tractable as the Viper over as wide a range of conditions, it would need even more gears to go with its $$$$$$$ engine.

Not everyone can afford a reciprocating assembly that can withstand 10,000Gs of acceleration (im serious), so the Viper does what it can with a mere few thousand dollars of mundane alloys in the motor.. Boost is cheaper than revs.

Vigo wrote: HP is just an extrapolation of X torque @ X rpm. HP does not make you lose traction.. torque does.

Simply put...Horsepower is a measurement of torque over time....

bigbens6 wrote:

MrJoshua wrote:

Vigo wrote: Think of torque in a very simple way.. Imagine your car sitting on the ground, and you put a torque wrench on the axle and try to spin the tire on the pavement (car is stationary and cant be moved in this example). Imagine you are a BEAST and you can put any amount of torque on the torque wrench. So you figure out that it takes, say, 1000 lb ft of torque to spin the tire on the ground. You decide to simulate a motor that makes 500 hp at 2000rpm.. thats 1310 lb ft. The tire spins. Now you decide to simulate a motor that makes 500 hp at 8000 rpm. Thats only 330 lb ft! The tire doesnt even come CLOSE to spinning. You can hit the tire with 1100 lb ft of torque one time per second, and it will spin every time. You can hit the tire with 900 lb ft of torque 875600 times per second, and it will never spin. HP is just an extrapolation of X torque @ X rpm. HP does not make you lose traction.. torque does.

I'm pretty sure you are wrong here. Stacking torque applications in your 875600 times per second example is like stretching a rubber band. The tire does not instantaneously recover after each torque application and regain full capability, it is still at mid or full stress from the previous one. If you apply small amounts of torque often enough you build up to a level where you will break traction. That's why horsepower is a useful measurement, not just torque.

And his example ignores gearing, the two examples given would never have identical gearing in the tranny or diff...

Precisely. If you have 100 lb ft/torque at 10,000 rpm you can run that through 10:1 gearing for the same vehicle speed and same at wheel torque as a motor that makes 1,000 lb/ft torque at 1,000 rpm with 1:1 gearing. The tires won't know the difference.

Also, wouldn't the light weight actually hurt the F1 cars ability to put the power down? I know that the coefficient of friction decreases with load, but 3500 lbs pushing down on the tires of the Viper (no downforce, or very little) would be the same, as far as the tires are concerned, as that F1 car and 2100 lbs of downforce. Even with a ground effects car, 2100 lbs of downforce is very high speed and you simply don't see F1 cars smoking the tires at 140 mph like the Viper does.

Even the tire sizes aren't that different. 345/30/20s are awfully big, and I think they were running r-compounds in that test.

And COG should be in the Viper's favor as well. A high COG will transfer weight to the rear wheels, precisely where it's needed. The F1 car, presumably, has much less weight transfer.

Perhaps this all comes down to anti-squat geometry in the Viper messing things up? Or maybe tires haven't come as far as I assumed.

Scott Lear wrote: Power to weight is the real killer. F1 cars weigh about 1400 pounds in race trim. Assume unlimited traction and equal power, and the F1 car devours the Viper in a straight line, and it gets worse in the corners with the formula car's downforce, and it gets really unfair under braking. Same applies if the tires aren't totally hooked up. If a tire generates 70 percent of peak friction in a slide condition, it's still put to much better use on the lighter car. You can't cheat mass, which is why lighter=better in race cars. Glenn Bunch's Challenger has gobs of power, yes, but it runs away from a Viper ACR-X on the back straight of VIR because it has all that power AND it only weighs 2600 pounds, which is crazy for a car that massive. http://www.youtube.com/watch?v=GUlT8_Z07L4&feature=related

I absolutely agree. What has me curious is why the lighter car, which has a far superior power/weight ratio, puts its power down better than the car with the inferior power/weight ratio.

Giant Purple Snorklewacker wrote: The answer is that Renault has an engineering team with singular focus, with no compromises.. to build a racing car. Henessey is modifying a rolling example of compromise. His market does not require the car to do much more than turn tires to their gaseous form and post big dyno numbers regardless of whether or not he employed the services of a chassis engineer in any endeavor more than "Make sure this doesn't break in half".

And what are the engineering differences the Renault guys didn't have to compromise for? You know, in case I hypothetically go to graduate school next year and get involved with an already moving project to build a race car from scratch ...

In other words, if I build a car, how can I ensure it does more than convert very large tires into gaseous form?

MrBenjamonkey wrote:

Giant Purple Snorklewacker wrote: The answer is that Renault has an engineering team with singular focus, with no compromises.. to build a racing car. Henessey is modifying a rolling example of compromise. His market does not require the car to do much more than turn tires to their gaseous form and post big dyno numbers regardless of whether or not he employed the services of a chassis engineer in any endeavor more than "Make sure this doesn't break in half".

In other words, if I build a car, how can I ensure it does more than convert very large tires into gaseous form?

There is a whole field of study in that question. I am still reading everything about chassis design I can get my hands on to build my own race car. I am no expert but for starters... become an expert ;)

As for what the differences are... Viper to F1 Renault?:

• cost. No one would be able to afford a viper made with the exotic materials, exacting tolerances and mind bending processes that go into a modern F1 car. Hell, no one could afford that in a new jet plane.
• durability. No one would buy a viper that required new hiem joints, dampers, brakes, rotors, clutch, tires every time you went for a drive and an engine that has to be replaced 8x a season.
• comfort. As uncomfortable as a viper is... compared to a car that would shatter a control arm on a speed bump - its a whole different level of squishy.
• labor. Imagine you need a crew of 40 to get going in the AM.
• rules. One has the FIA the other... the Institute for Highway Safety. ;)

All that blathering can be boiled down to... They have completely different design criteria and challenges. One is designed from the ground up to do only one thing, no compromises that do not have to made, no expense spared... the other is a car.

MrBenjamonkey wrote: Precisely. If you have 100 lb ft/torque at 10,000 rpm you can run that through 10:1 gearing for the same vehicle speed and same at wheel torque as a motor that makes 1,000 lb/ft torque at 1,000 rpm with 1:1 gearing. The tires won't know the difference.

Not quite.

That is to say, the tires won't know the difference, but the driver sure will.

Let me put it this way: In your example, if the tires did lose grip, if one engine would zing up to 12,000rpm, the other would only have to get up to 1200rpm to get the same tirespin. One of these engines will be easier to modulate than the other.

You know there are just so many variables and apples/oranges things in this comparison, that maybe we should look at it from a new direction..

which would be that the only real reason wheelspin exists when you are talking about cars that cost at LEAST $100k and with f1 into the millions, is that there is a lack of effort to stop it.

It's really not rocket science to prevent wheel spin. On some cars like a turbo viper it may be difficult to control purely with the gas pedal because unlike an n/a high-revvving engine with a very linear powerband, a turbo motor has much more inconsistent power delivery, especially when you're on and off the gas (feathering).

So if not through the pedal, what then? Oh i dunno, maybe something as simple as comparing the wheelspeed of the driven vs undriven wheels? How about driven wheel speed vs gps? How about rpm, tps, boost, and vehicle speed vs rate of vehicle accel? How about rate of accel vs observed 'ideal' rate of accel? So many different monitoring schemes are possible... and most of them are in use somewhere.

Then cut power. How do you cut power? Oh i dunno, something as simple as retarding timing, adding fuel, dropping or venting boost, closing throttle blade, moving manifold tuning valve, touching brakes, even shifting cam timing. These things can all be easily electronically controlled. A lot of them have no inertia (i.e. dont have to overcorrect).

In apps where the traction is actually critical, in the modern day, it is easily possible to have every bit of control over wheelspin that you could ever want. Building a 1000+ hp viper tuner car is not one of those situations. Just like the OP said, the car clearly wasnt built to go fast AROUND a racetrack. It was built to lay down dyno numbers, get photos smoking the tires at 150mph, and generally to win dick-waving contests.

But if they wanted to control the wheelspin, they could.

MrBenjamonkey said...

"Also, wouldn't the light weight actually hurt the F1 cars ability to put the power down? I know that the coefficient of friction decreases with load, but 3500 lbs pushing down on the tires of the Viper (no downforce, or very little) would be the same, as far as the tires are concerned, as that F1 car and 2100 lbs of downforce. Even with a ground effects car, 2100 lbs of downforce is very high speed and you simply don't see F1 cars smoking the tires at 140 mph like the Viper does.

Even the tire sizes aren't that different. 345/30/20s are awfully big, and I think they were running r-compounds in that test.

And COG should be in the Viper's favor as well. A high COG will transfer weight to the rear wheels, precisely where it's needed. The F1 car, presumably, has much less weight transfer.

Perhaps this all comes down to anti-squat geometry in the Viper messing things up? Or maybe tires haven't come as far as I assumed."

Good stuff- I was thinking about this in the shower and a couple of things occurred to me: The 2100lbs of F1 areo downforce is nearly constant in clean air at lets say "x" speed, while the vipers equivalent lard of 2100 lbs is sprung mass at "x" speed bouncing up and down and jiggling on springs like mad. I reckon the loading of the chassis looks very very different and would favor the constant loading provided by F1 areo by a texas mile.

Another thing that popped into mind was the tire design- F1 tires are high air volume unfashionably tall side walled affairs that (I reckon) give much more compliance and favorable contact patch than the big fat 30 series whatevers. And the F1 tire technology is going to be bleeding edge. Advantage F1. shocking.

The viper "normal car" packaging limits the suspension design to very short bits of connective geometry. Obviously an F1 car does need to meet the requisite rich guy 2 golf bag in the trunk and hot second (or third) passenger seat specification that the Viper does, so- advantage F1 car... stop the press.

Vigo wrote: You know there are just so many variables and apples/oranges things in this comparison, that maybe we should stop looking at it.

Fixed that for ya!

Look at this as more of a grape/raisin comparison. The grape has all the newest, sweetest and greatest ingredients; the raisin is the dried-up version that has no other useful purpose - and is flattered when used to supplement oatmeal.

I read the thread, and its pretty obvious. I reread the title, the basic question and:

It basically comes down to the viper is a cheap car made to have lots of HP for the sear fact of making HP

The F1 car of any year is made to go as fast as possible, and have lots of HP over a wide range.

Slightly more complicated then that 4 things come to mind:

First is power. The Viper makes likely 8,000-10,000ft-lbs in first gear. Your honda will never equate that. An indy car has a much smoother spread out torque curve (looking at over all shapes not exact numbers) and that helps traction

Second is traction. Even if the tires were the same width, the indy tire has a much bigger side wall and is made to be far softer and no compromise. I bet the actual contact patch is far bigger on an indy tire. A short 30 series side wall and a DOT legal stiff sidewall will massively hurt traction

Third is weight. Low weight helps reduce the cars resistance to move. put a clutch that will never slip in a honda, and put it in the viper. The difference in power and weight will make it slip as it has more force to over come (kinda bad example but come on- im tired lol). basically less mass changes speed easier at any speed

Forth is down force. Once the F1 car gets moving, it will keep making more and more grip. I bet the viper develops very little downfoce, it may actualy make lift.

Thats it in a nut shell, is a compromised car VS a purpose built car.

~Alex

So, lets see if I can sum up some of this... I'm trying to think of practical applications of these differences...

1. The F1 car weighs a bit under half of the Viper; if the Viper loses weight, it can improve cornering, braking and acceleration.
2. The F1 car has an aero optimized body and its suspension, etc. is designed to use that. if the Viper gets improved aero, ala ACR-X, it will improve
3. Because of the exceptionally low mass and inboard suspension (not sure about brakes), the F1 car can run with smaller rims with taller sidewalls. It still has amazing turn-in, thanks to the low mass. The Viper might improve here by running a smaller sized rim diameter with a larger sidewall on the rear wheels. It possibly also has the side-effect of reducing unsprung rotating mass. Since the fronts don't provide forward power, you want to preserve turn-in.
4. The F1 car is designed to have as low a center of gravity as possible. This means prioritizing weight savings at the top of the car. It also allows the F1 car to run with little to no anti-squat, because I wouldn't be surprised if the COG is BELOW the suspension attachment points. (I'm speculating here...) The Viper could be helped by raising the suspension attachment points to the highest point possible, lowering the engine as much as possible (dry sump, etc), lowering the seat, etc. Having a full undertray helps here too.
5. Coupled with weight is gearing. The torque curve to gearing to weight has to be properly matched once traction is optimized. Being able to spin tires at half throttle is fairly useless. It is far better to be able to spin tires only at higher throttle positions but have taller gearing for that gear. Having the ability to customize each gear ratio is essential. If you figure that you have 6 gears, with a top speed of 150 mph on the course, you have a first gear that will act as described, and the rest are spaced to keep the top end of top gear near redline at top speed for maximum acceleration.

Knurled wrote:

MrBenjamonkey wrote: Precisely. If you have 100 lb ft/torque at 10,000 rpm you can run that through 10:1 gearing for the same vehicle speed and same at wheel torque as a motor that makes 1,000 lb/ft torque at 1,000 rpm with 1:1 gearing. The tires won't know the difference.

Not quite. That is to say, the tires won't know the difference, but the driver sure will. Let me put it this way: In your example, if the tires did lose grip, if one engine would zing up to 12,000rpm, the other would only have to get up to 1200rpm to get the same tirespin. One of these engines will be easier to modulate than the other.

Hmm, I hadn't thought of that. Explains a lot.

I realize this is an apples to oranges comparison, and maybe I picked vehicles separated by too much, but the reason I was wondering is that I want to make a racecar next year. I'd like to do my own chassis from tube and then use junkyard subframes/drivetrains/steering/brakes from production cars. I'm going to try and make some pretty serious hp.

What had me wondering about this is observing how cars put the power down. A MK4 Supra, for example, doesn't put the power down very well at all in a road racing situation, but a C5 Corvette does. Or a Miata just making tire smoke at 300 hp while a similarly powered, similar weight, similar tire first generation RX7 will easily handle 300 hp. I could go on. 240 SX = no traction on exit but an FC has tons of traction. A MK1 MR2 vs a MK2 MR2. An FD (good traction) vs a Z32 (not so much). An 05 Mustang (not much traction in my experience) vs a 02 Camaro (very good traction).

When I make my own, I'd prefer to be more like the Vette than the Supra, but I don't understand the differences as much as I'd like.

So far it seems that it's best to run a big sidewall in the driven wheels, as little anti-squat as possible (maybe even pro-squat?), use aero downforce for more consistent loading and a higher revving motor that is more easily modulated.

MrBenjamonkey wrote: Or a Miata just making tire smoke at 300 hp while a similarly powered, similar weight, similar tire first generation RX7 will easily handle 300 hp.

O rly?

I've never driven a 300hp RX-7 but 200hp is kinda touchy. And, apparently, at the 600hp level, you can expect to have traction problems below about 100-120mph.

DirtyBird222 wrote: Simply put...Horsepower is a measurement of torque over time....

Bingo. There is no means, anywhere, to measure horsepower. We measure torque, and use a formula (based on a very old criteria that basically represents how far a single drawhorse can pull a specific weight over a specific distance) to convert that to horsepower.

In other words, all horsepower figures are derived from measured torque over time (which is another way of saying RPM). There is no known method to directly measure horsepower; we can only directly measure torque.

Because of the formula, Horsepower = Torque at 5250 RPM. Always. We get this from the formula where: HP = [torque ft/lbs x RPM] divided by 5252 1 ft/lb of torque at 5252 RPM is 1 HP at 5252 RPM; the same 1 ft/lb at 10,504 is 2 HP; the same 1 ft/lb at 21,008 RPM is 4 HP. The 1 foot-pound of torque gives all three HP values; all that changes is the RPM where peak torque appears.

Note that sometimes you see power curves where the horsepower and torque curves cross at somewhere other than 5250 RPM. This is your clue that the chart is bogus, because if you use the formula, that is impossible. (Actually, I think its 5252, but what's 2 RPM between friends?)

Torque is a twisting motion. Horsepower is a measure of work.

If torque is increasing, acceleration will increase. If torque is falling, acceleration will decrease. [Note that by "acceleration" we really mean acceleration over time; ie how hard you're getting pushed back into your seat].

Since on a Viper, torque is high at low RPM, and remains high over the powerband, it can initiate wheelspin at will. In an F1 car, torque is low at low RPM ... it may not be enough to overcome the tire's traction and car weight if you pop the clutch at too low revs.

Lets, for argument sake, say the Viper makes 500 lb/ft of torque somewhere in the powerband. Let's also say that the F1 engine also makes 500 lb/ft somewhere in the powerband.

Now, lets further assume that the peak torque in both happens at redline. If you give me a bit of liberty with my figures, to keep the math simple*, we get:

Viper = redline = 5,000 RPM / torque peak 500 ft/lbs @ 5,000 RPM / HP peak 500 @ 5,000 RPM

F1 = redline 20,000 RPM /torque peak 500 ft/lbs @ 20,000 RPM / HP peak 2,000 @ 20,000 RPM

So, they both make the same peak torque. But launching at more than 10,000 RPM is tricky business, so the F1 car is harder to wheelspin. Even at 10 Grand it may not be in the powerband yet. With the Viper, it's right there where your foot always is and you can launch right into high torque, so it's easier to wheelspin.

• All we really have to do here is assume Torque = HP at 5,000, not the correct 5,252 RPM. That keeps the numbers simpler. Then we make the Viper redline 5,000 instead of whatever it is, probably 6,000 or a bit more. With the F1 engine, torque peak is probably well below redline, but the math doesn't lie ... you need 500 lbs/ft to get 2,000 HP at 20K, period; the formula is pretty straightforward. F1 drivers tend to shift in the 12K ~ 17K range, so we might assume that's the actual powerband. But complex math doesn't help us understand things, so we go with the assumed numbers to get the concept across. If you "get it", it's easy to plug in the real numbers later and still see the relationships.