Why does amount of horsepower matter...?

[RS2]

Why is there less passing when the braking zones are shorter?

Because the physical distance to make the pass is smaller. If you must start braking at 400 feet compared to 300 then the time to pull up along side and get by the car in front just is not there. So one must follow and wait for a mistake or attempt to get off a corner better an try and get alongside before the next corner.

[Peabody]

First, I don't think that is completely true. If that was so simple, why do they need to build physical models? Perhaps the physics models can't completely mimic reality?

So please address the physics question.

First - how much would a 400 hp car have to weigh to have the same acceleration as the current car with 800 to 900 hp? I'm guessing 800 lbs or less, perhaps I'm wrong.

Second - do you believe given cost and safety constraints that there is a solution with that power to weight ratio that has a 400hp engine? Seems to me that might be a very very difficult task!

At lower speeds (say under 100 mph or so), power to weight ratio is the key to acceleration. At higher speeds it is power to drag.

Which is why a performance Motorcycle with 150 HP or less can outrun almost any production car to 100-120 and a restricted 3400 lb NASCAR COT can go almost 200 mph with under 500 hp. Most bikes are small and light, but not very areodynamic, and while a stock car is large and heavy it can have relatively low drag.

So if you want to reduce HP and get similar acceleration at all speeds, the only solution is less weight and less drag - basically a lightweight streamliner. If you outlaw exotic materials, then the basic car structure can't be as strong - or safe - as a slightly heavier structure and downforce (adding downforce involves moving air which adds drag) is limited so cornering speeds drop and lap times increase.

Everything is a compromise, and IMHO the slim gains from the Deltawing couldn't outweigh all of the downsides.

[SpeedwayRyan]

Right. Because they weight pretty much the same. Put the Nissan's engine in a Miata and see if it's easier to break loose than a Viper. Hint: It will be.

Power-to-weight ratios are great for comparing various cars in terms of estimated acceleration, assuming no traction problems.

"Breaking the tires loose" is hard to break down to simply a power-to-weight thing because the cars can be so different...low end torque, suspension setup, tires (width/compound/sidewall stiffness/etc.), clutch/transmission setup, gear ratios, weight distribution, etc. A lightweight, high-HP car set up to hook at the dragstrip could have a lot LESS problems with tire spin than a heavier car with less HP...so many variables.

[Mike Kellner]

Mike, I think we have considerable common ground.

No doubt. Basically we both want to improve the show, which means returning passing to auto racing. Some differences in approach. Hey, if everyone agreed on everything this place would be boring.

~ ~ ~

If the Delta Wing weighs 1100 LB with driver and full fuel ready to race, and has 400 HP, it will accelerate about the same as the current car if it had about 690 HP, assuming the drag is reduced in proportion to the weight. That means similar performance. That also means it has to weigh about 800 dry. That is kinda light. GP cars weigh about 1000 LB dry without any ballast. They are good in crashes, but they are very expensive to build, and 25% heavier. Lightness is expensive, either in money or broken bodies.

~ ~ ~

The current cars can break the tires loose, watch a few pit stops. They don't do that in the race because it toasts rears. If you see someone driving dramatically, hanging it out, and lighting the tires out of slow turns, that person is over-driving the car, and would be faster if they were smoother. That is why you don't see that style of driving anymore.

The current car has a power to weight ratio of about 2.8 lb/hp. That is not an underpowered car. The only reason it isn't faster at indy is aero rules designed to create drag and keep lap speeds around 225. Take off the various wickers and other draggy items, increase the revs, and they'd be back to 230+. The same cars were up close to 230 just a few years back. If there were two brands of motor and tire, and no aero-hobbles, speeds would be even higher than that. The current speeds at Indy are where they are on purpose.

The new car will be more like 2.4 lb/hp. About the same as giving the old car 100 extra HP.

mk

[christcc2]

Mike. You make a good point in regard to the fact that the current Dallara is not "underpowered". Other aspects of the car are in the way of it performing better.

That said, the current car could use another 100ft/lb of torque.

[doitagain]

If the Delta Wing weighs 1100 LB with driver and full fuel ready to race, and has 400 HP, it will accelerate about the same as the current car if it had about 690 HP, assuming the drag is reduced in proportion to the weight. That means similar performance. That also means it has to weigh about 800 dry. That is kinda light.

I was thinking they had reduced drag even more dramatically.

[Mike Kellner]

I was thinking they had reduced drag even more dramatically.

Could be, I have no idea. If so, that would mean a higher top speed, and higher lap speeds on big ovals.

mk

[doitagain]

Key Specifications (estimated)
•Weight with driver: 1,030 lbs.
•Horsepower: 300 BHP
•Wheel base: 125 inches
•Front track: 24 inches
•Rear track: 70 inches
•Aerodynamic drag: Cd 0.24

http://deltawingracing.com/2010/02/next-generation-concept-izod-indycar-unveiled-in-indianapolis/

[Mike Kellner]

Weight with driver = 1030? If it holds 11 gallons of fuel, and has a 150 lb driver, that leaves 814 lbs for car, coolant, and lubricants, or like a 750 LB dry weight. Not sure it could hit the wall at 225 and take care of the driver.

With 300 HP, that is 3.43 lb/hp, which is much higher than the current car, meaning lower acceleration, though it may make up for it at high speeds, if it has a higher top speed. For the most part, drag begins to be the big factor at 80% of top speed, which is where drag eats half the available power. Sounds to me like it would be slower anyplace where you run under 200.

Whatever. I always thought that if Chip likes it that much, he should have a small one made, chrome it, and bolt it onto his hood. It ain't what I'd call an Indycar.

mk

[Roninho]

Because the physical distance to make the pass is smaller. If you must start braking at 400 feet compared to 300 then the time to pull up along side and get by the car in front just is not there. So one must follow and wait for a mistake or attempt to get off a corner better an try and get alongside before the next corner.

Hmm, i'm no scientist, but on most passes one can see that the passing attempt is going to be succesfull before the cars are starting to brake. Imo being close to the other car, getting a better exit out of the corner and getting a tow are essential in passing. As long as your braking distance is the same as the other car then it is about having the inside and getting next to the other car before you brake.

So i might be wrong, but to me it doesn't look like the braking distance is that important (assuming braking distance is roughly the same for all competitors). Aerodynamics that allow you to stay close and get a tow do seem to be important.

[Luigi]

Hmm, i'm no scientist, but on most passes one can see that the passing attempt is going to be succesfull before the cars are starting to brake. Imo being close to the other car, getting a better exit out of the corner and getting a tow are essential in passing. As long as your braking distance is the same as the other car then it is about having the inside and getting next to the other car before you brake.

So i might be wrong, but to me it doesn't look like the braking distance is that important (assuming braking distance is roughly the same for all competitors). Aerodynamics that allow you to stay close and get a tow do seem to be important.

It is true in OW racing today because the braking distances are so short.

[gonzo]

Right. Because they weight pretty much the same. Put the Nissan's engine in a Miata and see if it's easier to break loose than a Viper. Hint: It will be.

I love it when people make my point for me.

Make your point? I don't understand what the hell your point is.