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Topic # 223362 25-Sep-2017 20:40
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I saw an interesting YouTube video about why no production car can go 300 MPH / 483 KPH.

I rounded up to 500 KPH, because it's an easier number to remember.

He used the Bugatti Veyron for a bunch of calculations, because it had plenty of performance figures for calculations.

His primary conclusion was it was cooling was the major stumbling block.

1,500 HP = 3,000 HP of cooling!

This is enough cooling for a 20,000 M3 office building with over 40 outdoor units.

A lot of car radiators, 10 in this case, means a lot of drag.

I know electric engines and batteries generate a lot of heat also.

So anyone have an opinion?

Again we're talking a production car; not a one-off salt flat run.



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  Reply # 1872702 25-Sep-2017 20:47
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Anytime soon? no. the batteries will weigh the car down it won't be able to accelerate due to the weight.


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  Reply # 1872708 25-Sep-2017 21:04
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There's just too much drag on a 'production' car. Honda did 397kmh on the salt flats about 10 years ago with their F1 car, which was run with as little drag as possible. 

 

I don't know if it was using the year before 3.0L V10 or whether it was the 2.4L V8. Either way it will have had at least 700-900bhp, perhaps 20,000rpm and around 700kg.

 

You just have to push too much air out of the way. Something from Le Man is much more slippery than an F1 car, I think Peugeot hit 407kmh in 1989 before they put the chicanes in.

 

How big a motor can you fit in a Prius??


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  Reply # 1872717 25-Sep-2017 21:05
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Whats the point of production cars that go any faster than 150-200 KMH?





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  Reply # 1872719 25-Sep-2017 21:07
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Batman:

 

Anytime soon? no. the batteries will weigh the car down it won't be able to accelerate due to the weight.

 

 

Take away the batteries and use a really long extension cord... problem solved.





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  Reply # 1872723 25-Sep-2017 21:14
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timmmay:

 

Batman:

 

Anytime soon? no. the batteries will weigh the car down it won't be able to accelerate due to the weight.

 

 

Take away the batteries and use a really long extension cord... problem solved.

 

 

What kind of production car will that be? I suppose induction charging would be the only way, assuming it can charge it enough to produce that many thousand hps.


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  Reply # 1872724 25-Sep-2017 21:19
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jarledb:

 

Whats the point of production cars that go any faster than 150-200 KMH?

 

 

Or more than 110kmh?





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  Reply # 1872728 25-Sep-2017 21:24
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MikeB4:

 

jarledb:

 

Whats the point of production cars that go any faster than 150-200 KMH?

 

 

Or more than 110kmh?

 

 

If you have an ICE that has a top speed of 110km/h, it probably has so few hp that it will take 2 kms of accelerating to get to 110km/h from 80km/h. Which renders it useless.

 

If you have an electric car that is only capable of 110km/h, it probably has the same problem.

 

Then when the wind blows the wrong way you will only go backwards.


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  Reply # 1872760 25-Sep-2017 22:27
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No technical reason that you couldn't use jet or rocket propulsion. As all of the heat just shoots out the back, no need for radiators, car can be more streamlined. And no reason why a car manufacturer couldn't start building lots of such cars. Sure such a car would be ridiculously impractical and expensive, as jets and rockets have really poor efficiency at slow speeds. So it would also need a conventional engine for slow speeds.

 

And then there is the problem that there are very few places that you can even get a Bugatti Veyron up to it's max speed. Presumably there will be even fewer again if you did happen to own a car capable of 500Km/Hr. So apart from bragging rights of being able to say "my car can do 500Km/Hr" There is hardly any other use cases for owning such a car.

 

If you have that much of a "need for speed" You would probably have a lot more fun flying fighter jet aircraft.






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  Reply # 1872773 25-Sep-2017 23:19
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Aredwood:

 

No technical reason that you couldn't use jet or rocket propulsion. As all of the heat just shoots out the back, no need for radiators, car can be more streamlined. And no reason why a car manufacturer couldn't start building lots of such cars. Sure such a car would be ridiculously impractical and expensive, as jets and rockets have really poor efficiency at slow speeds. So it would also need a conventional engine for slow speeds.

 

 

This is a solved problem:

 

 

Sorry, can't resist :p


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  Reply # 1872774 25-Sep-2017 23:25
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The problem you have is Tyres, and providing enough down force to stop the car flying into the sky. When you are generating enough down force, the weight would generally prevent the power to weight ratio required.

 

 


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  Reply # 1872790 25-Sep-2017 23:57
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kingdragonfly: 

So anyone have an opinion?

Again we're talking a production car; not a one-off salt flat run.




I'm thinking it would be because so few people would want to buy it. That capability would be basically useless, but very expensive. 

I have no interest in a Tesla Model S as far as it's top speed is concerned. Anything much over 140kph is useless to me. 






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  Reply # 1872825 26-Sep-2017 06:01
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timmmay:

 

Batman:

 

Anytime soon? no. the batteries will weigh the car down it won't be able to accelerate due to the weight.

 

 

Take away the batteries and use a really long extension cord... problem solved.

 

 

I am sure the physics of using an extension cord, the drag created if having to drag it, or the weight of sufficient gauge cord coiled up in the car plus the apparatus needed to allow it to uncoil at the terminal speed would be less efficient, and weigh more than a battery to allow a say 10km run of what ever it would be to get to terminal speed, and made a return pass to claim the record.


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  Reply # 1872826 26-Sep-2017 06:02
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jarledb:

 

Whats the point of production cars that go any faster than 150-200 KMH?

 

 

Why does a dog lick its balls???

 

 

 

It can.


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  Reply # 1872827 26-Sep-2017 06:04
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Aredwood:

 

No technical reason that you couldn't use jet or rocket propulsion. As all of the heat just shoots out the back, no need for radiators, car can be more streamlined. And no reason why a car manufacturer couldn't start building lots of such cars. Sure such a car would be ridiculously impractical and expensive, as jets and rockets have really poor efficiency at slow speeds. So it would also need a conventional engine for slow speeds.

 

And then there is the problem that there are very few places that you can even get a Bugatti Veyron up to it's max speed. Presumably there will be even fewer again if you did happen to own a car capable of 500Km/Hr. So apart from bragging rights of being able to say "my car can do 500Km/Hr" There is hardly any other use cases for owning such a car.

 

If you have that much of a "need for speed" You would probably have a lot more fun flying fighter jet aircraft.

 

 

I am sure there would be technical reasons for not building this car, mainly the insanely hot exhaust coming out of the rear melting the car behind at the lights.


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  Reply # 1872829 26-Sep-2017 06:53
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networkn:

 

The problem you have is Tyres, and providing enough down force to stop the car flying into the sky. When you are generating enough down force, the weight would generally prevent the power to weight ratio required.

 

 

 

 

I guess the answer to this is variable geometry wings or other airfoils. As speed goes up, they adjust to produce less downforce, so that there is always about 1 or 2G.

 

But, yes, tyres. Centrifugal forces on them would become significant.

 

 


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