How much power needed to reach 190 m/h ?

[Roslin]

How much power is needed to reach 190 mph. in an old SC ? I'm not thinking on turbo engine, but maybe a 3.8 with some mods.. I know many other things than engine / gearbox should concerned if the cart should be build for so high speed .

Roslin

[Steve@Rennsport]

Roslin,

Very high speeds are attainable by factoring engine power (of course), gearing, and just as important, aerodynamic drag.

I will tell you without reservation that pushing an SC to 190 MPH takes a LOT of power and thats not very likely with a naturally-aspirated engine of any kind. These are high-drag cars,......

[Shoepop]

Subscribed but can't answer your question way to many variables but interesting subject. I remember YEARS ago an article in Excellence mag 'I believe'. It was a red 911 chopped top early 911 that set a record at Bonniville with a small displacement turbo engine. 170+ MPH sticks in my mind but my mind is old. I have been through all my old magazines 10+ times and can't locate it. Maybe someone on forum will remember and or locate that will give you a baseline.

[JeremyD]

Look at the ruf yellowbird - it had a smooth pan and gobs of HP

[Hugh R]

Check this article out on the PP Tech Articles it will answer your questions. The Cliff Notes version (for those who remember them) is that hp demand goes up with the cube of the speed. At 55 mph, you need about 8 hp, at 200 mph, you need about 340 hp.

http://www.pelicanparts.com/techarticles/physics_racing/part6.htm

[Brorag]

sprinkle lithium crystal dust into the gas tank. That'll get you to warp power.................

[trader220]

I am no expert but the stock Sc with no aero mods I believe would take huge power to move enough air out of the way so it could do 190mph

[burgermeister]

Originally Posted by Brorag

sprinkle lithium crystal dust into the gas tank. That'll get you to warp power.................

That's DI-lithium crystals ...

You can also change out the windscreen for "transparent aluminum". Oddly enough, this miracle material would theoretically have very similar stiffness and density as glass, with somewhat lower tensile strength but superior notch sensitivity. An engineering joke in the movie, I suspect ...

We rehquihre nuhclehahrr wuesselss.

[burgermeister]

Let's see ... assumptions:
mass = 2750 kg
cd = 0.40
A = 1.6 m^2
RR = 0.005 (rolling resistance coefficient)
Driveline Efficiency = 0.85
So, HP required should be cd * A * v^3 + RR * mass * v^2
(I actually can't remember if the rolling resistance part has a v or a v^2 multiplier ... v^2 feels right to me, but feel free to correct me if I remembered it wrong.)

Using these assumptions, a 218Hp motor gives a top speed of 147MPH. Not too shabby, though of course I adjusted the rolling resistance coefficient to make it work out that way. Also to roughly provide equal power drain as aero drag at 50 MPH.

190 MPH would then require 446 HP.

[JP911]

Originally Posted by burgermeister

Let's see ... assumptions:
mass = 2750 kg

That's a really heavy 911.

[burgermeister]

Originally Posted by JP911

That's a really heavy 911.

Wow, it sure is. Must have gotten the transparent aluminum formula off and used transparent depleted uranium instead. I oughta have multiplied that by 0.454.

Of course, I'd just have back calculated a rolling resistance coefficient of 0.11 instead, and luckily the answer comes out the same. If that's my only screwup, I will be pleased.

[74911]

My (distant) memory of college physics says that mass doesn't effect top speed - only the time need to get there.

Did a little searching and came up with this:

http://www.physforum.com/index.php?showtopic=14909

http://www.nsxprime.com/FAQ/Miscellaneous/TorqueHPSpeed.htm

http://www.miata.net/sport/Physics/06-Speed.html

-Mark

[slodave]

I know a Targa that can hit 163MPH with the top off...

[Steve W]

Originally Posted by slodave

I know a Targa that can hit 163MPH with the top off...

Correction, that's 165 mph and only if it's a 73 2.4s!

[Brorag]

why stop at d-lithium, how about tri-lithium, or quatra-lithium? Has something to do with quantum theory. The answer, though, is 42.

[dentist90]

I know my 84 can do in excess of 175mph with the stock motor. All I have to do is drop it out of an airplane.

[billybek]

Originally Posted by Brorag

why stop at d-lithium, how about tri-lithium, or quatra-lithium? Has something to do with quantum theory. The answer, though, is 42.

So long and thanks for all the fish!!
190 MPH!??
If I am ever going that fast in a car, you know I seriously f***ed up!!!

[wastintime]

Originally Posted by 74911

My (distant) memory of college physics says that mass doesn't effect top speed - only the time need to get there.

sort of.... actually in this case it'd be irrelevant the problem here is more of a terminal velocity issue.

As for mass affecting top speed... lol, I may have only done high energy astrophysics research, but... I'm pretty sure the earth is moving at WELL over 190mph and it's way more massive than the 911 SC.

As for getting to 190... I think you're better off starting out in a more aerodynamically refined car like a 964, really stripping it out, and putting in an ungodly powerful motor. Plus it's stable enough you could probably keep it a narrow body car, just be really careful accelerating in the low gears... If you don't have flares for air to build up on you'll have an easier go at it. I'm sure it'd be fun, but probably an ultimately pointless excersise.

[Wil Ferch]

I posted on this topic before...do a search under this topic and my name.

A good reference is ( for example) my own nearly stock 85 Carrera. It's geared ( nicely) to hit redline at top speed ( ~ 150 mph) in 5th gear. Factory says 207 HP or so.

Wind resistance goes up with the square of speed and the HP required to overcome this wind resistance goes up with the cube of speed.....

so.......

( 190 mph / 150 mph) * cubed... (x 207 hp) = 420 hp ( +/-).

Pretty much the consensus here.


LATER EDIT...pretty frightening about the amounts of HP required. It takes as much to reach the first 150 mph as it does to increase the last 50 mph past 150 ( to get close to 200 mph). That's why it takes 950 hp to reach 250 mph. Frightening.

[RWebb]

What a drag it is [going fast]

apologies to the Rolling Stones