How many horsepower?

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  • #1
Nissan Jon
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Salutations,

I specialize in high performance solutions for Nissan vehicles. I've recently gotten into the top speed Texas Standing Mile competitions. The current champion is using a Ford GT with unknown power to set the record at 274 MPH from a still launch; I want to beat his record.

I will be using a 2007 Nissan 350z, which will be engine swapped from the VQ35DE motor to the VK56DE. This will bring my current 3.5L V6 to a 5.6L V8, which a twin turbo set up will be added. Now, my question is this: how much horsepower will it take to propel a (approximately) 3,400 lbs vehicle to 300 MPH from a stand still? I will try to optimally reduce the weight down to 3,000, and the target speed is 287MPH. What kind of engine figures will I need to be achieving to make that speed?
 

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  • #2
anorlunda
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You must specify how much time it takes to reach that speed before your question can be answered. 1 second -- impossible. 1 day -- a very small engine.

Another critical parameter, how many hp does it take to maintain a steady 300 mph?


The first question has to do with acceleration, the second with friction and drag.
 
  • #3
Vanadium 50
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how much horsepower will it take to propel a (approximately) 3,400 lbs vehicle to 300 MPH from a stand still?

Somewhere around 2000.
 
  • #4
NTW
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Assuming a frontal area of 1.5 m2, a coefficient of drag of 0.3 (a frequent value in sport cars) and an air density of 1.23, the power needed to keep the car moving at a constant 300MPH = 134 m/s against the aerodynamic drag would be:

Power = drag × airspeed ⇒ Power = (½ × 1.5 × 0.3 × 1342 × 1.23) × 134 = 665890 W = 893 HP.

And that, for air resistance only...
 
  • #5
Vanadium 50
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A bunch of ~20% approximations and you get 3 digits of precision?

The best estimator is the horsepower of cars that actually go at (or near) 300 mph. The five fastest production cars in the world average 260 mph at 1200 hp. If the only thing you were fighting is air resistance, 300 mph would take 1600 horsepower. Many of these "supercars" are more aerodynamic and lighter, which just adds to the power the OP will need.

I think it's unlikely he will be able to get 7x the power (or even 3x the power) out of that engine. I also think that even if he did, it's unlikely that the transmission will support the sort of torque needed to reach these speeds.
 
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  • #6
NTW
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To the aerodynamic drag, you must add the rolling resistance. The rolling coefficient for tires on concrete is around 0.012 Now, for a car with a mass of 3400 lb (1544 kg) the power needed to keep the car moving horizontally at 300 MPH (134 m/s) fighting just the rolling resistance would be:

Power = resistance × speed ⇒ Power = (1544 × 9.8 × 0.012) × 134 = 24330 W = 33 HP.

That, for rolling resistance only... Now, the drag-associated power required plus the rolling resistance-associated power required, is 33 + 893 = 926 HP. As there are other resistances, such as engine and transmission friction, and you would also need a power reserve of –say– 500 HP, taking all that into account, in the real world, you would need an engine of at least 1600 HP.

Or so...
 
  • #7
Nissan Jon
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The 1,600hp figure sounds about right, but, I assume, that's power to the ground?

I think I may not have been clear on certain important factors. One, the vehicle does not need to maintain 300mph, it must reach at least 280MPH within one mile, ideally 300. Getting a twin turbo V8 to 3,000bhp is actually fairly easy, on an open frame with nitro methane, alcohol, or 118 Oct. However, I will be cramming a lot of ducting into a much smaller street legal unibody.

The recorded holder, as I found out last night, is pushing about 2,000bhp, or roughly 1,500-1,600 whp, on his Ford GT. I assume I'll need something slightly north of this figure.
 
  • #8
NTW
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In my estimation, I accounted for the power lost to the transmission; thus, the 1600 HP is 'power to the ground', yes...
If you have to keep that speed of 300 mph, even for the fraction of a second, you'll need the 1600 HP, for that fraction of a second...

Good luck...
 
  • #9
Nidum
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@anorlunda said : question has to do with acceleration, the second with friction and drag.

+1

@NTW : You perhaps don't understand the difference between power needed to accelerate the vehicle and power needed to maintain a set speed .

If you have a simple trolley sitting still on a flat surface what do you need to do to make it move ?
 
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  • #10
anorlunda
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The 1,600hp figure sounds about right, but, I assume, that's power to the ground?

I think I may not have been clear on certain important factors. One, the vehicle does not need to maintain 300mph, it must reach at least 280MPH within one mile, ideally 300. Getting a twin turbo V8 to 3,000bhp is actually fairly easy, on an open frame with nitro methane, alcohol, or 118 Oct. However, I will be cramming a lot of ducting into a much smaller street legal unibody.

The recorded holder, as I found out last night, is pushing about 2,000bhp, or roughly 1,500-1,600 whp, on his Ford GT. I assume I'll need something slightly north of this figure.

Well, then you answered your own question.

Good luck.
 
  • #11
NTW
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@anorlunda said : question has to do with acceleration, the second with friction and drag.

+1

@NTW : You perhaps don't understand the difference between power needed to accelerate the vehicle and power needed to maintain a set speed .

If you have a simple trolley sitting still on a flat surface what do you need to do to make it move ?


Not the case here, since aerodynamic drag and rolling resistance should be taken into account.
 
  • #12
Nidum
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During acceleration of a vehicle some of the power delivered by the engine is used to increase the KE of the vehicle and some is used overcome drag forces on the vehicle .
 
  • #13
NTW
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The power mentioned above for opposing rolling resistance and the drag is the minimum power needed to accelerate the vehicle to 300 mph. That acceleration will start with a high value, and continuously decrease as the speed increases, till the target of 300 mph is reached asymptotically. If you wish a shorter time to 300 mph, you can always use the extra 500 HP also mentioned above...
 
  • #14
rcgldr
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There's a safety issue at high speed. That Mustang GT would need modified aerodynamics to keep it stable at 274 mph.

Here's an example of a RX7 on a Bonneville run, lifting the rear end at 215 mph, then flopping over onto it's hood (not a violent crash), the driver wasn't hurt. Skip to 2:10 into this video, and again to 3:45 (another run in another car, this time the car lifts the rear and/or the front end collapses and spins but doesn't flip).



Another issue is reaching 280mph in a standing start mile. The fastest production cars that can reach over 230 mph take 3 to 5 miles to do this.
 
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  • #15
Vanadium 50
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There's a safety issue at high speed

Ya think? :wink:

Clearly getting a car to go 300 mph at all is a huge challenge, and is a necessary but not sufficient condition for this race. One thing that hasn't been discussed is that getting a lot of power only helps you if you can turn the wheels faster. If it needs to go 12,000 rpm to hit 300 mph, you have a problem.

I'm a bit surprised at the twin turbo solution. The reason for a turbocharger over a supercharger is fuel economy, which is not a big concern here. The reason for a twin turbo over a single one is to reduce turbo lag. Again, probably not an issue.
 
  • #16
mheslep
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To the aerodynamic drag, you must add the rolling resistance. The rolling coefficient for tires on concrete is around 0.012 Now, for a car with a mass of 3400 lb (1544 kg) the power needed to keep the car moving horizontally at 300 MPH (134 m/s) fighting just the rolling resistance would be:

Power = resistance × speed ⇒ Power = (1544 × 9.8 × 0.012) × 134 = 24330 W = 33 HP.

That, for rolling resistance only... Now, the drag-associated power required plus the rolling resistance-associated power required, is 33 + 893 = 926 HP.
Which is the approximate rate work is done by drag and rolling friction on the vehicle, fair enough.

But the losses internal to the vehicle, the actual performance of the motor at its maximum rating over time at a given temperature, power of the heat rejection system, etc, are wild guesses based on the limited information here. Starting from the know HP rating of vehicles at high speed and extrapolating up, as V50 did, is the best approach with the given information. 2000HP @300mph. And some wings.
 
  • #17
mheslep
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The 1,600hp figure sounds about right, but, I assume, that's power to the ground?
No, less than 1000 HP to the ground. The rest is loss between the engine cylinders and the ground. Lots of heat.
 
  • #18
Nissan Jon
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Ya think? :wink:

Clearly getting a car to go 300 mph at all is a huge challenge, and is a necessary but not sufficient condition for this race. One thing that hasn't been discussed is that getting a lot of power only helps you if you can turn the wheels faster. If it needs to go 12,000 rpm to hit 300 mph, you have a problem.

I'm a bit surprised at the twin turbo solution. The reason for a turbocharger over a supercharger is fuel economy, which is not a big concern here. The reason for a twin turbo over a single one is to reduce turbo lag. Again, probably not an issue.

That's only partly true, and would only apply to inline turbo system on a large/small combination. A single sequential turbo can behave exactly like a twin turbo setup in that the inlet venturis can change diameter to alter charge speed at any given RPM. A twin turbo in this situation will be on isolated inlet runners, which doubles the total inlet charge. Two big turbos on independent inlet piping will double the volume of incoming air.
 
  • #19
Nissan Jon
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Aerodynamics will be the bigger hurtle, and is definitely the larger factor in this situation. The current record holder used the factory body for his record with no modification to its design. The Z33 that I'll be building isn't as aerodynamically tuned for high speed and the rear end gets increasingly lighter has the speed increases, which, of course, increases the likelihood of a roll over.

Boniville isn't the greatest example because they are running on loose lime and salt deposits, I'll be running on a retired airport runway; It's quite a bit safer.
 
  • #20
rcgldr
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Doing a web search, I found multiple articles stating that the current "claimed record" for standing mile by a "street" car is 283.232 mph by a modified Ford GT (about 1700hp, not sure if that's rwhp or engine power), but some groups dispute this.

Another Ford GT with about 2000 hp reached 278 mph at a Texas standing mile event. Video:

 
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  • #21
rcgldr
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I'm wondering what qualifies as a street car. There's a "street car" class for drag racing, one of which includes cars that are actually street licensed. The fastest ones are making 3000+ hp and reaching 250+ mph in 1/4 mile runs. The next step up are so called "door" cars that run in one of the "street car" classes, I doubt these could be street licensed, the fastest ones are reaching 270+ mph in 1/4 mile runs.
 
  • #22
Nissan Jon
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I'm wondering what qualifies as a street car. There's a "street car" class for drag racing, one of which includes cars that are actually street licensed. The fastest ones are making 3000+ hp and reaching 250+ mph in 1/4 mile runs. The next step up are so called "door" cars that run in one of the "street car" classes, I doubt these could be street licensed, the fastest ones are reaching 270+ mph in 1/4 mile runs.

For the Texas Standing Mile, 'street car' means street legal by the guidelines of the U.S. Department of Transportation, specifically: must retain all of its OEM saferty equipment (air bags, crash sensors, seat belts), running lamps, turn signals, and, I belive, it has to pass omissions.
 
  • #23
Nissan Jon
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Okay, I've got some new figures for you guys to crunch.

Curb weight: 3,145 lbs. (Will be ideally reduced to 2,900 lbs)
My weight: 190 lbs. (Will be ideally reduced to a sexy 175)
Drag coefficient: 0.30 (will be adding canards and adjustable rear spoiler for downforce)
Stand still launch to 5,280ft target.

Target horsepower: ideally 1,800 whp at the wheels?
 
  • #24
rcgldr
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I believe, it has to pass emissions.
This varies from state to state, but cars made or cars that resemble cars made before a certain year have no emissions standards. In California, the year is 1970, cars made before 1970 or (kit cars) that resemble cars made before 1970 can get a "smog waiver". I don't know what the rules are in Texas. As for one of the "street car" type drag competitions, the cars are actually driven (usually towing a small trailer) from event to event as part of the requirement, so those are licensed cars. I assume these cars are registered in the state with the most lax rules regarding "street legal" cars. In California, recent cars don't get an emissions test, the test stations connect to a port on the cars to check for any modifications to the ECU or out of spec readings from the ECU.
 
  • #25
gmax137
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Boniville isn't the greatest example because they are running on loose lime and salt deposits, I'll be running on a retired airport runway; It's quite a bit safer.

Is the timing at the Texas venue the exit speed, at the end of the mile run?

As I understand the Bonneville records, they time over a measured mile; for instance the time between mile 6 and mile 7 of the 12 mile course. The Bonneville times are really the computed speeds over a mile, not the instantaneous speed.

I watched the motorcycles run there one year, it was a lot of fun to see.
 
  • #26
rcgldr
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Is the timing at the Texas venue the exit speed, at the end of the mile run?
Unlike Bonneville, it's a standing start 1 mile drag run for speed (versus time).
 
  • #27
Nissan Jon
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Is the timing at the Texas venue the exit speed, at the end of the mile run?

As I understand the Bonneville records, they time over a measured mile; for instance the time between mile 6 and mile 7 of the 12 mile course. The Bonneville times are really the computed speeds over a mile, not the instantaneous speed.

I watched the motorcycles run there one year, it was a lot of fun to see.

Yes, your top speed is when you cross the trap line at the one mile mark.
 
  • #28
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I don't think this is calcuable. We don't know the tire friction at 300 mph (and what do you use for tires? My H-rated Contis would turn to dust at 300!) and we don't know the weight distribution on these tires, especially as aerodynamic forces become large.

That said, why are you messing with an IC engine? You could presumably use a Leaf instead of a 350Z, right? So why not just use a ginormous electric motor in your 350z? Lots of HP, lots of torque. You don't need a charger, so you could take that out. 2000 hp is 1500 kW, and the Leaf battery is 30 kWhr. That will give you 72 seconds of power. That sounds like not much, but if you need more than 72 seconds of power, you're not going to be making 300 mph after a mile. The technical question in my mind is whether it's possible (and wise) to drain the battery that quickly.
 
  • #29
mheslep
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Where does one buy 1.5 MW polyphase induction motors at a power density suitable for race car, ie 4 or 5 kW per kg? The beast would have to include some method of cooling the rotor, as does Tesla's much smaller motor.
 
  • #30
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Audi claims the electric drive in my A3 weighs 75 pounds. I believe it - it's a tiny little thing. It's limited to 102 hp, switching the engine on when it reaches that point because it can only run a few minutes at that level of power. An unreliable source (VW wouldn't lie, would they?) says it can do almost twice that. So that's well within the range you are discussing. Like I said, I think the bigger challenge is pulling that much energy out of a battery in a short time. You wouldn't want your car to pull a Samsung Galaxy at 300 mph.
 
  • #31
mheslep
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The battery ( and/or capacitor bank) would be purchased. I dont know of a commercial high power density 2000 HP e motor source.

Sure, the power density is doable, but with non trivial engineering and manufacturing chops. Tesla's motors for instance are 2.5 HP/lb (4kW/kg), and even higher power density is reportedly available, though these are built in the hundreds of HP range. Challenges include mechanical loads on the windings, with 200 lb-ft race car typical torque, and heat rejection when packing a lot of power into a small space, especially for the rotor. Guys like the OP have been machining high performance IC engines from scratch for a century. E-motors at 2000 HP and 3 HP/lb? Not that I know of. Dividing the load among multiple motors at 300 mph would present other challenges, like multiple gear boxes, and stable vehicle control.


Example GE 1.5 MW generator and gearbox, when high power density is not a design constraint:

0C9FABCC-CACF-B0B0-F1CD48C63AD088C7.jpg
 
  • #32
Nissan Jon
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Why mess with internal combustion? Because that's what I know. Why not electric power? Because I don't know anything about it. Lol
 
  • #33
Vanadium 50
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Because that's what I know.

That's actually a very good reason.
 
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  • #34
automotiveadam7
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I'm worried the amount of boost pressure necessary to generate said level of power would be too much for the stock motor. (assuming your engine, or the one you plan on purchasing is stock) From my knowledge of speed-machines, most cars running in the range you hope to achieve are running on 12+ psi, which few engines (apart from something to the likes of rb26s or 2jzs) can handle. At least for very long. Forged internals however, are always an option. Are you hard set on the vk56?
 
  • #35
Nissan Jon
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I'm worried the amount of boost pressure necessary to generate said level of power would be too much for the stock motor. (assuming your engine, or the one you plan on purchasing is stock) From my knowledge of speed-machines, most cars running in the range you hope to achieve are running on 12+ psi, which few engines (apart from something to the likes of rb26s or 2jzs) can handle. At least for very long. Forged internals however, are always an option. Are you hard set on the vk56?

Well, my shop represents Nissan motorsports, and I intended to stay with in the Nissan family. The only V8 option in the Nissan line up is the VK, however, as a testament to Nissan innovation, Nissan Supercar AU built a 714bhp Naturally Aspirated VK50, on almost entirely stock upper components and completely stock lower parts.

Now, I'll be far from stock. We'll be running primarily titanium parts, like: block sleeves, rods, pistons, ect., 320,000 psi head bolts, the works.

2,500 bhp is really easy to achieve, making it reliable is tricky, but cramming it all in a Z33 body will be the real challenge.
 

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