top speed

[Hugh]

You prooved my point. So a CTSC NSX with 373 rwhp should be able at least 300km/h :wink:

No he didin't, he got his silly graphs from this web page where the author clearly states "The charts shown below are a product of my imagination, but are developed from data contained in car design text, aeronautical text and just plain guess work. Use the data at your own risk; your milage may vary."

The graphs are meaningless especially since there is no corresponding value associated with the little colored squares.

 

[Hugh]

I just took some lessons in physics :biggrin: and have calculated that the NSX (274bhp, 270km/h) would need to have 374 crank hp to achieve 300km/h.

I would love to see the formulas and data you used as well as knowing what hallucinogenic you were taking at the time.

 

[nsxtasy]

- How will larger/smaller wheels affect the top speed?

getting small tires would be equivalent to making your gears shorter thus making you accelerate better but also lowers your top speed. it usually doesn't make too much of a different. a .5 inch shorter or taller tire would usualy add or minus 6+/- mph on the top speed. ( well thats with the gearing on a 240sx ) i know on a nsx it would probrably be closer to 10mph.

getting taller tires would make your gear ratio taller which as i mentioned earlier would make your theoretic top speed higher but would make it harder to get there.

This answer is true with respect to the theoretical top speed at redline in the top gear. However, the top speed of the NSX is drag limited, not rev limited, so that effect is not relevant. I believe smaller tires will increase the top speed because they provide better effective gearing, and therefore more torque at the wheels, and similarly, larger tires will hurt.

Also, speedometer accuracy has been mentioned in this topic but not with respect to tire size. Tires whose outer diameter is different from stock will affect the accuracy of the speedometer. There are other factors which affect the accuracy of the speedometer (and even the effective gearing); for example, the difference in outer diameter between a new tire and one that is worn down to the treadwear indicator bars and ready for replacement is about 2 percent.

140 MPH on the front straight of Road America.

That straight (or just about any racetrack straight, with the exception of a high-banked oval or something miles long, like the Bonneville Salt Flats) is not long enough to test the top speed capability of the car. Quite aside from the fact that it's uphill. I'm sure you noticed that you were still accelerating as you approached the braking zone.

 

[MikeW]

No he didin't, he got his silly graphs from this web page where the author clearly states "The charts shown below are a product of my imagination, but are developed from data contained in car design text, aeronautical text and just plain guess work. Use the data at your own risk; your milage may vary."

The graphs are meaningless especially since there is no corresponding value associated with the little colored squares.

I did not use graphs... use your specs!

Hey Hugh, as you are the prof here why don´t you falsify my calculations with yours ? This is the usual way physicists do !

There is a lot of estimates in YOUR postings why should anybody believe YOUR theories without any proof ?

As for the values and formulas, I took them from here: http://www.rs-speed.de/html/modules/Tuning_FAQs/impressum20.htm

So instead of claiming other persons using drugs enlighten us with the reality :biggrin:

NSXtasy, my tires are brandnew: Front 215/40/17 Rear 275/35/18

Front:
Circumference: 1842mm
Static roll radius: 283mm
Dynamic roll radius: 293mm

Rear:
Circumference: 1982mm
Static roll radius: 304mm
Dynamic roll radius: 315mm

The speedo is very accurate with those tires. GPS prooved.

 

[Hugh]

I did not use graphs... use your specs!

As for the values and formulas, I took them from here: http://www.rs-speed.de/html/modules/Tuning_FAQs/impressum20.htm

So instead of claiming other persons using drugs enlighten us with the reality :biggrin:

I apologize, nsxsupra posted the graphs, not you. I'll run your numbers later this afternoon. I have to brush up a bit on my German to read the site you linked to though.

 

[nsxtasy]

my tires are brandnew: Front 215/40/17 Rear 275/35/18

Those rear tires are larger in diameter than stock - depending on what year NSX you have, by the following percentage:

'91-93 (225/50-16 rear tires stock): +2.9 percent
'94-01 (245/40-17 rear tires stock): +3.5 percent
'02-05 (255/40-17 rear tires stock): +2.2 percent

All else being equal (see below), the oversized rear tires make the speedometer and odometer read lower by the indicated percentage, and, as previously mentioned, also reduce top speed (and the rate of acceleration).

The speedo is very accurate with those tires. GPS prooved.

That's possible. As I previously mentioned, a lot of variables affect the speedometer accuracy, including the tread depth on the tires, as well as the fact that different makes/models of tires can vary in size, even when they are labeled with the same nominal size. If the speedometer is accurate with your oversized tires, then it's quite possible it would read high with stock-sized rear tires.

 

[TURBO2GO]

Someone explain to me if something is messed up with this thinking. When I hear "drag limited", to me it means "horsepower limited". Drag is so high that the engine HP cannot overcome it.

I think the NSX's top speed, especially a supercharged one, will be gear limited not drag limited.

Does anyone know what is the theoretical top speed acheivable in 6th gear at redline in a 6 speed NSX? That would be your top speed if you have enough power. And my gut feeling is that an FI'd NSX probably has enough to reach redline in 6th. What is that speed with stock wheels/tires and rear end? Can someone calculate this?

Also I am glad Gerard has posted a video with all this doubting going on... God only knows the grief he'd be getting without the Vid. That speedo looks burried to me.

 

[Gerard van Santen]

The extremely large air intakes on the front of the F360 play a vital role in the car's aerodynamics, effectively reducing it's frontal area and also channeling air underneath the car into the rear diffusers. At 180 MPH there is amost 400 lbs of downforce acting on a 360. Of course not many get to see 180 MPH because they've usually suffered a major mechanical malfunction or have self -incinerated.

A non CTSC NSX wil have little problem disposing of an F-360 on the street and especially on the track.

I am a bit confused now. First you say I am sort of a liar. Than you explain why an F360 can reach more than 182 m/ph with less hp than my NSX and you say that even a NON CTSC NSX will have little problem with an F360 on street and track .

Perhaps I am wrong. But if an F360 has more downforce than an NSX even 400 lbs at 180mph, it should be more difficult for an F360 to reach its topspeed than for an NSX with the same horsepower

And than you accuse MikeW is hallucinating and under drugs. You even accuse MikeW for things written by NSXSUPRA. Why is that?
I can imagine that you don't believe these written topspeeds. But why do you argue experiences from NSX drivers in such a arrogant way?

 

[Gerard van Santen]

Someone explain to me if something is messed up with this thinking. When I hear "drag limited", to me it means "horsepower limited". Drag is so high that the engine HP cannot overcome it.
I think the NSX's top speed, especially a supercharged one, will be gear limited not drag limited.

An OEM NSX is drag limited. Gear limitation will only occur with enough hp to reach the red line in highest gear.

Does anyone know what is the theoretical top speed acheivable in 6th gear at redline in a 6 speed NSX? That would be your top speed if you have enough power. And my gut feeling is that an FI'd NSX probably has enough to reach redline in 6th. What is that speed with stock wheels/tires and rear end? Can someone calculate this?

TURBO2GO, I am glad with with your words. Because with all the arguing going on I hardly dare to say that my NSX is gear limited with rear tires 275x35x18 which gives an almost accurate reading on my GPS like MikeW also experienced. That means that I hit the rev delimiter in fifth. I know someone will argui this, but this is truely what happened on a straight line with even my son next to me and a 1/2 full fuel tank. This means a straight line speed of more than 300 k/ph (OEM Ring and Pinion and almost new tires)

Also I am glad Gerard has posted a video with all this doubting going on... God only knows the grief he'd be getting without the Vid. That speedo looks burried to me.

Perhaps I photoshopped the video:wink:

 

[MikeW]

That's possible. As I previously mentioned, a lot of variables affect the speedometer accuracy, including the tread depth on the tires, as well as the fact that different makes/models of tires can vary in size, even when they are labeled with the same nominal size.

Yes, definitely !

If the speedometer is accurate with your oversized tires, then it's quite possible it would read high with stock-sized rear tires.

So we come to the question whether the speedo is inaccurate or the tires ?
With my tires, the speedo is a precision-instrument...:biggrin:, -it´s the tires!

Let´s assume a 91 stock NSX with stock tires achieve 275km/h then the speedo will show 282,96 (+2.9%). If he achieves 280km/h the speedo will show 288,12km/h. This explains the speedo experiences of some members who are with stock wheels.

 

[steveny]

Especially when you're high on Ecstasy. 300 Km/H is 186 MPH and there's no way on God's green Earth than a CTSC can provide enough horsepower to overcome the drag to push an NSX to those speeds.

These top speed threads are like fish stories. This is the age of high tech. If you're going to make a claim of top speed use a GPS and post the proof. Otherwise the post gets categorized under Internet Rule #1 which simply states "99.9% of anything posted on a message board is pure unadulterated bullshit."

This is an acceptable method of "proof"

Ah yes.... the old take the GPS unit on the learjet and then attach it to your motorcycle dash trick.:wink: :biggrin:

 

[Aurora]

My top speeds till now:

In the dry 112mph (Didn't have chance to visit Germany).
Under water 6 mph (Talk about bragging rights!)





Hey, look at the bright side. Under water you do not encounter speed bumps, traffic cops or traffic jams.:biggrin:


Roger

 

[MvM]

I cannot attest to the accuracy of the NSX speedometer. But I think it is well known that the top speed of the NSX is drag limited. I also know that on my tacho at least the car had no trouble to put 280 kph (174 mph) on it even when stock. Now I have some mods added to the car and I expect it to be just a little faster.
Just last Saturday I put 270 kph on the tacho for a short while and the car was still pulling. I just ran out of empty road and also my passenger started to get a little anxious.

 

[TURBO2GO]

Does anyone know this figure:

Top speed of a 6 speed NSX with stock rear and and tires, at redline. (assume there is enough HP or no drag).

 

[TURBO2GO]

Perhaps I photoshopped the video:wink:

Perhaps you did! Perhaps you are just like those scientists with fraudulent data telling us our activity is causing the planet to warm. :smile:

 

[Dan Ciezniewzki]

Perhaps you did! Perhaps you are all just like those scientists with fraudulent data telling us our activity is causing the planet to warm. :smile:

uhoh, i think you may have just opened a whole nother can o' worms

maybe we'll see al gores lame slideshows and graphs :tongue:

 

[steveny]

My top speeds till now:

In the dry 112mph (Didn't have chance to visit Germany).
Under water 6 mph (Talk about bragging rights!)



View attachment 28844

Hey, look at the bright side. Under water you do not encounter speed bumps, traffic cops or traffic jams.:biggrin:


Roger

Is there another thread with a story about this?

 

[lowellhigh79]

Assuming 3000 rpm will get you 70 mph, 8000 rpm will get you 186, a top speed requiring far more than the stock car is capable.

We have the power (677 rwhp) to hit over 200 but my car will be gear limited to 180 because of the stock rear tire diameter (both 295/30-18 and 225/50-16 are 24.8"), 4.44 final drive (OS Giken), and 8400 rpm.

Assuming stock rear wheel diameter (24.8"), stock ratio (4.06), and 9000 rpm with enough HP, 210 is the ceiling. Changing my rear to 295/35-18 PS2s (26.1 diameter) and raising rpm to 9000 will get me 203. The above changes and a stock 4.06 final drive should get us to 222. We hit 180 several times at El Toro while we were setting up the suspension.

Best Regards,

Danny

 

[jond]

Heres a NSX-R at the NurburgRing hitting pretty close to what seemed like its top speed.
Fast foward to around 7:00.

http://video.google.com/videoplay?docid=7014510364856677447&q=nsx&hl=en

 

[NSXGMS]

Does anyone know this figure:

Top speed of a 6 speed NSX with stock rear and and tires, at redline. (assume there is enough HP or no drag).

Isn't that the figure in the FAQ chart? It says 202MPH is the theoretical top speed based on gearing for a 6-speed.

 

[NSXGMS]

Heres a NSX-R at the NurburgRing hitting pretty close to what seemed like its top speed.
Fast foward to around 7:00.

http://video.google.com/videoplay?docid=7014510364856677447&q=nsx&hl=en

From above:

...just about any racetrack straight, with the exception of a high-banked oval or something miles long, like the Bonneville Salt Flats) is not long enough to test the top speed capability of the car...

 

[TURBO2GO]

Isn't that the figure in the FAQ chart? It says 202MPH is the theoretical top speed based on gearing for a 6-speed.

If this the case and the coefficient of drag for an 02+ is 0.30, with a CTSC at around 360-370RWHP I think 190 is a reasonable number and I believe Gerard's speedo to be fairly accurate.

Some of the R parts are increasing downforce but probably doing nothing for the Cd, like the R spoiler and the R hood. That may explain Vance's limited top end. He is not supercharged and is just running out of power.

Gerard has said 300KPH with the Comptech supercharged engine and I have no reason to doubt him, this is with a WIDEBODY mind you, I am not sure if he was running that massive rear wing, I would be shocked if he was.

I am pretty confident just by what I have seen that an 02+ and a CTSC can hit 190 given enough room. Not that I ever want to see that speed personaly. One mistake and you are for sure dead.

 

[Gerard van Santen]

Gerard has said 300KPH with the Comptech supercharged engine and I have no reason to doubt him, this is with a WIDEBODY mind you, I am not sure if he was running that massive rear wing, I would be shocked if he was.

I have to clearefy this. That speed I reached before my conversion to a widebody and without this rear wing. But with CTSC and CT headers, testpipes, CT Supertrap exhaust and Gruppe M intake. The rear tires I used where almost new SO3's 275x35x18. These tires gives you an almost accurate speedo.

 

[Gerard van Santen]

If this the case and the coefficient of drag for an 02+ is 0.30, with a CTSC at around 360-370RWHP I think 190 is a reasonable number and I believe Gerard's speedo to be fairly accurate.

This is a chart of a speedometer test I did with my NSX. As you can see the speedo is very (prooven) accurate. The real km p/h is sometimes more. This is with the wheels and tires I mentioned before.

 

[TURBO2GO]

Gerard, what is the "measured speed"? measured how?