ctsc top speed?

[MvM]

Bigger rims would likely slow you down, as there will be more rotating weight, and therefore more parasitic power loss in the system. Lightweight 15/16's would be the ticket for high speed....

I am not so sure about this.
While the OEM 15/16 and 17/17 wheels are relatively light and so are OEM sized tires, the wheels are also much further inward relative to the body of the car.
AFAIK, the rolling resistance of tires goes up to a certain point and then remains at that point.
With bigger tires and larger wheels which are offset in such a way that the outside is in line with the wheelw wells you should have less eddies around those thereby reducing your wind resistance.

Wide body kits and/or parts thereoff increase the frontal surface of the car thereby increasing wind resistance even if the CD-value of the car would be the same.
Any part on the car that would create any significant downforce at high speed should normally reduce your top speed. I'm not sure if this works the same for parts that will increase downforce by just reducing lift.
Looks to me like, for example, the NSX-R undercover would actually help achieving higher speeds because it just reduces lift.
This is only true of course if your top-speed is drag-limited and not power or gearing limited.

 

[Wheelman]

with the power say (400 hp) what mph does the gearing run out, 180-190?

 

[nsxotic911]

I think there is a flaw here somewhere in your statement, 17, 18, or 19" wheel it doesn't matter because the overall diameter is usually the same.. the tire is lower profile. I don't think anyone is dumb enough to put wheels/tires that actually change the gear ratio of the car by that much. If that was the case, then yes you are right... but don't forget everyone keeps the overall diameter the same.

Good point.. should have thought of that

 

[nsxotic911]

with the power say (400 hp) what mph does the gearing run out, 180-190?

Based on previous discussion 400 HP/350RWHP should do abuot 180 assuming your Aerodynamics aren't screwed up..

 

[goldNSX]

Any part on the car that would create any significant downforce at high speed should normally reduce your top speed. I'm not sure if this works the same for parts that will increase downforce by just reducing lift.
Looks to me like, for example, the NSX-R undercover would actually help achieving higher speeds because it just reduces lift.
This is only true of course if your top-speed is drag-limited and not power or gearing limited.

It would be interesting to have an aerodynamic specialist to have all this explained.
AFAIK there's a trade-off between top-speed and downforce (or in most other of the cars less up-force). You can not have both at the same time, all else (power) the same. As there's no such thing as a free meal the downforce created by a diffusor and a flat underbody must be feed too.

F1 cars have different aerodynamically designs from race to race, in some races they are able to run 350 kph (Monza) in others it's only 300 kph (Monaco).

Some cars like the first Audi TT had to be aero-modified as it was not safe (too much uplift) at high speeds.

 

[lowellhigh79]

525 sounds a little high Danny. Gerard said the car had more to go at 182. Thats with a CTSC. I think the real answer is that a CTSC NSX should do about 185-190 top speed.

Hi Dave,

I agree that 525 rwhp sounds high; I was just going with the 350rwhp=180 mph starting point. Actually, if 240 rwhp (stock NA1) can get you 167 mph, 360 rwhp (240 x 1.5) should get you 184 (167 x 1.1), and 540 rwhp (360 x 1.5) should get you 202 (184 x 1.1) mph. Remember, this is jus a ball park way of anticipating top speed requirements. FYI, I remember this from a C&D article about top speed runs in a F-body Firebird.

Regards

Danny

 

[RAVN NSX]

How are you coming up with 180+ mph?

If you do the conversions and the math, he's only hitting 175.22 mph.

I've checked on a couple of sites and did the math:

1.00000 Kilometer = 0.62137 Miles

282 km x .62137 = 175.22634 mph

 

[AdnanVCS]

Here is a good site: http://www.metric-conversions.org/length/miles-to-kilometers.htm

 

[TURBO2GO]

Gerard's 282 was just the one on the video. He said he has done over 300KPH and I have no reason to doubt him. That's over 187 MPH.

 

[satx]

Not definite for sure, but somewhere in the back of my brain, I recall that you will need 50% more hp get get an additional 10% more speed once drag limited top speed has been achieved. Aerodynamics is THAT important. So if 350 rwhp will get you 180, 525 rwhp will be needed to get to 198.

Regards,

Danny

fyi.....a car that only requires ~230 rwhp to go 168MPH will do 200 with ~390 rwhp....appropriately geared of course.


The NSX is a very slippery car with it's low Cd and super small frontal area......actually it is one of the most aerodynamic cars ever built.

 

[satx]

btw....

here is a link to play with......I have found it to be very accurate.

http://www.rx7.org/Robinette/top_speed.htm

 

[TURBO2GO]

what is the Cd of an 02+ NSX? I think I read .29, is that right? that is very low. You'd think it would have less wind noise!

 

[TURBO2GO]

BTW Gerard has a widebody. I am not sure if the run was done with the widebody or not... that would be incredible if it was...

 

[nsxhk]

Well, for my old na1 with i/h/e, I have done 270km/h before, but just once and very brief. The car was still accelerating slowly so I think 280km/h is possible. It was scary and I don't think I want to do it again. The whole car feels like it's floating on air!

Henry.

 

[SaberX]

btw....

here is a link to play with......I have found it to be very accurate.

http://www.rx7.org/Robinette/top_speed.htm

Very cool. I put in 255 whp, 170mph old top speed. 344 new whp and it output 187mph as new top speed. So it looks like the CTSC should be able to run the car as fast as possible.

 

[spartan2-3]

what is the Cd of an 02+ NSX? I think I read .29, is that right? that is very low. You'd think it would have less wind noise!

I believe its .32

 

[TURBO2GO]

I believe its .32

I think thats correct for pre-02... I think the 02+ is less? anybody?

 

[sahtt]

I have a little first hand and a moderate amount of second hand experience regarding a similar situation regarding a different car, but not so different. The 90-96 [U.S] twin turbo 300zx also has excellent aerodynamic properties stock.

I took a small part in figuring out a stock, 300hp 300zx can reach 172.xx mph GPS stock. That was the average of going both ways, but there was only a slight difference because there was only a crosswind of about 4mph.

This is interesting because it closely resembles what an NSX can do.

A 300hp 300zx dynoes around 255whp. A 400rwhp 300zx attained a top speed, though only one way, of 186.xxmph. A 542whp 300zx attained a top speed of very close to the maximum allowed by the stock gearing, around 196 mph, by within 2mph. The last car I noted did not have the stock rear wing and was also lowered several inches, which surely helped the top speed a couple mph. There wasn't a huge supply of 600hp+ z32's in the area willing to expirement as you could guess.

The NSX attains a similar stock top speed with less horsepower, therefore it would be very conservative to assume a mid-high 3XXwhp NSX could do mid 180's and a 475whp, give or take, NSX could reach mid 190's, if not high 190's.

To find the true top speed of a car is actually quite simple, the only variables are power, drag, and gearing. Most equations include tons of other variables like weight, torque, etc. that make them at best speculative.

*as a side note, getting larger wheels than stock does usually increase the overall diameter slighly therefore giving a taller final drive. Going from all season 17's to low profile 18's may not make a difference, but certainly going with 19's in the rear, which is not unusual, will give you a slightly higher gearing, say a couple mph on each gear.

 

[sahtt]

Just for fun I did a couple calculations..

255->400whp is 145whp for a 186-172=16mph gain.
400->542whp is 142whp for a 195-186=9mph gain.

Given the better aero's of the last z tested, fits the mathematical equations almost perfectly.

 

[Coz]

isn't it's still a matter of gearing in the gearbox within the limits of the motor ? go faster sooner, have less top end.... and vise versa.
if geared correctly, amost anything could do 200 mpg under the right conditions. sort of thinking.....

having a ZF, we calculate ring and pinion teeth with various power loses through the drivetrain at the redline.
the gearing ratio and possible speed at redline is rhw max anything goes for that set up.
i always thought was pretty actuate as to determining top speed potenial...

yes, no ?

 

[sahtt]

isn't it's still a matter of gearing in the gearbox within the limits of the motor ? go faster sooner, have less top end.... and vise versa.
if geared correctly, amost anything could do 200 mpg under the right conditions. sort of thinking.....

having a ZF, we calculate ring and pinion teeth with various power loses through the drivetrain at the redline.
the gearing ratio and possible speed at redline is rhw max anything goes for that set up.
i always thought was pretty actuate as to determining top speed potenial...

yes, no ?

I don't think I fully understood your question, but I do believe you bring up a good point. People often think by getting a more aggressive gear ratio they are increasing acceleration but 'hurting' top end.

By say changing your final gear ratio from 4.10 to 4.77, you increase acceleration in all gears. So from a 100-120mph roll the 4.77 car will still beat the 4.10 car. However, if both had 1,000 hp the 4.10 car would have the higher top speed.

So as long as the gearing does not limit it, only_the horsepower and drag matter to calculate the top speed [drag includes friction caused by the tires so yes a 50 ton nsx will be slower than a 1.5 ton NSX]. Obviously if the gearing is too high the engine will be out of the powerband and won't make much power, so extreme cases don't work.

 

[lowellhigh79]

isn't it's still a matter of gearing in the gearbox within the limits of the motor ? go faster sooner, have less top end.... and vise versa.
if geared correctly, amost anything could do 200 mpg under the right conditions. sort of thinking.....

having a ZF, we calculate ring and pinion teeth with various power loses through the drivetrain at the redline.
the gearing ratio and possible speed at redline is rhw max anything goes for that set up.
i always thought was pretty actuate as to determining top speed potenial...

yes, no ?

At top speeds, the car is either gear limited or drag limited. Ideally you want to "match" the two at the same top speed. However, since top speed runs are almost never done in most cars, gearing a car to match the car's drag limits is unpractical. Most gearing is therefore slected for acclereation (lower gears) and mileage (highest gear) and the final drive ends up being a compromise between acceleration and mileage.

Although this topic is about CTSC top speeds, let me give you an example of gearing limitations. My 92 Red: 677 rwhp, 5 speed, 4.44 (OS Giken LSD), 295/30-18 rears, 8300 redline. My current top speed is gear limited to 178 mph and slamming into that top speed with plenty of acceleration still on hand doesn't change that fact. If I wanted to hit 200 mph, and assuming I don't want to change out my OS Giken to a 4.23 or 4.10, I will need to raise my rev limit to 9100 rpm (+9.6% = 195 mph) and change my rear tires to 275/35-18 (2.7% taller = 200 mph). All this, of course, goes counter to my current track setup.

Now going back to the CTSC top speed, it looks like the gear limit of a 5 speed (187) closely matches the drag limits of a CTSC NSX (184-187). Getting to 200 mph therefore will require, at the very least, another 7% increase in the driveline (ie raise rev limit to 8560 rpm) and an additional 100-150 rwhp.

Regards,

Danny

 

[pegi]

I think thats correct for pre-02... I think the 02+ is less? anybody?

Remebmer to read 91-01 was .32 and 02+- is .30.

But I found something info like this:

Cd (Drag coefficient): 0.32
Cl (Lift coefficient/overall): -0.100
Clf (Lift coefficient/ front): -0.040
Clr (Lift coefficient/rear): -0.060

Compared to the original NSX-R, this translates into an increase in vertical force acting on the front tires of 36.2kgf, and of 25.0kgf on the rear tires (test results measured at 180 km/h in both cases).
Lift reduction measures (effect measured piece-by-piece)

 

[pegi]

If you want to read intresting artictle about nsx-R, you could read it from here:
http://world.honda.com/NSX/

-pegi-

 

[scorp965]

This is in the FAQ:

[MYK - 99/10/8] I had a chance to ride Gruppe M equipped 91 NSX in Japan with Mr. Mamoru Ogose, the "M" himself on tiny little streets and on super smooth Tokyo freeway. Holly Shit! I used to drag race my 450 HP, Kenny Bell Equipped, and 11 second 1/4 mile running 87 Buick GN (Ran 22 - 24psi turbo boost) but the Gruppe M NSX with 5 psi felt much faster and had more torque than my ex-Modern Detroit Muscle.

His aggressive driving style and the power of the car instantly made me to say, DAMN! I gotta have this kit NOW!!! The car had 370ps (364HP to 366HP, I think) at 7300 RPM and it was running on the stock clutch. He said that the stock clutch is good enough for his ultra power kit. 370ps may not be enough for those of you like to compare NSX with new Porsche Twin Turbo but hey, if you get a chance to ride on this car...

Mr. Ogose claimed 4.4 sec for 0-60 mph and 12.7 sec for 1/4 mile or better. I think Alex has the Japanese Best Motoring Video with the Spec for this car in it. The video showed the top speed of this kit at 300 km/h or so (around 180 mph, I think)

I imagine the CTSC would be similar?