Top Speed

[greenberet]

Yep, in that picture of the speedometer with the needle past 180 mph, those are my hands on the wheel.

If you drive down a hill that can increase the speed you achieve a LOT. If you remove the .pdf ending of THIS FILE and open it with Excel, you can see about how much of a slope you need to achieve various speeds in an NSX. Driving with the wind is another way to go significantly faster than 168 mph in a naturally-aspirated NA1.

Here’s that video my NSX getting up to a GPS-measured two-way average top speed of 186 mph: http://www.youtube.com/watch?v=W5EmrML3p1U The fastest I have driven in only one direction is 304 km/h (189 mph), where the rev limiter seems to kick in on my NSX.

 

[nsxtasy]

If you drive down a hill that can increase the speed you achieve a LOT.
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Driving with the wind is another way to go significantly faster than 168 mph in a naturally-aspirated NA1.

Yup. That's why magazines remove this factor by using a level test course, with a two-way average to eliminate the effects of wind.

Unless you've got access to a high-banked oval, you'll also need a very long, preferably-straight (and preferably-empty) stretch of highway to test top speed. And by "very long", I mean several miles at a minimum.

 

[gsrboy]

This is the top of 4th gear in a turbo nsx (recall function, afterwards):

Highest is 189mph before running out of road; no picture of the peak recall, but the car had some rpm to go - some local owners saw the recall after the run.

Based on gearing alone, the car can reach 201mph with a 265/35/18 rear tire.

Off topic a bit scorp but can you set that cluster to read A/F from the wideband?

 

[NoelWatson]

180 on the speedo (on a 2004 and 2005 car) is around 165mph - the speedo overreads

 

[nsxtasy]

180 on the speedo (on a 2004 and 2005 car) is around 165mph - the speedo overreads

I've never heard of that before. The NSX's speedometer, at least on earlier year cars, is usually quite accurate.

Keep in mind that there are several things that can affect the accuracy of the speedometer. The difference in tread depth between new tires and ones that are worn down to the treadwear indicator bars is about 2 percent. And if you're using non-stock tire sizes, that can affect the accuracy of the speedometer by whatever the percentage difference is in the outer diameters of the tire sizes.

 

[sparky]

That car belongs green beret. ... that is in MPH. To top it off, his car is na.

that's very impressive. so greenberet can you give a brief summary of what you've done to achieve 300kph in an NA, including your torque curve above 7,000rpm. That is one of my (secret) long term goals, in an NA. :smile:

 

[heySkippy]

that's very impressive. so greenberet can you give a brief summary of what you've done to achieve 300kph in an NA

He did. Downhill with a tailwind.

 

[sparky]

He did. Downhill with a tailwind.

you must have skipped over post #51 where greenberet said he did two runs in opposite directions, averaging over 300 for the two.

 

[captainjman]

My top speed was on a very long entrance ramp to the tollway. There is no real speed limit there, just a suggested speed limit (per the rules of the road handbook).

Well, it says 35, but its just for reference-

I hit 7900 in 2nd, I hit 7800 in 3rd, and about 7000 in fourth before I hit the highway and slammed on the brakes to slow down to 100.

Not sure how fast I went, I didn't look at that. Do we have any engineers here who can tell me based on my RPM's on stock tires in a 97 3.2L - just how fast that was?

My overall top speed was in a Ferarri 512M - same expressway but 17 years earlier. It was 3am and we rocketed to just around 200mph and stayed at that speed for about 20 miles. We were out of fuel after the run. But what a rush.

Good times

 

[sparky]

put it this way ... 8,000rpm in 4th (with a 5 speed gearbox) is a tad over 140mph ...

 

[sparky]

it always amazes me how hard a car has to work to get to top speed. v. impressive!

 

[arfnsx]

I did a high speed run on a 2 mile airfield down in Miami. It was a standing mile run (much like the Texas Mile) (1 mile to run and 1 mile to slow down)

From a standing start, I got up to 170+ mph at the end of 1 mile. I was boosted running at the time about 380whp. Right now I am about 480whp and I would like to see what I can do. I believe I car should be able to hit about 183-185mph top speed. I would like to get to another runway to find out.


<iframe width="480" height="360" src="http://www.youtube.com/embed/GrDIY8JUmjM" frameborder="0" allowfullscreen></iframe>

 

[greenberet]

...can you give a brief summary of what you've done to achieve 300kph in an NA...

When the video with the 300 km/h two-way average top speed was shot and when my NSX got up to 304 km/h on a one-way run, the car had the following modifications:

Engine modifications:

• Comptech airbox
• Unifilter foam air filter
• Extrudehoned intake manifold
• Comptech ported and polished cylinder heads
• Comptech high-lift camshafts
• Cantrell headers with ceramic coating
• HKS muffler
• Autothority engine management chip custom programmed with car on dyno

Aerodynamic modifications:

• Homemade complete front and rear undertrays
• Homemade air dams in front of all four wheels
• Dali 2002-2005 OEM trunk lid spoiler replica
• Bilstein dampers that lower the car about 2 cm
• Procar Specials front blinker covers (mounted temporarily with duct tape)
• Homemade Styrofoam plugs for air conditioner openings in nose of car (temporary)

When the picture in post #42 and my avatar pic were shot back in 1999, my car got up to an indicated 8000 rpm in one direction on the Autobahn and 8050 rpm in the other. With the 245/40 17 rear tires the car had back then, that should have been just under 300 km/h factoring in tire slip, tire wear, etc. Back then, the car had the same engine modifications it has now except for ceramic coated Comptech headers instead of ceramic coated Cantrell headers. Aerodynamically, the car was completely stock back then except for Eibach springs and homemade Styrofoam plugs for the air conditioner openings in the nose of the car.

...including your torque curve above 7,000rpm.

I didn't do a before/after dyno test on the same dyno on the same day measuring the engine rpm from the tachometer pickup loop in the engine compartment so I don't have any reliable dyno figures. I'd like to know myself what my car's torque and power curves really are.

and ... is that light telling us the TCS is off ?

I'm afraid so! With 255/40 17 rear tires, my NSX runs into a speed limiter at 282 km/h (175 mph) if the traction control is on. If I turn it off I can go faster and the TCS failure light comes on instead, like in my avatar pic.

 

[nsxtasy]

I hit 7900 in 2nd, I hit 7800 in 3rd, and about 7000 in fourth before I hit the highway and slammed on the brakes to slow down to 100.

Not sure how fast I went, I didn't look at that. Do we have any engineers here who can tell me based on my RPM's on stock tires in a 97 3.2L - just how fast that was?

I'm not an engineer, but I can use a calculator. As noted in the wiki, the six-speed does 130 mph at redline in fourth gear. So at 7000 RPM, it's going 7000/8000*130=114 mph.

 

[sparky]

I'd like to know myself what my car's torque and power curves really are.

you probably have a pretty good idea already, but here's figures calculated by my reasonably comprehensive model of NSX performance using MATLAB.

To get an stock NA1 NSX (other than engine) to 300kph (186mph). I did this by simply multiplying stock engine torque curve by a percentage (since top speed is driven by power at high revs I reckon this is a valid assumption for this exercise):

required increase in engine torque: 28% = peak 366Nm (270 ft-lb)
peak engine power: 259kW (352hp / 347ps)
rpm @ top speed = 7,730

speed to distance:
400m you would be doing approx 184kph
1km you would be doing approx 240kph
2km you would be doing approx 275kph
it then takes another 3km (approx) to get close enough to top speed.

but all the above uses stock NA1 Cd (0.32). Given you modified your air dams and undertrays etc you probably reduced your Cd quite a bit, which would allow you to get to 300 with less power.
Using same model with Cd = 0.30 (which is what NA2 achieved by mods similar to yours)
required increase in engine torque: only 21% = peak 346Nm (270 ft-lb)
peak engine power: 245kW (333hp)
rpm @ top speed = 7,745

It's interesting how valuable Cd improvements are for top speed, especially since some Cd enhancements are way cheaper than engine power increases! Another contributor would be the car lowered by 2cm = less frontal area = reduced Cd x A (although I still used the stock 1.78 square meters in the model).

On another note ... I'm wondering how "drivable" your NSX is around town with the high lift cams? Are these cams still available to buy? how big a job was it, do they just drop in? I assume you need to retune / aftermarket ECU?

 

[Sumeronthechain]

I've never heard of that before. The NSX's speedometer, at least on earlier year cars, is usually quite accurate.

I can attest to this. I have a picture of the speedo at 162 or so and a GPS claiming a top speed of 163.

 

[greenberet]

... I'm wondering how "drivable" your NSX is around town with the high lift cams? Are these cams still available to buy? how big a job was it, do they just drop in? I assume you need to retune / aftermarket ECU?

With the Comptech camshafts, my car is still perfectly drivable around town. I think Comptech left the low lift cams as they were and just reworked the high lift cams. So below 5800 rpm there’s no difference to stock.

Comptech still has the design specs for the camshafts but I don’t think they offer them as a regular product anymore. I think they’d need to have some custom-made and I don’t know if they can have just one set of camshafts made if you want some. They may need to do a production run of several sets.

When I had the engine work done in 1995, my cylinder heads and airbox were sent to Comptech in California. After the parts came back and the engine was put back together and reinstalled into my car, I started it up to drive to an engine management chip programming company. I barely touched the throttle and kept the revs very low the whole way. Despite that, the check engine light came on almost immediately. Stopping the car and starting it again didn’t help. With the mechanical modifications and the stock engine management chip, I immediately got a check engine light. After having a new engine management chip custom-programmed with the car on a dyno, the check engine light once again only comes on if something is wrong. So I’d expect that you would need a retuned engine management chip or stand alone EMS if you installed new camshafts.

 

[sparky]

When I had the engine work done in 1995...

wow, you were an early upgrader! Have you had the same NSX all this time?

thanks for info, those high lift cams seem like a very effective mod, especially the way you've described. Food for thought!

 

[greenberet]

Yes, I’ve had the same NSX all this time. I bought my NSX in the summer of 1994, had the engine modified in the winter of 1994/95, and have put about 100,000 trouble-free miles on it since then.

 

[sparky]

that's impressive NSX loyalty ... and reliability!
why don't you have a kph speedo? (I'm guessing you brought it new in europe)

I had an amazing holiday in Germany in 1985 when I unexpectly got to drive a Porsche 930 turbo on the autobahn. I think I only did 220 that day but that was more than enough to trigger my healthy addition to quality performance cars ...

 

[greenberet]

No, I didn’t buy my NSX new. I bought it from the first owner in the States while I was going to grad school there. When I was done with grad school, I went on a road trip from the East Coast to the West Coast and back again. In Montana, I noticed a kind of speed limiter when the tachometer showed about 175 mph (the daytime speed limit was simply “reasonable and prudent” back then. Flat out in an NSX on a straight stretch of highway seemed reasonable and prudent enough to me). In New York, I put my US-spec NSX on a boat and shipped it to Europe as moving goods.

After picking it up in Bremerhaven, I took it to the Autobahn heading home and noticed the same speed limiter at an indicated 175 mph. After lots of searching it turned out to be in the traction control system.

Oh, and I forgot – the 100,000 miles have not been trouble-free. While the first half of the video in post #51 was being shot, the harmonic balancer failed. That’s why I short-shifted on the second half of the run. The balancer wore a hole through the timing belt cover and I’m really glad that’s all it did. It could have trashed my engine!

 

[costa]

Hey guys this car magazine just finshed last weekend doing a article on my car and would be outs some time next month i ran (all times were done with v-box) quarter mile 11.4 @215km(135 milles) without NOS just supercharger and 0-1000m (1km) my trap speed was 295km(184 milles)
that wasnt at cutoff so im shure there is plenty more if i remeber correctly 500-600rpm more on 5th gear

 

[sparky]

... just supercharger and 0-1000m (1km) my trap speed was 295km(184 milles)

holy sheeees!

 

[nsxtasy]

Yes, I’ve had the same NSX all this time. I bought my NSX in the summer of 1994

:biggrin:

 

[scorp965]

Off topic a bit scorp but can you set that cluster to read A/F from the wideband?

Yes, Stack offers a wideband option for their MFD cluster, the ST996.

Their newer generation clusters have an integrated g-sensor, and can also interface with CANBus; there are now options for a video logger, and GPS lap timer module, all of which can be synced to the data recorder for lap analysis.