Theoretical top speed
 

Has anyone been crunching numbers to determine a theoretical top speed based on Gearing ratios, available power, aerodynamics, vehicle weight, rolling resistance, available torque, ect. I don't really have much experience working with vehicles as most of my experience in such matters pertains to things in the air.

When you say theoretical top speed with available power and torque... Do you mean STOCK power and torque, or MAXIMUM potential? Also, do you mean stock gearing or what is available on the market that would MAX it out? Honestly, top speed depends on how much $$$ you have... You can make a FORD FIESTA fast with the right $$$.

I think he is referring to Stock all we know is its 155mph limited from what I have read so far

Weird. My NISMO hits 160 mph before the speed limiter cut off before I had it removed. Haven't tried again. But My guess 170mph is probably max the car can do.

The dude asked the same question in a different thread.

http://www.the370z.com/nissan-370z-g...-question.html

Not quite... I asked what people had actually obtained in the other thread... Here I'm asking what should be available bone stock from a theoretical standpoint.

Well, I did a little looking around by searching on Google. Found some people saying that the theoretical top speed is 170mph. But I don't know how reliable that info is. Like I didn't see anyone coming up with concrete evidence saying that they've done it on a track or anything like that. But more than one person said 170, so . . . I guess take it with a grain of salt?

Ok Grimm... I found the same info that Semtex got a hold of... I guess we should just wait a little longer and see what some of these members can do!

this video for 350z with VQ35HR it gets 260 KM/H
i think the 370z will be more by little dfferent
http://www.youtube.com/watch?v=tjFux...eature=related

if you could get 6th gear up to 7500 RPMs the theoretical top speed while in 6th gear would be 195. This is based on Car and drivers specs for the 370z.

GEAR RATIO MPH PER 1000 RPM SPEED IN GEAR
I 3.79 5.4 41 mph (7500 rpm)
II 2.32 8.9 67 mph (7500 rpm)
III 1.62 12.7 95 mph (7500 rpm)
IV 1.27 16.3 122 mph (7500 rpm)
V 1.00 20.7 155 mph (7500 rpm)
VI 0.79 26.0 157 mph (6050 rpm) TOP would equal 195MPH in 6th

I did the math before in the other thread, but now I'll do it for 170MPH
(Again, assuming that the wind-speed is 0MPH!):

NOTE: I couldn't find the frontal surface area on the 370z, so I'm GUESSING it's around 1.9m^2. It could be less.

First figure out how much drag force there is:
F_drag = (Drag Coefficient) * (Frontal Area-meters) * (Volocity-Km/s)^2
170MPH = 75.99m/s
F_drag = 0.29 * 1.9 * 75.99^2 = 3181.74 N

Now we figure out the rolling resistance:
F_tire = (Vehicle Weight-Kg) * 9.8 * (drag_contribution)
F_tire = 1506 * 9.8 * 1.8% = 265.65 N

Now calculate how much power is needed to push against these forces:
P = F * V
P = 3447.39 * 89.42 = 308265.6138 Watts = 413HP


I double checked my math and it's right. I still think this is pretty high. Can someone find the REAL frontal area on the Z? I think that's making this number high.

Completely disregarding calculations, just talking from years of looking at car stuff... I think 413hp will barely get the z around the 175MPH range. I think we are going to need around 500hp to get into the mid 180's and then 650hp to reach 195-200MPH. Just an educated guess.

^^^ My Trans Am had 350HP and made it to 165MPH without a problem and it weighed 3500Lbs. Sorry, but 500HP is good for 190MPH. The Corvette Z06 with 505HP made it to 196MPH and it weighs about 3200Lbs.

500hp is no guarantee that you will hit 190mph. Gearing, co-efficient drag plays the biggest part. A truck with 500hp won't see near that. A car has to be very slick to make it to that speed as well.

^^^ The 370z has almost the exact same drag-co as the Corvette. The rolling resistance is about the same since the corvette has wider tires but weighs slightly less... 500HP doesn't GUARANTEE that the Z will make it to 190, but it's a good chance.

Yes, the Z06 is also designed aerodynamically to go that fast. The Z is not. I think that the Z will need more power to reach those speeds. When you get into the 180's, things like flat underpanels start making a big big difference. Also you're saying that 500hp will only possibly get it to 190mph. Those last 10MPH can very well take an extra 100hp from the engine..

I guess the only way to find out then is to see if one of the guys with 500HP is willing to push their car to the top speed. I'd put my money on it hitting 190.

I've been drag racing a LONG time and I can say confidently that a car with 500HP will *generally* reach 190, unless - as nizmoz mentioned - the car is shaped like a brick.

If the Z's drag-coefficient is nearly the same as the Corvette Z06, then the aerodynamics of both cars are going to play the same roll on drag. So that, in point, is moot.

Don't forget that wind drag for a car is a function of speed, frontal area, and the coefficient of drag. Although the corvette and Z may have similar coefficients, I would presume the frontal area on the Z is greater and will cause it have much higher wind drag. Wind resistance will increase exponentially as speed increases linearly and have drastic effects at high speeds.

Drag = .5(1.293 kg/m^3)(speed in m/s)(frontal area in m^2)(drag coefficient)

This formula is good at sea level with no wind.

That's exactly right. I couldn't find the frontal area, as I'd stated, so I used a slight guestimate that was just a little more than the Corvette's. It's REALLY hard to find the frontal areas, I see... LOL

I used 1.9sq meters as the frontal area.

But yes, no wind and sea level!. :)

176mph
 

Listen. All you forum ******** can come at me right after i post this. I have removed my speed limiter and geared out the OD on our car (6th gear)
Meaning 7500rpm in 6th gear. Gps said 176mph and it couldnt go any faster. My car makes almost 400ftlbs to the wheels so dont say im lying and full of **** and a forum noob. Thanks for playing.

Do you have a turbo or supercharger to get that much torque?

You were 7500rpm in 6th gear going 176mph?

Choose one:
[ ] Clutch was slipping the entire time
[ ] You installed 23" diameter rear tires (3.5" shorter than stock)
[ ] You installed ~4.25 final drive gear
[ ] Tires were spinning the entire time
[ ] Inaccurate Story

7500rpm in 6th gear with either 6MT or 7AT would be over 200mph with stock gearing and tire diameters if you had the power to reach it. Aside from the basic math not agreeing with you... I have gone faster than 176mph in car the and it did not require 7500rpm to do this.

Toys out of pram ???

Language .. tsk, tsk, tsk ......

Only one way to find out, someone hop it there car and go do it. I've been 150mph in mine on a few occasions, nothing out of the norm, but also owning a SRT8 with way more TQ it just seems like an eternity to get to those upward speeds which seems so relatively easy in the SRT. I have a stretch of road that it can be done in, if it can be done, but I guess only time will tell.

we have a section of h/way in Australia NT no speed limit.
during winter last had car to 260kph - about 155mph in old money.
dont ask me what rpm's as I was too busy looking for kangaroos and eagles not to hit - and the occasional pot hole....roads are pretty rough.
speed limiter removed.
i use GPS sat nav that gives me speed indication...helpful at eyelevel.
6MT all bolt ons and uprev tuned.

I did 160. My car just has Gen 3's

OP, yes I looked at it. For all intensive purposes your looking at the high 170s low 180s for top speed. But that assumes alot, you have extremely long flat road, no wind, 70deg F temp, minimal difference between the steel wheel of a dyno and the asphalt of a road, and an accurate dyno.