Top Speeds in Different Gears (6MT)

Originally Posted by kannibul

Wrong. Moon has no air to resist. Dyno has no wind resistance. On the moon, the car would go as fast as it can barring friction losses with the brakes, drivetrain, front wheels, bearings, etc (provided it could breathe), and rolling losses (ie, tires). On a dyno, it'd go nearly to the theoretical limit, the difference being the same as on the moon, except without the front brakes/wheels being factors. Of course, I'm discounting gravity effect and lack of air for the moon.


So, let my try again:

You're driving along at 75MPH, 0MPH headwind. Your car is using (example) 65HP to perform this work.

You're driving along at 75MPH, 20MPH headwind. Your car is using 65+N HP now, because there is more resistance.

(You can change these numbers to driving at 75, with a 75 mph tailwind vs 75 with a 0mph wind)


Same effect applies when attempting to determine the maximum speed fo the vehicle. The faster you go, the more resistance is applied to the front of the vehicle.

As you increase speed, you increase air resistance. Lower drag coefficient means the car slips/cuts through the air more instead of creating turbulence which distorts the air, making it more resistant.

Imagine a biplane wing on a F18. It wouldn't got as fast...ever, given all things being equal.

Originally Posted by G37Sam

Wrong again, you're arguing a different point than I am

What I'm trying to say

If you're @ 4k rpm on 4th doing say 100mph, you will do that irrespective of any other forces, for the rear wheels to do 100mph, your engine has to be at 4k rpm if in 4th, it's how the car's gearing has been setup. Air resistance aka drag force only affects how much TQ you'll need to get there i.e how much time I'll take you to get there, but once you're there, you will be doing 100 @ 4k rpm.

Take it easy guys I only said on the moon because I wanted to use the 0 air resistance factor, of course the cars won't move there lol

Originally Posted by cjof2003

Forgive me if i'm wrong or off, as I don't know that much about the 370z, 
but with my napkin math, I get these results.

- 7500 redline
- 18" Rear Tire Size (non-sport): 245/45WR18
- 19" Rear Tire Size (sport): 275/35WR19
- 19" Rear Tire Size (Nismo): 285/35YR19
- Gear Ratios:
      6MT         7AT
1st:  3.794       4.924
2nd:  2.324       3.194
3rd:  1.624       2.043
4th:  1.271       1.412
5th:  1.000       1.000
6th:  0.794       0.862
7th:  N/A         0.771
FD:   3.692       3.357



Gear      6MT/6MT Sport      Nismo       7AT
1st               41mph      42mph     35mph
2nd               68mph      68mph     54mph
3rd               97mph      98mph     85mph
4th              124mph     125mph    122mph
5th              157mph     159mph    173mph
6th              198mph     200mph    200mph
7th                 N/A        N/A    230mph (229mph for sport)

Originally Posted by G37Sam

Wrong again, you're arguing a different point than I am

What I'm trying to say

If you're @ 4k rpm on 4th doing say 100mph, you will do that irrespective of any other forces, for the rear wheels to do 100mph, your engine has to be at 4k rpm if in 4th, it's how the car's gearing has been setup. Air resistance aka drag force only affects how much TQ you'll need to get there i.e how much time I'll take you to get there, but once you're there, you will be doing 100 @ 4k rpm.

Take it easy guys I only said on the moon because I wanted to use the 0 air resistance factor, of course the cars won't move there lol

Originally Posted by 370Zsteve

Resistance from the air will flatten those numbers as speed increases in 5th and 6th. The Z has nice drag coefficient spec, nonetheless physics will take over eventually.

Originally Posted by kannibul

Also, it looks like we should be dyno'ing the car in 5th gear?

Originally Posted by GTRFAN

I've been saying this all along on other threads. The only problem with using 5th is running into the speed limit of the rollers on the dyno. Some dyno's only support 200km/h, so using 4th is the only option to keep the speed down. (shoud only vary by a few kW anyway.)

my 2c