gear ratio calculation

[jaffaz32]

i am wondering if anyone can tell me how to work out what speed i should be doing with different gear ratio's. i.e. changing final drive.

For example at 3,000 rpm in 5th, what speed does everyone do in a US spec Nsx? Compared to a UK? Compared to changing the final drive?

More out of curiosity if anything.

Thanks.

 

[TyraNSX]

Read the wiki????

 

[nsxtasy]

Read the wiki????

Yes, exactly. And you can interpolate/extrapolate where needed. The calculations are basic math.

For example at 3,000 rpm in 5th, what speed does everyone do in a US spec Nsx?

Since the wiki notes that you do (a theoretical) 186 mph at 8000 RPM in fifth, you would be doing 3000/8000 * 186 = 70 mph at 3000 RPM in fifth.

Compared to a UK?

As noted in the wiki, the Euro spec NSX is geared the same as the North American one.

Compared to changing the final drive?

Again, you can interpolate/extrapolate. Since you're doing 70 mph at 3000 RPM in fifth with the stock 4.062 R&P, if you switch to a 4.55 R&P, you will be doing 4.062/4.55 * 70 = 62 mph at 3000 RPM, or you'll be doing 70 mph at 4.55/4.062 * 3000 = 3360 RPM.

 

[SFNSXguy]

FYI if you do the 4.55 R&P (assuming a stock 3.0 engine) the top speed of the car will still be aerodynamically limited to 168 mph -- though you'll be turning higher rpm.

 

[jaffaz32]

Yes, exactly. And you can interpolate/extrapolate where needed. The calculations are basic math.


Since the wiki notes that you do (a theoretical) 186 mph at 8000 RPM in fifth, you would be doing 3000/8000 * 186 = 70 mph at 3000 RPM in fifth.


As noted in the wiki, the Euro spec NSX is geared the same as the North American one.


Again, you can interpolate/extrapolate. Since you're doing 70 mph at 3000 RPM in fifth with the stock 4.062 R&P, if you switch to a 4.55 R&P, you will be doing 4.062/4.55 * 70 = 62 mph at 3000 RPM, or you'll be doing 70 mph at 4.55/4.062 * 3000 = 3360 RPM.

I did have a look at the Wiki but was hoping for the information above at 3000 rpm. Thanks!!!

 

[jaffaz32]

FYI if you do the 4.55 R&P (assuming a stock 3.0 engine) the top speed of the car will still be aerodynamically limited to 168 mph -- though you'll be turning higher rpm.

That's very interesting.

That explains a few things.

So does the 3.2 have better Aerodynamics to allow it past 168?

What is the main factor that allows the higher top speed of the 3.2 if that is the case? the bumper? there isn't much else visually i could see that may affect the Aero as the lights surely are the same when they are down on the NA1's. Ok the Bonnet is slightly different but surely that isn't for Aerodynamics but to Accommodate the fixed lights?

The rear is slightly different but i would imagine it's the front that restricts the top end.

 

[Honcho]

That's very interesting.

That explains a few things.

So does the 3.2 have better Aerodynamics to allow it past 168?

What is the main factor that allows the higher top speed of the 3.2 if that is the case? the bumper? there isn't much else visually i could see that may affect the Aero as the lights surely are the same when they are down on the NA1's. Ok the Bonnet is slightly different but surely that isn't for Aerodynamics but to Accommodate the fixed lights?

The rear is slightly different but i would imagine it's the front that restricts the top end.

Aero.

 

[nsxtasy]

FYI if you do the 4.55 R&P (assuming a stock 3.0 engine) the top speed of the car will still be aerodynamically limited to 168 mph -- though you'll be turning higher rpm.

Not true. If you do the 4.55 R&P, the top speed of the car will be rev limited, not drag limited; it will top out at 166 mph at redline (8000 RPM).

 

[SFNSXguy]

Not true. If you do the 4.55 R&P, the top speed of the car will be rev limited, not drag limited; it will top out at 166 mph at redline (8000 RPM).

What a HUGE difference... You're sure it's not 167.789? :biggrin:

EDIT: I guess what I should have said is that "regardless of the R&P ratio, a stock NA1 will still have a top speed of 168 mph (though keN's calculator says somewhat less)."