Hunter whilst I agree it's to do with gearing and aerodynamics, it also has to do with bhp on a like for like basis.

2 Bugatti Veyrons set up identically with regards gearing, aerodynamics and weight but with a 500 and 1,000bhp engine respectively will not reach the same Vmax in real world conditions. In the real world the 500bhp Veyron would run out of steam earlier because it has insufficient/ less power (bhp) to punch through the wind resistance created by the speed its traveling.

Taken from wiki:

Power

The power required to overcome the aerodynamic drag is given by:

P_d = \mathbf{F}_d \cdot \mathbf{v} = \tfrac12 \rho v^3 A C_d

Note that the power needed to push an object through a fluid increases as the cube of the velocity. A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW). With a doubling of speed the drag (force) quadruples per the formula. Exerting four times the force over a fixed distance produces four times as much work. At twice the speed the work (resulting in displacement over a fixed distance) is done twice as fast. Since power is the rate of doing work, four times the work done in half the time requires eight times the power.

Therefore power is relevant

Cheers

Guy 2006 RRS S/C CONSTANTLY under modification...
1994 RRC 4.2l not LSE sadly gone but not forgotten
LR Defender 300Tdi - affectionately know as "The Black Beast"

Well obviously power is important..but you can have as much bhp as you like...if the gearing isnt right and the ADs its just not happening.... Gone but not forgotten, 2005 RRS SC first edition, BMW 2010 Z4,TVR Tamora, TVR Cerb, MERC SL 55 AMG, E46 M3, Z4, Jag S type R, Skyline R33 GTR 640 bhp, Evo FQ 400, L322 RR, X5, Lotus Esprit V8 twin turbo, Lotus Elise 135r, Nissan Murano, Honda S2000, 911, Boxster s...and a few more

If the gearing is sufficient then having "as much bhp as you like" does make a difference. That's the point!  2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

with the right gearing you could do it with little bhp...but you can have as much bhp as you like and if the gearing is wrong..its not going to happen... Gone but not forgotten, 2005 RRS SC first edition, BMW 2010 Z4,TVR Tamora, TVR Cerb, MERC SL 55 AMG, E46 M3, Z4, Jag S type R, Skyline R33 GTR 640 bhp, Evo FQ 400, L322 RR, X5, Lotus Esprit V8 twin turbo, Lotus Elise 135r, Nissan Murano, Honda S2000, 911, Boxster s...and a few more

Maybe you need all of them?

Maybe an improvement on any of them will improve max speed? '08 RRS TDV8
I converted my diesel RRS to run on an environmentally friendly mixture of caribou fat and baby seals oil

RRSTDV8 wrote:

If the gearing is sufficient then having "as much bhp as you like" does make a difference. That's the point!

hunter wrote:

with the right gearing you could do it with little bhp

Quote:

...but you can have as much bhp as you like and if the gearing is wrong..its not going to happen...

Gavin Beecham wrote:

RRSTDV8 wrote:

If the gearing is sufficient then having "as much bhp as you like" does make a difference. That's the point!

The point is that a rrs with standard gearing and 600bhp wont do 160. If it had 1000bhp it wouldn't do 160.
Hunters points are completely relevant.

If the gearing was raised, the aerodynamics and suspension uprated and with a long enough straight it would do 160. The point is it wont do that with a remap.
If the op can clarify what he has actually done and what his gearing is then the top speed at a certain rpm can be calculated.
And as Hunter has said, the difference between 147 and 160 is massive ( and massively expensive to achieve )

Well at least we're all agreed on that!
And that was the point I ( and I think Hunter ) was making!

The op must have thought he was still in the pub with his mates when he said his RRS could do 160

As I have my own engineering company I make ratio gear so I can modify any thing I want

Just to add I don't understand why the standard gearing won't manage 160mph... I'm not talking if the drive train can take it but if it theoretically can reach 160mph...

Now as my standard geared 2006 SC does approx 74mph at 2000rpm and the RRS is limited upwards of 5000rpm and the gear ratios don't change with speed, therefore a linear progression, 5000 divided by 2000 equals 2.5.

Therefore 2.5 x 74 = 185mph, therefore by my calcs the standard gearing does satisfy the requirements.

Now onto the matter of drag. The equation I found to calculated the power required to overcome drag is:

Power (W) = Drag force x velocity (m/s), where drag force is:

D = Cd x 0.5 x density of air (1.204kg/m3 at 20C) x velocity2 (160mph=71.53m/s) x frontal area (2.170x1.817m)

Therefore the equation is:

Power = (0.37 x 0.5 x 1.204 x 71.53 x 71.53 x 3.94) = 321,187 Watts

321,187W = 431 hp

Therefore, theoretically it's possible. But obviously this excludes the friction of the tyres on the surface, and aero buffeting (drag created through lift) etc...

But in principle 160mph is possible...

Cheers

Guy 2006 RRS S/C CONSTANTLY under modification...
1994 RRC 4.2l not LSE sadly gone but not forgotten
LR Defender 300Tdi - affectionately know as "The Black Beast"

 Current Volvo XC90 R Design T8
Gone 2010 TDV8. Stornoway Grey
Gone VW R50, AUDI S8, ML320 Sport, FFRR V8
Stolen 2007 TDV8.

Guyzer73 wrote:

Just to add I don't understand why the standard gearing won't manage 160mph... I'm not talking if the drive train can take it but if it theoretically can reach 160mph...

Now as my standard geared 2006 SC does approx 74mph at 2000rpm and the RRS is limited upwards of 5000rpm and the gear ratios don't change with speed, therefore a linear progression, 5000 divided by 2000 equals 2.5.

Therefore 2.5 x 74 = 185mph, therefore by my calcs the standard gearing does satisfy the requirements.

Now onto the matter of drag. The equation I found to calculated the power required to overcome drag is:

Power (W) = Drag force x velocity (m/s), where drag force is:

D = Cd x 0.5 x density of air (1.204kg/m3 at 20C) x velocity2 (160mph=71.53m/s) x frontal area (2.170x1.817m)

Therefore the equation is:

Power = (0.37 x 0.5 x 1.204 x 71.53 x 71.53 x 3.94) = 321,187 Watts

321,187W = 431 hp

Therefore, theoretically it's possible. But obviously this excludes the friction of the tyres on the surface, and aero buffeting (drag created through lift) etc...

But in principle 160mph is possible...

Cheers

Guy

speedy2009 wrote:

As I have my own engineering company I make ratio gear so I can modify any thing I want