Power/Kg - transimission?

[MuRRe]

Just give me a rough idea how to calculate what to set max speed to after fully upgrading a car.
Wanna run the Lupo in B-spec, wanna have a good max speed so it doesn't take forever.

 

[CSLACR]

Depends on the car.
I've no idea what the power or weight of the Lupo is.

Give me those figures and I can probably give you a decent estimate if nobody beats me to it with tested specs.

 

[Famine]

Just give me a rough idea how to calculate what to set max speed to after fully upgrading a car.
Wanna run the Lupo in B-spec, wanna have a good max speed so it doesn't take forever.

Depends on the car.
I've no idea what the power or weight of the Lupo is.

Give me those figures and I can probably give you a decent estimate if nobody beats me to it with tested specs.

Rule of thumb for an "average" car:

Power (hp) required for given speed (mph) = (speed * speed * 0.02) * speed /375; Then divide all that by 0.85.

So to do 140mph, an average car needs (140 * 140 * 0.02) * 140/375 = 146hp; 146 / 0.85 = 172hp


Take a guess, plumb the speed in and see what the power requirements are. Smaller and slippier cars will need less power to go faster, bigger and more slab-fronted cars will need more.

 

[Rotary Junkie]

Erm Famine... Shouldn't it be divide by 0.85?

146 x 0.85 is 124.1hp not 172.

 

[oppositelock]

The only correct answer is "trial and error". Take the car to SSR7 or La Sarthe and tweak the final until the car stops accelerating just before hitting redline in top gear. For absolute maximum speed, set it so the car stops accelerating at the RPM which coincides with peak horsepower.

 

[XDesperado67]

Easiest way is to set the top speed at a value that's higher than what you think the car can achieve. Say for example with the Lupo 168 mph. Then take it to the track you will be using it on and run a lap or two making note of the highest speed you actually attain on that track. Then adjust the top speed down to about 5 mph faster than that observed speed. Example if you saw the lupo reach 136 mph then adjust the transmissions top speed to 142 mph or so. Run another lap or two to ensure you don't hit the rev limiter or gearing limits and you should be good. Won't necessarily give you the absolute fastest acceleration but without a lot of work will give you good acceleration for that track.

 

[Famine]

The only correct answer is "trial and error". Take the car to SSR7 or La Sarthe and tweak the final until the car stops accelerating just before hitting redline in top gear. For absolute maximum speed, set it so the car stops accelerating at the RPM which coincides with peak horsepower.

Easiest way is to set the top speed at a value that's higher than what you think the car can achieve. Say for example with the Lupo 168 mph. Then take it to the track you will be using it on and run a lap or two making note of the highest speed you actually attain on that track. Then adjust the top speed down to about 5 mph faster than that observed speed. Example if you saw the lupo reach 136 mph then adjust the transmissions top speed to 142 mph or so. Run another lap or two to ensure you don't hit the rev limiter or gearing limits and you should be good. Won't necessarily give you the absolute fastest acceleration but without a lot of work will give you good acceleration for that track.

If you take a guess and plumb the top speed in as above, you don't need to spend as much time - or mileage - testing it out on track, just 2 minutes with a calculator (use the one in Windows - it's probably closer to hand)

As another rule of thumb, if you plumb the numbers in and get a power reading higher than what you've got, take the cube root of the difference to work out how much you need to reduce the speed. If you get a power reading lower than what you've got, take the cube root of the difference to work out how much you need to increase the speed.

Using the example above, I've come up with 172hp to do 140mph. My car only has 156hp so it won't be able to go that fast. 172hp/156hp is 1.10, the cube root of that is 1.033 and 140mph/1.033 is 135.5mph - my car will do 135.5mph. So I set the gearing to 136 for my first test.

My other car has 189hp, so it'll go faster than 140mph. 189hp/172hp is 1.10, the cube root of that is 1.032 and 140mph*1.032 is 144.4mph. So I set the gearing to 145mph for my first test.

Again though, remember that smaller and slippier cars need less power to do the same speed and bigger and slabbier cars need more power, so the above calculations are just rule-of-thumb for average cars - but they'll save you a crapload of track testing time.

Erm Famine... Shouldn't it be divide by 0.85?

146 x 0.85 is 124.1hp not 172.

Yes - I was trying to work it out backwards and forgot that bit wasn't.