0-100 Km/h Times Are Useless, So Stop Asking For Them

[PSI_GTSII]

Heres something I knocked up which may simplify it...?

(btw, it is not mathmatically accurate, and is just to highlight the issue)

CAR A: Fast starting car with tapering off top end

0-10kmh = 1 second = 2 metres

10-20 kmh =1 second = 4 metres

30-40kmh =1 second = 8 metres

50-60kmh = 1 second= 12 metres

70-80kmh =2 seconds= 40 metres

90-100kmh = 4 seconds= 160 metres

Total 0-100 time is 10 seconds and covers 226metres

CAR B: Slow starting car with strong finish

0-10kmh = 3 seconds = 6 metres

10-20 kmh = 2 seconds = 8 metres

30-40kmh = 2 seconds = 16 metres

50-60kmh = 1 seconds = 12 metres

70-80kmh = 1 seconds = 20 metres

90-100kmh = 1 seconds = 40 metres

Total 0-100kmh time is 10 seconds and covers 102metres

Edited June 15, 2006 by PSI_GTSII

[Big Rizza]

PSI GTSII kind of beat me to it, but I have my own example:

I’ve always been really good at grasping this sort of thing (it’s the engineer in me), but terrible at explaining it! If I break it down into sections, including time, speed, acceleration and distance all together, maybe people will understand better.

Taking the V8 vs turbo route:

0-1 second

The V8 accelerates harder than the turbo over this increment because of its strong torque. The V8 gains 20km/h compared to the turbo’s 10km/h. The V8 is accelerating harder than the turbo (speed rising at 20km/h per second vs 10km/h per second). The speed of the V8 at this point is now 20km/h, the speed of the turbo at this point is 10km/h, so the V8 is pulling away from the turbo.

At 20km/h for one second, the V8 will travel 5.5 meters. At 10km/h for one second, the turbo will travel 2.8 meters. So the V8 will be 2.7 meters ahead of the skyline after 1 second.

1-2 seconds

The V8 keeps accelerating as before, gaining another 20km/h over this second. The laggy turbo starts seeing positive boost pressure and accelerates 15km/h over this second.

The total speed of the V8 is therefore 40km/h (20km/h + 20km/h), and the total speed of the turbo is now 25km/h (10km/h + 15km/h). The V8 has a higher speed than the turbo, and is therefore pulling away from the turbo, increasing its lead.

At 40km/h for one second, the V8 will travel 11.1 meters. At 25km/h for one second, the turbo will travel 6.9 meters. The total distance travelled by the V8 will be 16.6 meters (5.5 + 11.1). The total distance travelled by the turbo will be 9.7 meters (2.8m + 6.9m). So the V8 is ahead by 6.9 meters after 2 seconds.

2-3 seconds

The turbo continues to spool up and acceleration improves again, gaining 20km/h this second. The V8 also gains 20km/h. At this point the ACCELERATION of both vehicles is the same – both are gaining speed at the same rate (20km/h gain per second).

But the SPEED of the V8 is higher at 60km/h (20km/h + 20km/h + 20km/h) vs 45km/h for the turbo (10km/h + 15km/h +20km/h). So even though the acceleration is identical, the higher speed of the V8 means that it continues to extend its lead over the turbo (it should be obvious that the car travelling faster will be pulling away, ya?).

At 60km/h for 1 second, the V8 will travel 16.6 meters. The total distance travelled by the V8 is now 33.3 meters (16.6m + 16.6m). At 45km/h for 1 second, the turbo will travel 12.5 meters. The total distance travelled by the turbo is now 22.2 meters (12.5m + 9.7m). So the V8 is now ahead by 11.1 meters.

3-4 seconds

The turbo is really starting to cook now, accelerating 25km/h this increment, vs the V8s 20km/h. So at this point, the ACCELERATION of the turbo is better than the V8. It is gaining speed more quickly than the turbo (25km/h per second vs. 20km/h per second).

The total SPEED of the V8 is now 80km/h (20km/h + 20km/h + 20km/h + 20km/h) and the turbo is now doing 70 km/h (10km/h + 15km/h + 20km/h + 25km/h). The V8 has a higher speed than the turbo, so it continues to extend its lead over the turbo.

EVEN THOUGH THE TURBO IS ACCELERATING HARDER (25km/h/sec vs 20km/h/sec), THE SPEED OF THE V8 IS HIGHER (80km/h vs 70km/h) AND THEREFORE THE V8 IS STILL EXTENDING ITS LEAD!!!

At 80km/h for one second, the V8 will gain 22.2 meters. The total distance travelled by the V8 is now 55.5 meters (22.2m + 33.3m). At 70km/h, the turbo will travel 20m in one second. The total distance travelled by the turbo is now 42.2 meters (20m + 22.2m). So the V8 is now ahead by 13.3 meters.

4-5 seconds

The turbo is now on full boost, gaining a full 30km/h over this second, vs the V8s 20km/h. The ACCELERATION of the turbo is now significantly greater than that of the V8.

The total SPEED of the V8 is now 100km/h (20km/h + 20km/h + 20km/h + 20km/h + 20km/h), and the total speed of the skyline is now also 100km/h (10km/h + 15km/h + 20km/h + 25km/h + 30km/h). The speed is identical, so no car is gaining or losing ground against the other.

Both cars will cover 27.7 meters in one second at 100km/h. So the total distance travelled by the V8 is 83.2 meters. The total distance travelled by the turbo is 69.9 meters. The V8 is ahead by 13.3 meters.

There we go! Two cars with an identical 0-100km/h time, but in a race to 100km/h, the V8 wins by nearly 3 car lengths!

Edited June 15, 2006 by Big Rizza

[Cubes]

It makes perfect sense..

Awesome thread, I can say I have never 'really thought' about acceleration with regards to distance traveleed over time vs km/h for a given time.

This would also explain why you need so much more power to play catchup. One car clearly has so much more power yet it appears as if they are not really gaining on them at the expected rate (sucking doors off speed)

[VB-]

this reminds me alot of something i read about average power, where u take dyno figures from several different rpm point, and dividing by the number of rpm points used... you can have your big turbos and be out accelerated by a stock car, providing theres no rev limiter launchs

[ferni]

The whole point of this thread is to say 0-100 times dont say how fast a car is, while that is technically correct, it still gives you some ideas.... to find out which car is quicker you would race them right? over a set distance.... say 1/4 mile?

So the 1/4 mile drag is a better test to find out which car is faster....... over a quater mile

[Cubes]

So especially no more 4wd vs rwd 0-100 comparisons.

[dangerous_daveo]

The whole point of this thread is to say 0-100 times dont say how fast a car is, while that is technically correct, it still gives you some ideas.... to find out which car is quicker you would race them right? over a set distance.... say 1/4 mile?

So the 1/4 mile drag is a better test to find out which car is faster....... over a quater mile

Im still with the whole track thing though. Because really you need corners, and if your car cant go around them, pfft to your car! We (well most) drive skylines or skyline dirived cars, with good power, and good handleing. Corners is where its at!

G- FORCES!

LoL (here we go...)

[Big Rizza]

Im still with the whole track thing though. Because really you need corners, and if your car cant go around them, pfft to your car! We (well most) drive skylines or skyline dirived cars, with good power, and good handleing. Corners is where its at!

G- FORCES!

LoL (here we go...)

The whole circuit vs. street vs. strip debate is somewhat outside the scope of this discussion

[Cubes]

Street

Drifto

Circuit

Drag

Lots of different ways one can set their car up.

[khunjeng]

lol i just read all of this and its one of the most intresting treads I have seen for a while...this was an assignment when i did specalist maths in 1995...heheh.

KJ

[PSI_GTSII]

As far as I'm concerned 0-100kmh times used as a guide to a cars performance sucks....

The UK especially seem obsessed with it...I guess it gives there 'Hot' hatchbacks a chance of appearing quick....?

Its to short a time period for me to show a cars true performance.

Even just printing a 400m time is not really an accurate guide.

In a perfect world I'd like Magazines to test each cars standing KM performance with it broken down into speed and distance increments such as 60ft, 660ft, 400m and 1000m etc so you can really see where cars are strong and weak in performance

[PTR33]

Hey all,

There seems to be a lot of people who seem to be using the 0-100km/h time as a bench mark for vehicle performance. However, in my experience the 0-100km/h time is not a great reflection. Why is that? Many of the real world traffic light grand prix events are from rest (0km/h) to the speed limit, or just over it (so about 100km/h), so surely this would be the definitive measure of a cars on street performance? Not really, no. I will use an example to illustrate my point.

Three cars line up at the traffic lights. All three cars have an identical 0-100km/h time. For simplicity, let's make it 10 seconds. The speed limit of this road is 100km/h, so it will be a race to the limit. Nothing illegal here

Car number one is a concept vehicle (why it's at the lights I don't know...). An electric vehicle. It doesn't make much power (in fact the top speed is only 100km/h), but it is ultra light, and has 4 in-wheel electric motors giving full torque from 0 rpm, meaning it can charge of the line hard. Car number two is a regular family car. The long geared automatic with big six cylinder power means that acceleration is fairly constant throughout the rev range. The final car has a big turbo, front wheel drive, and manual gearbox. This makes it tricky to get off the line, but once it's hooked up and the turbo spooled, the acceleration is very good.

The image below shows a representation of these three cars' acceleration curves. As you can see, all three will hit 100km/h at the exact same moment.

(for those who care, the electric car's speed was modelled by a quadratic equation speed=-(time-10)^2+100, the family car by a linear equation speed=10xtime, and the turbo by another quadratic equation speed=time^2)

So it's a race to 100km/h, and all three cars have an identical 0-100km/h time, so it should be a pretty close race, right?

WRONG!

The hard launching electric car gets the jump from the start, and wins by a full 45m over the family car, and a whopping 90m over the turbo car - that's about 18 car lengths!!!!

(For those who care, distances were obtained by integrating the speed equations stated earlier. If I made any errors then they were deliberate and hence I don't care - don't bother pointing them out, the electric car would still win )

This is obviously an extreme case, but I think it illustrates my point nicely. 0-100km/h times are stupid.

Dude, you need a girlfriend more than anyone else in the history of the world......

[Dash]

Of course there useful,just like any other performance measurement.

If a car does 0-100 in 6s you have a 14 sec car

If a car does 0-100 in 5s you have a 13 sec car

If a car does 0-100 in 4s you have a 12 sec car

While this is a generalisation you get the idea,where it does get blurry is when you start to add a modified car.

Big turbos(or incorrectly sized ones),gearing,tyres, high stall convertors, nitrous can all alter the 0-400m time dramatically and the 0-100kph.

Because almost all "new" car manufactures use these figures its easy to compare vehicles.

As for 2wd guys who think 4wd is cheating.

Well all you have to do is next time you line someone up at the lights(at the drags) just wind down your window and ask if they could please take off slowly and then race when you catch up as your undertyred/overpowered car is only fast after 80kph,I'm sure they'll oblige

[dangerous_daveo]

I did forget to mention that, very good topic.

I think all the information is important. The more of it just allows you to make a better comparision.

Say you have your 0-100, 0-150, 0-200. Then a standing 1/4 mile (for when you dont have a calculator at the motorshow). A skidpan cornering G rating. A braking distance from say 60, 100, 150kmh. And thats getting off topic a bit.

[siksII]

ive always thought about this in my head, and wasnt sure if made sense. now thats its been spelt out i know it always made sense, thanks for typing it out!

[Shayde]

Interesting thread. One of the only threads I've read with no flaming! Hah

[boodsGtr]

Hey..has anyone seen my parabolic curve??

Ive misplaced my parabolic curve.

[runs away holding a scientific calculator]

[Cubes]

Well all you have to do is next time you line someone up at the lights(at the drags) just wind down your window and ask if they could please take off slowly and then race when you catch up as your undertyred/overpowered car is only fast after 80kph,I'm sure they'll oblige

Or............ don't stall it and sit quietly as not to make them think you are going to give it stick then let that 3ltr off idle torque rip through first.

[KamikazeR33]

meh all formulas should ask "can it chirp 2nd?"

[scathing]

In a perfect world I'd like Magazines to test each cars standing KM performance with it broken down into speed and distance increments such as 60ft, 660ft, 400m and 1000m etc so you can really see where cars are strong and weak in performance

I'm with you on that. They should break down the times into specific distances so people can see where some cars get the jump and others can muscle back.

I think 0-100km/hr times were great back when cars were relatively slow (I mean back in the 60's when the car culture really came alive and your average family hack struggled to even hit 100km/hr) and all of them were FR machines. It was a good way to show which had more power or better suspension since most other things were equal.

But unfortunately as time and performance have moved on, the benchmarks have not. A quarter mile is a bloody long distance for a FJ Holden to cover. But its doesn't take that long even in a V6 Commodore these days. And you're splitting hairs when it comes to 0-100km/hr times, when you're talking decimal places.

If you want to account for "inflation" to something equal to the benchmarks we used in the 60's, it should be 0-160km/hr and standing kilometre times.

When you're talking 0-160km/hr times you take a lot of the initial traction out of the equation, and short geared cars will bang off their limiters and lose out in the standing kilometre when the more powerful / aerodynamic cars can continue to pull.

Given that I'm at the top of 4th when I finish the quarter, I think I'd come real close to hitting my 250km/hr speed limiter by the end of a kilometre. I wouldn't reach it, but I'd come close. In the same way, I reckon an FJ would have probably run out of torque in top gear at the end of the quarter back in its day.