Have you ever heard of SWEDAC? What about the PML within NIST? Maybe you’ve heard of NMRO, then? OK, you probably haven’t, but those offices in Sweden, the USA and the UK do something that’s quite important: they regulate instruments that are used to weigh and measure things.
They are there to ensure that the fuel pump actually gives you the litre or gallon of petrol that you’re paying for, that the kilo of steak you pick up from the supermarket actually weighs a kilo. They don’t actually measure individual items. They set the standards that measurement machines are built to. The theory is that if the standard is correct, machines built according to that standard can be trusted to accurately measure the things that we use and buy. This ensures that there’s consistency and integrity in the market.
You probably don’t think about it that much, but weights and measures are very important. So important, in fact, that governments around the world have agencies like those mentioned above keeping an eye on things to protect consumers.
Pivot to cars…….
There are two primary units of weight measurement that carmakers typically use when they are talking about a vehicle’s mass – dry weight and curb weight.
In simple terms, dry weight is the weight of the vehicle on its own with no fluids. Curb weight is the weight of the vehicle “ready to drive” – with all oils, coolants, fuel and other liquids. If you want to dig deeper, there are weights that we, as manufacturers, are legally obliged to declare as part of the Type approval process. For the EU, we use ‘Mass In Running Order’, which is curb weight plus 68kg for the driver. In the US, we have to declare the ‘Gross’ weight, which is curb weight plus 300lbs.
Some manufacturers don’t calculate curb weight with a full tank of fuel, but with a “nominal” fuel level (e.g. 50%). Various requirements define different amounts of fuel to be included.
As you can see, it can be difficult to compare apples to apples.
It’s not unheard of to see ‘dry’ weight being used by manufacturers in their sales literature. It’s great for marketing but it’s not really any good for customers for one very important reason – you can’t drive a car at its dry weight. The lack of fuel won’t allow it to start and even if it did, the lack of lubricants and coolants would seize everything up in a matter of seconds. If, by some miracle, you managed to actually move the car, you wouldn’t have any brake fluid to stop it.
At Koenigsegg, it’s our policy to put the curb weight in our press and publicity materials. There are occasional variations within that definition, but we specify any variations so that you’ll know exactly what we’re talking about.
For example, when we did the One:1 program, we initially thought it would be very difficult to reach the One:1 power-to-weight ratio if the car was weighed with a full tank of fuel. So, in order to make sure we hit the One:1 ratio with our factory development car, we used a nominal fuel load of 50%. Using a nominal fuel load is a common way to measure curb weight and the nominal level can be anywhere from 50% to 75%. With the One:1, our fears were unfounded in the end, as we managed to get our customer vehicles under 1360 kg with a full tank of fuel. Our press material still talks about the 50% fuel load because that’s the way it was done at the time, but One:1 owners know they have a car that is well and truly 1:1 in terms of power-to-weight.
And as an aside, if one of our production One:1’s is driven with very little fuel and with a light driver, it can still have a One:1 ratio even with the driver included! But we digress…..
In the Agera’s case, the curb weight of the car is around 90kg more than the dry weight. The difference is about 120kg for the Regera. That’s a significant difference in the hypercar/megacar sector where weight is such a crucial figure. You can see why some might be tempted to quote the dry weight. Ask any hypercar company if they’d like to save 120kg or more with the stroke of a pen and they’d give you a resounding ‘yes’.
So as you delve into all the information that comes your way, take a look at the weight measurements that manufacturers use. Do they use curb weight, dry weight, or do they muddy the waters and just use ‘weight’ without specifying which?
Ratios
There’s something else we’d encourage you to check out, too – power ratios.
The most obvious one is the power-to-weight ratio, which tells you how many horsepower per kilogram. This is the ratio that the One:1 was named for as it has 1 horsepower for every kilogram of mass (measured as curb weight, with all fluids). The Agera RS has a power-to-weight ratio of 0.84:1. Do the sums on our competitors and we think you’ll find those numbers quite compelling.
There’s another ratio we like to use when comparing our cars – power-to-weight-to-weight (PWW).
Weight and power are interesting measurements on their own but measuring their combined value against the weight of the car is a great way to understand a sports car’s propensity to perform well around a race track.
For example: A sports car with 3000kg curb weight and 3000hp will have a power-to-weight ratio of 1:1. A car with 500kg curb weight and 500hp will also have a power-to-weight ratio of 1:1. Which one is likely to be faster?
Given an endless straight, the 3000kg car would be faster, as long as the aerodynamics are similar to the 500kg car. The 3000kg car has more power and its weight is not such a huge penalty for top speed (as long as the tires can take it). This means little around a race track, however, as straights are always limited in length. If fact, the 3000kg car will be almost undriveable around a track. It’ll have terrible brakes because there’s so much mass to stop, it will pull minimal G´s in the corners and acceleration in a straight line will be impacted by the shorter straights.
In contrast, the 500kg car will have blistering corner performance, great acceleration and incredibly short braking distances.
How do you calculate a simple PWW?
Find out the power figure and the true curb weight of the car in kg. Then take the weight and divide it into the car’s horsepower figure (P/W). Then divide the result again with the curb weight of the car. In order for the number to be easily readable, multiply the result by 10,000.
The higher the number, the better the result. Here are a few examples:
Formula – (P/W)/W*10000
Koenigsegg One:1 – (1360/1360)/1360*10000 = 7.353
Koenigsegg Agera RS (MY15 EU spec) – (1160/1382)/1382*10000 = 6.074
Again, if you do your own sums using competitor vehicles, you’ll find that our numbers are quite favorable.
Of course, there’s more to how a vehicle performs than this simple calculation. Chassis setup, suspension, steering, brakes – all of these play an important part in a car’s performance. But it’s good for providing a thumbnail view to compare from car to car.
Our advice – weigh the hype. Assess whether you’re getting all the information you need and make an informed judgement about what you’re reading.
21 responses to “Apples, Oranges, Weights and Measures”
Very interesting article. I never heard of power to weight to weight before.It’ll be fun to calculate this for all of the new supercars at Geneva, but I think I know who will come out on top 🙂
Quite an interesting topic! I’m still learning the basics of certain car terminology and I’m glad to know what dry weight and curb weight are! I’m sure those are very useful terms.
I enjoyed learning about how you guys used these weight factors to determine the best way to build your cars with the best performance. And I’m sure comparing the numbers with other competitors yields very pleasing results. As with all other areas of manufacturer comparisons, none can possibly match those of Koenigsegg:)
Keep up all the good work and keep us updated on the last Agera model!
Excellent post, but you actually need to put scales under the wheels of a fully tanked Chiron to find the number.
They won’t tell you the truth.
Koenigsegg Agera RS 1MW (1360/1382)/1382*10000 = 7.1
Koenigsegg Regera (1500/1628)/1628*10000 = 5.7
Koenigsegg Regera Track (1500/1360)/1360*10000 = 8.1
It would be interesting to see what the numbers would be for LaFerrari, P1, 918 and maybe some more “normal” cars like GT3, 458 and so on.
This newsletter thing doesn’t really work. I usually read your posts day or two before I get email from you guys
i thought hey maybe the nw huayra bc can get this number high, it does at 5.7 but still no match to an agera rs. also the huayra is listed to have the same weight curb and dry so someone messed up there
Not messed up, it’s the dry weight.
Another spec I like to consider when comparing cars (even though my price range is much, much lower) is rear wheel torque per curb weight. This number can fairly accurately predict acceleration, which is something every driver gets to use, unlike horsepower which more directly affects top speed, and there are very few places (especially in America) where you can test the top speed of a decent sports car.
(For you physics nerds out there, rear wheel torque divided by the wheel/tire radius is a force, curb weight is a mass, so I use rear wheel torque per curb weight because Force / mass = acceleration).
Once at the racing I was forbidden to participate, as the power factor Honda Civic TypeR the weight was 1,020 (!): 205hp = 4.95 The organizers of the race are not allowed to participate justifying the regulations, which allowed to have a ratio of at least 6. Where justice, tell you) but it is not about etom.Na actually sales marketing dictates unfair conditions. “Lie, but sell”
When an electric Koenigsegg? 😀
Thank you! This is an auto-enthusiast pet peeve of mine and it has certainly flared up during these last few days!
Lets set the record straight, with all fluids and a full tank of gas:
Huayra BC = at least 1308 kg or 2884 lb*
One:1 = 1360 kg or 2998 lb
Agera RS = 1382 kg or 3047 lb
Huayra = 1440 kg or 3175 lb*
McLaren P1 = 1543 kg or 3402 lb
LaFerrari = 1585 kg or 3495 lb
Regera = 1628 kg or 3589 lb
918 = 1705 kg or 3758 lb, around 1640 kg or 3616 lb w. Weissach package
Aventador SV = 1814 kg or 4000 lb
Veyron Super Sport = 1995 kg or 4398 lb
*1308 kg for the Huayra BC and 1440 kg for the Huayra is their claimed dry weight + 90 kg. However they carry a V12 with an engine bay jam-packed with load-bearing metal, not two but four hydraulic pistons for the active aero, and an interior cluttered with thick leather and metal details. There is a very good possibility that some creative measuring occurred (e.g without paint, without stereo system, without air-con, without floor mats, without several components).
Brilliant way to estimate on-track performance!
Caterham 620R works out to 310/572/572*10000= 9.74!
Ariel Atom 350R 350/520/520= 12.94!
Although they don’t specify if it’s dry or curb weight, but even if you add 50kg (having 4cyl engines they need quite a bit less fluids) the numbers are higher than pretty much any supercar.
Here’s another measurement boogeyman – horsepower. At the crank or at the wheels? The latter number is actually more important, but the difference between the two defines the parasitic properties of the drivetrain. Why don’t we measure wheel horsepower instead of crank? Is it because of the variations between dynamometers? And if so, why can we not simply assign a specific one with assigned calibrations to make all tests apples vs apples?
I imagine that’s purely a marketing thing. Yes, whp is more telling about what the car can actually do but when you’ve got two figures you can quote, you’re going to quote the higher one. That started a long time ago and it’s now considered normal.
It’s also, perhaps, the accurate answer to the most common question – how much power does the engine have? Everyone would need to start asking how much power does it have at the wheels for that to become the normal answer.
There are different numbers for that: In many countries like the US or Great Britain it’s common to use bhp (brake horse power), which is measured at the crank, but in Germany (I don’t know exactly where else, too) we use whp (wheel horse power). Unfortunately, both kinds of horsepower can be shortened as hp.
However, the worst thing is that there are official ratios for converting the two kinds of horsepower even though it depends on the transmission of the very car you’re measuring (e.g. a Regera has a very closer ratio than an Agera [or any other car with a transmission]).
That’s why I think everyone should use whp.
Here’s a silly question, thinking from a rally point of view: what about diesel torque or electric torque numbers instead of horsepower? And horsepower, not Newton-Meters or something else vs kilograms ? Seems strange through I understand the idea of keeping the units the same regardless. Pardon my thinking out loud here if I’m being silly.
(Oh and of course, my Canadian-version Golf TDI: 0.72)
I love the way that Running Order weight is 68kg (150 lb) in Europe, whereas in the equivalent American rating (Gross wgt) it is 300lbs, which is about 140kg. Average personal weights of the respective populations is being used, presumably.
TFW your swedemath says a Venom GT gets a score of 9.376.
What’s going on with APEX? They have such a big delay, is it due to Nürburgring speed limits?
Given huge variation of how horsepower and weight are defined in the industry, I think trying to calculate all those ratio from factory official numbers are rather pointless.
In terms of weight, car magazines around the world have consistently find official curb weight numbers are quite different from real curb weight, when the magazine staff put the car on an actual weight scale. So trying to make sure all weight numbers are “apple to apple” (curb weight) won’t help.
In terms of horsepower, it is the WHEEL horsepower that matters using a dyno. Even when you have wheel hp (from dyno) from all manufacturers, there could be variations due to the atmospheric conditions during the dyno tests. So all in all, you have huge variations of every variables when calculating those ratios which are all theoretical anyway.
If you ask me, it is all those standard test that matter, such as 0-100 kph, 0-200 kph, 1/4 miles time and trap speed, skid pad g force etc. Track time is extremely important too. These are all real numbers that show how all systems within the car perform as a whole.
I really hope Koenigsegg will do a Nurburgring time this year when the track management allow high speed test again. It is really THE number that all car fans in the world will remember and has the most marketing value to brand. Forget about all those theoretical numbers or measurement, very few people will know what it really mean in the real world.