Sunday, 22 September 2013

Statistics, Statistics, Statistics: FSG Acceleration through the years

The Acceleration event is probably the dynamic event which is most comparable over the years at FSG. It has been conducted on the exact same part of the Hockenheimring since 2007 and we also did not change the surroundings like we did for WetPad for example. Thus I figured that it is worth to take a closer look at the results of the Acceleration event from 2007 to now. Just to see, if there are any surprising conclusions from doing that.

A word about this kind of posts (statistics involved): All shown data has of course been pre-processed in some way by me and/or others. I do my best to always tell you, what I have done with the data, but nobody is perfect. So always take the provided data with a grain of salt. And there is one more thing about statistics, which is well covered by my favourite statistics (and probably nerdiest ever) joke:

Two engineering students meet. One of them says:"I have just attended a statistics lecture about correlation and causality.". The second student asks:"So do you now have a better understanding of this topic?". The first student replies: "I don't know."

I know, nothing that makes you burst out in laughter and it will probably also not make you the centre of a small talk party conversation, but it makes a good point: Just because two things happen at the same time, they must not be related. Please always keep that in mind when interpreting the data provided in my statistics posts.

So back to topic:
The first thing to look at are the weather conditions. I have extracted them from the archive of Wetter.com (Mannheim weather station) and by checking out the pictures provided at media.formulastudent.de . This is the retrieved data:


Weather Conditions FSG Acceleration 2007 - 2013
Year 2007 2008 2009 2010 2011 2012 2013
Tmin[°C] 18 17 21 15 21 17 25
Tmax[°C] 21 21 23 23 26 26 30
Taverage[°C] 19.519 22 19 23.5 21.5 27.5
Precipitation [mm/m²] 0 0 0 0 0 0 0
Cloud Coverage Medium Medium Dense None Low None Medium

Thankfully the weather conditions were relatively stable over the years. There has never been mentionable precipitation, but the ambient temperatures vary from a low average temperature of ~19°C in 2008 to ~27.5°C in 2013. However, under the assumption that the fastest times were driven under the best track conditions, which usually means highest temperatures, the maximum temperature should be the better indicator.
The cloud coverage does also vary and is important to judge the influence of direct sunlight on tarmac temperature. It is a conservative approach to say that even for years with dense cloud coverage, the tarmac will reach at least ambient temperature. For years with low or none cloud coverage the difference between ambient and tarmac temperature increases compared to a day with dense cloud coverage. But we already drift into scientific guessing...so let's move on.

Another impact factor could be whether F1 has been at the Hockenheimring the week prior FSG. It can be assumend that F1 itself and the numerous races of other classes held at the same weekend have also an influence on the grip level. F1 visited Hockenheim in 2008, 2010 and 2012.

Now we know the general conditions, so here come the times and weights for the combustion cars. I have taken the average of both, times and weights of the Top3 cars and the winner's value of both. Click the diagram to get the full size version in a new browser tab.

FSG Combustion Acceleration Times and Weights 2007 - 2013
Some things can be seen in this diagram:
  1. Weight seems not to be of major influence as until 2012 the winner's weight was, sometimes significantly, above the Top3 average weight. It still needs to be within a reasonable window though. Even, if this is not shown here: All winning teams have had 4 cylinder cars and most of the Top3, but not all, were 4 cylinder cars. Which also explains the rather high weight of the Top3 teams.
  2. Ambient temperatures (I am not talking about track temperatures!) seem to be of minor influence, when looking at the 2013 times compared to the other years.
  3. It is hard to judge whether F1 has an influence or not, as the low average time in 2011 speaks against a pattern in low and higher times oscillating with F1 appearance at HHR (2008, 2010, 2012).

Sadly the data does not provide any crystal clear conclusions, except that, quite surprisingly, more engine power helps being faster at Acceleration...the other 95% confidence conclusion is that weight is not a major concern when it comes to the Acceleration event, provided that you have sufficient power aka a good power-to-weight-ratio. Also not that surprising.

For the FSE cars, this looks different:

FSG Electric Acceleration Times and Weights 2010 - 2013
  1. The acceleration times have significantly improved over time.
  2. Being low weight has gained importance in FSE. At the beginning in 2010 the winning car of the acceleration was heavier than average within the Top3. But in the years after, the winner was at maximum as heavy as average or below.
  3. The gap between average times of the Top3 and the winning time got narrower, except for 2012, when Delft's first AWD car did the fastest time to date in Acceleration at FSG.
  4. Ambient temperatures and F1 attendance does also not seem to be a major influence. This is even harder to tell for FSE as the teams kept improving every year, which probably masks other factors.
Again, no real surprises. The data shows that being low weight and still have sufficient motor power available is easier for electric cars. What we can also see is that the average weight increased, after the change of the Efficiency scoring. This was an anticipated change, because of the higher accumulator capacity which makes sense with the new scoring formula in place.

For FSE, we have another dependable data source to look at and this is the Energy Meter data:
FSG Electric Acceleration Times and Power 2011 - 2013
  1. It is obviously not necessary to get very close to the rules limit to finish within the Top3. The Top3 maintained a safety margin of ~5kW and still managed to be fast enough.
  2. Although the power limit dropped from 100kW to 85kW in 2012, the times dropped as well. But the car weights dropped as well, so there is no specific conclusion from that.
  3. From 2012 to 2013 the times went slightly higher. Looking at the weight figures, this could have been caused by keeping the power at the same level while increasing the average car weight by about 20kg.
If there is something important to be learned from this data, then that you do not have to get very close to the allowed maximum power to get into the Top3. The Top3 managed to get there while staying about 5kW off the limit. Since a team will lose all points in a dynamic discipline, if it goes over the limit, it is probably a good advice to stay 5kW off the limit. It seems not to hurt so much after all.

Something that can not be seen in this diagram is that the Top3 in 2013 were all AWD. So in the end, it is more about grip than top end motor/engine power.

Please note:
If you think that any content in this post is worth discussing, please do so in the FSAE.com forum and not in the comment section of this blog, to make sure that everyone can benefit from the contents of the discussion, even if he/she is not reading this blog.

No comments:

Post a Comment