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Not quite this week, but I thought you might be interested.

 
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magicb5



Joined: 25 Jan 2015
Posts: 6
Location: Denmark

PostPosted: Sun Oct 09, 2016 8:47 pm    Post subject: Not quite this week, but I thought you might be interested. Reply with quote

I had the opportunity to test drive the Tesla Model S, so I took the B5 (E60) out to have a direct comparison.
There were 2 models 85D and P85D with insane mode.
First I listened to their explanation, which included the 700kg battery pack (!), then I went for a drive in the 85D. I commented that the acceleration seems to drop off rapidly above 80-100km/h, so they took me out in the P85D, and switched it to insane mode. This time the initial start is unbelievable – you could get whiplash – then after the initial push I had the same feeling that the acceleration was dropping off quickly, and was accelerating less than my B5.

So, I wanted to understand
- Is it just a feeling (ie the reduced acceleration was relative to the very high initial acceleration)
- Is it due to no shifts (with automatic or manual gears the body has a change in acceleration that “resets” your feeling of acceleration), or
- Is it for real.

The first article that helped me understand it was a Consumer Reports comparison of the Hellcat and a Tesla. This shows the Hellcat has faster acceleration at higher speed, even if the starting acceleration is lower.
http://www.consumerreports.org/cro/news/2015/07/tesla-model-s-p85d-vs-dodge-challenger-hellcat-video/index.htm

I then cross checked this against a few drag times results (accel graphs) which also showed around 1g for the first second – impressive stuff.
http://www.dragtimes.com/blog/tesla-model-s-p85d-insane-vs-sport
So, why might a 650 HP car feel slower than a 500 HP car ?

First looking at the weight and the power to weight ratio, the figures I could find are


So the B5 only loses 3% by this measure

Next acceleration times I could find
Alpina B5 Tesla S P85D
0-100 4.7 3.6
0-160 9.5 8.6
0-200 14.5 14.6
100-160 4.8 5.0
100-200 9.8 11.0
So the B5 does actually measure faster than the Tesla above 100km/h, but this must mean the Tesla does not continue to develop 100% of its power at higher speeds, or cannot deliver the full power for this length of time
For the record, here are some graphs I prepared to help understand the situation (based on the quoted power outputs and gearing and no losses).




However after some thought – why do I need a car that is faster in 100-200 acceleration, ie how often do I use it (since Germany is 1.5 hours away it can be used).
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E60 B5 in Alpina Blue
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