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標題: Elise Aerodynamic [打印本頁]

作者: Babybenz 時間: 2011-1-9 23:14 標題: Elise Aerodynamic

本帖最後由 Babybenz 於 2011-1-10 11:13 編輯

I've just made a spreadsheet to calculate downforces/drag force at different speed for Elise S1 & S2 based on the factory Lift and drag Coefficients. If you know the coefficients for your car you can calculate for fun as well.

Based on the calculation, my elise with std aerodynamic will have Clf=-0.3 & Clr=+0.53 so the weight distribution will gradually move forward from 41%(front) 59%(Rear) at 0km/hr to 55%(front) 45%(Rear) at 180km/hr. So it is not good since it will tend to oversteer at very high speed cornering.

If I can convert the Clr to -0.3 approx, the whole car can maintain a balanced aerodynamic by installing a large rear wing only. But I expect this will dramatically increase the drag. With the low power my elise has, I have to rule out this option since it will further reduce the already low combat ability of my elise at high speed.

If I buy a S160 spoiler which will bring the Clr to +0.35 region. This will bring the weight distribution to around 52%(Front) 48%(rear) at 180km/hr. I don't have to drag coefficient for this wing but should be lot less than the large wing.

Any comment is welcome before I purchase the wing.

作者: 古惑強 時間: 2011-1-10 13:59

本帖最後由古惑強於 2011-1-10 14:00 編輯

I thought you have already installed the rear diffuser in your S1, surely the diffuser is supposed to clean up the air flow at the rear and reduce lift without compromising drag. I can't open your xls file from my phone, so not sure if you have taken in this factor.

作者: Babybenz 時間: 2011-1-10 14:27

本帖最後由 Babybenz 於 2011-1-10 14:33 編輯

I thought you have already installed the rear diffuser in your S1, surely the diffuser is supposed t ...
古惑強發表於 2011-1-10 13:59

I did not take this into account since I don't have the revised lift coefficient after the installation of diffuser. But the difference in lift between front and rear is quite large (Clf=-0.3 & Clr=+0.53 in standard Elise S1 form). So I am in doubt that the diffuser can compensate such a large difference. BTW the original S1 has diffuser as well but just smaller than the one I installed.

At 180km/h, the front downforce = 75kg and the rear uplift = 132kg. So the difference is 207kg.

作者: romeochris 時間: 2011-1-10 19:46

Babybenz, from your exel file, it shows that all versions of S1 had a lift issue when doing high speed, the car is not being pushedr downward to the track whereas all S2 are being pushed downward when doing 180km/h, is that mean all S1 had some kind of design failure?

作者: Babybenz 時間: 2011-1-10 20:22

The designer mentioned that the main problem came from the high roof line yields a relatively unclean air flow to the back of car.With the spoiler for both 111s and S160 sitting low at the back, it could not resolve the unclean airflow. So positive rear lift force is the case although S160 spoiler provides a better result +0.35 instead of +0.5 for 111s and +0.53 for Std S1. So they lowered the roof line at S2 and problem solved.

I believe I need to get a higher adjustable wing to solve the problem.

作者: 古惑強 時間: 2011-1-11 13:05

Have to admit the Sport 160 spoiler looks pretty good on the S1, kind of un-expected really! As I always feel that the original body shape looks the best, but this S160 spoiler seems to integrate with the body line really well! (This is purely a comment on cosmetic rather than functional issue)

With the S160 spoiler (rear lift +0.35) as well as the rear diffuser, the combined rear lift should be < +0.35. Sounds like a better bet than a high rise adjustable rear wing which undoubtedly will have a much higher drag factor.

作者: Babybenz 時間: 2011-1-11 16:52

本帖最後由 Babybenz 於 2011-1-12 16:30 編輯

By using the rear lift = +0.3 (say), the final weight balance at 180km/h to be 51%(Front) 49% (rear) with respect to 41% (Front) 59% (Rear) at 0 m/hr.

Here is the dilemma. If I go for the S160 spoiler, the handling characteristic will be changed from MR to almost perfect balance 51:49 with total weight remain unchange. If the handling characteristic changes with speed, it may be difficult to handle/adapt.

If I go for the highrise wing (say lift = 0 & Cd = 0.5), the final weight balance at 180km/h to be 46%(Front) 54% (rear), still a MR with total weight increase by 75kg and additional drag of 8kg only comparing with S160.

Please advise which wing you like most.

作者: Babybenz 時間: 2011-1-13 13:33

Please let me know your choice of wing (just for a reference)?
                  Vote
Wing 1/2          0
Wing 3             0
Wing 4             0
Wing 5             0

作者: 古惑強 時間: 2011-1-13 14:08

Sorry, I still like the s160 spoiler only!

作者: Simon 時間: 2011-1-13 14:22

1/2 NO
4, 5 ok

作者: Babybenz 時間: 2011-1-13 14:30

回復 9# 古惑強

for cosmetic only, I prefer no spoiler the best followed by 111S/S160 spoiler. But I need to consider functional factor as well if I need to spend $.

作者: paul 時間: 2011-1-13 14:50

wing 5

作者: jockey 時間: 2011-1-13 14:58

wing 4

作者: AbarthJoe 時間: 2011-1-13 16:23

Wing 4

作者: Babybenz 時間: 2011-1-13 17:03

回復 10# Simon

How about 3?

作者: Eric 時間: 2011-1-13 17:05

If you want wing #5, I give sell mine from FD3S for low low price.

作者: Babybenz 時間: 2011-1-13 17:12

回復 16# Eric

Can I have a look and put on the car to see it looks good or not?

What colour is the wing?

作者: 古惑強 時間: 2011-1-13 17:13

Voting so far
1. 0
2. 0
3. 0
4. 2.5
5. 1.5

作者: Babybenz 時間: 2011-1-13 17:20

回復 18# 古惑強

Thx Rikki

作者: Eric 時間: 2011-1-13 21:57

Here is the picture:

作者: Eric 時間: 2011-1-13 21:58

The wing is in black color.

作者: romeochris 時間: 2011-1-13 23:19

4,5 are okay, but have you got more pic on #5?

作者: Trevor 時間: 2011-1-14 00:52

#3,4

作者: Babybenz 時間: 2011-1-14 07:55

Voting so far
1. 0
2. 0
3. 0.5
4. 3.5
5. 2

作者: Babybenz 時間: 2011-1-14 07:58

回復 22# romeochris

More Wing 5 photos.

作者: romeochris 時間: 2011-1-14 08:43

I think #5 looks good on these pictures, but has #5 got a good function on the downforce?

作者: Babybenz 時間: 2011-1-14 10:15

回復 26# romeochris

The higher the wing, the better of downforce with not much penalty on drag.

http://www.lotustalk.com/forums/ ... x3.html#post1062795

作者: romeochris 時間: 2011-1-14 14:52

no wonder why that RX-7 wing is that high! haha