Sean's Lotus Exige track journal and videos - Northern California - Page 2 - LotusTalk - The Lotus Cars Community
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post #21 of 25 (permalink) Old 06-27-2018, 03:05 PM
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Originally Posted by Formulabob View Post
(1) I hate the Raybestos ST43 pad compound but YMMV.
Just out of curiosity, what don't you like about the ST43 pads?
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post #22 of 25 (permalink) Old 06-27-2018, 03:57 PM
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Originally Posted by jds62f View Post
It will be useful to me, i'm fitting penske's right now! Did you mean "winmax" instead of wilmax? Also, have you modified brake master mc given the change in front and rear brake calipers?
Yes, Winmax not Wilmax. Ordered a larger MC but received a note with it indicating that the one I ordered had been superseded. New one was not the size I wanted and mounting holes were clocked differently. Found a part number on a VW forum for a “larger” MC to replace our standard one — forum members said it was 1” on both circuits but it was smaller on the rear circuit. So for the time being I will live with the increased pedal travel over stock. However, I eventually will find a reasonable way to decrease pedal travel.

Hate probably is too strong a characterization. The ST43s were squealing terribly on the track — even on my slotted discs and with double the standard break-in. Initially they also felt a bit “soft” although after four sessions they were feeling much better, but still sounding like I was castrating a pig in every braking zone. YMMV

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post #23 of 25 (permalink) Old 08-23-2018, 09:14 AM Thread Starter
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Another SpeedSF Challenge time attack is in the books! The Exige returned to Laguna Seca on 6/17 to test the chassis changes, again competing in the S2 class. The winning time was a 1:39.7, besting a Porsche Cayman GT4 which took second place. Note that the lap shown is a 1:39.8 which could have been even faster if it were not for the need to pass an oversteering M3 just after the corkscrew.

The results from the event emphasize the need for track-specific optimization. The setup was unchanged from Sonoma, where higher speeds and the rougher surface demanded more compliance and stability. The baseline Penske suspension settings, factory aero, and non-LSD were much more suited to Laguna Seca's traditional corners and longer straights than they were at Sonoma. The Exige rotated easily through the low-speed hairpins and only exhibited moderate oversteer in faster corners such as T5 and T9.

The quick-wearing character of the RE-71R's was again apparent with the rear tires already worn past their prime by the end of this second day. The front brake pads wore down quickly to the backing plates, ending the day one session early and highlighting that the front brake bias of the factory setup can be easily overwhelmed by heavy braking into T2 with greater than stock power. Finally, the newly-fabricated Laguna pipe worked as expected allowing the Exige to fly by the T5 sound station without penalty all day.

The SpeedSF Challenge S2 record still eludes us, set by a GT4 in 2017 with a time of 1:38.0. We plan to increase the grip at the Exige's rear axle and adjust its brake bias to better handle high speed stops. Hopefully, the Lotus can get closer to the Porsche's record with these changes.

Last edited by smurfm3; 08-23-2018 at 09:29 AM.
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post #24 of 25 (permalink) Old 08-23-2018, 09:55 AM
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Nice lap, Sean.....but it still looks like you are having to work too hard. More setup experimentation may be needed.

An oldie but goodie video of mine -- my personal best lap time of 1:35.46 at Laguna running a stock engine tuned for headers during a Lotus Cup USA weekend ......

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post #25 of 25 (permalink) Old 09-03-2018, 04:01 PM Thread Starter
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The Exige returned to Laguna Seca this past Monday, 8/27, to test a new aero setup! Trackspec removed the stock splitter, wing, and diffuser and replaced them with the Reverie 1650mm wing, Reverie front splitter, and Difflow Flat Track diffuser.

This was a true back-to-back test with no other setup changes. The change in handling was extremely significant! Before, the aggressive alignment settings with close to neutral rear toe worked well at low speeds but resulted in rear instability at high speeds. With the new aero, hairpin turns were unaffected, but the Exige was much more planted in medium and high speed corners such as T4, T6, and T9. In fact, the car even seemed to understeer in 4th gear turns.

The added stability allowed much more entry speed and throttle use. I could not seem to get on the throttle early enough in T3; adding throttle at the apex seemed to reveal more and more grip. Due to the lack of drama, understeer, and lower top speed, I was convinced that the overall laptimes were slower, but I was very surprised to see a best time of 1:38.2 when I pulled the data. That's almost 2 seconds faster than the last outing!

The best way to convey the feeling of track aero is adding all of the additional grip and stability of a 200-pound passenger without any of the inertia.

While there are significant grip and stability benefits to track aero, there are some tangible compromises, too. First, it is necessary to drive much more carefully on the street to avoid damaging the front splitter and rear diffuser. Many driveways and speed bumps require the driver to slow down to a crawl, and many obstacles are simply impassable. Second, the top speed fell by 6mph (125mph vs. 119mph peak). Perhaps some of the loss in straight line speed can be regained with a small reduction in the angle of attack.

The Trackspec team is looking forward to additional tuning and next season's SpeedSF Challenge events!

Last edited by smurfm3; 09-03-2018 at 05:02 PM.
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