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      02-09-2020, 04:38 PM   #43
Max Well
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Drives: '20 BSM X3MC, '20 PB X3MC
Join Date: Jun 2014
Location: Southeast USA

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Update – Round 2 Data

Intro: First, I wish to give a round of applause to the Staff of the Raceway and all of the Volunteers who worked so hard to get it open for Saturday morning’s Event, considering the severe weather that rolled through just 36 hours previous. There was still some work to be done Saturday morning, so the start was delayed from 10AM until 11AM, and there was an occ glitch in which an interval time didn’t measure on some runs (two of mine), but really great work by them.

It was a perfect day for performance engines, and I knew as soon as I left home with frost on the roof and crystal blue skies overhead. Because of the large turnout and the delayed starting time, I also knew I wouldn’t be able to run as many attempts as I did my first time out (11 that time), so that altered the strategy I had previously planned. I wasn’t sure if I was even going to be able to get four runs in, so I started with one Sport+/D3/Sport+ run, then figured I needed to hit LC every chance I got.

The differences from Round 1 mainly centered on a much better DA, beginning at -361 and ending at +14. We don’t have many opportunities to run in such pristine conditions at this Raceway as it is used throughout the year for professional runs and serious hobbyists with slick and drag radials only, so I definitely wanted to run max out on each attempt. As I noticed a lack of grip the last time out using BMW’s rec tire pressures of 33 front/38 rear, which definitely hampered my 0-60 foot times, I ran 32 Front/35 Rear this time. I know kingmonkeyjr had suggested 32 psi all around, but I didn’t want to make such a big jump down with this being only my second visit to the Raceway. Surely there is a sweet spot with our X3MC, so I wanted an intermediate data point for this series, and then next time figured I can try lowering the rears to 32 psi as well.

Gas was the same, just Shell 93 Octane, and this time tank volume was down to 5/8 for a starting point ending up at 3/8 tank at the end.

Results: What a difference with LC this time around – I had no trouble whatsoever setting the launch. Obviously if one were racing to see who gets across the finish line first as opposed to time slip results that would create a problem, since one only has 1.5 sec when the lights start and it has been suggested in previous discussions, we need roughly 3 sec for max boost build. Because you never know the abilities of the competition in the next lane or the timing start sequence (at least here I couldn’t judge that), hard to start building boost until you see the first yellow. So forget the R/Ts as I was totally ignoring that aspect.

Best ET for the ¼ mile was 11.671 s @ 117.81 (in which Dragy showed the 0-60mph time was 3.60 s, with the 1’ rollout like C&D and others use as 3.40 s). Best Speed for the ¼ mile was final round with ET 11.744 s @ 118.80. And to stress again, this is just bone stock, with a half tank of pump gas Shell 93 Octane.

Can’t count the number of folks who came up to me in the pre-staging lanes to remark they couldn’t believe what our X3MC is capable of laying down. Quite a sleeper visually (which personally I prefer but I understand others wish for the more aggressive aesthetic), but don’t mess with it when serious performance is desired.

Next time out, I would like to lower the rears to 32 psi as mentioned and begin with less fuel in the tank. Unfortunately, it appears that ‘All Welcome test-n-tune’ Events like this one which allow street tires may not be available again at this high echelon Raceway until early December (if I'm reading the printed year's schedule provided on Saturday correctly), so I'm not holding my breath on when I can get those trials done. And I heard for the first time around 1215PM the Announcer mentioning the ‘Sunoco Race Gas station was closing in 15 minutes, so if you need race gas you need to head right over.’ The fourth try would be to add race gas to raise the octane. Those incremental steps in slightly changing parameters should allow a better idea as to how much effect each change produces.

And one other point – it seems everyone always looks at the ET, but if you look at my final run, all of the interval times except for the 0-60 foot were essentially won in that last race (ignoring the .003 difference in the 60’-330’). So, the difference was totally in the 0-60’ interval (0.161 s). Subtract that 0.161 from the ET of that run of 11.744 yields 11.583 s for a very realistic and objectively documented ¼ mile time. Bone Stock. Shell 93 Octane, half a tank of gas, and DA +14.

Really liking this X3MC – once again thanks to BMW for their design and engineering on this model.
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