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XBimmers | BMW X3 Forum BMW X3/X4 Forums Third Generation BMW X3 (G01) General Forum (2017+) G01 X3 xDr 1/4 Mile Thread

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      06-26-2017, 02:51 PM   #1
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G01 X3 xDr 1/4 Mile Thread

As technical specifications were released today, thought I might as well run this now while I had some time. In earlier real-life comparisons with the F25 and F26, the Sim proved able to model actual data curves reasonably well (with appreciation to Rob, Crash and others who shared their times and videos for comparison with the sim). I'm hopeful that trend continues with this line-up, but as always, a disclaimer - I don't have a background in fluid dynamics or automotive engineering so this is just a lay attempt at understanding the G01's potential.
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      12-16-2017, 05:18 PM   #2
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Sim vs AutoTopNL real on the Autobahn

With meanmusic's kind addition of the AutoTopNL video, I screen-captured the visualized speedometer vs an online stopwatch since none was available. Although a number of variables are unknown (such as tires, psi pressure, road grade, wind direction, vehicle weight, actual speedometer from dash insturmentation, and the vagaries of the indicated speed not showing a smooth transition), it provided a chance to at least add some data vs the sim. Many thanks to meanmusic for sharing the video here.
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      04-23-2018, 09:05 AM   #3
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G01 Drag Slips from Seaz

As Seaz provided the first drag slips for the G01 X3 M40i ( http://x3.xbimmers.com/forums/showthread.php?t=1488754 ) I'm posting them in Spreadsheet format along with Notes and Interval times. By way of comparison/reference, am also attaching FSociety's F26 X4 M40i times he ran back in 2016. The red highlights indicate the fastest interval time for each Driver (makes it easier to detect how setting changes may affect performance through different segments when a number of tickets are entered). For example, although Seaz Run 658 was his fastest ET and MPH of his two runs, his interval times were actually faster in Run 235 illustrating a slower 60 ft launch in that run.
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      06-22-2018, 07:59 AM   #4
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Emmanuel.yoo's data added

As emmanuel.yoo has contributed another formal drag slip [ http://x3.xbimmers.com/forums/showthread.php?t=1508670 ], I'm updating the spreadsheet and also plotting it against the stock and hypothetical X3 M's with varying HP. His data lands almost exactly on the 400 HP curve.

Will be interesting to see slips from tracks which also provide 1000' data to enable full split times analysis, as well as a formal slip for a '100% stock run' to serve as a reference with which to compare various modifications.
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      06-22-2018, 08:22 AM   #5
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Thank you @Max Well for putting this together. If I’m reading this correctly, it takes an additional 135hp to shave 0.5 seconds off the 0-60 time?
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      06-22-2018, 09:03 AM   #6
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Great thread! Happy to contribute
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      06-22-2018, 09:06 AM   #7
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Here you will have my official dragy times if it can help. You even have the 0-1000.
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      06-22-2018, 09:49 AM   #8
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Very interesting. Thanks for the info. Good job putting it together.
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      06-22-2018, 12:14 PM   #9
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Quote:
Originally Posted by emmanuel.yoo View Post
Here you will have my official dragy times if it can help. You even have the 0-1000.
Awesome. Can't wait to add intake and a tune. Waiting on the Dinan tune, hopefully available by August. With the M235, Dinan has various stage tunes that can get to over 100 hp/torque added. Crazy.
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      06-22-2018, 01:40 PM   #10
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Quote:
Originally Posted by Pretzel View Post
Thank you @Max Well for putting this together. If Iím reading this correctly, it takes an additional 135hp to shave 0.5 seconds off the 0-60 time?
At least based on this rough approximation it does, which shouldn't be taken as Gospel for what the actual will be. The early phases of the curve are an estimation because of the complexities of take-off and the host of variables that come into play during that phase of acceleration (tires, road friction, drivetrain efficiency, ...).

As background - back in 2014 when I was researching how to calculate acceleration for different vehicles, it became readily apparent that I wasn't going to be able to model real-life curves the way professional software can (not only because I don't have any knowledge of this field but because of the complex equations needed which I couldn't ever clearly find, and the ones I did find I didn't understand!). But I wanted at least a layman's way of understanding this, so this Sim was produced.

The main issue it has to figure out during early acceleration is the maximal amount of power which can be put down and used to accelerate the vehicle. Too much and the wheels just spin without producing forward motion of the vehicle. So the sim takes the vehicle weight, uses rough coefficients for road surface friction and that of the tires, and a constant placed here and there along with the efficiency of the engine to transfer the power to the wheels to come up with a maximal amount of power such a vehicle can apply before the wheels spin and lose grip with the road. It then uses this power until a speed is reached where the tires shouldn't spin and the power available to the vehicle then becomes fully useful. In other words, if one had two identical X3 M40i G01s next to each other on a track, one might argue that even stock the 355 HP would cause the tires to spin early on. So whether one could modify one to have 555 HP, if the tires and everything else is equal, if the 355 is going to spin the tires then so will the 555 HP, so nothing is gained by having that additional power. That is until the road surface and tire friction coefficients allow grip when that extra HP can be utilized.

So in this sim, oftentimes the first 3 seconds or so are identical even if I change the HP, because that is the time needed for the coefficients of friction I am using to allow a vehicle's aerodynamics and HP variables to become relevant when the tires and road surface have 'full grip' if you will.

As such, I've not focused too much on this first three seconds of acceleration in the sim, but I've been pleasantly surprised at how close it approximates some of the real world data at the higher speeds which Forum Members have shared (FSociety and others). If I were more knowledgeable of the calculations and science I could probably massage the parameters if we had a lot of data series, but that is way over my head and would require the addition of detailed tire and rubber info, track surface data, atmospheric variables, ... - so most definitely over my head and not something I'm ever going to pursue!

For 0-60mph times, it seems that wt/HP vs 0-60 mph chart I had shared some months ago might provide another idea, esp if you look at BMWs only, as it seems different Mnfrs have varying degrees of efficiency in that regards.
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      06-22-2018, 01:47 PM   #11
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Quote:
Originally Posted by emmanuel.yoo View Post
Here you will have my official dragy times if it can help. You even have the 0-1000.
And thank you, emmanuel.yoo. I think the Dragy and other methods of acceleration documentation are great, but for this Qtr mile thread I'm going to limit the spreadsheet data to formal drag strip tickets. It has nothing to do with doubting of those contributions for they have been shown to be quite accurate, but rather, set Drag Strip locations can be easily referenced for altitude and grade without guessing those parameters. Data on temperature, barometric pressure and humidity can also be added to the Spreadsheet if provided.

Thanks again for contributing.
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      06-22-2018, 02:20 PM   #12
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Quote:
Originally Posted by Max Well View Post
And thank you, emmanuel.yoo. I think the Dragy and other methods of acceleration documentation are great, but for this Qtr mile thread I'm going to limit the spreadsheet data to formal drag strip tickets. It has nothing to do with doubting of those contributions for they have been shown to be quite accurate, but rather, set Drag Strip locations can be easily referenced for altitude and grade without guessing those parameters. Data on temperature, barometric pressure and humidity can also be added to the Spreadsheet if provided.

Thanks again for contributing.
We could easily include the DA(Density Altitude) for you as well as the slope.

https://airdensityonline.com/track-f...xas_Motorplex/

https://airdensityonline.com/track-r...xas_Motorplex/
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      06-22-2018, 02:44 PM   #13
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Some good work there. Looks very well correlated as you’d expect for weight/hp and acceleration time. Thanks for the explanation.
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      06-22-2018, 05:13 PM   #14
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Quote:
Originally Posted by ParadigmDawg View Post
We could easily include the DA(Density Altitude) for you as well as the slope.

https://airdensityonline.com/track-f...xas_Motorplex/
Thanks for sharing that site - hadn't seen it before. Ideally, it'd be great if weather data could be included with drag slip submissions (and I'll definitely include on the spreadsheet when provided), but not sure everyone is into that level of detail. Seems like it would provide a better reference for those serious about mods and sorting out which variables account for performance changes. But then some may wonder why the interest in modding a(n) X3 at all? Those may be the uninitiated.
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      06-22-2018, 05:48 PM   #15
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Nice numbers. Thanks for gathering all the info.
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      06-22-2018, 06:24 PM   #16
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Awesome thread. Keep up the good work and I'll continue going to the drag strip! Can't wait for them to figure out a more efficient intercooler for the b58s!
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      06-23-2018, 05:16 PM   #17
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Quote:
Originally Posted by emmanuel.yoo View Post
Awesome thread. Keep up the good work and I'll continue going to the drag strip! Can't wait for them to figure out a more efficient intercooler for the b58s!
Thanks, emmanuel.yoo. I'm attaching an updated spreadsheet with added numbers (your weight, gas tank status, temperature, humidity, and since your Dragy was roughly a consistent .05 sec slower across all times c/w the slip I subtracted .05 from your Dragy 1,000 ft time so we can have a rough idea of your full interval times - but left a slight cell fill color to note it was not slip-derived).

Question for those with drag strip experience - are tire sizes and pressures ever entered into data charts for evaluating future modifications and comparing different vehicle runs? It would seem 19" vs 21" and different tire pressures would have some effect? And do you want your pressures at rec settings for better grip at take-off or firmer for faster at higher speed (or does tire pressure make much difference at the strip)?
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      06-26-2018, 08:39 AM   #18
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I calculated emmanuel.yoo's DA using the website shared by GGEVOX in thread, http://x3.xbimmers.com/forums/showpo...7&postcount=16, found at [ http://www.dragtimes.com/da-density-...ect+ET+and+MPH ], using archived weather data from Montreal for his 21 Jun 2018 735PM drag run found at [ https://www.timeanddate.com/weather/...treal/historic ]. Note the corrected ET and MPH using the DA for modified turbocharged engines, per that website calculator, are 12.347s @ 109.138 MPH.

I was unable to do the same for Seaz' previous runs as I couldn't see his date and time stamps on his Drag Slips.

The DA will be very helpful for comparisons of various mods and fuels so hopefully future submissions can include this information.
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      07-02-2018, 12:44 PM   #19
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GT500R's stock runs from 29 Jun 2018

GT500R added slips from multiple stock runs at Island Dragway on 29 Jun 2018 (at http://x3.xbimmers.com/forums/showthread.php?t=1511311 ). I placed this information chronologically in a spreadsheet along with the DA values he provided, and also calculated 'corrected ET/MPH' values based on his DAs (calculator found at the dragtimes.com site mentioned in an earlier post).
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      09-07-2018, 08:01 AM   #20
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Updated spreadsheet with emmanuel.yoo's data from yesterday - https://x3.xbimmers.com/forums/showp...0&postcount=22 . Weather data enabling DA calculation from websites as noted in post from 26 Jun 2018 0939AM.
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      10-16-2018, 07:25 AM   #21
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GT500R's Mission Performance Stage 2 runs 12 Oct 2018

Added GT500R's data (from his thread at https://x3.xbimmers.com/forums/showthread.php?t=1544788 ), with the added detail of chronology of time and DAs provided by him in a PM.
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Last edited by Max Well; 10-18-2018 at 04:12 AM. Reason: Shortened text
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