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      05-12-2020, 04:35 PM   #133
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Quote:
Originally Posted by GT500R View Post
Depends on the track prep also, if drivers were noticing that they were not getting traction in Nov'19 vs. getting better numbers in Feb (lower DA hinders traction but helps with ET's, especially with a 1100 DA swing) it could account to better track prep combined with cooler temps. More to this then just moving the tire pressure down unfortunately (DA, track prep, tires more worn in, previous person running down the lane, etc. etc.).

Just noticed:
3 PSI in the rear and 1 PSI in the front won't make that much of a difference based on my drag racing experience of 100+ runs down the track.
No question a lot of variables go into the final result. But - my tires did spin in Nov with psi 33/38. The tires did not spin in Feb with psi 32/35. At a high-end track like GNV, I suspect their prep is consistent so will discount that (and as gross observation I've sat there in the ready lanes watching them both times before rounds began, and the time spent and machinery used was the same to my untrained eye). Previous person running down the lane can alter a single run time, but I purposely switch up lanes each day, and I also averaged the data, and if you look at the spread it is consistent so that doesn't seem to be key. The other Drivers I spoke with having traction issues on both days were either serious hobbyists but from out of town and unfamiliar with the track, or regular street guys like me without a lot of experience there, so probably comes down to knowing the settings at your home track.

There doesn't seem to be much data discussing 'tire psi vs performance' at drag strips that I could find online. Some links are available but aren't vetted analyses and seem to be written mainly for upper echelon Drivers, which discuss making only 1/2 psi adjustments at a time for drag slicks and radials. Kingmonkey mentioned he runs 32/32 if I recall correctly in his modified GLC63? I think one of our UK colleagues also runs lower than OEM psi? Would be interested in reading what others have found with their F97/98 runs.
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      05-12-2020, 07:11 PM   #134
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Correct, not much behind street tires and pressure changes, but the concept extensions the same, lower the pressure for more contact patch. I doubt even 3 psi provided a 1/2” extra patch (I’m sure there are calcs out there). Point is you have better runs And that’s awesome but I wouldn’t say it’s all due to tire pressure.
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Last edited by GT500R; 05-12-2020 at 07:19 PM..
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      05-12-2020, 08:09 PM   #135
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Both of you are correct. Several factors have contributed to those improved times, with lower tire pressure being a significant contributor.
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      05-14-2020, 04:33 PM   #136
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Quote:
Originally Posted by GT500R View Post
Correct, not much behind street tires and pressure changes, but the concept extensions the same, lower the pressure for more contact patch. I doubt even 3 psi provided a 1/2Ē extra patch (Iím sure there are calcs out there). Point is you have better runs And thatís awesome but I wouldnít say itís all due to tire pressure.
I did a rough analysis of psi vs contact patch area with my X3MC with Michelins and attached to the daily threads ( https://x3.xbimmers.com/forums/showthread.php?t=1720559 ). Interesting difference with even small psi adjustments, but the only way to know if they are significant is at the track/strip. I'm betting they are, at least at GNV Raceway, but may not be on open roads. Data from future runs may help clarify the importance of psi and DA here at GNV.
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Last edited by Max Well; 05-20-2020 at 08:35 AM.. Reason: Updated to now include 21 and 24 psi data points
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      05-24-2020, 09:17 AM   #137
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Did a quick interval comparison between a few stock X3MC formal slips and the Meth injection Dragy run bmw_romy shared at: https://x3.xbimmers.com/forums/showthread.php?t=1723080

Maximum time difference found in the 60'-330' with a slight downward trend thereafter. Wonder if a lower tire psi would've allowed an even faster 0-60 foot as the power increase is definitely there? Don't know if he has spare (looks like moon roof is there) or tank volume.
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      05-26-2020, 08:54 AM   #138
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Quote:
Originally Posted by Max Well View Post
Did a quick interval comparison between a few stock X3MC formal slips and the Meth injection Dragy run bmw_romy shared at: https://x3.xbimmers.com/forums/showthread.php?t=1723080

Maximum time difference found in the 60'-330' with a slight downward trend thereafter. Wonder if a lower tire psi would've allowed an even faster 0-60 foot as the power increase is definitely there? Don't know if he has spare (looks like moon roof is there) or tank volume.
35-36 psi from and 39 psi in the rear for the run below. Yes sunroof and yes spare with 1/4 tank gas - just 93 octane, no mix.

This is just 93 octane OTS tune with a near 0 DA. You can see where the HP starts to really take over and that MPH is crushed with downpipes, E blended gas and Meth.
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      05-26-2020, 12:34 PM   #139
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Quote:
Originally Posted by GT500R View Post
35-36 psi from and 39 psi in the rear for the run below. Yes sunroof and yes spare with 1/4 tank gas - just 93 octane, no mix.
This is just 93 octane OTS tune with a near 0 DA. You can see where the HP starts to really take over and that MPH is crushed with downpipes, E blended gas and Meth.
Interval analysis attached. I don't know enough about methanol injection to know when it's effects are maximized, but at least based on the diff between the St1 and romy's, looks like a pretty consistent and solid 0.12-0.13s/interval after 330 feet.
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      05-26-2020, 12:45 PM   #140
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Just for comparison, here are the best dragy results I could find on yt for the new stock X6M Comp. A tiny bit quicker than F97 Comp.
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      05-26-2020, 01:49 PM   #141
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Quote:
Originally Posted by Max Well View Post
Interval analysis attached. I don't know enough about methanol injection to know when it's effects are maximized, but at least based on the diff between the St1 and romy's, looks like a pretty consistent and solid 0.12-0.13s/interval after 330 feet.
I'm not the cool kid with a Comp

So just regular X3M for me
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      05-26-2020, 02:54 PM   #142
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Quote:
Originally Posted by AlexFL View Post
Just for comparison, here are the best dragy results I could find on yt for the new stock X6M Comp. A tiny bit quicker than F97 Comp.
Thanks, Alex - that would be an interesting match at a strip. It'd be close but I'd bet on the X3MC in a 'best of' series if both have similar settings (octane, fuel tank vol) and proper LCs.

Quote:
Originally Posted by GT500R View Post
I'm not the cool kid with a Comp

So just regular X3M for me
Sorry . Here' a corrected version, and I've added interval analysis of your St1 X3M vs my stock X3MC (Dragy vs slip). Once the Strip opens and you get the chance, can you revert back to Stock for a few runs like you did with your G01 so we can get some formal stock X3M data as well?
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Last edited by Max Well; 05-26-2020 at 02:59 PM.. Reason: Had to correct 'X3MC' to 'X3M' in the interval analysis
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      06-15-2020, 06:27 AM   #143
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Added forza1976 fastest run to the X3MC Stock page. His thread at: https://x3.xbimmers.com/forums/showthread.php?t=1728438 . Remarkably close agreement to the interval times between 330'-1320' despite the wide variation in octane, DA, and overall weight. Was Lemongrease planning on submitting his slips from Bandimere as well?
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Last edited by Max Well; 06-15-2020 at 06:50 AM.. Reason: Forgot to add link to forza1976's thread
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      07-02-2020, 04:22 PM   #144
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For those with tunes, it would seem the ideal evaluation would be running pure stock at a sanctioned Strip followed by variations of tune settings within a time-frame where DA, tires, engine temps are similar. We've all seen how conditions change throughout the course of a day, so making runs close together would control the conditions.

Would be interested in seeing those slips for apples-apples comparisons. And to see what the X3MCS will be capable of...
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      07-13-2020, 12:34 PM   #145
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Max Well I might get to the track today. Can you refresh how to do launch control. I got it to work a couple times back when I first got Draggy. Now I can't get it.

I thought it was all settings to max, Manual shifting in 1, and then brake & gas to the floor and let go?

I tried that the other day and it wasn't working. Am I missing a step?
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      07-13-2020, 12:43 PM   #146
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Quote:
Originally Posted by RoyB View Post
Max Well I might get to the track today. Can you refresh how to do launch control. I got it to work a couple times back when I first got Draggy. Now I can't get it.

I thought it was all settings to max, Manual shifting in 1, and then brake & gas to the floor and let go?

I tried that the other day and it wasn't working. Am I missing a step?
Make sure MDM is off under the dsc settings.
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      07-13-2020, 02:12 PM   #147
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Originally Posted by MJDBMW View Post
Make sure MDM is off under the dsc settings.
I hit DSC button and it shows MDM Sport on the dash with the traction off/limited sign.
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      07-13-2020, 02:32 PM   #148
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Quote:
Originally Posted by RoyB View Post
Max Well I might get to the track today. Can you refresh how to do launch control. I got it to work a couple times back when I first got Draggy. Now I can't get it.

I thought it was all settings to max, Manual shifting in 1, and then brake & gas to the floor and let go?

I tried that the other day and it wasn't working. Am I missing a step?
Here you go: https://x3.xbimmers.com/forums/showp...9&postcount=14

It really is best, at least for me, to set my M2 button with these parameters, then when I pull up to the line and Staged lights up, I simply push it twice (you have to push it the second time to confirm you want to disable DSC) and you are all set. Push down hard on the brake with left foot, push accelerator quickly to the floor, count to three sec and let loose of the brake. Really is flawless if everything is set up in M2 correctly.

Looking forward to some slips!

Last edited by Max Well; 07-13-2020 at 02:42 PM..
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      07-13-2020, 03:05 PM   #149
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Quote:
Originally Posted by Max Well View Post
Here you go: https://x3.xbimmers.com/forums/showp...9&postcount=14

It really is best, at least for me, to set my M2 button with these parameters, then when I pull up to the line and Staged lights up, I simply push it twice (you have to push it the second time to confirm you want to disable DSC) and you are all set. Push down hard on the brake with left foot, push accelerator quickly to the floor, count to three sec and let loose of the brake. Really is flawless if everything is set up in M2 correctly.

Looking forward to some slips!
Yup, that did it. Thank you! I forgot I set it like that before and changed it to traction control back on since it was all over on the colder weather.

Also found out track is closed today. Maybe tomorrow if the weather holds out.
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      07-14-2020, 04:13 PM   #150
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Didn't get to the track yesterday and today isn't looking good for getting out of the office. I managed to get one decent run yesterday with Draggy. However, shifting into 4th it felt like boost dropped. Turns out it tripped a boost safety and went into safety mode. Still managed to click off a 11.52 with limited boost into 4th. It was approx 72 degrees out and I was running Map 2 on a JB4. Now I raised the limit a couple PSI hopefully I can get a full pass clean soon. Unfortunately it's hard to find a clean 1/2-1 mile road by me to make some passes..

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      07-15-2020, 03:40 PM   #151
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Heading to the track in NH tonight with some of my RS3 buddies and a buddy with a C8. I CANNOT wait! I'll post slips later tonight
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      07-15-2020, 09:37 PM   #152
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Didn't get a chance to mess with tire pressures, but put down a respectable time for only getting in three runs. DA was 600, tire pressures 35 all around, and 3/4 of a tank. Car 222
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      07-16-2020, 12:15 PM   #153
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Quote:
Originally Posted by robopp View Post
Didn't get a chance to mess with tire pressures, but put down a respectable time for only getting in three runs. DA was 600, tire pressures 35 all around, and 3/4 of a tank. Car 222
Thanks for sharing, robopp. If you can, might be helpful to share images of your other two slips (even if they were slower). I can place all three on the track spreadsheet so interval times can be compared - you can always learn something from slips, even if they weren't the fastest ET/mph.

Also, it'll be important to know if stock or tune (and if tuned, which brand and which setting for each slip's run), octane of fuel (and Brand), and whether you have moon roof and spare? Trying to provide as much data as we can to allow comparison of tunes and what role octane, weight, etc. play in final results.
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      07-16-2020, 12:21 PM   #154
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Quote:
Originally Posted by Max Well View Post
Quote:
Originally Posted by robopp View Post
Didn't get a chance to mess with tire pressures, but put down a respectable time for only getting in three runs. DA was 600, tire pressures 35 all around, and 3/4 of a tank. Car 222
Thanks for sharing, robopp. If you can, might be helpful to share images of your other two slips (even if they were slower). I can place all three on the track spreadsheet so interval times can be compared - you can always learn something from slips, even if they weren't the fastest ET/mph.

Also, it'll be important to know if stock or tune (and if tuned, which brand and which setting for each slip's run), octane of fuel (and Brand), and whether you have moon roof and spare? Trying to provide as much data as we can to allow comparison of tunes and what role octane, weight, etc. play in final results.
Sure thing. First two times were due to my learning how to launch correctly. On my last launch I held it for a good five seconds and could absolutely feel the difference. Fuel was 93 speedway (I wasn't planning on going to the track; wish I would have used better fuel), but I topped it off with some E85 (3 gallons) to a full tank. No tune, fully stock on factory P4Ss, I have a moonroof, and no spare.
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