The official short shifting bench racing thread

[drob23]

Very cool guys… I think the launch rpm’s are a little off as the 60’s seem high especially given the et’s and traps… The last set by Jim seem spot on et and mph wise but 60 still seems high… The whole DA throws a wrench into it but if you look at the top times their done in 0 or negative DA’s so it’s pretty close IMO… It’s early so I need to read it again and digest it better! lol Appreciate you guys doing this, again great stuff!

Thanks for the feedback Ron, yea I think the launch will always be the worst. In the real world, I believe pneumatic tires almost act like slingshots or springs when you first load them up. So even getting max torque at launch (at approx 4000 RPM) still results in slower 60’s than you guys produce. Not sure we can fix that without hacking up the equations to artificially get the result we want (which we already sort of do with the dyno lol).

The DA thing will never make it into this, we just assume the engine does whatever the dyno says. I guess the APR dyno is probably better than actual, since they remove the wheels? But we can scale it however we want (i.e. add in drivetrain loss), so it can be tuned to give a certain desired result I suppose.

[drob23]

Added extra torque during launch to help with the 60ft, now appears to be about 1.7 sec for stg 2. I’ll put up the figures when I get home.

Does anyone have any ideas as to how to present the results to give it some kind of “conclusion” feel?

Anyone have any suggestion to the sort shifting values? Ie 5900 and then 6300 for sort shifting, 7200 at every gear for b8/dsg flash?

Ideally, we can end this thread with some reasonable conclusions…ie something to show Arin to convince him that short shifting isn’t completely responsible for poor performance. Thanks all and would also appreciate criticism of methods/assumptions.

[b5b4b8]

Thanks all and would also appreciate criticism of methods/assumptions.

Here is a thought on the 60’ times. Adding extra torque seems wrong to me, but…

Typically good 60’ times (and ET) are achieved by staging shallow. I think there is about 1’ of distance between the beams (?) – so … looking at my sims - 1’ of travel occurs in little over .2 seconds - so that would put the 60’ times as measured by the strip when you shallow stage down in the 1.6 range where primetime and the other dragstrip legends are

It would also cut the same amount of time off the ET, but not change the trap.

However – trap speed - it’s actually an average over the last several feet I think - we could model it that way as well to maybe make it more 1-1 vs. a timeslip…

[drob23]

Thanks all and would also appreciate criticism of methods/assumptions.

Here is a thought on the 60’ times. Adding extra torque seems wrong to me, but…

Typically good 60’ times (and ET) are achieved by staging shallow. I think there is about 1’ of distance between the beams (?) – so … looking at my sims - 1’ of travel occurs in little over .2 seconds - so that would put the 60’ times as measured by the strip when you shallow stage down in the 1.6 range where primetime and the other dragstrip legends are

It would also cut the same amount of time off the ET, but not change the trap.

However – trap speed - it’s actually an average over the last several feet I think - we could model it that way as well to maybe make it more 1-1 vs. a timeslip…

Damn Jim, that’s pretty genius :o

Bench racing FTW - shallow staging by 1 ft reduces the 60 ft by .22 sec when considering APR stg 2 dyno.

For those interested, found a nice reference for doing essentially exactly what we’re doing: http://www.wskc.org/documents/281621/308637/ENGAGE_E3S_Dynamics_DragRacing.pdf/6d7a264e-246f-4a70-8f91-677697fc20d4

I liked this line ;D: Even with the simplifying assumptions, the calculated results are
strikingly close to the published results.

[b5b4b8]

Damn Jim, that’s pretty genius :o

For those interested, found a nice reference for doing essentially exactly what we’re doing: http://www.wskc.org/documents/281621/308637/ENGAGE_E3S_Dynamics_DragRacing.pdf/6d7a264e-246f-4a70-8f91-677697fc20d4

LOL - no a genius would have thought of this from the beginning… >:(

Nice reference. Shift RPM = 5500 - and you B8.5 DSG guys are complaining

[sakimano]

Thanks all and would also appreciate criticism of methods/assumptions.

Here is a thought on the 60’ times. Adding extra torque seems wrong to me, but…

Typically good 60’ times (and ET) are achieved by staging shallow. I think there is about 1’ of distance between the beams (?) – so … looking at my sims - 1’ of travel occurs in little over .2 seconds - so that would put the 60’ times as measured by the strip when you shallow stage down in the 1.6 range where primetime and the other dragstrip legends are

It would also cut the same amount of time off the ET, but not change the trap.

However – trap speed - it’s actually an average over the last several feet I think - we could model it that way as well to maybe make it more 1-1 vs. a timeslip…

staging = pretty close. Maybe 10" is more accurate.
trap speed = average speed over final 60 feet of the track

[Skywagon]

There is a thread over on AZ in which a gent that owns a 2015 S4 claims his tachometer face redline is 7000 RPM and that is where his DSG shifts. My blood pressure is going up!!!

http://www.audizine.com/forum/showthread.php/614935-So-Everyone-Is-OK-With-Audi-Not-Allowing-DSG-Cars-To-Get-To-Redline

[drob23]

Thanks all and would also appreciate criticism of methods/assumptions.

Here is a thought on the 60’ times. Adding extra torque seems wrong to me, but…

Typically good 60’ times (and ET) are achieved by staging shallow. I think there is about 1’ of distance between the beams (?) – so … looking at my sims - 1’ of travel occurs in little over .2 seconds - so that would put the 60’ times as measured by the strip when you shallow stage down in the 1.6 range where primetime and the other dragstrip legends are

It would also cut the same amount of time off the ET, but not change the trap.

However – trap speed - it’s actually an average over the last several feet I think - we could model it that way as well to maybe make it more 1-1 vs. a timeslip…

staging = pretty close. Maybe 10" is more accurate.
trap speed = average speed over final 60 feet of the track

Makes sense about trap speed, since they’d need a way to calculate it to begin with: trip first laser beam slightly before and second beam at end of 1/4 mile, then divide distance by time delta. I’ll change the sim to reflect this.

It lowers the trap speed by about .8 MPH if you average last 60 ft vs taking instantaneous velocity.

[drob23]

There is a thread over on AZ in which a gent that owns a 2015 S4 claims his tachometer face redline is 7000 RPM and that is where his DSG shifts. My blood pressure is going up!!!

http://www.audizine.com/forum/showthread.php/614935-So-Everyone-Is-OK-With-Audi-Not-Allowing-DSG-Cars-To-Get-To-Redline

He’s just eyeballing it and guesstimating. The 2015 is no different from the 2014…just relax ;D

[Skywagon]

There is a thread over on AZ in which a gent that owns a 2015 S4 claims his tachometer face redline is 7000 RPM and that is where his DSG shifts. My blood pressure is going up!!!

http://www.audizine.com/forum/showthread.php/614935-So-Everyone-Is-OK-With-Audi-Not-Allowing-DSG-Cars-To-Get-To-Redline

He’s just eyeballing it and guesstimating. The 2015 is no different from the 2014…just relax ;D

I hope you are correct. Can’t see how anyone could read misread a tach that badly? I may just go past my dealer today and look for myself. I better take some meds!