R44 Performance
BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read

Go Back   BMW M3 and BMW M4 Forum > BMW F80 M3 / F82 M4 Technical Topics > Track / Autocross / Dragstrip / Driving Techniques

Post Reply
 
Thread Tools Search this Thread
      12-11-2014, 09:09 PM   #1
FTS
Enjoying driving
FTS's Avatar
United_States
388
Rep
1,169
Posts

Drives: 645
Join Date: May 2009
Location: MD

iTrader: (0)

DCT vs Manual - How Much Vehicle Speed Gained During Upshifts?

I am wondering how much speed difference can be expected between an upshift with the DCT vs. manual. I don't intend this question to be another "DCT vs. manual, which is better?" perspective, but more so as a technical question; does the DCT offer real and measurable speed advantage during upshifts? Of course there are benefits I see also on the downshifts, but for this discussion, I thought we just focus on upshifts.

For example, it generally takes me between 0.6 to 0.8 secs to do an upshift in a manual on the track, this is the time between throttle off and back on (WOT). Obviously the speed difference between the two methods will depend on beginning speed and accel G, but I thought may be someone may have more specific opinions and/or data on this. Hopefully it will be a positive, informative discussion
Appreciate 0
      12-11-2014, 09:17 PM   #2
gthal
Major General
gthal's Avatar
Canada
1901
Rep
5,678
Posts

Drives: 2018 340i xDrive
Join Date: Jul 2007
Location: Canada

iTrader: (2)

Doesn't the DCT shift in something like 80ms? That and there is effectively no throttle lift. The reason DCT cars are almost invariably faster in a straight line is faster shift speed and no throttle lift.
__________________
2020 X3 M40i | Black | Current DD
2020 C8 Corvette | Z51 | Torch Red ... built and waiting for delivery
2016 M2 | Long Beach Blue | 6MT
2015 M4 | Austin Yellow | DCT
2012 MB C63AMG | 2011 E92 M3 | 2010 E92 M3
Appreciate 0
      12-11-2014, 09:27 PM   #3
FTS
Enjoying driving
FTS's Avatar
United_States
388
Rep
1,169
Posts

Drives: 645
Join Date: May 2009
Location: MD

iTrader: (0)

@gthal, if I remember what I read correctly couple of months ago, I think it is 100 ms in S3 and with minimal LatG load. Regardless it is certainly much faster than I can shift (at least half sec ). However, what does that mean in terms of actual speed, and also related to that what does that mean in terms of secs gained? I think the differences may be surprising.

As an example, the attached graph shows one instance in which I chose to shift from 3rd to 4th, and another instance which I stayed in 3rd, no shift, no throttle interruption (not a BMW). The difference in speed was nearly 8 mph, which I was not expecting.
Attached Images
 

Last edited by FTS; 12-11-2014 at 09:32 PM..
Appreciate 0
      12-11-2014, 10:15 PM   #4
CanAutM3
General
CanAutM3's Avatar
Canada
21105
Rep
20,741
Posts

Drives: 2021 911 turbo
Join Date: Jan 2012
Location: Montreal

iTrader: (1)

Garage List
Quote:
Originally Posted by gthal View Post
Doesn't the DCT shift in something like 80ms? That and there is effectively no throttle lift. The reason DCT cars are almost invariably faster in a straight line is faster shift speed and no throttle lift.
It all depends how "shift time" is defined. It probably does take 80~100ms to complete the shift per se, meaning that it takes that time for one clutch to fully dissengage while the other fully engages. The thing is that during that time, there is no interruption in the transmission of power to the rear wheels. So in terms of effective acceleration, it can be assumed that there is really a zero shift time; i.e. there is no time where the car stop accelerating during the shift. This translates to a huge benefit. The caveat is that the DCT weighs more and suffers from more loss than the 6MT. Now how much of that is offset by the faster shift times on the F8X is still open for debate.

By no throttle lift, I assume you mean power shifting, where the engine inertia is recuperated to be converted in vehicle forward momentum. It is to be noted that this can also be done with a 6MT.

On the E9X, the advantage was clear. I have done an analysis here on the the 6MT vs DCT on the E9X. The DCT gains about 0.2sec every time the 6MT needs to shift. Further, the DCT also benefited from tighter gearing to better exploit the power characteristics of the S65. While on track with my buddy that ran a 2012 ZCP 6MT E92 on the exact same tires and wheels as my civic 2008 E92, I have been repeatadly able to pull a clean pass on him on the back straight of our local track. When he would be behind me, I would just pull away. As much as I would like to claim that I am a better driver, I have to give that advantage to the DCT.

Further, comparing data logs of my buddies C5 Z06, the slope of his speed curve (hence his acceleration) was clearly steeper than the one of my E92. Yet, we could also clearly see that every time he shifted, the M3 would catch up to enventually finish with a higher terminal speed at the end of the straight.

Last edited by CanAutM3; 12-12-2014 at 10:36 AM..
Appreciate 0
      12-12-2014, 11:27 AM   #5
MaynardZed
Lieutenant Colonel
MaynardZed's Avatar
United_States
1231
Rep
1,789
Posts

Drives: wife crazy
Join Date: Jul 2014
Location: Phoenix

iTrader: (0)

Garage List
There could be an additional advantage with the DCT in our S55 powered cars. Turbo lag is minimal, but we all know it's still there. The DCT may allow the turbos to remain spooled up and therefore experience less lag on upshifts.
__________________
Road course laptimes for BMW M4 2015 6MT
WHP East Track: 1:04.880, Arizona Motorsports Park: 1:54.352
Road course laptimes for Porsche 911 991.1 GTS 7MT
WHP East Track: 1:02.770, Arizona Motorsports Park: 1:48.889
Appreciate 0
      12-12-2014, 12:50 PM   #6
CanAutM3
General
CanAutM3's Avatar
Canada
21105
Rep
20,741
Posts

Drives: 2021 911 turbo
Join Date: Jan 2012
Location: Montreal

iTrader: (1)

Garage List
Quote:
Originally Posted by MaynardZed View Post
There could be an additional advantage with the DCT in our S55 powered cars. Turbo lag is minimal, but we all know it's still there. The DCT may allow the turbos to remain spooled up and therefore experience less lag on upshifts.
I agree it is a valid point. However, I wonder with the S55 anti-lag wizardry, how much boost is actually lost on a 6MT shift. My understanding of the anti-lag is that it is to counter lost boost coming from quick throttle lifts, which is exactly what happens during a shift. That is probably what causes the "farting" sounds on lift-off and on shifts.

Last edited by CanAutM3; 12-12-2014 at 01:23 PM..
Appreciate 0
      12-14-2014, 12:03 PM   #7
FTS
Enjoying driving
FTS's Avatar
United_States
388
Rep
1,169
Posts

Drives: 645
Join Date: May 2009
Location: MD

iTrader: (0)

Although @MaynardZed has a valid point, let's ignore that for the argument, I think we'll find that impact as we collect data at the track.

When I look at the data I have from my previous NA car, the shifting that happened in the graph is at 97 mph. If we assume both runs were at the same speed, the version of the data corresponding to the run in which I did not shift gained 2.6 mph during the 0.8 secs it took me to shift. Ignoring the continued speed difference increase after the shift, the data analysis software shows that time gained only during this period was 0.031 secs. If I do manual calculation with approximations and taking average speed during that 0.8 sec time period, I come up with 0.026 secs.

Either way it is not anywhere close to 0.2 secs per shift as @CanAutM3 calculated from his older thread, it is much smaller. Which is the reason I started this thread to see if I am missing something, because I would have believed at face value that "yes, 0.2 per shirt sounds about right." It may not be. Again, how this data will change for the F8x, I do not know, but I am looking forward to finding out
Appreciate 0
      12-14-2014, 12:29 PM   #8
CanAutM3
General
CanAutM3's Avatar
Canada
21105
Rep
20,741
Posts

Drives: 2021 911 turbo
Join Date: Jan 2012
Location: Montreal

iTrader: (1)

Garage List
Quote:
Originally Posted by FTS View Post
Although @MaynardZed has a valid point, let's ignore that for the argument, I think we'll find that impact as we collect data at the track.

When I look at the data I have from my previous NA car, the shifting that happened in the graph is at 97 mph. If we assume both runs were at the same speed, the version of the data corresponding to the run in which I did not shift gained 2.6 mph during the 0.8 secs it took me to shift. Ignoring the continued speed difference increase after the shift, the data analysis software shows that time gained only during this period was 0.031 secs. If I do manual calculation with approximations and taking average speed during that 0.8 sec time period, I come up with 0.026 secs.

Either way it is not anywhere close to 0.2 secs per shift as @CanAutM3 calculated from his older thread, it is much smaller. Which is the reason I started this thread to see if I am missing something, because I would have believed at face value that "yes, 0.2 per shirt sounds about right." It may not be. Again, how this data will change for the F8x, I do not know, but I am looking forward to finding out
I am not sure I follow your argumentation here

The 0.2 I reffer to is the time to speed difference. You are talking about time to distance. Which is not the same thing.

Note that the benefit of the speed gained during the shift extends beyond the period of the shift itself. That extra "2.6mph" benefits for the entire acceleration period that follows the shift, not only the 0.8s duration of the shift. I used your 2.6mph here, but your graph seems to show a gain closer to ~5mph in those 0.8 seconds; don't forget that the MT car actually decelerates during that time (negative g on your chart).

Going back to time to distance, in my E9X analysis, it shows the DCT crossing the ¼ mile mark 0.25 seconds faster than the 6MT. At 113mph, that is more than 40 feet, which is quite significant. Note that both "average" cars in my analysis are exactly matched from 0 to 40mph, so it is not a question of DCT launch control.

Last edited by CanAutM3; 12-14-2014 at 03:38 PM..
Appreciate 0
      12-14-2014, 12:33 PM   #9
MaynardZed
Lieutenant Colonel
MaynardZed's Avatar
United_States
1231
Rep
1,789
Posts

Drives: wife crazy
Join Date: Jul 2014
Location: Phoenix

iTrader: (0)

Garage List
Quote:
Originally Posted by FTS View Post
Although @MaynardZed has a valid point, let's ignore that for the argument, I think we'll find that impact as we collect data at the track.

When I look at the data I have from my previous NA car, the shifting that happened in the graph is at 97 mph. If we assume both runs were at the same speed, the version of the data corresponding to the run in which I did not shift gained 2.6 mph during the 0.8 secs it took me to shift. Ignoring the continued speed difference increase after the shift, the data analysis software shows that time gained only during this period was 0.031 secs. If I do manual calculation with approximations and taking average speed during that 0.8 sec time period, I come up with 0.026 secs.

Either way it is not anywhere close to 0.2 secs per shift as @CanAutM3 calculated from his older thread, it is much smaller. Which is the reason I started this thread to see if I am missing something, because I would have believed at face value that "yes, 0.2 per shirt sounds about right." It may not be. Again, how this data will change for the F8x, I do not know, but I am looking forward to finding out
Excellent point, never thought of it that way. You're right, even though the manual may be 0.8 secs slower per shift it's not like manual car is suddenly "paused in time" at a stand still on the track while the DCT pulls ahead. The manual car is "coasting" but at least proceeding down the track while the DCT car completes the shift quicker.

Newton's first law. An object in motion will stay in motion while the clutch is disengaged.
__________________
Road course laptimes for BMW M4 2015 6MT
WHP East Track: 1:04.880, Arizona Motorsports Park: 1:54.352
Road course laptimes for Porsche 911 991.1 GTS 7MT
WHP East Track: 1:02.770, Arizona Motorsports Park: 1:48.889
Appreciate 0
      12-14-2014, 01:49 PM   #10
CanAutM3
General
CanAutM3's Avatar
Canada
21105
Rep
20,741
Posts

Drives: 2021 911 turbo
Join Date: Jan 2012
Location: Montreal

iTrader: (1)

Garage List
Quote:
Originally Posted by MaynardZed View Post
Excellent point, never thought of it that way. You're right, even though the manual may be 0.8 secs slower per shift it's not like manual car is suddenly "paused in time" at a stand still on the track while the DCT pulls ahead. The manual car is "coasting" but at least proceeding down the track while the DCT car completes the shift quicker.

Newton's first law. An object in motion will stay in motion while the clutch is disengaged.
IMO, a skilled driver can lose much less than 0.8 seconds of acceleration time during a shift. My data shows it is closer to 0.2~0.3 seconds. Again here, that is in terms of time to speed, not time to distance. As you stated, the MT does not stop moving during the shift, it just stops accelerating (it actually even decelerates slightly due to rolling and aero drag).

So one cannot assume that a DCT lap will be faster by 0.2 seconds for every shift over a lap. Lap times are measured in time to distance, not time to speed. For example, three shifts are needed over the ¼ mile, but the DCT only has a 0.25 second advantage over the manual on that distance according to my analysis, not 0.6 seconds.

That being said, the DCT clearly has an edge due to the (almost) instant shifts. I don't know how much it loses because of the additional weight and losses. I am looking forward for more data points on the F8X DCT and 6MT so we can do more analysis.

Last edited by CanAutM3; 12-14-2014 at 02:28 PM..
Appreciate 1
      12-20-2014, 07:42 AM   #11
schmitzna
Private First Class
schmitzna's Avatar
United_States
54
Rep
121
Posts

Drives: 2015 M3
Join Date: Jul 2014
Location: Stokesdale, NC

iTrader: (0)

Garage List
2018 BMW X3 M40i  [0.00]
2015 BMW M3  [0.00]
Quote:
Originally Posted by FTS View Post
The difference in speed was nearly 8 mph, which I was not expecting.
If you lost 8mph from shifting, imagine the impact on lap time the quicker shift would have on a long straight. The faster shifting car keeps that 8mph advantage the entire time until the next braking zone. It is the same reason why the most important corner on the course is the one that leads to the longest straight.

Faster shifting gains way more time than just the time saved shifting.
Appreciate 0
      12-20-2014, 08:51 AM   #12
MaynardZed
Lieutenant Colonel
MaynardZed's Avatar
United_States
1231
Rep
1,789
Posts

Drives: wife crazy
Join Date: Jul 2014
Location: Phoenix

iTrader: (0)

Garage List
Quote:
Originally Posted by schmitzna View Post
If you lost 8mph from shifting, imagine the impact on lap time the quicker shift would have on a long straight. The faster shifting car keeps that 8mph advantage the entire time until the next braking zone. It is the same reason why the most important corner on the course is the one that leads to the longest straight.

Faster shifting gains way more time than just the time saved shifting.
I'm suspect of the 8mph advantage in the DCT, but if true its only held for a short period of time at the end of the straight just before the brake zone (actually has to start braking a tad earlier than the 6MT car).

Yes, agree the turn into the straight is very important, but has nothing to do with upshifting. In fact, theoretically, the 6MT (being lighter) should have a better entrance speed into the straight (all other things being equal). In reality, its driver skill that determines entrance speed.

This is anecdotal evidence of course, but another board member (his car is DCT) and myself (6MT) did the No Fly Zone AZ and our best 1/2 mile trap speeds were 144.8 (DCT) vs 144.5 (6MT). Unfortunately we did the event on different days so no head to head. I was powershifting, which I wouldn't typically do at an HDPE (unless passing maybe). On a road course maybe one of the biggest advantages of the DCT is consistency of the shifts since the 6MT guy will shift slower, even possible miss a shift every now and again.

Hopefully the next NFZ AZ we can meet up on the same day and get some head to heads done for more evidence. I'm hearing maybe March they'll be back for another event.
__________________
Road course laptimes for BMW M4 2015 6MT
WHP East Track: 1:04.880, Arizona Motorsports Park: 1:54.352
Road course laptimes for Porsche 911 991.1 GTS 7MT
WHP East Track: 1:02.770, Arizona Motorsports Park: 1:48.889
Appreciate 0
      12-22-2014, 03:01 PM   #13
CanAutM3
General
CanAutM3's Avatar
Canada
21105
Rep
20,741
Posts

Drives: 2021 911 turbo
Join Date: Jan 2012
Location: Montreal

iTrader: (1)

Garage List
Quote:
Originally Posted by MaynardZed View Post
I'm suspect of the 8mph advantage in the DCT
Rightfully so.

My analysis on the E9X shows a 2~3mph gain for each shift in the lower gears regressing to a ~1mph advantage in the higher gears.

Quote:
Originally Posted by MaynardZed View Post
but if true its only held for a short period of time at the end of the straight just before the brake zone
It all depends on the track layout and how much distance there is on the straight after the shift (or shifts). That distance can be quite long.
Appreciate 0
      01-07-2015, 08:40 PM   #14
bigjae1976
Major General
bigjae1976's Avatar
1567
Rep
8,074
Posts

Drives: 11 E90 M3 Individual
Join Date: Mar 2006
Location: Houston, TX

iTrader: (22)

Garage List
2004 BMW M3  [4.50]
2011 BMW E90 M3  [5.25]
2013 BMW 328i  [5.00]
The gearing is also different so that has an effect. But a DCT up shift is a clear advantage over a manual up shift, at least on my E90. The DCT does a consistent power shift and the power feels continuous.

Where I think most people go wrong is they automatically think S6 is the fastest. I think whatever doesn't upset the car and allows you to stay on throttle is the fastest setting.
__________________
2018 F30 320iX Melbourne Red
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red
2000 E36/7 Z3 Steel Blue
Appreciate 0
      01-10-2015, 10:15 AM   #15
CanAutM3
General
CanAutM3's Avatar
Canada
21105
Rep
20,741
Posts

Drives: 2021 911 turbo
Join Date: Jan 2012
Location: Montreal

iTrader: (1)

Garage List
Quote:
Originally Posted by bigjae1976 View Post
The gearing is also different so that has an effect. But a DCT up shift is a clear advantage over a manual up shift, at least on my E90. The DCT does a consistent power shift and the power feels continuous.
Very true about the gearing on the E9X. The thing is, as opposed to the E9X, the 6MT has better gearing than the DCT on the F8X. The DCT is a "hand-me-down" from the F1X ///M, hence not optimized for the S55 IMO.

Quote:
Originally Posted by bigjae1976 View Post
Where I think most people go wrong is they automatically think S6 is the fastest. I think whatever doesn't upset the car and allows you to stay on throttle is the fastest setting.
I personally preferred S6 on the E9X with its crisper upshifts and more immediate downshifts. The beauty of the DCT smarts is that if the ECU sensed any lateral forces, it would execute a butter smooth shift even in S6 which would keep the car perfectly planted. I could not tell if S6 was any faster since there was probably more driver variation than transmission variation .

On the F8X, I also prefer the most aggressive S3 setting for the track for the same reasons as on the E9X .
Appreciate 0
      01-10-2015, 04:19 PM   #16
bigjae1976
Major General
bigjae1976's Avatar
1567
Rep
8,074
Posts

Drives: 11 E90 M3 Individual
Join Date: Mar 2006
Location: Houston, TX

iTrader: (22)

Garage List
2004 BMW M3  [4.50]
2011 BMW E90 M3  [5.25]
2013 BMW 328i  [5.00]
Quote:
Originally Posted by CanAutM3
Quote:
Originally Posted by bigjae1976 View Post
The gearing is also different so that has an effect. But a DCT up shift is a clear advantage over a manual up shift, at least on my E90. The DCT does a consistent power shift and the power feels continuous.
Very true about the gearing on the E9X. The thing is, as opposed to the E9X, the 6MT has better gearing than the DCT on the F8X. The DCT is a "hand-me-down" from the F1X ///M, hence not optimized for the S55 IMO.

Quote:
Originally Posted by bigjae1976 View Post
Where I think most people go wrong is they automatically think S6 is the fastest. I think whatever doesn't upset the car and allows you to stay on throttle is the fastest setting.
I personally preferred S6 on the E9X with its crisper upshifts and more immediate downshifts. The beauty of the DCT smarts is that if the ECU sensed any lateral forces, it would execute a butter smooth shift even in S6 which would keep the car perfectly planted. I could not tell if S6 was any faster since there was probably more driver variation than transmission variation .

On the F8X, I also prefer the most aggressive S3 setting for the track for the same reasons as on the E9X .
I just noticed that the DCT and 6MT have the same rear diff gear ratio?

S6 could break the rear tires loose on an upshift in a turn. This would definitely affect when I could get on the gas. I found that S4 always resulted in a crisp but smooth upshift where I could be full throttle

The downshifts are always smooth as silk.
__________________
2018 F30 320iX Melbourne Red
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red
2000 E36/7 Z3 Steel Blue
Appreciate 0
      01-10-2015, 10:13 PM   #17
CanAutM3
General
CanAutM3's Avatar
Canada
21105
Rep
20,741
Posts

Drives: 2021 911 turbo
Join Date: Jan 2012
Location: Montreal

iTrader: (1)

Garage List
Quote:
Originally Posted by bigjae1976 View Post
I just noticed that the DCT and 6MT have the same rear diff gear ratio?

S6 could break the rear tires loose on an upshift in a turn. This would definitely affect when I could get on the gas. I found that S4 always resulted in a crisp but smooth upshift where I could be full throttle

The downshifts are always smooth as silk.
At my local track, there are 3 spots where I upshift mid corner, never had an issue in S6. In the short video below, you can see me shift twice while in a turn in S6 (at 0:09 and 0:24). Car stays perfectly stable. No power shift, just super smooth clutch engagement.



EDIT: Added link to youtube

https://www.youtube.com/watch?v=p4IdVXetYrc

Last edited by CanAutM3; 01-11-2015 at 10:06 AM..
Appreciate 0
      01-11-2015, 06:13 AM   #18
MaynardZed
Lieutenant Colonel
MaynardZed's Avatar
United_States
1231
Rep
1,789
Posts

Drives: wife crazy
Join Date: Jul 2014
Location: Phoenix

iTrader: (0)

Garage List
Embedded video not working, but I totally believe it. My race mechanic, whose a very fast and accomplished driver, was disappointed with me that I got the 6MT instead of the DCT for my M4. I think his words were "DCT is the only car I've driven on the track that you can full throttle shift while in mid-turn and it won't upset the car."

No matter though, I don't let him drive my cars anymore. Makes me feel real slow watching him. I complained about some problem in my E36 at the track one time, so he takes it out on track and proceeds to pass everyone in advanced HDPE, comes back in and tells me there's nothing wrong with my car.
__________________
Road course laptimes for BMW M4 2015 6MT
WHP East Track: 1:04.880, Arizona Motorsports Park: 1:54.352
Road course laptimes for Porsche 911 991.1 GTS 7MT
WHP East Track: 1:02.770, Arizona Motorsports Park: 1:48.889
Appreciate 0
      01-11-2015, 09:00 AM   #19
bigjae1976
Major General
bigjae1976's Avatar
1567
Rep
8,074
Posts

Drives: 11 E90 M3 Individual
Join Date: Mar 2006
Location: Houston, TX

iTrader: (22)

Garage List
2004 BMW M3  [4.50]
2011 BMW E90 M3  [5.25]
2013 BMW 328i  [5.00]
Quote:
Originally Posted by CanAutM3
Quote:
Originally Posted by bigjae1976 View Post
I just noticed that the DCT and 6MT have the same rear diff gear ratio?

S6 could break the rear tires loose on an upshift in a turn. This would definitely affect when I could get on the gas. I found that S4 always resulted in a crisp but smooth upshift where I could be full throttle

The downshifts are always smooth as silk.
At my local track, there are 3 spots where I upshift mid corner, never had an issue in S6. In the short video below, you can see me shift twice while in a turn in S6 (at 0:09 and 0:24). Car stays perfectly stable. No power shift, just super smooth clutch engagement.

Maybe I need to try it in S6 again. I don't have comp pkg or EDC, not sure if that makes a difference.

Basically it was most obvious in every 2nd gear corner where I'm at full throttle or pretty close. I know the rear suspension is on the bump stops (Dinan springs, OE shocks). So if I upshift in S5 or S6, the back end will kick out. Don't think it will cause the car to lose control but it definitely upsets it.

Im pretty sure S6 would be much smoother if I did the turn in 3rd gear but those are 35-40mph turns.

This leads me to believe it's an issue with my car. I've already had the dealer look at it a year ago and even took them on a 100mph run down an entrance ramp to show her...thought she was going to rip my door handle off! Normal function according to them.
__________________
2018 F30 320iX Melbourne Red
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red
2000 E36/7 Z3 Steel Blue
Appreciate 0
      01-11-2015, 09:43 AM   #20
CanAutM3
General
CanAutM3's Avatar
Canada
21105
Rep
20,741
Posts

Drives: 2021 911 turbo
Join Date: Jan 2012
Location: Montreal

iTrader: (1)

Garage List
Quote:
Originally Posted by MaynardZed View Post
Embedded video not working, but I totally believe it. My race mechanic, whose a very fast and accomplished driver, was disappointed with me that I got the 6MT instead of the DCT for my M4. I think his words were "DCT is the only car I've driven on the track that you can full throttle shift while in mid-turn and it won't upset the car."
I can't seem to get the links working. Maybe something is wrong with the forum website as even old videos in my older threads are no longer working...

Link to YouTube: https://www.youtube.com/watch?v=p4IdVXetYrc

I agree, having the ability to up or downshift mid turn without upsetting the balance of the car is another benefit of DCT that can improve lap times. With my E46 I had to either short shift, ride the limiter or compromise my line in those corners at my home track. With my DCT E92, I could just hammer a perfectly smooth shift .

Quote:
Originally Posted by MaynardZed View Post
No matter though, I don't let him drive my cars anymore. Makes me feel real slow watching him. I complained about some problem in my E36 at the track one time, so he takes it out on track and proceeds to pass everyone in advanced HDPE, comes back in and tells me there's nothing wrong with my car.

Last edited by CanAutM3; 01-11-2015 at 10:07 AM..
Appreciate 0
      01-11-2015, 09:48 AM   #21
CanAutM3
General
CanAutM3's Avatar
Canada
21105
Rep
20,741
Posts

Drives: 2021 911 turbo
Join Date: Jan 2012
Location: Montreal

iTrader: (1)

Garage List
Quote:
Originally Posted by bigjae1976 View Post
Maybe I need to try it in S6 again. I don't have comp pkg or EDC, not sure if that makes a difference.

Basically it was most obvious in every 2nd gear corner where I'm at full throttle or pretty close. I know the rear suspension is on the bump stops (Dinan springs, OE shocks). So if I upshift in S5 or S6, the back end will kick out. Don't think it will cause the car to lose control but it definitely upsets it.

This leads me to believe it's an issue with my car. I've already had the dealer look at it a year ago and even took them on a 100mph run down an entrance ramp to show her...thought she was going to rip my door handle off! Normal function according to them.
My E92 was a civic 2008 with EDC, but I don't think it makes any difference.

Ensure you keep a steady throttle when you shift. If you lift, it will confuse the DCT logic.

Quote:
Originally Posted by bigjae1976 View Post
Im pretty sure S6 would be much smoother if I did the turn in 3rd gear but those are 35-40mph turns.
Just out of curiosity, can you take those 35-40mph turns at full throttle in 3rd. If not, there is no benefit taking them in 2nd...
Appreciate 0
      01-11-2015, 11:22 AM   #22
FTS
Enjoying driving
FTS's Avatar
United_States
388
Rep
1,169
Posts

Drives: 645
Join Date: May 2009
Location: MD

iTrader: (0)

Quote:
Originally Posted by CanAutM3 View Post
The 0.2 I reffer to is the time to speed difference. You are talking about time to distance. Which is not the same thing.
This is the core of the argument or focus to say it differently, you did nail it.

When you look at the difference in upshifting in itself without distance consideration, the gains realized are more substantial. However, when you factor in the 'distance' it is quite a different matter. The reason distance is important is because there is a finite distance to cover in a given lap, so even if you loose the speed advantage in manual shifting you are still covering the distance towards lap completion. When factored in, in the example I gave, the time advantage turns into 0.03 secs, far more less than actual time lost during upshift.

However, there is another factor, one that you also mentioned: the speed advantage is continued and even increased after the shift. Unfortunately, due to distance covered by both scenarios, the braking zone is entered and the speed advantage is erased because the next corner is taken at about the same speed in both scenarios; the one with higher entry speed has to brake a little more
Quote:
Originally Posted by CanAutM3 View Post
Just out of curiosity, can you take those 35-40mph turns at full throttle in 3rd. If not, there is no benefit taking them in 2nd...
I also wondered about this as well. At the tracks we visit, there are half a dozen corners taken between 45-50 mph (only one below 40 mph). So, I tried few different ways in those corners with 3rd vs. 2nd gear, keeping in mind the time it takes me to upshift from 2nd to 3rd. Again, this is in the GT3, so gearing and traction are quite different, but it points to show that we should not make assumptions, test and measure to see what works best.

In 3rd gear full throttle is easy in those corners as long as the surface is smooth and traction can be maintained. In 2nd gear throttle modulation is necessary and acceleration is more violent, but nets an avg. time gain of between 0.6-0.8 secs; however staying in 3rd saves an upshift. Since my upshifts also take about the same amount of time, you would think it is a wash; however, because the matter at the core is time to distance and not time to speed, the net is really close to actual of 0.6-0.8 secs using 2nd gear in the corners I tried.

So, in the example I gave earlier in the thread, which is Summit Point Main T1 through T4 (I did not show the entire set of graphs here), staying in 2nd gear through T1, shifting to 3rd in T2 and staying on it (running red line at 8500 RPM) and taking T3 near WOT after apex and entry to T4, nets a gain of nearly 1.2 secs in my findings and the way I drive; significant gains from 'normal' and assumed way of driving those corners, provided gearing allows it.

Conclusion: Data is King!
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 03:00 AM.




f80post
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST