|
|
|
|
|
|
BMW Garage | BMW Meets | Register | Today's Posts | Search |
|
BMW 3-Series (E90 E92) Forum
>
6MT question
|
|
09-30-2011, 05:31 PM | #1 |
Captain
150
Rep 766
Posts |
6MT question
When I accelerate under full throttle and switch gears from 1 to 2 or 2 to 3, I always either jerk hard or skid the tires. What\'s the proper way to shift quickly near redline? When I shift at ~6800, second gear would land around say 6000... but when I shift fast, I release the clutch around 6500, so naturally the car jerks. How do I fix this? Does a modified CDV help? Thanks.
|
10-03-2011, 05:27 PM | #2 |
Freight Dawg
102
Rep 2,103
Posts |
It's all in the timing of the throttle and clutch and yes a CDV delete helps a lot. Really, they only way to get it right is to keep practicing. The goal is to have minimum clutch slip while getting back to full throttle as quickly as possible.
__________________
--Marcelo
'06 Arctic Metallic 325i | Sport Package | 6MT | Dinan Stage III suspension | Dinan exhaust | 330i manifold swap! Click here! | Active Autowerke tune | 135i Brake Calipers | Deiselboost caliper brackets | E46 M3 front rotors |
Appreciate
0
|
10-07-2011, 11:09 AM | #4 | |
Midlife Crises Racing Silent but Deadly Class
1820
Rep 5,337
Posts
Drives: 2006 MZ4C, 2021 Tesla Model 3
Join Date: Oct 2007
Location: Welcome to Jamaica have a nice day
|
Quote:
Let's say you're in 2nd gear at 6,000 RPM. In order to have a smooth shift to 3rd, your engine's RPM needs to be at exactly 3,950 RPM to engage 3rd. The formula is simple: ((next gear's ratio)/(current gear's ratio)) * RPM It's simply timing and practice. You can either time your clutch release at exactly 3,950 RPM for the shift between 2nd and 3rd, or you can release your clutch smoothly to let some slippage smooth out the transition.
__________________
Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
|
|
Appreciate
0
|
10-09-2011, 01:19 AM | #6 |
Banned
127
Rep 6,773
Posts |
+1..CDV and SSK is a very good mod..I had noticeable improvement w the CDV..
|
Appreciate
0
|
10-09-2011, 02:58 AM | #7 | ||
Midlife Crises Racing Silent but Deadly Class
1820
Rep 5,337
Posts
Drives: 2006 MZ4C, 2021 Tesla Model 3
Join Date: Oct 2007
Location: Welcome to Jamaica have a nice day
|
Quote:
Quote:
It takes either practice or patience, and a combination of both.
__________________
Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
|
||
Appreciate
0
|
10-11-2011, 09:01 PM | #8 |
Captain
150
Rep 766
Posts |
thanks, I understand what you're saying. But what I'm asking is ... let's say you're trying to get from 0-60 as fast as possible... disengage clutch at let's say 6800... by the time i have shifted and want to hit the gas again for optimal acceleration, the RPM has only dropped to ~6500... now by your logic I would have to really slowly let go of the clutch for slippage. All this "patience" will slow my acceleration... So how can I even manage to keep up with automatic cars? Or do I just have to jerk/skid for quick shifting?
|
Appreciate
0
|
10-11-2011, 09:14 PM | #9 |
Freight Dawg
102
Rep 2,103
Posts |
Your acceleration will not necessarily slow down. As long as the clutch is even partially engaged and your are at or near full throttle, you'll put power down. Like Hack said, you'll almost like DCT if you do it right. Automated manuals (I should say good automated manuals) will have perfect timing every shift. You're "cushioning" the falling revs so that the energy from the revs being higher than it would in gear goes to the ground more than it goes to wheel spin or the engine mounts.
__________________
--Marcelo
'06 Arctic Metallic 325i | Sport Package | 6MT | Dinan Stage III suspension | Dinan exhaust | 330i manifold swap! Click here! | Active Autowerke tune | 135i Brake Calipers | Deiselboost caliper brackets | E46 M3 front rotors |
Appreciate
0
|
10-12-2011, 11:18 AM | #10 | |
Midlife Crises Racing Silent but Deadly Class
1820
Rep 5,337
Posts
Drives: 2006 MZ4C, 2021 Tesla Model 3
Join Date: Oct 2007
Location: Welcome to Jamaica have a nice day
|
Quote:
And on a manual you can do exactly the same. You can clutch in, change gears and almost immediately slowly release the clutch as you apply throttle. Again, it's all in timing and practice. And when I mean slowly release the clutch, I mean instead of sidestepping the pedal to get it top pop immediately, you smoothly release the pedal in about 1/2 second. When you have the timing down right, you can release the clutch nearly as fast as you can move the shifter from one gear to another, and do it smoothly. Look, I can try and explain this to you and spend the next 5 posts "describing" it to you. My best suggestion to you is, is either keep practicing it until you get it just right, before you blow up your driveline, or have someone who can do this demonstrate it to you so you'll have at least some reference on how to execute it. On a side note, my car came naturally aspirated with solid lifters and individual throttle butterfly for each cylinder, and the second I let off gas at 7,900 RPM it'll drop immediately to ~5,000 RPM in neutral, almost perfect for the next gear. I can stab the clutch in between gearshifts. Can't do that in a turbocharged engine.
__________________
Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
|
|
Appreciate
0
|
10-12-2011, 11:33 AM | #11 |
Freight Dawg
102
Rep 2,103
Posts |
There was a guy on M5 Board who had lots demo videos about shifting that were pretty cool.
__________________
--Marcelo
'06 Arctic Metallic 325i | Sport Package | 6MT | Dinan Stage III suspension | Dinan exhaust | 330i manifold swap! Click here! | Active Autowerke tune | 135i Brake Calipers | Deiselboost caliper brackets | E46 M3 front rotors |
Appreciate
0
|
11-09-2011, 10:31 AM | #14 | |
Freight Dawg
102
Rep 2,103
Posts |
Quote:
Like Hack said, it's really difficult to describe this on a forum. You need to see it in action.
__________________
--Marcelo
'06 Arctic Metallic 325i | Sport Package | 6MT | Dinan Stage III suspension | Dinan exhaust | 330i manifold swap! Click here! | Active Autowerke tune | 135i Brake Calipers | Deiselboost caliper brackets | E46 M3 front rotors |
|
Appreciate
0
|
11-09-2011, 04:38 PM | #15 | |
Captain
150
Rep 766
Posts |
Quote:
|
|
Appreciate
0
|
11-22-2011, 08:00 PM | #16 |
Brigadier General
1534
Rep 4,103
Posts
Drives: BMW M3
Join Date: Feb 2011
Location: Blue Bell, PA
|
With the 335 you just have to be patient between shifts. It's not like an S2000 where you can just slam through the gears. It may seem like an eternity to wait for the revs to fall (especially 1 > 2), but that's just because you're driving - if you were a passenger, it wouldn't seem long at all. I did a driving video a while back and realized this.
__________________
2024 BMW M3 Sedan Frozen Pure Grey II/Fjord Blue, 6MT
Past: 2021 Z4 M40i Frozen Grey II/Black Alcantara | 2017 F30 340i Mineral Gray/Coral Red, 6MT | 2011 E92 335i Le Mans Blue/Black, 6MT |
Appreciate
0
|
12-03-2011, 10:48 PM | #17 | |
Midlife Crises Racing Silent but Deadly Class
1820
Rep 5,337
Posts
Drives: 2006 MZ4C, 2021 Tesla Model 3
Join Date: Oct 2007
Location: Welcome to Jamaica have a nice day
|
Quote:
My final advice to you is, if you want to achieve the FASTEST possible acceleration time? It's not going to be possible to avoid some jerkiness in between shifts when you dump the clutch. Even the last generation SMG, in the most aggressive and fastest shift mode, you will feel a hammer on the back of your @ss every time you shift because, well, there's a difference between engine speed and road speed. ONLY on DCT type transmission where there's two flywheels and two drive-shafts engaged at all times where it is possible to NOT feel that change in gear, because the next gear is already spinning at the same speed as the engine. Or ditch the N54/N55 and go with any of the naturally aspirated M engines. The individual throttle bodies makes the engine rev up and down almost as quickly as your foot can move, and those cars are tuned to produce far more smog than your run of the mill BMW engines so they're not programmed to "hang" up high in rev to keep NOx emission down (as much).
__________________
Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
|
|
Appreciate
0
|
12-04-2011, 12:21 AM | #18 | |
Captain
150
Rep 766
Posts |
Quote:
|
|
Appreciate
0
|
12-04-2011, 06:07 PM | #20 |
Freight Dawg
102
Rep 2,103
Posts |
I'm not sure about turbo cars, but on an NA car, a lightened flywheel will help your engine spin up and down quicker, so less hang and easier full-throttle shifts. For a DD, an excessively light flywheel will be more annoying than helpful. Launching the car will be tough since the car will be much more prone to stall. And since the revs fall quicker making a nice smooth granny shift will be tougher since the revs will go below your target revs for the next gear.
For turbo cars, a very good tune will help more than a flywheel and is cheaper. Good tunes will be able to get rid of most of the rev hang but this may be at a detriment to your cats since it will blow more unburned fuel through the exhaust. That's one of the reasons race cars burble and pop when they slow down.
__________________
--Marcelo
'06 Arctic Metallic 325i | Sport Package | 6MT | Dinan Stage III suspension | Dinan exhaust | 330i manifold swap! Click here! | Active Autowerke tune | 135i Brake Calipers | Deiselboost caliper brackets | E46 M3 front rotors |
Appreciate
0
|
12-04-2011, 09:19 PM | #22 |
Freight Dawg
102
Rep 2,103
Posts |
Depends on the piggy back. My guess is no since most tuners are going for power.
__________________
--Marcelo
'06 Arctic Metallic 325i | Sport Package | 6MT | Dinan Stage III suspension | Dinan exhaust | 330i manifold swap! Click here! | Active Autowerke tune | 135i Brake Calipers | Deiselboost caliper brackets | E46 M3 front rotors |
Appreciate
0
|
Bookmarks |
|
|