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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Tracking, Autocrossing, Dragstrip, Driving Techniques > Missed shifts - 6MT



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      05-11-2007, 03:13 PM   #23
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Quote:
Originally Posted by leftcoastman View Post
Close. The slip is at home. 14.6 @103.5

I'm going back next week. Twas my first time at a drag strip. I'm thinking mid 13s with a proper launch. Hell I'd be super stoked to get 13.9x that here at 6,000 feet. Might even try starting in 2nd since the track is a bit slick.

BTW - I have found that finger-shifting (gentle) is less likely to cause a missed shift than palm-shifting (forceful).

To be honest, the challenge of properly launching a 6MT is appealing to me. No grandma-appropriate 6ATs here! Just kidding, fellas.
I ran a 14.215 @ 98.609 with a 2.29 60 foot at a track with 3000ft elevation (car only had 400 miles on it)....how slow are you shifting?? My best MPH was 101, but my launch sucked. Also the track i was at has almost no track prep at all its like runing on ice. I loose traction going into 3rd. Im just going to keep practicing, I have to break 13s at that track. Im going to go back once i have about 5000 miles. Im at 1700 right now.


I didnt even launch for this run, I just let the clutch grab and I gunned it.

I also have trouble getting into 2nd. I dont realy miss it but it grindes alittle right before it goes in, once in sometimes it feels like its not pushing at all. I drop the clutch and floor it and the car seems to not want to go while in 2nd. Its weird because in my Evo 2nd gear was insane and realy easy to get into with no grinding at all. Im just going to keep practicing
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      05-11-2007, 03:34 PM   #24
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Quote:
Originally Posted by AW335TT View Post
I ran a 14.215 @ 98.609 with a 2.29 60 foot at a track with 3000ft elevation (car only had 400 miles on it)....how slow are you shifting?? My best MPH was 101, but my launch sucked. Also the track i was at has almost no track prep at all its like runing on ice. I loose traction going into 3rd. Im just going to keep practicing, I have to break 13s at that track. Im going to go back once i have about 5000 miles. Im at 1700 right now.


I didnt even launch for this run, I just let the clutch grab and I gunned it.

I also have trouble getting into 2nd. I dont realy miss it but it grindes alittle right before it goes in, once in sometimes it feels like its not pushing at all. I drop the clutch and floor it and the car seems to not want to go while in 2nd. Its weird because in my Evo 2nd gear was insane and realy easy to get into with no grinding at all. Im just going to keep practicing
As I said in my first post, the missed shifts are making me shift slower than I should be.

I never really wanted to get seriously into the dragstrip. Just really wanted to see what a 335i does at over a mile high. My heart is still with road courses and canyons.

mmmmm...twiiissstieees..
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      05-11-2007, 03:54 PM   #25
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Quote:
Originally Posted by leftcoastman View Post
As I said in my first post, the missed shifts are making me shift slower than I should be.

I never really wanted to get seriously into the dragstrip. Just really wanted to see what a 335i does at over a mile high. My heart is still with road courses and canyons.

mmmmm...twiiissstieees..
I know what you mean. I LOVE canyons. In 2 days it'll be a month since i got my car and I will have close to 1800 miles. Guess where I've been. Im in the canyons atleast once a day.
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      05-11-2007, 06:23 PM   #26
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I've been terrible on my 1-2 shifts - many ugly grinding misses - but have never missed any 2-3 or 3-4 shifts. Usually it's the 2-3 that gets me. Not in this car. Sometimes I'll nail 2nd and get some grinding which tells me I just barely made it!

It has gotten somewhat better since the short shift knob install but I still have no confidence when I attempt a WOT 6000 rpm quick shift. Forget powershifting 1-2. On the other hand, I nail the 2-3 with a hard chirp every time.

Now on the 1-2 I just shift a little tiny bit slower and I never miss. I still get that hard chirp or a little wheel hop, I don't fall off boost and no more fear of revving it to 10K! I ordered the Zeck CDV so we'll see if that helps.
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      05-11-2007, 06:29 PM   #27
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Quote:
Originally Posted by razormy View Post
It's the clutch delay valve. It does not matter how fast you will try to shift, the CDV will only allow the fluid to move through it at it's rate.

Once you remove it, you will love your 6MT.
problem with a manual? IT THE CDV

problem with your engine? IT NO OIL COOLER



the cdv has nothing to do with the gearbox, which is what hes complaining about
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      05-11-2007, 08:41 PM   #28
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Interesting - I occasionally have the same thing happen when I go from 2 to 3 quickly. Different car, but same as you describe. It hasn't happened for me from 1 to 2. I haven't removed the CDV.
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      05-11-2007, 11:28 PM   #29
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I find this all interesting, it seem like everyone has experience this, and I bet no one wanted to say anything since they thought they would be flamed for not knowing how to shift right...

As someone said, you just need to jam on the shifter hard... I do not believe that has to be.

Hell I have 53 Ford Pick up with Hypo 289 putting out 350 HP with 66 Ford Top Loader with Hurst shift and it shifts smooth as silk. Trust me those old trannies were rough and I do not have to jam on it.
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      05-13-2007, 01:22 PM   #30
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almost everytime im trying to shift fast from 1-2 It will grind. If I leave the clutch out a second longer, then the rpms drop really slow, must be the valve at work. Last time I tried to use a little more force, and pulled my knob right off!
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      05-13-2007, 05:55 PM   #31
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The exact same thing keeps happening to me. At the drag strip I've lost twice because when I shift from first to second it grinds really hard. I only have this problem shifting from 1st to 2nd as well.
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      05-13-2007, 06:14 PM   #32
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Quote:
Originally Posted by Park2670 View Post
almost everytime im trying to shift fast from 1-2 It will grind. If I leave the clutch out a second longer, then the rpms drop really slow, must be the valve at work. Last time I tried to use a little more force, and pulled my knob right off!
like i just said it has nothing to to with the CDV, it has to do with the synchros, this is apparent because 1: the issue is between 1->2 2: the issue occurs when you try to shift the fastest 3: the issue is grinding, all of this = slow synchros

again the gearbox has nothing to do with the CDV just the clutch and its engagment.

a gearbox is conceptually two seperate spinning parts, one attached to the wheels and the other independant or attached to the engine (depending if the clutch is in or out)

when you go from 1st gear at say 6500 most of the gearbox mass which was connected directly to the clutch is spinning at a speed related to 6500 RPM, but for sake of argument lets pretend it spins at engine speed with no static gear reduction, the part attached to the wheels is spinning a little slower in relation to 1st gears gear ratio (but they are still connected directly)

to get the car into second the big mass of gears needs to slow down by a factor related to the change in gears between 1st and second, in our case about 40%. it needs to do this because the next gear is smaller and has a faster output turn then 1st gear, so in order to match the speeds up it need to rotate slower (and in conjunction the engine, but they are not connected while you have the clutch in)

so when you yank the shifter out of first and try to slam it into second something called a synchro is used, this basically slows the mass of gears down through friction to the same speed as the driveshaft

problem is depending on the synchro they can only slow the gears down so fast, and you yanking on the stick to push it into second is much faster than the synchro can handle. because of this the gearbox is still spinning faster than the driveshaft and you hear CRRIIICHHHH


note that this whole time the gearbox is detached from the engine and the clutch (well half of it) the only time the CDV comes into play is when you let your foot off the clutch, it slows the speed at which the clutch connects, this has nothing to do with the grinding you hear or difficulty engaging second


your car is not defective, you do not suck at shifting (atleast not because of this ), its a BMW engineering design issue.

there is not solution short of shifting sooner, slower, or ignoring the grinding (not the best of ideas)

i hope you have enjoyed this public service announcment.
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      05-13-2007, 09:35 PM   #33
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You can solve it by double clutching...
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      05-13-2007, 09:51 PM   #34
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no, no you cant
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      05-13-2007, 10:30 PM   #35
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Yes you can. The problem is that parts of the transmission are too far out of sync for the synchros to overcome. So if you double clutch and get those parts rev-matched, you don't grind the gears.

As always, driver error...
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      05-13-2007, 10:45 PM   #36
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Quote:
Originally Posted by choatie88 View Post
Yes you can. The problem is that parts of the transmission are too far out of sync for the synchros to overcome. So if you double clutch and get those parts rev-matched, you don't grind the gears.

As always, driver error...
you either dont have your car, or you dont actually know what double clutching is , there is no way double clutching will alow you to shift faster from 1st to second.

if you just shift slower, not even half a second slower, you dont get the grinding issues. show me anyone in this world who is able to double clutch in that time frame , not to mention that they would have to wait longer than half a second for the engine RPMs (what drives double clutching) to drop enough to be usefull

double clutching is not a performance driving technique no matter what you heard from fast and the furious

so again; no, no you cant
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      05-13-2007, 11:16 PM   #37
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I never said you could shift faster by double clutching, I said you could eliminate the grinding by double clutching. The problem is that these drivers aren't giving the synchros enough time to do their thing, so, in theory, they could fix the issue by double clutching.

Whether they're good enough to double clutch faster than the synchros can do their job is another question entirely.
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      05-13-2007, 11:30 PM   #38
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Quote:
Originally Posted by choatie88 View Post
I never said you could shift faster by double clutching, I said you could eliminate the grinding by double clutching. The problem is that these drivers aren't giving the synchros enough time to do their thing, so, in theory, they could fix the issue by double clutching.

Whether they're good enough to double clutch faster than the synchros can do their job is another question entirely.
right you said that was a solution, but its not, the problem is having grinding when trying to shift ASAP, so a solution would involve removing the grinding and still shifting ASAP... soo why would someone go through all the trouble of double clutching when they could just shift a tad bit slower and in the end faster than double clutching?

in otherwords, how is that a solution or even a good idea at all?
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      05-14-2007, 01:02 AM   #39
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Grinding is a different issue. I get no grinding. I just can't get into second reliably when launching.
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      05-14-2007, 10:14 AM   #40
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Quote:
Originally Posted by leftcoastman View Post
Grinding is a different issue. I get no grinding. I just can't get into second reliably when launching.
This is true, the grinding occurs when you got it part way in and you let out the clutch.

I spend more time with this and noticed a few things;

The shift into second has two noticeable "click" (lack of a better word). When you pull the shifter back it stops moving or clicks in, and it feels like your in gear, however, if you pull a little harder (depending on engine speed) if will mover a little more until you get the next click.

Getting to the second click is the issue, if the Engine RPMs are too high you have to pull really hard to get past the first click, sometime it just sticks there and you have to wait a second of two or clutch it again like choatie88 pointed out.

I come up with a little work around, and it is a bit of pain but better than a full double clutch. I just release the clutch half way and push down again and back out. This lets the clutch engage a little and seems to allow the shift to easily move into the second click spot.

I agree this is still not right, but now thinks this could be a BMW design thing like the CDV to keep poor manual drives from killing the transmission.
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      05-15-2007, 07:49 PM   #41
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Keep the gas floored and powershift =)

Don't let off the gas hit the clutch shift to 2nd try that, thats fun for the higer gears the cdv gives it the perfect amount of delay to not engage hard
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      05-16-2007, 12:17 AM   #42
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does powershifting fuck anything up ?
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      05-16-2007, 02:25 AM   #43
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I hear BMW is coming out with their own version of a shift-kit. I would wait for that.
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      05-16-2007, 10:41 AM   #44
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Powershifting

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Originally Posted by Sparta3223 View Post
does powershifting fuck anything up ?
Not recommended. Do it often enough and be prepared to repair or change your manual transmission.
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