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Discussion Starter · #1 ·
Driving my new 325 cic sport is a little different than the old 4 banger Saab... I'm still getting used to it ...

Anyway when I push the RPMs to 5k+ in 1st and shift to second, I have a tough time getting off the clutch without a slight buck. Do I need to shift faster? More/less gas? Too fast off the clutch? Too slow off the clutch?

Like I said, driving at these RPMs is new to me, and any help would be greatly appreciated.
 

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Casey!
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NEWBIMMERGUY said:
Driving my new 325 cic sport is a little different than the old 4 banger Saab... I'm still getting used to it ...

Anyway when I push the RPMs to 5k+ in 1st and shift to second, I have a tough time getting off the clutch without a slight buck. Do I need to shift faster? More/less gas? Too fast off the clutch? Too slow off the clutch?

Like I said, driving at these RPMs is new to me, and any help would be greatly appreciated.
Someone needs a CDV-ectomy...

See http://www.zeckhausen.com/CDV.htm
 

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Try to go a little slower at first. BMW clutchs engage farther out if that helps. So you can jerk your foot off the clutch an inch or so then eaze off the clutch and add gas. It takes practice.
 

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Discussion Starter · #4 ·
Ok, I need to learn more about this CDV biznus. I just spent an hour reading posts about it. All of a sudden I want to scream about this thing! I knew I wasn't a total driving moron (maybe a partial moron). BTW- I race boats, so I have an innate desire to smoke everyone on the road, and have never had the ability to to it...

Besides the sticky thread, where should I look?
 

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Don't be too fast to blame the CDV. I've had my 330i for about 3 months, and now that it's fully broken in (yeah 2000 miles in 3mos), I notice that when I rev higher in first, I can let the clutch out generally faster than shifting at lower speeds. I think, for me, it's more a matter of the revs holding more at higher shift points.
 

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Wait a bit longer for the revs to wind down, then come up on the clutch and catch the right RPM.

I'm sorry to say that a CDV is also to blame, until you learn to compensate for it. A lighter flywheel would help, but that's mucho dinero.
 

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NEWBIMMERGUY said:
Ok, I need to learn more about this CDV biznus. I just spent an hour reading posts about it. All of a sudden I want to scream about this thing! I knew I wasn't a total driving moron (maybe a partial moron). BTW- I race boats, so I have an innate desire to smoke everyone on the road, and have never had the ability to to it...

Besides the sticky thread, where should I look?
I think a lot of it's in the gearing. 1st and 2nd really aren't in quite the right place, IMHO. I would just shift a little lower for 2nd and give the drivetrain a break... :dunno:
 

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shizat63 said:
Wait a bit longer for the revs to wind down, then come up on the clutch and catch the right RPM.

I'm sorry to say that a CDV is also to blame, until you learn to compensate for it. A lighter flywheel would help, but that's mucho dinero.
This is true. Also the drop in gearing between 1st & 2nd is the largest. It's all about timing the shift properly with the corresponding rpms when you engage 2nd. For example, if you shift out of 1st at 5K rpms, do you know what speed you're going and also do you know what rpms that speed will equal when you engage 2nd? Find the answer to that question and you will find the answer to your smooth shift. My guess is that you are engaging the clutch too soon and too hard. Don't try to be fast for now just work on getting the timing correct, after that then work on making the shift faster. In the beginning watch & use the tach, it will help and then when you get used to it you won't need to watch it that much anymore. I've driven my car with & without the CDV and I can get smooth shifts either way, so I would suggest to understand the theory of shifting and learn to apply it and then when you get that down consider removing the CDV if you feel it's neccessary.
 

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NEWBIMMERGUY said:
Driving my new 325 cic sport is a little different than the old 4 banger Saab... I'm still getting used to it ...

Anyway when I push the RPMs to 5k+ in 1st and shift to second, I have a tough time getting off the clutch without a slight buck. Do I need to shift faster? More/less gas? Too fast off the clutch? Too slow off the clutch?

Like I said, driving at these RPMs is new to me, and any help would be greatly appreciated.
For smooth shifts a good match of RPMs is required.

You need to let the engine rpms fall between gears. Otherwise the engine rpms are too high for the next gear and the car bucks.

Wait longer before releasing the clutch when shifting to 2nd. Each succeeding shift requires less and less delay.

Here' my guestimate on how long to hold down the clutch pedal on shifts....

1 to 2: 1 second
2 to 3: .8 seconds
3 to 4: .4 seconds
4 to 5: as quick as is comfortable without rushing.

There's another way to avoid the back-and-forth buck, LOT'S of throttle.
If you want to shift more quickly, just give it gas and you'll feel only one direction change (forward) instead of a buck (forward and back). Note: if you wait TOO long to shift, and your engine RPMs are too low, you'll feel the buck in the opposite direction. (back and forward).

The reason the delay is longer for the lower gears is that the difference in gear ratios is larger. If I understand correctly, the reason the engine takes THAT long to lose RPM is that the flywheel is heavy and therefore carries a lot of angular momentum.

I'm not sure what the disadvantage is of a lighter flywheel.
 

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Will_325i said:
Here' my guestimate on how long to hold down the clutch pedal on shifts....

1 to 2: 1 second
2 to 3: .8 seconds
3 to 4: .4 seconds
4 to 5: as quick as is comfortable without rushing.
Wow, you're even more consistent then SMG. :p
 

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Rev-matching is the key to smooth shifts. If you are really brave, you don't even need to use the clutch to shift. It's really tricky, but if you hold the correct RPMs the transmission will slide out of the current gear almost effortlessly. Then you have to adjust the RPMs to the correct speed for the next gear and the shift lever will slide right in. If you are off a few RPMs you will grind a little, but if you are right on the money it will slip into gear so smoothly that you won't even feel it.

Now granted, I don't recommend everyone run out and try this in their brand new bimmer, I'm just saying that it can be done. (It's also a little tougher with a brand new transmission, the clearances are still really tight.) This method is also not usually the fastest, if you don't want to abuse the mechanical bits. (It can be very fast if you don't mind forcing the lever, and hearing a little grinding on each shift. Several old school racers use this method, but they rebuild their engine and transmission on a regular basis.)

The real trick to smooth shifting is knowing what RPM the engine needs to be at for each gear at a given road speed, and I do recommend that you use the clutch. Once you know that, it's just a matter of practice. Like others have said, the spacing between 1st and 2nd is the largest. I belive BMW did this to make sure every bit of the RPM range is used to get their cars from 0 - 60 mph, with only 1 gear change. (0-60 isn't really measured very often in real life, but that is one of the numbers that everyone uses to compare other cars when shopping, or in the magazines....)
 

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NEWBIMMERGUY said:
Driving my new 325 cic sport is a little different than the old 4 banger Saab... I'm still getting used to it ...

Anyway when I push the RPMs to 5k+ in 1st and shift to second, I have a tough time getting off the clutch without a slight buck. Do I need to shift faster? More/less gas? Too fast off the clutch? Too slow off the clutch?

Like I said, driving at these RPMs is new to me, and any help would be greatly appreciated.
A homemade clutch-stop was all I needed to smooth out my shifts. It is by far the best bang for your buck mod. Do a search for the DIY. If you can't find anything, I'll tell you how I did mine.

It cost about $2.
 
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