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BMW 3-Series (E90 E92) Forum
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Heel-toe?
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01-20-2010, 08:55 PM | #23 | |
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When you single-clutch downshift, you only spin up the engine speed; the new gear is still spinning at too low of a speed. This is where the syncromesh comes in: it pushes up against the side of the new gear, spinning it up to speed. Although this is what the syncromesh was designed to do, this is also how it is worn down. When you double-clutch downshift, you spin up the gear assembly to match the speed of the syncromesh so that it essentially is not used. Here, this picture may help. The output shaft is only connected to a gear when the syncromesh ('dog gear' as they call it in the picture, but for our purposes think of them as the same thing) is pushed onto the side of a gear by the selector fork (which is what you move with your right hand when you shift). Otherwise, the whole gear assembly spins freely (i.e., when you are in neutral with the clutch disengaged). The dog/syncro gear is connected to the output shaft; gears 1/2/3/4/5 are not: When you single-clutch downshift, you do not spin the gear assembly up to the correct speed to match with the syncro/dog gear. Now, my personal philosophy on downshifting with H-patter syncromesh 'boxes: I only double-clutch when I am skipping gears (i.e., going quickly from 5th to 3rd). In this case, the difference between gear speeds is great enough that the syncros actually get used pretty hard and require quite a bit of effort to pop onto the side of the gear. To me it is easier to double-clutch than to wait for the gear to engage; the new gear engages quite easily with a double-clutch. However, if I'm only going down one gear (like 4th to 3rd) I single-clutch because the difference in gear speed is pretty small and the syncros only have to work a little bit; and the gear usually pops right in with little effort. |
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01-21-2010, 12:30 AM | #24 | |
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so i suppose that, while rev-matching alone (single-clutch rev-matching) minimizes wear on the clutch and flywheel, it doesn't minimize wear on the synchros b/c it doesn't spin up the gear assembly, only the ouput shaft and synchros. so the synchro still gets worn when the selector slots into place and the synchro makes contact with the gear. but i still don't quite understand how double-clutching makes a 5th -> 3rd or 4th -> 2nd downshift easier and quicker. i understand that double-clutching spins up the gear assembly to the same rpm of the output shaft (thus allowing minimal wear on the synchros), but i'm having trouble visualizing how double-clutching spins up the gears. could you elaborate on that a bit? TIA, Eric
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01-21-2010, 10:54 AM | #25 | |
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01-21-2010, 10:58 AM | #26 | ||
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I noticed the Double clutch was always a cleaner rev match, i normally double as J-Tyler said from a large gear change as he mentioned... 5th to 3rd or even 2nd just depending on how the situation pans out. Now I know why its so much cleaner, thanks to everything being matched up. |
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01-21-2010, 02:36 PM | #27 | |
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So, when you double-clutch, you engage the clutch during the throttle blip. Engaging the clutch (connecting it to the engine) means that when you blip the throttle, you spin up the engine speed and the gear assembly; with a single-clutch downshift (clutch disengaged during the throttle blip) you only spin up the engine speed, not the gear assembly, because the assembly isn't connected to the engine via the clutch. I hope that makes sense, I don't feel like I worded it very well...lol. Double-clutching is very awkward at first, but once your brain & muscles get trained to doing it, it becomes second nature just like a single-clutch. In the 335i video in my sig, I'm double-clutching from 5th to 3rd at the end of the front straight and at the end of the back straight. It happens faster than two single-clutch shifts (5th > 4th, 4th > 3rd) and I know for sure the gear will pop right in. |
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01-21-2010, 02:55 PM | #28 | |
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01-21-2010, 04:16 PM | #29 | |
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02-20-2010, 06:39 AM | #30 |
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One of the great pleasures driving a manual tranny. This my first ownership of a german car and compared to all my previous cars, this by far the most natural pedal placement (and having the accelerator pivoting from the floor) I have Owned. Porsche is the best I have experienced.
On my other cars, sometimes I felt like I was spraining my right ankle. Here is old pic I posted years ago: The thread is HERE. Danny
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04-01-2021, 08:34 PM | #31 |
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I've had my e92 for 8 years now, and I've struggled to consistently heel-toe the entire time. I can get it sometimes, but other times my foot slips off the accelerator. And I'm not really comfortable uncovering more of the brake pedal.
I had my first track day recently, and my downshifting was total garbage. In an effort to remedy this before my next time out, I finally went and bought some Bimmerworld aluminum pedals with an extended accelerator along with some Piloti Pistone X driving shoes. I went for my first test drive tonight...very happy! I didn't miss a single downshift. Just having that extra half inch of pedal and purpose-made shoes did the trick! Can't wait to be properly downshifting next time I'm on track.
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2013 E92 328i M-Sport: BSM, 6MT, 3IM+AA Tune, BMW PE, M3 control arms, Bilstein B12 Pro-Kit, BMW SSK, CDV Delete, Apex EC-7 18x9" |
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