what exactly is double cluthing?
05-19-2003, 09:56 AM
#16
Burning Brakes
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when you double clutch you are matching the speed of the input shaft, which is coupled to the crank when the clutch is out, to the speed of the output shaft. While it may help save a little wear on the synchs, it is not necessary in a modern trans, heel and toe downshifting and braking, on the other hand, raises engine speed as you downshift so as not to upset the chassis as you engage a lower gear.
05-19-2003, 12:19 PM
#17
Racer
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by MHT:
<strong>when you double clutch you are matching the speed of the input shaft, which is coupled to the crank when the clutch is out, to the speed of the output shaft. While it may help save a little wear on the synchs, it is not necessary in a modern trans, heel and toe downshifting and braking, on the other hand, raises engine speed as you downshift so as not to upset the chassis as you engage a lower gear.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I'm sorry, but you are wrong. Double clutching, as Geo explained already, is matching input shaft speed to crankshaft speed. Double-clutching when upshifting will slow the input shaft down because you double-clutch without blipping the throttle meaning that the engine is roughly at idle. Unless you meant that the idea is to match engine RPM (and hence input shaft RPM) to the proper inpur shaft RPM for the gear which will be selected. Unless the gear is 1:1, then you're not actually matching the input shaft speed to the output shaft speed.
As for double clutching slowing one down, it definitely does. However, it does not seem that way since you are busy with the act of double-clutching. Since double-clutching gives you something to do whereas waiting for the synchros does not, it only seems that it is faster to double-clutch.
Aaron
<strong>when you double clutch you are matching the speed of the input shaft, which is coupled to the crank when the clutch is out, to the speed of the output shaft. While it may help save a little wear on the synchs, it is not necessary in a modern trans, heel and toe downshifting and braking, on the other hand, raises engine speed as you downshift so as not to upset the chassis as you engage a lower gear.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I'm sorry, but you are wrong. Double clutching, as Geo explained already, is matching input shaft speed to crankshaft speed. Double-clutching when upshifting will slow the input shaft down because you double-clutch without blipping the throttle meaning that the engine is roughly at idle. Unless you meant that the idea is to match engine RPM (and hence input shaft RPM) to the proper inpur shaft RPM for the gear which will be selected. Unless the gear is 1:1, then you're not actually matching the input shaft speed to the output shaft speed.
As for double clutching slowing one down, it definitely does. However, it does not seem that way since you are busy with the act of double-clutching. Since double-clutching gives you something to do whereas waiting for the synchros does not, it only seems that it is faster to double-clutch.
Aaron
05-19-2003, 06:10 PM
#18
Burning Brakes
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Aaron, when you take your foot off the clutch pedal the input shaft and the crank shaft are coupled together, they are rotating at the same speed, this is true regardless of the gear selected. What I meant was, as you downshift, the relationship between input shaft speed and output shaft speed changes, therefore at a given road speed you need to increase the input shaft speed as you shift down. I was not trying to imply a 1 to 1 relationship. I can see no reason to double clutch during an upshift, in fact many drag racers do not even lift off the gas while shifting, for normal driving, the rpm drop as you lift and declutch to shift is enough to allow smooth shifting.(As for double clutching slowing one down, it definitely does.) It does what?
Mark
Mark
