Re: Rev matching

[audistuff@juno.com]

The reason the 5k has such a small starter motor is that it is a
permanent magnet motor which is much more durable (and expensive) than
the usual battery energized field coils.



On Wed, 11 Aug 1999 23:36:04 -0700 "Bernard Littau"
<bernardl@acumenassociates.com> writes:
> Hi Russ,
> 
> It would be a good idea to practice rev matching shifting before 
> your clutch
> goes.  It saved me a month ago when the clutch failed on my '71 Ford
> three-on-the-tree pickup.  Had to drive it home with a combination 
> of crank
> the starter in first and start the engine while getting the truck 
> moving,
> and rev matching shifting.
> 
> BTW I haven't had the heart to try starting my Audi while in first 
> -- the
> 5k's have _tiny_ starter motors.  I'll do it if I have to.
> 
> On to rev matching shifting.  I suggest you go down a long, level, 
> uncrowded
> stretch of road and do the following.  In 3rd gear at about 3000 
> rpm, hold
> the car at a constant speed and gently try to push the gearshift out 
> of 3rd
> to neutral.  You should feel some resistance, as the transmission is
> slightly loaded by keeping the car at a constant speed.  Don't force 
> it.
> 
> Now, while holding a constant speed down the road, put some pressure 
> on the
> gearshift to push it from 3rd to neutral, but not enough to actually 
> move
> it.  Gently ease off the throttle, keeping the pressure on the 
> gearshift.
> As you transition from engine powering to engine braking, you go 
> through a
> no pressure on the transmission point, and the gearshift should pop 
> out with
> the slight pressure you are putting on it.
> 
> You might try this a few times.  You are getting a feel for the 
> pressure it
> takes to shift out, and some feel for throttle control around the no 
> load on
> the transmission point.  To unshift, you don't worry about rev 
> matching
> since the engine and transmission are locked at the correct rev 
> match, but
> the load on the transmission is what is important.
> 
> To shift back into 3rd from neutral, you need to match the engine 
> rpms to
> the speed expected by the transmission when they are engaged 
> together.  Get
> moving at the 3000 rpm in 3rd rate, and pop the transmission into 
> neutral
> and let the engine go to idle.  Gently, using the same amount of 
> pressure
> you used to unshift, try and push the gearshift into 3rd.  Of course 
> it
> won't go.  Keep the gentle pressure on the gearshift towards 3rd, 
> and slowly
> raise the engine rpm.  When you get to the correct rpm, the 
> gearshift should
> just pop into 3rd.  You have to move the rpms up at a slow enough 
> rate that
> the system has time to react.  If you gun the throttle, it won't 
> engage even
> though you go past the rev matched point.  Be aware the car is 
> slowing down,
> so it may pop in at 2500 rpm.  Slowly move the rpms, Gently push the
> gearshift.
> 
> That is the brut force lesson.  Note that disengaging is as 
> important as
> engaging.  In fact, you are more likely to damage the teeth on the
> transmission's gears by a bad disengage than by trying to engage.  
> That's
> why we did the gentle disengage first.  Gentle is the key to 
> avoiding
> damage.
> 
> You are not doing your transmission a favor by trying to engage at 
> an
> incorrect speed, so you want to be as close as possible to the 
> "correct" rpm
> before you do your gentle pushing and throttle control.  Modern
> transmissions have synchro-mesh -- think of it as a little clutch 
> that
> engages as you try to go into gear.  The little clutch tries to 
> force the
> transmission's internal gears to spin at the correct rate to match 
> the
> driveshaft.  Synchro-mesh does rev matching for the internal parts 
> of a
> transmission.  The synchro-mesh working is the whine you hear from 
> your
> transmission when you attempt to shift into first at 20mph with the 
> clutch
> in.
> 
> On a level surface with the engine idling, if you gently try and 
> engage
> first without the use of the clutch, you can make the car move 
> forward by
> using the synchro-mesh.  Go ahead and try it once.  You can actually 
> push
> pretty hard on the gearshift and abuse the synchromesh.
> 
> Pay attention to the rpms you are running at in various gears for a 
> while,
> especially when you start from a stop.  I often find myself shifting 
> a 3000
> rpm, and then the next lower gear engages around 2000 rpm.  For a 
> final
> exam, you should be able to take off from a stop in first using the 
> clutch,
> go up to 3000 rpm and shift without clutch from first to second, go 
> up to
> 3000 rpm and shift from second to third, and your passenger should 
> not
> notice if you used the clutch or not.
> 
> Best,
> 
> Bernard Littau
> Woodinville, WA
> '88 5kcstq
> 
> -----Original Message-----
> From: Jeff Mruss <rmruss@pangea.ca>
> To: 'Quattro List' <quattro@audifans.com>
> Date: Wednesday, August 11, 1999 9:00 PM
> Subject: Rev matching
> 
> 
> >I've seen lots of posts referring to rev matching (usually when 
> talking
> about a clutch that died), and I understand the basic concept of 
> matching
> the engine speed to the gear you want to shift into, but what I want 
> to know
> is - how do you do it?  I don't plan on making a habit of it, but it 
> would
> be a pretty useful thing to know if my clutch ever failed.
> >
> >TIA,
> >
> >
> >Jeff Mruss
> 

___________________________________________________________________
Get the Internet just the way you want it.
Free software, free e-mail, and free Internet access for a month!
Try Juno Web: http://dl.www.juno.com/dynoget/tagj.