[QUOTE=raisantos,Nov 30 2007, 02:26 PM] so.. if im cruising in 6th gear at let's say 50mph, then went for a turn, slowed down to 25, is it still better to disengaged the clutch, shift to 5th, 4th, then 3rd, then engage the clutch, than if i shft from 6th straight to 3rd, and rev match?


and it seems like skipping upshifts is a common knowledge that it's bad. i usually do this in stop and go traffic, 1st, 2nd, 4th, then 6th... all this is happening between 2Krpm-3Krpm.

 

When downshifting and double de(clutching) you are using the engine to do the work of the synchros, so as long as you get the transmission turning at the right speed when you blip the throttle, you can go down as many gears as you like.

BTW, you don't necessarily have to heal-toe, because there is no rule that says you have to be on the brakes when you downshift.

The "official" word from Honda is that it is bad for the car if you don't shift through all the gears on the way fron 6th to 2nd, and this is because going straight to second puts all the work of slowing the transmission on the 2nd gear synchro.

I skip gears frequently, but I always do something along with the skipping to make sure that they synchros aren't overworked, but as likely as not when I'm in the situation you describe (50 MPH in sixth, slowing for a 25 MPH corner, normal street driving) I'll do something like ....

1) Long before I even start to slow down I'll clutch in, shift into fifth and blip the throttle for a rev match, so that I continue at a constant speed (50 MPH).

2) Still well before I start to slow down, I'll do it again and get the car into 4th.

3) Then just *before* getting on the brakes I'll do it one more time so that I'm in third.

4) If I feel like kicking up a fuss I might even get into third sooner and drop all the way down to second (at 50 MPH) before I even start slowing down, but doing this encourages me to attack the corner like I was racing, so I only do it when I'm feeling my oats.

5) So anyway, I'm in third before I ever get on the brakes. I'll get off the brakes as I turn in, and then (at 25 MPH in this case) I'll shift into second, and let the clutch out smoothly when I'm ready to start accelerating away from the corner.

NOTE: This is NOT the way you'd be shifting if you were racing or autocrossing, and it's not necessarily the right (or wrong) way to handle this kind of situation; There are an infinite variety of ways to handle this kind of situation.

Let's alter the situation a little. This time we're still doing 50 MPH in 6th gear, and I only realize at the last moment that we've reached a road where we need to turn. I check traffic and the road is clear, so I can nail the brakes hard enough to make the turn, without actually using threshold breaking. I need to get from 6th to 2nd quickly, so I can either heal-toe/double-(de)clutch and go straight to second, or I can work the shifter through the gears quickly while keeping the clutch depressed. I can ALSO just go straight to second, but I was taught not to do that when I learned to drive a stick, and Honda says it's a bad idea, so it's just not something I'd consider doing.

When I work down through the gears this way (with the clutch depressed) I frequently just "nudge" the synchros in each gear. Basically I push gently against the shifter until I feel the locking ring release (so the car starts to go into the gear), and then instead of actually engaging the gear, I move the shifter to the next gear slot and nudge the next set of synchros. Usually engaging each gear with the clutch depressed, or nudging the synchros, is quicker than just jumping from 6th to 2nd, even though it takes more motion on the drivers part. If you have to downshift and skip gears really quickly, the only way is to learn to double (de)clutch and heal/toe.

[QUOTE=raisantos,Nov 30 2007, 02:26 PM]and it seems like skipping upshifts is a common knowledge that it's bad. i usually do this in stop and go traffic, 1st, 2nd, 4th, then 6th... all this is happening between 2Krpm-3Krpm.

 

If you double-clutch the shift to spin the input shaft of the transmission up to speed before engaging a lower gear, it will cause very little wear on the synchronizers, and all is fine and dandy.

If you simply clutch in and select 3rd from 5th for instance, it's quite a lot of wear, and I would suggest against it.

 

i thought double clutching is unnecessary for trannies nowadays?

 

The purpose of synchros and double-clutching is the same... to match the speed ratio of the layshaft and the drive shaft within the transmission to a particular gear ratio.

When the ratio of speeds between the two shafts is close to that of the gear being selected (i.e., one gear upshift or one gear downshift) then the synchros can easily handle the stress of matching the speeds.

However, if the ratio of speeds between the two shafts is quite a bit different than the gear being selected (i.e., skip shifting), then the synchros alone take on a much greater burden when matching the speeds, and thus more wear and tear.

Properly performing a double-clutch rev match will do the same job, thus reducing/eliminating the work that the synchros need to perform to match the speed ratio.

So while a modern transmission with synchros does not need to be double-clutched, care needs to be taken to prolong the life of the synchros either by double-clutching during skip shifts or by avoiding skip shifts.

 

wow people, its not a sequential transmission! Keep the revs in an acceptable position for each shift and do what you want. Don't be a retard and you will be fine.

 

As 00CivicSI said (in a round about way), double clutching isn't necessary today, becasue modern transmisisons have synchros to do the work for us.

However, accourding to Honda, skipping gears in the S2000 will damage the transmission, and what that *really* means is that if you want to skip gears you have to make sure that you're not asking the synchros to do more than they were designed to do. Double (de)clutching and a variety of shift timing techniques make it possible to skip gears, so those who want to skip gears either have to learn the techniques or risk premature transmission problems.

IMO it is dead wrong to see any of this as being indiciative of design shortcomings. The transmission is designed to shift quickly, and the light flywheel lets the driver double (de)clutch and rev match when he wants to skip gears. It seems to me that Honda intended for the car to be driven this way, because it works perfectly and has no problems when driven that way. Building it to withstand hamfisted skipshifting and other "bad habits" would have taken away may of the qualities we all love in the S2000's shift action.

So, no, you do not need to double clutch or do anything else special with the S2000, but Honda has stated that skippinig gears will lead to early transmission failure, so you should consider that before skipping gears in your own S2000. If you think you know what you're doing and can do the work of the synchros in other ways, then you're the best judge of that, but if in doubt, then I personally think you'd be better off to follow Honda's advice. They advise against skipping gears, not that you should double (de)clutch when downshifting.

 

Which is more retarded? Ignoring Honda's advice, or not understanding the inner workings of a transmission?

IMO, not understanding some of the design tradeoffs in the S2000's design is not, in and of itself, an indication that one is retarded.