Drivin' too fast

[mjbst111]

not at all. first off, i'm going to knit-pick and note that "twice as much time" is completely inaccurate and would vary depending upon multiple factors. secondly, i know this isn't the aim of driving quickly, but double-clutching saves your synchros, where as jamming it into gear...well it does just the opposite. granted, yes, that is what the synchros are there for, but trust me, when you get to 200+ thousand miles, you'll be glad yours still work properly. thirdly, after you double clutch, (which takes no time at all) you're immediately at a higher RPM, rather than just waiting for your engine to rev itself gradually. perhaps it's an older car thing, but if i'm going 35 and want second gear, if i were to just put it into second and expect my car to do the work, it would take forever to get up to the proper engine speed. so at least for my car, i say quite the opposite-double clutching takes significantly less time to bring up the RPM. i'd say that between saving your synchros and the immediate jump into higher engine speeds, double clutching is entirely worthwhile.

finally, a wise man speaks!!

 

[Bmw 325i 7803]

Wha...... Double Clutching??? What's that? Auto driver here...

 

[Z3harpmom]

oh yeah baby!!!!

 

[Z3harpmom]

you really miss a sliptronic???????

 

[nadroj]

Double clutching means no power to the wheels for twice as much time. No power=go slower.

its not like anyone would be double cluching when they are race or doing auto X or somthing like that, you would only use it when you are driving normal. it will save the synchros so that when you are racing you can jam it down into 2nd and not get a big grind

 

[mjbst111]

Wha...... Double Clutching??? What's that? Auto driver here...

Double clutching is for down shifting in a manual transmission.

When you shift you put the cluch in, shift ot nuetral, let the clutch out, rev the engine, put the clutch back in, shift to the lower gear, and let the clutch out.

The mechanics behind it is as follows:
When you are driving in a higher gear the gears in the tranny are moving slowly (becasue the engine is al lower revs)... (all the gears move together by the way), anyway when you go to shift to a lower gear, to match the new gear's speed to the wheel's speed you must first speed up the gear. Syncros do this automatically with a clutch like action. However if you don't have syncros you have to double clutch. (this is a boggled explaination i know...) When you put it in neutral and let out the clutch, it speeds up all the gears when you rev the engine, so that when you go to shift, the gears new speed will match the wheel's speed. When you have it in neutral and the clutch is out, the gears are connected to the engine but not the wheels.

hmm i'm not sure if i could even follow what i was saying. I wouldn't be a very good teacher huh? Least i have it all up here

so if you ever saw the fast and the furious 1, after the race the dude says something about granny shifting and not double clutching.... whatever... whoever made that movie had no idea what he was talking about becasue first of all (if you are racing), you don't need to do it, and second, don't usually do it when upshifting... and thats all you usually do when you drag race..... Had to say all that causue i hate when movies say stupid things....

 

[epj3]

We know what double clutching is and what it does -- but the replies to kirby are wrong. E30freak, you say its not any more time, but in racing when LITERALLY .005 seconds can make the difference between winning and loosing, taking the .5 seconds to double clutch could loose an entire position.

 

[mjbst111]

i didn't say you didn't know what it was, i was answering Bmw 325i 7803's question....

epj3, it isn't any more time.... it's not .5 seconds etc.... Double clutching is for when you are down shifting. When you are in a race and are down shifting it is for a bend, NOT becasue you are losing speed going up a hill.... When you are slowing for a bend you aren't hitting the gas anyway, you are hitting the brakes. That is when you double clutch in a race. The "extra shift" does not take any more time off of accelerating becasue you aren't accelerating anyway, just preparing to accelerate... Therefore there is a 0 decrease in time. it matches the revs... if you don't do it then it can actually slow you down or cause a spin out on a bend because the revs aren't matched, etc. Therefore double clutching can only help you win a race!

Now when you do it cause you are slowing down in a high gear up a hill etc, then yes maybe it takes .5 seconds extra to shift, (even then it matches your revs making you better off) but since I'm not going to lose a race to anyone to work its better for me to double clutch to save my syncros.

there was a video on here some time that showed all these different cars getting raced in japan or somewhere. There was a special camera in each car just to show thedriver's feet. They were double clutching around bends.

 

[Bmw 325i 7803]

you really miss a sliptronic???????

Yes, I miss my old one..... The one I have now still slips in cold weather (30's or less) only I am now complimented with a whine-whistle sound when accelerating and letting the speed bleed off (kinda like that taxi lincoln town car or crown victoria tranny sound) and its spread from gears 123 to all 5 now and apparently BMW doesn't care, not to mention it shifts into Park Reverse and Drive roughly...

So yes I do miss my old transmission...at least it didn't make annoying noises and lower/raise my car when changing from drive to reverse or vice versa...

 

[Kirby]

I'm quite familiar with double clutching, thank you. I have driven vehicles that REQUIRE double clutching because they don't have synchros. I've also used a technique known as flat or float shifting, where you DON'T use the clutch at all.

I stand by what I posted (referring to racing, not street driving). There are many circumstances in racing where you need to downshift and keep power applied through a turn, never using the brake. Double clutching takes additional time, time without power to the wheels. You can loose a few thousands of a second per lap. I had a performance driving instructor who lost a national championship by 1/1000 of a second. Can you double clutch in less time than that?

 

[epj3]

I'm quite familiar with double clutching, thank you. I have driven vehicles that REQUIRE double clutching because they don't have synchros. I've also used a technique known as flat or float shifting, where you DON'T use the clutch at all.

I stand by what I posted (referring to racing, not street driving). There are many circumstances in racing where you need to downshift and keep power applied through a turn, never using the brake. Double clutching takes additional time, time without power to the wheels. You can loose a few thousands of a second per lap. I had a performance driving instructor who lost a national championship by 1/1000 of a second. Can you double clutch in less time than that?

Maybe if you had lisa simpson's automatic tapdance shoes

 

[bahnstormer]

I've also used a technique known as flat or float shifting, where you DON'T use the clutch at all.

sometimes referred to as power shifting, u don't even disengage the clutch, u just jam it
into gear. ...at the local bmw cca autoX weekend a guy broke something, but he was forced to drive home w/out using the clutch, made the most awful noises =]

that though, is the fastest way to shift a conventional box

racers have sequential trannies, no double shifting there...

when approaching a bend in a race, u want to be on the brakes as SHORT
a time as possible, u want to get on the gas asap, therefore, u brake very near
the limit of your tires...in order to squeeze every bit of grip out of a tire, u have
to be very gentle, smooth and linear with it...no slamming on the brakes, and no
upsetting the chassis's balance while downshifting...so u heel toe to match revs
while dwnshifting...no one double clutches in a race.