Subaru Forester Review

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hello everyone and welcome. this videowe’re going to be talking about what is double clutching when referring to thedriving technique. so we’re going to talk about what theprocess of it is and then talk about why it’s necessary and its really onlynecessary with cars which don’t have synchronizers with a manualtransmission and so i think the why question is the part that kind ofconfuses people the most, that’s the most difficult to understand, but first let’sgo ahead and walk through the process of what you’re actually doing. so here wehave our accelerator pedal, our brake pedal, and our clutch pedal.

the first thing you’re going to do islet your foot off of the accelerator pedal, the second thing you’re going to do ispress in the clutch, third thing you’re going to do we’re going in our scenariobe going from fourth year to third gear so we’re going to pull it out of fourthand put it into neutral. the fourth thing we’re then going to dois release the clutch and the important thing to realize here is that this isn’tyou know this like tedious step-by-step process a lot of this is kind ofhappening simultaneously there’s overlap between these steps so it’s actually avery smooth and quick process it’s not like you know first step let offaccelerator seconds that press in clutch

like those are kind of happeningsimultaneously there’s overlap between these steps so it’s a very quick smooth process.moving on to number five because we’re down shifting we need to raise up theengine speed to match the gear speed so we’re going to blip the throttlethat’s for number five. if you were up shifting going from 3 to 4 then youwould leave your foot off the gas and let that engine speed dropped down toyour gear speed because will be rotating lower so you wouldn’t put the throttlein that case but we’re going from fourth to third so we blip the throttle,

then we press in our clutch, and then weput it into our third gear and then we release the clutch and then you go onabout your way driving it in third gear. so that’s the process of doubleclutching and as i mentioned it smooth there’s overlap between these steps andit’s a very quick process but why is it necessary and so that’s the part here that’s allabout these synchronizers and you know how they’re involved in this process. so in order to understand why we need tolook at, you know, the inside of a transmission so here we’ve got ourengine which is coupled to the flywheel

it’s got a pressure plate around theclutch so there’s your clutch disc and then that clutch disc is going to gearup to a layshaft which will rotate your gearsthree and four here is your output shaft with a collaron it and then here is your gear selector so you can see if it’s aboutthis point and you pull that fourth back it’s going to push this forward pushingthis forward and pushing that collar into fourth gear so if we’re going to be going into thethird year we push it forward and that would slide it into there. so theimportant thing to realize looking at

this diagram is that each individualcolor can rotate at its own speed so in red red will always rotatetogether so the engine flywheel the pressure plate those are always rotatingtogether in blue some of these gears can rotate on theirown because these are on bearings on the output shaft but they will always berotating with the layshaft so their speed may differ but they’ll alwaysrotate with the layshaft and so everything in blue is always rotatingtogether and then everything in green so your collar which is splined to theoutput shaft will always be rotating with the output shaft

so in different scenarios everything canbe rotating together that’s all synchronized for example when you’re ingear or everything can rotate separate so if you’re in neutral and you haveyour clutch pressed in everything is rotating at its own speed ok so let’s walk through this processagain but looking at what’s going on inside so first we’re releasing the acceleratorpedal second were pressing in our clutch so now this and this are no longerrotating at the same speed and so that means also at that time when we pressedin that clutch

the collar is also rotating at adifferent speed from the gear so everything is rotating at a differentspeed at that time once you have your clutch pressed in so you release the clutch and now whatyou’ve done is you’ve linked up the engine to everything in blue soeverything in blue and red is now rotating together and so what your goalwith doing that is you can press the throttle so that when you go into gear 3 you nowhave influence over gear three’s speed because it’s connected to the engine

so you blip the throttle you bring thisup to speed with the collar and then once these two speeds are close you press inthat clutch and the reason you’re doing that is because you don’t want all ofthe mass of the engine influencing that gearshift and so once you press in the clutch these two are relatively the same speedyou press them in together you don’t have that influence from theengine so it’s you know it’s not much mass that you have to actually bring tothe same speed so you connect those together and thenyou’ve already you know this is a very

quick process and so then you let outthe clutch once you have that in gear and that’sgoing to be a very smooth process for shifting the gear so the reason why you do it is becauseyou you let out the clutch and that givesyou control over the gear speed versus the synchronizer speed and you want tomatch those press in your clutch engage them release your clutch and then haveeverything moving together so if you have a regular transmissionwhich most of you out there you know

driving a regular production car onpublic roads that’s what it’s going to have it willhave synchronizers in there the process is a bit different so you release thegas you press in the clutch and now whenyou’re shifting over to the next gear what’s happening is everything is at adifferent speed so you’ve released the clutch you’re inneutral and you’re about to go into the next gear so your engine is at one speed yourtransmission as far as these gears are in another speed and your output shaftis at a completely different speed this

is that your wheel speed of coursebecause this is going to your differential so what that synchronizer is doing is asyou bring this to third gear it’s going to match the speed of thegear to the collar and so that will allow you to get in gear and then onceyou’re in gear you can blip the throttle these are nowall rotating together and the only speed differential is between your engine andyour clutch and so you blip the throttle if you’re down shifting you will matchyour engine speed to your clutch speed and then you’ll release and then you’ll havethat smooth engagement so the the

benefit here of the synchronizer is thatyou don’t have to have the clutch engaged in order to match the speeds andso you know that’s why with modern cars you don’t ever have to do this doubleclutching technique because you have synchronizers that match the speed ofthe gear so what is this technique useful forwell basically if you have a transmission that doesn’t have synchronizers or if you do have atransmission with synchronizers but they’re completely worn out this is a method that you could use toshift gears where you had wouldn’t have

to worry about replacing thatsynchronizer if you got good enough at it and you could match your engine speed tothat collar speed and then get in gear without using the synchronizer simply bymatching the speeds so thank you guys for watching if you have any questionsor comments feel free to leave those below

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