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Thread: Slipper Clutch Vs Engine Braking

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    Default Slipper Clutch Vs Engine Braking

    Hello everyone!

    I am new to this awesome community. Has been a silent observer for few years now, and this is my first attempt to participate. I have a query for which I still couldn't get a proper answer yet. Slipper Clutch Vs Engine Braking.. Does slip clutch affect engine braking? My understanding of slipper clutch:

    1) Aggressive downshift induces wheel hops which are controlled by the slip clutch, so basically it rev matches
    2) Good for tracks when you want to go into the corners in a more controlled way so you can gun out of it

    Engine braking:

    1) Close the throttle and let the piston struggle for air, which causes the engine to slow down rather than just relying on the hydraulics and pads..

    I just booked my Duke 390 and will be getting it in couple of days.. Now despite all the excitement i went through some reviews which explained that slipper clutch might reduce engine braking Even after frantically looking for the connection between the two on the internet, is still a grey. How much truth is behind this? Can some experienced riders throw some light on this?

    Note: I searched through multiple threads and couldn't find anything close to it, so decided to start a thread. Hope this is not breaking any of the rules/regulations of the forum.

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    Default Re: Slipper Clutch Vs Engine Braking

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    Default Re: Slipper Clutch Vs Engine Braking

    From my experience on the Ninja 300, the slipper clutch comes into play only when downshifting, so in essence the engine braking is induced in any case. What the slipper clutch does is to match the revs of engine braking to the rear wheel which is controlled by the ECU and thus prevents the rear from sliding under you. As far as reducing engine braking is concerned, it depends a lot on where you are in the rev band. Since the rev band on a N300 is fairly wide a few downshifts in a low gear below 8000 rpm is not going to have any dramatic results in engine braking but will get different when one is higher up the rev band.
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    Moderator Divya Sharan's Avatar
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    Default Re: Slipper Clutch Vs Engine Braking

    Shorter version:

    Yes, slipper clutch reduces (or kills) engine braking at high revs. Useful on the track, not for daily commuting.

    Longer version:

    Engine Braking Occurs when a gasoline engine is used to slow the bike down rather than the use of the normal hydraulic braking system with calipers, pads, and disks. It occurs when a partial vacuum is created in the engine as the throttle is released. The change in pressure in the intake system by the closing of the throttle bodies creates a braking force internal to the engine which is transmitted through the drive-train that slows the bike down. This is most noticeable going from wide open throttle (WOT, throttle bodies are open as much as possible) to fully closed throttle.

    NOTE: Even with fully closed throttles, air is still able to enter the engine via the idle adjuster valve . The idle valve allows a small amount of air to enter the cylinders so that the engine is able to idle properly with no load. As the throttle bodies open, the required amount of air will enter through them instead.

    This drastic change in pressure inside the intake path (near the throttle bodies) causes the work created by the piston in the Ignition Phase to be mostly transmitted to the piston in the Suction Phase to draw new air into the cylinder rather than to rotate the gears. Think of trying to fill your lungs with air, sucking through a paper towel roll and then trying to fill them again but this time sucking through a little mixed drink straw. Your lungs will have to work harder with the smaller straw. As the throttle closes the area that the air can travel through gets constricted just as the little straw has a smaller area (more constricted) than the paper towel roll. Well, the engine has to work harder to draw air in at the same rpm with a close(ing) throttle than it did with an open throttle.

    Now, this engine braking as stated before gets transmitted through the transmission (drive-train) to the rear wheel. Since we were accelerating down the road and decided not to use the brakes for this turn coming up but chose to engine brake instead, we need to realize that the wheel has been rotating accordingly to push the bike forward. Well as we engine brake - the wheel is still trying to rotate at that speed we let off the throttle at; but now the engine is slowing is down. Without changing gears, you’ll feel this as the bike trying to throw you forward. As the bike accelerates, it seats down due to the interaction of the geometry of the swing arm with the sprockets and chain and therefore, as the bike decelerates, the bike leans forward. This becomes noticeable as engine braking is done at higher speeds (engine speeds and ground speeds).

    Shifting can also cause engine braking. In the same process that you change gears when you reach a high engine speed (rpm), the reverse will happen when you down shift from a high gear to a low gear. Shifting from 4th to 3rd will require that the input and output shafts in the transmission match speeds. This is done by engaging the clutch (removing pressure), opening the throttle briefly, shift gears, slowly release clutch. Now you’ll be riding at the same speed in a lower gear but with higher rpms. If done correctly, it shouldn’t slow you down. If the engine speed is not increased enough, the speed of the rear wheel, that’s dictated by the output shaft, will be faster than the transmission’s input shaft. When the clutch is released, the inertia of the wheel and the output shaft will cause the engine to speed up while the throttle is held constant. Guess what - that’s engine braking for you! The engine will be trying to get more air through the throttle bodies but is having to work harder because of the constricted path.

    When setting up for a corner, say at a track day, this can really mess you up. Under normal commuting speeds or canyon carving speeds, it’s less noticeable.

    So this is where the Slipper Clutch comes in to play.
    We know that the clutch assy is made up of plates and dogs that when pressure is applied, engage the transmission clutch gear (which transmits the rotating power from the crankshaft to the transmission from the primary engine sprocket) with the transmission input shaft that has the forward gear pinions. When pressure is released, the transmission clutch gear rotates while the transmission input shaft does not, and when pressure is applied, the transmission clutch gear and input shaft rotate together.
    Since we’re not releasing pressure on the clutch as we shift to setup for that corner coming up, the speed difference between the gears causes the engine and wheel to change speeds as well. So let’s say we were in 6th and are shifting down to 3rd for the corner with engine braking. The engine is running at a mid range rpm, now we engine brake and shift down to 5th. The engine that was trying to slow down now has to jump in rpms to mesh the transmission speed with the ground speed. Now the shift down from 5th to 4th causes a similar jump in rpms and again from 4th to 3rd. Each time the engine has to work harder to get the new air into the cylinders at a higher rpm.

    What makes a slipper clutch different is the interaction of the clutch plates with the transmission clutch gear through the use of two sections instead of one for the transmission clutch gear. The two sections have ramps and ball bearings that allow the part of the gear that is engaged with the engine pinion to keep rotating at the engine speed while the other section to rotate at the speed of the rear wheel and transmission output shaft. The ramps act in the same ways as one way screws. They allow rotation in one direction but not the other. So as the rear wheel tries to maintain ground speed and drive the front sprocket and transmission at a higher speed than the engine, the ramps slip up and the clutch disengages (pressure removed). Once the speeds begin to match again, the ramps allow the sections to mate up and continue to transmit power from the engine through the clutch through the transmission to the wheel. This ability to disengage the clutch allows the rest of the bike to remain smooth and stable negating the harsh engine braking that might happen when setting up for a corner. The benefits are usually seen at the higher range of engine and ground speeds.


    Source(s) - experience + various articles.

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    Default Re: Slipper Clutch Vs Engine Braking

    Quote Originally Posted by hariiharan View Post
    Hello everyone!

    Slipper Clutch Vs Engine Braking.. Does slip clutch affect engine braking? My understanding of slipper clutch:

    Even after frantically looking for the connection between the two on the internet, is still a grey. How much truth is behind this? Can some experienced riders throw some light on this?
    1. For same engine size, two stroke engine produces more power than a four stroke engine, however two stroke engines were replaced by four stroke engines due to numerous advantage associated with four stroke engines.

    2. Engine Braking is more of a problem in a 4-stroke engine than a 2-stroke engine. Four stroke smaller engines, rather single cylinder engine has more pronounced engine braking effect, as compared to two stroke engines. That is the reason why we have not heard/come across engine braking in earlier two stroke motor cycles. The effect was there but attention was not required to counter engine braking effect.

    3. This effect is due to four cycles associated with four stroke engines. When the intake valve is closed, the piston has to work against the closed valve inside the cylinder which effects the engine to slow down considerably and reduces the rear wheel speed. (You know very well what happens when the rear wheel slip results in-instability, loss of traction, loss of control on bike, chain slapping, loss of lap time, accident - may be fatal)

    4. To counter the engine braking effect, instead of normal clutch, slipper clutch was introduced. This served same purpose like normal clutch with added advantage. The advantage best utilized on tracks which has curves of varying degree with varying radius. The slipper clutch helps the racers to manage fast lap times and with confidence to kill corners faster and faster and brake as late as possible. Hence slipper clutch has become very popular track accessory.

    5. Now a days slipper clutch is street legal and seen in many high end motorcycles. Can be added accessory on street cornering, hill cornering apart from practicing track days.

    Hope this also helps in further understanding.

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    Default Re: Slipper Clutch Vs Engine Braking

    Quote Originally Posted by Divya Sharan View Post
    Shorter version:

    Yes, slipper clutch reduces (or kills) engine braking at high revs. Useful on the track, not for daily commuting.

    Source(s) - experience + various articles.
    Wow!That's one good read, thank you! Is Throttle Blipping sort of manual alternative for Slipper Clutch?

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    Default Re: Slipper Clutch Vs Engine Braking

    Quote Originally Posted by mknaidu11 View Post
    4. To counter the engine braking effect, instead of normal clutch, slipper clutch was introduced. This served same purpose like normal clutch with added advantage. The advantage best utilized on tracks which has curves of varying degree with varying radius. The slipper clutch helps the racers to manage fast lap times and with confidence to kill corners faster and faster and brake as late as possible. Hence slipper clutch has become very popular track accessory.
    Advantages of slipper clutch:

    While riding a corner you require to downshift.
    You have to give the bike slightly more throttle prior to downshifting, so that you are at a higher RPM to match your speed.
    Example, if you are cruising in 6th gear on the highway at low rpm, and you want to shift quickly straight to 4th.
    You will have to raise the rpm a little high.
    Now suppose if you are not matching the rpm/revs and just shift to 4th gear from 6th gear at the same rpm, the result is wheel locking up (as the wheels + engine are running faster in 6th gear and you want to make it slow at 4th gear, wheel minus engine)

    A slipper clutch is designed such that you keep slipping if you downshift too quickly/aggressively without matching the right engine rpm.
    jazzysaravana likes this.

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    Default Re: Slipper Clutch Vs Engine Braking

    Quote Originally Posted by mknaidu11 View Post
    Advantages of slipper clutch:

    While riding a corner you require to downshift.
    You have to give the bike slightly more throttle prior to downshifting, so that you are at a higher RPM to match your speed.
    Example, if you are cruising in 6th gear on the highway at low rpm, and you want to shift quickly straight to 4th.
    You will have to raise the rpm a little high.
    Now suppose if you are not matching the rpm/revs and just shift to 4th gear from 6th gear at the same rpm, the result is wheel locking up (as the wheels + engine are running faster in 6th gear and you want to make it slow at 4th gear, wheel minus engine)

    A slipper clutch is designed such that you keep slipping if you downshift too quickly/aggressively without matching the right engine rpm.

    So the wheel locking can happen even in street as most of us are use to engine braking by downshifting. And having a slipper clutch for a street bike too will help reduce the wheel hop, correct? Ideally we should be rev matching during this process and most of didn't practice and got used to quick stop in a wrong way. By wrong way i mean engine and transmission damage on the log run (?)
    Last edited by hariiharan; 11-03-2016 at 02:26 PM.

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    Default Re: Slipper Clutch Vs Engine Braking

    Quote Originally Posted by hariiharan View Post
    So the wheel locking can happen even in street as most of us are use to engine braking by downshifting. And having a slipper clutch for a street bike too will help reduce the wheel hop, correct? Ideally we should be rev matching during this process and most of didn't practice and got used to quick stop in a wrong way. By wrong way i mean engine and transmission damage on the log run (?)
    Motorcycle gears are not syncromesh type like in Automobiles, they are constant mesh type (all are in touch) where in all gears are engaged and the one which is being used is locked. Therefore chances are bright for damage if not used with correct practice.

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    Moderator Divya Sharan's Avatar
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    Default Re: Slipper Clutch Vs Engine Braking

    Quote Originally Posted by joe_marvy View Post
    Wow!That's one good read, thank you! Is Throttle Blipping sort of manual alternative for Slipper Clutch?
    Thanks. Yes throttle blipping is the manual way of achieving the same effect.

    Quote Originally Posted by hariiharan View Post
    So the wheel locking can happen even in street as most of us are use to engine braking by downshifting. And having a slipper clutch for a street bike too will help reduce the wheel hop, correct? Ideally we should be rev matching during this process and most of didn't practice and got used to quick stop in a wrong way. By wrong way i mean engine and transmission damage on the log run (?)
    See, unless you ride like a maniac 'on a frequent basis' and dump the clutch at very high RPMs in too low a gear will you damage the drive-train. Until now, even racers used to blip the throttle. And addition of slipper clutch hasn't increased the engine life even on a moto gp bike (no official sources to claim so).

    Therefore, it is safe to say that a commuter doesn't need a slipper clutch. I engine brake all the time and I'm about to hit 1 lakh km on the ODO. My bike is stock.

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