Can someone explain clutch slip better than...google?

  1. charleswrivers

    charleswrivers Senior Member

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    Yep. Think of your clutch like your brakes on a car w/o anti-lock brakes (for the purpose of this discussion... we want things to lock up). They're both similar devices enough to try to connect some dots... and if you know brakes a bit, it might make more sense. There's friction material just like your brake pads. The brakes use hydraulic pressure pushing on a piston(s) that are in a caliper… pushing the pad against the rotor. The clutch has a couple pieces... a pressure plate which has friction material that is being pushed against the flywheel from a diaphragm spring that's on a pressure plate (If you're not familiar with these... they're kind of like a wavy washer... but provide more uniform force than a wavy washer will. If you look up a picture... you'll see what I mean). When you push on the clutch pedal, you're pushing on the diaphragm spring and pulling the clutch disk of the flywheel... unlocking them. Random YouTube videos will help because they'll let you visualize the process.

    If there's enough pressure applied from the diaphragm spring which is part of the pressure plate and enough resistance from the friction material which is part of the clutch disk... the clutch, which is between the transmission and the engine will slip for a moment, the different speeds will equalize, then lock onto the flywheel and make them spin together. If there's not enough force from the diaphragm spring (which... BTW... a weak diaphragm spring is indicative of a light clutch pedal, which we have in our cars) then it won't lock on and it'll slip... as the friction material is wearing on the flywheel surface. Just like brake pads... if you slip them enough to get hot... pads will glaze. That will make them have a burned in 'glassy' coating. When that happens... they'll provide far less friction and slip more. That's why clutches that are allowed to slip a lot will actually lose holding power... along with the loss of friction material depth means the diaphragm spring has less length of material to push on... and it's going to provide less force. The only variables I know of that'd affect the holding power of clutches would be the surface area that's contacting the flywheel... the type of friction of the material and the force the diaphragm spring in the pressure plate is exerting on the clutch disk. There may be more I don't know about... but that's all that comes to mind.

    What happening with the clutches slipping most people are seeing and saying our clutches are weak is that it's initially engages and locks onto the flywheel... but when you go WOT... the engine is making sufficient torque vs the counter torque of the transmission and everything downstream it such that there isn't enough holding power and the clutch becomes unlocked from the flywheel and is spinning against it... heating and wearing the clutch material... heating and scoring the flywheel. You see it by engine RPMs rising but without an equivalent expected increase in vehicle speed. It's because the engine is unlocked from and moving faster than transmission.

    That's why when you're running TSP Stage 1... you can just look at the torque curve from the dyno and see where things would be at their worst torque-wise... around 3000 RPM. So far as counter torque... think of a bicycle with gears. You hop on a bike that's running slow then try to pedal in the highest gear. It takes a huge amount of effort... though you're turning the pedal slowly to keep it going. Just like trying to turn a stubborn bolt with a tiny wrench vs a breaker bar... it's the same with a small gear vs a larger gear. If you give yourself more leverage, you can essentially accomplish the same amount of work (distance traveled of said bike or bolt) with less force (torque) applied, albeit with the need to do the work over a greater amount of rotational spinning (speed of pedaling or the travel of that big breaker bar vs that tiny wrench). That's why I encourage people to let their cars rev out.... use the power at higher RPMs to spin a larger gear faster than a smaller gear slower. In the end... even with a tiny turbo that spools quick, the car makes far more power and will accelerate faster by revving it out.

    You're always slipping a clutch a little when you're shifting gears at portions of the clutches intermediate position... especially from a stop. When the car is at a stop... if you made the engine speed equal transmission speed... then engine speed drop to zero (because the transmission is stopped) and the engine would stall... or you would have been dumping the clutch, creating a huge amount of stress and causing the transmission to essentially accelerate immediately. Slip is necessary to allow the engine speed and transmission speed to meet without the engine stalling/excessive strain. That's also why flywheels are important... because they're just a weight to store mechanical energy. They're a big spinning weight at connected between the engine and the transmission the clutch is locking on to to ensure the engine has enough momentum built up that it doesn't stall when the clutch is engaged. Folks that run light flywheels have to slip clutches more and (or) spin an engine faster before letting off the clutch to keep an engine from stalling.

    "Riding" the clutch is bad because you're intentionally keeping your foot on the clutch pedal when driving. That is allowing the clutch to constantly slip. That will cause the aforementioned wear and overheat that can lead to glazing and early clutch failure. Novices who want to go slower than the idle speed with a car just in 1st or 2nd (~3 and 6 MPH for the Si) will ride the clutch to allow a slower speed from continuously slipping the clutch... but will cause their clutch to fail early in the process.

    Videos are very informative... when you see it work... it makes sense. It's one of those things... like a CVT that's actually kind of simple, but unless you see it work... it seems like PFM.
     
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  2. ne0guri

    ne0guri Senior Member

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    This ^
     
  3. swah_fk7

    swah_fk7 Regamaster King

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    Minor slipping is hard to catch, but I notice sometimes in 5th and 6th gear if I gun it from a low rpm in the gear, youll see rpm climb faster than "normal" and when you let off, the rpm will drop suddenly as if the clutch was trying to "catch" the flywheel.
     
  4. NoelPR

    NoelPR Senior Member

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    I thought that every late civic si owner are experts on clutch slipping topics.
    Is a very common thing on this car LOL
     
  5. swah_fk7

    swah_fk7 Regamaster King

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    1200 miles in, slipping in 5th and 6th with a tune.
     
  6. H3llsp4wn707

    H3llsp4wn707 Senior Member

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    Its easy- when you pull out in 1st gear your tires will be skipping, and feels just like wheel hop. Load your car up with 5 people and take off normally from a dead stop. If you feel the car stuttering and bucking while you pull forward your clutch is slipping.

    Seriously though, this is either the weakest clutch offered in any car on the planet or you Si drivers are the .worst
     
  7. swah_fk7

    swah_fk7 Regamaster King

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    The clutches are very very weak.
     
  8. H3llsp4wn707

    H3llsp4wn707 Senior Member

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    I seriously cannot believe how bad this clutch is. There has to be a defect, this is not normal.
     
  9. swah_fk7

    swah_fk7 Regamaster King

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    As noticed right away with the weight of the pedal, it's not a mystery that the clutch cannot hold the torque produced by the tiny turbo. I have 1250 miles on my odometer, I babied the car and city drove the first 1000 miles. My car slips under WOT in 4th, 5th, and 6th if I'm low enough rpm.
     
  10. charleswrivers

    charleswrivers Senior Member

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    I don't know... if you stayed NA on the 8th/9th gens, even going FBO wouldn't crack 200 ft/lbs. Unless you stayed on the mildest belt on a SC, I saw noise of needing to replace clutches... and that's just in the 250 ft/lb range for 9th gens.

    I don't think Hondas have ever necessarily had clutches that can take whatever you could possibly throw at them... they just managed to stick a tiny turbo on our cars that can make 300 ft/lbs if you let it. I know GTIs can do that on APR tunes but I don't know if their stock clutch is up for it. The only guy I know who had a GTI, a MK6 never said anything about replacing his after APR, though I never asked. I never have followed Ford's so I have no idea.

    That said, I've never had issue with my clutch. Perhaps we should do a poll and see who's running a reflash/basemap and clutch problems vs none. (shrug) I still bet there's far more w/o problems.
     
  11. rive

    rive Senior Member

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    Enough people have tried to explain what happens. I'm going to explain how it feels...emotionally.

    Imagine going to the fair with your best friend and seeing the coolest ride ever. You give up your spot in line to someone who got separated from their friends because you're considerate like that, but it turns out your friend gets the last seat and you have to wait. Now you're watching your friend have the time of his life and hearing all the noises and screams while you stand there feeling nothing. You're suddenly empty inside. Sure you can get your fun the next time, but it's too late. The moment was already ruined and, even when you get your chance, you're left thinking about what went wrong.

    This moment brought to you by clutch slippage.
     
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  12. turbociv910

    turbociv910 Senior Member

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    clutch slip. clutch is engaged to the transmission and engine is turning, wheels dont turn. clutch slip.
     
  13. joshhjackson2112

    joshhjackson2112 Senior Member

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    I can tell my clutch does not hold all of the power I am pushing with TSP Stage 1 but it holds for the most part. As long as I ease into the boost and not just WOT from the start, I hold power pretty good. I will know more when I get my CTR retrofit installed. I could just be used to it by now and can't tell how bad I am slipping. IMHO, people shouldn't be slipping in 5th or 6th gear because they shouldn't be searching for power here. I don't give more than 20% throttle in these gears. If I need to pass someone, I am dropping it to 4th gear. 4th is good for power until like 90 mph and I think that's not even hitting red. (Could be wrong on this last statement. It's been a while since I have been there)
     
  14. unholy79

    unholy79 Senior Member

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    Ok so after reading this I'm wondering if my clutch was actually slipping... I ran the Ktuner base tune... the 19/21.5 I think for about a month, and the behavior I saw wasn't that the RPM's were climbing but the needle wasn't moving... in my case the RPM's stopped climbing. The car was still accelerating but instead of a steady RPM climb, the RPM's climbed more slowly if not just hovered over a specific RPM. Very weird to describe. Either way I pulled the tune off because I found it completely foreign to what I was used to.
     
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