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    shifting question

    When I shift into 2nd or 3rd at high RPMs my clutch seems to strip and I lose horsepower. It feels like the clutch is not connecting, and I have to let off the throttle to engage it. Does anyone know the cause of this and why it occurs?

    Re: shifting question

    worn out clutch?

    Re: shifting question

    Nope. Its happened for the last 1 1/2 years since the car was new. I have actually popped some type of "ball joint" twice when doing this around corners and have replaced it both times.

    Re: shifting question

    Be sure to release the clutch first and then put on some throttle...

    I am serious about it.

    Re: shifting question

    As Ferdie said, you might benefit from learning to operate a clutch/stick properly. My observation in the US is that few drivers who drive stick do operate it properly - clutch/stick is not taught in driving school in this country.

    Re: shifting question

    agreed, it may be your shifting technique.

    Re: shifting question

    My question is not about technique but about anyone's knowledge of the clutch apparatus or why this happens.

    Many do not know how to shift, but have you ever heard of this question before?

    Does Shumacher let off the gas when he shifts?

    Has anyone experienced when shifting the feeling like the clutch is "stripping" or not engaging?

    Re: shifting question

    Quote:
    GFORCED said:
    When I shift into 2nd or 3rd at high RPMs my clutch seems to strip and I lose horsepower. It feels like the clutch is not connecting, and I have to let off the throttle to engage it. Does anyone know the cause of this and why it occurs?



    When you depress the clutch to shift you are disengaging the clutch and at that point the clutch disc is not connected to anything. As you change gears, with the clutch pedal depressed, you may find you have trouble engaging the next gear. This could be because of worn or damaged synchronizers in the transmission.

    I don't think this is your problem though. I think the problem is that you are shifting with full throttle on and when you release the clutch the motor has gained significant RPMs and the clutch is having difficulty resolving the speed differential.

    Don't shift this way. Take your foot off the gas when shifting. It will allow the engine speed and transmission speed to be better matched when you release the clutch. A Porsche is not designed to withstand full throttle shifts. The disc is not big enough, the pressure plate does not exert enough force, the clutch return spring is not strong enough and the transmission is not designed for this kind of abuse. Leave the full throttle shifts for the american muscle cars.

    Re: shifting question

    Gforced,

    I am not trying to teach you and I'd say it is pretty difficult for us to evaluate this issue on the internet.

    I do believe that it could be the above mentioned reason. Schumacher doesn't have to back of the throttle since

    a. his car has an automated seq. gearbox with shifts in a fraction of a second and

    b. most modern racecars can be shifted without using the clutch at all and without lifting the throttle.
    Instead a gearbox sensor interrupts the ignition for a short moment to reduce the stress on the gears.

    My answer above is very simple and due to one physical effect. Sliding friction has a lower coefficient than static friction, in other words less force can be applied on this surface. This happens e.g. when you lock your brakes or launch with lots of wheelspin or possibly when you don't engage the clutch properly before stepping onto the gas.

    It is actually not even recommended to keep your foot on the clutch pedal, even if it feels engaged to you there might be insignificant slippage that will shorten the clutche's life - just to get an impression how sensitive these objects are.
    By the way, this shouldn't be an issue on a Porsche only. Did you experience this or similiar things on other cars?

    Of course I might be wrong, especially since I don't know your experience with manual gearboxes and the technical background.

    Could you give us some more info about it?

    Greetings!

    Re: shifting question

    GM Austin: I do let off the gas, but if I shift really quickly, and try to match RPM's I sometimes encounter this.

    Ferdie: I was just commenting on the "you don't know how to shift" issue referencing Schumacher.

    As far as letting off the clutch, you may be right, as I may not have fully released it when rapidly shifting in these instances.

    No, this never happened with my other cars, my 928 back in the day or my 02 996.

    I think you guys have nailed it though: When rapidly shifting, I may not fully disengage the clutch. When the next gear is shifted into, the clutch is spinning and not engaged.

    Thanks guys for the insight.

    Re: shifting question

    Does that sound right???

    Re: shifting question

    I think the clutch pedal is not fully released when you reapply power, causing the clutch to slip when it tries to engage. The motor is more powerful than the clutch spring in this instance. Once engaged, it will be able to hold and take the engines full power. Try not applying throttle until your foot is fully off the clutch. You can still shift very quickly, it's just a sequence and timing thing, one has to happen before the other.

    Re: shifting question

    Quote:
    GM Austin said:
    I think the clutch pedal is not fully released when you reapply power, causing the clutch to slip when it tries to engage.



    Incidentally, this is an excellent way to shorten the life of your clutch by overheating the lining surfaces. What's even better is, this kind of misuse leaves ovious tell-tale signs, so those spoilsports at your friendly local Porsche dealer won't fix it under warranty!

    Re: shifting question

    Quote:
    What's even better is, this kind of misuse leaves ovious tell-tale signs, so those spoilsports at your friendly local Porsche dealer won't fix it under warranty!



    Those guys! Where's their sense of adventure?

    BTW, I wouldn't be giving you this diagnoises if I hadn't done this a few times myself.

    Re: shifting question

    Quote:
    GM Austin said:
    Quote:
    What's even better is, this kind of misuse leaves ovious tell-tale signs, so those spoilsports at your friendly local Porsche dealer won't fix it under warranty!



    Those guys! Where's their sense of adventure?

    BTW, I wouldn't be giving you this diagnoises if I hadn't done this a few times myself.



    And did your dealer have a sense of adventure, or maybe a sense of humor?

    Re: shifting question

    My clutch lasted 70k miles, in spite of burnouts and powershifts. Go figure. And when it finally failed, it was the rubber hub that busted, not the disk face. I replaced it with a Sachs that did not have the rubber hub. That 2nd clutch was still working when I sold the car at 135k.

    Although the dealer did not work on the car when the clutch was replaced, obviously they would not have cared what the cause was since it would have been out of warranty.

    They do though seem to have a sense of adventure. They love my off-road photos. Some salesmen keep 8x10's in their office. They treat me pretty well there, no complaints.

    Re: shifting question

    Well, the dealership replaced my "Shifter cable" that snapped and said I drive "too aggressively." So who's going to give me the lesson on how to shift?

    Re: shifting question

    A PCA DE session might help.

    Re: shifting question

    Yeah, no time, costs too much. I think I figured it out...

    Slow down!!

    Re: shifting question

    Quote:
    GFORCED said:
    Yeah, no time, costs too much.



    More than new clutches and shifter cables?

    Re: shifting question

    Quote:
    GFORCED said:
    Yeah, no time, costs too much. I think I figured it out...

    Slow down!!



    No need to slow down at all! Just work on the technique.

    Re: shifting question

    GEFORCED consider this, get two lace or rope of same length but make sure that one has elastic. Now sew them together to their ends, and now take them to a door handle and run the elastic side to the left of the handle and the non-elastic side to the right. You will see that by pulling a lot of elastic side you pulling littl of the non-elastic, and vice versa. The elastic side is like a clutch and the non-elastic side is like an accelerator. I am not good at explaining things, but I still hope you get my point. This is obviously a crude analogy of the mechanics of clutch and accelerator, but when I was a kid this is how I learned to drive.

    Re: shifting question

    Quote:
    fritz said:

    More than new clutches and shifter cables?



    They're free under warranty!

    I think we've established that I was powershifting and that puts undue amounts of force on the cable. By the way, my clutch is fine.

    Re: shifting question

    Quote:
    GFORCED said:
    Yeah, no time, costs too much. I think I figured it out...

    Slow down!!



    I know you aren't going to believe this but the fastest way is the smoothest way and not the abusive way. If you can keep the car nicely balanced and controlled then you can actually get much closer to the edge without falling off. I know this might sound silly when it comes to shifting (and braking) but it is not. Smoothness counts in all directions.

    Stephen

    Re: shifting question

    Quote:
    GFORCED said:
    Well, the dealership replaced my "Shifter cable" that snapped and said I drive "too aggressively." So who's going to give me the lesson on how to shift?



    Practice...

    or

    you pay me the ticket to come to California!

    Try the above mentioned way to apply the throttle only when you released the clutch (and get of the throttle slightly before pressing the clutch pedal before the shift).
    As stated before especially in circuit driving a smooth shifting technique is the best way to go, to lower the stress on the box and reduce the amount of weight transfer during cornering.
    I would also recommend to move the gearshifter in two steps,
    1st take out the gear and stop in the middle of the gate and
    2nd put in the next gear.
    In other words don't tear through the gears, the time saved doing so doesn't justify the stress on the transmission components (in my eyes).

    You will figure that professional racedrivers are very, very smooth in shifting!

    Re: shifting question

    Quote:
    GFORCED said:
    Yeah, no time, costs too much. I think I figured it out...

    Slow down!!



    You may have heard/read it already:

    Ex-world champion rally driver Walter Roehrl has a reputation for being an extremely smooth driver.

    He does not have a reputation for being a slow driver.


    PS: I remember reading somewhere some years ago that Ayrton Senna said - after being driven around a circuit by WR - that he was the one driver in the world he would take his hat off to, because of his smooth style.

    Re: shifting question

    GFORCED, how close to SD do you live?

    Re: shifting question

    45 miles from San Diego. I'll be at Crystal Cove tomorrow around 8:00 AM.

    Re: shifting question

    It almost sounds like your not letting the clutch out fast enough, Im not very familiar with cars that have that much HP but it still doesnt sound right too me.

     
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