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Thread: 450 Gearbox change speed discussion

  1. #1
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    450 Gearbox change speed discussion

    Just so we don't hijack the other thread.

    Jake,

    Where did you get the information about the 600cc and 700cc gear changes? Is that just hearsay from one of the many "tuners" out there?

    I am sorry to say but until someone can produce documentation showing the comparison between an "un-mapped" cars gear change and the corresponding "mapped" gear change both of which are taking the time scale from the same "trigger" point I shall remain unconvinced.

    I haven't had a chance to look at this document Forbes has sent me yet, but the only way to decrease the time the gearbox takes to change gear would be to reduce the time taken for A) the mechanical things to do their jobs and B) the reduce the time taken for the electronics to do their jobs.

    Now I don't know about you, but as far as I am aware, electricity travels at the speed of light (near enough) so you can't speed that up!
    The ECU will have some finite time it takes to do the calculations between receiving a signal and then sending a signal to any given sensor or Actuator. You can't change that.

    Below is my understanding of how things work:-

    So the things you can change are:

    The speed at which the mechanical things work at.
    The number of calculations that are required between a signal being received and one being sent.

    The speed that the mechanical things work at can be improved by reducing the friction they encounter. i.e. lubrication of the clutch actuator, correctly set clutch plate, correct oil in the gearbox, Boosting the voltage to both the clutch actuator and the gearbox motor to make them "move" quicker. As pointed out a lighter flywheel can improve things but only in as much as it makes the difference in the engine speed and the gearbox input shaft change more quickly which in turn means the signal to the ECU is sent sooner in the sequence.

    The electronics obviously have some "wait" periods in the coding so that it does not try to move the the gearbox motor whilst the clutch is still engaged or re-engage the clutch with the revs too low if you are travelling at speed. I.e. it has some error checking to do before it allows the requested gear change to happen.

    If you compare a "manual" gear change sequence;
    1. Foot off accelerator - revs start to fall.
    2. Foot on clutch.
    3. Hand moves gear lever - being mechanical, gears in gear box move simultaneously.
    4. Foot off clutch
    5. Foot on accelerator.

    1 and 2 above can be done more or less together by the human brain - either one starting the sequence.
    2 and 3 above can also be done more or less together, but there is a time delay unless you want horrible noises from the gearbox!
    3 . makes use of the fact the human decides the gear lever has got to where it should be before commencing 4 and 5.
    Oh yes, forgot to point out that the human involved also does error checking - like making sure you move the gear lever to the correct gear.


    In the SMART's gearbox.
    1 and 2 are two separate things. The ECU has to wait for the signals from the sensors and it does 2 before 1! It has to get the request signal from the SE drive to change gear, this starts the sequence.
    The ECU knows which gear it currently is in and correctly interprets the request for the next gear.

    ECU tells clutch actuator to disengage.
    Clutch actuator moves -- No possibility of speeding this up as it is dependent on actuator speed, other than grease or more volts.
    Clutch actuator provides signal to tell ECU whether clutch is disengaged.
    The bite point of the clutch has parameters which can be altered, but they may result in either clutch slip or clutch drag if they are to far out.

    So once it has disconnected the clutch, it needs a signal from the transmission speed sensor to confirm the RPM of the shafts / gears is suitable for it to signal the gear change motor to start turning.
    If this is outside set parameters then it waits until they are acceptable.
    (Possibly you could change the values of these to allow the rest of the sequence to happen sooner)
    It needs to know which way to rotate the motor - more error checking to make sure it is going the way it is supposed to. - No possibility of speeding this up as it is dependent on motor rotation speed.

    Motor gets to position for requested gear.

    Signal from the gearbox motor to say it has moved to the required position.
    ECU has to do more error checking to confirm this.
    There are no parameters that can be altered here as it is either in gear or not.

    ECU can send signal to clutch actuator to re-engage the clutch. - No possibility of speeding this up as it is dependent on actuator speed, other than grease or more volts.
    The bite point of the clutch has parameters which can be altered, but they may result in either clutch slip or clutch drag if they are to far out.

    More error checking to make sure the shaft speeds between the engine and gearbox are with in given limits

    Sequence can be completed.


    The above is food for thought and may be entirely wrong. Hopefully once I have had a chance to translate and study the document Forbes sent me, I will be able to improve upon this.

    John

  2. #2
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    Quote Originally Posted by Heinkeljb View Post
    ... Hopefully once I have had a chance to translate and study the document Forbes sent me, I will be able to improve upon this.

    John
    You will struggle using Google or other suitable software to translate that document. Better just reading the original text and refresh your school German as you go.
    Drives a Smart Cdi - 65 to 85 MPG

  3. #3
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    Is the 451 any quicker, and if so why?

  4. #4
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    Am looking forward to seeing the outcome of this thread

    Does seem that in gear acceleration is mainly acceptable (im in 600cc) but the gearchanges are the plague of acceleration!
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  5. #5
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    Quote Originally Posted by XTEN10 View Post
    Is the 451 any quicker, and if so why?
    Different box.......

  6. #6
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    Hi John,

    I'm not sure where I saw the percentage improvements of 10% for the 700cc and 25% for the 600cc as it was quite awhile ago now. I'll try and see if I can still find the information.

    The 700's are widely talked about having quicker gearchange times than the 600cc and so that shows that if smart sped up the gearchange, then it's possible to do it within certain remaps as the actuator and gearchange motor are the same across both models.

    As far as I know, only Big Performance remaps (sold by Ian and Digitec) and SW-Exclusive maps (that Fudgesmart sell) quicken up the gearchange. SW-Exclusive maps as they're developed in Germany have a TÜV rating, showing that the bhp and torque has been tested by a truely independent company (as it's quite easy to inflate dyno figures) to ensure safety and accuracy in the products abilities (power). As SW-Exclusive maps also advertise a quicker gearchange speed, this would have been tested as well.

    Based on those two points, I'm confident there is an increase in the gearchange speed.

    XTEN10: The 451 does have a completely different gearbox. Smart marketed the quicker gearchanges on the 451 by saying that it has 5 proper gears and not the 2 x 3 gears that the 450 has. The only gearchange that took two changes on the 450 was 3rd to 4th though and so I think the whole system has probably seen an upgrade as well with a different actuator, gearchange motor as it's quicker at changing every gear.
    _________________________________________________


  7. #7
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    Quote Originally Posted by Heinkeljb View Post

    ECU can send signal to clutch actuator to re-engage the clutch. - No possibility of speeding this up as it is dependent on actuator speed, other than grease
    Oh dear! Trawled my maintenance notes and found this:

    ''09/06/10.45790mls Digitec back on. Some tidying up of induction pipes.
    Hosed plenty LE9102 into cluch actuator.''

    So at the same time as I fettled the induction system I also greased (for the first time) the clutch actuator, LE9102 being the grease I used.
    The only question I have now is which to eat first - humble pie or the egg on my face?

  8. #8
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    I am still waiting for a friend of mine who is fluent in English and German (amongst several other languages) to translate the document for me. He's even pretty good with the technical stuff.
    So you have a while to decide which to eat first
    The reduction of friction in the system is likely to have as much effect on gear change times as anything else and doesn't cost nearly as much!

    John

  9. #9
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    Quote Originally Posted by Heinkeljb View Post
    So you have a while to decide which to eat first
    Thanks buddy!

    Quote Originally Posted by Heinkeljb View Post
    The reduction of friction in the system is likely to have as much effect on gear change times as anything else and doesn't cost nearly as much!
    You haven't seen the price of LE9102....

    I'll give it a bit more thought (it was a two years ago now) but I obviously greased the actuator around the time I was messing with the pipework.
    Something I'll look at also is an article on a newly developed torque sensor for automotive application that measures actual torque at the crank. It is destined to be used on DCTs. The implication (from skim reading it a few months back) was that thus far DCTs and AMTs deduce the torque from ECU parameters when re-engaging the drive (clutch) and are thus an approxomation which obviously requires margins as only an estimate is obtained (the new sensor is precise). Still, it is in my mind that my induction mods helped speed the gearchang, but only valid if I can remember any improvement occurring before I greased the actuator. Time to lean on my memory then....

  10. #10
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    Ok Noob Alert but why does induction affect gearchange? Is it related to the turbo spooling up?? Sorry no mechanic but would like to understand?

    Thanks
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