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Down shifting a DCT under how much throttle

Discussion in 'Tracking & Driver Education' started by Alexcle, Dec 14, 2019.

  1. Alexcle

    Alexcle Karting
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    Jan 2, 2018
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    Alex D
    hello all,

    I have a f12 and had a 991gts w pick as well. The f12 doesn’t shift Orner downshift as quick and my question is- I used to be able in sport plus have throttle all the way down in 6 when driving the Porsche and down shift sequentially I to the lowest gear ex.g goes to 5k rom without letting off gas and keep going.

    Can you do that to this generation of dct ex.g f12 and 458 or is it bad for fearbx. Upshift is ovipositor under full load but how a out downshift?

    My concern has to do w the fact my middle section gearbox was replaced in 1 month Ignatius ownership(gasket leak) it took a mi th to transport and fix. I am driving it in the winter as well and want to know what constraints the gearbox has. The old is bulletproof- honestly Ferrari’s gearbox seems less robust.

    Thanks for reading and input.
     
  2. daytona355

    daytona355 F1 World Champ
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    On my 458, I never had any issues with downshifting, the computer really only steps in for protection if you really **** up the shifting. Aside from that, it stays out of it, and I’ve had some glorious track time with the car, hammering up and down through the gears to get some fantastic lap times in, either using sport and race settings on the mannetino. That said, I’m not entirely sure of your question as it looks like autocorrect has been attacking your post, so feel free to expand on it
     
  3. Alexcle

    Alexcle Karting
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    Whoops,

    I didnt see all the errors on my mobile. To rephrase the question. if 75MPH is the shift point to the 3rd gear adn if I am in 7th gear at 75, will it harm the gearbox if i sequentially downshift until third gear which would be about 4,500 rpm with my gas all the way down. Or should i let off the throttle and then downshift to the lowest gear possible and then floor it?

    PDK in the porsche seemed bulletproof and I didn't worry about it breaking etc. the ferrari I am a little concerned due to recent replacement. Upshifts no worries at all of course.
     
  4. fatbillybob

    fatbillybob F1 World Champ
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    I'm trying to think why you would do that? If at 75 @ 7th and you need /want 75 @ 3rd...what are you doing in 7th? Isn't the mistake being in the wrong gear from the start?
     
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  5. Alexcle

    Alexcle Karting
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    Well,

    I would be coasting on Hwy, then I want full acceleration since 2 lanes free up or whatever and I am in manual 7th gear.

    This is not a track setting I am referring but wanted to ask this in the race section assuming people on this section drive their car in race conditions or on street harder maybe?
     
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  6. rlips

    rlips Formula Junior

    Jul 29, 2011
    935
    New Jersey, USA
    Generally, the expectation on a race track is that upshifts will happen under full throttle and downshifts will happen under braking. On a race track, every shift is done at redline, so there would be no reason to downshift under throttle. Every paddle shift transmission I've ever driven on a track (and road) seems to like this sort of operation, my guess is they are programmed that way. I generally teach students new to paddle shifting on track "right pedal, right paddle, left peddle left paddle."

    To the specifics of your question, If you are cruising in top gear on the highway, then the next lower gear is pre-selected by the computer with the assumption that you will request a downshift. Since there is no higher gear to pre-select, the computer has no other choice it can make. When you pull the paddle, all you are doing is selecting the other clutch, the lower gear has already been engaged. No mechanical gear shifting actually takes place, just a clutch switch.

    I imagine, that if you floor the throttle, and downshift out of top gear, the computer will make an assumption that you are either going to select a lower gear, or upshift next and it will pre-selet that gear. This is highly dependent on the programming strategy built into the box by the manufacturer. If you happen to ask for the gear that was already pre-selected, then once again, it will only be a clutch switching over. If you are asking for a different gear (lets say 5th when the computer guessed 7th was your next request) then the transmission will have to select the requested gear before it switches to the new clutch. Accordingly, it will take longer and may feel balkier.


    Hope this sheds some light on it.

    Cheers,

    Ron
     
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  7. Alexcle

    Alexcle Karting
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    RLips,

    You are correct that most auto will auto downshift to lowest. At 3rd gear and 75 great is redline shift off 2nd gear.

    I always drive in full manual and the car will not auto downshift. So let’s say For entertainments sake. I am coasting at 75 in 7th in full manual, then an aventador flys by. LOL ! I want to catch up or give chase, it would take too long to press the auto button on the console bridge instead, is it safe to sequentially downshift to third gear under full throttle? What would you do InThe situation?

    BTW, has not happened yet but I wish would!
     
  8. Alexcle

    Alexcle Karting
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    Oh yes last part of the question- will it harm the gearbox doing so under full throttle?
     
  9. Ky1e

    Ky1e Formula 3

    Mar 4, 2011
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    #9 Ky1e, Dec 16, 2019
    Last edited: Dec 16, 2019
    Shift how ever you want, the computer will take care of it. If it is bad or above rpm it wont allow the shift. If it allows it, it can take it. These cars can take all you can dish out, both on and off the track. It doesnt matter if you have the accelerator on or off regarding the car, but it does in regards to your driving technique. As others stated I cant see many situations needing to be full throttle while you are down shifting, but I do acknowledge ye sit can happen such as your highway passing example. In that case, yes you can do it if you need more acceleration and are not in the rpm power band. No problem for the gear box. I'd only do it for straight line acceleration though, as it would upset the car if you were in a corner or had any wheel in it. For those cases (having wheel in it) do a slight lift as you downshift. Not to save the gear box but to save yourself from losing control.
     
  10. Alexcle

    Alexcle Karting
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    Thanks ron i picked up the right paddle right pedal and left... good to know.
     
  11. daytona355

    daytona355 F1 World Champ
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    sequentially downshift, don’t delay by trying to switch to auto..... that’s what the paddles are for, Use your own senses to listen to the box and the revs, but going down you’ll have the revs jump up to match the gear speed each time, so you may go 6,5,4,3 very quickly, and the gearbox will let your surprisingly fast. However, it is controlled by you mainly, with only a safety feature within the software to protect the engine, so you have to be careful dipping so far down. It will cope, presuming the seeped you are already travelling is within the range of the ultimate gear to provide, but if you misjudge it, you may run the risk of overriding things in my opinion, so it’s going to depend on the situation at the time.
     
  12. Ky1e

    Ky1e Formula 3

    Mar 4, 2011
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    Yes you can manually downshift even with full throttle. No you cannot hurt the gearbox, nor over rev the engine, the computer will deny the shift if you are going to over rev the rpms. You do not need to be careful, you cannot over rev on a downshift, it will not let the shift happen if it puts you in a gear that is near or over redline.

    Side note, if in auto the car adapts/changes to your driving style. If you are driving lightly it will shift sooner and not have the rpms go up as high nor hold them as high, if you are driving very aggressively the shifts will change to match that style. For example if you floor it, rev it out and then de- accelerate the car will have more aggressive downshifts. Or if you then level out your speed it will hold the rpms at a higher level and stay in a lower gear as it knows you want to keep it in the power band because you are driving aggressively. Whereas if you were recently driving slowly, softly, it will cruise at lower rpms and select a higher gear.

    Second note: if you are at a stop and you accelerate hard off the line, full throttle and depress the throttle very quickly it will not peel out because it expects you want fast acceleration, but if you stomp on the gas extremely quickly/hard at full throttle (as fast as you can - literally stomp on it) it knows you want to peel out and will engage the clutch differently and allow you to do a full wheel spin and a long burnout. The car computer is designed to understand and read different driving styles based on your input and will change its shifts accordingly. You'll only notice this on extreme ends of the spectrum.
     
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  13. Alexcle

    Alexcle Karting
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    You am going to experiment this. Thanks all for your insight. STill driving it in this weather. 23 degrees and just snowed 2 in couple days ago- better than the battery tender!
     
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  14. Ky1e

    Ky1e Formula 3

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    have fun! the car can handle very hard driving.
     
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  15. Mr Turbo

    Mr Turbo Rookie

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    Alan,
    Congratulations on the wonderful IMSA website write up you received today. All of your success has come as a result of your dedication to honing your skills as a driver and you've learned your racecraft very well! It is always great to see you at the track, and I've enjoyed watching you excel in competition at that high level.
    Jim H
    btw, I was the guy that told you to get a dedicated race car:)
     
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  16. Ky1e

    Ky1e Formula 3

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    Hey Jim! Yes I remember, thank you for costing me deep into 7 figures! LOL Seriously though, thank you, I'm having the time of my life. 40 pro races and over 100 days on track in 2019 and it all started with a Chin track day at Sebring in the 458.
     
  17. DGS

    DGS Three Time F1 World Champ
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    FWIW, my EVO X (with a 6 speed Getrag) will downshift under most conditions (and then let the rev limiter catch it if you downshift too early).
    (Which happened a couple times when I first switched from the manual EVO VIII to the DCT EVO X. I had to get used to the downshifts being as immediate as upshifts. ;) (I'd been in the habit, with the manual, of pre-shifting with the clutch in, under braking, and then triggering the change with the clutch.))

    Generally, even on the street, I downshift under braking. The fast shifts make that practical.

    One of my common turns is coming off a 55 mph road onto a 25 mph side street.
    I just flick the left paddle three times under braking for the turn.

    But I keep the Getrag in "super-sport" setting (fastest shifts).
    (I'm told that the slower shift modes wears the clutches faster.)

    Best to read through the owner's manual.
    One "gotcha" on the EVO's Getrag is that it won't use 6th gear in "super-sport" mode when set to automatic shifts. (Also, the cruise control won't work in manual gearbox operation.)
    But Getrag programs even the same gearbox differently, for different vehicles, so your owner's manual is your best reference.
    (I saw an article complaining that the same 7 speed Getrag isn't programmed as crisply on a Mercedes as it is on the Ferrari.)
     
  18. NYFAIM

    NYFAIM Formula Junior
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    Generally if I'm cruising in overdrive, and I want to punch it, I'll keep the throttle steady and downshift until the rpms hit the sweet spot for torque - maybe around 5,000 to 6,000 rpm and then enjoy the sound of the engine as it rolls up to redline, and then shift. If you floor it and then downshift as far as the computer will let you, you'll like end up at redline almost immediately and then have to upshift. I doubt that you'll cause damage either way.
     
  19. Alexcle

    Alexcle Karting
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    Thanks for everyone’s input.
    I guess my concern comes from the Porsche pdk downshifts so fast. F12 not as fast and so waiting for that loses time/momentum. Not like I am racing on the street but still.
     

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