Down shifting a DCT under how much throttle

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

 

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?

 

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

 

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.

 

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.

 

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.

 

have fun! the car can handle very hard driving.

 

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

 

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.

 

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.)

 

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.