What's the best method to do a quick launch without launch control? Never had a dct. Do you footbrake like with an automatic, do you dump the clutch like a stick shift or just stab and steer?

 

The info below may be confusing, but it is from the Owner's Manual. It's used with a "double paddle declutch". Holding both paddles in at the same time is like holding the clutch, in a manual transmission car, while you increase the RPM's to the point you want, then releasing the levers/clutch and off you go. There is video, from Jeremy Wellborn, on Youtube that shows different launch controls and this method of rapid exit.

Rapid Exit : This is intended for use at a
closed course race track and not on public
roads. Engine power is reapplied to the
wheels quickly to support spirited driving.
The rate of launch is dependent on how
much the accelerator pedal is pressed when
the paddles are released: The further the
accelerator pedal is pressed, the greater the
rate of launch. Tire spin may occur with the
accelerator pedal pressed and the Traction
Control System (TCS) turned off.
This launch occurs when both of these
conditions are met:
. Vehicle speed is below 10 km/h (6 mph).
. Both the + paddle and − paddle are
released at the same time.
With the accelerator fully pressed and the
engine at the rev limiter, peak performance
only occurs if the paddles are released
within a short period of time after reaching
the rev limit (i.e., a few seconds).
Standard Exit : Engine power is reapplied to
the wheels gently to support normal vehicle
operation on public roads.
This occurs when paddles are released under
any of the these conditions:
. Vehicle speed is above 10 km/h (6 mph).
. The vehicle is in R (Reverse).
. The + paddle and − paddle are not
released at the same time.
If the vehicle was in Temporary Manual
Paddle Shift mode before entering Double
Paddle Declutch, the vehicle will return to D
(Drive) with automatic shifting upon exiting
Double Paddle Declutch.

 

Good info. Guess Ill have to read the entire owners manual like a normal person with this car. Was thinking about the when your messing with one of your buddies or on a road to nowhere and don't want to mess with all the features to get into launch mode. Also want to be able to do as much of the controlling myself without the computer doing everything. Kinda like a two step for the drag strip. Works great at the strip but to cumbersone for around town.

 

And, what does "best method" mean? Fastest 0-60 time, or simplest to execute? Sometimes, I just put mine in Track mode, release brake and hit da gas.....Its a plenty fast launch that will impress most passengers. May or may not beat that "buddy" you are "messing with". I don't turn any of the so-called nanny feature off. I occasionally will get some initial wheel spin, spectacular shifts, great exhaust sounds (NPP) - and totally stable operation. Watch out for wheel hop (I have never had that happen but others have) and stop accelerating immediately if that happens. I have never used the rapid exit mode, nor the launch mode, and I have never used the 0-60 timer.

 

^^^^
Yep, have done several 0 to 60+ in a row for some friends on the 3/4 mile little traffic road between farm fields near my house. Plenty fast enough with just WOT. Pins them back in the seat and as you say, safe with all nannies engaged. Launch Mode is fine occationally but not really needed to appreciate the C8 traction and acceleration.

Might get slight wheel spin on the 1st but with warmed tires, sticks like glue. Much more traction than even my 2017 Grand Sport with 335 rear tiers.

 

My last vette was the first one I never had a race on the street with. Maybe my area is too congested or I'm getting smarter in my old age. This one will probably be the same but I still have to know how. Last one was also the first one that remained stock. Probably another big reason. Racing a stock car is not much fun for me. No secrets about what it can do.

 

^^^
Well IF foolishly racing on the street then use Launch Mode. GM says they keep BOTH clutches engaged (for at least the 1st few shifts) that decreases 0 to 60 times. (They don't go into detail how they do that OR for how many milliseconds!)

Yep when I turned 19 stopped racing on the street! I did foolish stuff before that but got smarter once I reached 19! As I often say I'm 79 and turn 19 when I get in the Vette!

SIDEBAR
An interesting statement was made with no details by GM’s Chief Corvette Engineer, Piatek (not to be confused with Tadge Juechter who is the Executive Chief Corvette Engineer- read higher pay! ) : “We found that during very aggressive launches we can drive torque through both shafts/clutches simultaneously which improves the 0 to 60 times.”

Road and Track interpretation of that statement was: "With the C8's Performance Launch mode, the car will actually use the inertia of the engine coming down between revs to propel the car forward. Chevy calls these "Boosted Shifts," and they're only used with a Performance Launch."

 

Stab and steer or footbrake may be your best bet. A double paddle pull "clutch dump" at say 4-5k rpm is not received well by the ecu and it kills timing until the clutches fully engage.

 

I got at least 1500 miles before I can bang on it hard. Just trying to understand how the trans and ecm work together. My c5 with street tires did best with a 2500 or so dump. Any higher and it just spun tires with the 4:10s.

 

Read the Rapid Exit mode, which is in the manual, and also in post 2 above. It is a legitimate procedure, so one would assume that the ECU is programmed to "receive it well" and do whatever it is supposed to do. Having said that, I have not ever executed it, and do not plan to do so.

 

Yep back-in-the-day had to learn to execute what the Beach Boy's song Shut Down said! With the skinny tires we had available and 4.56:1 dif gears I had in my Coupe No Choice (Business Coupe came with what was called the baby flathead, 2.2 Liters 60 hp so Henry included that dif so it could go up hills.)

Once I stuffed in the modified Olds engine had to Ride the Clutch to get traction and stop wheelspin off the line!

From Beach Boy's Song Shut Down
My Stingray is light the slicks are startin' to spin
But the four-thirteen's really diggin' in
Gotta be cool now power shift here we go
Superstock Dodge is windin' out and low
But my fuel injected Stingray's really startin' to go
To get the traction I'm ridin' the clutch
My pressure plate's burnin' that machine's too much

 

In my experience, at the drag strip only and not having traction issues, I have tried all variants of launching and I have datalogged them All. Using launch control is superior to anything else, followed by the footbrake which I believe is around 1800 rpm and then the the plain stab. The DCT is essentially a manual trans but the ecu does not allow a big dump without killing power first to preserve its parts. On the street with street tires may be different and I have no experience there.

 

So if you have tried the rapid exit procedure in a C8 at the drag strip, can you elaborate on what happened then. I have been asking about it in other threads but no one has said they tried it. I have been assuming that since it is a procedure in the manual, then it probably is not a hard clutch dump, but rather an ecu controlled clutch engagement that also modulates engine power to prevent damage. Some have claimed its to be used to spin the ties to warm them up, but the manual does not say that.

 

Launch Control is logically the fastest considering GM’s Chief Corvette Engineer, Ed Piatek statement: “We found that during very aggressive launches we can drive torque through both shafts/clutches simultaneously which improves the 0 to 60 times.”

SIDEBAR
Perhaps I'm reading more into the words Piatek used, "WE FOUND" but I was very surprised at that statement when a DCT MUST disengage one clutch before engaging the other- or so I thought! His statement makes me reflect on what the R&D Lab I managed (totally different field) would do if given the assignment to define the minimum time before one clutch was engaged after one disengaged.

Would set up the DCT in the Lab with a dyno measuring output torque and powered by a mensurable controllable power source. Then control the shifts and clutch engagements while changing the timing in millisecond steps! There are delays in the hydraulic circuit timing, valve and clutch actuator activation etc. So not too surprising that we might get close to zero planed dely.

But would not have anticipated we could actually engage the 2nd clutch before disengaging the 1st! However would run the test until something broke! Then depending on what it was make the part beefier of say we reached the minimum time.

Perhaps a surprise they could go past zero! They have not given details and things like the gear cluster shaft having torsional defection, slippage of the triple synchro cones etc would cause a delay in activation, perhaps deferent than deactivation.

Some day GM may write an SAE technical paper and give more details. But for now it is what is creating the very fast 0 to 60 times. I do recall reading it operates in 1st and 2nd, which would be logical as a Z51 shifts at redline in 1st at ~35 mph and out of 2nd at 60 mph.

 

Looking at the manual's description of rapid exit, I think this video has an example of it.
Although he does it in the sport mode with traction control turned off, he his not using Launch Control.
It's at the first part of the video, then skip to 7:30 and watch from there to see how he set it up.

 

3 drivers of C8s that I know, have ALL had transmission issues. They all had 1 thing in common, they all launched with paddle shifters. One guy had catastrophic failure, one had leaking fluid, and one had grinding gear sounds. One is trying to Lemon out the C8. Do not launch with paddles. And as soon as you tell the SA your details of why your at the dealership, your done.

 

Here’s a rapid exit with drag radials

 

Interesting. The 2024 now goes a step beyond the rapid exit description in the earlier manuals (that already seem to legitimize the rapid exist approach). In the 2024 Manual there is an entire paragraph on Manual Launch Control. It sound just like rapid exist, except for an extra step of releasing one paddle, which then initiates the Manual Launch Mode, to be distinguished from the rapid exit, described on the same page.

 

^^^^^
Don't see how it's as tough on the DCT as using Launch Control? Left foot hard on brake, right foot to the floor, engine goes to 3500 rpm and the 1st gear clutch is slipping! In fact, both clothes are engaged simultaneously for perhaps up to 50 milliseconds on the 1st/2nd shift reducing 0 to 60 times.

I was constantly achieving 2.5 seconds just lifting my foot from the brake while simultaneously going to WOT. Best I got was 2.4 seconds. With Launch Control was able to achieve 2.1 second, all other conditions optimized. Note those are the GM Dash Test were the number displayed has drag strip rollout subtracted, which could be ~0.3 seconds.

 

Well I've only gone 1 time to the 1/4 mile drag races in my C8
My experience was this
I was able to make 5 passes in qualifying and this is what happened
Remember most drag races are "Dial In " meaning the way to win a race it takes consistency !!!!! Especially when there were over 50 cars in that class (11.0 and slower )
The Launch control my 0-60 times in Sport Mode were almost identical every pass 2.9 to 2.7 (TC and TCS OFF)

But without launch control it and just flooring it both with TC/TCS ON and then OFF it was not only SLOWER from 0-60 But it was inconsistent !! Anywhere from 3.7 to 3.2
So I chose using launch control in eliminations
Only thing I did not test was tire pressures We settled on like 28 PSI But looking back I think It needed a little bit of tire spin to keep the RPM's UP and not Bog and maybe 30 PSI would have been just a tenth quicker
My car is a BASE Model NON Z51--- but with my aftermarket exhaust and CAI and Pedal Commander I am equal to a Z51 and did not spend the what 10K extra for it
Exhaust and CAI and Commander was less than $2500

PS: we finished 4th out of a 50 car line up and this was my 1st C8 drag race ------- racing guys that go to a race every weekend !!! (lost in the semi's by .076 ) Dam !!!