Finally tried out launch for the 1st time the other day, just on a back road. Not ideal, but I wanted to try it. Sport mode, with competitive drive mode enabled.

For whatever reason, it went through 1st, shifted to 2nd, then immediately shifted to 3rd. See attached video.

Any ideas why it would shift into 3rd like this?

 

Repeat it in track mode or in z mode with the transmission set to track mode. You will probably get more of what you expect.

 

Fully floored, I would expect it to run up to red line again in 2nd before shifting to third, even if engine/shift is set to Tour. Any chance you bumped the upshift paddle?

 

Right, that’s what should have happened. I really don’t think I hit the paddle, but I suppose it’s a possibility.

 

Doesn't look you were in Launch Mode! As suggested, put in Track or as I always use Z-Mode set to max power. Need to have foot firmly on brake when at WOT and it will go to 3000 to 3500 rpm before you remove foot from brake.

 

Jerry, I still don't see why it would make any difference - causing the car to abruptly shift from 2nd to 3rd at low rpm while the throttle is floored. I don't do launch control launches, and only once have I ever tried a "rapid exit" from a double paddle declutch. But I have done full throttle starts from a standstill in Tour Drive mode, and it still always waits til the rpm is near redline (6000+ rpm) before it shifts to the next gear.

 

I have done many Launch Controls with my E-Ray Andy. it always goes thru all gears (well the 1st few.) In fact on the 1st to 2nd shift is where it gets it's "extra aggressive launch" powering thru BOTH 1st and 2nd drive shafts.

This is what the former Chief Corvette Engineer (Josh Holder's current position) said around the C8 Launch, just before he and half the Corvette engineers were assigned to work on EVs in ~2020:

• A very interesting comment was made by GM’s Chief Corvette Engineer, Ed Piatek: “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."
• Recent comments from @RedLS6 clarified how that is done. I mentioned in a post must only be for a few milliseconds. He said he had info on other DCT's that do about the same. They can slip both clutches for 100 milliseconds! Thats 0.1 second and a lot with ~400 hp!

Don't know what the OP was doing or why it skipped a gear BUT IMO it was not Launch Control.

 

It was absolutely in Launch mode. For a Z51 car, selecting SPORT drive mode and then pressing the TC button twice will engage Competitive Drive mode; where launch is available.

In the video, you can clearly see my foot is 100% on the brake, and then I quickly stab the throttle to 100% WOT, and the RPMs jump up to 3500 and hold there until I release the brake pedal.

If launch mode wasn't engaged, then the RPMs would not have climbed to 3500 and held there. I believe without launch, the RPMs stay around the 1500 - 2000 range, correct?

1st gear was exactly as I expect, with the system working to keep traction. It shifts to 2nd, then immediately shifts to 3rd. All while my foot was 100% on the throttle and launch mode engaged.

 

Sorry, did not have those details BUT looking at the graph of the run did not look like what I experience. Expect with the slipping clutches 1st to 2nd might look different but 60 mph in 2nd is ~6600 rpm so should shift to 3rd but not until then!

And I agree, before I reached 1500 miles I only made 0 to 60 test runs using the old slushbox automatic approach of foot hard on brake and as soon as I use WOT release brake. I don't recall it getting to even 2000 rpm. BUT I did get rear wheel spin. I was surprised. In fact 1st time it happened had a passenger and lifted quickly. After in in my 2.1 second GM # runs with heated tires heard no audible tire spin.

Try Again. I noticed a video at a drag strip where he got a 60 foot time on 1.57 seconds he bypassed the water and used Sport mode to do a short burnout. He said it mostly cleaned the tires. IMO it was so short there was no heat building. Then he used Track or Z-Mode to Launch. That was with street tires not slicks.

In fact that is where I developed my tires need to be heated (I have the ZER Option Summer tires.) That was March time frame. On the GM Test I was able to get 2.5 seconds (have to add ~0.4 seconds as GM subtracts drag strip roll out as most magazines do when the published 0 to 60 times.)

PS: Yep watched again several times and it was in 3rd at ~43/45 mph. If anything would expect the gear number might be delayed not shown sooner. Appears something happened in that 1st to 2nd shift where they slip both clutches. Wonder if it detects tire spin it jumps to 3rd.

 

No worries, all good .... The graph in the video isn't showing RPM or MPH unfortunately. Ii displays brake pedal pressure, throttle position, and steering angle. I look around Tool Box for a way to try and add RPM to the graph, but apparently it's not that configurable.

I'm guessing I either inadvertently did hit the paddle, or the surface was loose enough where it somehow caused it to jump to 3rd; but if that were the case, I would have expected the RPMs to spike suddenly due to traction loss and that didn't happen (have to watch the video to see what the RPMs are doing).

I do like to short shift a lot when driving around normally. I'll accelerate aggressively with say 80% throttle, but I don't want to rap the RPMs out to ~6k or so when just driving through traffic, so I'll pull the paddle to short shift and leverage the low RPM torque

Maybe I subconsciously hit the paddle? I really don'tthink so, as I had someone in the car with me and we were both focused on seeing how the launch mode would do. I didn't even realize it skipped 2nd until I got home and reviewed the PDR video. At the time of the experience, I said something like "Hmm, TC is off but it seems stabilitrak still interfered as it seemed to bog down from 1st to 2nd". It was only when I got home and reviewed the PDR video that I noticed it shifted into 3rd right after engaging 2nd.

 

Looking at my table of gear/rpm/speed for Z51/E-Ray gearing: 1st gear red line is ~36 mph. It shows 3rd gear at ~45 mph is only ~3500 rpm. So my guess is, if it detects wheel spin perhaps going into or in 2nd with the clutch slipping it goes to 3rd. It's protecting itself from possible wheel hop!

 

This is what I was thinking too. Some Stabilitrak algorithm must have detected something which caused it to up-shift as a protective or avoidance measure. Either that, or I hit the paddle by mistake (still doubt this though) ...

When I have some time, I'll try it again in competitive driving mode, as well as in track mode (with PTM).

I'll bet the eRay's AWD setup makes for some FANTASTIC launches! The wife's AWD Durango (supercharged 5.7 Hemi) certainly jumps off the line without any wheel spin drama (maybe a little chirp, but that's it). For a 6k lb vehicle, it gets to 60 in 4.59 seconds now (6.2 seconds before I added the supercharger).

The eRay is officially rated at what, 2.5 seconds vs. the Stingray's 2.9 (or 2.8 depending on what spec you believe)? That's a significant difference for only 200 extra HP with an extra 200 - 300 lbs of weight. The AWD most certainly is providing some serious benefit here.

Stingray curb weight: 3535 - 3647
eRay curb weight: 3774 - 4000

 

Yep even with the extra weight the Launch is hard to understand unless you feel it!

I retired in 2000 (well semi, still have a part time Internet business) and bult what I had always thought about. A Big Block set back in a tubbed chassis mostly for acceleration. It's a 34 Sedan body to allow the set-back engine (and bucket seats) on a very rigid TCI 4 bar link rear suspicion chassis. Coilovers and disk brakes in all 4 corners. It has 53% of it's 3000 lb static weight on the rear 16.5 section width (420 metric) Mickey Thompson tires. With long tube headers and a Holley 850 double pumper It's about 525 hp with gobs of torque. The Launch with a 2600 rpm stall converter is super. BUT measured with my G-Tech Pro does not come close to the E-Ray! Tough to match the added FWD traction!

 

What is a WOT?

 

wide open throttle

 

Thanks

 

Now you're making me want to retire early :P

I'm also wondering if I should have waited a bit longer to buy a C8, for eRay prices to come down a bit more as they age and ones with higher mileage come into the market LOL! Although I do love the driving experience of a RWD platform with power ...

Does the eRay have a drive mode which allows a rear bias, so you can do fishtails, donuts, drifting, etc ...? I saw the article about GM patenting active aero to develop a "drift" drive mode, and it made me wonder if the eRay and/or ZR1X might have some ability to disable the front drive line somehow?