Nelno

I've seen one reference to GM improving the A8 shift response times for the C7 ZR1.

Is this true? And if so, does anyone know if this is a software vs. hardware upgrade that might be available for other C7 models / years, or incorporated into 2018 Z06's?

If there's one thing I'm not overly pleased with on the C7Z, it's the shift lag. I know it's faster in Track, at full throttle, and in Performance Shift Mode, and I've read Tadge's points about it, but when I'm not full on the throttle (which, c'mon... it ain't easy to do that all the time in a Z06), I find myself wishing it would take my shift suggestions more seriously!

davepl

I always ask because I've never understood:

Who cares how fast it shifts at light throttle?

I have an old SMG car that you can force to bang-shift at 2000rpm and part throttle if you WANT, but I certainly never DO that. So I don't miss it in the Vette, and don't understand why anyone cares.

It shifts lightning-quick under load in anger when it matters, so I'm really lost as to why people care about part-throttle light load stuff.

I'm not arguing with you - if that's what people want, that's what people want. I just don't get it, myself.

Internets_Ninja

Do you mean shift lag when using the paddles? Or the actual transmission shifting the gears?

Nelno

I meant shift lag when using the paddles. I know the transmission shifting is tunable and it seems fast when it actually shifts.

ashmostro

I drove 18 and 19 A8's back to back against the M7 I recently bought and was very underwhelmed by the shift reaction times. I am one that still wants an immediate response from my command regardless of what rpm or level of anger I'm driving at. Otherwise I have no use for paddles.

If you're like that too, I wouldn't recommend the newer A8's.

Motors5

davepl

No, I fully grant that pulling a paddle at light load and mid rpm yields a slow shift. I just argue that it SHOULD do that, and don't see any reason why I'd want a crisp part throttle, light load upshift!

Suffice to say, however, if you believe that's what a trans should do, our A8 doesn't do it.

ashmostro

Yep, philosophical difference for sure. I'm aware of the common position here that a light throttle up shift doesn't need to be crisp. I'm just not in that camp by a mile. Hence, no A8 for me.

Good thing the M7 is so good!

corvetteflier

The faster you go, the quicker the paddles shifts. However, it works so well in auto I generally leave it in that, but use the paddles while in auto primarily to downshift. Has been working perfectly on my '18 for 2500 miles. Best automatic I've ever driven.

davepl

Gotta ask then - let's say you're out cruising in your M7, about 22 mph, and it's time to casually upshift from 2nd to 3rd.

Do you ever just grab that handle and RIP it as hard and fast as you can, completing that upshift in milliseconds? Like pull off your fastest shift possible for absolutely no reason?

If that's the feature you miss in the A8, do you actually do it in the M7?

Just asking because I'm curious, not judging. I have sticks and autos, and am religious about neither!

ashmostro

So, coming from a DCT in my F80 M3, the use case for me is, When I'm using the paddles, I want to feel in control of the decision making process. The lag, any lag, feels like that decision is being made for me. That's what I dislike.

Yes, I might choose to shift slowly or more aggressively in a manual, but it's my choice, not something thrust upon me.

When I pull a paddle, I expect a shift.

Internets_Ninja

This is definitely true, when you're full throttle driving hard, the paddles respond quicker. There is still a delay but I actually got used to it and learned to anticipate.

Agree 100%. Loved my A8 and now I love my M7. My next car will probably be an auto. I miss things about the A8, but there are parts of the M7 that the A8 will never fulfill. After having owned both there is probably a 60% chance I would buy the auto in my next vette since it would be my daily driver.

davepl

It is. It's saying "WTF? You want a fast shift now at 3000rpm? But the pump is barely running because we're nowhere near where you'd want to shift, but ok... let me spool up some pressure, and... shift!"

That's opposed to the 6200rpm shift where the trans has already prepared 85% of it and all you have to do is so "OK" and it goes "Bang! Done!" because the pressures were up and so on.

And if it comes as a surprise to the transmission, it'll be slow. To which I concede that "The A8 sucks at shifting at the wrong time". If it's when a transmission would be expected to shift (under load near redline) it's quasi-magical for a TC automatic, I think.

ashmostro

I can tell this is a tense subject, so please don't take this as a criticism of another perspective. It is not, and I fully see the validity of your perspective.

This morning as I was driving my DCT-equipped M3 and was using the paddles at moderate RPM the following came to mind: for me (and I'm sure many others) shift reaction time isn't the only factor in influencing the perceived aggression of a shift. I'd even argue it's not the most important factor.

Other behaviors that will vary according to the driving style at the time of the shift request in my DCT include: even-odd clutch overlap, ignition cut and duration, throttle position, timing, fuel cutout. I'm sure there are others that I'm not aware of. The point is at low RPM/throttle position shift requests I still get an immediate shift reaction, but I don't get any of the punch-you-in-the-back clutch overlap. and the ignition does cut out temporarily to allow the engine to spin down faster. All of this contributes to a fast, but unnoticeable shift. On the other hand, when I'm doing WOT upshifts on a racetrack, I get the same fast reaction time, but no comfort-oriented mapping enhancements - the priority is power application. I like the dual nature of this design while not having to compromise on shift reaction time, again for the "connectedness" reasons I stated above *which are purely subjective preferences*.

In summary I feel (again, I admit subjectivity here) I can get the best of both worlds in other automatic transmissions (note I am not the one comparing to manual here) but I cannot get the behavior I want out of the A8 on this platform. I know it's tempting to make the Manual comparison but when I rejected the A8 for my use case, it was due to a comparison to the DCT performance I've acclimated to. As such, I was forced to contemplate the manual transmission as the only other choice but thankfully it was one that I happen to like a lot for *other* reasons than what we've been discussing here.

Does that help clarify where our thinking differs but does not have to be mutually invalidated?

Nelno

I don't think that's a valid comparison, though.

The issue is when you perform the action to shift and the car doesn't do it quickly enough and also does it some seemingly random amount of time later.

A more appropriate comparison would be, you're out in the M7 and you push the clutch in, shift the stick into the new position and release the clutch, and some indeterminate amount of time later the transmission changes to the new gear.

It is the delay between when you, the driver, complete the gear change action and the car actually changes gear that is the issue, and it's exacerbated by the inability to predict how long it will take.

I'm not religious about it either. I bought the auto because it's my daily and I end up driving in traffic a fair bit and... it's faster in a straight line. I'd just like it to be more consistent and faster to respond if possible.

Nelno

It's all subjective really.

I still love my Z06 and wouldn't trade it for anything at this point, but this is something that myself and others wish they could improve.

If they did do it with ZR1's, and that is applicable to previous models, I'm pretty sure a lot of people would choose "more responsive" over "less responsive", whether they really need it or not.

djnice

In the ZR1 reviews that I have seen, they didn't indicate shift quickness was improved.

ashmostro

Another excellent distinction. Well said.

subieworx

Tune it. This is adjustable somewhat in HP Tuners. My current setup drastically improves shift times and response at lower load and rpm over stock.

Nelno

My understanding was that this could reduce the time that the transmission would take to shift at various loads (once it was told by other systems to initiate the shift) but did not have much effect on the time between pulling the lever and when the system told the transmission to shift, and that was where most of the lag was.

The difference may be a subtle one, but I'm assuming the flow is something like this (based on Tadge's response about shift times):

1. Shift lever pulled
2. Some control unit begins planning the shift (this may include both collection of data and telling other ECUs to prepare the system they control for the shift).
3. Same control unit, based on information from other ECUs, decides everything is just right and tells the transmission control unit to shift.
4. Transmission control unit starts a shift, which may be a fast, slow or in between.
5. Transmission actually shifts performs a shift.

My understanding from reading posts about transmission tuning is that it doesn't completely fix the lag, and most likely affects 4 to 5, not 2 to 3.

Do you feel like it actually reduced the lag and (most importantly) the uncertainty after a paddel shift is initiated?