RKCRLR

There aren't any hydraulic lifters in the C8 Z06 (uses shims for lash adjustment) and there doesn't appear to be any room to incorporate anything like AFM between the cam and lift fingers.

JerryU

There are no hydraulic lifters to deactivate! Would have to design a completely different system (read post # 58, it's not simple!

There won't be many Z06's so the 8% increased fuel economy now being required by an administration 2024 to 2026 versus the 1.5% that had been in place so it won't be that critical in meeting the Corvette Family average. Same with the Zora. Demand easilly controlled with price!

THX_ZORA

another plus for running manual mode at all times for me. I don't have to worry about whether V8-V4-V8 is fool-proof or not. I personally don't like the idea of dropping 4 cylinders, then activating them, et cetera, regardless of the mechanics behind how it works. I'll gladly take the MPG hit, plus my car is rarely on interstates/running at consistent speeds for any period of time anyway

Footsam

My 2017 Stingray had two DSA failures and in between had the front bearing migrate out, all in first 7000 miles. Installed Range AFM disabler after last DSA installed and never had another problem when I parted with the car at 34,000 miles.

Halfmoon378

I doubt that the DCT likes the power inputs changing either? Chevy can keep the 4 cyl. mode as far as I'm concerned. By the way, the AFM was left off the ZO6. If it's so great, why did they eliminate it?

JerryU

A few failures doesn't constitutes a general problem. With over 150,000 C7s built don't recall it was a "significant issue," at least as posted on the forum when I had my Two C7s for ~7 years.

However understand your concern and empathize with the problem you had. However like when your neighbor is out of work it's a sign of a recession but when you are it's a depression! All relative, sorry for your issue BUT installing a "disabler" may have been a coincidence not the reason for no further failures..

JerryU

See post # 62 as the reason the Z06 does not have it!

PS: It's NOT a power level input change, it's how it's achieved. It only occurs at low power so no big deal for the DCT. I'm sure it doesn't like my aggressive braking from ~70 mph when I leave the highway to turn into our rural road. In Z Mode Powertrain set to Track (where I often drive) it downshifts from 6th to 5th to 4th in the blink of an eye as I brake aggressively prior to the turn! There is often heavy traffic with folks on that 4 lane divided highway going to and leaving Myrtle Beach and I don't want that line of traffic behind me to have to break excessively!

SIDEBAR
GM has done a great job over the years getting the small block Chevy to produce 495 hp AND meet tougher EPA Requirements. Heck when I was ready to get my 1st Vette in 1974 the max power in a 350 cid small block was ~200 with the new EPA requirements that year. The 454 BB Vette only had 270 hp with less restrictive EPA requirements than today.

It's getting tougher as the current administration has announced they are implementing an 8% improvement in mpg requirement from current 1.5%. Get ready for not just V4, but Start/Start and probably the E Ray Hybrid system in most Vettes! Hell of a lot better IMO than EV's the Zealots are pushing!

The World is changing and if you haven't noticed no one is really concerned what high hp sports car folks want! Nope can't just pay money and pollute the World - like it or not!

HERE IS A QUICK SUMMARY OF WHAT IS COMMING:The current administration is reversing the prior administration's loosening of vehicle emissions rules with a plan to boost efficiency 10% from the 2023 model year and aiming for a fleet average of 52 miles per gallon by 2026.

The EPA proposal also calls for a near 5% stringency increase in each model year from 2024 through 2026.

loyalsince72

Obviously, you don't live in or near mountains. My C8 Z51 tends to go into 4 cylinder mode at 30 mph in fourth gear climbing hills. Since the Range is not available I put it in manual mode when I'm in the hills in town. My C7 GS has a range and I never have to think about it. I LOVE IT.

JerryU

First like all my DD's for 62 years my 2017 Grand Sport was a standard shift. So never use ECO and therefore no V4. It fact with a standard shift you can feel it going in. I often drive my C8 in Z-Mode Power set to Track. Don't need any "Range Device." It also won't even use 7th or 8th. In my rural area I'm usually under 65 mph as it's a 55 mph limit it does not even go into 6th. Don't have to deal with it downshifting gears.

Heck 4th gear is a 0.88:1 overdrive and 5th, where I most drive is 0.66:1. Back in the day a "slushbox" with OD was typically 0.70:1 OD ratio. Heck 8th is 0.33:1 OD ratio! Great for GM to get a higher EPA mpg reading in that test that probably has the Vette using <75 hp! That's all that is needed for City and Highway cycle.

That said, when I use MY-Mode I have set to Sport (never use Touring) it does use all gears. The V8 to V4 is seamless. As they did with the slushbox in C7s they slip the clutches slightly so you can't tell.

If I had hills would be in Z-Mode Power set to Track all the time. I used Manual Mode for a month getting over every DD being a standard shift. But at the end of the rural road I live on is a stop sign and a 4-lane divided highway. Often heavy traffic going to and coming from Myrtle Beach. To merge I accelerate rapidly while making that 90-degree turn. With the wheel turned and 1st gear reaching redline at 34 mph in the blink of an eye the upshift paddle is out of position to pull. Hit the rev limiter several times. No fun with the car feeling like it hit a brick wall with ~70 mph traffic coming up fast behind! In Z-Mode Power set to Track it shifts just before redline! Been doing that for 2 1/2 years!

BJ67

I wonder if I unplug the oil temp sensor/sender unit if I would make V4 mode not come on.

BJ67

Because V4 mode sucks.

BJ67

Cannot wait until the tuners can get into the ECM.

https://www.youtube.com/watch?utm_so...ature=youtu.be

Michael A

I've driven cars where the cylinder deactivation is subtle but noticeable. I just drove my C8 over 180 miles yesterday through all types of traffic. I honestly forgot it even had AFM.

MarkMeHopeful

If your C8 goes into V4 mode when climbing even a slight hill then there is something wrong with it. You should take it to the dealer and have it fixed. Mine won't enter V4 mode with even the slightest extra pressure on the throttle (which surely you have to maintain speed) and kicks out when going from flat highway to a slight rise.

68/70Vette

I read many of all of these posts. Two things I noted:
(1) During transitions from V8 to V4 and V4 to V8, the clutches in the DCT slip to prevent a powertrain induced jolt the driver would otherwise notice
(2) In V4, the engine operates in V4 mode for 10 minutes, transitions to V8 mode for one minute, and then transitions back to V4 for another 10 minutes.

This in turn leads to thoughts that......
(1) over long turn use, the V8/V4/V8... transitions will be element of clutch wear-out degradation. A small wear-out degradation per transition, but in the aggregate significant?
(2) the engine is not to operate in V4 for more than 10 minutes, without a 1 minute operation in V8. To me this implies there is something harmful in continuous V4 operation.

But not to castigate the Corvette engineering team. All of this sophisticated complicated technology for this and many other things means that they can present this car for sale and meet all of the government mandates. It's accept this stuff, otherwise it won't be possible to present the car for sale.
........................................ .
Will the V8/V4/V8 transitions result eventually in the need for clutch replacement? With the automatic engine stop/start/stop transitions lead to premature starter motor brush wear out? Just keep in mind that the cost savings in gasoline consumption, will be obliterated by the cost of clutch replacement or starter motor replacement? Or maybe the cost to repair the automatic transition functions themselves if/when they fail.

If we don't like things like this, what about writing to our Representative or Senators in Congress? This will be a moot activity. Most of these federal intrusions into our lives do not come from Congress, but rather from unelected government bureaucrats.

JerryU

You'll get a CEL! Just use Z-Mode Power set to Track! If MRC can set Ride to whatever. If not, has no effect of ride.

JerryU

Wrong conjecture! Have to understand what is happening before "guessing" the reasons for why it's being done!

• The 1st gear clutch slips whenever you're taking off and driving below ~4 mph. Has to or the engine would stall. It also slips slightly when stopped per the Executive Corvette Chief Engineer Tadge Juechter. He also says it is designed to do that and no harm.
• Yep it will switch back to V8 periodically but nothing wrong! It's to maintain combustion pressure in shut off cylinders.

SIDEBAR
For those interested this is a "VERY condensed version" of how Cylinder Deactivation works"

• To provide maximum fuel economy under light load driving conditions, the engine control module (ECM) will command the cylinder deactivation.
• When cylinder deactivation is commanded, the ECM will determine what cylinder is firing and begin deactivation on the next closest deactivated cylinder in firing order sequence.
• Cylinder deactivation is accomplished by not allowing the intake and exhaust valves to open on the selected cylinders by using special valve lifters.
• Cylinder deactivation is timed so that the cylinder is on an intake event.
• By deactivating the exhaust valve first, this allows the capture of a burnt air/fuel charge, or exhaust gas charge, in the combustion chamber. The capture of exhaust gases in the combustion chamber contributes to a reduction in oil consumption, noise and vibration levels, and exhaust emissions when operating in V4 mode cylinder deactivation mode.
• Switching between V8 and V4 modes is accomplished in less than 250 milliseconds, making the transitions seamless and transparent to the vehicle operator.

Red Mist Rulz

It might, but it would probably also throw a code, and maybe trigger limp mode, since the car won't know why the oil temp is so low.

Andybump

Jerry,
The microslip feature is documented in the "MidEngine Revolution" book on page 182. It says " The new dual-clutch transmission, however, has less inherent capability [ than a torque converter to mask the engine vibration [that results when switching between four and eight-cylinder operation] which is why cylinder deactivation technology has so rarely been used on a car with a dual-clutch transmission. The C8 engineers were able to marry these two technologies [referring to torque converter capability to absorb the vibration] in the new Corvette, however, by putting some micro-slip into the clutch control of the DCT." In addition to that there is also a "pendulum damper" documented in several articles about the TREMEC transmission as follows:"Connecting the LT2 engine’s crankshaft to the TR-9080’s clutch basket is the responsibility of a flywheel carrying the starter ring gear and a centrifugal pendulum damper that’s needed to quell torsional vibrations erupting during the engine’s migration between V4 and V8 firing modes (a fuel efficiency improver)."

I am curious about your explanation for the v4 duty cycle. Where is that documented? While it makes sense that might be to compensate for leak-down of the captured spent charge (which is necessary for the "spring effect" they cite", I have never see that written anywhere. If that is the only reason, it seems like it would only need to open and shut for 1 cycle to recapture a charge, rather than 1 minute. I previously speculated (but its conjecture and no proof) that it was related to making sure the the engine block was evenly heated. I am also surprised that the captured, spent charge would actually last for 10 minutes.

Red Mist Rulz

There are literally 10s of millions of miles on small block V8s with AFM. Issues are few and far between once you get past the first generation of the technology. Search the web and you'll find lots of posts saying their engine had a lifter failure and blaming it on AFM. But I had a lifter failure on a 1966 Dodge, and no one had even thought about cylinder deactivation. Sometimes hydraulic lifters fail, in all kinds of engines. I suspect the 10 minute / 1 minute cycle has multiple reasons, including leak-down, maintaining even heat distribution and probably other things, but I haven't seen any documentation of it.

As for clutch wear, it's really too early to know. But a little clutch slippage in a multi-plate wet clutch is going to cause a lot less wear than on a traditional dry clutch. GM says they expect the clutches to last the life of the car in normal use. Hopefully they're right. I'm not really worried about it, personally. There are reasons, perhaps, to worry about the DCT, but I don't think AFM is one of them. My opinion.