Silberschnell

Have a new C7 auto trans, and noticed a pinging sound at low RPMs when cruising at 40 mph+ and lightly giving it gas. Seems to occur mostly in V4 mode. Dealer said it is normal, but if don't like it use the manual trans mode with paddles. I see there are devices that plug into OBD port to defeat V4 mode- will this be better for engine longevity?

NSC5

I don't like V4 mode, particularly with the automatic. For longevity of the torque converter clutch I would use either the Range module or manual mode.

I have a Z06 (with A8) and never let it enter V4 mode. I have never heard any knocking but I use only 93 octane fuel. You might also try a different fuel station but I would stay out of V4 mode.

davepl

I doubt it's specifically related to V4 mode, though that could aggravate it just by virtue of those cylinders experiencing additional load. Note also, for example, you're more likely to ping going uphill. Load matters.

If you mean a couple of seconds of ping that then resolves and doesn't come back during the drive, I'd say that's (a) normal, (b) expected, and (c) good. If you mean it does it a lot or does it -every- time you tip into the throttle, then that's none of those things and it should be looked at (IMHO).

I'd try better gas or a (real) octane concentrate before I started disabling AFM. I have AFM, mine's an auto, and other than the rumble noise I have no knowledge of or problem with mine going into V4 mode. Others are more sensitive about it.

Maxie2U

I bought the Range Technology AFM Disabler even before my C7 was delivered. I bought a Sports Car not a 4 cylinder Honda Civic so wanted to stop mine from going into V4 mode.

Owned it a year and a half and it's never gone into V4 mode

The other major reason to avoid V4 mode is the excessive vibration and some even reported torque converter issues related to V4 mode.

JoeHat

No way, i drive mine in Tour mode 75% of the time. No pinging. I don't have NPP so i can barely hear it transitioning. BUT, i too recently had a A8 scare. Check out my post from two days ago. I have the AFM disabler but haven't used it much. Think I'm going to start!

Silberschnell

Thanks - have tried different fuels but all the same, probably the 91 octane CA gas. Will use manual mode and get the Range module!

Bill Dearborn

I have an M7 but run in Eco mode a lot with the transmission in 6th gear so engine is in V4 mode for longer periods of time. I don't notice any pinging. I really don't see why it would ping even with 91 or even 87 octane gas. When the engine is in V4 mode it is barely running. As soon as there is any strain it changes to V8 mode. That is why I run in 6th gear Vs 7th when on the highway. At 70 mph in 7th the engine won't go into V4 mode unless the car is on perfectly flat ground or a downslope. Any upslope even if you can't see it will throw it into V8 mode. In 6th it has enough torque to on slight upgrades which actually improves gas mileage over 7th gear. The only thing I notice about V4 mode is the exhaust gets a lot quieter when it is on.

I am not sure why people don't like it since if you want more sports car power all you have to do is tickle the throttle and you are in V8 mode. It doesn't take much of a change in throttle pressure to switch it.

Bill

NSC5

I would generally agree with you with the M7 transmission but with the A8 it seems quite problematic. Modulating the torque converter clutch to reduce vibration in V4 mode appears to not work well over the long run. To date GM has released at least three torque converter revisions and now a new fluid to try to address the issues faced with the A8 concerning excessive RPM fluctuation and shudder while cruising at a steady state in V4 mode. I suspect most A8 owners would rather have additional vibration in V4 mode via a locked converter clutch rather than transmission issues.

davepl

And yet I'm one of those A8 guys that never notices it. It either must vary per car or our tolerance for it varies wildly I guess.

Would I turn it off if I could through the DIC? You bet, just because I doubt it picks up much economy and I don't really care for the rumble sound. But I can't feel it. No converter shudder, no clutch locking and unlocking that I can tell. Seamless, really.

djnice

Dave, how many miles on your car? I would like to know if Z06 owners are getting relatively high miles on the Auto trans with V4 active.

davepl

Mine's only got maybe 6,000 miles. We've seen other high mileage cars on the forum (50k, 77k, etc). But I'm sure not one of them!

I drive about 10,000 miles a year and if it's a good year I'll get half of that in the Z.

NSC5

It would be interesting to see how the "shudder tendency" occurs across the C7 line. The base C7 and presumably Z51 (at least the original) should have the most active AFM system and will spend a greater percentage of time in AFM mode. These cars have the higher compression LT1, a steel torque tube (better absorbs NVH from V4 mode), AFM noise control valves (although deleted on later production Z51 I believe due to failure on track), and a higher numeric axle ratio for the Z51 which would probably allow AFM to activate at a slightly lower road speed per gear.

The Z06 has a carbon fiber torque tube and no AFM noise control valves so AFM activation is more noticeable compared to the Stingray and presumably it is not programmed to become active in situations where these differences from the base car would make it highly noticeable. The LT4 has a lower compression ratio so efficiency is a little lower while the larger tires and greater air resistance mean more engine power is needed to maintain the same road speed compared to a Stingray; together these are going to reduce the percentage of time that AFM can be active under given driving conditions.

The GS should be somewhere in between the Z06 and regular Stingray in terms of AFM likelihood of activation. It has the LT1 engine but I believe it has a carbon fiber torque tube and no AFM noise valves like the Z06 so it may be programmed to be less active than the regular Stingray. It also has the greater air resistance of the wide body and the greater rolling resistance of the wide Z06 size tires but this is somewhat offset by a higher numeric rear axle ratio than the Z06.

So doing a long term average by grouping I would expect a base C7 including the Z51 to have increased likelihood of early torque converter issues while the Z06 will be at the other end of the time/miles distribution and the GS will be somewhere between the two. Obviously driving style has a lot to do with it and some drivers will be in the road speed and power range that often activates V4 while others are rarely in that window.

Steve Garrett

OP, welcome to CorvetteForum.

This is just a thought, but I only use my Active Cylinder Deactivation if I'm on the highway. I've got to think that city driving in V4 mode would not work as well or be as effective.

Bill Dearborn

And I use my Z06 M7 in Eco Mode all the time. With the exhaust in stealth mode I can't tell the difference between V4 and V8 modes. In track mode the exhaust gets very quiet when the engine switches to V4 mode and loud when it switches back to V8 mode.

When the car is driven in traffic using a light foot and running in 4th, 5th and 6th Eco mode definitely gives you noticeably better gas mileage. I try to be in 4th gear before the speed goes above the 20s.

Bill

AWOL

Why I wonder?
It does not matter if you are on the highway or in town, the same parameters are used to tell the engine to go into 4 cylinder mode or 8 cylinder mode.

fnbrowning

I'm a 2016 Base Stingray with A8 also.
I'm another one of those A8 guys that never notices it. It must either vary per car or our tolerance for it varies wildly I guess.

I can't feel it. No converter shudder, no clutch locking and unlocking that I can tell. Really seamless for me also.

taylosw

I have a Z06 is it actually bad and/or detrimental for my car to go into V 4 mode ? I hear a lot of horror stories !

Should I invest in the AFM thing ?

NSC5

This link provides a little history on GM's use of triple C (AKA capacity coupled clutch). From the shudder and RPM fluctuation issues and ensuing multiple revisions of the new "squashed" converter which allows the 8L90 fit the same space as the prior 6L80 and 6L90 it appears the current clutch material doesn't like the extreme duty cycle when in AFM mode.

https://www.transtar1.com/TranstarIn...TLT-TC-035.pdf

Your Z06 doesn't go into V4 mode nearly as frequently as the LT1 equipped models so it may go a very long time without issue but that wasn't I risk I was willing to take with my Z06. For those who expect to keep their C7 to very high miles then you will experience different wear characteristics between the "normal" cylinders and those shut off in V4 mode. Delphi and some of the Japanese firms are testing systems which randomize shutoff across all cylinders to avoid this issue.

taylosw

Definitely plan on keeping this cool car for a long time so it looks like I'll order one tonight

NSC5

Probably coming soon to an engine near you and maybe it will overcome some of the issues (NVH, differential wear pattern) of the current AFM system: http://www.delphi.com/manufacturers/...ivation-system