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Like title says does z06 have the exhaust AFM valves. I have a post where a lot of us with stingrays are having a warble type sound. Dealer is telling us it is coming from the AFM valves and one guy said the Z06 doesn't have the valves. They are supposed to quieten the exhaust when you go from 4-8 or 8-4 but ours are making a strange warble sound around 1500 RPM. Dealer and GM thinks they are a bad batch of vales and hopefully a recall will come soon. So question is does the Z06 have the valves and if not why, does the Z06 not have the 4-8 feature? Thanks
No. Supposedly the exhaust AFM valves restricts the exhaust flow in 4v mode thereby increasing the velocity and keeping the Corvette from sounding like a Honda. The supercharged Z06 doesn't have the issue.
I expect the heat issues that killed the AFM exhaust restriction valves in some of the tracked Z51 C7s would have shown up very commonly with the LT4 equipped Z06 driven in a variety of conditions. AFM doesn't activate as much in the Z06, probably due to the slightly lower compression engine and greater aero and tire drag compared to the regular Stingray, so it can make do with the NPP valves providing some sound modification in V4 mode. Since every Z06 has NPP unlike some of the other models that probably also drove the decision.
I'm the guy in that thread who made the comment that the Z doesn't have the AFM valves.
It doesn't. At least mine doesn't, and I'm sure it's not a special unit.
I can see where the question may come from.
I can't look at my car right now and I don't recall seeing them the last time I was under there.
But the GM parts diagram does show the valve there.
Granted this is a combined diagram for the Stingray, Stingray NPP and Z06 that breaks out different part numbers for the 3 systems in the notes. However the illustrated view isn't clear if the valve is omitted for the Z06. Initially I thought this may have been the NPP valve but based on the location in the schematic before the muffler it should not be.
To make the matter more muggy if you dig deeper into the valve and the part number. The info about the part specifically states it fits 2015 and 2016 Z06's.
Just wanted to point this out to show that there is a legitimate reason for the question and possibly conflicting answers.
Might they be there on Z06 M7's as opposed to Z06 A8's or vis versa?
I was helping to install an Akrapovic exhaust that kept making mention of two sets of valves, which confused us. The instructions expected/allowed for both NPP and AFM valves.
At the time I did some research to find out what was doing on with the instructions and the best I could determine then was that some of the pre-production Zs, and perhaps the early production cars, had the extra set of valves.
Early on into the run they got rid of them, and the Z hasn't had them since at least very early in the 2015 run.
Can't prove any of it, but that's what I concluded.
Mine's an M7 and it doesn't have any. I don't think any of the Zs have them.
And I wasn't knocking the guy asking the question - certainly a fair question to raise. Particularly in light of the trouble some of the Stingray owners seem to be having with these.
Mine's an M7 and it doesn't have any. I don't think any of the Zs have them.
And I wasn't knocking the guy asking the question - certainly a fair question to raise. Particularly in light of the trouble some of the Stingray owners seem to be having with these.
I think most folks on the forum who have seen your past post know you weren't knocking the guy.
I certainly didn't mean for my post to come across as insinuating that.
Apologies to all if it did.
Thanks for the information. I have an early production M7 and will report back as soon as able.
Thanks for the info guys, so does the z not have the 4/8 mode? Since the afm valves are there to help with sound in 4 mode and u guys say the z doesn't have them i assume the z doesn't have the 4 mode. Thanks again gentlemen.
Thanks for the info guys, so does the z not have the 4/8 mode? Since the afm valves are there to help with sound in 4 mode and u guys say the z doesn't have them i assume the z doesn't have the 4 mode. Thanks again gentlemen.
Yeah it has 4/8 mode. I've never used it - mine's an M7 - but the A8 guys that have and have also had Stingrays report that the Z spends much less time in V4 mode than the Stingray. Seems the operational parameters of it on the Z may be narrower (but one of the A8 owners may be able to provide more insight on that).
The A8 equipped Z06 doesn't go into V4 mode nearly as often as the regular Stingray but it still uses it which is why mine has a Range AFM defeat module plugged into the OBD port via an extension cable with power switch. Otherwise you can leave the A8 set to manual mode and use the paddles like I did on the drive home from the NCM.
Yeah it has 4/8 mode. I've never used it - mine's an M7 - but the A8 guys that have and have also had Stingrays report that the Z spends much less time in V4 mode than the Stingray. Seems the operational parameters of it on the Z may be narrower (but one of the A8 owners may be able to provide more insight on that).
You say "I've never used it" - just wondering why.
I'm all for increasing fuel economy by a couple mpg. I'd "use it" more often when highway cruising if I could, but I've got an M7 and AFM is only in operation if I go into ECO mode, which I don't mind doing when cruising - but I find it very hard to "use it"!!
I understand with the A8 that AFM will be active in all modes unless you put the transmission into Manual to use the paddles.
First of all - how do you know if it's working or not?? The only way I know of is to select "Info" for your instrument display, then scroll to the display in the window below where you can see the small "V8" (or "V4" when in the 4-cylinder mode). I pulled the pics below off the internet, and they must be from an A8 because they're in "Tour" (and the gear selection shows a "P" and "D"), and an M7 will only go into "V4" in "Eco":
Second - I've tried to get it to go into "V4" mode, but it generally just will not do it when I'm cruising. I've tried ECO while going down the interstate at 70 or so in 7th gear, but when I look at the display in the picture above it's always "V8". Even when cruising at 55 mph on a local highway it just won't go into V4 while I'm in 7th.
Third - While cruising down the highway in 7th and "V8", I have got it to go into "V4" by downshifting to 6th or 5th. Butt....the "Instant Fuel Econ" went DOWN by a couple mpg!?!?!?
So....is there any other way to know if you're in "V4" mode? And I thought "V4" was designed to INCREASE mpg, but all I get is worse mpg if I get it to go to V4 by downshifting.
I think it's a stupid and useless system!! However, if it saved me $1800 or so in gas guzzler tax I'm all for it, same as the 1->4 shift that never comes into play either.
On a 2,500 mile road trip, a friend's 2015 Z06(one of the early A8's built) only went into v4 operation when he let off the gas going downhill. He was running eco mode.
You say "I've never used it" - just wondering why.
I'm all for increasing fuel economy by a couple mpg. I'd "use it" more often when highway cruising if I could, but I've got an M7 and AFM is only in operation if I go into ECO mode, which I don't mind doing when cruising - but I find it very hard to "use it"!!
I understand with the A8 that AFM will be active in all modes unless you put the transmission into Manual to use the paddles.
First of all - how do you know if it's working or not?? The only way I know of is to select "Info" for your instrument display, then scroll to the display in the window below where you can see the small "V8" (or "V4" when in the 4-cylinder mode). I pulled the pics below off the internet, and they must be from an A8 because they're in "Tour" (and the gear selection shows a "P" and "D"), and an M7 will only go into "V4" in "Eco":
Second - I've tried to get it to go into "V4" mode, but it generally just will not do it when I'm cruising. I've tried ECO while going down the interstate at 70 or so in 7th gear, but when I look at the display in the picture above it's always "V8". Even when cruising at 55 mph on a local highway it just won't go into V4 while I'm in 7th.
Third - While cruising down the highway in 7th and "V8", I have got it to go into "V4" by downshifting to 6th or 5th. Butt....the "Instant Fuel Econ" went DOWN by a couple mpg!?!?!?
So....is there any other way to know if you're in "V4" mode? And I thought "V4" was designed to INCREASE mpg, but all I get is worse mpg if I get it to go to V4 by downshifting.
I think it's a stupid and useless system!! However, if it saved me $1800 or so in gas guzzler tax I'm all for it, same as the 1->4 shift that never comes into play either.
.
BEZ,
I've never used it primarily because my Z is my 3rd fun car in my stable - so not a daily driver. A minor increase in mpg on that rig for me is a de minimus benefit. For others it might make more sense. That combined with reports from other M7 owners that it doesn't really meaningfully increase mpg on the M7, and the added stress on the timing chain and reports of failures of the AFM lifters due to malfunction shifting in/out of operation, leads me to simply not use. I frankly don't ever even think about it - other than reading threads like this.
As a result, I've simply never had my car in eco mode. Doubt I ever will. For others it may makes more sense to give it a try and see if results in any benefit for them. For me, it's pretty much a non-issue. And my car has the 1-4 tuned out, so I left that in my rear view mirror as well.
I've never used it primarily because my Z is my 3rd fun car in my stable - so not a daily driver. A minor increase in mpg on that rig for me is a de minimus benefit. For others it might make more sense. That combined with reports from other M7 owners that it doesn't really meaningfully increase mpg on the M7, and the added stress on the timing chain and reports of failures of the AFM lifters due to malfunction shifting in/out of operation, leads me to simply not use. I frankly don't ever even think about it - other than reading threads like this.
As a result, I've simply never had my car in eco mode. Doubt I ever will. For others it may makes more sense to give it a try and see if results in any benefit for them. For me, it's pretty much a non-issue. And my car has the 1-4 tuned out, so I left that in my rear view mirror as well.
Even though you have the AFM tuned out, you still have the disadvantage of retaining the hardware. The lifters of the four AFM cylinders are heavier than the lifers on the other four cylinders. GM brags about the millions of trouble free miles on their AFM engines of the past, but those were 5.3L trucks, not 6.2L higher revving Corvettes.
On the Corvette, the camshaft has two different lobe profiles with the lobes for the AFM lifters having "softer" ramps to accelerate/de-accelerate the heavier lifters. GM claims that it doesn't hurt airflow but that makes no sense. If the "softer" ramps don't hinder airflow, then why do they have the other eight lifters with a different profile that opens/closes the valve at a faster rate.
05-26-2016, 09:26 AM
Does the Z06 have the AFM valves
The only way I know of is to select "Info" for your instrument display, then scroll to the display in the window below where you can see the small "V8" (or "V4" when in the 4-cylinder mode). I pulled the pics below off the internet, and they must be from an A8 because they're in "Tour" (and the gear selection shows a "P" and "D"), and an M7 will only go into "V4" in "Eco":
