Does anyone know if this valve isn't working will it affect performance?

 

I'm assuming that you're referring to the NPP exhaust valves and not the AFM valves? I believe that the NPP valvles fail open which means that they would technically be in track mode and would not impact performance. If they are somehow in the closed position and not working then, yes it will choke the exhaust down a little, but shouldn't be a big impact to performance.

 

Thanks

I am not sure if its npp or afm. The dealer ordered the part out of LA and said it would be a good 4 hour job.

 

Probably an AFM valve if they are saying it is a 4 hour job since the AFM valves are more challenging to access compared to the NPP valves. I'm just not sure if the AFM valves fail closed or open. If closed, I could see them choking the exhaust down which is why I suspect that they too fail open, but it is just a hunch.

 

The AFM and NPP valves fail open. I'm 100% sure of this. I've answered this in the OP's other thread.

https://www.corvetteforum.com/forums...26c8-code.html

Both valves are built the same with a heavy spring holding them OPEN. The actuators close the valves when powered, driving against this spring. When no electricity applied...the spring forces the valve open.

Try it for yourself with the NPP valves. Stick your finger in one of the tail pipes and close the valve manually. It will spring back open.

The AFM and NPP actuators are the same part #, as are the valve spring/mount/shaft assemblies. However, the valve blade for the AFM has a hole in it and the NPP blade does not.

The only exception would be if the actuator seized under power with the valve closed. This is highly unlikely. If the AFM valve was seized closed, the exhaust would be very quiet from that side and the OP would notice only one side of his exhaust making the normal rumble.

 

Thanks again

It is somewhat confusing. The AFM valve must be hard to get to if the dealer needs more than four hours.

 

You can see in the picture below the AFM valves sit just in front of the mufflers and are tucked up inside the frame.

To access them the axle back assembly has to come out. That means removing the lower rear fascia on the bumper cover, removing the tunnel plate, unclamping from the X-pipe, and disconnecting the wiring/hanger isolator/center bolt. Then the assembly slides out the rear, and the actuator can be replaced easily. And then put it all back together. I'd say 4 hours is a generous estimate for this work by a professional. On a lift with the right tools, 2 hours seems more like it IMHO.

 

^ very helpful..

Now I have a question for you..

I installed my Akrapovic axle back and a CEL came on.. Almost positive its my AFM because my NPP works flawless. I hear the AFM valves malfunctioning when I go from v8 to v4 mode.. Any suggestions?

-Johs

 

Yeah, the actuators for AFM are uniquely calibrated to the valves they get installed on. They are checked for function on each startup, and any minor variation in force profile/duty cycle will throw a CEL. That's also the reason the AFM fuse (32) can't be pulled without throwing a CEL after a couple start/stops.

There is a dealer calibration/relearn procedure whenever actuators are replaced or swapped onto a new exhaust. Going to the dealer and asking for this reprogram -may- help your problem IF the Akra valves are actually operating within GM specifications.

The aftermarket has not done well in replicating the GM OEM valves. There are stories for all the aftermarket makers that make systems with AFM valves throwing neverending CELs. Just see the Borla backorder threads and David Borla's explanation for how sensitive the AFM duty cycle is...

My personal recommendation would be to disable the AFM functionality via a Range Technology plug or tune and bask in V8 glory all the time (with NPP fuse 41/42 pull or the addition of a DIY fuse remote or actual M2W). Then remove the actuators from the AFM valves and tie them up out of the way (they need to stay electrically connected to the car to avoid CEL), or buy this AFM actuator delete kit from CF sponsor Cajun Edgy Vette:

https://www.corvetteforum.com/forums...te-module.html

 

My AFM valves have been deleted via a tune and the actuators removed and the delete kit from Edgy Vette installed. All was well until today when the cel light re: engine came on. The codes are P12EF and P26C8. Both refer to the valve operation. I will have the cel reset and hopefully all will be well. The car had been working flawlessly in V8 mode without the AFM and the NPP was also removed and fuse 42 pulled. Not sure why after almost 4 months the cel would come on.

 

^ The CEL delete is no longer sold by Cajun due to issues.

So a range disabler that plugs into the OBD, and a way to keep the valves open.. sigh!

-Josh

 

So much for whatever warranty there may have been. Companies that don't stand behind their products shouldn't be in business. They worked for 4 months. Let this be a heads up to other potential customers.

 

Hi all, I recently had a Borla Atak installed at the Carlisle show and my car now throws a check engine light, Borla was there and reset it twice then changed the over the axle pipe. 2 hours later on the way home after I shut the car off and restarted it the check engine light came on. I contacted Borla as they are aware of my issue specifically, they told me they are working on a solution and will get back to me soon. I've had read some threads out there about this, anyone have a solution. Oh BTW, I did read on this forum it was recommended to go to GM and have them relearn the AFM valves, it was done and it didn't work ($150.00). Thank you for any information.

 

^ Thats what I'm afraid of. Getting it relearned but it doesn't do anything.

-Josh