Active Fuel Management Issues / Question

[94boosted]

11 hours ago, 300 Blackout said:

The valve is not controlled by the tune. The valve doesn’t have any electronics, it’s simply a butterfly valve with constant spring pressure that defaults to the closed position until enough exhaust pressure causes the valve to open completely.

The truck always starts in V8 so the AFM delete really isn’t doing anything different than normal at startup. It simply doesn’t allow the truck to exit V8, therefore, the valve always stays open (until you shut off the truck).

Easiest way to disable the valve is with a clamp. Get a wrench, manually turn the valve to the open position and clamp it there. If you leave AFM active with the valve clamped open, you’ll likely hear what is described as the “chopper” noise when traveling in V4 mode. It’s entertaining to say the least. You’ll feel like George Jetzin puttering down the highway.

The other option is to cut the valve out. Most guys who do this cut out their muffler and straight pipe from the 3rd cat to just behind where the valve used to be. If you leave the resonator (looks like a smaller muffler above the rear axle), you actually end up with a nice sounding exhaust. Cost is about $50 at a muffler shop. Takes less than 30 minutes.

Thank you for the detailed response 300 Blackout that's really helpful!

 

I may just do what you suggested regarding cutting out the valve and muffler just down stream of the third cat. Do you get any drone at highway speeds after doing that? What about when towing? 95% of the exhaust systems I've heard on trucks sound great in the city but when driving out on the freeway, especially while towing/under load, they sound awful. 

 

[Jaychevy81]

I removed the valve when I did a full magnaflow cat back system. I turned off v4 with a tuner and never looked back.


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[gilkman]

wanted to add another experience with this.  I just took my 2014 6.2L into the dealer to have them look into a loud ticking sound.  turns out the #4 AFM lifter rod was bent.  they are recommending replacing the rod/lifter for all 4 cylinders on that side of the engine.  Truck only has 55k miles on it, but I have had it for over 5 years...so out of warranty.  Dealer actually contacted GM and they are agreeing to pay for the bulk of the cost.  they will not say that the AFM caused this, and I don't have any facts to back that up.  I am impressed that GM would cover most of it out of warranty.  given the low mileage, I think they should.  I also have been dealing with this particular dealer for a while, and they are truly one of the best.