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AFM V8/V4 Mode

AFM V8/V4 Mode

Postby atxltz [OP] » Jan 27 2011, 6:54am

Is there a way to turn off the AFM system with a programer or tune? I just put a flowmaster on my truck and can hear and feel the switching between modes and it starting to get on my nerves! The truck also feels slugish switching out of V4 mode.
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Re: AFM V8/V4 Mode

Postby 99chevyz71 » Jan 27 2011, 8:22am

most tuners or programmers can turn it off
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Re: AFM V8/V4 Mode

Postby EKinMN » Jan 27 2011, 2:07pm

If you have the 6 speed auto, you can also run in 4th or 5th (manual mode) around town, and it will not go into V4. But yes, most tuners can turn it off.
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Re: AFM V8/V4 Mode

Postby yamaha911 » Jan 06 2012, 11:30pm

Dude I know what your feeling, I could not stand that AFM noise and shudder!
It really amplified when I threw a lift and 35's on!
So I just got a Hypertech Max Energy and turned that crap off.
Its your best bet man, you get better power and milage and their not too expensive. Go to autoanything.com.
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Re: AFM V8/V4 Mode

Postby oldsaltydog » Jan 07 2012, 2:06am

Yep turned mine off with my Intune tuner actually gets better mileage off mine sounded like a diesel in v four mode with my dual exhaust much better now
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Re: AFM V8/V4 Mode

Postby O'Brien » Jan 07 2012, 4:04am

Do you think that will effect the factory warranty in the event of a non AFM related issue should one arrise? Seems I read somewhere it would but have no way to verify.
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Re: AFM V8/V4 Mode

Postby EKinMN » Jan 07 2012, 2:48pm

GM would have to prove that turning off the AFM was specifically what caused a failure. Otherwise they cannot void your warranty. Having the AFM off will not cause brake, suspension, drivetrain, etc type of failures. Now if there was an internal failure in your engine, they may claim it was due to the fact you "tinkered" with the engine. But, they would have to prove it....and I doubt they could.
Also, remember, AFM is not a mechanical process. Its all done electronically. Your vehicles computer is simply shutting off fuel flow and shutting down the spark to those cylinders. By turning AFM off, all you are really doing is telling the computer to operate "normally" all of the time, and to not use a feature. I cannot see where there could be a mechanical problem related to turning off the AFM.
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Re: AFM V8/V4 Mode

Postby LGSONE » Jan 07 2012, 2:55pm

The reading I have done regarding AFM:

Cylinder Deactivation (Active Fuel Management) System Description
System Operation
General Motors Active Fuel Management engine control system has the ability, under certain light load driving conditions, to provide maximum fuel economy by deactivating 4 of the engines 8 cylinders. The engine will normally operate on 8 cylinders in V8 mode during starting, idling, and medium or heavy throttle conditions. When commanded ON, the engine control module (ECM) will direct the active fuel management system and deactivate cylinders 1 and 7 on the left bank and cylinders 4 and 6 on the right bank, forcing V4 mode. Refer to Lubrication Description and Cylinder Deactivation (Active Fuel Management) System Description.

Valve Lifter Oil Manifold Assembly

The valve lifter oil manifold assembly is bolted to the top of the engine block beneath the intake manifold assembly. The oil manifold consists of 4 electrically operated and normally-closed solenoids. Each solenoid directs the flow of pressurized engine oil to the active fuel management intake and exhaust valve lifters. The active fuel management oil pressure relief valve, located in the oil pan, regulates engine oil pressure to the lubrication system and the oil manifold.

When enabling conditions are met for active fuel management operation, the ECM will ground each solenoid control circuit in firing order sequence, allowing current to flow through the solenoid windings. With the windings energized, the solenoid valves open and direct pressurized engine oil through the valve lifter oil manifold into 8 vertical passages in the engine block lifter valley. The 8 vertical passages, 2 per cylinder, direct pressurized oil to the valve lifter bores of the cylinders to be deactivated. When vehicle operating conditions require a return to V8 mode, the ECM will turn OFF the ground circuit for the solenoids, allowing the solenoid valves to close. When the solenoid valves are closed, remaining oil pressure is exhausted through the bleed passages of the valve lifter oil manifold into the engine block lifter valley. The housing of the oil manifold incorporates several oil bleed passages that continually purge trapped air from the manifold and engine block.

To help control contamination within the active fuel management hydraulic system, a small replaceable oil filter is located in the valve lifter oil manifold oil inlet passage. The oil pressure sensor monitors engine oil pressure and provides information to the ECM.

Active Fuel Management Valve Lifters

When operating in V8 mode, the active fuel management valve lifters function similar to the non-active fuel management valve lifters. The active fuel management oil manifold solenoids are in the closed position, with no pressurized oil directed to the valve lifters. The pushrod travels upward and downward to actuate the rocker arm and valve. The spring loaded locking pins of the lifter are extended outward and mechanically lock the pin housing to the outer body of the valve lifter.

When the active fuel management system is commanded ON, the ECM will direct the solenoids of the oil manifold to open and direct pressurized oil to the valve lifters. Oil travels through the valve lifter oil manifold and engine block oil galleries and enters the inlet port of the valve lifter.

When operating in V4 mode, pressurized oil forces the locking pins inward. The pushrod remains in a constant position and does not travel upward and downward. The outer body of the lifter moves upward and downward independently from the pin housing. The valve lifter spring retains tension on the valve train components to eliminate valve train noise.

When the active fuel management system is commanded OFF, the ECM directs the solenoids of the oil manifold to close, stopping the flow of pressurized oil to the valve lifters. The oil pressure within the lifter will decrease and the locking pins will move outward to mechanically lock the pin housing and outer body.

The active fuel management engine block incorporates additional features to support active fuel management system operation. Engine oil pressure is routed to the valve lifter oil manifold assembly from an oil gallery in the rear of the cylinder block. Cylinders 1, 4, 6, and 7 each have 2 vertical, cast-in-block oil passages . The vertical oil passages permit oil flow from the manifold assembly to the valve lifter bores.

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Re: AFM V8/V4 Mode

Postby EKinMN » Jan 07 2012, 3:03pm

I stand corrected. I did some "research" (via Google) and found the same things as LGSONE posted. So it is both mechanical and electronic. But still, I don't see how it could void a warranty by NOT using the function.
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Re: AFM V8/V4 Mode

Postby LGSONE » Jan 07 2012, 3:07pm

I thought is was as you stated EK but when at the speed shop I was "enlighted". Those guys HATE the AFM.

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