L99 AFM -- It's REALLY a tough choice, for some. Step Inside.

[radz28]

I believe the L76 has the AFM and there is a shop in So. Cal. (I believe) that has added a TVS MP1900 to a G8 with the L76 and it was running pretty good with and without the AFM working. I believe they were still intent on seeing if tuning would get the PCM squared away...

http://www.g8board.com/forums/showthread.php?t=3959

[jmliptak]

Originally Posted by camaro1

you are correct, look back 2 post's from yours,, man the board is moving fast today!

I think we were probably typing at the same time, it shows they were posted a minute or so apart, thanks for the additional info, it does make a lot of sense....

[theholycow]

Originally Posted by Captain Awesome

That's a good question. Does anyone know what the deactivated cylinders do when they are "off"? If the valves are still opening and closing wouldn't that cause problems with forced induction?

The valves are inoperative (I think closed) when AFM is active. I thought that was why people fear difficulty modifying it...

[camaro1]

Here is the complete AFM/DOD description straight from the gm service manual:

To provide maximum fuel economy under light load driving conditions, the engine control module (ECM) will command the cylinder deactivation system ON to deactivate engine cylinders 1, 7, 6, and 4, switching to a V4 mode. The engine will operate on 8 cylinders or V8 mode, during engine starting, engine idling, and medium to heavy throttle applications.

When cylinder deactivation is commanded, the ECM will determine what cylinder is firing, and begin deactivation on the next closest deactivated cylinder in firing order sequence. For example, if cylinder number 1 is on its combustion event when cylinder deactivation is commanded ON, the next cylinder in the firing order sequence that can be deactivated is cylinder number 7. If cylinder number 5 is on its combustion event when cylinder deactivation is commanded ON, the next cylinder in the firing order sequence that can be deactivated is cylinder number 4.

Cylinder deactivation is accomplished by not allowing the intake and exhaust valves to open on the selected cylinders by using special valve lifters. The deactivation lifters contain spring loaded locking pins that connect the internal pin housing of the lifter to the outer housing.

The pin housing contains the lifter plunger and pushrod seat which interfaces with the pushrod. The outer housing contacts the camshaft lobe through a roller. During V8 mode, when all cylinders are active, the locking pins are pushed outward by spring force, locking the pin housing and outer housing together causing the lifter to function as a normal lifter. When cylinder deactivation is commanded ON, the locking pins are pushed inward with engine oil pressure directed from the valve lifter oil manifold (VLOM) assembly solenoids. When the lifter pin housing is unlocked from the outer housing, the pin housing will remain stationary, while the outer housing will move with the profile of the camshaft lobe, which results in the valve remaining closed. One VLOM solenoid controls both the intake and exhaust valves for each deactivating cylinder. There are 2 distinct oil passages going to each cylinder deactivation lifter bore, one for the hydraulic lash-adjusting feature of the lifter, and one for controlling the locking pins used for cylinder deactivation.

Although both intake and exhaust valve lifters are controlled by the same solenoid in the VLOM, the intake and exhaust valves do not become deactivated at the same time. Cylinder deactivation is timed so that the cylinder is on an intake event. During an intake event, the intake CAM lobe is pushing the valve lifter upwards to open the intake valve against the force of the valve spring. The force exerted by the valve spring is acting on the side of the lifter locking pins, preventing them from moving until the intake valve has closed. When the intake valve lifter reaches the base circle of the camshaft lobe, the valve spring force is reduced, allowing the locking pins to move, deactivating the intake valve. However, when cylinder deactivation is commanded ON, the exhaust valve for the deactivated cylinder is in the closed position, allowing the locking pins on the valve lifter to move immediately, and deactivate the exhaust valve.

By deactivating the exhaust valve first, this allows the capture of a burnt air/fuel charge or exhaust gas charge in the combustion chamber. The capture of exhaust gases in the combustion chamber will contribute to a reduction in oil consumption, noise and vibration levels, and exhaust emissions when operating in V4 mode cylinder deactivation mode.

During the transition from V8 to V4 mode, the fuel injectors will be turned OFF on the deactivated cylinders. To help prevent spark plug fouling, the ignition system secondary voltage or spark is still present across the spark plug electrodes on the deactivated cylinders. If all enabling conditions are met and maintained for cylinder deactivation operation, the ECM calibrations will limit cylinder deactivation to a cycle time of 10 minutes in V4 mode, then return to V8 mode for 1 minute.

Switching between V8 and V4 modes is accomplished in less than 250 milliseconds, making the transitions seamless and transparent to the vehicle operator. The 250 milliseconds includes the time for the ECM to sequence the transitions, the response time for the VLOM solenoids to energize, and the time for the valve lifters to deactivate, all within 2 revolutions of the engine crankshaft.

Valve Lifter Oil Manifold (VLOM) Assembly
The cylinder deactivation system uses an electro-hydraulic actuator device called the valve lifter oil manifold (VLOM) assembly. The VLOM is bolted to the top of the engine valley, below the intake manifold assembly. The VLOM consists of 4 electrically operated normally closed solenoids. Each solenoid controls the application of engine oil pressure to the intake and exhaust valve lifters on the cylinders selected to deactivate. Engine oil pressure is routed to the VLOM assembly from an internal oil passage on the rear of the cylinder block.

All 4 VLOM solenoids are connected in parallel to a fused ignition 1 voltage circuit, supplied by the powertrain relay. The ground or control circuit for each solenoid is connected to a low side driver internal to the engine control module (ECM).

When all enabling conditions are met for cylinder deactivation, the ECM will ground each solenoid control circuit in firing order sequence, allowing current to flow through the solenoid windings. With the coil windings energized, the solenoid valve opens, redirecting engine oil pressure through the VLOM into 8 separate vertical passages in the engine lifter valley. The 8 vertical passages, 2 per cylinder, are connected 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 control circuit for the solenoids, allowing the solenoid valves to close. With the solenoid valves closed, engine oil pressure in the control ports is exhausted through the body of the solenoids into the engine block lifter valley. The housing of the VLOM incorporates several bleeds in the oil passages to purge any air trapped in the VLOM or engine block.

To help control contamination to the hydraulic circuits, a small replaceable oil screen is located in the VLOM oil inlet passage, below the oil pressure sensor. The oil pressure sensor is a 3-wire sensor which provides oil pressure information to the ECM.

During service, use extreme care in keeping the VLOM assembly free of any contamination or foreign material.

Cylinder deactivation may be inhibited for many reasons, including the following:

• Engine coolant temperature out of range for cylinder activation

• Engine vacuum out of range

• Brake booster vacuum out of range

• Transmission gear incorrect or shift in progress

• Accelerator pedal out of range or rate of pedal application too fast

• Engine oil pressure and temperature out of range

• Engine speed out of range

• Vehicle speed out of range

• Minimum time in V8 mode not met

• Maximum V4 mode time exceeded

• Decel fuel cutoff active

• Reduced engine power active

• Torque management active

• Catalytic converter over temperature protection active

• Piston protection active, knock detected

• Cylinder deactivation solenoid driver circuit faults

[Captain Awesome]

Wow. That's awesome. Thanks for the info!

[theholycow]

Originally Posted by camaro1

Switching between V8 and V4 modes is accomplished in less than 250 milliseconds, making the transitions seamless and transparent to the vehicle operator.

...well, apparently not true if the vehicle operator likes to shift his own gears.

[2KZ28_For_Now]

Originally Posted by camaro1

Here is the complete AFM/DOD description straight from the gm service manual:

Thanks for the info!

[Nexus6]

mine will be purely for fun so i want the manual transmission.so LS3 for me

[shank0668]

6 speed for me

[2KZ28_For_Now]

My bad -- I've duplicated this thread:
http://www.camaro5.com/forums/showthread.php?t=5548

Keerap!

Anyways, I hope this thread gets merged, or everyone just go over to that other thread to answer.

[06TBSS]

Originally Posted by daddyseth1

Is SCT the only tuner brand out there? If not, can someone let me know of any other tuner companies? Thanks a bunch.

He flashed my Trailblazer, got rid of 2nd gear timing retard and firmed up shifting....awesome now especially when stabilitrak and traction control is off.
http://www.vectormotorsports.com/ind...tpage&Itemid=1

If he can tune a turbo LS2 Grand National he can tune your L99/ LS3....DOD or not....


I was going to say MTI in Houston but they have gone out of business for some reason as I just googled and no more!....wow

[TFord]

Originally Posted by camaro1

the only time the afm/dod kicks in is when you are cruising at a steady speed at a very light load ,, in these conditions you would never be seeing boost anyways,,, the only time you get boost is when you are accelerating and under high engine load

example:

so even if you were cruising down the hwy at 65+ mph and in 4cyl mode and went to pass someone the afm/dod would turn off instantly as soon as you pushed down on the gas pedal you would be running on all 8 cylinders and your boost would come on like normal


and whatever company comes out with a supercharger will probly be including a ecm tuner or you will be sending your ecm to them to be flashed for the supercharger anyways

See I understand your logic put the problem I see is this...

with a roots style blower your boosted no matter what. The amount of boost is directly porportional to the engine RPM's hince the term "blower" lets say I gun it untill I hit 70 mph and then cruse, once Im crusing afm kicks in and 4 cylinders close Im still forcing in a volume of air porportional to my RPM's thats designed to be split between 8 cylinders, but now I have 4 so I just doubled the volume of air being sent to these 4 cylinders. Isnt there is the potential to do this to your block

[Camaroman_99]

Right now, I plan on getting the 6-speed.

[CamaroSpike23]

hey.... i just got to thinking about something after reading a post from DGthe3 in another thread...



people are complaining about the manual SS not being paired up with the L99.... buuuuuuuuuuuuuuut, doesnt the AFM only activate during low load, idle, and cruising situations? (stick with me on this)

GM theoretcially should be able to do a manual L99 with AFM..... but they would have to program it so that it only activates when at idle in N or with the clutch fully depressed at a stop (with a microswitch/sensor on the clutch linkage so that when you release the clutch it goes back to V8) and have it programmed to be active when cruising in 6th gear (highway) and deactivate when you push the clutch in when cruising. and since the 6th gear is only really for fuel economy, add to that the AFM and you could yield 50+ mpg highway with the manual...

now this is all theoretical, but i dont see why it wouldnt work....