CAT IVA (Intake Valve Actuator) Defined...Kind of

Another thing that not many people know is when the compression brake is activated the Iva actuators hold the intake valve open for a few seconds, this minimizes the shock load on the exhaust rockers, something to consider when deleting or backing off Iva. I'm not saying you will all break exhaust rockers but it will definitely shorten there life!

 

not trying to be a smart-ace, but why in the world would you cut any
of those wires? also, you could have just unlugged them and taped them up or covered them. only things is, if you basically disabled them via the cut wires and ecm changes you still have the high compression factor. your still using factory18.1 pistons. acert head gaskets dont like that combo, but i guess different folks, different stroke......good luck.

 

Ok here yall go. you may need to read a few time for it to make sence,
It is quite a complex system and a half harted attempt to remove it all is not realy the answer,
The Variable Valve Actuator [VVA] system provides variable controlled intake valve timing. The main components of the VVA system are the three identical housings that include both a Cat Compression Brake and Intake Valve Actuators (IVA). Each VVA housing is positioned over two cylinders and controls inlet valve timing during the compression stroke and also works as an (optional) engine compression brake. The Variable Valve Actuator is held down by six mounting studs/nuts and one bolt.
Intake Valve Actuators (IVA) are also called Low Pressure Actuators (LPA), Variable Valve Actuators, Valve Actuators, or the standard part name, Actuator Gp - Valve.
The variable valve actuator housings contains Intake Valve Actuators (IVA), hydraulic/electric devices that use engine oil pressure to operate small actuator pistons. This action can control the closing of the intake valves by delaying the movement of the bridge (for the two intake valves per engine cylinder). The VVA system allows the ECM to vary the closing of the intake valves. Increasing the intake valve duration, allows control of the effective compression ratio (which results in optimized emissions and engine performance).
The timing of the intake valves on Heavy Duty ACERT engines are still primarily controlled by the camshaft profile. The VVA system can control the intake valve closing location (between 120 and 53 degrees BTDC) by holding the intake valve open after the normal cam profile would normally allow the valve to close. This enables the ECM to control cylinder pressures and heat in the cylinder during the compression stroke.
VVA Oil Rail – VVA oil supply is fed from the main oil gallery pressure. The VVA Oil Rail sees elevated pressure due to the containment of oil and the cylinder compression force pushing against the actuator.
VVA End of Rail (EOR) Valve - Is the VVA system pressure control valve or warm-up valve. The EOR valve is a normally closed valve that is used to release rail pressure for cold start capability and to provide pressure to the VVA rail under normal operation. When this solenoid valve is energized by the ECM, it opens and releases oil from the VVA oil rail.
VVA System Check Valve – This check valve is located at the VVA oil rail inlet. The VVA check valve allows lube pressure to travel from main oil gallery to VVA oil rail and keeps oil from draining out of the VVA oil rail line.
Low Pressure Actuator (LPA) valve – Provides actuation and control of individual VVA units. There are two LPAs for each VVA housing. These actuation solenoid valves are the same type as used in standard HEUI injectors.
VVA Detection – Software strategy utilized to diagnose VVA system mechanical failures to protect the engine from emissions non-compliance and structural damage due to elevated cylinder pressures.
Intake valves can be held up to 3 mm (0.118 in) off of the valve seats. This varies the intake valve timing BTDC (During the Compression Stroke)
The VVA system is not operational when the coolant temperature is below 20° C (68° F).
The VVA system is operational from 1100 - 2100 rpm @ 20 - 100% torque.

How it all works
.
Engine oil is supplied to the variable valve actuators through an oil supply rail (VVA rail) within the valve cover base and a jumper tube. An external line (oil galley) from the engine block supplies this oil rail. An orifice check valve is placed on the engine block side of this oil line in order to keep oil from draining out of the line.
The End of Rail (EOR) Valve is located in the valve cover base and is used to flush cold engine oil from the VVA oil rail after engine start-up. The EOR valve is a solenoid operated valve and is normally closed. The EOR valve opens when energized by the ECM, allowing engine oil to flow out of the VVA oil rail. This is needed in order to warm-up and flush the oil from the VVA rail. The released oil flows under the valve cover and returns to the oil sump.
The ECM will de-energize the EOR valve, when certain conditions are meet, allowing the VVA rail to attain the oil pressure needed for the VVA System to operate. The ECM will not de-energize the EOR valve until the VVA oil rail has been flushed for over 17 seconds
If the engine was started cold - after 17 seconds and the coolant temperature is greater than 20° C (68° F) the EOR valve will close (de-energize):
After the EOR is closed, the VVA system continues through a start-up initialization phase. During this time the engine will have a power derate and the status flag, "Intake Valve System Starting" will be present in ET (without any codes active or logged). The start-up power derate and the ET status flag, "Intake Valve System Starting" will be removed by the ECM when the VVA mapping logic is fulfilled and the VVA system is in normal mode. Various inputs are included in the VVA start-up logic including - time, atmospheric pressure, coolant temperature, intake manifold temperature and VVA detection (via the VVA oil pressure sensor).
When the engine is cold started - coolant and intake manifold temperature below 20° C (68° F) - the coolant temperature must be greater than 75° C (167° F) for the "Intake Valve System Starting" status flag to clear. When the VVA is in normal mode diagnostic fault codes will be used to derate the engine.
During VVA operation the pressure in the VVA oil rail will "pulsate" at 250 ± 50 kPa (36 ± 7 psi) higher than the rest of the lubrication system. This is due to the ECM firing (closing) the actuation solenoids and the cylinder compression force pushing against the actuators. These oil pressure rail pulses are sensed by an VVA Oil Pressure Sensor. The output of the VVA Oil Pressure Sensor is vital for VVA Detection (the software strategy which allows the ECM to control the VVA system).
An Intake Valve Actuator (IVA) (within the VVA housing) is essentially a valve follower during normal operation. The actuator motion is limited to 3 mm to prevent piston-valve interference. During operation, engine oil is directed to the Intake Valve Actuator assemblies at all times. This causes the VVA pistons (within the variable valve actuators) to be fully extended by the low-pressure oil. When the intake rocker arms comes into contact with these pistons, the force of the valve springs will push the VVA pistons back into their bores. To extend the intake valve closing location, the VVA actuation solenoid is energized (by the ECM). This closes the normally open actuator control valve, locking the VVA Piston in the extended position by trapping the oil in the actuator. Releasing the oil trapped in the VVA actuator controls the intake valve closing time. Each variable valve actuator, has a check valve built into it, that allows oil to flow into the actuator despite the actuator control valve position. This allows the VVA piston to follow the valve down and be locked open when the VVA control valve is again engaged.
During normal intake valve operation (without late intake valve timing), the variable valve actuators are not operational and are essentially a valve follower.
When the VVA system is operational, low pressure engine oil is directed to the variable valve actuators at all times.
When the valve mechanism opens a set of intake valves, the VVA piston (in the associated variable valve actuator) fills with oil. This causes the VVA piston to be fully extended by the low-pressure oil.
When the valve mechanism allows the intake valve to close, the intake rocker arm comes into contact with the VVA Piston. The force of the valve springs will push the VVA piston back into it's bore.
To extend the intake valve closing location, the VVA control valve (normally open actuator control valve) is energized by the ECM, locking the VVA piston (hydraulically locked) in the extended position (3 mm) by trapping the oil in the actuator.
The ECM then de-energizes the VVA control valve, releasing the oil trapped in the VVA actuator, this controls the intake valve late closing time.
A snubber assembly reduces intake valve velocity. Each VVA actuator has a check valve built into it that allows oil to flow into the actuator despite the actuator control valve position. This allows the VVA piston to follow the valve down and be locked open when the VVA control valve is again engaged.
The snubber assembly (in each variable valve actuator) controls the velocity at which the intake valves close when the solenoid is de-energized.
An accumulator (in the VVA circuit) and reduces the amount of valve bounce when the intake rocker arm comes into contact with the piston assembly.
Two orifices (or bleed holes) are located on each VVA housing in order to exhaust the pressurized oil to the oil sump. The orifices also act as an air bleed.
Two electrical Packard (bulk) connectors are used for the overhead wiring of the VVA housing. These connectors provide power to the six (2 wire) Intake Valve Actuator Solenoids. The number 1 and number 2 solenoids share a common wire, number 3 and number 4 solenoids share a common wire and number 5 and number 6 solenoids share a common wire.

 

Yea.............Something about my engine breathing "fresh" air instead of "EGR" air just appeals to my nature I guess. BTW It just rolled 680K on the odo today and It's never been cracked open yet so I guess time will tell. Still has EVERYTHING it came with from the factory except 2 injectors. But it's getting the thermostats changed this week.........Brrrrrrrrrr.
Oh....and the reason they are cut.....They are JUST wires. They currently have female lugs on the end.

 

Clean gas induction?
What is that gas? Exhaust.
That means it is an EGR.



If you put on a gas mask, would you call "breathing" something different because its going through a filter first?

 

Older videos but still something to watch if morehp explanation was to much understand.


http://youtu.be/djWN_HGYbF0

http://youtu.be/6wlxH5zNVu8

 

It's a shame all the time we spend reading, and explaining, trying to get our motors to half their protential, because of restictions.

 

Wow.. what did I just read...

5 star thread!

 

So... many... words...

Pretty dry reading material for my lunch, but greatly appreciated. I thought. I had a pretty clear picture of the ACERT systems, and I did. I just didn't have the letterbox version. So many details around the peripheral. The info on the EOR solenoid and the operational temp range and such is priceless if you're troubleshooting a naughty ACERT engine.

Thanks, sincerely, for so much useful information. I've really been enjoying figuring out ACERT and I run a 6NZ. Just good to know with the old man and a friend or 2 runnung the BXS and MXS engines.

 

First off the emission stuff started in 1970, the latest was passed in 2004, George and his boys, the Cat uses EGR the old way by closing the exhaust valve early,and cam profiling, the Miller effect lowers the friction HP. That is the HP it would take to run the engine with no fuel added. It makes no sense to compress air that you do not need for combustion.
I am glad to see that there are people on this site that know better than the engineers that built the engine on how an engine works and how to make the most HP efficiently. The Acert is not a very efficient engine, read the number on the EPA tag, they do drive nice, as a mechanic when they first came out Cat did not pay for the warrenty repairs the wanted done.
Just a thought!