LCV connections

[07midnight57]

Originally Posted by arizonawarrior

Said another way, sometimes while riding the oil drops below 176F and the ECU opens the LCV a bit and adds a bit of extra fuel. It might only open one point or five points or whatever, its a computer it figures those things out.

The LCV is an air pump (this we know, just saying it for those that do not). Just for the sake of converstation if the LCV is adding air, isn't that beacuse the engine needs more air and not fuel? The hoses from the LCV go to the intake manifold past the throttle body blades. Meaning that it adds air to the same amount of fuel that is present at that time based on throttle position. Adding more air and not adding fuel would lean out the AFR therefore causing an increase in combustion chamber temperature and increasing engine temperature. If the LCV is adding air and at the same time the ECU is also increasing the duration of injector opening (adding a little more fuel) wouldn't that just negate the fact of trying to increase engine temperature.

I do not know as much as you do Arizona so this is a great place to discuss this topic and hopefully I can learn something as I always do from you and this site. The above is my understanding of the LCV system. I do not think I know more than anyone else on this topic and I do not claim to know exactly how yamaha has the LCV system set-up to work and the above are just my thoughts and idea of how it works.

So what say you?

[arizonawarrior]

Running the motor lean across the rpm range isn't a good way to heat the motor oil. More fuel and air means more explosion and more heat is generated safely. As you might know, the service manual is descriptive about how and when the LCV adjusts and the ECU adds matching fuel. The LCV isn't an air pump, just an opening to atmosphere like the venturi. The valve closes some specific amount as the motor oil warms up and when the motor oil sensor reads 176F the valve is fully closed. At lower temperatures the LCV's valve is partly open and the ECU matches the extra air with extra fuel via injector duration. Its described pretty well in the service manual, spread across several areas in the manual. Easy to find by searching the PDF for 'linear' or similar. Taken as a whole, that's how it works. So I'm actively posting when appropriate because I want to learn more. I realize a lot of guys have successfully trashed the LCV, and many of those may not have realized the LCV has 146 adjustment positions and doesn't fully close until the oil temp sensor reports 176F. Additionally, it appears the LCV re-opens to some varying amount when and as the oil temp sensor drops below 176F but I'm having trouble confirming that. I like to get a couple opinions before I believe something that isn't spelled-out in the service manuals. If the LCV does re-open as engine oil temperature falls (such as when riding clear roads over the top of a snowy mountain pass) then for me its a game changer as long as I'm in northern climates. Back in the desert I probably would't care a bit about the LCV.

[Link71]

Originally Posted by Jbat

yep, that is the intake for the LCV. Usually when a VBAK is put on you have a hose with a little filter connected as rcoligan2 said. capping won't hurt anything the LCV just wont be able to take in air and probably won't idle high on warm up.

I HATE the high idle at startup.....so by capping just the one end that draws in air for a few days....I can decide whether or not I want to remove my LCV permanently?

[4UTNV]

If you cap that, and the other two hoses are still secured to the throttle bodies tightly, yes that should eliminate all air being able to enter the lcv. So if you dont like the high idle, you can heave ho like so many of us

[07midnight57]

Yes lean across the rpm range is bad, I assumed it wouldn't do it across the whole range and just in a few areas or while cruising based on throttle position.

So since it is not a pump, the air is being drawn in via manifold vacuum and the valve just varies in open positions cutting off the amount of air being drawn in?

[arizonawarrior]

07, Yep you got it bro.

I was thinking these are probably the 'cases' for this system, did I cover all of the possibilities and get the Air Fuel Ratio (A:F) right?

Added member ideas and clarified 14 Sept 2012.
Amended: service manual states extra fuel added in response to intake air pressure sensor (IAPS)
recognizing more air and signaling the ECU which adjusts injector duration thru normal method, 14 Sept 2012.

LCV Installed and Working.
Starting: ECU opens LCV to some extent, IAPS senses more air so ECU adds extra fuel so A:F is correct.
Running and oil below 176F: ECU adjusts LCV, IAPS signals ECU which adds extra fuel so A:F is correct.
Running and oil above 176F: ECU closes LCV, IAPS senses less air so ECU cancels extra fuel and A:F is correct.
Running and oil again falls below 176F: Does ECU re-open LCV making IAPS signal ECU for extra fuel? (most say no)

LCV stuck Fully-Closed or Capped or Unplugged or Removed.
Starting: ECU signals to open inoperative LCV, IAPS does not sense more air so ECU does not add extra fuel, A:F is correct.
Running and oil below 176F: ECU signals to adjust inoperative LCV, IAPS does not sense more air so ECU does not add extra fuel, A:F is correct.
Running and oil above 176F: ECU signals to close inoperative LCV, IAPS does not sense more air so ECU does not add extra fuel, A:F is correct.
Running and oil again falls below 176F: Even if ECU re-signals to open inoperative LCV the IAPS does not sense more air so the ECU does not add extra fuel, A:F is correct.

LCV stuck Fully-Open or Intake Hoses Left Uninstalled. See also (*) and (**)
Starting: ECU signals to open inoperative LCV, IAPS senses more air so ECU adds extra fuel, A:F is correct.
Running and oil below 176F: ECU signals to adjust inoperative LCV, IAPS senses more air so ECU adds extra fuel, A:F is correct.
Running and oil above 176F: ECU signals to close inoperative LCV, IAPS senses more air so ECU adds extra fuel, A:F is correct.
Running and oil again falls below 176F: Even if ECU does not re-signal to open inoperative LCV the IAPS senses more air so the ECU add extra fuel and A:F is correct.

I figured I'd put this out there and see who I can learn from since this thread was already on the topic. Thanks everyone.

[balance deleted because even if parts are right its not relevant!]

[Churchkey]

The LCV is a valve not a pump. It is actually a device that operates 180* differently than a hand choke. It allows air into the engine instead of limiting the amount of air the engine gets like a choke does.

The ECU does not add more or less fuel dependent on LCV operation.

The ECU operation is dependent on preset parameters controled by temp & pressure sensors. It operates in open loop the same as your injected cage does on start up.
Your cage however changes to closed loop when the O2 sensor reaches 600 *. No 02 on the bike, it remaims in open loop.

Lower temps & up to the YAMAHA figure of 176* is cold for an engine, it needs more fuel at low temps for smooth throttle response. A stock bike runs like crap when its cold & normally stalls at the first stop, The LCV is the primary cause of this problem.

When pipes etc are changed the bikes need more fuel during cold & hot engine temps.
They do not need a device that automatically leans out the fuel mixture that was designed for a stock bike with restrictive intake & exhaust systems.

[active1951]

Originally Posted by Churchkey

The LCV is a valve not a pump. It is actually a device that operates 180* differently than a hand choke. It allows air into the engine instead of limiting the amount of air the engine gets like a choke does.

The ECU does not add more or less fuel dependent on LCV operation.

so how does it richen mixture for cold starts???
.
.

[Jbat]

It doesn't, LCV lets air in which actually would lean it out. According to AZ above posts the ECU does add more fuel during cold engine temps which accompanied with the air from the LCV would raise the idle, as if you were turning the throttle. But I am not sure when and how much it adds.

[alanh]

Originally Posted by active1951

so how does it richen mixture for cold starts???
.
.

The enrichment cycle only works on start-up! Nada Mas ... this is not a smart device and has no feed-back to the engine control unit.

IMO the real world operation of the LCV is as stated by Churchkey HERE:

• The ECU does not add more or less fuel dependent on LCV operation.
  
  The ECU operation is dependent on preset parameters controlled by temp & pressure sensors. It operates in open loop the same as your injected cage does on start up.
  Your cage however changes to closed loop when the O2 sensor reaches 600 *. No 02 on the bike, it remaims in open loop.

_______________________________

If you do your Due Dilligence on this device in the Yamaha factory shop manual you'll want to search for both 'LINEAR & LINER' and also take note that there is an error on the rotation angle of the stepper motor that should read 1.5* and not 15*

Because there is no feed-back the LCV is driven OVERCLOSED each and every time the engine is shut-down with the normal key-off procedure.

IMO there is way to much emphasis of the importance of this valve and its interaction with the engine management system.
Once the engine oil reaches 176*F it's history ....
_______________________________

ADDED:

• LCV (linear control valve) 101