The £10 cure for VCT Rattle

[munkul]

(new thread to clear up confusion about nistune/software/other unrelated crap, mods can you close the other thread please?)

First of all, I take no responsibility for this mod! It has and is working well on my own car, and I can see absolutely no downside to this mod, short-term or long-term, due to the way the VCT operates normally. However, It's up to the individual to decide whether this is a good idea or not.

Yes, I know, it sounds like a typical internet scam but it seems so ridiculously easy and cheap compared to forking out for a new sprocket for £300+, and having it fail a year or two later!

This is what I did earlier. Warm engine (90 degrees oil temp) it starts rattling like its about to die.



So... surely I'm not the first person to discover this?

So what I propose is a microswitch mounted on the TB so that whenever it is closed (ie, idle) it closes the earth circuit to the VCT solenoid and activates it. As you can see from the video, there doesnt seem to be any ill effects.

You dont use +12v, you use earth. The VCT solenoid is negatively fired - the ECU circuit pulls to earth. Easy to work out on a multimeter. The yellow wire is the earth trigger wire, the other wire is +12v on ignition.

This is my setup. I have made a bracket that bolts straight into the arm for the cold idle stat valve. (yes mine is redundant but it should work perfectly on a plumbed stat!) I have tapped neatly into the wiring on the inlet manifold for the earth trigger wire and gone under the stock engine earth at the other end. Please excuse the untidy loose wires, its only a trial




Only issue now is my switch lever arm is a bit **** and has a bit too much sideways movement, so could jam at some point.

This has now worked perfectly for a week and varied driving.

Questions?

Does this totally cure it?
No. It merely removes the symptoms of a worn VCT sprocket. A worn VCT sprocket has been known to work perfectly well in operation, apart from the horrible noise found at idle, because it is normally switched off at idle and therefore has no oil pressure to cushion the VCT splines (?) inside the sprocket. Switching it on at idle keeps oil pressure up and therefore the sprocket splines are cushioned.

Does this affect the idle quality?
No. It doesnt affect the idle quality whatsoever. At ALL. Not even my AFRs are affected.

Will it work forever after this mod?
I don't know, I THINK it will depend on how worn your sprocket is to start with. My sprocket is just a LITTLE louder when activated at idle, than a properly working (silent) sprocket is, when not activated. But mine is rather worse than a lot of cases

Will it make an ok sprocket worse with time?
I dont know, and this is where part theory and part speculation comes into play. The constant oil pressure should cushion the sprocket internals and reduce wear. On the other hand, is there a good reason why Nissan wanted no oil pressure at idle? Possibly because it would receive too much pressure from a cold start? Possibly the fact that some of us that use 50-weight oil instead of 40-weight has something to do with failure? Not as far as I can tell from my forum research, but you never know.

Can you not adjust the set point of VCT activation with a standalone ECU or with Nistune?
With a standalone ECU like Link or DTA, yes. I dont know about the Apex'i Power FC though, cos the program architecture is similar to Nissan and Nistune. Nistune will let you adjust the set point, BUT also needs the neutral and TPS idle indicator to be off. Making it pointless. There are no plans by Nistune to alter this for us for the time being.

(to be edited as seen fit if anyone else can shed more light on this)

[Sean-B]

Just to add to this. It doesn't work with Tomei Poncams it won't idle.

However I've set it up to a moment switch and just holding the switch on for 2-3 seconds when first turning on the engine prevents any rattle for the rest of the drive.

My VVT rattle wasn't very bad but was noticeable on idle.

[mikeyrs]

doesnt work with hks step 2's either. it would idle but very bad and sounded like a bag of nails going through the turbo.