How to tell if VCT working?

[calaistur]

HI guys,

I have put together an RB25/30 combo with a Microtech LT8. What I want to know is how do you tell if the VCT is working or not? It has been programmed to come 'on' at a certain rpm but how do you really tell if it doing anything?

Thanks

Justin.

[crooser]

Next time the car/engine is dynoed try unplugging it for a run.

[calaistur]

OK. Will do.

Does anyone know exactly how it is activated?? There is a 'device' on the side of the head but what exactly does it do and is there a way to test it?

[calaistur]

Still doesn't work guys.

The mechanic says the computer is switching the solinoid type thingy on the head ok but nothing seems to be happening internally. Does anyone know what might be happening. The head was only reassemble a short time ago, could something have gone wrong? Does anyone have a manual they can look up to see it says anything?

[Steve]

Did you tap an oil feed between the block and the NVCS gallery?

[calaistur]

Yes the oil feed on the bottom of the head was blocked off and we tapped into the front of the head. This draws oil from a t-piece in the oil pressure sender line.

I have oil pressure, So i assume that the oil feed is also getting pressure.

[Steve]

Does the solenoid (in the side of the head) 'click' when the revs go above the point set for it to activate? mine does, but only when not in neutral (R33 with power fc, utilises a neutral switch).

Have you tested for voltage across the plug that goes into the NVCS solenoid on the head?

[Steve]

Also, have you tried loosinging the solenoid to see if you have oil pressure there? may be vapour lock?

[calaistur]

Also, have you tried loosinging the solenoid to see if you have oil pressure there?  may be vapour lock?

From what I have read, The solenoid is supposed to be activated from ~1000rpm to ~5000rpm at which point it deactivates or turns off. Is this right?

[Steve]

http://www.tomei-p.co.jp/_2003web-catalogu...haft-specs.html

that is what the factory sets it to, I have run these figures through dyno 2003 software with larger cam specs and came up with the same switch off point as being optimum - can definately tell the difference when its not connected:)

[calaistur]

Just to clarify. The VCT is "ON" or "activated" in the low rev range and then "OFF" in higher rev range???? So if we test the voltage at the solenoid at low revs it should measure greater than zero ?? and then in the higher revs it should be zero??

Just trying to get an idea of what is supposed to be happening so we can do some tests.

[Steve]

yep, switches on just above idle, then off at ~4500rpm. You should be able to hear the solenoid clicking as it comes on.

[calaistur]

Does it normally operate in Nuetral gear?? Could I free-rev the engine with the bonnet up and hear it?

I take it its quite an audible 'click'. So with the bonnet up on the dyno you should hearing it clearly?

[Steve]

I am not sure how it would operate with the LT8, mine only works in gear, must be set up with a neutral switch. I only noticed it because my car was hunting a little, and it made a sound similar to when a wire arcs out - so I investigated:)

[Craved]

does the stock ECU run the same neutral switch for vct?

[Steve]

At a guess, I would say yes.

The reason being, the power fc is basically a stock ecu that has been modified to allow adjustments to be made. I was told its acutally got an internal piggyback setup, that also allows other functions such as boost control.