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Rb25Det Vvt Problem

WalkyHR31

By WalkyHR31,
in Engines & Forced Induction

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WalkyHR31 Enthusiast

WalkyHR31

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Guys,

I need you help please. I have a loud whirring noise that has appeared in the inlet VVT cam wheel when opening or closing the throttle but goes away if I hold the throttle open at constant revs. It is a Series 1 engine.

I know its the VVT as it disappears when I disconnect the lead off the solenoid. I have 2 spare VVT units and have tried each and the noise is in all three. I also have a spare solenoid that I changed and same again - noise still there. The power to the solenoid is working with no voltage below 1050 RPM and full battery voltage from there to 4700 when it turns off again. I checked the oil feed thru the front cam bearing and all looks OK. ECU is a Z32 with Nistune board.

Can drive it Ok with VVT disconnected so I took it to 2 engine specialists who build RB's and SR's and neither of them could tell me what they thought it was however, another SR20 specialist builder thought it may be that the spring inside is weak allowing the helical gears to rattle but surely not in all three units!

Any ideas please as it has no mid range torque with it disconnected and is not much fun to drive plus I need to find out what it is so I can fix it. I build my own engines and can normally solve all issues like this but not this time. Anyone experienced this problem before and had if fixed or can recommend someone who would know I can go to?

Also I can't find any info on how the internals of the VVT unit work. I know how it is activated and what it does but not how it works internallyl (i.e. how it advances the cam once oil pressure is applied). I also can't see how to pull it apart to find out without cutting it open as it all appears to be sealed.

Thanks, Brett

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WalkyHR31 Enthusiast

WalkyHR31

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Yes, definitely installed correctly as per your description as I have done it many times. The noise appears to be coming from the gear as I have run it with the timing cover off and the cam cover off too.

Timing belt is a new Gates blue racing belt. Does not run a mechanical water pump but a DC EWP so that's not it. Tried changing tensioner and idler with spares I have and that's not it either. Engine has been in the car for 9 months and done 5000 K's so not something I have just installed.

What I haven't done as yet is checked the actual delivery of oil to the unit thru the bolt hole although the solenoid is working OK. My next step would be to take the cover off the VCT unit and crank the engine over with the solenoid open to see what sort of oil delivery there is to the unit. I feel it has to be something to do with the operation of the VCT as it is the same noise when I try all 3 units that I have. What do you think?

89CAL Grand Master

89CAL

Posted
Posted

Hmmmm it would be odd to be an oil feed issue, but not impossible. From memory, the oil goes through the front cam cap on the intake cam side? Maybe rip the cam cap off and have a look. I'm not 100% on this but for some reason seem to recal something went on in the front cam cap

WalkyHR31 Enthusiast

WalkyHR31

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Have already taken the front cam cap off and checked the two holes in the cam and bolt and all clear. Can't imagine why it would be an oil issue but something is not working right and making the noise. If I could only find out how the internals of the VCT unit work I may be able to work out the problem.

I have Googled it but can only find info on what makes it work (oil pressure) and what it does (advances cam) but not how the internals work. The guy I left one of my spare units with to try and dismantle it hasn't done it as yet and doesn't even know if he can disassemble it. I have the Nissan Factory RB engine manual (480 pages) but it doesn't go into any of that, just how to take it off and put it back on the cam. Any ideas on that or where I could find any info?

Thanks for your help with this.

WalkyHR31 Enthusiast

WalkyHR31

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So I've had a look at the SAU thread on gates timing belt problems and it isn't any of that. I put this gates belt on 5 months ago and had no noise issues at all.

The loud whirring noise I am experiencing only started a couple of weeks ago and only occurs when the VCT is activated as I explained in my first post, so can't see how that would have anything to do with the belt, which I have retensioned each time I separately changed the 3 VCT units, tensioner, idler etc to test (about 6 changes).

This is driving me mad....Grrrr!!

WalkyHR31 Enthusiast

WalkyHR31

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Yes, it is but that's a good explanation. All the dots on the cam wheels and crank wheel line up with their covers and I have done this many times without a problem. Remember, this only happened after the engine had been running for some months so I assume if it was anything like that it would have made itself apparent the moment I started the engine when I first installed it and if I hold the revs at a constant level (e.g. 3000 RPM) then the noise goes away so I don't think it could be that as any interference would be there whilst the VCT is activated irrespective of the throttle position. It's only there on throttle open (revs building) and throttle close (revs reducing) so its got ot be something to do with the VCT unit.

If only I could find out how it works internally I may be able to solve it but I can't find anything on that.

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