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Rb25/30 Rb30det Vvt Internal Oil Control

psi

By psi,
in Engines & Forced Induction

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  • 2 weeks later...
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fletch rb30
fletch rb30

33 and 34 vct activation is different. On 33 heads, the oil constantly feeds the front journal to lubricate it. The oil leaves the journal via the vct solenoid into the head. When the vct engages the

daisu
daisu

Just to get an idea of how it works, is this what is happening with the oil feed?

psi
psi

I've heard of a few plugs that refuse to play the game. I thought I would have that issue and got some brass just incase.. If you do break or mangle it, you will have to make a copy. Nice pics

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dave1200 Collaborator

dave1200

Posted
Posted

Guys I've had a closer look at the neo head now and I've gone with the external oil feed solution. I was about to try drilling through from the oil gallery for the lifter but decided against it because I reckon that the VCT will be calibrated for operation on nominal pump pressure from the block. I'm just not 100% sure that there won't be some pressure loss down that gallery feeding the lifters with all the points of loss at each lifter and don't want the VCT doing strange things.

I just think there must be a reason that the nissan engineers decided to run a standalone oil supply to this rather than using the existing head supply.

  • Like 1
dave1200 Collaborator

dave1200

Posted
Posted

It's not that surprising at all since it's a pressure actuated mechanism. The oil supply to the lifters is seriously restricted already (see oil control stuff) then is opened out into a ~15mm gallery that feeds oil to all the lifters. It may work OK on the R33 on/off VCT but I reckon it's unlikely to work perfectly on the Neo head with the variable degrees of advance/retard.

Ben C34 Grand Master

Ben C34

Posted
Posted

It's not that surprising at all since it's a pressure actuated mechanism. The oil supply to the lifters is seriously restricted already (see oil control stuff) then is opened out into a ~15mm gallery that feeds oil to all the lifters. It may work OK on the R33 on/off VCT but I reckon it's unlikely to work perfectly on the Neo head with the variable degrees of advance/retard.

The neo vct is either on or off, no variable.

dave1200 Collaborator

dave1200

Posted
Posted

The neo vct is either on or off, no variable.

I see...so what is the function of the oil? I'm not game to pull the gear apart in case it's full of complex little bits? I assume it's always in the nominal position for high revs and in the low revs is releases oil to the mechanism that rotates the gear relative to the camshaft. If you didn't have an oil mains pressure supply could it half actuate or not actuate at all?

The Mafia Grand Master

The Mafia

Posted
Posted

the solenoid actually stops the oil AFTER the gear. What this does is pressurises it and pushes it / makes it rotate inside.

Thanks my understanding anyway.

When the solenoid opens, it releases the pressure and a spring returns the cam to the normal position.

Please correct me if I am wrong.

It indeed does need pressure.

dave1200 Collaborator

dave1200

Posted
Posted

the solenoid actually stops the oil AFTER the gear. What this does is pressurises it and pushes it / makes it rotate inside.

Thanks my understanding anyway.

When the solenoid opens, it releases the pressure and a spring returns the cam to the normal position.

Please correct me if I am wrong.

It indeed does need pressure.

Pretty sure this is wrong. The oil supply quite clearly comes up through the head from the block, passed the solenoid (depending on its state) then to the cam.

fletch rb30 Enthusiast

fletch rb30

Posted
Posted

33 and 34 vct activation is different.

On 33 heads, the oil constantly feeds the front journal to lubricate it. The oil leaves the journal via the vct solenoid into the head. When the vct engages the solenoid blocks the drain which pressurises the pulley and advances the cam. The semi constant oil drain from the front journal is the reason for the oil drain in the front of the 33 vct heads.

If you look at the head and the cam you can see the oil holes are in line and it lines up with the groove in the cam which is ported to the cam pulley

On the 34 neo head, the front journal lubrication comes from the same main gallery as the rest of the cam bearings.

The vvt solenoid has its own feed which is closed when the vvt is off. when it turns on, it feeds pressure to the grove in the cam which activates the vvt pulley. When it turns off, it shuts the oil feed from the block, and vents the oil pressure in the pulley to the head.

If you look at the front cam journal you will see the same 2 holes as the 33 head, except they are not in line, and the grove in the neo cam lines up with the oil hole from the solenoid only.

The advantages of the 34 system are the cam journal is always fed with pressurised oil like the rest of the journals, and the vvt only discharges a small amount of oil into the head when the vvt switches off, instead of the constant loss of the 33 system.

This also explains why a few people here and there who just block off the vvt on their 33 head and run an rb20det or similar cam, seize the cam as there is no dedicated lubrication to the front journal.

sorry no photos on hand to show what i mean, and couldnt find them on google

  • Like 2
dave1200 Collaborator

dave1200

Posted
Posted

Good call, I've ended up with the head that the internal mod was done on (mustn't of been used until I got it). But it didn't work, seems like not enough pressure to engage the vct, so I just got rid of it completely

I've been thinking a little more about this; how would you know that it wasn't working? Your ecu could be actuating the solenoid but if your oil pressure is insufficient to actuate the cam then I don't know how you'd know? Unless you had previous seat of the pants experience with the motor or another car with similar specs to compare against? It's not like a light comes on in the dash when camshaft is advanced?

Huzqld Enthusiast

Huzqld

Posted
Posted

Because I did numerous tests on the solenoid, also hooked it up so it would come on with a switch to test at idle, note of engine didn't change at all. Did numerous dyno runs with it on/off and different rpm switch points, no difference.

even pulled the bolt that lets the oil through to vct gear out and replaced with a Solid bolt still no difference.

I don't think it was working.

Could be wrong

steve200b Proficient

steve200b

Posted
Posted

Because I did numerous tests on the solenoid, also hooked it up so it would come on with a switch to test at idle, note of engine didn't change at all. Did numerous dyno runs with it on/off and different rpm switch points, no difference.

even pulled the bolt that lets the oil through to vct gear out and replaced with a Solid bolt still no difference.

I don't think it was working.

Could be wrong

Must of been another issue. I have done the internal mod and been working fine for 1 year. Full vct function through boost street
  • 5 months later...
devilsknife Collaborator

devilsknife

Posted
Posted (edited)

hey guys sorry to bring this back up but as im building one i thought i might ask ive attached a picture with my head and was looking at the core plug #1 and was wondering on the other side of it if i was to drill it to provide oil to vct off the main bucket gallery's

also i couldnt work out how to add the pix sorry

Edited by devilsknife
  • 5 months later...

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