Vct Help

[WMDC35]

Have a r33 25det motor with bolt ons

Can hear the vct click on just off idle as it should and if powered up directly hear the exhaust note change so seems to be working but driving the car with it unplugged or plugged in seems to make no difference?

Also on the dyno it seemed to 5/8ths of FA

I'm about to do cams so would be a good time to replace something if needed?

Any ideas?

Cheers

[GTSBoy]

So, to diagnose this properly, you need to get a test light and connect it to two probes jammed into the back of the solenoid's loom connector. Run leads back into the cabin so you can see the light come on, or perhaps just under the back edge of the bonnet if you can see it tehre while driving. Then just take it out for a spin. If you see the light come on then you know the ECU is doing its thing.

If you don't see the light, then you know that the ECU is not turning it on. This generally means that you aren't giving the ECU all the prerequisite signals to allow VTC to activate. These include;

• not being in neutral,
  
• vehicle speed signal >0,
  
• coolant temperature within limits (not too cold, not too hot - so do the test at normal operating temperature and you should be fine),
  
• in the case of a Neo, there must be sufficient load (ie at light loads it won't switch) - I don't know if this applies on old 25s though,
  
• Throttle not closed,
  
• revs within range (generally 1700<rpm<4700, although it seems more like 5400 rpm in Neos)
  

Some of these, like the neutral switch, are well known for giving trouble. Others shouldn't give you VCT trouble if you're not having other problems as well.

To troubleshoot most of the above, you really need to hook up a scan tool of some sort.

Now, if the ECU side all checks out fine, and the light is coming on, and you say that the car feels no different with the solenoid activated or not, then you have to wonder if there is a hydraluic problem. The oil side could be blocked up, or the solenoid could be jammed. Just because it comes on at idle doesn't mean that there's enough oomph available to make it move at higher revs. This would be bad, because it's harder to fix.

[WMDC35]

Cheers, I'm pretty sure it's not electronic and I'd be surprised if it's blocked because the motor is very clean inside, can hear the solenoid click fairly well so maybe at a guess it's the pulley itself, anyway of testing the pulley? the cams are coming out anyway so can put another one on at the time

I always thought the vct was a bit if a gimmick so I'll be happy if can gain something!

Cheers!

[KiwiRS4T]

VCT is no gimmick. Inlet cam is advanced by 20 deg which is substantial. Mid range power can be 10 - 20 kw more depending on your set-up. Do a run with it off and (when you get it working) with it on and see the different curves.

[Guilt-Toy]

So, to diagnose this properly, you need to get a test light and connect it to two probes jammed into the back of the solenoid's loom connector. Run leads back into the cabin so you can see the light come on, or perhaps just under the back edge of the bonnet if you can see it tehre while driving. Then just take it out for a spin. If you see the light come on then you know the ECU is doing its thing.

If you don't see the light, then you know that the ECU is not turning it on. This generally means that you aren't giving the ECU all the prerequisite signals to allow VTC to activate. These include;

• not being in neutral,
  
• vehicle speed signal >0,
  
• coolant temperature within limits (not too cold, not too hot - so do the test at normal operating temperature and you should be fine),
  
• in the case of a Neo, there must be sufficient load (ie at light loads it won't switch) - I don't know if this applies on old 25s though,
  
• Throttle not closed,
  
• revs within range (generally 1700<rpm<4700, although it seems more like 5400 rpm in Neos)
  

Some of these, like the neutral switch, are well known for giving trouble. Others shouldn't give you VCT trouble if you're not having other problems as well.

To troubleshoot most of the above, you really need to hook up a scan tool of some sort.

Now, if the ECU side all checks out fine, and the light is coming on, and you say that the car feels no different with the solenoid activated or not, then you have to wonder if there is a hydraluic problem. The oil side could be blocked up, or the solenoid could be jammed. Just because it comes on at idle doesn't mean that there's enough oomph available to make it move at higher revs. This would be bad, because it's harder to fix.

nice post dude.

Something to add to this, and i think it might be case on this guys issue because he said he has a RB25DET motor, not a R33 skyline...

So in engine swaps the speedo is rarely hooked up properly, usually because the cars they are going into have a incompatible speedo, or sometimes it is hooked up and the speedo is working, so all is good right??? WRONG...

Just because the speedo is working in the dash it does not mean that the ECU has got speed signal, and the ecu gets its speed signal from the back of the speedo!!! like a output to ecu.

So if you are to do a RB25DET swap properly you need to use the original cluster, and make sure the speed signal is getting to the speedo correctly and from the speedo to the ECU correctly.

Easiest way around this issue is to grab a plugin after market ecu, like a vipec which does not require any of those parameters to be met to enable vct.

if you do work out let me know which pin it is on the back of the speedo so i can hook mine up in the r32... too lazy to work it out myself, i dont need it for vct as ive got vct deleted cams, i want it for speed based boost control and slip based traction control

cheers

[WMDC35]

I agree, awesome posts! The car is a C35 Laurel Club S, the r33 and c35 looms aren't much different and almost plugs straight in

I'll try as GTSboy suggests for a kickoff, I know someone with a real time scanner so can make sure it's being controlled at the right times

It does make a resonant noise at about 1100-1200 rpm which I've heard many 25s do which I thought may have been the pulley starting to flog out like the sr's sometimes do, was thrown off this when heard a non vct 25de make exactly the same noise

I'm going to go and have a play with it now!

Cheers!!!

[GTSBoy]

You just have to make sure that the speed signal from the dash is connected to the right pin on the ECU. I put a Neo into my R32, and despite there being differences between the way the speed signal is generated between R32s and later Skylines**, the R32 speed signal is 100% compatible with the R34 ECU. It just needed to be wired correctly. I don't know what pin it is for R33 and C35, chances are it is different though.

There's a good reference to modifying the speed signal on the back of R33 GTR here. It's not directly helpful, but it does show the back side of the dash and what pins on the dash are involved. But you should be able to find the correct info off the appropriate wiring diagrams in the manuals with no difficulty. IN R32s, the speed signal wire from teh dash to the ECU is yellow/green with silver trace. I reckon it probably is the same in later cars too.

**R32 is cable drive to the speedo and the speedo head generates the 0-5V square signal that is sent to the ECU. R33 onwards have electronic sender at the gearbox, sends a low voltage AC signal to the speedo head. Speedo head converts that to the same 0-5V square signal as the R32 for the ECU. It's all good. In my car, the speed signal at the ECU reads exactly the same km/h as shown on the speedo itself.

[AngryRB]

My Power fc lights up the VCT at just over idle and in neutral, does that sound right?

[Hanaldo]

My Power fc lights up the VCT at just over idle and in neutral, does that sound right?

It shouldn't happen in neutral...

[GTSBoy]

Actually, the VCT will switch stationary when revved in neutral. My Neo does it.

It would be great to get a full disassembly of the program code to see what all the rules are!

[JonnoHR31]

yer power fc does it regardless of speed or gear. i dont have the speedo or neutral switch hooked up and it works fine

[WMDC35]

Electronically mine seems to function as it should, (switches in neutral also) I'll check the mechanicals when the cams come out, just found this is for sr but some of the basics are covered in general

zilvia.net/f/.../238600-s14-sr20det-vvt-problem.html

cheers

Edited April 22, 2012 by WMDC35