R34Neo Vct Not Functioning

[rondofj]

Hi all,

Just had an inspection at Unigroup (GTT, Precision 5558/0.63, Nistune, EWG, usual support mods).

Reason was lack of low down torque below 2500-3000rpms, loud groany farty note, gutless POS incosistently and missfire under WOT past 5000 rpms usually only when hot 90% of the time. Shocking fuel use

18-20L/100kms everyday driving with ocassional short hard squirt.

Yavuz mentioned that my VCT is working mechanically, gets power, but doesn't send the signal to the ECU or the ECU is not able to interpret the signal hence VCT doesn't work. He didn't have the time to find what it was - a wire in the loom or something else as he had other cars booked in. But he did pinpoint the lack of VCT signal intepretation by the Nistune.

Further he said he has had many many problems with Nistuned cars, notably Skylines and R33s & 34s, as well as many cars where Nistune works great. On my car he said its been acting funny with the VCT and the other thing is it doesnt have a boost cut. Further, its been tuned previously by someone else to the last load points on the software and he couldn't increase boost from the current 18psi to 22-23psi. If he was to do that he has to rescale everything and start ll over again. I was surprised that him and Mark has had many issues with Nistune in the past.

Hence he has asked me to consider going a Power FC (I know its old tech but easy to tune) or if I want to go Flex Fuel in future, to look at a G4/Haltech or something. Doesn't really recommend Adaptronic. But flex fuel would be even bigger injectors, E85 pump, sensor, lines, expensive ECU, tune, too much $$$$.. So not heading that way for now.

What is everyones thoughts, esp regarding the VCT and Nistune or new ECU/which one? Is it a simple signal wire from ECU loom to solenoid that I can cut and replace/rule out; what else can it be?

Further it made a miserable 260rwkw at its current state on the Unigroup dyno (due to the issues I think), when it was running ok it did push out 286rwkw on JEMs dyno, its kinda tuned on the edge with timing. Its a real crappy car lol

Edited December 6, 2013 by rondofj

[Dose Pipe Sutututu]

Send STATUS a quick note or PM, I recall reading a few years ago that he had similar issues and resolved somehow.

It seems Nistune has issues with RB25s, on R33 using Z32 16-bit ecu is a fail, and on R34 there are memory leaks etc. however seems to work flawlessly on SRs

[GTSBoy]

There is no feedback from the VCT to the ECU. The only interface between them is that the ECU switches on or off the output and the VCT solenoid does its thing. If the ECU is not outputting the signal to activate/deactivate the solenoid, then that means that something that the ECU wants to see as a requisite condition is not happening. These things include stuff like vehicle speed sensor must be working (which is the square wave speed signal from the dash to the ECU, not the saw tooth signal from the gearbox sender to the dash - so having your speedo working is not proof that the ECU is receiving a speed signal). There are other conditions also.

So, just to recap, in Nistune, if when you are driving and you reach a point where the VCT output flag should be lit up and it isn't, that IS NOT an indication that there is no feedback. It is an indication that the ECU is not activating that output. And there must be a reason for that. And that reason will be a fault on one of the other inputs to the ECU.

[rondofj]

Jeez thanks guys - had to read that one up a few times GTSBoy, now its kinda dawned on me what you really mean lol.. And it could be a few things (inputs) causing the ECU to not be activating the VCT output..

Any advice on what I should be doing/things to test/rule out?

cheers

[GTSBoy]

VSS, TPS, AFM, neutral switch. The R34 ECU looks to see that you have positive speed, load over a certain value and TPS over a certain value. Then, once you are within the rpm window for the ECU to activate the output, it will. If any of these inputs are faulty, in that they read the wrong sort of value at the wrong time, then you won't get VCT. Note that it is hard to get yourself into such a situation.

The VCT will come on if you free rev the engine in neutral and stationary. I think this is what the neutral switch input to the VCT logic is all about. Allows the VCT to be seen operating with the bonnet up. But when driving in gear, neutral switch is off, and then it needs load signal and non zero VSS to make it happen. Also TPS I think.

Note, that all of the above has a layer of "I don't really know" over it, because it's a bit arcane trying to work it out. For example, the neutral switch in my gearbox is not working, but I still get normal VCT operation when driving. In theory there should be at least something wrong with that, but it still works. Dunno why.

[Rolls]

Put a multi meter on the ECU and see if it is turning the VCT on, if it is then it is a simple wiring problem, if the ECU is not outputting the signal then something is wrong in the ECU, could be an electronic fault but more likely the settings are f**ked up for some reason in the nistune software meaning it never turns on, it should be pretty easy to check the constants in nistune to confirm this though. If that is ok then it could be a burnt out mosfet on the ECU, though that would be unlikely.

Worst case if you have an eboost street or eboost 2 you can use that as a window switch to turn the VCT on, though would be preferable to get the ECU working.

Misfire past 5000 rpm is due to the common rich misfire which is a combination of bad spark (old plugs and overheated coilpacks with burn marks on them) coupled with running too rich most likely from a poor tune or an air leak turning you good tune into a bad one as air leak on boost means you measure more air than you are getting in, hence a rich condition. Reality is probably all 3 of these things are causing it, check the AFRs, if rich then smoke pressure test the intake, then check the tune, then replace plugs and check coilpacks for arcing (blue burn marks).

[rondofj]

Thanks mate. So what do I look for in the multimeter test- which pin of the ecu and how many volts? Do I not just put a test light to the end of the vct signal wire on the loom ( it needs to be plugged to vct solenoid to do this, right??) And rev past 2000rpms.

Well I found that it works flawlessly sometimes and sometimes doesnt. When I reset the ecu by taking off batt terminals n draining charge then reconnecting, the vct worked perfectly ( much more low down, much softer sound, noticeably easier spooling and better boosting, much more kick and revs smooth n quick, power everywhere). Earlier when the vct wasnt working I found the solenoid plug wasnt connected, so with the engine idling I connected it and bingo it worked and was a different car. Worked as it should for two days and then stopped working after. The engine note becomes louder n groany when not working and theres no power low down and mid- becomes a real pig to drive.

Its really bugging me, after resetting the ecu yesterday I expected it to work without fault from then on but today it became a bit of a pig again. Yesterday it was beautiful though, perfect.

[Rolls]

Thanks mate. So what do I look for in the multimeter test- which pin of the ecu and how many volts? Do I not just put a test light to the end of the vct signal wire on the loom ( it needs to be plugged to vct solenoid to do this, right??) And rev past 2000rpms.

Well I found that it works flawlessly sometimes and sometimes doesnt. When I reset the ecu by taking off batt terminals n draining charge then reconnecting, the vct worked perfectly ( much more low down, much softer sound, noticeably easier spooling and better boosting, much more kick and revs smooth n quick, power everywhere). Earlier when the vct wasnt working I found the solenoid plug wasnt connected, so with the engine idling I connected it and bingo it worked and was a different car. Worked as it should for two days and then stopped working after. The engine note becomes louder n groany when not working and theres no power low down and mid- becomes a real pig to drive.

Its really bugging me, after resetting the ecu yesterday I expected it to work without fault from then on but today it became a bit of a pig again. Yesterday it was beautiful though, perfect.

Check there are volts at the VCT solenoid, simple, check volts across it, is it 0v or is it 12/14v ? You should hear it audibly click if it is, you shouldn't even need the multimeter as it is very loud.

Resetting the ECU is not diagnosing anything, it is just guess work, check it properly with a multi meter. If the engine note gets louder it sounds like your timing is being retarded or something else is going wrong, the VCT should not make enough of a exhaust note change for you to hear it, I think you are chasing a different problem, is it only on cold start? Plug in ecutalk and see if the timing is being retarded, sounds like it might be running on the knock maps.

Ultimately it sounds like you don't have the tools to figure this out on your own so I would recommend taking it to a workshop who deals in skylines, sounds like you have quite a few problems, print off this thread and take it to them.

[rondofj]

Cheers mate I did, Yavuz at Unigroup has been through it few weeks back, confirmed that the ecu isnt sending the vct signal (read up a few posts), mechanically its workin n its getting power, he didnt have the time to exactly pinpoint the cause but confirmed that Nistune has been known to cause this type of problems on many R34 and R33s. Bit of a hit n miss according to him, he suggested me to go a pfc and retune, but thats just more money for not much gain- hence Im lookin at finding the cause-- I will however be touching base with him shortly when they re-open next year. And yes u right its going onto the 'crap' maps sometimes- thats how it feels when driving

[Rolls]

Oh so the ECU isn't sending power, sounds like an issue to ask the nistune boys over on their forum, matt and pete would figure it out for you, http://forum.nistune.com/

[GTSBoy]

Nistune doesn't send power. Like most such actuators on an engine, switched by an ECU, the ECU switches to earth.

[Rolls]

The point is the same, the mosfet isn't switching.

[GTSBoy]

Yuh. Worst case it's not an ECU change (to a PowerFC or anything else)....it's just a window switch of some sort required as an add on. Otherwise you could source another R34 ECU (I have one here modified and ready for a Nistune board if someone needs) as a test to see if it's the output that's faulty. I don't believe that it is an inherent problem with Nistune itself.

[Rolls]

I'm guessing his settings are wrong, download your tune and post it up on the nistune forums, they will do their best to fix it.

[darkhalf]

Received an email today with a link to this forum thread so responding here....

Reason was lack of low down torque below 2500-3000rpms

What was the cause of the loss of torque low down compared to factory? See my dyno graphs here (R34 with GT3071) with no loss in torque using Nistune

http://forum.nistune.com/viewtopic.php?f=2&t=950&start=15

missfire under WOT past 5000 rpms usually only when hot 90% of the time

Sounds like coils. Separate issue, but once you start winding up the boost any problems with coils will start to surface

Yavuz mentioned that my VCT is working mechanically, gets power, but doesn't send the signal to the ECU or the ECU is not able to interpret the signal hence VCT doesn't work.

VCT goes from the ECU to the solenoid. There is a VCT indicator inside Nistune which indicates when it is active. You can also trigger VCT from Operations > Active Test > Valve Timing Solenoid inside the Nistune software. This is covered in the documentation and would have taken 2 minutes to check...

Further he said he has had many many problems with Nistuned cars, notably Skylines and R33s & 34s, as well as many cars where Nistune works great.

Okay well I havent heard of anything from Unigroup directly to address and resolve issues for them. My email is available daily and mobile is available on request (I used to list it on the website until overseas customers started calling me up at 2am in the morning...). Most other workshops I've spoken to have only mentioned warm crank start issues with R34 when using larger injectors which I am looking into currently (there are 5 cranking tables which are conditionally used on this vehicle)

R33 issues previously identified were due to false positive knock sensing (which has been disabled using 470K ohm resistor) due to the Z32 ECU not matching the R33 knock sensor. Also 16 bit ECUs which had been previously attempted are shown to have issues so we state only to use 8 bit ECUs

other thing is it doesnt have a boost cut.

Load Cut (TP) is an airflow based fuel cut in the ECU. This is what the Japansese tuners refer to as boost cut. This ECU is confirmed to have it (and I've verified it works on my vehicle)

he couldn't increase boost from the current 18psi to 22-23psi

When tuning the vehicle you do your scales based on maximum TP (airflow) based on the target boost level, after this tune your AFRs and then your timing. Having to change the boost levels would require rescale and retune. Increasing above 18psi is fine but you may need to increase the Boost Limit TP and Boost Limit TTP parameters

I was surprised that him and Mark has had many issues with Nistune in the past.

Pete (PLMS) interfaces with Unigroup more than myself but I havent heard any feedback. If they are having issues then call me to resolve since I'm more than happy to help (and this is my full time job now). I'm planning on a NSW visit early this year for training so it may help workshops who are getting stuck in a few areas

....

Okay I've read the repsonses above and they are correct that the ECU needs all valid input signals. One dodgy input (or fault with component inside the ECU) can cause issues. Taking a log of the problem (using consult or Nistune software) and watching the VCT signal is the best way to diagnose if the problem is intermittent

I think the rest is best resolved via email (or our forum). The reason for this is because there are many different vehicles (and forums that people belong to) for those vehicles. I obviously cannot track every single thread on multiple forums resolving issues so I mainly resolve issues via email or forum or phone... and only those methods

[rondofj]

Hi Darkhalf, got your email and many thanks for the above response. I have replied to you :

"Hi Pete, thanks so much for the help, saw your post on skylinesaustralia forums, I might call you soon to discuss - all the other problems mentioned above of misfiring etc; have been solved - that was my coil packs - the issue is the vtc not working, and from what I gather from you:

"VCT goes from the ECU to the solenoid. There is a VCT indicator inside Nistune which indicates when it is active. You can also trigger VCT from Operations > Active Test > Valve Timing Solenoid inside the Nistune software".

So will this solve the vtc issue?? - I gather it needs speed signal, load and temp to be activated.."

[darkhalf]

emailed...