93SE5speeder

Soooo, can anyone tell exactly how the VTCs for the VE engine functions? The FAQs explanation really doesn't give the nitty gritty of it before wading into the "this is how you fix it". I understand there are solenoids (basically on/off valves on the oil galleries leading to the VTCs (and that you can "ground" them to keep the VTCs from ticking you into insanity). I also understand that the VTCs are "spring loaded" and will rotate the intake cams to improve power at higher (<3000) RPMs.
Specifically:
1)Does the oil pressure (which is turned on/off by the solinoids) work "against"(or with) the spring pressure to affect cam rotation.
2)Are the solenoids in a normally open or closed position at idle and low RPMs?
3)Does grounding the solenoids cause them to remain open(or closed)?
4)Does the spring pressure keep the cams in a normally retarded(or advanced) position (supporting low or high RPM power)?
5)How does oil gallery "clogging" cause VTC failure? Is it a direct effect (no oil - wrong VTC adjustment), or indirect (no oil - spring degradation)?
6)What is the VTC failure symptom (tic, tic, tic...) caused by? Is it the VTC cams oscilating and banging within the VTC, or is it from valve on valve seat "mis-adjustment" (closing too fast/far)?

Maybe perhaps a discussion of solenoid, cam rotation, oil pressure, etc.. status under each of the following conditions would help; idle, off-idle/low RPM, high RPM - part throttle, and high RPM full throttle? I'd appreciate your help, as I'd really like know.
Thanks in advance!!!!

Jeff92se

iTrader: (82)

If by reading the VTC information that I wrote isn't enough, then you would have to get a Nissan Service Manual for deeper technical references.

Matt93SE

iTrader: (44)

As Jeff said, all of that is described in great detail in a factory service manual.

eric93SE

iTrader: (1)

1) when the solenoids are energized they work against the springs. the springs are for when the solenoids are disengaged and act the bring the sproket into the unadvanced position.
2) The solenoids are in the normally closed position during idle. The problem is that the springs arent strong enough to bring the assemblies back into the unadvanced position.
3) grounding the solenoids turns them ON, and there by putting the sprokets into the advanced position.
4) Yes the springs are used to put the sprokets in the unadvanced position (but its not considered normally retarded, it is simply the engines 'normal' timming). At idle the vtc's are off, then they switch on during a good load and all the way up to around 4500rpm? I forget the exact rpm that they switch off again, this is the top of the rpm range and the engine will then have its natural torque peak (vtc are off, and the spring is trying to bring the assembly back to its unadvanced position).
5) Oil gallies cloggin may be due to the fact that the vtcs are off during idle, since the oil does not circulate at idle it is trapped in that position, also since VE engines are known to run hotter the chances of oil baking on and creating a varnish over time will lead to build up. This will be even worse for those of us who do not change the oil more regularly, switching to synthtic oil may help.
6) The noise mainly comes from the VTC area and not the valves, so its probably the sproket assembly are oscillating back and forth. Only a few people have had a catastrophic failure where parts have broken within and created havoc.

CandiMan

iTrader: (1)

Damn for a newbie you sure asked some detailed questions
Hopefully your questions were answered. I haven't read the VTC sticky lately so I'm unaware of what info is in there. FYI a new/better design VTC assembly has a stronger/bigger spring to help with the spring degradation issue. Also if you purchase a rebuild kit it also comes with a stronger/bigger spring. Now go stop that ticking.

93SE5speeder

I truly appreciate the response. I have a 93 SE (5 speed) with 204K miles (original owner). I've used Valvoline 5W-30 pure synthetic since 3K miles, changing it every 7K-8K. Still doesn't use ANY oil between changes. Never had the engine apart, but it just started ticking a little. Symptoms are odd though, on first start-up - no ticking. After 10 minutes it starts ticking after idling for 10-15 seconds, after 15 minutes run time - no more ticking. I was trying to get some details on VTC function to try and figure out if going to a heavier weight oil would help. Sounds like it may not. Actually sounds like the springs in the VTC are starting to get marginal and during the warm up cycle there is period of uneven thermal expansion where they're not quite adequate. (any other theories are welcome here).
I appologize for the approach to the tread - although asking the question straight out ( how do the VTCs work?) would have gotten me flamed.
I'm mechanical engineer by trade, motorhead by desire. The Maxima has been my daily driver for 10 years, and I haven't wanted to mess with it too much (I have '73 'vette convertible for that).

Again I truly appreciate the responses - you've been a lot of help.
Regards!!!

eric93SE

iTrader: (1)

Well doing the VTC job isn't said to be all that bad. Getting the rebuild kit and all the gaskets, and following the technical service bulliten will get the job done right. It would also be a good oportunity to replace all the valve stem seals(maybe do a compression test to see that all is okay). I'm sure you'll easily get another 100k out of an engine thats been well maintained.

-Eric

93SE5speeder

I was thinking that I would just run a ground wire off the solenoids (per the instructions) through a switch mounted inside the car to ground. That way I can (cheaply) eliminate the ticking when I want to and still have that extra 12hp most of the time.

I really haven't had to put anything into the car since new, and am trying to keep it that way since I only plan on keeping it another year. Other than regular PM, I've only had to put in an axle/CV joint (@90K), Tokicos (@150K), battery (@175K), and a water pump (@180K). (yes - the original clutch, exhaust, starter/alt and everything else are still working great!). I gotta love Nissan!!!!

I don't know how much a real clean 93SE 5-speed (w/ 204K miles) is worth with perfect VTCs versus one with a switch to eliminate the tick. If you really think I could get my money back when I sell it in a year, it might be worth taking on the VTC repair. Any input is welcome.

Jeff92se

iTrader: (82)

VTCs are a very large pain in the butt. I just got done breaking down my old motor and was reminded what a pain it is to get to the heads etc...
Plus, unless there's some good way to run compressed air though the sparkplug hole, the heads have to come off to replace the valve stem seals. But even them, both cams have to come out.