Well heck I spent the $1 and 5 min and just did the VTC rewire (grounding the green/yellow VTC input wire). No more annoying ticking and surges/loss of power while accelerating. However, it's not a miracle fix. It seems to me that although the bottom-end torque stayed constant, the high-rpm power is a bit less than what i've felt before.

My Nissan service manual says when the VTC valve is off (I am assuming it's off when the wire is grounded!), that the cams will have cause overlap and duration, which would help out high-end power, correct? The VTC opening is supposed to help LOW-end power by creating GREATER duration and valve overlap.

It's just odd to me that the seat-of-the-pants meter is saying the direct opposite. Any ideas, comments?

 

That is correct, what you might want to do is advance your ignition timing 2-4 degrees. However this might take away even more toppend power. Look at this way now you have a VG torque curve minus the VE toppend.

 

First of all... I mean to say LESS instead of CAUSE

(My Nissan service manual says when the VTC valve is off (I am assuming it's off when the wire is grounded!), that the cams will have "LESS" overlap and duration, which would help out high-end power, correct? )

Second, that's why I'm confused. The VE top end power is caused by what? The VTC system, right? Well in my service manual, it has a higher torque curve at higher RPM's when the VTC system is OFF, which is what the grounded wire mod should have done. So I was expecting to lose a bit of low-end power while keeping the high-end. Where in fact it feels like the opposite happened.

Anybody get what I'm saying?

How exactly does the camshift switch? Is there a second set of lobes, or does the cam just rotate a bit?

 

When the vtc is "on" it is suppling oil to the vtcs and keeping the cam in retarded mode. When you reach a certian rpm ie.. 3300 rpm, it switches "off" and no oil is going to the vtcs. This allows the intake cam(only) to advance up to 8-9 degrees. This also increases the overlape between the intake and exhaust cams. I hope this clears the confusion.

 

Alright, so basically I am running around with the intake cam always advanced, which is why high-end is lacking a bit, since there is too much overlap. We'll see what this does to my gas mileage (currently about 330 per tank).

 

No I think your running always off, which means always advance. So your high end should not suffer. I don't know why your car does that. More overlap usually means better high rpm breathing.

 

Ok well I only drove the car a couple miles. I'll have more feedback tomorrow then

 

According to my FSM when the VTC solenoid is off the valve overlap is decreased. Also it says the VTC's are off at idle and high engine speed, plus the intake valve timing is retarded. Technically if the VTC were in the off position then he should have lost low-meduim speed torque, but his high speed torque should be the same. It also says in the diagnostic procedure that when the ignition switch is on that battery voltage should be between VTC terminal A and ground. What I'm thinking is that the VTC's were grounded in the "ON" position. So instead of the VTC's getting batt voltage after say 4500rpm they were grounded to only get the 0.2-0.5V that they use to stay on. I don't know if this helps but at least you got rid of the noise.

 

Well, I did the mod also...about 2 weeks ago...it got rid of the noise and the power loss....and now it runs much better, however, I will say....it feels like it has all the low end power that it should, but between 5,000 and 6,000 rpm it feels like it looses power, and right at 6,000 it sorta comes back again...gains some power....so theres a weak area in the range and its 5000 to 6000, so theres a whole 1000 rpm area that seems like it "lags"....as far as gas milage....I just drove 215 miles on a 1/2 tank and I was on the highway the whole time at 75mph.

Matt