Do the 5th Gen Maximas come with variable intake and/or exhaust? I keep hearing a change in the intake or exhaust noise when the car gets above 4500 or 5000 rpm. Maybe it's just my **shameful** past with Hondas and their Vtec engines. Just curious.

 

Grin, and grin with a huge freaking smile... yours does have variable intake. Not sure if the 2000 GXE has the variable exhaust (SE models have it for sure, including mine), but around 5200 RPM your Variable Intake (VIAS) should switchover to the high-end mode. I'm not sure if mine's working properly, 'cause I don't hear that transition...

 

I hear no transition, nor do I feel it. I, also, had a honda in the past ('99 TL), and the transition in that car was very apparent.

 

There is a huge, rather old thread somewhere about the VIAS on the 2000 models, and how some of them don't function properly. In some cases, it's possibly an internal issue with the manifold. I think that might be the case for me. But a new manifold is expensive, so I may consider inspecting the power valve and related components soon to see if I can come up with an answer or a fix.

 

It's a PIECE OF CAKE really to check.

Just remove the two screws(careful they're made of soft metal and are VERY very tight) on the PASSENGER side end, and pull off the cover. Then just flip the L-shaped power valve actuator rod under the VIAS box to see if it moves. If it does, put the cover back on...it's working. If it doesn't, then it just slides out and you can see what's broke.

The ONLY way it can NOT be rotating when you flip the L-shaped power valve actuator rod under the VIAS box is if it snapped off the key inside. Basically, it's one LONG nylon bar(power valve) with round O-rings inbetween each runner. However, on the end that connects to the L-rod under the VIAS box(drivers' side), there is a rotating metal circle with a slot that the power valve "locks" into.

Basically, the L-rod turns the metal circle, the metal circle turns the power valve. Not much to it really.

 

BTW, I'll take some pics tonight, so you can see what I'm saying.

 

Isn't this something that is very important to the power delivery of a car? Wouldn't something like this malfunctioning throw a code or do something other than a lack of the sound? Just curious.

 

that would be sweet. i wanna see what it looks like ...thx mr. moderator

 

Nope and dealers aren't even smart enough to figure it out.

Max_Gator had *TONS* of proof and they just said that it wasn't possible to not work...they had no clue really. They eventually gave in and replaced the COMPLETE manifold, which indirectly fixed the malfunction, ie the power valve/rod.

There are no sensors or code that would be flagged.

 

Check back in an hour.

I *THINK* this can turn this into ANOTHER mod. All you have to do is pull it out(easy) then shave it down a bit for better airflow. However, don't quote me on that.

 

Ice, I will try inspecting that for sure. One other thing I wanna inspect is this "vacuum check valve" for the vacuum tank that feeds the Power Valve. I wanna make sure it's working properly, so that it has adequate vacuum at WOT.
I haven't touched my VIAS stuff in a few months, but last I checked (last fall I think) I was stuck with knowing that the L-shaped rod does indeed move at ~5200 RPM under no load, but I never hear the "transition" when I'm actually testing it on the road at WOT, and I tried manually applying vacuum via the fresh-air port using a vacuum pump and did notice a reduction in low-end torque... therefore implying that the VIAS valves inside are working properly once given proper vacuum.

This is fueling my theory that my vacuum check valve isn't working properly. I think the VIAS works, and given proper vacuum works properly, but I don't think it's getting proper vacuum when I road-test it at WOT.

 

If the rod is moving then the vacuum check valve is working.

The only way the power valve is NOT turning, is if the end of it BROKE off, which honestly, I doubt happened. If it did, the engine ate it and you'll find it in your CAT.

 

We have variable intake runners on our 5th gen Maxima's but it's not like VTEC. We just have dual intake maifold runners. There is a long runner and a short runner. During low speed operation the long runner is open so for high velocity air speed for good tourqe. During high RPM operation the second runner opens up which is shorter and larger. It is the same as the intake manifold on the GSR.

A lot of Japanese cars have this feature, it's been around for over 15 years now. People with aluminum intake manifolds sometimes remove the runner separation but this will hurt performance unless you are making big power over the stock setup.

 

Here they are:

http://www.cardomain.com/memberpage/419735/12

 

Actually, you've been missing all the action:
http://forums.maxima.org/showthread.php?t=311222

Skip a few pages, but actually we don't.

 

I'm considering the possibility that the vacuum check valve isn't working, however ~5000-6000 RPM under no load does not require WOT, therefore under no load 5200+ RPM produces a situation where the intake manifold still has vacuum, enough to operate the Power Valve.

However, under load at WOT on the highway, there may not be enough vacuum available to operate the Power Valve even when the VIAS is switched on. Hence the whole purpose of having a vacuum tank w/ check valve--to supply adequate vacuum to the Power Valve even when the intake manifold vacuum is low (closest to atmospheric pressure) under WOT conditions under load...

Again, it's just a theory, one I need to investigate.

 

In neutral or on the highway, vacuum at XXXXrpm will be the same.

If you zip tie open the L-rod, it's mimicking the vacuum valve working.

Go for a ride and if the vacuum valve wasn't opening the power valve, I'm pretty sure you'll feel a difference. If it's moving at idle, it's going to be open when you do this.

If no difference, it could be working fine, so try disabling it, disconnect the plug, and go for a drive. If this feels the same, get a dyno.

 

how does the Variable Exhaust work and what purpose does it serve?

Is it better then a aftermarket exhaust?

 

The variable exhaust gives you a quiet sound at idle, as you excelerate pressure/vaccum? opens a valve that allows the exhaust to flow straight thru the muffler. This gives you a louder exhaust, but more performance due to less restriction.

 

Thanks guys. I really appreciate all the info. What a great forum!