Thanks for the information. I saw the same thing on my ODBII scanner.

I removed the duct simply as an experiment. I absolutely loved the sound. It is far deeper sounding than just the Z-pipe and almost makes it sound as if you have an exhaust. At part-throttle, the induction noise is very tame. I went ahead and added some black pipe insulation foam around the intake box lip to clean up the look. It even uses the OEM pop-tabs. For someone that doesn't own a G, they'd think it was OEM.

At the track in May (70s, fairly humid, 1500' density altitude air), I ran a 14.49@97.59mph with a 2.19 60', a 14.6@97mph (slow 60') and a couple 14.5s. My only mod was the Z-pipe.

In November (40s, dry air, sea level density altitude), I ran a 14.32@97.79mph with a 2.15 60', 14.38@98mph, and a handful of 14.4s@97-98mph. My mods were the Z-pipe and no Power Duct cover. No, I do not think the lack of the Power Duct cover made my car faster. It was clearly the better air. That's it.

 

The best times I've recorded - a 14.2 @ 97.2 with a 2.21 60'was actually with the Injen. However last summer I pulled on a Z and beat him after a bad launch with a heat soaked power ductless car that ran a 14.5 @ 95.x with 2.29 60' during a hot humid June day. G35 X's were running @ 90 that day so I felt OK. Hard to compare two different days, not to mention different tracks.

The Z tubed, Power Ductless, Mid Piped and Crawford Catted Car sounds like an awesome machine at Idle and under heavy or WOT. Kind of M3 like - it's sings at 4000 rpm when you nail it. I can't keep my foot out of my car.

 

That's why most serious drag racers correct their times for density altitude.

Here is a link to solve for your density altitude:

http://www.modulardepot.com/density2.php

This takes many of the variables out of the track times by racing on different days or even different track elevation levels.

Here is a link to find your track elevation:

http://www.racefan.com/racetracks.asp

 

Cool, thanks for all the feedback guys I just bought the K&N Filter yesterday and ordered the Z-Tube today. How's installation? Pretty easy? :crosses fingers:

 

Yup...pretty easy. You should search for & find the DIY instructions (not sure where they're posted), but someone had step by step w/ photos on how to do it (that's what I used). Enjoy!

 

Ohh, thanks! Can anyone redirect me to that link of the DIY? I've done a couple searches but haven't found any with pictures that work. Only found one with a ton of pictures from DaveB but the pictures seem corrupt and don't show correctly...

 

Gee..I typed in "Z tube install" in the search function and found a thread that had this link pasted in it ............ (BTW...this is the exact install instructions that I used): http://www.6mt.net/mod-g35-350z-intake.php

 

Well you intrigued me, so I removed the power duct to see what it was all about (took all of 30 seconds w/ the handle of a screwdriver on the inside of the intake box). Definitely noticed a lot stronger/louder noise from the intake/Z-tube under WOT in the 3K RPM and up range! That was the only audible change I noticed (idle & normal acceleration remained the same). Thanks for the tip!

 

You have plenum, coupe midpipe, exhaust and you can still hear the difference? Must be quite loud then... When you leave that gap open does the filter still keep all the dust in check? Or some dust might go through?

 

The open gap is before the filter.

 

Jimmyc13,

I just checked my car and there's two plastic screws further in and two in the front (probably useless). So you have to peel open the filter box to take out the screws from the inside? Or can you use a long needle plier and snap it out by sticking it into the opening from the front? I am curious as how it sounds like myself.

 

The other poster who mentioned removing the "power duct" might in fact
cause you to LOSE performance, might be correct here.

With nearly the exact same 60 ft times from your May visit to your November visit, you only gained .17 seconds and .2 mph but
you were running in 30 degree cooler weather, drier air and lower density altitude.
The 30 degree cooler air ALONE should of given you more of a time improvement than .17 seconds and .2 mph.
You very well MIGHT have done better WITH the "power duct" back on.

But to know for sure you would of have to listed wind conditions for both
days you ran too. Or, put the Power Duct on and run a few times, then
take it off, let the car cool and run a couple more times on the same day.

 

I have the k&n/ztube on my 05 6MT. At first, I just had the ztube. At that time, I could tell *zero* difference in either feel, or sound, of the car. The k&n did absolutely nothing as well(disclaimer--this is just by feel/sound of the car).

I took off the air duct that leads to the "power duct", the one that runs from the central part just behind the radiator lengthwise to the airbox. After that, I noticed a huge increase in intake noise. And this was in the last few weeks of summer, and I didn't notice any tangible performance effects. After about a week, I put it back on.

Now, at my last trip to the track, I tried removing the air duct again. I had run a few 14.2's. After I took the duct off, I instantly ran two 14.4's at about 2 less mph, with similar 60 foot times. I put the duct back on, and my times stabalized again. Later on in the night is when I ran the 13.7/13.8's.

 

I just installed my z-tube and KN filter today. Now the KN filter has obvious benefits, but as far is the z-tube is concerned, there really are none. I was aware that any HP gains would be negligible, but after installed it I didn't really hear any difference at all - even above 4k rpm.

Somebody must have said at some point "the z-tube sounds waaaay better", and then you kinda hear what you want to hear. If it wasn't a christmas gift, I'd prolly send the z-tube back. If you have money to blow and just want to install something on the car, then it was a fun little install, but otherwise I say save your money. The car doesn't sound any different.

KN = Go for it.
z-tube = save your cash.

 

[QUOTE=kajoob]I just installed my z-tube and KN filter today. Now the KN filter has obvious benefits, but as far is the z-tube is concerned, there really are none. I was aware that any HP gains would be negligible, but after installed it I didn't really hear any difference at all - even above 4k rpm.

I just installed the z-tube on x'mas day too while I had the K&N for a month now. I agree with you that I don't feel any gain in power too but there is a tad deeper sound between 1800 to 2500 rpm. I drove my car before and after so I can tell the difference.
After taking the stock tube out, it is smooth inside as well as the z-tube except with the tiny hole that leads to the bottom resonator. The top trapazoidal shape "bump" doesn't appear inside the tube.
I think the z-tube is just a little fun hands-on fix if you enjoy working on your car.