I installed the Kinetix v4 plenum last night, which by the way is a quality piece of work and came with really good instructions. I took it out for a test drive this morning, and my butt dyno tells me I lost some low end torque. I am waiting for the Kinetix high flow cats before I dyno it. It also seems the engine got QUIETER? I had the following mods prior to last night:

NISMO CAI
NISMO headers
NISMO exhaust

With just those 3 the car seemed peppier and sounded meaner. The plenum seems to have quieted and tamed it a bit. Could it be that the stock cats are now becoming a bad enough choke point? Any thoughts?

Thanks

 

It almost sounds like you took off the Kinetix and installed the stock plenum. The Kinetix should be slightly louderthan stock.
I'm not sure about the interworkings of your mods with the addition of the plenum, but it would seem like the plenum should add torque--especially in the mid to upper RPMs. Keep in mind that the ECU will need time (100-150 miles) to adapt to new airflow mods. You might feel more power after some drive time.

...and the stock cats are one of the main bottlenecks in the exhaust flow.

 

Ok, this is really WEIRD. I test drove this morning without the engine cover or strut bar, just in case I had to fiddle with the plenum. I drove for about 30 minutes and came back. I let the car sit for two hours to cool down, and then I reinstalled the cover and strut bar.

I went out again for an errand and WOW! From the moment I turned on the ignition the car had a growl angrier than ever before. I took it for a 1 hour drive and it was AWESOME. It had a deeper, louder growl and it ran great.

So, I am not crazy, and I KNOW that the engine cover and strut bar had nothing to with this, sooooo, could it be that turning the car off and leaving it be for a while somehow made the ECU catch up?

Cant wait for the cats....!!!

 

You'll loose more low end with the cats. The best way to correct this is by getting flashed.

 

Also, make sure the STB is not rubbing against the plenum. The "Growl" you might be feeling is the plenum vibrating against the STB which will then vibrate through the whole car. Take a business car and see if you can slide it all the way under the STB. If not, the STB is rubbing against the plenum. This could cause a "wear" point on the plenum and also a little loss of power. If you drove the car with the Kinetix but without the STB, you wouldn't have felt the vibration but when you put the STB on, you felt the "Growl" which could be just vibrations.

 

I did V1 to V4 and it always takes more than 1 week to get the ECU to adjust to the new Plenum. On V4 it took 2 weeks for the growl to come back.

 

When you first took it out, did you make agressive runs? You need to do 5 or 6 0-70 full throttle runs to get the ECU to adapt to the mod.

I could feel the difference in each run after my install.

 

I read somewhere that the 2004.5's could not be reflashed yet. Any news on this?

 

Your right....but when you can get flashed, you should do it. Wasn't aware that you had a 04.

 

Thanks for the tip! The credit card trick works great. The bar does touch the plenum right in the middle. But I didn't feel any vibration, although if it is touching it may very well be vibrating and me not feel it. It sounded more like a growl like when I first had the exhaust installed, only deeper. Is there an adjustment that I can make to get the bar off the plenum? (short of removing the bar)

 

A few washers at the mounting points at the frame to act as spacers? That might work.

 

Here are some pics of my install

http://www.quiros.net/350z/plenum.htm

Notice the sway bar has a dent in the middle, and that is where it touches the plenum. Does anyone else have a swaybar that looks like this? The washer idea gives me pause, as the bases at each end of the bar seem to give it rigidity, and I would be lifting the bases with the washers.

Comments?

 

If it is touching, there will definately be some vibration. Mine was very noticable. My gas milage also went to shi- when the plenum was installed 9mpg

 

I believe I put two 3/8ths washers on each of the two front bolts on each side. I then put one 3/8th washer on two of the rear bots on each side. This way the STB was some what slanted back. This was to create tension and clearance from the plenum and the hood.

 

I have the same setup as you do - nismo headers, exhaust, cai, kinetix v4 with the addition of the kinetix h/f cats, nismo flywheel/clutch, ts reflash, and nismo cams. When I had the v4 and cats installed the total complexion of the car changed. The response was much better with noticeable pull from about 4000 rpms on. Now that we have added the cams, I can't say enough about the total performance of the car. I absolutely love it. I am extremely pleased with the combination of mods. I only have 9300 miles on it so it really isn't even broken in yet so I am hopeful that it will get even better. You will definitely enoy the addition of the h/f cats because the stock cats stink to say the least. Good luck with your mods. I definitely love mine.