I installed my 3/8" plenum spacer over the weekend and have noticed a couple things that I didn't notice before the install.

1) Once the engine heats up...there is a slight vibration in the gas pedal at low RPM (1-2.5k). My exhaust also seems to be a little louder and deeper in this same RPM range.

2) When idling after the engine is warmed up...RPMS wiggle around 500 and sometimes drop to around 350 and quickly come back up. Is this normal or could I possible have a leak?

I wasn't able to get my hands on a torque wrench for the install, so when torquing the perimeter bolts and the 6 bolts on top of the plenum...once the bolt gave a decent amount of resistance to turn, I gave it another 1/3 of a turn to tighten it. I didn't want to over torque it and warm something....but maybe I haven't given it enough?

Your help is much appreciated guys. Maybe I'm just being paranoid.

Thanks!

 

I think you got the powerlab plenum spacer. I got the same installed not too long ago. The vibration that you're feeling is the strut bar rubbing against your engine. As the engine warms up, it seems the spacer expands quite a bit so you need to add more washers to the strut bar to raise it higher.

#2 I'm not sure as mine is fine. Maybe some experts can chime in and help.

 

Yeah you are probably right about the strut bar. I did allow some space (2 or 3mm) but I guess that isn't enough. Is that something that needs to be fixed right away or can it wait until I have some time?

 

#2 can be just a normal irratical idle that the Z has or it could be an air leak. honestly though, if you have a leak in your plenum you will sputter if not stall at a stop light. The idle will actually make your car flutter like it is losing air. Bouncing RPM tach is normal, but you have to distinguish which one it is?

the increased exhaust sound at idle or even driving is normal. More intake flow creates more exhaust note out the back end.

-As far as not having an inch lb wrench, as long as you followed the tightening sequence that you would have followed with the torque wrench... you should be good. If you followed the sequence and tightened them a little at a time and didn't snap any bolts your good to go.

 

Can you hear a vacuum leak?

 

I don't believe so. When I get home this evening I can rev up the engine a few times in the garage and see if I hear anything abnormal. I would imagine it would sound like a loud 'hiss' correct? Is there anythign else I should look for?

 

I'm just worried that I "babied" it too much and didn't tighten down the bolts enough. I really don't know how much 9-10 lbs of torque is so I did my best...but I know I didnt pop any bolts.

 

if you have a vacuum leak in your plenum you would think your car was broke... its not a leak.

 

9-10 ft/lbs isn't much, and I believe the top 6 plenum bolts should only torqued to 80 inch/lbs (~6.5 ft/lbs.). I installed my spacer the first time trying to use a ft-pound torque wrenched turned way down, then realized i was over-torquing it. I just had to re-install for my fuel injector install, and this time around I made sure to pick up a in/lb torque wrench - now i have piece of mind. However, piece of mind cost $80

 

need to reset ecu

 

Read this thread: https://my350z.com/forum/intake-exhaust/299010-5-16-md-plenum-spacer-installed-having-idling-problems.html

Searching FTW....

 

Awesome write-up VO!!

 

 

If it was a leak you'd know it. No worries there. You need to tighten everything according to specs though. Let the ECU reset to the new airflow.

It really could just be a rubbing issue....I believe there are only one or two spacers that don't require either a new or adjustment to the strut bar.

 

A vacuum leak (if audible) makes a hissing sound. You can also wet your finger and move it along the edge. Unfortunately you will not get bubbles with a soap-water solution. The upper plenum has some hoses in the back. Make sure they are connected.

 

It appeared to be a rubbing issue with the strut bar. I made some height adjustments and the vibration is gone. As for the idle issue....I think I was just being paranoid.

 

Any noticeable gain in performance?

 

^ wanted to know too.

 

This has been discussed a million times, but by far this was the best bang for the buck mod for me. Opens up a top end that really wasn't there from factory. Makes me actually want to take it past 5,500.

 

It should be in INCH pounds, not ft/lbs -- inch pounds is alot more precise torque spec. If you torued them in ft/lbs you would have already snapped the bolts off.