Plenum Spacer help.....

S

Squishymedic

Member
Location
New England
Okay so, I'm trying to get my ducks in a row before I pull the trigger on a spacer,(please know that I'm nowhere near as versed in this stuff like all you guys,so please be patient).

I'm figuring on the 5/16 copper Motordyne spacer,but the tech guy at my shop was very skeptical about the hp increase,,is it bullshit or what? Does it just make your whip sound meaner with no real increase?

Also he mentioned that I might need a larger throttle body....true?

And I have the Invidia catback exhaust with stock cats and stock header tubes. Is it best to change those as well?

Should I look for a true speed shop? These guys are great for repairs and they've NEVER boned me,but maybe this stuff is above them? He's a L1 ASE guy who used to work in a big dealership, but who knows.

ANY help would be greatly appreciated. If any local members can help me, I'll buy you dinner!

Thanks,

Ross
 
Plenum spacer does have proven dyno gains. Motordyne has independent dynos. The spacer just fixes a flaw in OEM plenum design. Infiniti fixed this on rev-ups, it's why they don't need a spacer. Throttle body has nothing to do with spacer. And gains from a larger TB are much more unproven. You may gain 5whp from HFC's. Headers don't gain much because it's a very short area. Plus the install is a pain so it's not really worth it for shorty headers that bolt to the cats. Only real gains from headers are by going to long tubs that replace the factory exhaust manifold and cat.

Install the plenum spacer yourself, it is literally one of the easiest things to do. Under an hour.
 
So he also said that I might want to replace the cats but they won't last as lone as the OEM.

Me? Install the plenum? Listen,, I can do surgical airways,,access sub-clavian blood vessels, put IV's and IO's in newborns to 1000 year old people, but I know my limits! I'd screw that up proper.
 
Aftermarket cats can last as long as OEM, but they are probably going to fail sooner just because the substrate is more for flow than emissions or longevity. Plus I'd trust Nissan over some little shop anyday. Having said that, I have a set of HFC's on it's way.

Just make sure the shop doesn't bill you for more than an hour of labor. If they do; either they're incompetent or trying to rip you off. It's seriously as easy as unbolt throttle body, unbolt plenum, put spacer on, put plenum on top of spacer with included longer bolts. You don't even have to remove hoses or anything.
 
5/16 gives good power where you would use it the most (inside the RPM range where you consistently cruise at).

1/2 will give better top end gains, I don't think anyone is tuning their FX for high speed as their primary concern, so I don't think many people will benefit from this.

Plenum spacer is a proven mod, you will not need to change your TB.
 
Squishymedic said:
So he also said that I might want to replace the cats but they won't last as lone as the OEM.

Me? Install the plenum? Listen,, I can do surgical airways,,access sub-clavian blood vessels, put IV's and IO's in newborns to 1000 year old people, but I know my limits! I'd screw that up proper.
Click to expand...

I usually go to a performance shop to do most of my mods but when I brought my car in for the plenum spacer mod, the mechanic asked me if I have a DIY guide. I said, I'd come back later. I end up doing the install myself.

It's easy just follow the install guide, take your time and have a cold beer ready after the install.


Sent from my iPhone
 
Personally, I can vouch for MD 1/2" copper spacers. You get dyno proven hp gain, and best bang for the buck. Contrary to what meme said, if you look closely at the MD dyno graph the 1/2" spacer will give you more HP through
out the RPM range! (that's why I installed).
Depending on how many miles are on your car, I would recommend BG induction service when you are installing your plenum spacers. I saw oil in my air intake system while installing the MD 1/2" copper spacers and had the bg induction service performed right away. I also custom installed an oil separator kit to stop oil ingestion through pcv system, which will reduce the amount of oil that enters the intake manifold, and will allow your engine to run more efficiently.

As far as high flow cats go, I would recommend FI RHFCs, they are much quieter than other cats, and are very well made. They are going to run you over $600 plus shipping, but you get what you pay for.
 
Okay so just to be clear I've read with the 1/2 inch spacer you'd have to modify the cover,, true? The descriptions of the hp boost are the same so I should just stick with the original 5/16 idea.
 
I don't see any reason to modify the engine cover for adding plenum spacer. The spacer is sandwich between the lower and upper intake manifold. Adding the spacer simply raises the upper manifold up half inch; it doesn't change the mounting or hitting anything with the half inch height increase.
 
I've got a 1/2" Powerlab spacer. Cover still fit, you just had to push the front edge down a tiny bit when screwing it back on because those bolts are on the top of the timing chain cover which don't move. Our FX engine bays are much bigger than G/Z, those guys often can't use strut bars with the plenum spacers.
 
Sorry to bring a thread back to life but i thought I'd post here instead of making a new one.

Dumb question, plenum spacers won't void the manufacturer warranty nor aftermarket correct?

That being said, do infiniti dealers install plenum spacers? Or anyone know of a shop in Illinois to get it done?

Thanks.
 
If you have a 2012, there is no spacer. Basically spacers only work for the original VQ35DE, not the revup and definitely not the HR which is what you have.
 
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