Plenum Spacer
It really depends on what school of thought you adhere to. There are those that believe a flat spacer is best as it keeps the same design of the plenum and there are those that believe an angled plenum spacer is better as it changes the curve of the manifold which forces more air to the front two cylinders. There are lots of discussions out there about these concepts. Depending on what you're reading, you will likely find somewhat biased reviews.
Personally, I run an angled spacer since I was keeping my OEM front STB at the time I bought it.
Personally, I run an angled spacer since I was keeping my OEM front STB at the time I bought it.
New Member
Joined: Mar 2013
Posts: 99
Likes: 21
From: florida
Save for header/exhaust. I tried both (on a freshly built motor) all I saw was just a power shift but no addition, unless you can feel 3 - 4 hps difference on certain bands. Maybe my car is different than yours mine being a base model, but most bolt-ons I tried did not add anything. I got true gains on my header and str8 single exhaust. Even my K&N regular filter recorded more power than CAI (long or short) on the same dynopack I used before the built. just my cents
The Motordyne 5/16 spacer is what most are using and Motordyne is a very good quality company with superior products,if you have the revup engine it is prerequisite to purchase the MREV2 lower manifold to see any gains which Motordyne offers as well. There website quotes the gains to be 15+hp and 18tq in the midrange if you have the non-rev I've been told the spacer by itself should be sufficient GL!!!
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Registered User
Joined: Apr 2018
Posts: 129
Likes: 24
From: Redmond, WA
I also recommend the Motordyne 5/16 with the iso-thermal kit (I think it's called?). It includes a copper TB gasket and aramid lower plenum gasket that helps isolate the intake charge from the engines heat. Before installing I would stop after a long drive, and the top of the plenum would quickly become too hot to touch. After the install, the plenum stayed cool to the touch for ~20-30 seconds before it heat soaked. Also my butt dyno showed pretty significant gains on my rev-up, but I installed an MREV2 at the same time.
New Member
Joined: Sep 2017
Posts: 222
Likes: 40
From: WA State
One other thing - If you are going to install it in an early 2003 you will have to drill and tap the strut bar bolt holes as the oem size is M8 and the hardware in the spacer kit is M10.
Last edited by tmdz; May 16, 2018 at 04:10 PM.
New Member
Joined: Jan 2017
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From: Pennsylvania
Registered User
Joined: Apr 2017
Posts: 116
Likes: 14
From: Kauai
I JUST installed a 5/16” Motordyne spacer and it makes a definitely noticeable difference. People say “you can’t feel an extra 5-6 hp” - but that’s false. Can you feel the difference when you turn on the AC? I certainly can and that’s only a 5-6 hp loss. I’d guess the spacer adds back just about exactly the same HP as the AC takes away. So shut off the AC and feel that extra power. It changed the way my car shifts, how it sounds and most importantly it makes the car ~3 seconds faster on the “test track” I use to measure my car’s performance. It did require a bit of mucking with the strut bar to get the hood closed properly.
I JUST installed a 5/16” Motordyne spacer and it makes a definitely noticeable difference. People say “you can’t feel an extra 5-6 hp” - but that’s false. Can you feel the difference when you turn on the AC? I certainly can and that’s only a 5-6 hp loss. I’d guess the spacer adds back just about exactly the same HP as the AC takes away. So shut off the AC and feel that extra power. It changed the way my car shifts, how it sounds and most importantly it makes the car ~3 seconds faster on the “test track” I use to measure my car’s performance. It did require a bit of mucking with the strut bar to get the hood closed properly.
Registered User
Joined: Apr 2018
Posts: 129
Likes: 24
From: Redmond, WA
I don't know about this forum, but there is a G35Driver sponsor who does e-tunes. Basically you tell him what mods you have and he creates a base tune, and sends it to you along with an UpRev cable/license. Then you plug the cable in along with a laptop, load in the new tune, drive around for a bit while recording A/F ratios and stuff. After a few pulls, you send him the results and he'll fine tune your maps based on that data. This way you can get a pretty accurate tune without needing to pay for dyno time (or in your case, pay for a dyno!). Feel free to PM me and I can send you the guys email. I'm planning on going this route once I have all the bolt-ons I want, though it's worth noting he will do free re-tunes for 1 year after purchase if you decide to change things up.
Registered User
Joined: Apr 2017
Posts: 116
Likes: 14
From: Kauai
Yes I heard of this. Costs a bit though I think..around $900? Tuning a car here on Kauai is pretty silly anyway since the speed limit is 50 and there’s only 2 lane roads.
....says the guy who installed a plenum spacer....lol!
....says the guy who installed a plenum spacer....lol!
Registered User
Joined: Apr 2018
Posts: 129
Likes: 24
From: Redmond, WA
I think listing pricing is against forum policy, but it's quite a bit more affordable than you think. The tune also allows you to run WOT in first a second gear, whereas the OE maps don't allow 100% throttle, so it'll definitely help with low speed fun as well.
i had the Skunk spacer @ 1st. sucked because it made the mani way to high for the bar and it touched my hood. So i got rid of it and went with the Kinetix and i did see some improvements, but nothing crazy.
Registered User
Joined: Jan 2019
Posts: 3
Likes: 0
From: Texas
Engine scraping hood
I replaced my engine in my 2004 350z, I put a 5/16 plenum spacer and a throttle body spacer. But now the pen strut tower or bar won’t fit and it’s eating into my injen intake and the top of my plenum.
Registered User
Joined: Apr 2017
Posts: 116
Likes: 14
From: Kauai
It took a 3-4 attempts of fiddling with those nuts on the strut bar to make mine fit - and just barely.
