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Phenolic Thermal Manifold Spacer WRX/STi/LGT/FXT - 3mm

  • Subaru Phenolic Thermal Manifold Spacer

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Product Description

GrimmSpeed 3mm Subaru WRX STI Phenolic Thermal Spacer
GrimmSpeed 3mm Subaru WRX STI Phenolic Thermal Spacer


Do you know what your intake manifold sits on?...a superheated boxer engine. If you don't know already, the cooler your intake air is the more HP your car will achieve. We present you the answer to this age old problem, raising the intake manifold off the engine with GrimmSpeed's™ new real Phenolic Intake Manifold/TGV to Engine Thermal Spacer.

Phenolic spacers have been used for years by many other specialized automotive companies, but this is very new technology to the Subaru world.

What it does:

  • Greatly reduces the transer of heat from engine to intake manifold thus reducing heat soak.
  • One of a kind true Phenolic material, not cutting board material like others.
  • The cooler your intake temperature is the denser the air is which leads to more power
  • For every 5 degree reduction in air temperature, increases power by 1%.
  • The cooler and denser the intake air that the engine sucks in, increases the amount of air that can be mixed with fuel thus increasing efficiency.
    GrimmSpeed 3mm Subaru WRX STI Phenolic Thermal Spacer
  • Direct bolt-on.
  • When running the oem gasket only, your intake manifold gets very hot to the touch, enough to burn your hand. When the oem gasket is replaced with our Phenolic Spacer, your hand can be placed on the intake manifold without any issues.
  • We have installed both with and without OEM Subaru Gaskets and have had no issues with either way. We do recommend using 2 sets of oem gaskets however, one on both sides of the spacer.
  • USA made

How it works:

  • The intake air in your engine travels through the airbox into the turbo, then into the aluminum intake manifold. The air exits the intake manifold and goes directly into the engine.
    GrimmSpeed 3mm Subaru WRX STI Phenolic Thermal Spacer
  • While the intake air is within the intake manifold it picks up alot of heat from the aluminum intake manifold. This added heat reduces air density thus reducing engine power capabilities.
  • In stock form your engine has a steel gasket between the intake manifold and engine which allows the heat from the engine to quickly transfer into the intake manifold. By replacing this steel gasket with the GrimmSpeed™ Phenolic Spacer you are greatly reducing the transfer of engine heat into the intake manifold.
  • Phenolic Spacers are able to withstand 500+ degrees F. Subaru engines run at the hotter end of operation around 200 degrees F, so the Phenolic Spacer is well within its max running temperature. GrimmSpeed™ has tested that it is also safe to run race fuel, E85, and methanol with the Phenolic Spacers.
  • The Phenolic Spacer will conduct 300-900 times less heat than the oem steel gasket.

Temperature Testing Data: Testing at 1/2 hour intervals. All testing was conducted fairly in Fahrenheit measurements on ONE day at a consistent outside temperature.

Test #1 - OEM measurement from IM without spacers, 152 degrees.

Test #2 - with 3mm phenolic spacers the temp dropped to 134 Degrees

Test #3 - With 8mm phenolic spacers the temp dropped to an outstanding 108 Degrees!!!

That is an OVER 44 Degree drop with the largest phenolic spacers!



WRX '02-'10
STi '02-'10
Legacy GT 02-'10
Forester XT '02-'10

Product Videos

GrimmSpeed Phenolic Spacer Ethanol Fire Test (02:24)
Guys over on nasioc wanted us to soak our thermal spacer in ethanol to see if it broke down. well after 12 days of soaking it held up perfectly. So now we will kill the spacer by starting it on fire...
  • GrimmSpeed Phe...
    Guys over on nasioc wanted us to soak our thermal spacer in et...

Product Reviews

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Product Reviews

  1. spacers are amazing and really do work

    Posted by Andrew Kapczynski

    These spacers are amazing and really do work. Before I installed mine, I could barely touch my intake it was so hot just from warming up and idling. Now that I have them I can do a 10 minute heat and my intake never gets hot. In-fact my intake didn't get much above ambient temp. I wish I had a checked the temp with a laser before so I could give an accurate number of how much cooler my intake is now. I am a true believer in this product. I have made my own before and they are very difficult to make, which is why I understand how much they cost to purchase. Phenolic is a very abrasive material which makes it very difficult to cut. They cannot be cut out with lasers or milling machines. The only way to get a clean cut without destroying every bit or blade within 100 miles is to use a waterjet. Believe me I tried bandsaws, cnc, and laser cutting. Not to mention the toxic dust and smoke that is created. You will be amazed at what these do for your intake temps, I was!

  2. Works as advertised

    Posted by Ryan Schram

    "I picked these up since I was doing TGV deletes anyway. Works as advertised, and your car and tuner will appreciate them too!

    I replaced the steel gaskets with these (no more steel ones). no leaks so far as I can tell."

  3. Really do the trick

    Posted by marcello marchesini

    "These really do the trick. If you want to, grab the intake manifold after a few good highway, i mean drag, runs before and after. Although a subjective test, the results are obvious.

    AND as a testament to the customer service GrimmSpeed offers... I needed these for a build the next day, and my paypal account was not up and running yet.

    Justin OVERNIGHT SHIPPED it on an IOU. I was never a customer before (now I'm obsessed) and Justin didn't know who I was. Simply amazing.

    I'm only saying this to show how much they'll work with your special needs. Not to advertise this IOU service. Thanks GrimmSpeed for pimpin' my ride."

  4. inexpensive mod that will yield positive results

    Posted by Jason Sherrill

    "While my install was quite a bit different from the route that most will use, I can vouch for the fact that the spacers are very easy to swap in and out and add or remove OEM gaskets, if-necessary.

    With that being said, my install process was much more complex because I chose to go all-out and get a ported and polished (PnP henceforth) and coated Throttle Body, PnP and coated TGVs and PnP Intake Manifold from Justin. Along with an APS Turbo Inlet Pipe I picked up, this was much more involved than simply disconnecting a few harnesses, unbolting the TGVs and lifting things up and inserting the new spacers...

    Basically, I started out by following the factory recommendations for removing from the TGVs on-up. With all of this out, I proceeded to follow the directions for installing the APS Turbo Inlet Pipe (found here: APS Turbo Inlet Pipe Installation). As things came together and prior to putting the ""manifold assembly"" back in the vehicle, I put the Phenolic Spacers in-place. They fit perfectly and once everything was back in, I torqued the bolts down to spec and all seemed to be seated good and firm. While the spacers are obviously thicker than OEM gaskets, there wasn't ANY addition movement in the manifold, TGVs or otherwise - even when grabbing a hold of the runners and give a few hard tugs! In fact, there are some small round tabs sticking up that are meant to hold the OEM gaskets in location while the TGVs are being put back in place that will fit any combination of OEM gaskets +/- the spacers... Even with 2 sets of OEM gaskets and the spacers installed, there is still a perfect fit on these ""tabs"", which made it much easier to seat them properly, after-the-fact!

    In the end, I personally chose to run OEM gaskets on both sides; however this was only to add extra ""insurance"" to my own application. They were added after I had already torqued down the TGVs and completed my other installs... unfortunately, I'm very worrisome and simply did this for my own piece-of-mind - prior to doing so and after several sessions of idling and revving the motor, I had no leaks, squeaks or otherwise! Personally, if I did it again, I'd probably just save some money and run without gaskets...

    Concerning the results: as-always, they can vary, but I took measurements before and after with an infrared thermometer (cheap, but seems to be somewhat accurate) and noticed external temps from the TGVs, up through the intake runners and all the way to my throttle body seem to be down 10+ degrees, depending on where they were measured. I have chosen to omit the exact before vs. after temps, simply because the thermometer wasn't what I'd consider top-grade and I'm not a technician by any means; however I do feel that it's fair to say that I took enough measurements to prove that there was a steady decrease across the board and that these parts are doing exactly what they're made to do.

    Overall, this install is quite simple and the parts definitely seem to be functional. I'd recommend that anyone with the means to pick up a set and install them ASAP - they're an inexpensive mod that will yield positive results!"