GrimmSpeed WRX/STI Upgrades You Can't Live Without

GrimmSpeed has been one of the pioneering companies in the Subaru performance industry who have invested years and dedication to bring Subaru enthusiasts with innovative products. If you’re a new Subaru enthusiast, they have entry-level products that you can begin with an learn how upgrades make a difference in your performance. And they also have highly advanced upgrades that the seasoned enthusiast is very familiar with that can support substantial amounts of horsepower. Additionally, GrimmSpeed is not limited to power upgrades, they have a great selection of drivetrain and suspension upgrades to improve the overall driving experience. Most importantly, even with early WRX and STI models, GrimmSpeed continues to develop, innovate, and engineer products that renew our love for older Subarus, while optimizing the performance and potential of the latest models to roll off the assembly line.

With that being said, here is a list of just some of the GrimmSpeed uprades that you can’t live without on your Subaru WRX/STI.

 

GRIMMSPEED BOOST CONTROL SOLENOID

The GrimmSpeed Boost Control Solenoid is a simple plug-and-play unit that provides a quicker boost response to the turbocharger, it’s affordable, and highly durable. This example should be under the hood of every turbocharged Subaru. This little upgrade is ideal for those of you who are getting your Subaru tuned and are making boost that surpasses the limits of your factory-equipped 2-port solenoid. This is a 3-port example that interrupts the boost signal that travels from the turbocharger to the wastegate, and rather than bleed the boost signal like the factory unit will do, this will generate a tighter boost control with faster consistency and precision. This will also reduce turbo lag during boost and will work safely in conjunction with your factory ECU. In terms of tuning, it makes life much easier for your tuner who is performing a flash tune, or who is using a COBB Accessport. Although the aftermarket has many solenoid options for the Subaru WRX/STI, the GrimmSpeed unit features durable internal construction along with nickel-plated fittings, a laser-cut CNC bracket that can withstand extreme conditions in the engine bay.

 

GRIMMSPEED BOOST CONTROL SOLENOID 2008+ SUBARU STI

GRIMMSPEED BOOST CONTROL SOLENOID 2002-2005 SUBARU WRX

GRIMMSPEED BOOST CONTROL SOLENOID 2006-2007 SUBARU WRX / 2004-2007 SUBARU STI

GRIMMSPEED BOOST CONTROL SOLENOID SUBARU WRX 2015+

 

GRIMMSPEED COLD AIR INTAKE

Like most turbocharged vehicles, the Subaru WRX and STI responds very well to a quality cold air intake system. The factory airbox is just fine if you plan on leaving your Subaru bone stock. However, if you perform upgrades such as a cat-back exhaust system or anything else that could increase the power and the torque, your turbocharger will certainly struggle to breathe, putting a limit on your performance. The thing is, is that the GrimmSpeed examples are not your average cold air intake design. They have invested countless hours into the development to engineer a cold air intake with the right amount of volumetric efficiency. With a proper tune, this intake provides noticeable gains in power and performance. Here are some of the details:

• Hybrid cold air and short ram design to combine the advantages of both while eliminating the negatives of a traditional intake system
• Designed with a proper air straightener to provide accurate and consistent MAF sensor readings
• The included filter can be serviced and cleaned for continuous use
• The MAF sensor location is inside the heat shield and isolated from the engine bay heat
• Includes a laser-cut heat shield that is CNC bent and powder-coated, and it has a proper fitment

This is quality stuff for sure. And by that, meaning that it’s not some janky pipe with a welded MAF housing with a local auto part store cone-style filter that can break apart getting sucked into your turbocharger. Like all Grimmspeed products, their cold air intake examples make for a great investment that will flow enough air from mild to moderate modifications.

GRIMMSPEED COLD AIR INTAKE 2002-2007 SUBARU WRX/STI

GRIMMSPEED COLD AIR INTAKE – 2008-2014 SUBARU WRX/STI

GRIMMSPEED COLD AIR INTAKE – 2015-2018 SUBARU STI

GRIMMSPEED COLD AIR INTAKE – 2015-2018 SUBARU WRX

 

 

GRIMMSPEED TOP MOUNT INTERCOOLER

One of the roadblocks on the path to more power and performance in the Subaru WRX and STI models is the factory top mount intercooler. The OEM top mount has a small profile, and because it essentially mounts directly to the turbocharger, it is very close to the heat generated by the turbo and the engine. The only solution to cooling, is relying on the hood scoop, or upgrading to a larger core.

The main issue with the factory top mount intercooler is that due to the lack of size, you risk experiencing heat soak. More importantly when you experience heat soak, you limit the power and performance potential from the rest of your modifications. You might not hit your normal boost targets on a hot day. Or your Subaru may feel like it’s making about 70% of the power it normally does.

So how does a GrimmSpeed Top Mount Intercooler relieve this issue? GrimmSpeed manufactured their units with a thicker, all-aluminum bar-and-plate core. A thicker core lowers the intake charge temperatures to the intake to maintain and increase your power levels. Additionally, these have been designed to fit your stock location while maintaining proper clearance under your hood so that your hood scoop can still direct air to make proper contact with the top surface of your intercooler. Upgraded top mount intercoolers offer better spool response when compared to a front mount intercooler setup, however, a front mount intercooler may be ideal once you want to start making power levels above 400 WHP. If you want to stay in that 350-400 WHP sweet spot, the GrimmSpeed top mount intercooler is perfect for maintaining a cooler intake charge temperature if you have an intake, full exhaust, injectors, and a tune. BUT, note that most GrimmSpeed top mount intercooler examples can support 550-575 WHP so it is more than enough intercooler for those of you not trying to break records at the drag strip.

GRIMMSPEED TOP MOUNT INTERCOOLER -  2015-2018 SUBARU WRX

GRIMMMSPEED TOP MOUNT INTERCOOLER - 2022+ SUBARU WRX

GRIMMSPEED TOP MOUNT INTERCOLER – 2008-2014 SUBARU WRX

 

GRIMMSPEED TURBO INLET

One of the most documented issues in earlier WRX, STI, and other Subaru turbo models that shared the same EJ platform is the failure of the factory turbo inlet hose. The design of the inlet hose attaches to the compressor side of the turbo, and there are other vacuum provisions on the inlet. The problem is that this hose is made using rubber materials that will crack and tear over time, mileage, and road vibration. When this happens, it can trigger a check engine light, as well as have an effect on the performance because the turbocharger is sucking in unmetered air through those cracks and rips. The solution was a replacement made using heat-resistant multi-layered silicone hose with smooth interior walls. These are longer lasting units that improve the performance by increasing the throttle response due to the elimination of the accordion-style piping with the OEM unit.  

For 2002-2007 WRX and STI models GrimmSpeed does have their Post MAF Hose option. And unlike the rubber OEM turbo inlet for earlier WRX and STI models, the 2015-2021 WRX models had a plastic unit. This was also failure prone because at least with rubber in the earlier models, it can absorb engine vibration. The OEM plastic units just get hard and brittle from the heat and will crack wide open. GrimmSpeed solves this issue with an all-aluminum replacement. This replacement will be the end-all be-all units for the VA WRX, and makes for an excellent performance, and a preventative maintenance upgrade for the turbocharger.

GRIMMSPEED POST MAF HOSE 2002-2007 SUBARU WRX/STI

GRIMMSPEED ALUMINUM TURBO INLET 2015-2016 SUBARU WRX

GRIMMSPEED ALUMINUM TURBO INLET 2017-2021 SUBARU WRX

 

GRIMMSPEED PITCH STOP MOUNT

For seasoned Subaru owners, you might have experienced a broken pitch stop mount. And if you haven’t here’s what’s going on. You have your engine mounts that secure the engine in your WRX and STI no matter the generation. But then the pitch stop mount not only prevents excessive forward and backward movement of the engine and transmission, but it also has to absorb a lot of the drivetrain torque and energy. The problem is that the factory pitch stop mount has the strength of a chicken bone. Whether if you are stock, but especially if you have modifications that increase the power and the torque, you will eventually snap that OEM pitch stop mount.

GrimmSpeed has the answer with (2) versions. They have their regular unit which is more than enough for those of you with daily drivers. Then they have their race version designed for those of you who have Time-Attack style race cars, or if you are making all of the horsepower at the drag strip. Both feature strong billet aluminum construction and have urethane bushings on each end to be the last pitch stop mount that you will ever need. The race version is just thicker than the standard GrimmSpeed unit.

GRIMMSPEED PITCH STOP MOUNT 2002-2020 SUBARU WRX

 

GRIMMSPEED RADIATOR HOSE KIT

This is a must-do upgrade for your Subaru WRX and STI. Like many of the rubber hoses throughout your engine, these are naturally wear-and-tear items. But you especially need to pay attention to your upper and lower radiator hoses. Because your radiator hoses are made using rubber materials, they experience endless amounts of heat cycles every time your drive your Subaru. Heat expands, and contracts when your antifreeze cools. What happens is that the fibers inside the rubber will break apart, allowing your OEM hoses to expand enough to where they will rip where the worm clamps are installed on each end. Or the upper radiator hose can swell so largely that it contacts the cooling fan damaging the fan and the hose. Most importantly ripped hoses will leave you stranded because if you let your Subaru overheat you will lose your head gaskets then suddenly, your repair bill just increased 6X.

The GrimmSpeed Radiator Hose Kit will mainly include the upper and lower radiator hoses for your Subaru WRX and STI, and they feature heat-resistant multi-layered silicone construction. These units will not expand during heat and pressure and will provide you with long-lasting performance. Additionally, there are a few color options to choose from to improve the overall engine bay aesthetics.

GRIMMSPEED RADIATOR HOSE KIT – 2002-2007 SUBARU WRX/STI

GRIMMSPEED RADIATOR HOSE KIT – 2015-2018 SUBARU WRX

 

GRIMMSPEED AIR OIL SEPARATOR

Subarus are known for oiling issues that are inherent in many boxer engine designs. What happens is that oil, as well as oil vapors can enter the intake system which can coat the intake valves, as well as the top of the pistons. If this happens, several issues can arise. If oil and carbon starts to build up on your intake valves, as well as your pistons you will experience misfires, as well as check engine lights. This can send experienced mechanics down a rabbit hole because misfires can be caused by spark plugs, coil packs, dirty injectors, as well as a bad MAF sensor. However, those who are not seasoned with Subaru engines would more than likely overlook the fact that this is a crankcase issue. The design of the Subaru PCV system allows oil and vapors to infiltrate the intake system. If ignored and driven on for thousands of miles, the damage can become great enough to where you will need an engine rebuild. This issue acts as a slow-burning problem for Subaru engines. Your octane levels will change, leading to leaner running conditions. You will experience detonation and your intake valves will have caked-on carbon buildup.

The main fix to this issue is a proper air/oil separator. As the name suggests, an air/oil separator will separate the oil from the air, only allowing air to enter your intake system while keeping the oil in the engine where it needs to stay. The GrimmSpeed Air Oil Separator is a unique design where it mounts to the factory oil cap location and has hose provisions to hook up to your PCV system. If you don’t have an air/oil separator installed on your Subaru WRX or STI, now is the time to perform this upgrade so that you have a healthy running engine without the risk of those harmful vapors getting in your engine.

 

GRIMMSPEED AIR OIL SEPARATOR - 2002-2008 SUBARU WRX / 2004+ SUBARU STI

GRIMMSPEED AIR OIL SEPARATOR – 2008-2014 SUBAUR WRX

 

 

HONORABLE MENTION:

 

GRIMMSPEED CAT-BACK EXHAUST SYSTEM

A proper cat-back exhaust system might just be the most sought-after upgrade for the Subaru WRX and STI of all generations, and this is because of the performance gains, but mainly how cat-back exhaust systems amplify the unique sound that the Subaru boxer engine produces. Shopping for a proper cat-back exhaust can be exhausting frankly. And it isn’t easy due to the fact that there are several options, and the majority of cat-back exhaust systems are expensive.

Now that it’s established that a proper cat-back is an investment, it would be wise to invest in a Subaru-centric brand. Because GrimmSpeed are masters at their craft in terms of producing high-performance upgrades for the Subaru, they know what’s best for the Subaru engine. All of their cat-back exhaust system examples are made using premium-grade stainless steel materials. The piping diameter is enlarged with minimal bends to allow for a fast exit strategy for the exhaust gases during acceleration. This will produce more power, more torque, all while improving the overall throttle response. Additionally, they all have built-in mufflers that will still produce that race-inspired sound, but it won’t be too loud to disturb surrounding drivers and patrons. All of their cat-back options can also flow well enough and support other modifications that produce substantial amounts of horsepower.

GRIMMSPEED CAT-BACK EXHAUST SYSTEM RESONATED – 2011+ SUBARU WRX STI SEDAN

GRIMMSPEED CAT BACK EXHAUST SYSTEM – 2008-2014 SUBARU WRX/STI HATCHBACK