Why Upgrade to 1.75‑Bar Turbo Charge Piping on Your Forester?

Subaru Forester owners who push beyond stock turbo setups quickly discover the factory charge pipes become a bottleneck. The stock piping is typically designed for lower boost levels and uses restrictive bends, thin metal, or rubber sections that can collapse under higher pressure. Moving to a 1.75‑bar (~25.4 psi) turbo charge piping system transforms the entire air path from the turbo compressor outlet to the intercooler, and from the intercooler to the throttle body. The result is measurably better airflow, faster spool, and a more responsive throttle – exactly what you want from a Forester turbo mod.

Upgraded piping often features larger inner diameters, smoother internal surfaces, mandrel bends, and high‑temperature silicone couplers. These details reduce turbulence and pressure drop, allowing the turbo to work more efficiently. For a Forester running a 1.75‑bar target, this upgrade is not just a “nice to have” – it becomes essential to realize the full potential of supporting mods like a bigger turbo, intercooler, and engine management tune.

The Science Behind 1.75‑Bar Airflow Demands

At 1.75 bar of absolute boost, the turbo is moving a massive volume of air. Any restriction in the charge piping raises the effective backpressure on the compressor wheel, increasing exhaust gas temperatures and slowing spool. Smooth, larger‑bore piping reduces the velocity while maintaining mass flow, which lowers pressure drop. A well‑designed 1.75‑bar charge pipe kit typically uses 2.5‑inch or 2.75‑inch tubing, compared to the stock 2.0‑inch or smaller sections. This 15–30% increase in cross‑sectional area directly translates into better flow and less lag.

Additionally, the piping must withstand sustained 25 psi boost without bulging or leaking. High‑grade aluminum or T304 stainless steel is the norm, paired with multi‑layer silicone couplers that resist heat soak. Upgrading to such hardware is a foundational step before even considering boost controllers, fuel system upgrades, or larger turbos.

Top 1.75‑Bar Turbo Charge Piping Kits for the Subaru Forester

Not all charge piping kits are created equal. Fitment, material quality, coupler type, and included hardware vary significantly. Below are the most trusted options that have proven themselves in Subaru circles for 1.75‑bar and higher boost targets.

1. Injen SP Series Cold Air Intake with Charge Pipe Upgrade

Injen’s SP Series is a complete intake and charge pipe solution that eliminates the restrictive stock airbox and resonator. The kit includes a mandrel‑bent aluminum charge pipe that replaces the factory piece from the turbo outlet. It uses a large, washable dry‑flow filter and a heat‑shield to keep intake temperatures down. The charge pipe smooths the transition from the turbo to the intercooler, reducing turbulence. While primarily marketed as an intake, the SP Series effectively upgrades the first section of the charge piping. It’s a popular choice for Forester owners who want a simple, bolt‑on improvement for 1.75‑bar setups. Injen backs their products with a limited lifetime warranty, and the filter never needs oiling.

Key advantages: Simple install, excellent filtration, and immediate throttle response improvements. It works well with stock or aftermarket intercoolers.

2. GReddy Type RS Intercooler Piping Kit

GReddy’s Type RS intercooler piping kit is designed specifically for Subaru turbo models, including the Forester XT. It replaces the entire piping between the intercooler and the throttle body, as well as the turbo‑to‑intercooler section, with mandrel‑bent aluminum tubing and heavy‑duty silicone couplers. The kit is sized for high boost – typical for 1.75‑bar targets – and reduces pressure drop across the system. GReddy includes T‑bolt clamps and a blow‑off valve flange (BOV not included). The piping is polished or available in a wrinkle‑black finish for a professional engine bay look.

Key advantages: Comprehensive kit covering both hot and cold sides, proven track record in Subaru performance, and excellent fitment for Forester chassis. Many tuners consider it a must‑have for any Forester aiming beyond 20 psi.

3. HKS Super Turbo Piping Kit

HKS is synonymous with high‑end Japanese performance parts. Their Super Turbo piping kit is engineered for maximum boost response. It features a unique design with short, direct routes and smooth transitions that minimize volume and restriction. The kit typically includes a larger diameter pipe from the turbo to the intercooler, and a matched pipe from the intercooler to the throttle body. HKS uses their signature blue silicone couplers and heavy‑duty clamps. The piping is made from high‑strength aluminium with a black powder‑coat finish that resists corrosion and heat.

Key advantages: Focus on reducing piping volume for faster spool, premium build quality, and compatibility with most Forester turbo models. The HKS kit is often chosen by enthusiasts who want maximum responsiveness from their 1.75‑bar tune.

4. Samco Sport Silicone Turbo Hose Kit

While many kits use metal pipes, Samco Sport offers silicone hose replacements for the factory rubber sections. This kit includes a set of reinforced silicone hoses that connect the turbo to the intercooler and the intercooler to the throttle body. The silicone is multi‑layer with embedded aramid fibres, capable of handling sustained 1.75‑bar boost without bulging. Samco hoses are flexible, making installation easier in tight engine bays, and they resist oil and heat better than standard rubber. The kit comes with stainless steel hose clamps and includes all necessary bends and reducers. It’s an excellent choice for Forester owners who want to keep some OEM routing but upgrade to a more durable, high‑flow material.

Key advantages: Exceptional heat and oil resistance, easier to route than rigid metal pipes, and proven reliability in racing applications. Samco hoses are also lighter than full aluminium piping.

5. Custom Mandrel‑Bent Aluminium Piping Kits (e.g., TurboXS, MAPerformance)

Many shops offer custom kits that are vehicle‑specific for the Forester. TurboXS and MAPerformance produce charge pipe kits that include both hot and cold side pipes, sold separately or as a set. These are often larger diameter (2.5” to 2.75”) than budget options and include CNC‑machined flanges for the blow‑off valve and boost reference ports. They are fully polished or available in matte black. Custom kits allow you to choose the exact routing and finish you prefer, and they often come with detailed installation instructions for the Forester chassis. Because they are made in smaller batches, quality control tends to be high.

Key advantages: Fitment tailored to Forester XT and N/A turbo conversion builds, choice of finish, and upgrade‑ready features like O‑ring grooves and silicone couplers with integral bead locks.

What to Look for When Choosing 1.75‑Bar Piping for Your Forester

Material and Construction

Aluminium (6061‑T6 or 5052) is the standard for aftermarket charge pipes. It’s lightweight, easy to weld, and resistant to corrosion. Stainless steel (T304) is stronger and better at handling extreme heat but heavier. For a Foreter producing 1.75 bar, both materials work, but aluminium is preferred for weight savings. Check that the pipes are mandrel‑bent, not press‑bent, to avoid collapsed inner walls. Welds should be smooth with no slag or pin holes.

Couplers and Clamps

Multi‑layer silicone (at least 4‑ply) is essential for holding 25 psi. Look for couplers with embedded aramid reinforcement. Cheap silicone can soften or blow off under sustained boost. T‑bolt clamps are far superior to worm‑gear clamps – they distribute clamping force evenly and don’t strip under torque. Ensure the kit includes enough clamps of the correct diameter for each connection.

Fitment and Integration

A Forester engine bay is tight, especially near the turbo and intercooler. Choose a kit that is specifically designed for the Forester XT (SG or SH chassis) or a universal kit with careful measurement. Kits that include a blow‑off valve flange (1” or 1.25” standard) are preferable because you can plumb a BOV easily. Some kits also include a boost reference port for the wastegate or boost gauge.

Supporting Mods for 1.75‑Bar

Upgrading charge piping alone won’t safely get you to 1.75 bar. You need a tune (open‑source or Cobb Accessport), fuel pump upgrade (255 lph or higher), and possibly larger injectors. A front‑mounted intercooler (FMIC) upgrade is highly recommended because the stock top‑mount struggles with heat soak at elevated boost. The charge piping kit you choose should be compatible with your intercooler setup; many kits are designed for either TMIC or FMIC configurations.

Installation Guide for Forester Charge Piping

Tools and Preparation

  • Socket set (metric) with extensions
  • Flathead and Phillips screwdrivers
  • Trim removal tools (to avoid breaking plastic clips)
  • T‑bolt clamp tool (if included, or a nut driver)
  • Jack and jack stands (to access lower piping)
  • Shop rags and degreaser
  • Anti‑seize compound for bolts

Step‑by‑Step Installation (General Guidelines)

  1. Disconnect battery and allow the engine to cool completely. Boost piping holds heat; work on a cold engine for safety and easier handling.
  2. Remove the stock air intake and airbox. On a Forester, this often means unclipping the MAF sensor and pulling the resonator. Set aside – you may reuse the MAF housing.
  3. Access the turbo outlet pipe. Depending on your model, you may need to remove the heat shield around the turbo. Use penetrating oil on bolts that are difficult to turn.
  4. Remove the factory charge pipe. This tube runs from the turbo to the intercooler. Unbolt it at both ends and slide it out. If it’s in one piece, wiggle it free.
  5. Remove the intercooler to throttle body pipe. This is usually the longer section that crosses over the engine. Unclip the rubber hoses and disconnect any vacuum lines. Avoid pulling on the wires for the TGV (tumble generator valves).
  6. Clean the mounting surfaces. Use a rag and brake cleaner to remove any oil residue where the new couplers will seat. Oil can cause couplers to slip under boost.
  7. Test‑fit the new piping. Place each section loosely to confirm routing and length. Trim silicone couplers if they are too long – never force a pipe into position.
  8. Install the new piping. Start at the turbo outlet. Use the supplied clamps but do not overtighten before all sections are in place. Attach the intercooler pipe and then the cold side. Ensure any BOV flange is oriented correctly.
  9. Tighten all clamps sequentially. Use a torque pattern – tighten to moderate resistance, then go around again. Over‑tightening can damage silicone.
  10. Reinstall heat shields if they still fit. Some aftermarket pipes require trimming the stock heat shield. Check clearance to avoid rubbing.
  11. Reconnect the battery and start the engine. Let it idle for one minute, then rev gently to about 2500 rpm. Listen for hissing – that indicates a leak.
  12. Perform a boost leak test. Use a boost leak tester (available for Subaru) or a simple rubber cap with a Schrader valve. Pressurize the system to 15 psi and listen for leaks. Soapy water on connections will reveal bubbles.

Common Pitfalls

  • Overtightening T‑bolt clamps: They can cut into silicone couplers. Hand‑tighten plus 1/8 turn is usually enough.
  • Forgetting to plug vacuum lines: If the kit removes a factory vacuum port, cap it off with a rubber cap and zip tie.
  • Routing conflicts with the hood latch or fuel lines: Dry‑steer the car to ensure there’s no rubbing when the engine moves under torque.
  • Not recalibrating the MAF if the intake changes dramatically: After installing a bigger charge pipe, the MAF scaling may shift. A custom tune should account for this.

Performance Expectations After Upgrading to 1.75‑Bar Piping

Real‑world results vary by car, but most Forester owners report:

  • Quicker spool: 300–500 rpm earlier on the boost threshold.
  • Peak horsepower gains of 15–25 whp on a dyno, depending on the tune and supporting mods.
  • Improved mid‑range torque: Up to 20 lb‑ft gain from 3500–5500 rpm.
  • Faster throttle response: The engine feels more eager to rev, especially during part‑throttle driving.
  • More consistent boost: Reduced pressure drop means the boost controller doesn’t have to work as hard to maintain 1.75 bar.

It’s important to note that on a stock turbo (VF40, VF52, etc.), upgrading piping may only yield moderate gains. The real benefit comes when you pair it with a larger turbo like a TD05 or Blouch 18G. The piping then becomes the supporting infrastructure that allows the bigger turbo to deliver its full potential.

Maintenance and Longevity of High‑Boost Piping

Aluminium and silicone are low‑maintenance, but you should inspect the system every oil change:

  • Look for cracks or bulges in silicone couplers, especially near the clamp edges.
  • Check clamp tightness – they can loosen slightly from thermal cycling.
  • Clean the air filter according to the manufacturer’s schedule.
  • Inspect the inside of the pipes for oil residue. A small amount is normal (from PCV), but excessive oil indicates a turbo seal issue.

Many high‑quality kits will outlast the car if installed correctly. Samco Sport hoses, for example, have a reputation for lasting 10+ years in Subaru applications.

Frequently Asked Questions

Do I need a tune after installing 1.75‑bar charge piping?

Yes. Changing the charge pipe volume and diameter alters the boost curve and air metering. Without a tune, you risk running lean or hitting boost spikes. Always retune after major induction modifications.

Will 1.75‑bar piping work on a stock turbo Forester?

Yes, but the stock turbo may not flow enough to fully utilise the larger piping. You will still see improvements in spool and response, but peak power gains are limited. Many owners upgrade the piping first, then upgrade the turbo later.

Can I install this myself?

If you are comfortable with basic hand tools and have done intake work before, yes. Expect 2–4 hours for a first‑time install. The most difficult part is accessing the turbo outlet bolt on some Forester models.

Which kit is best for a Forester XT (SG chassis)?

The GReddy Type RS kit is widely praised for SG Forester fitment. HKS Super Turbo also works well. Check vendor fitment guides before ordering.

Conclusion: Invest in Quality Piping for Reliable Power

Upgrading to 1.75‑bar turbo charge piping is a smart, foundational modification for any Subaru Forester owner serious about performance. The improvements in airflow, boost response, and engine longevity make it one of the highest‑value mods you can do. Whether you choose a complete kit like GReddy or HKS, or piece together a custom setup with Samco hoses, the key is to get piping that is properly sized, mandrel‑bent, and paired with quality silicone couplers and clamps.

Remember that charge piping alone is part of a larger system. Combine it with a professional tune, upgraded fuel delivery, and a capable intercooler, and your Forester will deliver thrilling responsiveness and power at 1.75 bar – all while remaining a dependable daily driver. Take your time choosing the right kit for your specific year and build, and follow the installation instructions carefully. With the right parts and a bit of labour, your Forester will transform into a truly quick turbo machine.