Installing a boost controller is a proven way to sharpen your engine’s response and extract maximum power from a turbocharged setup. In the fast-paced world of roll racing—where you launch from a rolling start rather than a dead stop—having precise, on-demand control over boost pressure can mean the difference between pulling on a competitor or falling back. The Greddy Profec B is a popular choice among enthusiasts because it offers reliable electronic boost control without the complexity of a full standalone ECU. This guide walks you through every step of installing a Greddy Profec B, from gathering tools to dialing in your final boost settings for street and track use.

Why a Boost Controller Matters for Roll Racing

Roll racing places a premium on mid-range and top-end power. Unlike drag racing from a standstill, where traction dominates the first 60 feet, roll racing tests your ability to accelerate from 40–60 mph and beyond. A properly adjusted boost controller lets you fine-tune boost delivery, keeping the turbo spooled and responsive throughout each gear. Without one, the factory wastegate controls boost in a fixed, often conservative manner. An electronic boost controller like the Profec B can raise boost pressure, reduce spool time, and even provide a “gain” adjustment to tailor how quickly boost builds. This translates directly to faster roll-on passes and more consistent runs.

What You Will Need

Before turning a wrench, gather the following tools and components. Having everything on hand prevents mid-job trips to the hardware store.

  • Greddy Profec B boost controller (including main unit, harness, and vacuum hoses)
  • Basic hand tools: Phillips and flathead screwdrivers, 10mm and 12mm wrenches, pliers, and a socket set
  • Wire strippers and crimping tool with a variety of insulated butt connectors
  • 3–4 feet of silicone vacuum hose (4mm inner diameter is common, but confirm with your wastegate and intake manifold ports)
  • Zip ties for routing hoses and securing wiring
  • Electrical tape and heat shrink tubing
  • Multimeter for testing connections
  • Shop vacuum or compressed air to clean areas before mounting
  • Optional but recommended: a boost leak tester and a handheld OBD2 scanner to monitor engine parameters during tuning

If your vehicle uses a vacuum source other than the intake manifold (e.g., a dedicated vacuum port on the turbo compressor housing), be sure to have the appropriate adapters.

Step 1: Prepare Your Vehicle

Park on a level surface and let the engine cool completely—turbocharger and exhaust components can exceed 600°F immediately after a drive. Disconnect the negative battery terminal and isolate the cable to prevent accidental contact. This step protects both you and the Profec B’s electronics during wiring. While the battery is off, inspect the area where you plan to mount the boost controller solenoid (typically near the turbo, wastegate, or strut tower). Clean any oil or dirt with brake cleaner and a rag to ensure the solenoid and lines seal properly.

Step 2: Understand the System Layout

Before touching any vacuum lines, take a moment to identify the key components:

  • Turbocharger compressor outlet – This is where pressurized air leaves the turbo and enters the intake system. Many installations tap a vacuum/boost reference line from a port on the compressor housing or intake piping.
  • Wastegate actuator – A canister-like device attached to the turbine housing. A hose runs from the actuator to what is normally a boost source. The Profec B intercepts this hose to regulate wastegate opening.
  • Intake manifold – In most applications, you will connect one of the controller’s vacuum ports to manifold vacuum or a dedicated boost reference line to sense actual manifold pressure.
  • Profec B main unit – The in-cabin controller that displays boost and allows adjustments via buttons.
  • Profec B solenoid – The black, solenoid-operated valve that physically controls the pressure signal to the wastegate. It mounts in the engine bay.

Refer to the Greddy manual for the specific port labeling (COM, NC, NO) on the solenoid. A common configuration: the “COM” port connects to the wastegate actuator, “NC” (normally closed) connects to the boost source (e.g., turbo compressor outlet or intake manifold), and “NO” (normally open) vents to atmosphere or is capped depending on the setup. Double-check your manual, as variations exist between Profec B versions.

Step 3: Install the Solenoid in the Engine Bay

Locate a Mounting Spot

Choose a location that is well-ventilated, away from direct exhaust heat, and protected from road debris. Common spots include the inner fender, strut tower brace, or a custom bracket near the intake. Use the supplied bracket and screws—drill pilot holes if necessary. Ensure the solenoid is oriented so that the hose barbs point downward or sideways to prevent moisture accumulation.

Connect the Vacuum Hoses

Cut lengths of silicone vacuum hose to connect the solenoid ports to the wastegate actuator and boost reference source. Keep hoses as short as possible (under 18 inches if feasible) to reduce lag. Use zip ties to secure hoses away from moving parts and sharp edges. Route the solenoid’s electrical harness toward the cabin where the main unit will be installed. Leave a few inches of slack for vibrations.

Step 4: Wire the Profec B into the Vehicle

Plan the Wire Runs

The Profec B requires a +12V constant power, ignition-switched power (often from the fuse panel), a ground connection, and a signal wire for the solenoid. Some versions also have a wire for an optional warning light or a speed-based boost reduction feature (for different gears).

Connect Power and Ground

Run the +12V constant wire (red) to the battery positive terminal via a fused link—Greddy typically includes a 3A fuse in line. For the ignition-switched wire (white/blue stripe), tap into a circuit that is only live when the key is in the “ON” or “RUN” position. The radio, cigarette lighter, or a dedicated fuse tap can work. Use a multimeter to verify the circuit before connecting. The black ground wire should attach to a clean, unpainted chassis bolt. Crimp a ring terminal on the ground wire and secure it.

Route the Solenoid Harness

The solenoid’s three-wire harness (usually with a small plug) connects to the main control unit. Pass it through a grommet in the firewall—often there is an existing hole near the steering column or passenger footwell. Apply a small dab of silicone around the grommet to seal the cabin from fumes and moisture. Inside the car, plug the harness into the corresponding connector on the back of the Profec B. Tuck excess wire under the dash and secure with zip ties.

Step 5: Mount the Controller in the Cabin

The Profec B main unit is compact and can be mounted in several locations: in a center console cubby, above the rearview mirror, or on a custom pod on the A-pillar. Choose a spot that is visible while driving (to monitor boost) but does not obstruct controls. Use the supplied double-sided tape or bracket. If using screws, be careful not to damage any wires or airbag components behind the panel. Once mounted, connect the power and solenoid harness you already routed.

Step 6: Reconnect the Battery and Perform Initial Checks

Reattach the negative battery terminal. Before starting the engine, visually inspect all vacuum lines and electrical connections. Turn the key to the “ON” position (do not start). The Profec B screen should illuminate and display something like “0.0” or “OFF.” If the screen remains dark, check the fuse and wiring. If the solenoid clicks or the screen flickers, recheck your ground and power connections.

Step 7: Configure the Boost Controller

With the engine off but ignition on, begin initial setup. The Greddy Profec B is relatively intuitive but you must understand a few key parameters:

  • Set boost (or “SET BOOST”) – This is your target boost pressure in PSI (or Bar). For a safe starting point, program a value that is 2–3 PSI above your factory wastegate spring pressure. Do not exceed safe limits for your engine and fuel system.
  • Gain – Adjustment for how quickly the solenoid responds to boost build. Higher gain speeds up spool but can cause boost overshoot. Start with a low gain (e.g., 20) and increase incrementally.
  • Boost controller mode – The Profec B typically offers “Hi” and “Lo” settings (or a manual/off mode). Use “OFF” for initial test runs.
  • Warning and limit settings (optional) – Set an overboost warning and a safety cut if you have a throttle cut or fuel cut relay wired.

Follow the specific button sequence in your manual to enter setup mode. Input your initial target boost (e.g., 12 PSI for a stock turbo with 10 PSI spring). Turn the gain to 10. Exit setup and save.

Step 8: Test the Installation

Start the engine and let it idle. The Profec B should now display actual boost pressure—usually near 0 or slight vacuum (negative numbers). Listen for vacuum leaks: a hissing sound could indicate a loose hose clamp or split silicone line. With the engine at idle, use a soapy water spray bottle on each hose junction; bubbles will reveal leaks. Tighten connections or replace damaged hoses.

Now it’s time for a low-load road test. Warm up the engine and find a safe, empty stretch of road. In first or second gear, accelerate gently to 3,000 RPM—the boost gauge should show you running on wastegate spring pressure (the controller is in “OFF” mode). If you see a sudden spike or the car goes into limp mode, abort the test and recheck wiring.

Once satisfied, set the Profec B to “Lo” or “Hi” mode with your target boost. Gradually increase throttle in third gear (common roll racing gear) from 3,000 to 6,000 RPM. Watch the display. The boost should rise smoothly to your programmed target and hold steady within ±1 PSI. If it overshoots or oscillates, reduce gain by 5 points and retest. If boost is lower than expected, check for a pre-existing boost leak or a misconnected vacuum line.

Step 9: Fine-Tuning for Roll Racing

Roll racing demands a boost profile that helps the engine pull hard from mid-RPM to redline. On the Profec B, you can adjust gain to eliminate lag. A typical street/track setup: set gain around 30–50 on a small turbo, lower for large turbos (to avoid spike). Some owners also use the “Start Boost” function (if available) to set the RPM or speed at which the controller begins regulating—this can be used to minimize boost in lower gears for traction, but in roll racing you generally want full boost from engagement.

After each adjustment, repeat a 3rd‑gear pull and log peak boost, boost dip at shifts, and stability. Ideal roll racing boost is flat from 3500 RPM onward. Consider a data logger or consult a dyno if possible. Never exceed boost levels that your fuel system, intercooler, and engine internals are designed to handle—consult a tuner if you are pushing past factory limits.

Troubleshooting Common Issues

ProblemLikely CauseSolution
No boost increase beyond wastegate spring pressure Controller not in active mode; solenoid not wired correctly; vacuum lines reversed Verify the controller is set to “Lo” or “Hi”. Check solenoid port orientation per manual. Confirm power and ground.
Boost spikes or over-boost triggers fuel cut Gain too high; wastegate actuator too small; hose restriction Reduce gain by 10–20 units. Verify vacuum line diameter and length. Upgrade wastegate if necessary.
Controller not responding to button presses Wiring fault; dead controller; loose ribbon cable inside unit Check 12V and ground with multimeter. Re-seat internal connector carefully. Contact Greddy support.
Erratic boost readings on display Loose sensor line; voltage supply fluctuation; faulty solenoid Inspect vacuum line to the Profec B’s internal MAP sensor (in the main unit). Clean electrical contacts. Test solenoid with a 12V signal.
Boost drops off at high RPM Turbo is out of its efficiency range; intake restriction; boost leak Check intake and exhaust flow. Pressure test intercooler piping. Consider a larger turbo upgrade.

Roll racing on public roads is illegal and dangerous. This guide is intended for use on closed courses, private tracks, or legal racing events. Always wear safety equipment and obey local laws. Modifying boost pressure can increase stress on engine components; ensure your cooling, fueling, and internals are up to the task. If you are unsure, consult a professional tuner.

Final Thoughts and Resources

Installing a Greddy Profec B boost controller is a straightforward upgrade that yields noticeable gains in responsiveness and power—ideal for roll racing where every split second counts. The key to a successful installation lies in careful routing, solid electrical connections, and patient tuning. By following this expanded guide, you can confidently transform your vehicle’s boost profile from conservative to competitive.

For further reference, consult the official Greddy Profec B product page for the latest manuals and firmware updates. The community at RollRacingForum.com offers tuning tips specific to various platforms. And if you need a deeper dive into boost controller theory, Garrett Motion’s tech articles provide excellent background on wastegate operation and solenoid function.