So you’ve got an F20B engine and you’re thinking about adding a turbo. It’s a fantastic way to make serious power from Honda’s high-revving DOHC VTEC engine. The first question on your mind is probably, “What Turbo Do I Need For A F20B?” This guide will walk you through everything you need to know to make the right choice, from understanding your engine’s potential to picking the perfect turbocharger for your goals.
The F20B is a special engine, often found in the Japan-spec Honda Accord SiR-T and Torneo. It’s related to the H22 but has a unique cylinder head and lower compression, which actually makes it a great candidate for forced induction. Choosing the right turbo isn’t just about max horsepower; it’s about how the power feels and how reliable your setup will be.
What Turbo Do I Need For A F20B
There’s no single correct answer, but the best turbo for most F20B builds is a modern, ball-bearing turbo in the 50-62mm compressor wheel range. This size offers a excellent balance of quick spool and strong top-end power, perfectly matching the VTEC engine’s character. Popular choices include the Garrett GTX2860R, the BorgWarner EFR 6258, or comparable turbos from Precision Turbo or Turbosmart.
Your choice depends heavilly on your power goals, budget, and how you want the car to drive. A smaller turbo will give you quicker acceleration from low RPMs, while a larger one will make more peak power but take longer to spool.
Understanding Your F20B’s Foundation
Before you even look at turbo models, you need to assess your engine’s health and setup. The F20B is strong, but it has limits.
Its factory lower compression (around 9.6:1) is a good start for boost. However, the factory cast pistons and rods become the weak link after about 350-400 horsepower. For a reliable build, you must consider internal upgrades if your goals exceed this.
You’ll also need to think about supporting mods. A turbo kit is just one part of the puzzle. Here’s what else is non-negotiable:
* Fuel System: Larger fuel pump, higher-flow injectors (often 550cc to 1000cc), and a way to control them, like a Hondata or AEM engine management system.
* Exhaust: A quality turbo manifold (often a T3 or T4 flange), and a free-flowing downpipe and exhaust system.
* Cooling: A large front-mount intercooler and possibly an oil cooler are essential.
* Tuning: This is the most critical part. A professional tune on a dyno is what makes a setup safe and powerful.
Defining Your Power and Driveability Goals
Your target horsepower is the biggest factor in choosing a turbo. Be realistic about what you want and what your budget can handle.
Street-Friendly Daily Driver (300-400 WHP)
This is the sweet spot for many. Power is substantial, spool is quick, and stress on the stock internals is manageable with a good tune.
* Turbo Size: Look for a turbo with a compressor wheel around 50-57mm.
* Examples: Garrett GT2860RS (Disco Potato), BorgWarner EFR 6258, Precision Turbo PTE 5558.
* Characteristics: These turbos will often start making boost by 3000 RPM and pull hard to the redline. The powerband feels very natural and responsive, perfect for a street car.
Aggressive Street / Weekend Track Car (400-500 WHP)
This range requires built internals (forged pistons and rods) for long-term reliability. The power is serious and transforms the car.
* Turbo Size: Step up to a 57-62mm compressor wheel.
* Examples: Garrett GTX3071R, BorgWarner EFR 6758, Precision Turbo PTE 5858.
* Characteristics: Spool will come a bit later, around 3500-4000 RPM, but the top-end charge is brutal. You’ll need stronger clutch, axles, and likely a transmission upgrade to handle the torque.
All-Out Drag or Max Effort Build (500+ WHP)
This is a dedicated build. Everything from the bottom end to the transmission needs to be reinforced.
* Turbo Size: 62mm and larger compressor wheels.
* Examples: Garrett GTX3576R, BorgWarner EFR 7163, Precision Turbo PTE 6266.
* Characteristics: Lag is present but manageable, with massive boost coming on strong in the mid-range and absolutely pulling to the limiter. The focus here is on peak power for specific applications.
Key Turbo Specifications Explained
When you look at turbo models, you’ll see a bunch of numbers and codes. Let’s break down what matters for your F20B.
Compressor Wheel Size: This is the inducer diameter (in mm) and gives a general idea of airflow capacity. Bigger wheel = more potential power, but slower spool.
Turbine Housing A/R (Area/Radius): This is crucial for response. A smaller A/R (like 0.63) will spool faster but may choke the top-end. A larger A/R (like 0.82) spools slower but allows for more high-RPM power. For an F20B, a divided T3 turbine housing with a 0.63 or 0.72 A/R is often a great match.
Ball Bearing vs. Journal Bearing: Ball bearing turbos spool significantly faster and are generally more efficient. They cost more but are worth it for a responsive street engine. Journal bearing turbos are more budget-friendly but have more rotational friction.
Turbine Housing Flange: This must match your manifold. Common flanges are T25, T3, and T4. T3 is a very common and versatile choice for the F20B.
Step-by-Step Turbo Selection Process
Follow these steps to narrow down your options.
1. Set a firm horsepower goal and budget. Include all supporting mods and tuning in this budget.
2. Prepare your engine. Do a compression test. Decide if you will stay stock internals or build them based on your power goal.
3. Research compressor maps. While technical, looking at a turbo’s compressor map (available from manufacturers) shows its efficiency islands for your engine’s airflow. You want your target boost level to be in the highest efficiency zone.
4. Read build threads. Look for forums where others have turbocharged their F20B. Real-world results and dyno graphs are invaluable.
5. Choose a reputable brand. Stick with known names like Garrett, BorgWarner EFR, Precision, or Turbosmart for core components. Avoid obscure, cheap turbos.
6. Match the entire system. Ensure the turbo’s flange matches your chosen manifold and that the downpipe you plan to use is available for that turbo’s outlet configuration.
Supporting Mods You Cannot Skip
The turbo won’t work alone. Here is a checklist of critical items:
* Engine Management: Hondata S300 or a standalone ECU like AEM Series 2.
* Fueling: Walbro 255lph fuel pump, RC or ID injectors sized for your goal, and an adjustable fuel pressure regulator.
* Ignition: Fresh OEM or one step colder spark plugs.
* Exhaust: Mandrel-bent turbo manifold (not log-style), 3-inch downpipe and exhaust.
* Cooling: Front-mount intercooler with short piping, silicone couplers, and T-bolt clamps.
* Drivetrain: Upgraded clutch and lightweight flywheel. Consider stronger axles for 400+ WHP.
Installation and Tuning Considerations
Installation is straightforward if you’re mechanically inclined, but take your time. Key tips include:
* Prime the turbo before first start by cranking the engine with the fuel pump fuse pulled to get oil flowing.
* Ensure all intercooler piping is secure; boost leaks are a common issue.
* Use a quality oil feed line with a restrictor if needed (especially for ball bearing turbos) and a free-flowing oil return line.
The tune is everything. Do not try to run the car on a base map for long. Get it to a tuner who has experience with turbocharged Honda engines. A proper dyno tune will ensure the right air/fuel ratios, ignition timing, and VTEC engagement for a safe, powerful result.
Common Mistakes to Avoid
* Choosing a turbo that’s too big. This leads to excessive lag and a poor street experience.
* Neglecting the fuel system. Running lean under boost will destroy your engine in seconds.
* Cheaping out on the manifold. A poor-quality manifold will crack and fail.
* Skipping the intercooler. Intake temperatures will skyrocket, killing power and risking detonation.
* Forgetting about drivetrain upgrades. The stock clutch will slip immediately with added torque.
FAQ Section
What size turbo is best for a stock F20B?
For a stock internal F20B, a turbo in the 50-57mm range (like a GT2860RS) is ideal. It can make 350-380 reliable wheel horsepower with proper supporting mods and a conservative tune.
Can the F20B handle boost?
Yes, the F20B can handle boost quite well due to its lower compression. The factory bottom end is generally considered safe for up to 350-400 wheel horsepower with a excellent tune. Beyond that, forged internals are recommended for reliability.
What’s better for an F20B: turbo or supercharger?
This is personal preference. A turbocharger typically offers more peak power potential and tuning flexibility. A supercharger (like a centrifugal kit) gives linear, instant throttle response but often makes less peak power and can be less efficient. The turbo is the more common choice for maximum power.
How much boost can a stock F20B run?
On pump gas (93 octane), a stock F20B can typically run 8-12 psi safely with a perfect tune, intercooler, and all supporting mods. This depends heavily on the turbo size and the tuner’s approach. Always tune conservatively on stock internals.
Does VTEC still work with a turbo?
Absolutely. In fact, it’s a advantage. Your tuner will set the VTEC engagement point to work with the boost curve. Often, VTEC is set to engage at a slightly higher RPM to help spool the turbo, then the combination of boost and VTEC creates a massive power surge.
Choosing the right turbo for your F20B is a balance of science and your personal driving preferences. By defining your goals, understanding the key specs, and investing in the required supporting components, you can build a forced induction setup that brings out the engines full potential. Remember, patience and attention to detail in both parts selection and tuning are what seperate a successful, fun project from a frustrating one. Take your time, do the research, and you’ll end up with a incredibly fast and rewarding car.