If you've spent any time around performance cars, you've heard people talking about "boost." Turbochargers and superchargers are the holy grail of power upgrades—nothing adds horsepower like forced induction. But if you're new to the concept, the terminology can be confusing. What exactly is boost? How do turbos work? What's the difference between a turbo and a supercharger?
This guide breaks down everything you need to know about forced induction in simple, practical terms. Whether you're considering adding boost to your car or just want to understand what your car already has, this article will give you the foundation you need.
What is Boost?
Let's start with the basics. Boost is simply air pressure above atmospheric pressure. At sea level, atmospheric pressure is about 14.7 psi (pounds per square inch). When your gauge reads "0 psi boost," your engine is running at normal atmospheric pressure—also called "naturally aspirated."
When a turbocharger or supercharger compresses air and forces more of it into your engine than would normally enter, you create boost. If your gauge reads "10 psi," that means you're running 10 psi above atmospheric pressure, or 24.7 psi absolute (atmospheric + boost).
Why More Air Equals More Power
Internal combustion engines make power by burning fuel. But fuel can't burn without oxygen. The more air (oxygen) you can cram into the combustion chamber, the more fuel you can burn, and the more power you make.
A naturally aspirated engine relies on the pistons moving down to create a vacuum that sucks air into the cylinders. This is limited by atmospheric pressure—you can't suck in more air than the atmosphere will provide.
Forced induction uses a compressor (turbo or supercharger) to actively force air into the engine under pressure. More air molecules in the same space = more oxygen = more power. It's that simple.
Turbochargers vs Superchargers: The Fundamental Difference
Both turbos and superchargers compress air to create boost, but they're powered in completely different ways.
Turbochargers: Exhaust-Driven
A turbocharger uses exhaust gases to spin a turbine, which drives a compressor wheel. The hot exhaust leaving your engine passes through a turbine housing, spinning the turbine wheel at extremely high speeds (often 100,000+ RPM). The turbine shaft is connected to a compressor wheel in the cold side of the turbo, which compresses intake air.
Key advantages:
- Free power source: Uses exhaust energy that would otherwise be wasted. No parasitic drain on the engine.
- Efficiency: Turbos are very efficient—they're using energy that's already been spent.
- Massive power potential: Turbos can create huge amounts of boost. 20-30+ psi is common in serious builds.
- Scalability: Easy to upgrade by changing turbos or adding a second turbo.
Key disadvantages:
- Turbo lag: Takes time for exhaust flow to build and spin the turbo up to boost-making speed. There's a delay between throttle input and boost delivery.
- Heat: Turbos operate in extremely hot conditions. Exhaust heat management is critical.
- Complexity: Requires custom exhaust manifolds, intercooling, oil feed/return lines, wastegate control, etc.
- Installation cost: Custom turbo installs are labor-intensive and expensive.
Superchargers: Belt-Driven
A supercharger is mechanically driven by a belt connected to the engine's crankshaft. As the engine spins, it drives the supercharger, which compresses air and forces it into the intake.
Key advantages:
- Instant boost: No lag whatsoever. Boost is available from idle to redline because the supercharger spins proportionally to engine speed.
- Linear power delivery: Power increases smoothly with RPM. Very predictable and easy to drive.
- Bolt-on simplicity: Many supercharger kits are true bolt-on systems with everything included.
- Reliable: Fewer moving parts exposed to extreme heat compared to turbos.
Key disadvantages:
- Parasitic power loss: The supercharger is driven by the engine, stealing 50-80 hp just to turn the blower. This reduces net power gains.
- Heat generation: Compressing air creates heat. Superchargers generate significant heat, requiring good intercooling.
- Boost limited by pulley size: To increase boost, you need to change pulleys, which has practical limits.
- Cost: Quality supercharger kits are expensive, often $7,000-$10,000+.
How Boost Creates Power
Let's talk numbers. How much power does boost actually add?
There's a rough formula enthusiasts use to estimate power gains from boost:
HP gain ≈ (Boost PSI / 14.7) × Base HP
For example, if your naturally aspirated engine makes 400 hp, and you add 10 psi boost:
- (10 / 14.7) × 400 = 0.68 × 400 = 272 hp gain
- New total: 400 + 272 = 672 hp
In reality, it's not quite that simple. You'll lose some power to heat, inefficiency, and parasitic drag (for superchargers). A more realistic multiplier accounting for these losses is:
HP gain ≈ (Boost PSI / 14.7) × Base HP × 0.85
Using the same example with the efficiency factor:
- (10 / 14.7) × 400 × 0.85 = 231 hp gain
- New total: 400 + 231 = 631 hp
This is much closer to real-world results. We typically see 50-75% of theoretical boost gains depending on the setup, fuel, and tuning quality.
Critical Components of a Boost System
Whether you're going turbo or supercharger, several supporting components are critical for safe, reliable boost.
1. Intercooler
When you compress air, it heats up dramatically. Hot air is less dense (fewer oxygen molecules per volume) and more prone to detonation. An intercooler is a heat exchanger that cools the compressed air before it enters the engine.
There are two types:
- Air-to-air intercooler: Uses ambient air flowing through fins to cool the charge air. Simple, reliable, common on most turbo and supercharger setups.
- Air-to-water intercooler: Uses coolant to remove heat from charge air. More efficient but more complex. Common on high-end supercharger kits.
Without an intercooler, you'll lose significant power to heat and risk detonation. Never run boost without intercooling.
2. Fuel System Upgrades
More air requires more fuel to maintain proper air-fuel ratios. Your stock fuel system is sized for naturally aspirated power levels and will max out quickly under boost.
Required upgrades typically include:
- Larger fuel injectors: Stock injectors often can't flow enough fuel for boosted applications. Plan to upgrade to high-flow injectors.
- Upgraded fuel pump: The pump must supply enough volume to feed the larger injectors at the required pressure.
- Fuel pressure regulator: Some applications need an adjustable or rising-rate FPR to maintain proper fuel pressure under boost.
3. Engine Management and Tuning
This is the most critical component. Your engine's ECU must be reprogrammed to properly control fueling, ignition timing, and boost levels.
Running boost without a proper tune will destroy your engine. The ECU doesn't know you've added boost and will run dangerously lean air-fuel ratios and too much timing, causing detonation and melted pistons.
Professional tuning is non-negotiable. Budget $800-1,500 for a quality boost tune.
4. Supporting Engine Hardware
Depending on boost levels, you may need internal engine upgrades:
- Low boost (6-10 psi): Most modern engines handle this on stock internals with proper tuning.
- Moderate boost (10-15 psi): Stock internals often adequate, but pushing the limits. Conservative tuning recommended.
- High boost (15+ psi): Forged pistons, rods, and upgraded head studs typically required for reliability.
Understanding Boost Pressure
How much boost should you run? There's no universal answer—it depends on your engine, fuel, and goals.
Conservative Boost Levels (Stock Internals)
If you want to keep your stock engine intact and reliable, here are safe boost levels on quality pump gas (93 octane) with proper tuning:
- LS/LT engines: 6-10 psi safely. 12-15 psi pushing limits.
- Coyote 5.0: 8-12 psi safely. 15+ psi requires careful tuning and good fuel.
- HEMI 5.7/6.4: 6-10 psi safely on stock blocks. Hellcat engines built for more.
- BMW N54/N55/B58: Stock turbos max around 18-22 psi. Upgraded turbos can run 25-30+ psi.
Race Gas or E85
With race fuel or E85, you can safely run significantly more boost thanks to higher octane and knock resistance:
- E85 typically allows 30-50% more boost than 93 octane pump gas.
- Race gas (100+ octane) allows even more but is very expensive.
Common Boost Myths
Let's clear up some common misconceptions about forced induction:
Myth 1: "More boost always equals more power"
Reality: Boost is just air pressure. What matters is airflow (CFM - cubic feet per minute). A small turbo at 20 psi might flow less air than a large turbo at 15 psi. More boost from an inefficient setup doesn't always mean more power.
Myth 2: "Turbos always have lag"
Reality: Modern turbo technology has reduced lag dramatically. Small turbos can provide near-instant response, and twin-turbo setups can eliminate lag almost entirely. While lag exists, it's far less problematic than it was 20 years ago.
Myth 3: "Superchargers can't make as much power as turbos"
Reality: Superchargers can absolutely make huge power. Hellcat Redeyes make 800+ hp with a factory supercharger. The difference is efficiency—turbos are more efficient because they use waste energy, but both can make massive power.
Myth 4: "You need forged internals for any boost"
Reality: Many modern engines handle 6-10 psi boost on stock internals just fine. It's all about tuning and boost levels. Conservative boost with proper tuning is safe on stock motors.
Turbo vs Supercharger: Which Should You Choose?
After explaining both, here's my recommendation based on use case:
Choose a Turbocharger If:
- You want maximum power potential and efficiency
- You're building a dedicated track or drag car
- You don't mind turbo lag and can work with the power delivery
- You plan to run very high boost levels (15+ psi)
- You're doing a ground-up custom build anyway
Choose a Supercharger If:
- You want instant throttle response with no lag
- The car is street-driven and you value drivability
- You want a bolt-on kit that's easier to install
- Linear power delivery is important to you
- You're adding boost to a modern car (Mustang, Camaro, Challenger)
What About Factory Turbo Cars?
Many modern performance cars come turbocharged from the factory—BMW M cars, Ecoboost Mustangs, GR Supra, Porsche 911 Turbo, etc. These engines are already optimized for boost and offer easy power gains.
Tuning Factory Turbo Cars
Factory turbo cars typically respond incredibly well to tuning because the hardware is already there. A simple ECU tune can add:
- BMW B58 (Supra): 50-80 hp with just a tune
- Ecoboost 3.5L (F-150): 80-120 hp with tune and bolt-ons
- Porsche 911 Turbo: 60-100+ hp depending on model
For these cars, upgrading turbos, downpipes, and intercoolers can push power even further with proper tuning.
Real-World Boost Examples
Here are some actual builds we've done at Raw Exotics to illustrate real-world boost performance:
Example 1: 2019 Mustang GT + Whipple 2.9L
- Before: 420 whp naturally aspirated
- After: 675 whp at 8.5 psi (93 octane)
- Gain: 255 whp (60% increase)
- Character: Instant power everywhere, incredible street car
Example 2: 2015 Charger R/T 5.7 HEMI + Single Turbo
- Before: 370 whp naturally aspirated
- After: 650 whp at 12 psi (E85)
- Gain: 280 whp (75% increase)
- Character: Slight lag, but explosive top-end pull
Example 3: 2020 BMW M340i (B58 Stock Turbo)
- Before: 335 whp (stock tune)
- After: 420 whp (custom tune, downpipe, intake)
- Gain: 85 whp (25% increase) - Just from tuning existing turbo!
- Character: Smooth, linear, feels like a much bigger engine
Getting Started with Boost
If you're ready to add forced induction to your car, here's the process:
- Define your goals: How much power do you want? What's your budget? How do you use the car?
- Research your platform: What kits are available? What do other owners recommend?
- Choose your system: Turbo or supercharger? Which specific kit?
- Budget for supporting mods: Fuel system, intercooling, tuning, clutch/transmission upgrades.
- Find a reputable shop: Boost installations require expertise. Don't cheap out on installation or tuning.
- Maintain properly: Boosted engines need quality oil, frequent changes, and proper cooling. Maintenance is critical.
"Forced induction is the single best way to add serious power to your car. Whether you go turbo or supercharger, the transformation is incredible. Just make sure you do it right—proper installation, quality parts, and professional tuning are non-negotiable."
Ready to Add Boost?
If you're in Houston and considering adding a turbo or supercharger to your car, we'd love to help. At Raw Exotics, we've installed hundreds of forced induction systems across all platforms—LS, HEMI, Coyote, BMW, and more.
We'll help you choose the right system for your goals and budget, handle the complete installation, and dial in a custom tune that makes power safely and reliably. Call us at (713) 299-1168 or stop by the shop to discuss your boost build.