How Does a Turbo Work?

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Source | Dave_7/Flickr

Auto manufacturers have almost exclusively used turbochargers in sports cars or race cars in the last couple of decades. Considering their main purpose is to provide a large boost in power, that does make a lot of sense. Now that automakers need to improve the fuel economy in vehicles across their lineups, they’ve started using turbocharged engines in daily drivers too.

This rise in popularity is mainly because turbochargers make engines work more efficiently. And when engines don’t have to work as hard, they use less fuel. Fuel-cost savings are among the top benefits of a turbocharger, along with the power output surge it provides.

Despite more widespread use of turbochargers in recent years, there are still a lot of questions about what they do and how a turbo works. We’re going to take a look at the technology behind turbochargers. We’ll also look at how they’ve evolved since they first appeared in a production vehicle back in 1962.

What is a turbo and how does a turbo work?

To understand how a turbo works, you first need to know its components and what each of them does. The two fundamental parts are a compressor and a turbine, forming what is essentially an air pump. The compressor consists of a wheel, a housing, and a diffuser. The turbine, for its part, has a wheel and a housing.

The main goal of a turbocharger is to boost the power output of an engine, without having to increase the engine’s size. Here’s how a turbo provides power:

  1. It takes in exhaust gasses from the engine through its turbine wheel.
  2. This process causes the turbine wheel to start spinning. A shaft connects the turbine wheel to the compressor wheel, causing it to rotate as well.
  3. Once the compressor wheel begins to spin, it takes in ambient air and compresses it.
  4. From there, it sends the compressed air through the compressor housing over to the chambers of the engine.
  5. The compressed air enters the engine’s combustion chambers, providing the engine with more power and torque.

Nowadays, automakers factory-install or offer as aftermarket parts a few different types of turbos. Beyond the basic type of turbo configuration—the single turbo—there are parallel twin turbo configurations, sequential turbos, and quad turbos.

1962 Oldsmobile Cutlass/F85

1962 Oldsmobile Cutlass/F85, Source | Greg Gjerdingen

From the ’62 Oldsmobile Cutlass and Chevrolet Corvair, to Ford’s EcoBoost

The first production car to feature a turbocharged engine was the 1962 Oldsmobile Cutlass. This classic car was powered by a 3.5-liter aluminum V8 engine, with a power output of 215 hp and 300 lb-ft of torque. That same year, Chevrolet rolled out a turbocharged Corvair. Both became trendsetters for turbocharged cars. In 1975, Porsche introduced its first turbocharged model: the 911 Turbo, helping make the technology famous around the globe.

For the past few years most global automakers launched models that use a turbocharged engine, with Ford’s EcoBoost technology arguably leading the way. Ford includes EcoBoost engines across most of its lineup, including the F-150, sports cars, family sedans, and SUVs. Its main turbo-engine competitors include Audi, Chevrolet, and Volvo. The market should continue to grow—many European and US automakers say they plan to invest in this technology for years to come. (Japanese manufacturers have focused more on hybrids and electric vehicles.)

Lower fuel consumption, higher power output—but at a cost

Like with most vehicle technologies, turbochargers have their drawbacks. To create power, the turbocharger supplies the engine with more condensed air by using the exhaust energy from the engine, which would otherwise be wasted. Turbocharged engines deliver the same amount of power as non-turbocharged engines twice their size. Because of that, automakers don’t have to install larger engines.

But there’s a reason why turbos have yet to become a staple in every single car. Turbocharged engines are more expensive to build than their naturally aspirated counterparts. Creating an efficient and durable turbo is a complicated engineering process. That’s why they were usually found in luxury, high-performance cars. Only recently have cost reductions helped get them into more mainstream models.

Aside from high production costs, there are also a couple of downsides to turbos. One of the biggest drawbacks from a consumer perspective is turbo lag. Turbo lag is the time it takes for a turbocharger to start supplying the engine with an increased pressure and, consequently, a power boost. A turbocharger only provides a boost after it reaches a certain RPM threshold. Turbo lag is the time it takes an engine to reach that threshold after idling, or from a low speed.

Reaching the threshold for a power boost can lead to another downside of using a turbocharger. Once it reaches the threshold, the turbo speedily delivers an increase in power. That power boost can make the car difficult to control, which makes turbos potentially dangerous if a driver doesn’t know what to expect.

Sticking around

Even with the pitfalls, the consensus in the automotive industry seems to be that turbos are here to stay, and they’ll continue to get more popular in the near future. Automakers face strict fuel economy standards in many markets around the globe, prompting them to invest in fuel-saving technologies like turbochargers. Good thing we think they’re pretty fun.

What about you? Are you a fan of turbos? Share your tips and experience in the comments.

 

The Weird World of Intake Manifolds

 

Intake manifolds are often a hot rodder’s upgrade part but are otherwise mostly ignored. Every minivan on the road has an intake manifold feeding an air and fuel mixture to the cylinder heads, so they don’t have the sexy and complex reputation of a turbocharger. Still, throughout the history of internal combustion, there have been several intake manifolds that left us scratching our heads. Here are a few of the weirdest.

Source | Andy Jensen

If You Can’t Dodge It, Ram It

This one causes a puppy-head-tilt reaction in everyone who sees it for the first time. The Chrysler B-block was a standard and unexciting people-moving engine by 1960 until it was topped by the unique cross-ram manifold. The dual four-barrel carbs sit way out over the exhaust manifolds and run the air charge through a gigantic, 30-inch runner to the opposite side intake port. Yup, the driver’s side feeds the passenger side cylinders, and vice versa. Chrysler rated the 361 cross ram at 310 horsepower, which wasn’t bad considering the muscle-car wars hadn’t really started yet. While it wasn’t a drag strip warrior due to losing power in higher RPMs, the cross-ram-equipped car had an impressive 435 lb-ft of torque down low, thanks to the extremely long runners.

Defying Gravity

What do you do when the traditional intake manifold world gets boring? Turn it upside down — or in this case, sideways. Sidedraft carbs were needed due to packaging constraints on cars with average-size engines in a small engine bay, like the Jaguar XK120 and Datsun 240Z. While North America was familiar with a standard Holley sitting directly on the manifold, the sidedraft style meant the Weber or SU carbs were mounted 90 degrees sideways, feeding a vertically mounted intake manifold. It’s easy to assume that gravity pulls fuel from the carb bowl into the manifold, which means sidedrafts shouldn’t work. Fortunately, the Venturi effect, which draws the air and gas mixture into the engine, is far more influential than gravity, meaning the intake manifold works just the same as if it were installed on top of the engine. If you want really weird-looking, there’s aftermarket kits to put sidedrafts on a rotary.

Truck Engine in a Sports Car

Remember the ’80s? No? Well, lucky you. The rest of us suffered for a bit while the manufacturers tried to figure out how to balance horsepower with emissions. GM’s solution was electronic-fuel injection with the tuned port intake (TPI) manifold. The distinctive long curved runners connecting the plenum to the lower manifold are a source of the engine’s torque, with a tuned length that takes advantage of pulses in the air charge at low and mid RPM. Right as the pulse of air is about to slam into the closed intake valve, it opens, sending a blast of slightly compressed air into the chamber. While only generating 245 horsepower, the TPI could make an impressive-for-the-time, 345 lb-ft of torque. If that isn’t oddball enough for you, the ’85 to ’88 V8s had nine fuel injectors.

Looks Like a Bad Day at the Factory

A transverse (sideways) mounted intake manifold make sense on a transverse mounted engine, like the modern Toyota Corolla. The cylinders are in a line between the wheel wells, and the intake manifold lines up with the cylinders left to right. Things get quite a bit more confusing when looking at the engine bay of the Infiniti Q45. The Nissan VH series engines were longitudinal (front to back) V8s driving the rear wheels but topped by a spider-like intake manifold sitting sideways as if it were front wheel drive. The reasoning behind the strange layout is unclear, but it was probably for packaging or emissions. This reminds us that the orientation of the intake manifold does not always determine the drive wheels. For further proof, look to the ’90s Acura Legend. While the engine drives the front wheels, the longitudinally mounted manifold suggests the rear wheels are driven. Oddly, this layout in a modern Japanese EFI sedan recalls the classic Oldsmobile Toronado.

While these oddities are no longer in production (excluding some as aftermarket upgrades), they solved an engineering dilemma of their times.

If you know of any other unusual intake manifolds that should be on this list, make sure to let us know in the comments.

Ways to Boost Power Without Breaking the Bank

Lotus intake

Much like an elite athlete’s ability to rapidly breathe allows them to perform stronger, so it goes with your car’s engine. Whether you drive a ’69 Chevelle or an ’09 Civic, the same principle applies. Get more air in and out, and your engine will make more power and run stronger. This is why forced induction (i.e. turbocharging and supercharging) is so popular as a means for, literally, pumping up an engine’s output. These modifications can easily cost $5,000 and up. But there are plenty of ways to help your engine breathe like an Olympic decathlete without getting into debt up to your eyeballs. Consider these bolt-on mods that will give you the best bang for your buck.

Edelbrock Pro-Flo 1000

Edelbrock Pro-Flo 1000

Going with a less-restrictive air filter setup than what the factory supplied has long been a staple of performance enthusiasts. Those who own an old American car from the ’60s and ’70s typically favor a round, open-element air cleaner that sits over that carburetor. Some classic muscle cars came standard with these types of filters, or even trick hood scoops that funneled colder, outside air to the intake. More often than not though they have a closed housing that breathes through a snorkel-like fixture sticking out of its side. Other options for those golden oldies include Edelbrock’s iconic, triangular “Pro-Flo 1000” (formerly known as the “Lynx”) open-element filter.

K&N Cold Air Kit

K&N Cold Air Intake Kit

When fuel injection became widespread in the ’80s, air filter assemblies took on more complex configurations that continue to this day. The latter is due chiefly to being equipped with various sensors that keep tabs on things like intake air temperature and velocity, so the computers can adjust fuel metering accordingly. The air filters themselves are typically buried within black plastic boxes. The aftermarket quickly came to the rescue with low-restriction, cold-air kits that typically feature a semi-conical, open-element filter. K&N, in particular makes well-engineered kits that are known for their high quality and wide range of applications.

Cat-back exhaust systems

Cat-back exhaust systems

Now that your engine can inhale more deeply, it’s time to turn your attention to the exhaling side of the equation—the exhaust. Before model year 1975, when catalytic converters (“cats”, for short) came on the scene to clean up exhaust emissions, the default performance-enhancing setup was pretty straightforward. Exhaust headers ran to true dual exhausts with a crossover. Nowadays, the ideal setup is pretty much the same, albeit with high-flow cats plumbed into the system.

Still, going with a full engine-to-tailpipes system can be rather complicated (ask anybody who’s installed headers) and expensive. Plus, that labor is probably beyond what most shade-tree wrenches can do. The good news is you don’t have to go that far. Those looking for a cost-effective and minimal hassle upgrade should consider a “cat-back” exhaust system. It is just that—a system that bolts on after your car’s catalytic converter(s). With its freer-flowing pipes and lower-restriction muffler(s), a cat-back exhaust system lets your engine exhale easier and sounds pretty cool in the process.

Regardless of what you drive, there are plenty of great choices for a cat-back system. Popular brands include Borla, Dynomax and Magnaflow. Even within each manufacturer’s product line, there’s great variety, sonically speaking. You’ve got systems that are fairly quiet at idle and part throttle that then growl gratifyingly when you step into it. And then you’ve got the more aggressive setups that proudly make their presence known whether you’re burbling at a light on the boulevard or grabbing gears as you rocket up a freeway on-ramp.

Tackling any of these projects in the near future? Leave us a comment to let us know how it went.

Muffler Methodology: Getting the Sound You’re After

Car muffler picture

What’s your sound preference? Mild? Moderate? Aggressive? No sound at all? Maybe you want a different sound depending on what and where you’re driving. You want an aggressive tone for your 1972 Dodge Charger that you lovingly restored, and a “less noticeable” tone for the Subaru Outback you use to shuttle the kids back and forth.

No matter what your harmonic preference or what you’re driving, there’s a muffler that will deliver exactly the sound you’re looking for. Welcome to the world of mufflers and sound enhancements—increasingly popular modifications that can personalize your ride.

A quick history lesson

Mufflers aren’t a new invention. Records from the U.S. Patent Office show that a patent for an engine muffler was awarded in 1897 to Milton and Marshall Reeves of the Reeves Pulley Company in Columbus, Ind. Mufflers in the early 1900s featured a “straight through” design that is still popular today. Essentially those early mufflers consisted of a pipe with holes, wrapped in something similar to steel wool, with the pipe passing through an outer shell. A big change to that early design occurred with a switch to a fiberglass packing material in place of the steel wool.

Contrary to the name, a muffler isn’t just muffling the sound. It’s actually destroying many of the sound waves. But let’s back up for second.

How mufflers work

The two types of mufflers that most DIYers have heard about are a chambered muffler and a straight through or “glasspack” muffler. Here are the differences between the two (and a third, just for fun):

  • In a chambered muffler, the sound waves generated by the engine at the end of the exhaust stroke enter the muffler and bounce around the muffler’s various chambers. As they do, they encounter friction which destroys some of the sound waves. Some of the sound waves that aren’t destroyed by friction bounce off a chamber wall and form a sound wave that’s an exact opposite. Those two sound waves cancel each other out, further reducing the noise that the vehicle produces.
  • In the straight-through muffler design, the sound waves pass through a straight pipe, with some of the waves being absorbed by the material surrounding the pipe, much like the earliest mufflers.
  • A third type of muffler design is a turbo style muffler in which the exhaust gases are forced into an s-shaped pattern and are peeled off and deadened by the muffler material.

Different types of mufflers yield different sounds, and that’s where personal preference and the type of vehicle enter the picture. Case in point, you’ll find more glasspacks on vintage muscle cars than you would on a custom Honda Civic.

Similarly, chambered mufflers deliver their own unique sounds depending on how many chambers they have and the chamber configuration, both of which determine which sound waves die and which escape and are heard.

Backpressure and its effect on sound

The other consideration when choosing a muffler and exhaust system modification is, of course, backpressure. All those twists, turns and holes that the hot exhaust gases are forced through in the muffler slow down and restrict the gases’ migration toward the tailpipe. That restriction results in increased pressure, which forces the engine to work harder to expel the gas, which leads to a reduction in power. Less pressure equals more power, and more sound.

Begin your research by listening to as many different muffler sounds as you can, like the sound test of these eight Flowmaster mufflers that range from mild to wake-the-neighbors. Choose the one you like, and rest easy knowing you can always change up the sound if you get tired of it. Or get too many complaints. To really customize your muffler’s sound, read this.

What are my options?

Thanks to advancements in muffler design, you can now choose what kind of sound you prefer and even how loud it is. Most late model cars have a bolt-on exhaust system after the catalytic converters, so installing a new system that’s engineered for your specific vehicle couldn’t be easier. Many manufacturers now offer custom outlets, so you can choose one that matches your ride’s exterior.

The muffler is just one popular modification when it comes to tweaking the exhaust system, with headers, catalytic converters and tailpipes presenting other options. Whatever you decide to modify, you’ll be in good company because exhaust system upgrades are increasingly popular and there are plenty of well-known suppliers in the game, including Walker, Flowmaster, and Magnaflow.

Have you modified your muffler? Leave us a comment and tell us about your experience.

Make Your FR-S or BRZ As Fast As It Should Be

Scion FR-s

Scion FR-S

The Toyota 86, known as the Scion FR-S and Subaru BRZ in the States, promised a return to the good old days, when you could get a cool, rear-drive sport coupe for a reasonable price. Of course the “86,” or hachiroku in Japanese, is a reference to the iconic RWD Corolla coupes from the ’80s. With bloodlines like these, Toyota and Subaru couldn’t miss.

But they did. Hard. Because the modern-day hachiroku just doesn’t have enough muscle. The 2.0-liter boxer four under the hood is rated at 200 horsepower and a measly 151 lb-ft of torque. It makes some sporty noises when you wind it out, but there’s no force behind it. The FR-S and BRZ are not fast cars, which is a shame, because the target demographic loves fast cars.

So what’s a power-hungry FR-S or BRZ owner to do? Slap a turbo on it! Here are two great kits that’ll turn your ride into a monster right quick.

Turbocharging the Scion FR-S or Subaru BRZ

Subaru BRZ

For mega aftermarket power, a turbo kit is the way to go. The peak output with some of these kits is explosive. Of course, they use more oil, and any modified car requires extra maintenance. But a lot of folks have been running turbo setups on 86s for thousands of miles with no issues. It’s a robust foundation for a build. As a point of entry, check these two kits out.

FA20Club Stage 1 ($3,499)

FA20Club is one of the big names you see on the hachiroku boards, and for good reason. They pack a lot of value into their kits. The Stage 1 is their entry-level setup, which they say is “capable of up to 280whp without fuel mods.” That’s a cool 115-hp gain over stock power at the wheels. If you think about the power-to-weight ratio that offers, we’re approaching Porsche Cayman territory. Not bad for a few grand.

Dynosty Turbo Build ($17,914)

Ready to roll up your sleeves? Let’s get serious and quintuple the price of the FA20Club kit with this well-regarded Dynosty setup. If you’re up for it, an easy 400+ whp can be yours, and that puts your hachiroku in rarefied territory indeed. See, these cars in stock form weigh in at about 2,800 pounds, maybe a little less. Now consider the new C7 Corvette, making 460 hp for 3,300 pounds. If you do the math, the 86 actually has a better power-to-weight ratio than the Vette. Maybe spending $45 grand or so on a Japanese sport coupe isn’t so silly after all.

Looking for additional ways to boost power to your vehicle? Read about less expensive options, including high performance exhaust mufflers.

Are you sold on turbocharging as the answer? Anyone want to speak up for superchargers? Leave us a comment.

Unlock Your Engine’s Hidden Horsepower

Hot Wheels CarI’m sure you can all relate. You buy this performance car and do your custom bits, but there’s still something missing. In my case, it all came down to actual performance when I punched the gas. For a while, it just frustrated me until I decided to look further…what I found was that I was only using a portion of my engine’s power!

If you’ve been frustrated knowing that your engine has unused power and did something to unlock that power, this is the place to share your success and tips with your fellow tuners, and make yourself look like a genius while you’re at it.

Many vehicle manufacturers are ultra conservative when it comes to programming engine control units (ECU), also known as the control module or the engine control computer at the factory. They’re not going to program the control module so that the vehicle runs at its maximum power capabilities, in part because they’re concerned with things like the vehicle warranty, emissions, and fuel economy. Their conservative settings, however, leave you with a vehicle that isn’t producing as much power as it could. How frustrating is that? The solution? Well, there are quite a few.

A lot of you are probably thinking, “ECU chip tuner” or “reflash” right about now. That seems to be the common wisdom when it comes to increasing horsepower by modifying the control module. For the uninitiated, an ECU basically controls how the engine goes about its business of producing and delivering power, including air/fuel ratio, ignition timing, idle speed, valve timing, and RPMs.

Back in the day, if you wanted to do some car tuning and change the ECU’s parameters, you had to actually change computer chips, physically swapping them out with newer chips that had software featuring the performance parameters you wanted. Today, one can install new software that changes the ECU’s operating parameters simply by plugging into the OBDII port. Boom. A few keystrokes later and you just raised the rev limit, governed top speed, and tuned the air-to-fuel ratio.

What about switching out the engine control computer entirely with a new one instead of just reprogramming it? Is  a new control module an option?

A couple people, including Ethan Campbell, a Roanoke, Virginia-based tuner toying with a ‘96 Miata, have mentioned the MegaSquirt PNP ECU (MSPNP2) as one possibility for completely replacing the stock engine control computer. Campbell’s winter project is taking an engine with a VVT head from a ’99 Miata and installing it into his ’96 and adding a MegaSquirt ECU. MegaSquirt describes the product as taking “over the functions the stock ECU provides – fuel control, ignition control, and various other outputs – and lets you adjust these yourself by connecting a laptop to the MSPNP2.”

Another car-tuning option to increase engine performance is Accesstuner from Cobb. The manufacturer describes the software as allowing “the user to get into the heart of the OEM ECU and create custom calibrations for vehicles equipped with virtually any performance modification. The end result is a tune that is custom tailored to the vehicle’s unique modifications, producing maximum power gains while maintaining the drive-ability and sophistication inherent in the OEM ECU.” Anyone tried it?

What about turbocharging as the car-tuning option? I know that turbocharging a non-turbo car is a viable option for increasing horsepower, but it’s also one that’s accompanied by a whole host of other considerations, including boost level, compression ratios and avoiding knock, that have to be planned for to avoid engine damage when turbocharging.

And finally, before you inundate me with comments for not mentioning it, there’s the ever-popular option of adding a Nitrous Oxide System (NOS) – a topic I’ll explore more in depth in an upcoming post.

If you’ve modified your engine control computer or have what you think is the perfect solution for unlocking horsepower, let us know how you did it, and what you did it to.

Editor’s note: Harness your hidden horsepower at Advance Auto Parts. Buy online, pick up in store.

Graphic courtesy of Toycarcollector.com.

 

 

Hot Trend: ECU Tuning

Josh adjusting ECU in car

When car manufacturers install an engine into a new vehicle, they have no idea where the buyer will live or the conditions under which he or she will be driving. So, they install a “one-size-fits-all” engine and overall system that meets today’s emissions standards.

Enter Engine Control Unit (ECU) tuning.

So what exactly is engine tuning and why is it important? Good question! To find out more about ECU tuning, we contacted Josh Dankel, an ECU engineer at Cobb Tuning. Josh explains the situation further. “Let’s say that you live in the mountains,” he says. “Your OEM vehicle isn’t tuned for that type of driving. And, even if you had a car tuned for the mountains, so that you could squeeze the most power possible out of the engine, it wouldn’t be efficient when you were traveling through sea-level land. What works in 100 degree weather in Florida, as another example, wouldn’t work as well in another climate.”

The advent of the ECU

Until the 1950s, nobody gave much thought to the pollution caused by early automobiles. But some experts began to suspect that the smog in Los Angeles might be caused, at least in part, by vehicle emissions. It took nearly two decades for an official Congressional response. Finally, in 1970, Congress passed the Clean Air Act that set tailpipe emissions standards.

In response, manufacturers installed microprocessors to help control emissions. This was the advent of the “car computer.” There’s more than one car computer in a modern vehicle, but the most powerful one is typically the ECU. Like any other computer, the ECU contains settings that can be tweaked for smoother operation, better fuel efficiency, and more horsepower.

ECU tuning - computer screen

ECU tuning, with a caution

“You can definitely cause your car to run more efficiently and get better mileage by using ECU tuning software,” says Dankel. Then he qualifies, “What often happens though is that, as you squeeze more power out of your engine, you also begin to have more fun with your gas pedal. If so, then you won’t get more fuel efficiency by tuning.”

But ECU tuning combined with healthy driving habits can result in a more efficient driving, especially in relation to stop-and-go driving.

At Cobb Tuning, Josh works on a product, called ACCESSPORT, which provides up to 100 different tuning settings for different occasions.

“Let’s say that you always use 93 octane fuel at home,” he says as just one example. “If you go on a road trip and can only get 87 or 89 octane, you can switch to a different tuning to squeeze the most power out of your engine.”

Engine tuning for performance is often accompanied by additional upgrades, such as installation of a freer flowing exhaust. In turbocharged cars such as the 2006-07 Subaru WRX, Cobb recorded a 24% increase in horsepower.

Have you tried tuning your ECU? If so, what are the best ECU tuning strategies that you’ve discovered?

 

​​Tuner Notes: Why Replace an Exhaust System

Thrush brand muffler

A Thrush muffler with cutouts

For many import and tuner enthusiasts, how your car sounds can be as important as how it looks and performs. Sound and performance share a common bond—the exhaust system—and there are some pitfalls to keeping the stock exhaust system. Those car exhaust systems, consisting of a muffler and catalytic converter, sacrifice engine horsepower. You’ll also miss out on hearing an import/tuner’s true expression.

Why replacing a stock car exhaust system is a good idea

Stock mufflers are designed to absorb sound. (Learn more about the different types of mufflers.) With all their twists and turns, they get the job done of dampening the noise. That air-flow restriction, however, robs the engine of horsepower and a vehicle of its natural sound. To improve engine horsepower and harmonics—without breaking the bank—consider replacing the stock car exhaust system with a performance exhaust system (the muffler and catalytic converter).

Why replace the catalytic converter too

Second only to the muffler, a stock catalytic converter is a big engine horsepower thief—but necessary to avoid big fines and possible impoundment. So, what’s an enthusiast to do? Replace that stock cat with a high-performance one.

While a ceramic core might be cheaper, it delivers slightly less of an increase. More worrisome for import/tuners, though, is its lower melting point and the resulting failure in high performance, or boosted applications. And, when it comes to removing the cat entirely, improvement is minimal and hardly worth it, given the risks and considerable cost of running afoul of the law. If you’re looking for additional ways to improve performance without going broke, check out our article on three easy performance mods.

Considering swapping out your stock exhaust system? Share your ideas in the comments.