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Modern Use of Forced Induction - Factory Boost

More new cars today are turbocharged than ever, but is that a good thing?

Aaron Bonk
Nov 1, 2016

Over the last quarter century or so, the turbocharger's gone from fundamental ingredient to the kind of cars that keep you up at night to something about as exciting as tube socks but with the ability to satisfy low-emissions quotas. You can't buy a BMW without one (unless you're counting the electric i3 that you shouldn't), Ford's used them to make you care about its cars again (thank you, Focus ST), and even the king of all naturally aspirated commuter cars, Honda, has now got one underneath the hood of its forerunner Civic. Today, more than 20 percent of all new cars sold feature some sort of boost and, thankfully, not every one of them does so for the sake of the eco weenies.

Modern use of forced induction turbocharger Photo 2/19   |   Power adders don't get much more efficient than turbos do, which is exactly why so many new cars today are sold with them. But turbos are also good for making a whole lot of power, which is always more fun than being efficient or lowering emissions.

BOOST REVIEW

Turbocharging is, in essence, efficient. It's how Mitsubishi's managed more than 300 hp out of its mass-produced 2.0L Evo, and how almost every motorsports record you remember has been made. It's also incredibly simple. At its core, a turbo makes use of the exhaust gases the engine is already making. Here, a turbine wheel driven by those fumes links up to another wheel that compresses air within a housing before entering the engine. And we don't have to tell you that more air, along with more fuel, is what'll allow your 1.8L, four-cylinder box of pistons to act more like your uncle's 5.0L V8.

It turns out that turbos have come a long way since Chevrolet first bolted one on to the early '60s Corvair Monza you've never heard of, and today's technology means they're more reliable, quieter, and more efficient than ever.

Modern use of forced induction turbo piping Photo 3/19   |   A turbo uses its engine's exhaust gases to spin its turbine wheel, which links up to another wheel that compresses air within a separate housing before entering the engine's intake manifold.

OG TURBO PLAYERS

Factory-boosted cars have been around since before you were born but it's those that were strapped with boost in the name of more power that you remember most. Cars like that Corvair you still don't know anything about, BMW's mid-'70s 2002 tii Turbo, and anything from Saab were all designed to make more power than their naturally aspirated competition but had trouble getting enough people to want them to keep them around. The following players, however, you won't forget about anytime soon.

Porsche 930 Turbo Carrera: It's the car that, beginning in the mid-'70s, showed everybody what exactly a turbo was good for. Porsche had already been fooling around with turbos for a decade or so on the track before introducing anything to the public, but it's that 911 production car that you remember first. Early models checked in at 234 hp, although later 911s make gobs more power, all thanks to that turbo.

Modern use of forced induction porsche 930 turbo carrera Photo 4/19   |   If there was a car that started the turbo revolution, Porsche's 911 has got to be it. Porsche didn't invent turbocharging, but no other car has benefited from boost as extensively and for as long as the 911 has.

Mazda RX-7: You think they're temperamental, unreliable, and a fire waiting to happen, yet you still want one. That's because Mazda's 252hp, sequentially turbocharged 13B-REW rotary engine is every bit as amazing as it is mystical. But Mazdas and turbos didn't start in '93; the U.S. got its hands on its first turbocharged RX-7 when the second albeit slightly less glamorous model was introduced just a few years earlier.

Modern use of forced induction mazda 13b rew Photo 5/19   |   When you think of iconic, turbocharged Japanese sports cars, you can't not think of Mazda's third-generation RX-7 and its 13B-REW rotary engine.

Mitsubishi Eclipse: It's the car that, along with Honda and its Civic, paved the way for everything you care about today. The Eclipse's 4G63T engine wasn't matched with its 14B turbo because the EPA and its regulations said it had to be; it was there to get the cast-iron-block-based four-cylinder into 195hp territory, which, in the late-'80s, was about the only way to do that.

Modern use of forced induction mitsubishi 4g63t Photo 6/19   |   Mitsubishi's first-generation Eclipse started the sport compact turbo revolution and was, in part, responsible for the wave of homemade turbocharged Hondas that followed.

Toyota Supra: There's a reason the motorsports world still looks to the 2JZ-GTE: it's pretty much bulletproof. Yeah, Supras and turbos go back to the MKIII and its 7M-GTE engine, but the MKIII will never be as exciting, and that's mostly because the MKIV Supra is the fastest production car Toyota's ever let loose (withstanding the LFA, of course).

Modern use of forced induction toyota 2jzgte Photo 7/19   |   More than two decades later and the Supra's sequentially turbocharged 2JZ-GTE is yet to be beat.

Nissan 300ZX: You knew better in the mid-'90s than to mess with any Z32 300ZX with the Twin Turbo badge out back. Its VG30DETT engine made 300 hp with the help of two non-sequential, Garrett turbos and was always faster than your Prelude.

RESURGENCE

Today, factory-turbocharged cars are more popular than ever, but most of the time that turbo isn't there just so you can spank the Camaro in the other lane. A turbo is just about the most elegant way of allowing smaller, more environmentally friendly engines to produce enough power for you to do things like accelerate and merge while still giving you that small-engine fuel economy and low emissions the EPA wants you to have. At least that's what they hope. Turbos make more torque than their naturally aspirated counterparts at lower engine speeds, which means you don't need to stab the throttle as hard to get moving. Only problem is you still will, and you don't drive how the EPA thinks you will, which means that fuel economy and its earth-saving properties probably won't happen under your watch.

But none of that means the OEMs and the EPA won't stop insisting on turbo technology, and that's a good thing. Today, turbos don't just allow for lower emissions, they're more reliable, quieter, generate less heat then ever, and'll almost always give you more power than you'd get without one.

MODERN BOOST

You can sit there and dream about history's most infamous turbo cars that you can't buy anymore or you can get off your butt and go shopping for something new. Today, there are more factory-boosted cars on dealers' lots than ever, which is as good excuse as any for you to get a job, unload your automatic Sentra, and plop down the dough for something new. Wait long enough and you might not even have a choice; some analysts say that within the next decade or so a good 40 percent of all cars sold will be boosted.

Mitsubishi: The Evo X Final Edition is the last Evo you still might be able to get your mitts on, which uses a TD05H-based turbo that's got a smaller compressor wheel than its predecessor, and which means it's a bit more responsive, but still manages a best-ever 303 hp. Best of all, the Evo and its turbocharged 4B11T engine exist for you to go faster and not to satisfy anybody's low-emissions standards.

Subaru: You can't talk about the Evo without following up with the WRX. Subaru updated its high-performance Impreza a couple of years ago but, face it, it's the STI that you really care about, what with its 305hp EJ257 and IHI turbo. The STI's EJ engine isn't anything new, but Subaru developed it for the sole purpose of you being able to make more power than just about any other four-cylinder engine out there.

Modern use of forced induction subaru ej257 Photo 8/19   |   There's never been more choices when it comes to factory-boosted cars. Mitsubishi's Evo X and Subaru's WRX STI with its 305hp EJ257 were both developed for the sole purpose of you being able to make more power than just about any other four-cylinder engine out there.

Ford: The American carmaker's been cramming the idea of its EcoBoost engines down your throat for the last 10 years but it wasn't until the Focus and Fiesta STs that you stopped to listen. Ford developed its ST lineup so that you could go faster and its 252hp, BorgWarner K03-turbocharged Focus engine proves it. Here, what BorgWarner calls a low-inertia turbo speeds up spool-up time with its lightweight Titanium-aluminide exhaust wheel.

Modern use of forced induction ford focus st Photo 9/19   |   If you think Japanese carmakers have got a lockdown on factory-turbocharged performers, you're wrong. The 252 hp Focus ST and impending Focus RS would like to have a word with you about that.

Honda: The words Honda and factory turbocharged were never meant to go together, but that didn't stop the tenth-gen Civic EX from getting boosted. Before you get too excited, though, know that it's the eco warriors who won here and the 174 hp turbo mill is only a tradeoff for its 1.5L of displacement. For perspective, when emissions regulations were less stringent, the second-generation Integra GS-R made similar power (170 hp), without boost, and with only .3L of additional displacement.

Modern use of forced induction honda 10th generation civic Photo 10/19   |   Not everything that's turbocharged does so for the sake of more power. Honda's tenth-generation Civic is turbocharged, yes, but it only puts out 174 hp. Here, boost was added in an effort to match a smaller, more fuel-efficient engine underneath the Civic's hood but without losing the car's responsiveness and ability to keep up with whatever else is on the road.

BMW: These days you've got to try awfully hard to end up with anything from BMW that isn't turbocharged. Like its 230i, which is probably the only one you can afford, and is good for its 248 hp by way of what BMW calls its TwinPower Turbo system. But there aren't two turbos here; TwinPower really just refers to the split exhaust housing that separates exhaust gases in two for better spooling.

Volkswagen: Settling on something turbocharged by way of VW is easy; both the Jetta and Golf offer boosted variants, the most hopeful of which are its 2.0L mills, like the one you'll find underneath the hood of the GTI that's good for as much as 220 hp and, according to VW, puffs out 18 percent better fuel economy than the older model yet still makes more power than ever.

Acura: You're not buying Acura's second-generation NSX but that doesn't mean you shouldn't know about the turbocharged mill that makes it tick. The NSX's V6 gets its 500 hp from a twin-turbo layout that allows each of its single-scroll, electronically controlled turbos to hit just north of 15 psi. The power doesn't stop there, though. A trio of electric motors (one for the rear and two up front) yield another 73 hp but only when things like traction, emissions, and your right foot say you need it.

Modern use of forced induction 2nd generation acura nsx Photo 11/19   |   Where Honda fell short with its Civic it redeemed itself with its NSX. Here, a trio of electric motors work in tandem with the twin-turbocharged V6 that, by itself, puts out 500 hp.

Nissan: You're also probably not in the market for an R35 GT-R but that shouldn't stop you from knowing how it gets its boost. Here, two IHI turbos are mounted in parallel, which means they both come online at the same time unlike what you'd find with a sequential setup. Curious just how efficient a turbo engine can be? Nissan's 500-plus-hp VQ38DETT still meets the U.S.' strict 50-state LEV2/ULEV guidelines.

Modern use of forced induction nissan vq38dett Photo 12/19   |   Nissan's R35 GT-R's VQ38DETT defines efficiency. It's good for more than 500 hp yet still meets the U.S.' strict 50-state LEV2/ULEV standards.

BOOST VS. AU NATURAL

Dollar for dollar, a turbocharged engine will always make more sense than anything naturally aspirated. But they aren't perfect and they won't make life on your engine's internals any easier. Here are the top reasons boost might be best for you. Or not.

Boost it

  • There's no other way to get this sort of power.
  • Do you want your 1.6L Honda to beat Mustangs or not?
  • Picking up an extra 20 hp at a time was never easier. Boost controller, yo!
  • Dollar per horsepower, nothing compares to turbocharging.
  • Turbocharging's one of the most efficient ways of making more power.

Or don't

  • More power means your pistons, rods, and cylinder walls can all bust.
  • Boost creates heat, and heat breaks things.
  • Custom turbo kits can require lots of parts and can be complex.
  • You'll need all sorts of supporting mods that you can't afford.
  • All of a sudden, traction's a problem.
  • Make the sort of power you care about and forget about passing smog.
  • Going fast isn't cheap.

TURBO TERMINOLOGY

Sequential Turbos: Sequentially turbocharged engines date back to the RX-7 and Supra and, although they aren't all that popular anymore, can still be found underneath the hood of diesels like Nissan's Titan XD, for one. Here, a smaller turbo spools up first, delivering low-end response followed by a second—often larger—turbo that gives you the top-end power that makes you feel important. Sequential setups are typically limited in terms of generating big power and are often bulky, complex, and less efficient than a single-turbo setup.

Modern use of forced induction multiple turbo layout Photo 13/19   |   There's more than one way multiple turbos can be laid out: sequentially, where a smaller turbo spools up first, followed by a second, larger one, and parallel, where two equally sized turbos both come online at the same time.

Twin Turbos: Stick two equally sized turbos onto your engine—each fed by half its cylinders—and you've got yourself a twin-turbo or parallel-turbo layout much like the 300ZX had. Here, both turbos have got to be the same size and are typically smaller than what you'd find on any other kind of turbo engine. The twin-turbo layout is still a popular one and can be found matched to V-type engines like the GT-R's VQ38DETT.

Variable-Geometry Turbos: The future of turbocharging starts with turbos like these that feature movable vanes that are able to simulate various turbine housing dimensions, which can result in better turbo response. Look for this technology on the same car that brought you mass-produced turbocharged performance in the first place, the 911 Turbo.

Modern use of forced induction twin scroll turbo Photo 14/19   |   Twin-scroll turbos incorporate turbine housings that are split into two separate passages that speed up the engine's exhaust pulses as they pass through, which means better response and less lag.

Twin Scroll: If you're familiar with any of these already, it's got to be the twin-scroll turbo, which means the turbine housing is split into two separate passages. Do it right and the engine's exhaust pulses are now more effective, speeding up that turbine, which means less lag.

BUYING BOOST

That aftermarket turbo kit on your 240 will probably never be as reliable as whatever, say, Subaru bolted onto its WRX. Most of the time, whatever engine you're sticking that turbo onto wasn't designed to handle the sort of cylinder pressure it's about to experience. Right about now is the time when rods bend, valves burn, and headgaskets blow. It doesn't have to be that way, though, so long as you take the right precautions and don't skip any of the supplemental mods you know you need but don't want to pay for, your aftermarket turbo kit can be just as reliable as factory boost. Do the following things and avoid blowing your shit up right away:

Modern use of forced induction intercooler Photo 15/19   |   Factory boost may not yield the most power, but it's efficient, tidy, and exponentially simpler than aftermarket turbo systems where things like massive intercoolers have got to be positioned, piping's got to be fabricated, and fuel systems have got to be updated.

The turbo: You know you need a turbo but you've got no idea where to start. It'd take an entire article to explain turbo sizing so, instead, just know these two things: First, you won't make any more friends by strapping on something that's way too big for your engine. Second, flow maps can provide you with all sorts of useful information; use them and don't end up with a turbo that's too big or too small.

  • Garrett GTW: You can't go turbo shopping without at least considering something from Garrett, and its GTW turbos might be exactly what you need: something capable of making big power but that you can afford. GTW turbos feature forged-aluminum compressor wheels, journal or ball-bearing cartridges, and T3 or T4 turbine housings. They're also good for 700-950 hp.
  • BorgWarner EFR: BorgWarner's EFR (Engineered for Racing) turbos, like the EFR-7163—the official turbo of IndyCar—are now available to schmoes like you and me, are good for as much as 1,000 hp, and feature ceramic, dual-ball-bearing cartridges, stainless-steel turbine housings for less heat and longer life, and integrated blow-off valves and wastegates.

The intercooler: That air that your new turbo's compressing before sending it toward your throttle body's getting really hot. Cool it down and avoid the ugliness of blowing things up with an air-to-air intercooler, preferably placed in front of the radiator where it'll be able to work more effectively.

Modern use of forced induction greddy air to air intercooler Photo 16/19   |   You can't have a thorough and reliable turbo system without some sort of intercooler, and nothing's more practical or efficient as the air-to-air type that works similar to a radiator, only here, instead of coolant passing through, the engine's intake stream does.

  • GReddy: Get the right intercooler and you've just made your engine safer and more powerful at the same time. That's because the right intercooler, like something from GReddy, has the ability to lower engine inlet temperatures, which creates a denser air charge that'll make more power at the same boost level.
  • Godspeed: That '84 Camry you think you're going to turbocharge means finding a bolt-on intercooler isn't gonna happen. Godspeed's line of universal intercoolers means even the guy with the '84 Camry can take advantage of lowering intake temps, reducing detonation, and not blowing up.

The other stuff: You'll also need a blow-off valve to keep your turbo's compressor wheel from surging and wearing out and an external wastegate if your turbo wasn't equipped with an internal one to regulate boost pressure.

Modern use of forced induction borgwarner efr blow off valve Photo 17/19   |   Modern turbos like BorgWarner's EFR units incorporate their own blow-off valves and wastegates, but if you don't have something like an EFR, you'll need an external blow-off valve to relieve pressure from the intake system when letting off the throttle.

  • HKS: It's the blow-off valve that diverts boost pressure out of the system once the throttle's been closed. Without one, extreme pressure changes can lead to turbo damage. HKS has been making blow-off valves since before you were born and has got an application for whatever it is you plan on boosting.
  • Turbosmart: It's the wastegate that regulates boost pressure, and nothing's more capable than a high-flow external one. Turbosmart's ProGate 50 Lite is among the smallest external wastegates, which makes integrating it into any setup easy.

The internals: Most of the time, turbochargers and high-compression engines don't get along. Lower your compression ratio a smidge with a slightly thicker headgasket. Or do it the right way and adjust your compression ratio with the right pistons. Make sure you're using something that's been forged and, since you've got the whole thing open, drop in some stronger connecting rods while you're at it.

Modern use of forced induction forged pistons and rods Photo 18/19   |   Boost doesn't blow up engines, but the higher cylinder pressures associated with it does. Forged pistons and rods are almost always necessary when turbocharging anything that didn't come that way from the factory.

  • BC: BC's got the forged pistons and rods you need to keep from blowing up under boost and the cams and valvetrain you want to make even more power. Be sure to consider what octane you've got access to before settling on a particular compression ratio.

More fuel: We're not talking about topping off your tank here, noob. Your engine's ability to burn more fuel is what'll make more power and keep you from expensive problems. Most of the time you'll need a higher-flowing fuel pump and fuel injectors to make that happen.

  • AEM: You already know you need higher-flowing fuel injectors and, most likely, a higher-flowing fuel pump to satisfy that big 'ol turbo, but what you forgot about was the engine management system to control it all. Chances are, AEM's got an Infinity ECU that'll plug right into whatever it is that you drive, allowing you to control those new injectors and a whole lot more.

The stuff you can't see: Bolt everything up right and all of a sudden you're making a whole lot more torque. More torque means slipped clutch discs, broken halfshafts, and cracked engine mounts, though, so be sure to shore up what you need to before going too far.

  • SPEC: Add enough torque and you'll be obliterating that stock clutch in a hurry. Which means you'll want to look to SPEC, who's got everything from baller, twin-disc setups to high-performance street versions in their extensive lineup.

Modern use of forced induction spec clutches Photo 19/19   |   Boost doesn't destroy clutches either, but the additional torque you've just made will wear a factory clutch disc to its core in a hurry. Aftermarket units like these from SPEC can provide extreme grip yet still maintain street drivability.

TAMING THE TURBO

Looking to turn up the boost on your factory turbo mill and keep its air/fuel ratio happy? There's software for that. Not happy with that wussy factory rev-limit? That and a whole lot more can also be changed. But you already knew that. As it turns out, just about anything can be fiddled with. We're talking about reflashed ECUs, which, a lot of times, are about the only thing keeping you from going as slow as what the guys who built your car thought you should. For the guy searching for a moderate power bump on the same car that he schleps back and forth to work in, a reflashed ECU makes a whole lot of sense. Developers like Hondata, for example, offer software upgrades for that tenth-generation Civic, delivering it from that measly 174 hp to something just over that 200hp mark. Best of all, most reflashes are inexpensive, will still let you pass an emissions test, and won't require you to do a whole lot more than unplug your ECU and hand it over to somebody smarter than you so they can work their magic on it.

By Aaron Bonk
348 Articles

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