In recent years, turbocharging has become the go-to strategy for big power among both enthusiasts and OEMs. While other power adders like supercharging and nitrous have their virtues and can be better suited to certain applications, turbos offer a number of advantages that benefit performance as well as efficiency.

“For automakers, much of the recent rise in turbocharging’s popularity has to do with fuel economy,” Darcy Gibbs, mechanical engineering manager at Holley Performance, explains. “Turbocharging gives you the ability to substantially increase the maximum amount of power that an engine can output without significantly increasing fuel consumption.”

As stricter government regulations continue to roll out, this has become a key item of concern for manufacturers who’re looking to produce ever-more-powerful models without running afoul of the efficiency targets that they need to hit.

“In most driving scenarios, the turbocharger is effectively dormant and not producing boost, which allows the engine to operate as efficiently as possible when you’re just cruising around, or at a steady-state engine speed on the highway. And then when you ask for the power, the turbo ‘wakes up,’ and there it is.”

Gibbs also cites improvements in OE engine management technology and the benefits of the economies of scale as other factors that have made turbocharging so commonplace in today’s factory engine combinations. And while enthusiasts and racers tend to have different priorities than automakers when it comes to engine performance, turbocharging’s popularity on the aftermarket side has been enabled, in part, by similar advances.

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“If you look at the setups you would’ve seen at the drag strip, say, 20 years ago, it was really about engine displacement. But I think that when we started seeing these guys with turbocharged 2.0-liter K-series engines doing seven second quarter miles in Hondas, people took notice. And improvements in aftermarket engine management technology helped popularize turbos on this side of the equation as well.”

But while the basic principles of naturally aspirated, supercharged, and nitrous-fed setups are fairly easy to understand, turbo systems are a bit more esoteric. Jeremy Clarkson famously once described the turbocharging process this way: “Exhaust gases go into the turbocharger and spin it, witchcraft happens, and you go faster.”

There’s perhaps no better summation of how most of us think about the complexities involved in turbocharging. But knowledge is power, as they say, and that certainly applies to turbo system modifications. To give us a clearer picture of how a turbo system works, Gibbs provides a straightforward synopsis and explains why a charge pipe upgrade should be on your radar, regardless of whether you’re a casual enthusiast or a seasoned racer.

The Role Of Charge Pipes

“As Jeremy noted, the exhaust gases go into the system and they spin the turbine side of the turbo, and that spins the compressor side of the unit, which is connected to the engine’s air intake system,” says Gibbs. “The compressor wheel compresses the air that’s coming into the intake. Since exhaust gases are hot and the air compression process introduces additional heat, you’ll typically see some kind of charge air cooling system involved here – either an air-to-air or air-to-water intercooler. And once the air has gone through this intercooler, it enters the throttle body.”

The charge pipes are the components which take the air from the turbocharger to the ‘hot’ side of intercooler, and then once the heat exchange has been made, charge pipes on the ‘cold’ side of the intercooler deliver the cooled air to the throttle body.

“The charge pipe is connected to the outlet of the volute on the compressor side of the turbocharger, and they’re typically either clamped directly together, or attached via a silicon or rubber hose. And that basically routes the air to wherever it makes sense to connect to the intercooler,” he says. “The turbocharger is typically behind the radiator system, and to get cool air in an air-to-air heat exchanger configuration, you need that heat exchanger to be out in of the radiator stack to get that nice, cool air. So you’ve got to route that charge air around that radiator stack and over to the intercooler’s location. Once it’s done the work of exchanging the heat, the ‘return’ charge pipe, on the cold side, has to then route the air to the throttle body.”

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Common Misconceptions

Gibbs tells us that one of the most popular myths about charge pipes is that upgrading to larger diameter components will inherently increase power and efficiency. Although there are some situations where larger diameter charge pipes can provide an improvement over smaller ones, it’s important to keep in mind that charges pipes which are oversized for the application can actually work against your performance goals.

“You have to remember that this is a pressurized system, and you’re constantly trying to combat pressure drop when you’re moving the charge air from the turbocharger to the throttle body. With today’s factory setups we see a lot of sharp turns, molded-in cutouts, and other solutions that are designed to make it easier to route the charge pipes around components in the engine bay. All of those things introduce turbulence into the system, which in turn increases pressure drop. Each one individually might only make a small difference, but together they really start to add up.

“Some folks think that if you want an effective charge pipe, you need to make it bigger than the stock OE part. That can be true in some instances, but it’s ultimately a balance. If you use a charge pipe with a diameter that’s too big, you will actually get a larger pressure drop from the charge pipes. It can increase turbo lag as well.”

On the other side of the coin, Gibbs says that there’s a significant contingent of folks who think that those tight bends and other restrictive elements of some charge pipe designs don’t really affect performance and efficiency because it’s a pressurized system. But that isn’t entirely true either.

“Although there’s an element of truth here as well, it isn’t universal to all applications. You might not have an issue with a bone-stock setup, but when you start getting into higher boost, upgraded turbochargers, and things like that, it starts to make more of a difference.”

Each one of those restrictions means that the turbocharger has to work that much harder in order to provide consistent boost levels. That additional work translates to more heat, which in turn results in less power. “You’re burdening the intercooler system with this additional heat. And at a certain point, the factory engine management system will step in to modify the maps and turn things down if it detects higher intake air temperatures. That’s done to protect the engine and turbocharger.”

The Right Way To Upgrade

Whether your turbocharged engine setup is highly modified or factory-stock, there are some clear advantages to stepping up to high-quality aftermarket charge pipes like the ones offered by APR. Beyond alleviating restriction concerns, these charge pipes have also been developed to address issues that are pervasive in many OE designs.

“Factory charge pipes are usually made out of plastic, mainly due to cost considerations, and that presents a few potential concerns,” says Gibbs. “For example, to combat the clamping force of the hose clamps that are attached to them, manufacturers will mold in, or over-mold the plastic over a metal ring. That metal ring sits inside the charge pipe, where the hose clamp would go, in order to prevent the clamp from crushing the charge pipe. In the case of the new MBQ Evo-platform cars like the Mk8 Volkswagen Golf and GTI, they actually eliminated one of those metal rings, and they have what looks like a ‘flow straightener’ in the end of the charge pipe on the cold side, right in front of the throttle body. Looking at it straight on, it looks like a little plastic star, and it’s supporting that portion of the charge pipe against the clamp force. What we’ve discovered when removing them from customer cars is that most of them are broken, straight from the factory.”

Having a broken piece of plastic right in front of where the air goes into your engine is sub-optimal, as you can imagine. But beyond that design flaw, the OE charge pipe material itself can become a liability if you’re really putting your car through its paces on a road course or at the drag strip.

“At a certain point, plastic charge pipes will actually begin to melt – they’re just not designed to see that amount of heat for that amount of time,” he points out. “And so upgrading to an aluminum charge pipe is a huge advantage there. Also, the bead-rolled ends on the APR charge pipes can handle a lot more clamping force than those plastic components, which can come in handy if you’ve got an upgraded turbo that’s running more boost than stock.”

APR’s aluminum charge pipes also address air flow turbulence by using mandrel bends for smoother airflow paths and employ consistent piping diameters whenever possible. “And by reducing that turbulence, we’re helping the system maintain pressure, which translates to better performance,” Gibbs notes. Although these APR charge pipes are a worthwhile investment regardless of how mild or wild your build is, he says that there are a few tell-tale signs that you’re already overdue for an upgrade.

“If you’re experiencing boost leaks, or if one of the boost hoses actually pops off, that’s a pretty clear indicator that the factory charge pipes aren’t cutting it. Leaks aren’t always obvious at glance, though. If you notice that the boost levels are oscillating above and below the target level, that’s a good indicator that there’s a leak somewhere in the system. What’s happening there is that the engine is chasing a boost target. One moment it might be adding boost to fight against the leak, then the leak momentarily seals up. Now you suddenly have this spike in boost, and the engine has to adjust for that, too. That those fluctuations typically point to a leak in the system. Sometimes boost leaks will cause audible whistles or ‘whooshes,’ too.”

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Gibbs also points out that if you’re doing an intercooler upgrade, you may want to consider replacing the factory charge pipes at that time, since you’ll be removing the charge pipes during the intercooler installation process anyway. “A charge pipe upgrade should be considered in any situation where you’re modifying your vehicle for performance, but even a totally stock vehicle can see a benefit,” he adds. “We know from instrumented testing and development experience that these charge pipe issues are prevalent. That’s why we always encourage our customers to upgrade them.”