The Turbo Craze: All Aboard For Boost

Words And Photos: Richard Holdener

It seems turbochargers are everywhere. From Formula One and IndyCar to Drag Week and Holley’s LS Fest, pop the hood on any of the fastest vehicles in attendance and the chances are very good that said motor benefits in some way from positive pressure. While we have come to expect turbocharging at the strip, that amazing power potential has also found its way onto the street, where Crow and Corolla alike all benefit from boost. Heck, even the OEMs have embraced turbocharging to provide the required combination of power, emissions and fuel mileage required for today’s performance-minded enthusiast. Ford, Chevy and Dodge all offer turbo motors and not just in their diesel line ups, as direct injection has been combined with boost to create powerful, small-displacement, EcoBoost, Ecotec and MuliAir gas engines. Why the sudden popularity and (more importantly), why should you board that crazy train to turbo town? Read on, my friend as we take an in-depth look at the proliferation of turbocharging.

Turbocharging is awesome and the power potential is amazing, but the recent surge in popularity is a function of more than just power. A number of factors have combined with the afore-mentioned power potential to create the current boost craze, including cost, technology and even social media. Before we get to these, we need to examine the tremendous power potential offered by turbocharging, as no amount of technology, affordability nor the power of social media can create desire without proper substance (the Kardashians notwithstanding).

In this case, the substance offered by turbocharging is the ability to dramatically increase the power output of any combination. All-motor aficionados claim that anyone can make power with turbos, but the turbo guys recognize that all-motor fans are just guys that have never run boost. It is hard to argue with the fact that turbos allow you to have all the power of your all-motor combo then increase it by 50%, 100% or even 150% (or more). Time was when people got excited about making 1 horsepower per cubic inch on an all-motor combo, but now hot street/strip motors can eclipse 2 hp per inch and dedicated race motors are up near 3 hp per inch. Impressive as those numbers might be, they pale in comparison to the 8, 9 and even 10 hp per inch offered by turbo combinations.

How do turbos offer so much power? The reality is that boost in general, and turbochargers specifically, act as a power multiplier. If we apply boost from a turbo to a typical 300 hp V8, we must first understand that the normally aspirated motor is already running under boost, boost we call atmospheric pressure (of 14.7 psi at sea level and a given temperature). The atmospheric pressure obviously changes (as does the power output) with changes in elevation, temperature, and humidity, but know that when the piston races down with the intake valve open, it’s positive atmospheric pressure that forces air into the negative pressure created by the downward moving piston. Thus, our theoretical (normally aspirated) V8 making 300 hp does so at an atmospheric pressure of 14.7 psi. The upside of understanding this is that if the motor makes 300 hp at atmospheric pressure of 14.7 psi, if we double that pressure by adding 14.7 psi of boost from our turbo(s), we can theoretically double the power output (double the pressure=double the power output). There are a number of reasons why this doesn’t always work as easy as the math suggests, but just know that such gains are not only possible, they are expected.

Understanding that doubling the boost can double the power of our 300 hp V8 to 600 hp, we can also extrapolate lower and higher boost levels, as well as what happens when we change the power output of the original test motor. If we apply just 7.35 psi (.5 bar or 50% atmospheric pressure), we get a corresponding 50% increase in power from 300 hp to 450 hp. The same goes for running 2 bar (14.7×2=29.4 psi), where we transform our 300 hp V8 into a 900 hp monster. The calculation works for any boost level, but it also works if we apply it to a more powerful combination. Suppose we improve the power output of the 300 hp V8 to 400 hp by upgrading the heads, cam and intake. Running 7.35 psi will increase the output of the 400-hp V8 by 50% to 600 hp while 14.7 psi will (again) double the power to 800 hp. Running 29.4 psi will result in 1,200 hp, and so goes the calculations based on the new power output at any given boost level. This example should illustrate the importance of combining a powerful normally aspirated combination with boost, as the power gains are simply multiplied by the original output-the more you start with the more you finish with. Having more power to start with also allows you to reach any given power level at a lower boost level.

While the boosted power output is a function of the original power multiplied by the boost (actually pressure ratio), know that all boost is not created equal. The advantage turbos have over superchargers is that very little power is required to drive the compressor of the turbo. The impeller or rotors of a supercharger are driven directly off the crankshaft. This mechanical coupling can provide immediate boost response, especially with positive displacement superchargers, but, like the power steering, A/C and alternator, the parasitic losses associated with driving the supercharger reduce the power output offered by the motor. What this means is that for nearly any given boost level, the turbo will produce more power than a comparable supercharger. This power differential will increase with boost (and flow), but know that 10 psi from a supercharger will not produce the same power curve or output as 10 psi from a turbo. The sacrifice for this efficiency can be boost response, but proper sizing can produce amazing results as factory turbo motors are able to provide peak boost pressure as low as 1,800 rpm (lower than you would want for almost any performance application).

Turbos have offered this type of performance since their inception, but one of the major reasons for their sudden surge in popularity is availability. Like it or not, the advent of affordable, offshore products has helped usher in the current turbo era. Before the China connection, turbo kits were few and far between primarily because of their expense. Complexity also played a part, but we will cover that portion in our discussion on social media. The average Joe could not or would not spend $5,000-$6,000 on a turbo kit, but thanks to knock-off turbos, intercoolers and the associated couplers and tubing, turbo pricing has dropped dramatically. Obviously it pays to shop wisely, but putting together your own turbo kit can be done for less than half of what is cost not long ago and even less if you shop around. With $300-$400 turbos, $125 intercoolers and aluminum tubing bends readily available, it is possible to piece together a DIY turbo system for under $1,000 if you start with factory exhaust manifolds. This type of kit is not going to put a scare in the likes of Larry Larson, but it is capable of boosting the power or your Ford, Chevy or Dodge (or import) by 50%-100% or more.

In addition to cost, technology has played a part in increasing the number of boosted builds. We mentioned that the boost supplied by turbo motors was a multiplier of the original (normally aspirated) output and technology has helped dramatically improve that output. Using the small block Chevy as an example (though Ford and Dodge motors followed suit), we see that after the original muscle-car era, power outputs plummeted to keep pace with the ever tightening emissions laws. We saw a resurgence in performance heading into the mid 80s, but the last L98 TPI small block motor managed just 245-250 horsepower. Technology upped the ante when GM introduced the 300-hp LT1 then again after the LT1 was phased out in favor of the LS engine family. Starting your turbo build with a 250-hp L98 will naturally result in substantially less power than a 300-hp LT1 or (better yet) a 430-hp LS3. The LS engine family has been around long enough that they are dirt cheap from your local boneyard. Best of all, making as much as 1,000 hp takes nothing more than adding a cam, springs and the right turbo to an otherwise stock and inexpensive 5.3L LM7 (LS motor). It wasn’t long ago that making an honest 1,000 hp required a dedicated (and expensive) build up. It’s so common place, that 1,000 hp is now the new 500 hp!

Why are quality exhaust components critical for your turbo motor?

Though all of these factor are inexplicably linked, social media has also played a major role in bringing turbo power to the forefront. The power of social media is not to be denied and how can you resist those glowing exhaust manifold photos or videos. Add to that the exploits of the 400+ mph Bonneville racers, 2000+ hp Drag Week (and Street Outlaw) competitors and all those helpful, how-to horsepower videos and you start to see how turbos have managed to stay relevant. Despite the onslaught of online interruptions from the Nene, Pizza Rat and what lunacy Kim and company might be involved in this week, enthusiasts rush to share their own twin-turbo install videos, dyno, or drag race results. The sheer availability of information eliminated one of the obstacles involved with past turbo installations, as no matter what you plan to install, it has likely already been done and the videos are there on line to help guide you successfully through your install. Things like engine combinations, camshaft selection and even turbo sizing are all readily available (though mind the source of info). Cost, technology, and even social media have all combined with the prodigious power potential to keep that turbo train rolling down the track. The only question now is, what are you waiting for? Grab a turbo and get on board!