TwinScrewTech

When the sixth-generation Camaro SS debuted late last year, it elevated Chevrolet’s musclecar to new heights. Gone was the old Holden-based chassis, replaced by the smaller, more modern Alpha platform it now shares with the Cadillac ATS.

Along with a weight reduction of several hundred pounds, the new generation SS was also the first Camaro to receive the venerable LT1 V8 motor. This direct-injected, 455 horsepower 6.2-liter mill made its debut in the C7 Corvette Stingray two years prior, and in the engine bay of this new Camaro, it delivered levels of performance never before seen in factory SS specification.

Although Chevrolet has their own supercharged Camaro due out next year with the ZL1, mixed reviews about the LT4's power output and heat management in the Corvette Z06 have provided some cause for concern. GM moved to a smaller, 1.7-liter supercharger with the LT4 versus the 2.3-liter unit used in models like the C6 Corvette ZR1. In order to provide similar levels of boost, the smaller supercharger has to spin faster, in turn creating more heat.

Despite its newfound capability, for some it’s still just not enough – not when there’s boosted Mustangs and Challengers afoot. Chevy’s own supercharged LT4 serves as something of a response to the factory-produced brutes like the Shelby GT500 and the Hellcat twins. It first debuted in 2015 between the fenders of the Corvette Z06, and the Camaro ZL1 was the next to follow in its footsteps.

As brutal as that 650 horsepower engine is, the price of admission to get one can be enough to keep some folks away, and heat management issues with the LT4 in the Corvette chassis have persisted ever since the Z06 made its way into the hands of journalists at Road Atlanta late in 2014.

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Whipple’s new system is compact enough to fit into the Camaro’s engine bay without any cutting or additional modification while also delivering more power than an LT4 on an otherwise stock LT1. The system’s twin screw design offers advantages in both performance and thermal efficiency over Roots type alternatives.

For those who are wary of the LT4’s design or aren’t interested in what the ZL1 package brings to the table, Whipple is offering an alternative, and this single upgrade can take the garden-variety LT1 in the Camaro SS to output levels beyond that of the LT4. Here we’ll get the lowdown on Whipple’s 2016-17 Camaro SS supercharger system in terms of their design philosophy, how it differs from the factory approach, and what kind of gains owners can expect to see from this upgrade.

Forced Induction Designs

Not all superchargers are created equal, and supercharging isn’t the only way to add forced induction into the equation. An internal combustion engine is in essence an elaborate air pump, and the idea behind forced induction is to push more air through the system with each combustion event. In theory, more air combined with more fuel should equal more horsepower.

Auto manufactures have turned to turbocharging smaller displacement motors in recent years, as AMG did when switching from the naturally aspirated 6.3-liter V8 to the bi-turbocharged 4.0-liter mill. Image: Mercedes-AMG

Auto manufactures have turned to turbocharging smaller displacement motors in recent years, as AMG did when switching from the naturally aspirated 6.3-liter V8 to the bi-turbocharged 4.0-liter mill. There’s a pair of turbochargers buried in there somewhere, trust us. Image: Mercedes-AMG

Turbocharging has long been an alternative to large, naturally aspirated motors, and in recent years many automakers have turned to this method to add performance while minimizing the impact on fuel economy to get it. Turbocharging, like supercharging, forces more air into the combustion chamber, in turn causing a bigger bang. But unlike superchargers, turbos aren’t belt driven. Instead their turbines are motivated by the engine’s exhaust gas. While this has a benefit of improved efficiency versus supercharging during low RPM cruising, it means that the engine’s power delivery isn’t linear since the turbochargers only spool up and make power once that engine hits a certain range in the powerband.

Superchargers, on the other hand, are belt driven and therefore create boost whenever the engine is operating. While this isn’t as frugal on fuel, it means the engine’s power delivery is more linear throughout the rev range, in turn behaving more like a naturally aspirated motor would.

In the realm of modern superchargers, there are three main design approaches: Roots type, centrifugal, and twin screw. Each has its advantages and drawbacks, and both tuners and automakers utilize all three designs in different applications.

Due to its simplicity and compact packaging, GM decided to go with a Roots type Eaton TVS blower for the LT4.

Due in part to its simplicity and compact packaging, GM decided to go with a Roots type 1.7-liter Eaton TVS blower for the LT4. When designing production cars, automakers are faced with federal regulations that put limitations on design options. These boundaries are less restrictive when it comes to aftermarket options.

The Roots of Supercharging 

Roots type superchargers have a history dating back to the late 1800s, when the Roots brothers designed a system to serve as an air conveyer for mine shafts. More recently, roots type superchargers have taken the forms that you’ve likely seen popping out of the hoods of drag race cars with bird catcher-style hood scoops. While their simple design has made them a popular choice over the years, they typically lack the efficiency of newer alternatives.

If this Vortech YSi centrifugal  supercharger looks a lot like a turbo to you, that's because they both use the same basic design.

If this Vortech YSi centrifugal supercharger looks a lot like a turbo to you, that’s because they both use the same basic design concept. While turbos use exhaust gas to spool up the compressor, a centrifugal supercharger like this one is belt driven.

Centrifugal Motion

By contrast, centrifugal superchargers function more like a belt-driven turbocharger, utilizing a compressor wheel (much like a turbocharger’s) to force air into engine. But rather than using exhaust gases to spool the compressor, it’s done by an engine accessory belt. While centrifugal superchargers certainly have a use case in modern applications, particularly where engine bay packaging is tight overhead, they typically take longer to ramp up to their full boost levels as opposed to a twin screw or roots style supercharger, which produce large levels of boost almost immediately.

Whipple supplies the 2.9-liter twin screw supercharger used on Chevrolet's COPO Camaro drag car.

Derived from Roots type superchargers, twin screw superchargers improve upon the design by compressing the air before it goes into the motor, rather than simply pumping more of it in as Roots type superchargers do. The design yields significant improvements in overall efficiency too, resulting in less heat, consistent performance throughout the rev range and tons of low-end power, the latter of which is particularly desirable in street driven vehicles.

For those reasons, twin screw style superchargers have become the go-to design for OEM high performance applications, most recently with Chevrolet’s sixth-gen COPO Camaro and Dodge’s supercharged 6.2-liter Hellcat V8.

For those same reasons, companies like Whipple utilize a similar twin screw design for their aftermarket products as well. And as we’ll explain below, Whipple’s twin screw supercharger design differs from GM’s roots-style approach with the LT4 in some important ways.

Development and Design

When a company develops a supercharger for a new vehicle, there’s a multitude of factors that must be considered beyond sheer output. “We basically start with a car, an engine and the CAD data of the vehicle,” says Dustin Whipple of Whipple Superchargers.

Getting the maximum amount of air into the engine is only one part of the supercharging formula - it also has to fit into the vehicle in question with minimal additional modification (or, preferably, none at all), and it also has to have enough thermal efficiency to avoid succumbing to heat soak over a reasonable period of time. Whipple's design is robust enough that additional headroom has been built in for further performance modifications down the line.

“From there we begin with a design review, understanding what can fit and what can’t, so we can start development. Once we’ve come to an understanding of what will be best for that application, we begin all the work in CAD. From there, the basic design gets done to maximize all areas.

“We use CFD software to help with inlet design and airflow, then we work with our intercooler vendors to come up with the optimum intercooler size and type as we modify both the air and water side of the core depending on the application. From there, we then 3D print sample parts to mock up in the vehicle and on the engine, ensuring fitment, clearance, ease of installation, etc. Once we’ve done this, made changes, we go to castings and prototype testing.”

Superchargers tend to generate a lot of heat, and heat is the enemy of performance when it comes to supercharging. While getting a lot of air into the motor is important, making sure the system can maintain consistent output through proper heat management is just as pivotal, otherwise power tends to drop off precipitously as heat soak sets in.

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Unlike some other supercharger systems on the market, Whipple’s twin screw system remains 50-state emissions legal.

“Compared to the Eaton, we have far more capacity – 2.9L is 26 percent more capacity than a 2.3L, and more than 50 percent greater capacity than a 1.7L. This lowers the compressor speed over 2000 RPM, allowing you to get more optimal power, as well as having more capacity in the future. – Dustin Whipple, Whipple Superchargers

“What separates us from most is that not only do we go the extra mile to maximize airflow on both the inlet and out of the compressor, we also use larger, more efficient intercooler cores that truly maximize cooling. We design them with the mindset that the base power level is only the first stage, meaning we build significant extra capacity for power, airflow, and thermal efficiency. Many miss this and only maximize for base power, leaving it less efficient or ideal for later modifications.”

For the 2016-17 Camaro SS, the result is a 2.9 liter twin screw supercharger system that simply outperforms the established alternatives. “Compared to a centrifugal, this system offers instant boost for increased drivability, more tip in torque, and a much cleaner installation,” Whipple says. “Most centrifugal systems require cutting to get the air tubes to the front of the vehicle, as well as having the air filters above the headers.”

And compared to GM’s Roots type Eaton TVS supercharger used on the LT4, Whipple’s system doesn’t have to spin nearly as fast to make similar levels of boost, in turn reducing the internal temperatures that GM has struggled with during prolonged road course use with the C7 Corvette Z06.

“Compared to the Eaton, we have far more capacity – 2.9L is 26 percent more capacity than the 2.3 liter, and more than 50 percent greater capacity than a 1.7 liter,” Whipple points out.

“This lowers the compressor speed over 2000 rpm, allowing you to get more optimal power, as well as having more capacity in the future. The twin screw is a true compressor, giving it less leakage in boost applications, lowering power consumption and discharge temp. Therefore the Whipple supercharger stays cooler, longer with less heat soak.”

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Gains Over Stock

OK, so we’ve got a handle on Whipple’s design – but the results are what ultimately matters, right? All the engineering in the world isn’t worth much if it doesn’t translate out on the road. Well, we’ve got some promising numbers for Camaro SS owners looking to boost their LT1.

“On 91 octane fuel, an LT1 using our supercharger system will make 600 rear-wheel horsepower – a gain of over 200 rwhp over stock,” Whipple tells us. “Even better – it makes 630 pound-feet of torque at the wheels as well. That’s neck-snapping torque!”

Whipple also offers additional supercharger pulleys in various sizes for the 2016-17 Camaro SS kit here. A general rule of thumb is every .125″ of pulley change is one PSI of boost.

Using 15 percent as a baseline for parasitic loss from crankshaft to the rear wheels, those are gains of nearly 50 horsepower and almost 80 pound-feet of torque over GM’s own LT4 motor on an otherwise stock LT1. And with room to grow built into Whipple’s system, it’s ready to go well beyond that already impressive figure whenever you are.

Get more information about Whipple’s killer supercharger system for the 2016-17 Camaro SS right here.