One Blown Bat Outa Hell

The Tom Henry Racing Camaro's Supercharger System
by Hib Halverson, Content Director

Superchargers are the weapons of choice for fifth-generation Camaro owners looking for big power increases. With the car's real-world weight hovering around 4100-lbs, hardcore owners of Chevrolet's iconic sports coupe are looking for 150-or-so more horses needed to show their tail lights to Corvettes. Consequently, in the short period since Camaro returned to the marketplace, the aftermarket has responded with bunches of blowers.

Even Chevrolet is posed to jump on the boost band wagon with a 5G Z28 which will use GM's LSA, a 6.2-liter, supercharged V8, and that begs the question: why bother with an aftermarket blower when GM will have its own?

Camaro upfitter, Tom Henry Racing, sees The Edelbrock E-Force Supercharger is as the best solution to a Camaro buyer's need for boost–better than other aftermarket systems and, perhaps, better than GM's factory blower. Consequently, the supercharger THR makes available on its uniquely personalized Tom Henry Racing Camaros is E-Force.

The LSA is rated at 556-horsepower, SAE-corrected, and is topped with a smaller version of the blower introduced in 2009 on the Corvette ZR1. The Camaro E-Force (PN 1597, automatic trans; PN 1598, manual) uses the larger rotor set from the LS9 and bumps the manual trans Camaro from 426- to 570-hp SAE. Edelbrock documentation rates an E-Force supercharged LS3 even higher, at 599-hp, using the "standard-correction" common to the performance aftermarket.

One attractive feature of the Edelbrock system is that, for those wanting their hot rods to have a stealth look, while GM's Z28 supercharger requires a specific hood with more clearance, E-Force fits under the standard Camaro hood so as not to giveaway your "supercharged secret" until you pass a Corvette.

Another big selling point? Right now, E-Force is the only Camaro supercharger kit with California Air Resources Board (CARB) Executive Order (EO) approval. This means E-Force is street legal in all 50-States and will pass state exhaust emissions inspections.

Vic Talks, then We Drive.

Why was Edelbrock, one of the oldest and most recognized brands in the performance aftermarket, late to jump into the aftermarket blower business? Last Spring, just before the Camaro E-Force was introduced, CHpg visited Edelbrock in California to get the answer, straight from the guy who's name is on the building.

"We'd been considering something like E-Force for a long time." Vic Edelbrock told us. "In the late-'90s, when we first looked at the (GM Gen 3/4) engines, there was only so much you could do with a set of heads and a camshaft and it wasn't easy to make a manifold. You're lookin' at 40 horsepower, maybe. We needed something for the LS engines we could put on and get an appreciable gain of horsepower.

"I looked at centrifugal supercharging. We almost bought a maker of centrifugal superchargers but that would have been a mistake, in my opinion. A few years later, I talked to Eaton, but they were thoroughly plugged-in with Magnuson. At that time, unless a company doing OE that had what you wanted, you were dead in the water because superchargers were kinda hard to make.

"But, knowing what we could do with boost in kept us looking in that direction. A couple of years ago, when Eaton gave us the opportunity to participate in their (TVS supercharger) program, that energized us because supercharging is a way of gettin' horsepower like no other."

Later that day, Edelbrock's Vice President for Research and Development, Rob Simons, and I went for a drive in the company's 2010 Camaro development vehicle which, from a powertrain standpoint, duplicates a supercharged Tom Henry Racing Camaro except it lacks THR's additional dyno-tuning work.

Many of the company's test cars have a small fender script: "Edelbrock: The FUN Team". Near the company's Torrance, California headquarters, Crenshaw Boulevard runs for half a mile or so alongside a giant Exxon-Mobil refinery. It was there I had some "fun" in a demo of what Vic Edelbrock meant about "...gettin' horsepower like no other."

From a first gear roll, I punched it. The throttle response was just about instantaneous–thanks, in part, to Edelbrock's very good calibration work. A second later, as the engine pulled into it's best torque range, the red Camaro was spinning the tires. I pedaled it a bit and she hooked so, I let it pull just about to the rev limiter. I got second gear, whacked the throttle wide open, again. Second is a hoot in this car! While a stock SS accelerates sportingly, with stick-shift versions of Chevy's sports coupe, the impact of E-Force on the engine's torque makes the 5G Camaro a rocket ship. I banged third and stayed on it until about 4500. Fun?! An E-Force supercharged Camaro is a whole lota fun! And...most blown THR Camaros will have 30-horsepower more through headers and custom tuning, making for one blown bat outa hell.

All American Design

At the core of E-Force is Eaton's new, sixth-generation, "Twin-Vortices Series" R2300 rotor set which was developed in the late-'00s for the ZR-1's 638-hp LS9 engine and is manufactured in the U.S, at a plant in Athens, Georgia. The "TVS" sets new standards for aftermarket superchargers.

While Eaton supplies the rotor set, Edelbrock developed and manufactures the rest of E-Force's major hardware, including a large aluminum casting, poured at Edelbrock's foundry at San Jacinto, California and machined at the company's main facility in Torrance, which serves as both the supercharger case and the intake manifold.

The start of an E-Force Supercharger case at the Edelbrock Foundry is the assembly of the cores. Here, a foundry worker sets the foot-long, runners in place. Image: Edelbrock, LLC.

The mechanized crucible at left scoops molten aluminum from the melting furnace then transfers it to the line of black boxes in the background. Those are the core boxes on a conveyor system and each holds one blower case. The crucible fills one core box then goes back for another load while the conveyor moves the next box into position for pouring. Image: Edelbrock, LLC

In Edelbrock's Torrance manufacturing facility, a blower case is being removed from a pallet which holds it during the CNC machining process. Image: CHpg Staff.

Viewed from the rear, the finished blower case before assembly. The part is black-powder-coated prior to machining. Image: CHpg Staff.

A Camaro E-Force Supercharger ready for installation. It is an amazingly compact package. The E-Force is a front-drive design with a front intake, slightly left and below the drive rotor's shaft, and a top exhaust. It needs neither a jackshaft, used by some aftermarket superchargers, nor complex intake ducting used on others. Image: CHpg Staff

A key advancement is the R2300's increased displacement over the largest fifth-generation Eaton blower, the M122, which was the basis of a number of aftermarket supercharger kits. Eaton categorizes blowers by the volume of air they displace during one rotation of their rotors. With the fifth gen, "M-series", the unit of measure was cubic inches (M122 is 122 cubic inches or 1999 cc.) With the TVS line, it's cubic centimeters (R2300 is 2300-cc.). About 300-cc more displacement and other enhancements has the R2300 flowing about 20% more air along with having a wider dynamic range than the M122. It builds boost more quickly at low rpm and can sustain it at higher speeds.

This is math art of rotor sets from the Eaton M122 and R2300 superchargers. Big difference--four lobes rather than three and a 100° greater helix angle. Image: Eaton Corp.

Not only does the TVS rotor set add performance, but it does so without the characteristic loud whine typical of "modified-Roots" superchargers previously used in aftermarket blower kits. One enabler of that is a switch from three to four lobe rotors and a significant increase of the rotor helix angle from the Gen 5's 60-degrees to 160-degrees for TVS.

Those changes allow better "porting"–how the air gets to the rotors through the supercharger intake. The more tightly-twisted, four lobe rotors allowed Eaton to enlarge the supercharger inlet which slows the air going through it. That is a significant advancement over the fifth-generation which, under some conditions, had air flowing at sonic speed through the inlet but slowing substantially as it filled the rotor cavity. Such a large change in velocity increased both the power required to drive the unit and noise radiated through the case and out the throttle body.

There was more work on efficiency and noise reduction at the supercharger outlet. "Backflow ports or 'slots' were added to the 3rd generation, primarily to quiet the sound of the supercharger," Eaton's Development chief for the TVS, Mike Sitar, told us.

"Backflow is the method of compression within a Roots device. Air enters the inlet port, gets closed off by the rotor faces, then transfers to the outlet at inlet pressure. As it hits the outlet port, if you didn't have backflow slots, the air would immediately rush backwards, through the outlet port, to bring that cavity up to outlet pressure, then the rotors would come into mesh and force the air back the other way, through the outlet. That's a full, air flow reversal in the outlet port.

This view of the outlet of an M122 outlet shows one of the backflow slots Eaton used in the Gen 3, 4 and 5 designs as a noise reduction measure. Image: CHpg Staff.

"That reversal creates a high level of pulsation and noise. Backflow slots allow the air from the outlet to begin pressurizing that closed chamber before it moves to the outlet port. They allow air flow, into the supercharger, through those ports, then out the outlet port, maintaining one-way flow through two different ports. We took a percent, maybe a percent and half hit in adiabatic efficiency, but it, also, allows a one to three decibel decrease in noise. It does impact efficiency of the supercharger, but our biggest goal was noise reduction.

"The TVS does not have those backflow ports," Sitar continued. "Its backflow function depends on flow from the outlet to the rotor bore. There's actually a hole–we call it a "blowhole"–located within the rotor mesh. When the rotors mesh, there's still an open area that connects the rotors across the top of this cusp within the supercharger. In TVS, backflow occurs within the rotor set itself. The air is never moved to the discharge port, then brought back in.

More math art explains the TVS supercharger family's "blowhole" feature used to reduces noise caused by backflow. Image: Eaton Corp.

"The blowhole exists continuously, it just moves forward all the time. It starts in the rear, after the inlet closes, and travels forward as the rotors mesh. It always exists between the rotors, but its position changes all the time.

 "This allows our backflow event to be more than twice as long (than with the Gen 5), so before the rotor even opens to the outlet; the air is almost completely pressurized inside the supercharger.

"The TVS still pressurizes the intake manifold through backflow, which defines it as a Roots device, but when it goes to the outlet port, it's primarily one-way flow. The TVS is 5-10 decibels quieter, compared to a fifth generation supercharger, and a lot of that is because of backflow management."

The set of 56-tooth, blower drive gears in an M122 are shown at left.  The R2300 has 101-tooth gears. The near-doubling in tooth-count moves the gear noise to a higher, less-objectionable frequency. Image: Author.

GM found during LS9 development that noise radiated by the supercharger was reduced by 10-dBA and it's a logical to conclude that the noise reduction is similar with the E-Force system on a Tom Henry Racing Camaro. By going from three to four lobes, Eaton raised the frequency of what noise was left making it less noticeable. Additional noise reduction came from an increase in blower drive gear tooth count from 56 to 101 which raised the frequency of the gear noise to a less annoying level. Bottom line: an Edelbrock blower still makes noise, but it's not near as loud, because of Eaton's work in controlling air flow, and less objectionable, because of its higher frequency.

Some of the engine's power is used to drive the supercharger. Engineers call that "input power requirement" and limiting it is important to both fuel economy and the supercharger's ability to increase performance. For better gas mileage, E-Force has a bypass valve which opens during part-throttle operation. When manifold absolute pressure drops below about 69 kPa (10 psi), the bypass opens and intake air flows from the supercharger outlet, through the valve and back into the blower inlet. With the bypass open, the supercharger consumes only about half-a-horsepower which has minimal effect on fuel economy.

In this image, the bypass is closed. When it's open, the supercharger consumes about half-a-horsepower and has minimal effect on fuel economy. Image: Author.

Eaton also reduced input power requirement of the blower when it's on boost. At the engine's power peak, it dropped from around 115 hp, for the M122, to about 75-hp for TVS. This reduction came from the efficiency improvements cited earlier and efforts in friction reduction, chiefly with the rotor surfaces which mesh.

One reason the R2300 is the most efficient modified-Roots superchargers on the market is minimal clearance between the lobes of the rotors. Image: GM Powertrain.

During the rotors' first turns, part of the black coating abrades away, leaving lobe contact areas better matched to each other and able to run extremely close. All surfaces of each rotor except the shafts are treated with the abradable powder coating, however, it only abrades in the areas shown. Image: CHpg Staff.

Rotor sealing is a double-edged sword. The tighter rotors mesh, the better they seal and the less leakage the blower sustains, however, a tight seal means more friction and more power needed to turn the blower. The TVS rotor set maintains a tight seal, but with less friction due to:

1) Exacting tolerances Eaton uses during machining and assembly. Because rotor clearance remains more consistent from rotor set to rotor set, the minimum clearance can be less.

2) Rotors treated with a graphite-based, abradable powder coating (APC).  During the rotors' first few turns, part of the coating abrades away, leaving rotor lobe contact areas better matched to each other, able to run extremely close and lubricated by the graphite. That provides enhanced sealing with reduced friction.

3) A design that is dimensionally-stable at outlet temperatures up to 300°F. A rotor set that is dimensionally-stable at higher operating temperatures means  there is less rotor expansion so clearance can be set tighter. For more technical discussion of superchargers click here.

Cooling and Tuning

Higher intake air temperature makes the engine more prone to detonation. The nature of supercharging is that, because it compresses air going into the engine, it adds heat to the charge air.  Edelbrock attacks that problem on three fronts.

First, improvements discussed previously cut temperature rise by 15% compared to the M122, so not only is the R2300 better performing, smaller and quieter; it adds less heat.

Second, typical of many superchargers used in high-performance applications, the E-Force has an air-to-liquid, charge air cooler. Some call this an "intercooler" but, if we're going to be dead-nuts accurate, it's a "charge air aftercooler" because it cools the intake charge after it exits the supercharger.

Third, the system uses the wave tuning effect to further limit heat rise.

At a glance, Edelbrock's supercharger may seem a copy of GM's hardware, but while Rob Simons' team was inspired by the ZR1's blower; there are significant differences. Like GM did with the LS9, Edelbrock opted for two charge air cooler heat exchangers for easier packaging, but key to E-Force fitting under a base Camaro hood was putting those heat exchangers in a different place.  

We benchmarked the GM supercharger," Rob Simons told us, "and discovered aspects we wanted to change. It wouldn't fit under a Camaro hood. Ours had to be lower and we achieved that by moving the intercoolers to the side. That gained about two inches. In addition, the GM's intercoolers overlap the supercharger outlet, so there's restriction. Getting them away from the outlet improved air flow." Image: CHpg Staff.

The heat exchangers have a separate cooling system consisting of an additional radiator mounted at the front of the Camaro's cooling stack, an electric pump, a reservoir and associated plumbing. The system holds a gallon or so of coolant and is capable of cooling the intake charge up to 70 degrees.

There are two of these heat exchangers which sit either side of the blower case. This is a significant difference in packaging from how GM locates the exchangers for the LS9 and LSA and gives Edelbrock's supercharger more space to use for the long intake runners. Image: CHpg Staff.

Ample space in front of a 5G Camaro's cooling stack allows a generously-sized radiator for the E-Force charge air cooler. Image: Edelbrock, LLC.

Charge air coolant is circulated in the system by this Bosch electric coolant pump. Image: CHpg Staff.

The charge air cooling system is separate from the engine's cooling system, has its own reservoir tank and uses the same type of coolant as the engine. Image: CHpg Staff.

Another major feature differentiating E-Force from GM's and the aftermarket's Roots blowers are long intake runners in the bottom of the supercharger housing. "When air flows down into the LSA's ports," Simons stated, "it has to go around the injector which sits right above the port. To not constrict the port entry, GM siamesed the runners, so the port is shrouded by the injector and there is no demarcation between runners.

Moving the heat exchangers to the side not only lessens the space needed for hood clearance but it allowed Edelbrock to put long runners beneath the blower case. Couple a TVS with short runner manifold then compare it to the same blower coupled with a long runner manifold. Use the same engine, same pulley ratio, same rpm and you'll get the same airflow, but the pressure, from 2000 to 5000 rpm, can be as much as two pounds lower. That makes for less temperature rise and less parasitic loss. Image Edelbrock, LLC. Image: Edelbrock, LLC.

"Instead of short, siamesed ports, we used space we gained moving the intercoolers for individual runners underneath the supercharger. We have 12-inch runners, which provide a tuning effect. Each four runners go from below an intercooler to the opposite cylinder head. In addition, the injector doesn't impede flow. It's in the same location, if the air goes down, it was in the way. When the air goes across, it's not."

"In a ZR1 supercharger, after air flows horizontally though the intercoolers, it makes an abrupt turn then goes down, into the  heads. We wanted the supercharger to flow more freely, so we don't have the hard right turns," Simons told us. Image: CHpg Staff.

Few Roots or screw blower systems go this route because of the complex design and casting necessary but the advantage is the effect resonant tuning has on the engine's performance. In the critical 2000-5000 rpm range, you'll observe enhanced mid-range torque when you compare an E-Force to one of the other, Roots systems. The individual runner manifold also allows a more efficient spark schedule in Camaro's ECM calibration and that further improves  response and fuel economy. For a more detailed discussion of long runner manifolds, read this sidebar on blower tech.

This is the E-Force reprogrammer. The calibration for a stock Camaro is 50-state legal with a California Air Resources Board "EO Number". Image: Edelbrock, LLC.

During my drive in the Edelbrock Camaro on Torrance streets and nearby I-405, I found that besides more power and less noise, the E-Force system exhibits the outstanding drivability one expects from a production engine, something absent with some of the other Camaro blower kits on the market. Doesn't matter how you drive it: stop-and-go traffic, lugging in sixth, cruising the 'burbs at 30-40 mph, part throttle high rpm in first, going for high mileage on the highway at 55 mph or cruising at 90 on the Interstates out west–whatever.  Edelbrock has its calibration down pat and, because of that, E-Force is a new drivability benchmark for aftermarket blower kits.

Finally

During development Edelbrock determined that the stock Camaro air filter box  posed a restriction and needed to be enlarged. Every Camaro E-Force comes with this larger air filter top and a high-performance Green Filter. Image: CHpg Staff.

Edelbrock benchmarked competing  aftermarket superchargers and found that with some of them belt slip was a problem. Because of that, design of the blower drive and the drive belt selection received much attention.Every E-Force comes with the Goodyear Gatorback belt which is the only belt Edelbrock recommends. Image: CHpg Staff.

An E-Force system comes with everything necessary for installation on a stock Camaro L99 or LS3 including a handheld reprogrammer containing the engine controls calibration.

Tom Henry Racing is a factory-approved Edelbrock E-Force Installer. THR Camaro E-Force system prices start at $8300.00 which includes the supercharger system, installation, custom tuning and a 12-month, limited warranty. In addition, Edelbrock offers three extra-cost, extended warranties which offer coverage of up to 5 years or 100,000 miles.

A lot of parts? You bet. This is why installing the E-Force is best left to facilities such as Tom Henry Racing which are trained and experienced in supercharger work. Image: Edelbrock, LLC.

For more information on superchargers, read our sidebar on blower tech.