Many have followed us in our journey to build a barn-burning drag radial, leaf-sprung monster capable of 4-second blasts down the strip on narrow 275 radial tires and leaf springs. Our build started with a solid foundation from Dart Machinery, Total Seal rings, a Winberg billet crank, GRP billet rods, Ross Racing’s custom flat top pistons, and ARP hardware. It was topped with one of the most wicked top end packages offered for LS-based powerplants in Mast’s canted valve Mozez heads and matching tunnel ram. Then, Comp, Ferrea, and T&D teamed up for a bulletproof valvetrain.
A solid engine platform is critical to being competitive in small-tire racing. However, a solid platform on its own doesn’t win races.
These days, natural aspiration just won’t cut it – you need a power adder. When working up the build, we considered a number of options with consistency as a key goal. As mentioned, we knew natural aspiration wasn’t an option. We’d never be able to get the car light enough and would almost certainly spend a fortune in exotic valvetrain gear to accommodate the RPM a naturally-aspirated combo would need to make the combo competitive. We briefly discussed nitrous. For the 30 to 40 seconds it was considered, we quickly decided we couldn’t trade the kick-in-the-pants feel of the gas for the inevitably of burnt pistons. We liked Ross and the beautiful set of slugs they produced, but we didn’t want to make calling them a habitual affair. Nitrous was out. What about a turbocharger? Turbos are all the rage and for good reason, they make lots of power.
However, we wanted a solid platform that could make big power, rattle the stands from the burnout box, and wouldn’t require an army of electronics and team of programmers to stage. Consistency quickly became a theme. Consistency in the racing program, consistency in the mid-round chores, consistency in the driving routine, and most of all, consistency in the parts we would rely on to make power.
Chassisworks Component Drive System
The Chassisworks Component Drive System, CDS for short, is an extremely popular way to drive centrifugal supercharger units. They can mount the superchargers in multiple orientations and eliminate the need for dicey serpentine or cog belt setups. In addition to running the supercharger, the CDS systems have a number of options to drive other components like fuel and oil pumps.
Here are some other features:
- The legs are indexed for a press fit. This allows them to locate and hold together without the bolts (though you need the bolts). This means that the drive doesn’t have the ability to wobble or walk even if the bolts aren’t super tight
- Uses “pick up at the corner speed parts store” Winters quick-change gearsets that you can buy from retailers like Summit for as little as $65
- Built-in timing pointer
- Built-in crank trigger sensor mount
- Built-in oil level indicator window
- Utilize a stainless billet hub (not aluminum) that doesn’t deflect or shear
- High strength bushings that last a full season
- Provide a crank and blower speed drive that mounts using a standard 1-inch keyed mandrel
- Provisions built-in to change motor platforms while using the same drive unit
- Provisions built-in to change supercharger platforms while using the same drive unit
- Chassisworks provides a number of encapsulated plug and play accessory drive options
Tuning a supercharged system is fairly straightforward. The direct coupling of the supercharger to the crank reduces the complexity of hunting for specific boost numbers based on a wastegate duty cycle, or exhaust output from air, fuel, or timing changes. It’s simple: when the engine makes RPM, the supercharger makes boost. If it doesn’t, something is broken.
When it comes to supercharged boost, there were a number of choices in screw-type, roots and centrifugal systems, but only one came to mind when contemplating consistent big horsepower numbers. We wanted to make sure we connected with the most reliable platform we could think of and that resulted in a call to Brian Ellis, Lance Keck, and Jimmy Martz at Vortech. The guys at Vortech went over the combination, our desired horsepower level, and fitted us up with one of their larger new generation blowers: the V30-123mm. This supercharger was an upgrade from the XB series unit we had run in the past. The transmission received an upgrade, the volute underwent internal tweaks, and the impeller was redesigned to produce more power.
From the outside, the supercharger received a facelift with all-black anodize compared to the “as cast” dull finish on the older units, with an inlet bellmouth that not only looked cool but was designed to direct air to the impeller as it entered the blower through the Camaro’s front lower valence. The setup retained some of the prior generation blowers’ features, like external oiling and ceramic bearings that are unique to Vortech.
Q&A With Vortech
In addition to getting us fitted with a solid centrifugal blower package, the guys at Vortech also took some time to answer a few questions.
DJ: What sets Vortech apart from a more traditional roots or screw-style supercharger?
Vortech: Efficiency. High efficiency equates to less heat being generated, a reduction in power required to drive the compressor, and more net power produced as a result.
DJ: Why did Vortech choose to go with an external oiling system over self-containment?
Vortech: Through vigorous testing, we found that oil does more than just lubricate the internal parts of the supercharger, it also aids in bearing temperature control. This is vital to bearing longevity and supercharger durability. The external oiling system assists in that process.
DJ: When selecting a compressor, why isn’t bigger always better?
Vortech: The proper size compressor for a given engine size and airflow requirement is something of a black art. One of the tools that we use to predict the requirement is a compressor map. This gives us the flow and pressure ratio of the given blower, and with this information we can take the engine in question and determine its airflow requirement.
Far too often, racers will attempt to turn up the blower speed in an attempt to get the performance they think they need, but in turn, it puts the blower in a worse performance area (efficiency island) on the map. – Lance Keck, Vortech
DJ: What happens when the compressor is too big?
Vortech: Running a supercharger that is too large for a given combination may result in that blower running mainly on the left side of the compressor map in a location close to surge. That’s bad. This area of the map is typically far away from the most efficient operation area of the compressor.
DJ: What happens when the compressor is too small?
Vortech: One situation where you have to use a blower that is too small for the engine combination is if it is written into class rules. In that instance, you risk the chance of the blower continuously being in a state of choke. This can (and sometimes does) work acceptably, but under these circumstances, the discharge temperatures and power consumption are elevated. The other downside to running an improperly sized blower is the potential of running the compressor in the transonic region.
DJ: If it is too small, can’t I just spin it faster?
Vortech: Far too often, racers will attempt to turn up the blower speed in an attempt to get the performance they think they need, but in turn it puts the blower in a worse performance area (efficiency island) on the map than if they kept the blower speed in a slower, higher efficiency point of operation.
DJ: What is the limiting component or factor in determining the maximum supercharger RPM?
Vortech: Bearing manufacturer’s recommendation. Once we have this data, we can use FEA and CFD along with a Rotodynamic evaluation to ultimately determine what is a safe impeller speed for a given compressor stage.
DJ: You recommended a 123mm for our LSX engine — how did you arrive at that size?
Vortech: With the airflow requirements that were estimated, this blower has the correct airflow characteristics that meet your needs.
DJ: Beyond the drive system (exhaust versus crank) what makes a centrifugal supercharger different from a turbo?
Vortech: You already nailed it — a centrifugal supercharger is mechanically driven, while a turbocharger is exhaust driven. The volute and impeller design are similar between both power adders.
DJ: What is the single most important thing when selecting a supercharger?
Vortech: The size of the compressor. One size doesn’t fit all applications.
The truth of the matter is it has everything to do with flow and very little to do with boost. Boost is a measurement of restriction, plain and simple. – Lance Keck, Vortech
DJ: What is the most common misconception in centrifugal supercharging?
Vortech: That a specific boost number is required to make a certain horsepower target. Far too often people contact us and say, “I need to make 12, 15, 20 psi,” when in actuality they only need a fraction of that boost number to reach their performance goals. This expectation could be due to any number of things, but the truth of the matter is: it has everything to do with flow and very little to do with boost. Boost is a measurement of restriction, plain and simple.
DJ: What should a customer consider when choosing a supercharger as a power adder?
Vortech: Efficiency is far too often overlooked. The more efficient a compressor is, the more horsepower it will make per pound of boost. Less drive power equals more total horsepower.
DJ: A lot of the new centrifugal superchargers have fancy inlet bells. This seems to be a new trend. What’s that all about?
Vortech: Under the right circumstances, an inlet bell (or bellmouth inlet) can aid in performance. The potential to see gains in blower performance depends on a number of things, but ultimately the main contributing factor is the impeller design — whether it can draw air from the sides or if it is limited to drawing directly from the front of the supercharger. Even the best design can see benefits from a bellmouth inlet. Besides, they do look pretty cool mounted to the front of a big centrifugal compressor!
Calculating Supercharger Speed
Centrifugal compressors like superchargers and turbos have speeds at which the impellers can be safely spun. Exceeding the recommended speed can cause the compressor to run out of its efficiency range, increase heat, reduce power, and eventually fail. No to worry. Each manufacturer will provide a maximum safe RPM for the unit and calculating impeller speed is relatively easy. The equation:
Max Engine RPM x Drive Ratio x Transmission Ratio
In the case of our build: We expect to run the engine to 9,000 RPM, we installed a Winters 1.65 ratio gearset in the CDS unit, and Vortech’s website provided us with a 4.21 internal transmission ratio.
9000 x 1.65 x 4.21 = 59,045.25 RPM
Vortech recommended we stay below 65,000 RPM. With this setup, we’ll be fine.
Vortech: We are continually trying to raise the bar with compressor design. New compressor stages/trims are constantly being designed. We want to make sure our customers have the best centrifugal superchargers available to them. Diverging diffusion technology, Nano Tolerance Technology, and Enhanced Inlet Entries are a few things we have in the works that will have a sizable effect on supercharging.
Putting It All Together
In addition to the supercharger unit, we also picked up a pair of BV57 Bypass Valves from Vortech’s accessory store. Often mistaken for wastegates used in turbo applications, bypasses (also known as blow-off) valves serve a critical purpose for parts longevity. Rather than control boost, they protect the intake system (manifold, throttle body, and plumbing) from parts-damaging boost spikes. When under boost and wide-open throttle, the air from the supercharger makes its way through the intake and into the chamber to make power. When the throttle is closed, the compressor is still making boost, but it has nowhere to go. The valves from Vortech serve the critical function of venting trapped boost pressure into the atmosphere rather than damaging components as the boost finds its own way out.
Once we had the hard parts, we had to move on to the challenge of putting them together in a package that would be conducive to airflow efficiency while fitting in the confines of a 1968 Camaro that was never intended to house over 4,000 cfm of horsepower inducing air. In addition to the supercharger and bypass valves, the combination was built for gas, as alcohol was not in the class rules. This meant we’d also have to fit the combination with an intercooler.
For the task, we went with a Chiseled Performance IC3000 intercooler that sported 5-inch V-band inlet and outlets but was packaged small enough to fit in the front of the car. We had to get the intercooler as far forward as possible to ensure the weight landed where we needed it. The added advantage of mounting the intercooler far forward meant that we could get away with shorter tubing runs, which equates to less restriction and more power. To connect the pieces, we secured 5-inch aluminum mandrel bends. Builders traditionally use 4-inch tubing in this type of application. However, we talked to an industrial HVAC technician to see if he could run the restriction numbers on our application. After asking some questions, looking at some charts, and punching some keys on a calculator, he assured us that we would want to go with the larger tubing. As our tech explained, “In a system like this, you want the fewest number of transitions and turns as possible.”
Mounting The Unit
We have the V-30 123A, the BOVs, the Chiseled IC3000 and a bunch of tubing to sew it all together. Next came the Chassisworks Component Drive Systems (CDS) mount for the supercharger. We ran a CDS unit on the previous combination and it was a no-brainer to stick with them on the new setup. As a result, we fitted the Dart LS Next block with a bunch of billet bling from Chassisworks. The setup included a block plate fitted for a standard LS block, a gearbox designed to carry standard quick-change gears, stands and a blower plate designed specifically for Vortech superchargers, and topped off with an accessory drive to mount our Peterson 6-stage billet oil pump.
Putting together the package was straightforward but did require one minor configuration detail: how fast to spin the supercharger.
As mentioned, the CDS unit required a 10-spline quick change gear set. Winters manufactures a gear that is primarily intended to allow dirt track racers flexibility in making rear differential ratio changes at the track. However, their compact size, wide availability, large ratio offering, and low cost made them perfect for use in the CDS. Choosing the right gear was important, as the wrong gear could result in slow blower speeds and low power or excessive impeller speeds and a broken blower. For this combination we settled on a 1.65 overdrive ratio — this meant that each turn of the engine would result over one and a half turns in the supercharger. From there, the supercharger had its own transmission with a fixed 4.21 gear ratio that served the purpose of further increasing the impeller ratio.
All told, after the two stages of gear multiplication, a target of 9,000 engine RPM would net over 50,000 impeller RPM. Doing the math, 9,000 engine RPM multiplied by the 1.65 CDS ratio and then the 4.21 transmission ratio nets out at 59,045 impeller RPM. If math isn’t your strong suit, that’s OK…there are many online sites can convert a gear ratio — or pulley teeth for those running belts — to get a final impeller RPM. Ultimately, the goal was to heed the advice of Vortech to avoid overspinning the unit and ending up with reduced power, or worse, a broken supercharger.
The supercharger is selected and the gear ratios installed. However, the steps taken here cannot be forgotten, as we’ll have to play with shift RPM and potentially adjust drive ratios once we have on-track data. Our initial math places us shifting in the 9,000-10,000 RPM range with a finish line RPM in the 9,000-plus RPM range.
That means the supercharger could see safe impeller speeds as low as 62,000 RPM or as dangerously high as 70,000 RPM. With some of these unknowns, we’ll need to test and then adjust gear ratios and shift points to make sure the engine pulls through an optimal RPM sweep but doesn’t push the blower to exceed impeller speed limits while making sure we spin it fast enough to turn on win lights.
With the engine completed, our intercooler and plumbing fabricated, and Vortech hardware peeking out from behind the grille of our 1968 Camaro, the journey through this project is nearly complete. Controlling the power comes next.