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Vortech V3 SCi-Trim Supercharger Kit - Boost Basics
Cranking Up The Boost Involves More Than Just Spinning The Blower Faster.
Last month we modified a '93 Mustang GT with a basic supercharger kit from Vortech. The entry-level blower added 6 psi of boost to our test subject, and the result was 96 rwhp. It is a bare-bones system that includes nothing more than a new self-lubricating Vortech V3 SCi-trim blower kit. JPC Racing handled the installation and proprietor Justin Burcham tuned it with a custom chip. After seeing how easy it was to add nearly 100 rwhp, we wanted more.
The car pounded out 405 rwhp, up from the baseline of 309. The test vehicle runs a stock short-block with Trick Flow heads, Edelbrock intake, and a mild camshaft. Adding more with a supercharger seems easy enough-just spin the blower harder, right? To do so, we upgraded our base kit to the High Output (H.O.) version from Vortech, but along with it came some extra baggage.
In most cases, adding more boost is easy. A smaller blower pulley size will spin the centrifugal blower's impeller faster. "Changing the blower pulley is the easiest way to add more boost. But when doing that with the base kit, you need to address some issues," comments Ricky Best of Vortech Superchargers. Just adding more boost comes with consequences, and the company's H.O. upgrade addresses those very issues.
Burcham also wanted to employ some other goodies, too. On the Vortech side, the two major components in the H.O. kit are an eight-rib blower pulley setup and a bypass valve. Vortech also includes a T-Rex fuel pump (which we added last issue due to the modified engine package), different FMU setting to adjust fuel, and an MSD/Vortech timing retard box (when you're under boost).
The Vortech parts work great, but Burcham elected to leave some components in the box. First was the FMU-he discarded it since this engine has Ford Racing 60-psi injectors, a healthy fuel-pump arrangement, and custom tuning. The ECU is modified with a chip from DiabloSport. Burcham made adjustments to keep the air/fuel ratios steady. The MSD/Vortech timing retard box was also left on the shelf as Burcham turned to the MSD Digital Programmable 6AL-2 to control timing under boost and enhance the spark output, among other things. The JPC mastermind also likes the 6AL-2 because of its rev-limiter capabilities. This MSD box keeps things simple, and enthusiasts don't have to mount multiple ignition controls and rev-limiter devices.
The timing retard is required to prevent detonation due to increased cylinder pressures. Our mild 6 psi of boost only required a little timing removed. Thanks to our vision of 9-10 psi, our engine needed more timing removed. We couldn't just dial back the timing manually in the ECU like in the 6-psi application because it would compromise driveability. The best way to do it is remove timing little by little as boost increases, and the only way to achieve this is to add a timing control box.
"I like the programmable 6AL-2 because it has everything in one box. That makes it easier to mount, and MSD has great programmable features that can be adjusted on a laptop," comments Burcham. "Adding an MSD 6-series box of any kind is always a great idea with a supercharger. The multiple sparks help the combustion process."
MSD sells several versions and the Digital Programmable 6AL-2 is its latest. The base model 6A enhances the ignition output with multiple discharges. MSD adds L to the name for the rev-limiter option and the product is the widely known as the 6AL box. Moving down the list is the 6-BTM, which is essentially a 6A box with provisions to retard timing per psi of boost along a fixed curve.
The programmable 6AL-2 is the top of the line and incorporates three rev limiters, programmable timing curve for nitrous and boost applications, timing controls that are more accurate and controllable than the dial on MSD's other products, timing launch control to help get the car out of the gate, and of course, the benefits of the multiple spark discharges for better ignition power. Since it is a digital ignition system, the timing curves and rev limiters are adjusted and plotted on a computer program from MSD. The software is compatible with PC computers only.
Other products work effectively to remove timing based on a fixed curve using a dial, and the digital system allows us to get very specific in timing controls. For example, the dial is put to 1-degree ignition retard for every 1 psi of boost in other ignition systems. As boost rises, the timing is retarded to that pre-determined number. With the programmable 6AL-2, we can create our own curve. As Eric Holliday of JPC Racing stated during the installation, "The curve with this box is not fixed. We are starting with only a half degree of timing retard for 1 psi of boost. The low boost doesn't require as much timing to be removed as it will at 9 or 10 psi. It allows the car to be snappier in low boost."
Burcham chose to lock in the timing at 25 degrees total (10 degrees base with spout out) and rely solely on the MSD box for timing commands. He programmed the retard to start off lightly. As mentioned, at 1 psi of boost, timing is retarded only a half degree. As the boost goes up, so does the retard-at 3 psi our test vehicle's engine will have 1.5 degrees of timing removed. As manifold pressure rises, the retard gets more aggressive. At 5 psi, there is 5 degrees of timing negated. Burcham set the timing retard at 9 degrees at 8 psi and 12 degrees removed at 10 psi. He chose to remove more than 1 degree per 1 psi of boost at the higher levels because of the stock short-block in the test vehicle. A 2-bar map sensor is hooked up to the 6AL-2 so it can reference the manifold boost.
Last month we outlined the fuel system, which is a bit overkill for this application, but Burcham would rather have too much than too little. Initially we added a set of Ford Racing 60-pound injectors (with a Pro-M 80mm MAF sensor matched to the injectors), a Vortech T-Rex in-line fuel pump, and a UPR 255-lph in-tank pump. Burcham kept the engine running smoothly and cleanly thanks to a DiabloSport chip-it allows the engine to idle nicely and not overrun with fuel.
This month, Burcham adds a new product that is set to hit the market shortly. It is an MSD Programmable Fuel Pump Boost Control that utilizes a PC-interface to build a custom curve to increase fuel pump output (through voltage increase), much like the programmable 6AL-2 does for spark.
Overkill? Definitely, but we felt the product was too neat to pass up, so Holliday wired it into the car. Both the UPR and Vortech fuel pumps are wired into the box, so they react the same to the adjustable curve. A vacuum line is run to the fuel pump-control box so it can read boost output and adjust the voltage.
Adding the fuel pump booster is an easy way to supply more fuel to the engine without buying new fuel pump(s) or even adjusting the computer tune in the ECU. The box will add a minimum of 1.5 volts at 1 psi, and it can go as high as 22 volts at 15 psi. In stock trim, the fuel pumps operate at 13.7 volts at idle with a functioning alternator. The MSD software is simple too. You don't need a background in programming to make adjustments. It is a basic graph that plots boost pressure and voltage output.
MSD references manifold pressure in a different format than the normal pounds per square inch (psi). The program calls it psia, or pounds-per-square-inch absolute. The simplest way to think of it is boost with the normal earth's atmosphere of 14.7 psia added in. Zero boost on a psia gauge would read 14.7; anything above represents boost. For example, a reading of 15.7 psia represents 1 psi of boost in an engine. It's important to understand the simple conversion because MSD references manifold pressure in this form.
As we mentioned earlier, increasing boost is as easy as adding a smaller blower pulley. Of course, spinning the blower too fast can cause heat and impeller overspeed. This kills efficiency. But for this test, we knew the blower was well within its limits since this was an upgrade kit was from Vortech.
Another bump in the road with spinning a supercharger harder is belt slippage. Upping the impeller speed comes at the cost of having less belt wrap on the smaller pulley. Less contact means less belt traction, and ultimately, slippage. To remedy this, Vortech includes an eight-rib blower-pulley system, which is a step up from the base kit's six-rib belt, and Vortech supplied us with wider blower and crankshaft pulleys for the eight-rib upgrade. The six-rib drive is acceptable for up to 6 or 7 psi; after that, it's recommended that you add an eight-rib drive to prevent belt slip.
Ricky Best also points out that there is another critical component included in the H.O. kit. He highly recommends a bypass valve, which is easily described as a pressure-relief valve for when the throttle blade is closed and the engine isn't ingesting all of the extra airflow from the blower. Without the relief of pressure, the air will back up in the inlet system between the throttle body and the blower discharge. The reversion will find its way to the impeller, causing it to skip and jerk, causing belt problems in minor cases. The jerking can lead to a broken supercharger head unit. The reversion situation is most prevalent when the engine goes directly from WOT to a closed throttle blade. The sudden shutting of the door to the manifold will cause a major problem in blower applications at 8 psi or higher.
Vortech routes the vented boost back to the inlet elbow on the impeller side of the blower. The boost cannot be vented to the atmosphere or downstream of the MAF sensor. The MAF sensor has sampled the air and therefore it needs to be recirculated upstream of the MAF sensor. The ECU reads the sensor and determines the engine is ingesting a certain amount of air. If the sampled air is released to the atmosphere, then the engine will run overly rich, if it can idle at all.
Vortech provides a plastic elbow with a nipple on it so the bypass valve can be connected back to the inlet system upstream of the MAF sensor. We aren't using the elbow with our UPR pipe. The UPR inlet pipe feeding our supercharger was installed because the Pro-M 80mm MAF sensor wouldn't mate with the Vortech inlet system due to its size. The blower kit is designed around a stock 55mm MAF sensor housing, not the massive 80mm unit on this car. Luckily, UPR molded the inlet pipe with provisions to route the bypass valve hose into the inlet pipe. The standard Bosch bypass valve included in the Vortech kit is rated up to 12 psi. For applications above that level, Vortech sells properly sized valves for race and street use.
The smaller lower pulley (6 inches versus 6.75 inches) brought total boost up from 6 psi at 5,500 rpm to 10 psi at 5,800 rpm. Output rose from 405 rwhp to an impressive 460 rwhp-above what we like for a stock short-block. This was the absolute maximum power Burcham was willing to put to the stock internals. These mods netted us a gain of 55 rwhp from an additional 4 psi of boost.
The curve was more aggressive through the mid-range thanks to the timing chart that Burcham plotted. The timing removal started off passive and grew more aggressive as the boost went higher. It is a technique that couldn't have been done without the capabilities of the MSD programmable 6AL-2 box. This allows the car to have more low-end as it starts making boost and keeps the engine safe at high psi readings. In naturally aspirated trim, the test vehicle produced 309 rwhp, showing a gain of 151 rwhp with 10 psi of boost. For those keeping score, that amounts to 15.1 rwhp per 1 psi of boost.
Our original intention was to add a Vortech Powercooler after the H.O. upgrades. That plan, unfortunately, was spoiled when the H.O. upgrade put our engine's output to 460 rwhp. It was much further than what Burcham deemed safe for a stock short-block application.
The Powercooler is a great product that replaces the discharge tube with a air-to-water intercooler. "Adding the Powercooler will allow for more timing, which means more horsepower," says Burcham.
We didn't get to sample this extra horsepower on Macintosh's ride, but Burcham did have a car in the shop that had just received a Powercooler upgrade. Power increased from 501 to 549 rwhp.
The addition dropped air inlet temperatures, but Burcham says the gains are due to the increased ignition timing he can run in the combination without fear of detonation. Cooler air is denser and less prone to pre-ignition (detonation).