When it comes to supercharged applications, smaller pulleys equal more boost, right? Well, not always. On most positive displacement supercharged applications, the restriction can be found before the supercharger--in the inlet (air intake, throttle body, and plenum). Whether it's a stock GT500 or an aftermarket bolt-on kit, pulleys can help make more boost, but only up until the inlet has reached its maximum flow capacity.
We installed a C&L Performance cold-air intake and a Ford Racing Performance Parts throttl
Replacing the supercharger pulley with a smaller version will cause the supercharger to spin faster, effectively creating more boost. The same can be said of a larger crankshaft pulley, or any combination of the two. Boost, though, is created by the output of the supercharger (after the supercharger). It can only make as much boost as the inlet (before the supercharger) allows. So there is a point where either the supercharger has reached the maximum of its recommended rpm range, or the inlet is a choke point. Either way, no more boost can be made at that point.
To exercise this theory, we headed to Lamotta Performance in Longwood, Florida. There, owner Jake Lamotta had Ron Manuel's automatic '07 GT in for a new fortified long-block. Lamotta installed Manuel's new FRPP Aluminator (8.5:1 pistons) short-block, freshened stock Three-Valve heads, and then the pre-existing Saleen supercharger. Unique in its design, the Saleen kit offers a long, flat inlet design, which utilizes a stock-style throttle body and cold-air kit.
There are a number of versions of the design of the inlet, and ours was equipped with Saleen's new high-flow lid, coupled with the 475hp airbox system and a stock throttle body. He had also previously added a 2.8-inch supercharger pulley and a 7.074-inch crankshaft pulley, spinning the supercharger to near its limit of useful range. But was he gaining all the benefit from the pulleys?
1 Featuring a Saleen supercharger equipped with the new high-flow lid, Manuel's GT made 4
2 At Lamotta Performance in Longwood, Florida, Jake Lamotta removed the 475hp airbox and
3a Lamotta then removed the stock twin-55mm throttle body and installed an FRPP billet Th
Once the installation was complete, Chris Johnson of SCT Performance tuned the combination for us. It achieved 415 rwhp and 413 lb-ft of torque. Boost peaked at 13 psi and air/fuel was steady at 12.2:1. We tried to keep the AFR the same for each step of the test to make a fair comparison.
Though not bad for a street car, we wanted to maximize the power potential in the quickest and easiest way. To do this, we called C&L Performance. C&L has been an innovator in the cold-air intake business for 20 years, and devotes significant time and resources maximizing the potential of its kits. Proprietor Lee Bender sent us the latest Three-Valve kit from C&L (PN 10699-05PR; $299). This kit, according to Bender, has the capability of flowing over 1,000 cfm.
"The flow capacity of this assembly is 1,070 cfm. The stock intake is 550 cfm, and most aftermarket intakes flow in the 750- to 825-cfm range," says Bender. He also informed us that our existing Saleen 475hp airbox falls in that 750-825 slot, which could be causing a restriction. Lamotta installed the C&L kit, Johnson adjusted the tune, and we spun the rollers on Lamotta's Dynojet. The result was an astonishing 455 rwhp and 439 lb-ft of torque--a 40-rwhp and 26–lb-ft increase!
The next item on the list was the stock throttle body. Ford Racing Performance Parts (FRPP) sent us one of its billet Three-Valve throttle bodies (PN M-9926-3V; $649.95). This twin-62mm bore throttle body has a flow capacity of 1,306 cfm--enough to keep up with the C&L cold-air kit. The stock throttle body utilizes twin-55mm bores, good for only 953 cfm, according to Ford Racing.
Back on the dyno and with another tune adjustment by Johnson, Manuel's GT spun the rollers to 472 rwhp and 450 lb-ft. The throttle body swap alone yielded an additional 17 rwhp and 11 lb-ft of torque. Total increase was up to 57 rwhp and 37 lb-ft--all for under $1,000 and by simply freeing up power that was being lost by a restricted inlet.
3b This piece flows up to 1,306 cfm, according to Ford Racing, compared to 953 cfm for t
4 Lamotta then reinstalled the C&L intake and Johnson adjusted the tune to accommodate th
5 Here is a view of the finished product. Not counting a trip to the tuner, this install
As boost increases, so does the demand for fuel. Even though we were merely allowing the supercharger to work more efficiently, extra fuel was still required to accommodate the higher boost levels. On the last pull, we noticed our air/fuel ratio leaning out at the top of the rpm range. To remedy this, we contacted JMS Chip & Performance, for one of its new PowerMax voltage boosters.
Called FuelMax (PN PM-1000; $329), this 21V/44A voltage booster is designed specifically for increasing fuel pump output easily. Installation is simple, it is easily adjustable, and can operate on a boost reference--ideal for this application.
To install the main unit (which is smaller than a 20-ounce soda) mounts in the spare tire well. One wire in the harness (included) splices into the 12V fuel pump feed wire. Two more wires go to the engine bay (one for power feed, and one for the Hobbs switch), and the control knob and harness are run into the cabin.
The Hobbs switch splices into a vacuum line on the engine to sense boost, and signals the FuelMax to engage when boost is sensed. This is adjustable from 3 psi to 7 psi, according to the user's needs. Also adjustable is the ramp-in and ramp-out, which can help eliminate fuel pressure spikes.