July 19, 2007

Horse Sense: It doesn't matter if they're internally lubed or oil fed, centrifugal superchargers such as Paxton's IL deliver top-end horsepower without adding unmanageable torque down low. That typically translates into easy-to-manage traction on street tires.

Paxton's new internally lubricated (IL) supercharger (right) offers all the performance but fewer installation hassles compared to its familiar oil-fed Novi 1200 brother.

Mustang fans love supercharging, except when it comes to punching the hole in the oil pan for lubrication. Some do it, but it's an angst-filled moment; others just can't swing the hammer. Using the opportunity to sell more superchargers, Paxton has developed-or redeveloped-an internally lubricated supercharger. The blower carries its own supply of oil and doesn't require any communication between the engine oiling system and the supercharger. In turn, that means there's no need to plumb a pressurized oil feed line or return line to the engine's oil pan. It's a concept Paxton pioneered in the ball-drive days but abandoned for an engine-oil feed when the boost and rpm levels of modern hot-rodding proved too much for the friction ball drive.

A pressurized oil feed from the engine remains a viable way of lubricating a centrifugal supercharger, and Paxton has no intention of abandoning it. There are some good reasons for the company to add an internally lubed blower to its offerings. We've already mentioned the first: punching the hole. Putting a hole in a perfectly good oil pan to fit an oil return line is too much for many people, so providing a choice between an oil-fed blower and an internally lubed one should result in more Paxton blower sales.

Eliminating the oil-feed and return lines also means fewer steps during installation, making it quicker and cheaper. That's always a plus. Especially since Paxton is seeking to expand its sales to car dealers. Notoriously parsimonious, dealers demand quick-and-easy installations, and are resistant to what they perceive as mechanical mayhem-punching holes, for example.

Remove the cover on the IL and this is what you'll see: the large drive gear and the smaller impeller gear covered by the plain disc of the oil slinger. The cover provides the location for the two ball bearings seen here.

Finally, oil-fed superchargers rely on gravity to return drained oil to the engine. In Mustang applications, this isn't an issue. For Paxton, there are installations where a gravity drain is problematic. In those cases, an internally lubed blower offers the ability to mount the supercharger almost anywhere the drivebelt or jackshaft can reach, including lower than the oil pan.

Challenges & Solutions
Giving a supercharger its own oil supply raises questions of oil cooling, cleanliness, aeration, distribution, and-most importantly-control inside the tight confines of the supercharger transmission.

To understand how Paxton addressed these concerns, let's review what's happening inside the drive section of the company's centrifugal blower. The action begins at the supercharger pulley, driven by the blower belt. The pulley is mounted to a shaft that's part of a large drive gear inside the supercharger's transmission. It mates with a much smaller impeller gear, which is mounted on the impeller shaft and directly turns the impeller. The two gears feature helical (curved) teeth and form a gear ratio of 3.6:1. The relationship between the crankshaft pulley and the blower pulley is also a gear ratio, typically around 2:1, giving the overall 7.2:1 a step up between the crankshaft and the supercharger impeller. Therefore, if the engine is ambling along at 2,000 rpm, the impeller and its gear in the blower are turning 12,960 rpm. At 6,000 engine rpm, the supercharger is whizzing along at 43,200 rpm. There's tremendous energy whirring inside the blower's transmission and at its impeller.

Remove the gears from the supercharger housing and the details of the redesigned housing are apparent. The bottom of the housing is the oil sump at the bottom in this photo. The angled fences are anti-windage devices, as is the semicircle fence around the impeller bearing bore. This housing is used on oil-fed and IL Paxton superchargers.

It's this prodigious rotation inside the transmission that causes all the frustration when trying to lube and cool the gears and their ball bearings inside the blower trans. The big concern is the gears, as the ball bearings need only a mist of oil for lubrication. Oil-fed blowers spit oil through a 0.032-inch hole at the gear interface, with a constant flow of filtered oil supplied by the engine. The amount inside the blower is controlled by the small orifice, and it's constantly draining out the bottom of the blower to the oil pan. There's never a large volume of oil in the gearbox, just a heavy mist to constantly wet the surfaces.

With internal lubrication, the supercharger has 4 ounces of oil. Think of it as a wet sump compared to the dry sump oiling of the oil-fed blower. This volume is necessary to allow it to cool, but pouring this much fluid into an unmodified oil-fed blower transmission means the dervish of gears entrains the oil and races it around the perimeter of the transmission housing. This heats the oil, beats air into it causing it to foam, and doesn't put it where it's needed, at the center of the transmission where the gears and bearings are.

Paxton's solutions are to cast fences in the oil's path to stop the roundy-round flow, provide a slinger to fling oil where it's needed, and use specially formulated lightweight oil for its lightweight and anti-foaming capabilities. Oil filtering is addressed by regular changes.

To see how the new internally lubricated transmission housing and its oil-control fences are laid out, it's best to examine the photos and captions. Paxton arrived at this configuration, including the shape and volume of the IL supercharger's transmission housing, by beginning with a standard oil-fed blower fitted with a clear plastic cover. Once the flow was visually determined, trial and error gave the various shapes and angles needed to kill the roundy-round action, direct the oil flow, and shear or knife the air/oil hurricane inside the transmission.

The drive gear (left) and driven-impeller gear (right) are identical to those in the oil-fed supercharger. The only difference is the addition of the oil slinger-the large flat disc-to the impeller shaft assembly. The slinger dips into the oil sump and flings a fine film into the drive-gear portion of the blower. It's the only oil "pump" in the system.

Regular oil changes are required, but at press time Paxton hadn't determined the exact interval. It will likely be once a year/ 12,000 miles, but could be slightly longer or shorter depending on testing. It was sent to an independent test lab for several durability trials, each approximating 50,000 miles of use. Oil changes are facilitated by drain holes in the bottom of the blower. The regimen was promised to not involve pulling the blower out of its brackets to turn it upside down. We're expecting a hose and drain valve at the bottom of the blower. The oil is filled through the dipstick hole.

Paxton says the exact oil specifications are proprietary, but confirms the lube is a light synthetic oil designed to avoid foaming. Motor oil can't be substituted, as it would foam, cause more heat, entrain, and perhaps bubble out the vent.

Function & Reliability
Naturally, Paxton wanted the new IL supercharger to meet or exceed all the existing standards for power output and reliability. Because the blower uses the same pulleys, gears, impellers, and volutes as its oil-fed units, it's no surprise Paxton's testing showed no difference in power output between IL and oil-fed Paxton superchargers. We've included before and after dyno tests of the prototype IL Mustang installation in a sidebar; they show the expected gain at the rear tires.

Most of the supercharger cover is filled in to form a thin opening between the drive and driven gear sides of the supercharger housing. This reduces windage and improves oiling. An O-ring seals the cover-to-housing interface.

Paxton's durability testing was conducted in the shop, on the road, and in outside labs. The only parts requiring validation were the lubricated parts in the blower's transmission and the oil itself. Because the gears and bearings are the same as those used in the oil-fed superchargers for years, the only unknown was the lubrication and cooling.

While Paxton used its chassis and engine dynos, the most definitive IL tests were done on the road using instrumented test mules with extensive datalogging. The driving was done on the hilly country in Paxton's Southern California region, including the long and steep Highway 14, Baker, Cajon, and Grapevine grades, as well as the long run to Reno, Nevada, including the high-altitude Bishop grade. The data showed plenty of underhood heat, around 200 degrees on 98-degree-ambient days, and some supercharger heat. The blowers were instrumented to reveal the individual bearing's temperatures-front and rear impeller bearings, for example-and the lubricant. Testing was designed to find the source of blower heat, and the two important factors include the ambient temperature and impeller speed.

Paxton designed the oiling improvements to function in the IL and oil-fed superchargers, so this housing is now used for all Paxton 1200- and 2200-series superchargers. The three threaded holes along the bottom are for the return oil drain when used as an oil-fed blower. Three holes are provided to accommodate any clocking of the supercharger-they'll likely all be plugged in IL applications; in oil-fed blowers two are plugged and one has a drain fitting. At press time, Paxton thought it might provide an oil-drain fitting and hose in one of the holes on IL blowers to facilitate the oil change.

Interestingly, the blower oil temperatures tend to be slightly lower in the IL superchargers than the oil-fed units except under the worst conditions. In any case, Paxton was comfortable with the IL's heat performance and has no plans to fit the supercharger with a pump and oil cooler, as was optional toward the end of the friction-ball era.

Fitting In
Paxton's business requirements for the IL blower were that the new supercharger fit into the existing lineup with minimal disruption. The IL superchargers augment-not replace-the oil-fed superchargers, which continue in production. In fact, as the photos detail, itshardware improvements are also used in the oil-fed superchargers.

The IL drops into the existing oil-fed blower brackets and mates with all tubes, belts, and so on. If an existing oil-fed blower customer wanted to switch to the IL blower, it could be done by swapping in the new blower head unit, as the engineers refer to the supercharger proper. It also means a minimum amount of new part numbers for the Paxton organization to absorb. Expect the familiar-standard (non-charge-cooled) and high-output (air-to-air charge-cooled) kits.

Impeller trim levels for the Paxton blowers are the same for oil-fed and IL kits. These would be the Novi 1200 rated at a 680hp capacity and the Novi 2200 rated at 900 hp.

Which to use-the traditional oil-fed or the new internally lubed Paxtons? Punch the hole or change the oil? The choice is yours.

Assembled on the bench as they are in the supercharger, the 3.6:1 ratio gearset would have the blower pulley at left and the impeller at right. The close quarters among the gears and oil slinger are obvious. Besides being quiet, the combination of wide and helical gears provides more gear engagement.

IL Installation
Installing the Paxton IL supercharger follows the same basic procedure as the fam-iliar oil-fed variety, except there are no oil lines to plumb. Assuming the more popular high-output kit is being installed with its complicating air-to-air charge cooler, plan on a six-hour installation; you'll probably spend an entire weekend if it's your first blower install.

Major points include fitting the blower and its bracket into the front engine dress-it shares the serpentine drivebelt with other accessories. Removing the front bumper cap to bolt on the charge cooler and fitting a second fuel pump to the assembly submerged in the fuel tank are other things that need to be done. No holes are drilled, but the engine coolant and other hoses are cut and extended or rerouted. Engine management upgrades are accomplished with a DiabloSport Mafia MAF extender and a reflash of the engine computer via a Diablo Sport Predator.

Once installed, the supercharged engine will need premium 91-octane or higher fuel. It will give a definite gear noise even with the helical gears (heard mainly outside the car), and swell the powerband starting around 3,500 rpm until near bursting at redline.

Cost & Availability
IL superchargers will be available in mid-July 2007, according to Paxton. Only the '05-'07 Mustang kit will be available initially; the second kit will come shortly thereafter for the evergreen '86-'93 Mustangs. They remain a major market for Paxton. Kits for SN-95 Mustangs will follow the Fox cars.

It's tougher to call the kit prices-they hadn't been set at press time. According to Paxton's estimate, the individual IL superchargers (blower head only) will cost a bit more than the existing oil-fed units, but the IL supercharger kits should be slightly less than their oil fed brothers, thanks to the missing oil plumbing.

ON THE DYNO
BASELINE PAXTON IL DIFFERENCE
RPM TORQUE POWER RPM TORQUE POWER TORQUE POWER
2,043 224 87 2,008 236 89 12 2
2,117 227 92 2,107 234 93 7 1
2,205 228 96 2,205 238 {{{100}}} 10 4
2,{{{300}}} 230 101 2,320 242 107 12 6
2,435 231 106 2,409 246 112 15 6
2,515 229 109 2,509 248 118 19 9
2,{{{600}}} 230 113 2,610 249 123 19 10
2,706 232 120 2,708 252 129 20 9
2,817 233 124 2,827 260 140 27 16
2,901 231 128 2,910 263 145 32 17
3,012 229 131 3,012 261 149 32 18
3,113 228 135 3,105 262 155 34 20
3,205 229 139 3,212 259 158 30 19
3,316 231 145 3,304 264 166 33 21
3,407 235 152 3,407 270 175 35 23
3,509 239 160 3,513 280 187 41 27
3,600 243 166 3,608 290 199 47 33
3,704 242 171 3,719 298 211 56 40
3,805 244 177 3,817 304 221 60 44
3,922 246 183 3,906 308 228 {{{62}}} 45
4,000 247 189 4,000 306 233 59 44
4,103 248 193 4,119 313 245 65 52
4,203 250 200 4,211 320 255 70 55
4,320 251 206 4,312 327 268 76 62
4,400 250 209 4,{{{405}}} 330 276 {{{80}}} 67
4,511 249 213 4,501 328 280 79 67
4,610 246 215 4,606 328 287 82 72
4,719 245 219 4,708 327 293 82 74
4,821 244 224 4,813 326 298 82 74
4,{{{924}}} 242 227 4,904 327 305 85 78
5,000 {{{240}}} 228 5,006 330 313 {{{90}}} 85
5,101 237 230 5,107 330 320 93 90
5,207 234 231 5,203 332 329 98 98
5,302 229 231 5,312 331 334 102 103
5,419 225 231 5,407 330 340 105 109
5,503 221 231 5,503 329 345 108 114
5,600 217 231 5,602 328 349 111 118
5,708 213 231 5,710 326 355 113 124
5,805 209 231 5,{{{825}}} {{{323}}} 357 114 126
5,910 204 230 5,904 321 360 117 130
6,000 201 229 6,000 316 361 115 132
6,125 195 227 6,119 315 366 120 139

Shown here are dyno results produced by one of Paxton's test cars, an '06 Mustang GT convertible. It's owned by Paxton Manager Tom Catalano, and it's stock other than the blower and some bolt-on suspension parts. It's also the same car seen in our installation photos. You may see short-tube headers in the background, but they weren't installed when the dyno tests were performed on Paxton's in-house Superflow chassis dyno.

All test data was supplied by Paxton from development testing. We're showing the naturally aspirated baseline run and a typical power run with the supercharger installed. As expected, the power gains are dramatic and correspond exactly with the equivalent oil-fed supercharger.

Paxton uses high-quality, aerospace ball bearings where appropriate. That's mainly on the impeller shaft, which spins up to 50,000 rpm and must absorb thrust due to the helical-cut gears. The bearing carries our favorite three-word inscription, as well as "Vortech," which is Paxton's sister company. The brand name identifies the bearings without letting the world know who the supplier is, and confirms Paxton's dedication to quality control-not just any old bearing is being used.


Clearance between the drive gear and housing is tight, about 11/416-inch along the oil control fences. This keeps oil from clinging to the gear and roping itself around it. Shedding the oil reduces the power needed to drive the blower and allows the oil to gravity-feed its way to the sump.





Cooling is the main job of the blower oil; only minute amounts are needed to lubricate the ball bearings. Thus, the slinger doesn't move a ton of it, and at 14,000 to 50,000 rpm, accuracy isn't a problem. Enough oil gets washed over the gears to provide lubrication and cooling. In fact, simplicity was a design goal of Paxton's; the company knows that the less complicated the part, the more reliable it is.



Taking another look at the lower end of the blower housing shows the occasional machining touches designed to maintain gear-to-housing clearance.








Another consideration given to using the new Paxton blower housing for the IL and oil-fed superchargers is shown here. The U-shape cutouts in the windage fencing allow spray oil to reach the impeller in oil-fed blowers. The 0.032-inch oil spray jet is located in the threaded hole seen across from the U-shape window; a second window and hole are provided 180 degrees away to allow different supercharger clockings. Only one is used at a time in oil-fed blowers; none are in IL applications.



No changes were made to the back of the supercharger housing. It works with the same impellers and scrolls as previous Paxton superchargers.








To use only two covers across the entire supercharger lineup, Paxton has drilled and tapped the outside of the covers with numerous threaded holes. The only difference between the two covers involves one large threaded hole for a belt tensioner. This is the non-tensioner cover used on S197 Mustang applications.





Oil level and quality checking is done via dipstick. Two holes are drilled and tapped in each cover to allow the dipstick to fit in whichever hole is uphill. The other one is plugged. The supercharger holds 4 ounces of special synthetic oil which will likely require an annual change.






IL superchargers are vented using this trick dipstick. The vent hole on the cap is clearly visible; it communicates with the blower internals via the slight gap left between the dipstick and cap when the cap is swedged onto the stick. Even in this close-up shot, the clearance is nearly impossible to see. Also shown are the sealing washers and plug used on the hole opposite that occupied by the dipstick in the blower housing.



Jumping to conclusions, here's the finished Paxton 2200 high-output (charge-cooled) IL installation on an '06 Mustang GT. From the top it's essentially impossible to see the difference between it and the existing oil-fed kit. The IL offers no difference in blower sound qualities and the weight difference is negligible.





The finished installation is compact, with the blower belt barely visible between the engine and supercharger. While this view mainly illustrates the S-bend in the intake-air path, along with the open element air filter and aftermarket mass air meter, it also shows the dipstick and matching plug atop the supercharger housing.




While the throttle body is never touched, the intake manifold must be removed to access the engine coolant crossover passage running just behind the alternator.






Our installation was done on a car that already had the blower kit installed, so we're showing the results of the coolant hose rerouting. The welch plug is where the stock Ford coolant bypass exits the engine. The Ford nipple is extracted with some brutality, and the welch plug is installed. The Paxton water neck is then installed atop the coolant crossover casting; it's visible here just above the welch plug.



With the coolant rerouted, the intake manifold is reinstalled, along with Paxton-supplied high-capacity fuel injectors. The intake manifold, throttle body, fuel rails, and almost all the associated plumbing is unchanged.







One hose section that changed is the PVC assembly. The stock PVC valve is retained, but it's slightly rerouted. A series of cut hoses and clamps replaces the stock molded plastic line.





A pair of idler pulleys is mounted on the front of the engine using existing holes. They both use unusual Paxton-supplied stud/bolt hole combination fasteners. These are needed because the blower mounting plate mounts to the bolt hole portion of the fastener while the idler pulley is sandwiched between the engine and blower mounting.





Sticking the camera between the engine and the radiator shows us the reconfigured coolant bypass hose assembly. It includes the thermostat housing. Paxton supplies the necessary molded hoses and instructions on how to modify the existing hoses; the point is to open the necessary space for the supercharger.





With the pulleys mounted, the serpentine belt is next. The engine accessories and supercharger share the same belt; Paxton supplies the required longer belt in its kit. It must be threaded into position before the blower goes on.





Paxton has long been known for its stout blower mounts, and the IL superchargers fit into them with no modifications. A series of standoffs correctly space the blower mount; the bolts are left loose for now.





The supercharger is placed in its mount, a procedure that requires fiddling. The supercharger, its mount, the drivebelt, and some hoses all come together at once.






At this point, the installation switches to the air-to-air charge cooler fitment. The first piece of aluminum tubing is slid into position. It will lead from the downward-facing supercharger discharge to under-car tubing that takes the air forward to the charge cooler.





The Paxton charge cooler is big-it can support 900 hp worth of charged air. It mounts behind the front bumper, using long replacement bolts and existing bolt holes. The front bumper cap must be removed to access this area, a job that looks more involved than it is.





Supercharger-to-charge-cooler tubing is mounted on the driver side. The clamp that suspends the tubing from a tab on the radiator support is being tightened after all the tubing is in place.





On the passenger side, the charge cooler discharge air is routed using more aluminum tubing. All the tubing is nicely bent and mounts with simple screwdriver work.






The cooled intake air is lead to the throttle body using a heavy, cast-aluminum intake tube. It mounts using simple hose clamps.






With the charge cooler and tubing installed, the front bumper cap can be replaced.








Some of the front bumper cap is secured by the same fasteners holding the inner fenders in place. Once the bumper cap is in position, the inner fenders can be reinstalled and the pop-on plastic fasteners replaced. A special tool for prying the plastic nails helps, but a screwdriver will work.




To make room for the charge-cooler coolant tank, the passenger-side engine-wiring loom must be pulled out of the way. This is done by pulling it against the inner fender, then bending the soft A/C service point tubing back to form a lock. It's sort of crude, but is easily done, costs nothing, and has no effect on A/C functioning or testing.




With the wiring loom pulled aside, the coolant tank is lowered into position between the engine and right shock tower. Some assembly of brackets and nipples is required, but it's all simple wrench work. The stains on the tank attest to our photo car's status as a test mule, with multiple IL installations. The techs were guessing this was the car's 10th installation of this kit.




A coolant hose extension is required; it lies atop the radiator and is joined by crimping a band clamp. There's a special tool for this that's not supplied by Paxton, but the job can be done with wire cutters if care is taken to crimp the band from both directions to even the load.




Due the high volume of air between the supercharger and the throttle body in air-to-air charge-cooled Paxton kits, they use two bypass valves. Here's the first one assembled with its plumbing being placed below the supercharger.





With the first bypass assembly in place, the second one goes in. Again, this is simple hose-clamp work, but the working room is cramped. This step is easier with someone to hold things out of the way.





Installing the cold-air kit is easy. A new mass air meter is supplied to replace the stock one molded into the air filter box.






There's no worry about extending the wiring to the mass air meter; a Diablo Mafia unit supplies the needed wiring. It's a simple plug-and-play device, which extends the useful range of the MAF electronics. In this case, it also supplies some welcome wire length.




Paxton supplies an electronic tune in a DiabloSport Predator flash tuner. It communicates with the engine management computer using the diagnostic port under the dashboard.






With more air being pumped into the engine, more fuel must be injected. Paxton's auxiliary in-line pump is added to the existing Ford fuel pump which lives in the fuel tank. Removing the rear seat reveals this large, round rubber plug. Pry off the plug to locate the fuel-pump access in the top of the fuel tank.




Under the tank access cover you'll find the fuel pump, fuel level sending unit, and fuel pickup/return assembly. It's secured by a locking ring that's tapped out using a long punch.





With the fuel unit removed from the gas tank, the Paxton auxiliary pump can be piggybacked to the stock pump. The job is shown half-finished here-the Paxton pump is the silver cylinder with the black top, while the factory pump is bright white and to the left. All that's left to attach are several fuel hoses. The assembly can then be returned to the fuel tank, finishing the supercharger installation.