2005 Mustang ROUSHCharger Supercharger 101

By Sam Haymart

Read about the 2001-2004 ROUSH supercharger system here.

The 2001-2004 Roush supercharged Mustangs set a new paradigm in the world of aftermarket modifications with a supercharger that offered OEM engineering, integration, and performance to a level that nobody else had previously attained. With the long wait over, Roush Performance has now released the ROUSHCharger system in kit form for the 2005+ Mustangs with the 3V 4.6 V8. Because the new generation Mustang had both a completely new engine and control system as well as fuel tanks and fuel subsystems, a completely new ROUSHCharger system had to be engineered.

The following archive is based on information gathered from Roush Performance documentation, reports from Roush supercharged Mustang owners, and bit of wisdom we have gleaned from sources within the engineering brain trust that created these cars. Because of this, the following information should be considered to be somewhere between opinion and fact, but closer to the latter. We suggest that your results may vary and we invite you to keep us up to date on what has worked for you and to what degree it has not.

The 2005 Roush supercharger system is offered both in aftermarket kit form to the public and is offered as a dealer installed option at Certified Roush Ford Dealers. Because the kit is available to any dealer who can install it on any car, a Mustang should not be considered a certified Roush Stage 3 Mustang just because it has the supercharger. Certified or “real” Roush Stage 3 cars that were planned to be such from the factory will have the appropriate serial numbers from Roush. That said, the performance of the cars will be the same, as mechanically they are the same as it relates to the supercharger system. This is one area where buyers will have to beware in the future when looking for a true “Stage 3 Roush Mustang”. There are already dealers as of this writing who are slapping the ROUSHCharger on lesser Mustangs and marketing (and charging for) them as Stage 3’s. Be careful you get what you pay for or pay for what you get.

The heart of the supercharger system is a custom specification M90 blower that was been optimized by Roush. Like before, the M90 used has some proprietary differences that Roush specified for their units that gives it superior efficiency and flow compared to the “off the shelf” blower from Magnussen/Eaton. The part number is different from the unit specified for the earlier Stage 3 system from 2001-2004, but the units are virtually identical. The intake manifold and intercooler assembly is all new for the 3V 4.6 V-8 and people will be happy to know that the charge motion control valve (CMCV) system is tossed aside. A clever “CMCV replicator” electronic black box is provided to keep the ECU happy. The intercooler supplied is the same part number as the 2001-2004 systems. Because of the efficiency advantages offered by the proprietary high flow manifold and intercooler, combined with the custom supercharger assembly, it offers superior performance compared to other systems with the same boost of 6 psi. The upshot of this is more power with less boost, meaning longer engine life and better fuel efficiency.

In the past, one of the most common misconceptions about the Roush supercharger system is that it is overpriced. The new system comes in at a price point that is far less than the 2001-2004 set up because it comes with a lot less major replacement assemblies such as flywheels, alternator, fuel tank, fuel pumps and a secondary FEAD assembly. The new system is certainly a leaner and less complex composition of parts than the one it replaces. This makes it more attractive for the weekend installer as it will be a far less intensive operation. There are still some advanced electrical wiring, modification of steel and plastic parts, and plumbing tasks that require an experienced and able installer with the appropriate tools. See the 2005+ ROUSHCharger Parts List and Installation Manual ( PDF 4mb) for more details.

Of note, the new system makes due without the famed secondary sheave FEAD that used a collection of large aluminum castings, idler pulleys, and an additional floating crankshaft pulley to drive the supercharger. Instead, the new ROUSHCharger utilizes a single 6 rib belt. The system now uses the existing alternator and brackets, but modifications are necessary to them for relocation. While the older systems and conversions replaced the entire fuel system including the tank and pumps, the new supercharger only replaces the fuel injectors with higher flow units and lower temperature heat range spark plugs. Evidently the new S-197 Mustang’s fuel system provides sufficient fuel pressure for the boosted engine’s performance.

One of the second most misconceived notions about the system is that it is easily modified just as any other car or system is. The jury is out at this time as to how the new ROUSHCharger will be able to be modified and to what level those modifications will be successful. The following is an outline as to how individual areas of the ROUSHCharger system are set up and how mods may be achieved.

Tuning:

The package includes an ECU reprogramming that utilizes proprietary software. The supercharged 3V 4.6 wont work without it. This software is all new to the 2005 Mustang as new variables such as the drive-by-wire throttle body, variable valve timing and the CMCV system have to be counted into the programming. While at the time of this writing we do not yet have all the background information on the software, previous experience with Roush products tells us that the OEM programming taps the maximum safe performance from the stock 4.6 3V engine. The Roush software adjusts various data tables based on readings from the standard hardware such as the O2 sensor, MAF sensor, and adjusts the tables and where in them to read the data. Thus MIL eliminators and other sensor replacements with a Roush supercharged car cripples the Roush ECU software’s ability to read and adjust to important data. (see Exhaust section)

Intake Tract:

The Roush Supercharger package uses a completely new air intake tube that carries the factory MAF sensor, albeit in a new location nearer to the throttle body. The factory air-box is retained, but modifications are done to provide higher airflow. A high flow air filter is provided in the ROUSHCharger system as is a cover plate for the hole left behind by the relocated MAF sensor. Because the 2005 Mustangs have an integral MAF sensor, replacement MAF has been a difficult proposition. To replace the Roush air-tube with a new CAI or MAF assembly would be a difficult proposition considering that it connects to the stock Mustang oval TB on one end and a round air box on the other. Further, it curves delicately around components requiring changes in the shape of it‘s cross section, such fabrication would be highly difficult. While in the past, supercharged Roush owners had depend on aftermarket CAI’s as an easy bolt-on for 10-20rwhp, it appears this mod is a thing of the past without a great investment of time and money.

Fuel System:

At this time we can only share that the new ROUSHCharger only provides a higher flow injector set with their system a reprogrammed ECU software. There is obviously enough fuel system capacity with the factory provided horsepower. The future will tell as to what fuel system mods are necessary as our owners test the waters.

Exhaust:

In the past, Stage 3 owners have successfully added various combinations of headers, X-pipes, and mufflers for additional horsepower. Because this system will be available both on cars with Roush high flow exhaust systems and stock Mustangs, the variations in rwhp gains will likely be wide. Most aftermarket cat-back exhaust systems give out anywhere from 5-15 rwhp. 2001-2004 Stage 3 owners reported mild gains on average of 5-8rwhp with catted X-pipes. Note again, that using MIL eliminators and/or and off road X pipe severely cripples the Roush ECU's ability to adjust and compensate, setting the table for less performance and unsafe AF ratios.

Supercharger Pulley:

There have been smaller supercharger pulleys marketed for the earlier generation Roush supercharger system that ups boost by about 1-2 lbs. Owners of the 2001-2004 models have reported a stronger pull and rwhp gains of 9-15 hp on average have been reported. Of course, adding a pulley increases boost and theoretically leans out the AF ratio. The ECU can mitigate this to a degree but if you live in areas with high altitude like Colorado or hot temperatures like Arizona, you probably want to make sure your AF ratios are safe once installing the pulley. Again, we are awaiting data on both available pulleys and what results owners will have.

Under-drive Accessory Pulleys:

On a supercharged car, under drive accessory pulleys are not a mod. This is because in most cases under drive pulleys actually slow the supercharger and lessen the boost.

Intercooler:

On most all intercooler cars dedicated gear heads have tried using freon type sprays, extra fans and other cooling measures on the heat exchanger of the water-to-air intercooler in hopes of cooling the air charge and thus gain power. This does work in principle, but this approach has not yielded a mainstream following. There is a larger heat exchanger that is manufactured in the aftermarket that has a significantly larger capacity that some owners have tried. We have yet to see any significant proven results at this point in the way of dyno tests to tell how much if any gains come from this.

Heads, increased displacement, and cams:

At this point we don’t have any data from real world owners or cars who have utilized larger displacement versions of the 4.6 engine or have had custom head or camshaft installations. There have been a few owners reported to be working on such modifications and we will revise this archive when we get data from them.

Nitrous:

If you do it, don’t do it upstream of the supercharger. The jury is still out on the viability of the new 3V 4.6 at the time of this writing, as to the amount of power the engine can make before coming apart. Surely in time we will be revising this.

So how much power can I get?

Roush quotes 415-420 hp depending on the press release. A published dyno sheet from Roush Peformance quotes 417. Our experience is that Roush historically undervalues it performance numbers, meaning that in the real world, performance usually exceeds their claims. We will revise this archive with real world results as they come.

Are you a pioneer? Let us know about your ROUSHCharger experience, what mods and what power you have.