IEMC Featured STANG
Rocky Gibbs Supercharged 6 Speed 2005 Rocket
About Rocky's Mustang... Cali (short for Mustengo Caliente).
My 2007 GT ragtop was previously featured in the newsletter. I also have a 2nd Mustang, a 2005 GT 5-speed coupe I bought in June 2014. It’s been my “driver” since then. I found it on a downtown car lot and was attracted as it is my preference Redfire color and has the red interior upgrade to provide contrast with the black. It’s my first manual shift vehicle in 25 years and the first ever in a vehicle with a greater level of performance than my previous ones, those being work pickups and low powered cars. I don’t like manual shifts in city traffic, but when cruising on rural two-lane roads with hills and curves it is great fun.
I first put aftermarket wheels on it. I helped Carl Sontowski replace the carpet last November. I also installed SLP Loudmouth axle-back exhaust and a Ford Racing Cold Air Intake and custom tune. I upgraded the brakes with ceramic pads and stainless steel brake lines. The results performed well and the car was fun.
However, as often happens with fun cars, one gets comfortable with them and begins looking for more, be it performance or look. I think most Mustang owners could identify with that statement. There are two ways to get more performance; replace the car with something else or modify the car one has. Several factors should influence one’s final decision. A car upgrade for me would have been to find a late model GT500. They are great cars for performance but they represent a significant upcharge. My preference was to “personalize” what I had, or in an earlier era, it was been called “hot-rodding” it. Even though these mods were not inexpensive, they cost much less than trading up to a GT500. My result is a modified GT than gives no external visual clues to its modifications. I consulted a few club members with performance Mustangs and was steered towards supercharging for power and further, to consider a centrifugal unit versus the twin screw type. I did on-line research for both types and came to agree that centrifugal was the better choice for me. However, common sense dictated that when considering a significant power upgrade, one must also consider the drive train for upgrade to handle the increased load to avoid breaking parts on the road to fun.
After a year with the car I was sure the clutch would need replacement within a year. The Carfax indicated the transmission had been previously replaced and when removed, it was obvious it had been replaced with one from a junkyard. I had objections to some of the operating “quirks” of the transmission. From on-line research I found that the “quirks” were actually normal operation for the stock transmission. Along with my complaint of the poor synchronizer operation, my greatest complaint was the wide gap in gear ratio between 4th and 5th (overdrive). I wanted a gear in the middle of that spread. Further research turned up the Tremec Magnum XL 6-speed transmission.
The Magnum is the aftermarket version of the TR6060 used in the 2007 and later GT 500, some Corvettes, Vipers, Challengers and others. The Magnum XL is a new model with extended tail shaft housing. The gear shift is mounted directly on the tail shaft for quick, positive, short shifts. There is no remote shift linkage as with the original. The first production version of the XL is built specifically as a bolt-in replacement in the S197 Mustang. Tremec will produce future versions specific to other cars. The gear ratios are spaced evenly from 1st to 5th with an equal RPM drop between the gears, leaving 6th as the cruising overdrive gear. This gives me the gear I wanted between 4th and 5th of the stock TR3650 transmission. In reality I now have 1st through-5th as performance gears. The TR3650 is also rated for not more than 450 pounds of torque so an increased load from more power would be a problem. I decided on a two-phase upgrade approach. First was to do the drive train and then the power.
I had already decided to change the transmission and clutch, regardless of a power upgrade. The best answer for me was a package from Modern Driveline. They are a Tremec Elite dealer. They sell a complete package including the transmission, clutch, bell housing, driveline, mounting hardware, etc. Their kit includes the Magnum XL rated for 700 pounds of torque, a Quicktime SFI approved bell housing, a 600 HP Kevlar clutch from Superior Friction, and a Dynotech 3.5 inch aluminum single piece driveshaft. I also changed to a stainless steel hydraulic clutch line. With the drivetrain work completed the car was more fun to drive and much more responsive with the gear ratios providing what I had been missing. As I don’t do burnouts or otherwise lay rubber, I believe the stock 3rd member and rear axle shafts should be OK, but I may upgrade those as well later. At this point I did consider doing no further upgrades.
However, it’s a fact that with performance cars, one always wants more. Therefore, the next step was the ProCharger centrifugal supercharger from ATI. ATI sells a kit specific for the S197 Mustang. The stock 2005 GT is Ford rated at 300 crankshaft horsepower. As is normal, there is less HP at the rear wheels due to mechanical losses. ProCharger claims a 70-80% boost in horsepower, meaning 500-540 crank horsepower. Dyno reports I’ve seen on-line appear to corroborate their claim. Other Dyno reports I’ve seen on-line show an average of 460 horsepower at the rear wheels with this kit. Of course these are peak ratings only produced at or near redline RPM. The ProCharger is 50 state emissions legal which I believe is important. The kit includes the supercharger, mounting brackets and hardware, air-to-air intercooler and blow-off valve, increased flow fuel injectors and a higher flow fuel pump to feed the injectors. I won’t go into a complete discussion of my reasons for my ProCharger choice, in this article, but anyone interested can discuss it with me at length if they wish. I will point out that ProCharger provides a three-year warranty which was the longest period I found with any supercharger. Other warranties I saw included no warranty, 90 days, with a one-year being the longest period I found. Some other supercharger kits are not 50-state emissions legal which is a problem in Washington. And finally, the ProCharger installation is 100% reversible should one wish to remove it, assuming one keeps the original removed stock parts to re-install.
I was also concerned about the effect of more power on the engine. My research indicated that this supercharger should put me in the upper part of what is considered “safe” for the engine. Time will tell, but everyone I consulted, discussions with ProCharger, and information that I found on-line caused me to feel that unless one is racing extensively, or otherwise always driving it to the max, it should be OK. The weakest engine parts in the 4.6L are the connecting rods with the pistons being next. The bottom end is quite stout and should be good for this amount of power. After all, Ford Racing sells a 550 H.P. supercharger kit for the 4.6L so they must believe it’s a safe H.P. increase. Should I eventually be proven wrong, then I may get a 5.0L Coyote crate motor which produces much more power than the 4.6L and is capable of producing 700 H.P. or more with forced induction added. ProCharger claims their horsepower boost is safe as long as the critical variables (these variables apply to all forms of forced induction actually), are maintained. The critical variables are fuel octane (never less than the minimum the supercharger system’s design requirement), high quality fuel, proper fuel to air ratio and spark timing throughout all RPM’s, and keeping combustion air temperatures as low as possible. ProCharger claims to have the lowest induction air temperature of all supercharges due to their massive air-to-air intercooler. The higher the induction air temperature, the greater the tendency for detonation in the cylinders. Any one, or any combination of these variables performing improperly, can cause detonation. Detonation is always an engine killer.
I purchased everything through Pro Automotive and they performed the installations. Before ordering the ProCharger a cylinder leak down test was performed to indicate the conditions existing inside the engine. While they have installed many ProChargers on a variety of cars, this was their first S197 Mustang installation and there is always a learning curve with anything done the first time. The most problematic issue was not caused by the new additions, but rather adding the Supercharger showed up vacuum leaks in the seals on the intake plenum. The leaks would not allow the car to tune properly because at low RPM it’s leaking vacuum and at higher RPM it’s leaking boost. Ford does not sell replacement seals for the plenum. Rather, one must buy an entire new plenum from Ford or find a used one. However, the new one has been updated to a one piece design eliminating the seals that were leaking in the original. With the vacuum leaks fixed the car tuned right up with the originally supplied ProCharger tune. We may tweak the idling a bit more but it’s quite drivable at present.
The car is now even more fun to drive. If one drives it normally, the car is little different from stock. It drives well on the street just as it did before and the gas mileage has not been diminished. The car already required 91+ octane fuel due to the previous Ford Racing tune. The octane requirement remains at 91+ with the ProCharger. With the added boost it becomes a different car when one “gets on it.” It roars and pushes one back into the seat. It can hit 90 MPH or more in 3rd gear in what to me, is a very short distance. It can hit 60 or better in 2nd gear very quickly. These speeds are attained a little below the RPM redline. I try to stay less than redline to reduce stress on the engine. Research on-line indicated that going from 5000 RPM to 6000 RPM causes as much as a four-fold increase in engine internal stress. Besides, unless drag racing, there is no need to go to redline because with the combination of supercharger boost and the proper ratio spacing between gears of the Magnum XL, it gets moving very quickly. The power is already there when upshifting to the next gear due to the small RPM drop between gears. Ron Prior at Pro Automotive is a lifelong drag racer and can power shift this car as smoothly and quickly as if it were an automatic transmission, resulting in thrilling performance. It surprised both of us that we had no tire spin or chirp when shifting gears, and on street tires. The S197 Mustangs transfer weight to the rear very well under power for “hook up.” With Ron driving, its get in, buckle up and hang on!
I’d sum it up that on the street, before “punching” it, one should be pointed the direction they wish to go as it will go there very quickly. For those of you owning supercharged cars all of this discussion may be “old news.” I’m sure you can brag about your car’s performance and tell me your stories as well. I’d like to hear some of those stories at length. But I’m having fun with my “hot rodded” GT and that’s what it’s all about.
I’m reading in numerous places that the S197 Mustangs are a great car to consider if you want something easy to modify. They are becoming relatively inexpensive to buy. They last for many miles unless maintenance is neglected, or if they have been “pounded.” There is a vast selection of parts available to personalize them, be it for looks, performance or both.
My only other planned addition is a fiberglass functional Ram Air hood to provide cooler outside air and extractors to remove engine heat. The hood will be the only external visual suggestion that the car perhaps has some performance mods. I don’t plan engine or interior dress up items as this car is about driving and performance, not show. In time I may consider a more significant brake upgrade as well without going so large it would require a change of wheels.
I have no personal experience to compare it to driving a GT500 or similar but it’s capable of more performance than I need, at least for now. The problem with all performance cars is that other than on a track, there are few places allowing one to use the power, unless you like traffic tickets or something worse. Some may think it foolish to make an investment resulting in a car with more invested than the car is worth retail. This is always a valid consideration with “transportation,” vehicles, but for a fun performance car (toy), I don’t apply that rule. The purpose of fun cars should not be as an investment, but rather, the fun they can provide. I’d prefer a few years of fun with the car and have the memories versus not having the car and have no memories of the enjoyment it provided. After all, most Mustangs are not used for basic transportation. Most are owned and driven because their owners consider them to be special vehicles and they get fun and enjoyment from them. Hope to see you on the road having fun with your Mustang. – Rocky