What You Should Be Buying
Our second question to the aftermarket specialists was what parts should'99-'04 owners put on their cars? Like all open-ended questions, theanswers varied, and everyone agreed that to a certain extent it dependson what you want to do with the car. But several key components wererepeatedly mentioned.
Hardly typical of the daily...
Hardly typical of the daily driver norm for late-model edge cars, thisyellow demon from the Kenne Bell shop sports a high-boost screw blower,slicks, and a few extra supporting parts to make well over 600 rwhp. Ittakes an improved short-block for the 4.6 GT engine to live at thesepower levels, plus a prepped fuel system and other supporting parts,which partially explains why such combinations are relatively rare.
The common theme with everyone we talked to was almost everybody wants aMustang that does it all--well mannered on the street, with more power,and better handling and braking. It isn't just about straightline speedanymore.
And we'll say we were pleased to note that what the market is buying andwhat the market should be buying are pretty much the same thing, savefor one point. Everyone goes for more power first, then upgrades thesuspension and brakes. Those items should be tuned up first, then morepower added, but few people do it that way because they're all excitedabout more power.
This is doubly true of supercharging. Do the suspension and brakesfirst, then add the blower. You'll save a ton of wheelspin and possiblya trip backward into something hard and expensive in the process.
Ultimately, we'll repeat our long-standing advice on Mustangmodification. There are two things you need--besides money--to make thebest time of tuning. Most importantly, you need a goal and a plan onreaching it. Interested in drag racing? Then you'll want powerproducers, tons of rear axle gear, and to eliminate as much weight as ispractical (removing the air conditioning is the big one here). The dragguy is also interested in a soft suspension tune, and must budget forslicks and small front wheels and tires. He's a prime candidate for ablower or nitrous, too.
On the other hand, an open-track fan can put up with more weight withoutreal penalty, needs a stiffer suspension, and has durability under toughconditions--namely summer heat--high on his priorities. And theopen-tracker really does need to step up his braking and suspendersbefore adding more power.
As you can see, it depends on what you want your car to excel at whenyou are finished modifying it, so give your ultimate goal some thoughtat the beginning.
The second must-have is opening a dialogue with a tuner or parts vendor. Work with these people on establishing a parts purchase andinstallation plan that suits--or at least comes close to--your budget.Information on what is available, and what works in your region, or evenwhat your tuner is capable of handling, play a great practical part inachieving a fun Mustang with a minimum of false starts and lost money onso-so parts purchases. This is true if, like the vast majority ofowners, all you really want is a nicer, more capable street car thatwill likely never see a racetrack.
OK, what are the near universal recommendations from our tuners? Toppingthe list was an old favorite, rear axle gears. Always the best bang forthe Mustang performance buck, moving to lower ratio gears in the ol'8.8-inch differential is reasonably affordable and gives an immediate,unmistakable increase in acceleration performance.
The devilish detail is which gear to buy. Stock, the New Edge Mustangs,both V-6 and V-8, came with 3.27:1 gears. They really are a goodcompromise between low-speed acceleration performance and freewayflying. By keeping engine rpm relatively low on the freeway, the 3.27gears do a major part in promoting fuel economy.
Performance ratios available for the 8.8-inch differential are 3.55,3.73, the newcomer 3.90, and 4.10. Many 5.0 traditionalists will adviseyou that the 3.55 is the best all-around gear, but that is with 5.0s. The less torquey, smaller displacement 4.6 engines need more help, andso the 3.55 is the Two-Valve's best economy/slight performance ratiogearset. In the wide-open West, where 50-mile commutes are not uncommon,drivers would be happy with 3.55s simply because they're spending somuch time highway cruising and $3.00 for a gallon of gasoline is a realthreat, but there's more performance to be had. If high-speed freewaydriving is not a major consideration, which is typical in the East andMidwest, then 3.73 gears are the default ratio. These will definitelygive a noticeable boost in acceleration more than the 3.27 cogs whilestill not driving you batty on the highway. In fact, if in-town runningaround is really all you do, the 3.73s may actually improve yourmileage--assuming you don't pull a John Force launch from everylight--because the engine doesn't have to work so hard to get the carmoving.
Finally, there are 4.10s. Knuckle dragging gears for sure--don't go hereif endless hours of freeway driving figure in your plans. On the otherhand, if brutal three-gear blasts are what you're into, or if you run a28-inch tall slick at the drags, then 4.10s will cure what ails you.
Typically, automatic transmission cars want one more step in gear thanmanuals, and this is where the 3.90 gear ratio comes in. Offered by Pro5.0 (yep, same folks famous for shifters), the 3.90 cog is relativelynew to the Mustang scene, and is proving an excellent gear for automaticNew Edge cars. It's also a good option for manual-transmission ownerswanting everything the 3.73s can offer, and who might really want the4.10s, but are afraid of the high highway rpm and resulting fuel burn.In that case, the 3.90 is just that "little bit more" without having togo all the way.
And if you are from the old 5.0 school, don't sweat the lower 4.6 ratiorecommendations. The 4.6 engine is happier turning higher rpm than the5.0, so more gearing is welcomed.
With the rear gear change comes a need to recalibrate the electronicspeedometer. This is where some sort of electronic tuner comes intoplay, the Diablo-Sport Predator was one we heard plenty about, but theSCT Xcalibrator is popular as well. Not only does the flash-tuner fixthe speedometer, it also cures the check engine light issue brought onby off-road
X-pipes, so MIL eliminators are unnecessary. Furthermore, flash-tunersare reprogrammable so future tuning changes--cam, blower, and so on--canbe accommodated at any time. This saves the delay and cost of havingthe computer re-flashed or a new chip burned every time you make ahardware change.
And let's not forget you can typically get about 10 rwhp even on a stockTwo-Valve with a flash-tuner or chip.
While larger mass air meters...
While larger mass air meters have not proven to be a '99-'04 necessity,a larger throttle body is a cost-effective improvement. This pair of 70and 75mm Accufabs are representative of the wide choice available. Theusual bolt-on car will make the expected 300 rwhp with the 70mm unit.
Continuing with the power theme, the next recommendation is to attend tothe engine's intake side. An upgraded throttle body, cold-air kit, orairbox improvement all fall in this category. There are a variety ofimprovements going on here. The stock inlet, for example, is not overlylarge, and has some convoluted rubber hoses, which produce turbulence inthe airflow path. Thus, a smoother tube or pipe helps raise airflowwithout having to grow too large and take up all the underhood realestate on the passenger side of the engine compartment.
We prefer a cold-air kit that places the air filter inside the fender. This avoids breathing hot, underhood air (less dense, less power) andfan wash, which can confuse the mass air meter and lead to maddeningdriveability woes.
The throttle body is a simple call. Aftermarket throttle bodies arelarger and flow more air than the stocker--the large oval unit availablefrom FRPP is appropriately sized, and there are others from Accufab,BBK, and so on, depending on your manifold. Like many other inletimprovements, a larger throttle body by itself is not the magic key toperformance nirvana, but combined with the other breathing mods, ithelps. An important building block, in other words.
Here's another '99-'04 over-achiever;...
Here's another '99-'04 over-achiever; but we wanted to show the Bullittintake manifold. These upgraded factory intakes are all aluminum andbreathe better than the GT's plastic piece, so they are worth power.Pricey for sure, we'd consider one of these intakes once we had finishedwith all the other bolt-ons.
Intake plenums, often called elbows, are recommended. These devices arereasonably priced and do produce a couple of horsepower. Testing hasshown they won't quite match the power gain of a throttle body, but inconjunction with one, they will raise the power curve just a couple ofpoints all across the tach. You'll do best cost-wise when buying thethrottle body and elbow as a package.
At this point, the more drag-racing oriented tuners recommend a shifter,other tuners leave it until later.
Exhaust was the next power recommendation. Luckily, the X-pipe has thetuner's favor, as well as the customer's ear, so it seems the way to go. As for cat or non-cat X-pipes, tuners say it really is up to thecustomer, and in fact, sales are about evenly split on this item. Wehave to say the high-flow cats are our recommendation. We have a strongethical bias when it comes to hobbies and clean air, and from a powerstandpoint, eliminating the cats is only worth a few horsepower anyway.
There is one bothersome exception to this, and that is if you arebuilding an open-track car. The extended periods of full-throttleoperation on a road course can seriously heat catalytic converters ofany type, and in that case, not having cats can save a fire. The rightway to do it, of course, would be to have cats on the street and swap toan off-road X-pipe (or a dedicated track-only exhaust system withstraight-through mufflers and no tailpipes) for track days.
For street cars that occasionally go to the dragstrip for a couple offun runs, don't sweat overheating the cats. They'll be fine. And, infact, the same is likely true at the road course if you are notabsolutely flat to the floor, but rather out to enjoy your car withouttraffic, police, and road hazards.
After-cat choices are as wide-open as always, but the Bassani andMagnaflow systems that are so popular seem to be doing a fine job. Thereality, of course, is that on a street car where some semblance ofdecorum is required, there will be a small top-end power loss due tomufflers anyway, and just as likely a low-range torque gain compared torunning short, open pipes. But, with the realistic bolt-on powerexpectation just over 300 rwhp, losses due to mufflers are notoutlandish anyway. Bottom line: today's popular quality systems arelikely giving all the power a street-licensed car can.