Tom Wilson
April 1, 2005

For those of us who have been living with the late-model Mustang on a daily basis for a decade or more, the all-new '05 Mustang is truly exciting, and at the same time, a bit of a shock. Why a shock? Because we've become so comfortable with the existing car, so familiar with its details, that the all-new machine makes us realize just how much we need to learn about it.

So you can imagine our interest when Jim Bell, from Kenne Bell, wheeled out a brand new '05 GT the first week they went on sale. Like so many in the aftermarket, Jim was eager to get started on developing products-in his case screw-type superchargers-for the new car. And to do that, he didn't wait around for a promotional handout from Ford (almost none have been handed out anyway). He got his the old fashioned way, by exchanging paper with pictures of dead presidents on it.

Jim Bell's engineering background has given him a real curiosity about modifying cars. His is an analytical approach, where he straps the object of his attention to his Dynojet chassis dyno and systematically reduces variables-and disassembles a bunch of hardware-until he's sure about what's going on with the stock car, and what should be possible with modifications.

So, first thing Jim did with his new '05, aside from driving it half a day to get a feel for it, was to tie it to his dyno. The idea was to discover what makes the new Mustang rumble, lay a baseline as to its performance, and divine what sort of power could be developed from it.

It's important to remember that at this early point, no attempt was made to develop parts, at least not directly. The goal from this white-lab-coat session was to determine where easy horsepower might be had, "to see what Ford left us," as Jim put it, and occasionally, to define what might be the ultimate power potential in a certain system (the exhaust, for example).

To jump to conclusions, the new car doesn't promise tons of performance from dead-cheap bolt-ons. Ford has upped its Mustang game considerably, so the easy, low-hanging power fruit is now smaller and higher up the tree. But there is still fruit, and the Three-Valve cylinder head layout promises great power from more extensive modifications, namely forced induction.

Dyno TestingStep one was establishing a totally stock baseline run, and in the finest tradition of magazine testing, we even did that out of order. Kenne Bell had actually been dynoing the car the night before our arrival, while working with Superchips Custom Tuning on a software program for the Xcalibrator. In other words, Kenne Bell and SCT had been working on a tune for the new Power PC engine management computer and its Spanish Oak software. While toggling the Xcalibrator to the stock engine management program was super simple, the gas tank had a good load of 91-octane fuel in it. Ford says the Mustang runs on regular 87-octane, so that's what we wanted to see. We especially wanted to try regular gas once Ken Christley, Kenne Bell's electronics specialist, told us they had seen a gain, simply by switching to 91-octane fuel. But with so much 91-octane in the tank, it was decided to run several tests with it to burn some of it up, then drain the tank and run 87-octane to see what the difference was. We also requested a run with 104-octane unleaded race gas, that Kenne Bell keeps on hand, to determine if there would be any more power with even more octane.

As we started testing, we noted the car was instrumented to read out torque and horsepower, rpm, ambient air temperature, and the air/fuel ratio via a wideband oxygen sensor.

BaselineAbsolutely stone stock mechanically, with 91-octane fuel in the tank, the car averaged 280 hp and 301 lb-ft of torque to the rear tires. It took a minute to hit us, but that is nearly 100 hp greater than the 188-193 rwhp a fresh, stock '88-'93 5.0 Mustang put out. In fact, our personal '91 LX hatch we drove to the test, wearing underdrive pulleys, with the timing turned up to 14 degrees, and breathing through stock headers, a 2.5-inch Magnaflow X-pipe and matching mufflers makes 212 hp to the tires, so it's clear real progress has been made in the last decade. With 21 fewer cubic inches, the '05 Mustang Three-Valve engine was making at least 68 more horsepower than our mildly warmed up 302. It's even more amazing when you consider the matching improvements in fuel economy and emissions. Too bad the '05 Mustang GT doesn't weigh 3,200 pounds.

Remove Air FilterStarting with the intake, the stock panel air filter was removed and the air filter lid reinstalled. Apparently, this confused the air signal to the mass air meter, which is located in the air filter lid outlet tube, as the air/fuel ratio went rich, from 12.1 to 11.0:1. Obviously, this murdered horsepower, about 3 hp around the power peak and about 5-8 hp in the meat of the powerband.

"This is the most sensitive [mass air] meter I've ever seen," mumbled Ken, as we pondered how such a simple modification could result in a change of an entire point in air/fuel ratio. In the end, we could only conclude the panel air filter must act as a flow straightener, and taking the filter away alters airflow to the mass air. The air filter was reinstalled for the remainder of the testing.

Hydrocarbon TrapLooking inside the rubber inlet hose, between the air filter/mass air and the throttle-body, we found a hydrocarbon trap. Looking like a wadded up set of radiator fins stuffed into a tuna can, the hydrocarbon trap absorbs stray hydrocarbons when the engine is off and heat-soaked, then evaporates those hydrocarbons into the inlet air stream the next time the engine is run. All part of reducing evaporative emissions, the trap looks restrictive to airflow.

Removing the trap and re-running the engine, we got 282 hp-a gain of about 2 hp over the baseline-then a little less each of the next two pulls (we make three "official" dyno pulls and average the result for each test). The final pull netted 278 hp.

We cannot explain why power started backtracking on the second and third runs, other than to say it went slightly lean each time. Good guesses are the engine was picking up a bit of coolant temperature, or it may even have detonated ever so slightly. In any case, the engine management computer would have pulled a degree or two of ignition timing.

This is a good example of how computerized engine management can be, constantly throwing in little timing and air/fuel adjustments into a test and you really don't know about it. This makes 1-2 hp gains tough to scientifically pin down in chassis dyno testing.

In any case, removing the hydrocarbon trap certainly didn't gain a ton of power. In fact, averaging our three runs and comparing them to the baseline, removing the trap cost a hair of power until the power peak (where Ford's flat-lining the ignition timing results in a flat power peak). At the power peak, removing the "cookie" gained 1.3 or maybe 2 hp.

If anything is clear, it is the hydrocarbon trap barely hinders airflow at stock power levels. Just for the record, we've seen a 2.3 Duratec Focus engine gain almost 3 hp when removing a similar device from its inlet tract, so this test backs up that data.

Xcalibrator, no Hydrocarbon TrapLeaving the hydrocarbon trap sitting on the bench, Ken plugged in the Xcalibrator to the diagnostic port close by the steering column, under the dashboard. Because he had been working with techs from SCT the night before, the Xcalibrator already had Ken's quick and dirty hot-rod program installed in it. Most importantly, Ford has the stock ignition timing "clipped" (not advancing), starting at 5,100 rpm, so Ken's program took care of that with more timing up high. Clearly that was going to make power at elevated rpm, plus whatever it could do below the peak, with more aggressive air/fuel ratio and timing.

There was no ambiguity with the Xcalibrator, the engine liked it from the get-go. Down at 2,500 rpm the torque was up 8 lb-ft and horsepower up 4. The power peak moved upward 300 rpm, from 5,200 to 5,500 rpm, which always nets more horsepower. At 5,500 rpm, the Xcalibrator combination was 11.5 hp ahead at 287.5 hp-comparing power peak to power peak, the gain was almost 8 hp.

Ken would like to see if he could gain more power all the way across the tach with more Xcalibrator tuning, but he certainly didn't have the time to invest in such tuning during our visit, and chances are he won't. The Xcalibrator's purpose at Kenne Bell is to provide the necessary electronic tuning to support KB's superchargers, so that's where Ken will spend his Xcalibrator time on the '05 Mustang.

Xcalibrator, with Hydrocarbon TrapTaking another look at the hydrocarbon trap, we reinstalled the unusual hockey puck in the inlet hose and ran it with the Xcalibrator still set to its hot-rod program. The result was a loss of 1.5 to 2 hp. Near the power peak, at 5,500 rpm, the loss was 2.3 hp, hardly enough to worry about when schlepping around on the street.

It would seem that pulling the hydrocarbon trap might be smart on test and tune night or other special occasions, but we don't see a compelling reason to remove it for general driving. Besides constituting illegal tampering with an emission control device, removing the trap doesn't gain enough power to feel or make a difference, unless someone is keeping track with electronic timers.

After-Cat Exhaust RemovedOur next move was under the car, to see what horsepower might be lurking in the after-cat portion of the exhaust. Going into it, we didn't figure it was much, as the '05 comes stock with decent-looking cast-iron manifolds, and a 2.5-inch, stainless steel exhaust from them all the way to the tailpipes. Fitted with two catalytic converters and an H-pipe crossover, the system shows few restrictive bends. Clearly, it's an improvement over the 211/44-inch system on '04 and earlier Mustangs.

The '05 system also sports some nice-looking clamps holding together a non-crush mate between the H-pipe and after-cat, so two 15mm nuts later, the after-cat was slid off the H-pipe and we were testing. At about three minutes, it was absolutely the fastest exhaust disconnection we've seen.

We're glad we didn't have to invest much time in unhooking the exhaust as it only gained power starting at 4,500 rpm, and then it was just a hair. By the power peak, the gain was 2 hp. Hardly momentous.

So, there's not much power in mufflers and tailpipes according to Kenne Bell's dyno, but the kids will all buy noisy mufflers anyway.

For the record, we were surprised how mellow and quiet the exhaust was with the mufflers disconnected. Oh, it's plenty unsociable, but not as loud as expected. It would seem the mufflers don't have that large a job on the new car, and that may be because the cats are working harder than before.

OctaneOur final test was to try different fuels by pumping out what was left of the 91-octane, then trying regular 87-octane, followed by 104-octane unleaded racing gas. There's definitely power in moving from 87- to 91-octane as the engine management follows the knock sensor. At 2,500 rpm the gain is 2.7 hp, at 4,500 rpm we saw the largest "octane gain," a healthy 5.7 hp and 7.5 lb-ft jump, followed by a slight tapering in the gain. At 6,000 rpm, the difference was 2.7 hp, still in the 91-octane's favor. No doubt the '05 engine management/knock sensor is tuned to allow more ignition timing (increased octane cannot raise power by itself unless the engine had been detonating on lower-octane fuel). Furthermore, we suspected the happy gains would not continue past 93-octane, and might not gain past 91-octane for that matter.

Testing that theory with the 104-octane, we not only didn't see a gain, the 104-octane run looked curiously like the 87-octane run from a power standpoint, a definite drop from 91-octane. Several factors could have been at play here, including a slower burn rate for the high-octane stuff, and thus a slight power loss. Or, something in the electronics may have thought the knock sensors had gone tango uniform, so the timing was pulled to a safe default setting. Only time and much more testing will tell.

What we do know is, for those running Kenne Bell's version of the Xcalibrator, the octane gain absolutely stoppped at 91-octane, as the timing tables remain constant from that point up.

ConclusionWe came away from this get-acquainted-'05-Mustang-tuning-session with a few ideas. While much more testing is needed to corroborate these preliminary findings, it seems:*Ignition timing flat-lines at 5,100 rpm and electronic tuning is required to get around it.*The power peak is 5,300 rpm.*Burning premium fuel is the easiest way of gaining 3-5 hp.*More than 93-octane fuel is useful only at the track as detonation insurance.*There's still meaningful power in stepping up the ignition timing with electronic tuning.*The air filter/mass air meter is a sensitive area-running without the air filter is a worse idea than normal, due to turbulence in the air box.*There can't be much power to be gained in the after-cat exhaust.*More testing is needed on more cars and dynos before hard and fast rules can be set.*With electronic aid, and a few hardware tricks, 300 hp to the rear tires is not unthinkable. *Forced induction is the most straightforward path to meaningful power increases.

Mustangs have come a long way since the landmark 5.0 HO days. Only the increased weight of the new Mustang keeps it from surging far ahead of earlier cars. More so than ever, savvy tuners will rely on weight reduction, along with increased power, to achieve big gains.

Kenne Bell's '05 Mustang PlansLike the rest of the aftermarket, Jim Bell is excited by the new Mustang. Powerful and refined, it appeals to a much wider audience than the previous cars.

Jim is even more excited about what his supercharger kit will do for the '05 Three-Valve engine. Recent work with '04 and earlier GTs has shown the Two-Valve engine is capable of tremendous power when supercharged, and Jim figures the Three-Valve will be that much better. He's predicting his screw-blower kit will retail for $5,000 and make 400 hp at the rear tires, with 9 pounds of boost. That's plenty more than a stock '03-'04 Cobra, so we can see where there would be a demand for it. And, as Jim points out, with no SVT Lightning and the SVT Cobra at least a year away, there will be no other outlet for big-power, late-model Ford fans. Rumors that the new Cobra will continue with the less-expensive, less-efficient Roots supercharger also bode well for Kenne Bell, which has done well swapping its twin-screw blower for the factory units.

Look for the Kenne Bell '05 Mustang supercharger kit by the time you read this. Expect it to be charge cooled-Kenne Bell is going for boost on this one-and also look for a 4.6/5.4 version of the same kit (same manifold/adapter casting) for F-150s not much later. The usual modular V-8 caveats concerning weak pistons, so-so connecting rods, and now, aluminum blocks still apply.

On the Dyno
  Baseline, 91-octane No Air Filter, 91-octane No Hydrocarbon Trap, 91-octane Xcalibrator, No Hydrocarbon Trap, 91-octane Xcalibrator, Hydrocarbon Trap, 91-octane No After-Cat, Xcalibrator, 91-octane Xcalibrator, 87-octane Xcalibrator, 104-Octane
RPM POWER TORQUE POWER TORQUE POWER TORQUE POWER TORQUE POWER TORQUE POWER TORQUE POWER TORQUE POWER TORQUE
2,{{{200}}} 101.00 241.11 108.44 258.89 106.03 253.11 113.47 270.89 108.65 259.34 112.84 269.38 103.87 247.94 105.40 251.{{{62}}}
2,{{{300}}} 115.95 264.77 114.62 261.74 116.26 265.47 119.75 273.44 119.35 272.55 119.14 272.06 113.72 259.67 113.01 258.06
2,400 122.63 268.35 120.83 264.42 122.{{{80}}} 268.73 126.30 276.40 125.66 274.99 125.42 274.46 120.33 263.32 118.32 258.94
2,500 127.29 267.42 123.64 259.75 126.98 266.76 131.44 276.14 131.16 275.54 130.40 273.95 124.61 261.79 124.26 261.05
2,{{{600}}} 132.72 268.09 128.50 259.{{{57}}} 132.54 267.74 135.89 274.51 135.49 273.70 135.39 273.50 129.80 262.21 128.66 259.89
2,700 139.11 270.60 135.29 263.17 139.07 270.51 141.88 275.98 141.61 275.45 141.35 274.95 136.03 264.61 134.{{{90}}} 262.42
2,800 146.09 274.02 141.62 265.65 144.76 271.54 148.28 278.15 148.15 277.89 147.75 277.14 143.19 268.58 141.67 265.74
2,{{{900}}} 150.80 273.11 144.98 262.57 149.97 271.62 153.09 277.26 152.96 277.02 152.14 275.54 147.52 267.17 146.48 265.29
3,000 154.88 271.15 149.90 262.44 154.63 270.72 157.58 275.89 157.14 275.11 156.62 274.20 152.34 266.70 151.30 264.88
3,{{{100}}} 159.70 270.57 153.90 260.75 159.26 269.83 162.49 275.30 161.95 274.37 161.42 273.48 157.22 266.37 155.76 263.89
3,200 165.77 272.08 162.08 266.03 {{{164}}}.09 269.31 168.01 275.76 167.71 275.26 166.51 273.29 162.57 266.83 161.10 264.42
3,300 172.77 274.97 167.72 266.93 171.49 272.93 174.39 277.54 173.80 276.60 173.59 276.28 169.02 268.99 167.33 266.31
3,400 180.92 279.48 173.06 267.34 179.56 277.37 182.51 281.93 182.05 281.22 182.57 282.02 176.71 272.97 174.13 268.98
3,500 190.31 285.57 182.16 273.34 188.93 283.51 191.80 287.80 191.19 286.90 191.32 287.09 186.13 279.30 183.73 275.70
3,600 199.05 290.40 189.85 276.97 197.77 288.54 201.15 293.46 200.25 292.15 200.56 292.60 195.30 284.93 193.10 281.72
3,700 204.98 290.96 197.49 280.34 203.50 288.86 207.62 294.72 207.55 294.61 206.86 293.64 201.79 286.44 201.21 285.62
3,800 212.23 293.33 203.18 280.82 209.77 289.94 214.11 295.92 213.27 294.76 213.62 295.25 207.77 287.17 207.14 286.30
3,900 220.34 296.73 211.85 285.30 216.67 291.79 221.96 298.91 221.69 298.55 221.62 298.45 214.39 288.72 213.69 287.77
4,000 226.84 297.85 218.62 287.05 223.08 292.91 229.75 301.66 229.48 301.31 229.27 301.04 221.14 290.36 220.49 289.52
4,100 233.79 299.48 26.98 290.76 229.46 293.94 237.35 304.05 236.38 302.80 236.21 302.59 227.50 291.43 226.54 290.21
4,200 {{{240}}}.58 300.85 34.90 293.75 235.22 294.15 245.07 306.46 244.29 305.49 244.71 306.01 233.98 292.60 232.90 291.24
4,300 246.11 300.60 43.35 297.24 242.26 295.90 251.98 307.78 250.73 306.25 251.43 307.10 239.48 292.51 238.93 291.83
4,400 252.55 301.46 246.22 293.91 245.17 292.65 257.31 307.15 256.04 305.62 256.99 306.76 246.57 294.33 244.91 292.34
4,500 255.69 298.43 250.63 292.52 251.08 293.04 260.85 304.45 259.30 302.64 260.74 304.32 251.40 293.42 251.97 294.09
4,600 259.57 296.37 254.19 290.23 254.08 290.11 264.17 301.62 263.09 300.39 264.09 301.53 256.93 293.35 253.93 289.92
4,700 263.32 294.25 258.19 288.52 256.73 286.89 267.66 299.11 266.51 297.81 266.90 298.25 259.40 289.87 257.88 288.18
4,800 268.48 293.76 263.14 287.93 262.17 286.87 271.12 296.66 269.33 294.70 271.38 296.94 263.26 288.06 263.32 288.13
4,900 272.53 292.12 267.91 287.16 265.93 285.04 277.76 297.72 275.59 295.40 276.66 296.54 268.56 287.85 266.77 285.94
5,000 276.03 289.95 271.97 285.68 268.51 282.06 281.30 295.49 279.59 293.69 281.39 295.59 272.28 286.01 270.13 283.75
5,100 278.55 286.86 274.29 282.47 271.86 279.96 284.39 292.87 283.00 291.44 284.19 292.67 275.85 284.08 273.79 281.95
5,200 279.78 282.58 274.97 277.73 274.37 277.12 286.06 288.93 284.59 287.45 285.91 288.78 276.32 279.10 275.75 278.51
5,300 278.31 275.80 276.61 274.11 276.20 273.70 287.44 284.84 285.20 282.63 286.62 284.03 277.32 274.82 276.16 273.67
5,400 277.13 269.55 275.36 267.82 275.21 267.67 287.50 279.63 285.46 277.64 287.13 279.26 276.93 269.34 276.44 268.87
5,500 276.04 263.60 273.06 260.76 275.88 263.45 287.54 274.58 285.23 272.38 286.88 273.95 275.98 263.54 275.70 263.28
5,600 276.05 258.90 271.76 254.88 276.57 259.38 286.72 268.91 284.86 267.17 286.48 268.69 275.91 258.78 275.07 257.99
5,700 275.70 254.04 271.63 250.28 277.58 255.77 286.01 263.53 284.67 262.30 286.51 264.00 275.00 253.39 273.69 252.19
5,800 275.97 249.90 268.77 243.38 277.41 251.21 285.29 258.35 284.98 258.06 286.05 259.03 274.05 248.17 273.38 247.55
5,900 275.33 245.09 269.43 239.84 276.52 246.16 284.89 253.61 283.47 252.35 285.73 254.35 272.16 242.28 272.56 242.63
6,000 274.33 240.13 265.79 232.66 273.53 239.44 284.02 248.62 283.33 248.02 285.45 249.87 271.61 237.76 271.20 237.39
6,100 273.02 235.07 n/a n/a 272.92 234.99 284.66 245.10 282.28 243.04 285.43 245.76 271.29 233.58 271.25 233.55