Tom Wilson
July 1, 2008

Horse Sense: Expect all sorts o of things to work overtime when pumping 700 hp to a Mustang's rear tires. As if synchronized to last only as long as the test, Kenne Bell's prototype mule started slipping its stock clutch at the end of the Mammoth development program. A Centeforce DFX clutch installation was the cure.

Five years ago, Kenne Bell released its stunning '03 Mustang Cobra kit. With little more than swapping the stock Eaton supercharger for the Kenne Bell Twin Screw compressor and minor tweaking of the fuel and spark, the KB kit pumped the Four-Valve Terminator engine into the 620hp neighborhood.

Yes, it took more than 20 pounds of boost and race fuel to reach that much horsepower, but not much more. As amazing as it may seem, the Kenne Bell Terminator got darn near two thirds of 1,000 hp with a stock short-block and cast-iron exhaust manifolds while blowing through the stock cats.

Since then, Jim Bell, the major rotor at Kenne Bell, has introduced larger high-boost-optimized superchargers. He has also pondered his Terminator offering, looking for a way to get even more from it. The combination of Jim's power quest and specialized compressors has now been finalized. That's the kit we're looking at here.

To save you from flipping to the end of this article, the new kit takes the same stone-stock Terminator engine, cast-iron exhaust manifolds, and cats to 704 rwhp, a 101-rwhp improvement with the same pulley as the original 2.2-liter KB Terminator kit.

There's one point that we should emphasize before going any further: The original KB Terminator kit remains available for anyone satisfied with approximately 525 rwhp while running pump gas, or anyone happy with about 700 rwhp with prepped heads, hot-rod cams, and race gas. Why? The original kit is less expensive, and its 2.2-liter and 2.6-liter superchargers are slightly more efficient at lower street boost levels than the larger 2.8-liter compressor used in the new Mammoth kit. The Mammoth is for those wanting great street horsepower and the ability to quickly swap pulleys and gasoline to run hard at the track. It also offers tremendous potential to the cam and heads crowd; with the right supporting pieces, it should post 850 hp to the tires. We also caution that the extra power needs careful throttle manipulation to avoid wheelspin-which isn't such a bad thing if you know what you're doing.

With no hope of getting enough air under a stock Mustang hood to feed a Mammoth kit a full suction, nor room to package a correspondingly huge air filter, Kenne Bell turned the intake pipe down and through the sheetmetal to take air from under the driver-side front fender. The relocated stock mass air electrionics and intake air temperature senor show here as well.

Mammoth Proportions
So, what did Kenne Bell do to come up with its new Mammoth kit? The company began by understanding its 2.8H supercharger was more efficient at high boost levels (15 psi or higher), and it therefore took less power to drive than the 2.2/2.6H blower did at high boost. If that larger compressor could fit into the Terminator engine, it would free up power compared to the 2.2/2.6H blower.

The crew also realized that the inlet-the curved, aluminum intake air casting that sweeps the incoming air into the rear of the supercharger-is restrictive at high boost, even on the 2.2/2.6H supercharger. The deeper-breathing 2.8H compressor would need even more air, so a much larger, much freer-breathing intake casting was developed. Because castings in production volumes are expensive, this wasn't a casual commitment.

With no need for a separate mass air meter, the stock Cobra air meter innards were relocated to a pad on the side of the 4.5-inch tubing. That gives the Mammoth kit a 4.5-inch (114mm) mass air, if you will.

With the new inlet in place, the remainder of the intake air path proved undersized as well. The throttle body, inlet tubing, mass air meter, air filter, and the air path past the Mustang sheetmetal were undermatched to the needs of a 700hp force-fed engine. Therefore, all of those parts had to be redesigned.

Perhaps the most fundamental change was to move the inlet from the passenger side of the engine compartment to the driver side. There simply wasn't enough airflow available on the passenger side due to the air-blocking hardware. However, there was greater airflow on the driver side once the battery was removed. So Ken Christley, Kenne Bell's secret weapon and all-around engineer, relocated the battery to the passenger side, where it belonged in the first place. He put a huge oval air filter in the driver-side fender and connected it to 4.5-inch-diameter metal tubing leading to the supercharger.

We tried many ways to illustrate how huge a twin 75mm throttle body is, and this one seemed to work best. This immense billet monster is machined for Kenne Bell by a contractor to KB's specification, and it's essentially a mechnical version of the twin 75mm e-throttle KB uses on its GT 500 kit.

Since there was no way the stock twin 57mm throttle body could flow the required air volume, a giant Mammoth throttle body was developed. It's essentially a mechanical version of the throttle body Kenne Bell uses on its drive-by-wire S197 high-output kits and twin 75mm bores. For those of us who cut our teeth on "big" 70mm throttle bodies for 5.0 street cars 20 years ago, the twin 75 seems as though it's off a funny car or something.

Connecting the culvert-like 4.5-inch inlet tubing to the equally massive throttle body was done by pressing the stock rubber intake bellows off the Ford GT into Mustang duty. At its discharge end, the bellow clamps to the new aluminum intake, which bolts to the 2.8H supercharger.

Quantifying the new inlet system's airflow capabilities in cubic-feet-per-minute airflow shows just how impressive an improvement it is over the stock Cobra. Measured on KB's flow bench at 28 inches of water: Put another way, the Mammoth airflow path can flow nearly 2.5 times as much air as the stock Mustang Cobra intake. This illustrates both the huge power potential the Mammoth intake possesses (much more than 1,000 hp), as well as its low restriction on the naturally aspirated (suction) side of the supercharger.

While it may look as though the KB twin 75mm throttle body is closer to the camera than the stocker below it, they're both sitting on the same bench. KB uses a twin throttle plate because otherwise the throttle shaft bends when the throttle is snapped shut at high rpm. It takes a lot of air to bend a throttle shaft-and to make 700hp.

Bolting the supercharger onto the engine required a new mounting plate, because the slightly longer supercharger and much larger inlet casting required more firewall clearance. Ken used a two-piece mounting plate with Z-shaped registers for the job. This arrangement is considerably easier to install than the standard Terminator kit and is self-locating (registering), so it requires no more alignment than simply bolting on the lower plate, then sliding the top plate/supercharger assembly into position and installing the capscrews.

As for the name, during development of the immense intake, the word mammoth surprisingly came to mind and stuck. Thus was born the nickname and woolly mammoth caricature whittled into the identification plate recessed into the huge inlet.

System Requirements
Changes to the basic Cobra engine weren't needed to reach 704 rwhp, but at the elevated power levels for which this kit is optimized, a freer-flowing after-cat exhaust system proved necessary.

A quick glance under the prototype showed the cats and the first portion of the 3-inch Bassani after-cat system fitted during testing. The Bassani mufflers gainded 36 hp over the stockers at the mid 600hp level. Even better, it still amazes us a bolt-on Mustang can put 700hp to the tires.

The stock exhaust was run until the car reached 660 rwhp. At that point, the after-cat was unbolted and the test maximum of 704 rwhp was obtained. That's fine for track work, but obviously a good exhaust system is required on the street, so KB fitted a 3-inch Bassani aft-cat. Power was an amazing 696 rwhp, a mere 8hp drop from without mufflers or pipes.

Ignition breakdown is a typical problem at high boost, but KB achieved the 704-rwhp figure with nothing more than NGK TR6 sparkplugs gapped to 0.025 inch. This proved right at the limit for the stock ignition, however, and KB recommends its Boost-A-Spark box for 15-pound-or-higher boost applications. It won't show any more power on a dyno unless the engine is misfiring. It will clean up misfires at high boost and helps against the inevitable degradation in spark as the plugs and wires age. The BAS isn't included in the Mammoth kit, so it's an extra cost option at $229.

As for fuel, once again the excellent Cobra twin-pump fuel system proved up to the task, at least with a small current bump from KB's Boost-A-Pump, which is required and part of the Mammoth kit.

No other fuel system modifications are required up to 704 rwhp other than increased octane. Kenne Bell is aggressive on that, preferring to spend money on high-octane specialty fuels for track and dyno work to replace detonated engines. The company points out that 91-octane premium pump gas (the best pump fuel on the West Coast) is good to 565 rwhp with the Mammoth kit at 15 psi; East Coast tuners can squeeze another 30-35 hp with 94-octane pump premium fuel at 17 psi.

D'Agostino Racing's fuel upgrade kit essentials include a pair of Ford GT pumps, larger 3/8-inch plumbing, and the software and hardware required to support those parts. The kit was developed mainly by Kenne Bell to support all-out Mammoth efforts, but it's only sold through D'Agostino Racing954)583-884;

Above the mid-500-rwhp mark, KB uses race gas. The Mammoth kit was developed using MS109 gasoline, with the highest boost levels augmented by a couple of gallons of 116 octane C16 race gas. Admittedly these octanes are overkill, but it's definitely the smart way to go when doing development work. Some KB customers report getting away with nail-biting stunts such as 650 rwhp on 94 octane, but we and KB can only caution that this is begging to pay for a new long-block. A safer octane strategy is to limit boost to 17 pounds or less on 93/94 octane. That will net 600 rwhp.

Getting back to the hardware, for power outputs in excess of 700 rwhp, the Mustang Cobra's fuel system needs considerably more help than a Kenne Bell Boost-A-Pump. See the Fuel System Upgrade sidebar for details.

Don't Get Stepped On
In the '60s, the Chrysler Hemi was known as the Elephant, and the saying was "Don't get stepped on." While mammoths and elephants are different animals, today Kenne Bell could redirect the same thoughts of over-powering thrust to its Mammoth Terminator kit.

Besides the obviously stupendous thrust of its 700hp potential, the Mammoth prototype kit we briefly sampled on the side streets around Kenne Bell's shop drove nicely and would easily serve as a daily driver. The installation was set at a 91-octane tune with 3.500-inch blower and 6.5-inch crank pulleys (565 rwhp) during our drive, so it was breathing easily. The torque-bulging power was immediate and abundant. Blower whine was muted through the long intake snorkel at full throttle, but it was still there to be enjoyed when hammering away and nonexistent at plunking around speeds. Much more power would only result in wheelspin, as we found with the 800-rwhp tune on Kenne Bell's all-out GT 500 months ago. Lazy as we are in our old age, even the street tune was impressive.

So, it boils down to if you can use the extra power the Mammoth kit delivers. For purely street-driven Cobras, we say not really. The standard kit roasts the tires hard and is even more or equally efficient at low to mid rpm. Moving to the Mammoth gives an incremental bump in power with pump gasoline, be it either West Coast 91-octane or 93/94-octane East Coast fare. With the standard kit putting out 525 rwhp on 91 octane and the Mammoth delivering 40 rwhp more on the same fuel thanks to its more-efficient-at-higher-boost blower, it's tough to justify the additional $2,300 cost if sticking with a typical 15 pounds of boost and pump gas combination. That's why Kenne Bell offers both kits.

When moving on to race gasoline and smaller pulleys, the Mammoth is a no-excuses winner. The power goes up a staggering 101-plus rwhp over the standard kit-about 220 hp over stock-so that's definitely worth the price of entry. Plus, everyone becomes power jaded, so starting with a Mammoth in street tune and eventually moving to the track is a good way of prolonging a Cobra love affair.

As its typical engine-dyno pratice, Kenne Bell employs a sophisticated, expensive air/fuel monitor for independent verification of what's really going on in the cylinders. It's one of many ways KB keeps a tight grip on te electronics, mechanicals, and even the business side of its supercharging efforts.

Ultimately, teaming a Mammoth with a cammed and ported Terminator engine seems a standout idea. The resulting power would be terrifying, and for those thinking big, a combination of a built Terminator, Mammoth blower, and fuel system upgrade kit has 1,000 hp written all over it. That's mad power built mainly from kits.

If you're ready for the Mammoth, Kenne Bell has them in stock now. Pricing is $5,750 with a satin finish, as seen in our photos, or $6,400 for a polished blower. Tuning is optional-at this level, most owners have custom tuning done locally. However, Kenne Bell offers its tune for $249.

For comparison, the standard KB kit for '03-'04 Cobras uses the smaller 2.6H compressor and is $3,349. It too is supplied without tuning, so add $249 for the KB tune. It's also recommended that the $249 Boost-A-Pump be used.

For either kit, a dual-tune Switch Chip is optional at $299, additional pulleys are available for $69, and the rapid-fire pulley-changing wrench costs $25.

Comparing the new Mammoth intake casting to the standard Cobra inlet (right) is another example of size making a difference. Obviously the Mammoth intake casting is wider-mounted and much deepeer to allow 1,500 cfm of air to make the turn into the compressor. The new intake casting is the key player in the Mammoth kit.

Finally, for those who haven't pedaled a 700hp Mustang on street tires but fancy the idea, be advised that it's a different experience than moving from 300 to 500 hp. Big-power street cars demand restraint, understanding, and occasionally real skill from the driver, and strangely enough, can be slower than the typical 400hp bolt-on Mustang in most casual street situations. The big-power car's limitation is traction, and with so much power, it's laughably easy to blow off the rear tires. At the least, this can be bothersome to work around every time you want a nice squirt of power. If you're a sporting sort, it can be embarrassing when a bolt-on car walks away from your tire-spinning power-wagon. At its worst, mega-power can mean losing control over bumps, sand, rain, or other traction stealers, so plan on being fully engaged with your car if opting for the big power figures on the street.

We won't advise you to have fun. That part comes automatically.

  Stock Mammoth
Inlet 845 1,750
Inlet, throttle body 835 1,528
Inlet, TB, filter, MAF, inlet tube 608 1,462

Fuel System Upgrade
OK, 700 rwhp is nice, but hey-you want it all. In that case, you need the fuel system upgrade developed by Kenne Bell in conjunction with and sold by D'Agostino Racing [(954) 583-8884;]. It supplies the big box of hardware and software needed to move the Terminator past 700 rwhp and into four digits.

Beginning with the nuts and bolts, the Cobra's stock fuel pumps are replaced by high-output Ford GT units. The GT fuel pumps are fitted to a stout billet "hat," or bracket, that simplifies installation considerably and provides positive O-ring sealing compared to shoehorning the GT pumps into the stock pressed-metal bracket.

In the kits, a second fuel pump driver module is added, along with supporting wiring and a relay. To drive the second FPDM, a Kenne Bell dual Boost-A-Pump is required; it's supplied in a single box with two BAPs inside.

Kenne Bell's Boost-A-Pump and Boost-A-Spark hot-rod the current to the fuel and spark systems to compensate for high boost pressures. The BAP in the Mammoth fuel upgrade kit is unique in that it's actually two BAPs in one box.

The Cobra's 5/16-inch fuel line tubing is upgraded to a 3/8-inch hose. New fuel rails are used at the engine-not because the stock rails are undersized, but because it's the easiest method of attaching the new fuel line. Larger 62-lb/hr fuel injectors, naturally, and jumper wiring harnesses are must-haves as well. On the spark side, a Boost-A-Spark box pumps up the current.

Most vexing to tuners, however, isn't getting the fuel to the engine, but handling the electronics in a realm far past where Ford ever designed the Cobra's computer to run. Simply put, when making 800-odd horsepower, there isn't any computer code to handle the necessary calculations-that, and the stock mass air meter flatlined hundreds of horsepower ago.

In the standard KB Terminator kit, the stock mass air meter flatlines around 500 rwhp. Ramping up the fuel pressure takes care of that problem up to the mid-500hp level. In the Mammoth kit, the larger intake tubing helps the air meter read more volume. The real breakthrough came when Jerry Wroblewski showed how to rig the SuperChips Custom Tuning software Kenne Bell tunes with to double the mass air range by halving its resolution. Bingo! With that tuning sleight-of-hand, the stock mass air electronics in the big intake tube could handle up to 700 rwhp. Special thanks to Jerry from Kenne Bell and the rest of us for providing a key strategy to making the Mammoth work at an affordable price.

Kenne Bell made it clear that help from Jerry Wroblewski and SCT software, as well as DiabloSport's MAFia mass air extender were necessary to provide the electronic support the fuel upgrade kit requires. The MAFia is required past 700 rwhp since the stock mass air electronics are pegged at that point, and increased fuel pressure can't be accurately accounted for by the engine computer.

The D'Agostino fuel system upgrade surpasses even that trick's usefulness, so a DiabloSport MAFia mass air extender is required to tune higher yet. Kenne Bell was just able to avoid having to fit the $150 MAFia to the Mammoth kit, but it is a must when stepping up with the fuel upgrade, so it's included.

Summing up the situation, we see the two fuel systems potentials:

Two stock Cobra fuel pumps at 119 lph (20 psi) w/BAP = 378 lph for 704 rwhp

Fuel Upgrade:
Two Ford GT fuel pumps at 212 lph (20 psi) w/BAP = 600 lph for 1,100 rwhp

Clearly the D'Agostino fuel upgrade kit quells any normal questions regarding fuel delivery. Just as clearly, it's something for high-achieving, more than 700-rwhp Cobras and isn't necessary for strictly street cars.

Kenne Bell developed the Mammoth kit in its usual time-intensive fashion of strapping the car to the in-house Dynojet, wiring it to log every imaginable temperature and pressure, locking the ignition timing to reduce variable, and then testing. Such dyno mules may spend up to four months on the roller before coming off for part-throttle driveability tuning.

On The Dyno

2,200 141.36 337.46 135.53 323.27 -5.83 -14.19 181.25 432.56 186.93 446.18 45.57 108.72
2,400 158.12 346.03 205.37 449.38 47.25 103.35 211.88 463.62 212.70 465.44 54.58 119.41
2,600 173.99 351.47 232.75 470.14 58.76 118.67 237.00 478.71 235.72 476.15 61.73 124.68
2,800 188.69 353.93 253.99 476.43 65.30 122.50 262.84 492.98 258.22 484.34 69.53 130.41
3,000 204.56 358.13 275.79 482.81 71.23 124.68 288.31 504.73 282.53 494.59 77.97 136.46
3,200 220.18 361.38 296.77 487.07 76.59 125.69 314.23 515.73 307.59 504.82 87.41 143.44
3,400 234.68 362.52 317.31 490.15 82.63 127.63 339.82 524.90 334.12 516.11 99.44 153.59
3,600 247.81 361.54 336.97 491.61 89.16 130.07 367.02 535.43 360.54 525.99 112.73 164.45
3,800 262.88 363.33 354.88 490.50 92.00 127.17 394.22 544.86 387.46 535.51 124.58 172.18
4,000 275.50 361.73 373.45 490.36 97.95 128.63 420.47 552.08 415.26 545.23 139.76 183.50
4,200 290.19 362.88 391.19 489.19 101.00 126.31 446.23 558.00 441.31 551.85 151.12 188.97
4,400 305.52 364.68 406.67 485.42 101.15 120.74 472.19 563.63 467.53 558.07 162.01 193.39
4,600 313.40 357.83 421.79 481.59 108.39 123.76 497.93 568.52 493.30 563.23 179.90 205.40
4,800 326.49 357.24 437.17 478.35 110.68 121.11 523.65 572.98 518.41 567.23 191.92 209.99
5,000 337.68 354.71 452.28 475.08 114.60 120.37 548.57 576.23 543.59 570.99 205.91 216.28
5,200 346.67 350.15 465.68 470.35 119.01 120.20 573.87 579.62 568.96 574.65 222.29 224.50
5,400 358.76 348.94 475.03 462.04 116.27 113.10 598.34 581.96 593.89 577.61 235.13 228.67
5,600 368.49 345.61 486.27 456.05 117.78 110.44 623.16 584.44 617.51 579.16 249.02 233.55
5,800 377.34 341.70 494.53 447.82 117.19 106.12 647.42 586.27 N/A N/A N/A N/A
6,000 376.11 329.23 499.85 437.55 123.74 108.32 668.08 584.81 N/A N/A N/A N/A
6,200 366.03 310.07 501.94 425.21 135.91 115.14 686.65 581.68 N/A N/A N/A N/A
6,400 367.88 301.90 500.51 410.74 132.63 108.84 694.54 569.98 N/A N/A N/A N/A
6,600 345.93 275.32 485.75 386.51 139.82 111.19 N/A N/A N/A N/A N/A N/A

Four dyno runs of interest from the Mammoth development are presented here. The first is the stone-stock Mustang Cobra; the second is the baseline Mammoth installation where the complete Mammoth kit was installed and run on 91-octane pump gas; the third run documents the Mammoth kit tuned with race gas, 20.5 pounds of boost, and the after-cat unbolted. This is the 704hp peak power run; our 200-rpm-resolution dyno charts didn't capture this peak (maddeningly so, but that's always the way it seems to go). The last test is identical to the third, but with the 3-inch Bassani aft-cat installed. All runs were made on Kenne Bell's Dynojet with SAE correction.