Tom Wilson
August 1, 2005

Complex. Now there's a word to keep in mind when tuning an '05 Mustang. With more mechanical gizmos and electronic tricks than any previous Mustangs, the '05 calls for a new level of tuning sophistication. We've touched on this before, but it was driven home when we returned to Kenne Bell to see how its '05 Mustang GT blower kit was coming along.

Turns out, the Kenne Bell kit was almost ready for production during our visit, and its development provides a fascinating insight into those '05 GT complexities as well as the power to come from supercharging.

The Complex Horse
Let's start by reviewing the new Mustang's Three-Valve engine. It's lightly built using the Mach 1's aluminum block, powdered metal rods, and hypereutectic pistons, so its ability to withstand killer boost, and especially detonation, is still up in the air. On the other hand, its Three-Valve cylinder heads breathe nearly as well as Four-Valve Cobra heads, so its power potential is excellent. Furthermore, the new engine introduced significant new technology to Mustangs, namely an electronic throttle and adjustable cam timing. Finally, Charge Motion Runner Controls are employed to boost low-end torque, along with a new, faster, powerfully sophisticated Spanish Oak engine management.

Put together, these new technologies mean the '05 GT engine is much more integrated than before-change one thing and everything else falls to pieces. That, and as we saw when testing this same car a few months ago at Kenne Bell's, Ford didn't leave easy horsepower on the table. "These aren't the good old days anymore," is how Ken Christley, Kenne Bell's overworked in-house electronic tech puts it.

No kidding. Ken went on to explain how the all-seeing Spanish Oak computer is both a speed density unit and a mass air system. It employs both strategies, and uses one to check the other. In fact, with the electronic throttle, Spanish Oak has more secret police than the Soviet Union dreamed of. Getting it to accept a supercharger has been a mean feat.

In prototype form, the Kenne Bell '05 GT blower kit is a bundle of test wires and temperature probes. But with the supercharger on top where it can be seen, plus the big air-inlet hose, the production kit promises to give a late-model look to match its umph. It certainly won't be this "wiry."

For example, while others we've spoken to said they had no issues with moving the mass air meter from its perch in the air filter box lid, Ken says when he moved it, the engine threw a fit. It's one of the touchiest mass air meters he's seen, and Ken has hot rodded more than his share.

The '05 engine is super sensitive to ignition timing, too. With the blower, Ken says his timing tests have shown the Three-Valve engine picks up 8 hp per degree of ignition timing advance-roughly double what other Ford V-8s yield. This sensitivity requires finesse when the computer decides to pull timing due to rising temperatures, for example.

Of course, there is good news. The new engine is fitted with knock sensors, and they are great. Ford has tuned the knock sensors so well to the stock engine that the Spanish Oak is actually programmed with premium fuel ignition and fuel tables, but the car is sold as a regular-gasoline car. That means, with regular fuel, Ford is relying on the knock sensors to constantly maintain timing because the computer is trying to run aggressive, premium-fuel spark tables all the time.

Length is the only difference between the 1.7L and 2.4L Kenne Bell superchargers. This pair is shown minus their drive sections and inlet tubes, and each has been polished, an extra-cost option. A spacer allows KB to mate the 1.7L blower where the 2.4 blower was designed to fit.

Kenne Bell's Kit
To develop its '05 GT kit, Kenne Bell is "working backward," as Ken puts it. Typically, KB starts with its entry-level, non-intercooled, small 1.7L supercharger, then once that system is set, it adds hardware and sometimes larger blowers to arrive at higher boost, intercooled kits. This time, Kenne Bell principle Jim Bell decided to start with the larger 2.4L supercharger, intercooler, and whatever large mass air meter, cold air kit, and so on the engine needed to reach its highest power goals (KB is talking 800 hp, folks), then simplify the kit as possible when the boost was lowered, ultimately to the entry level of approximately 6 pounds, no intercooler, and about 430 rwhp. The result is simpler packaging that will accept either the shorter, lighter 1.7L ("417") or longer, higher-volume 2.4L ("424") Lysholm-screw superchargers Kenne Bell swears by, plus more of the good stuff will likely end up on the entry-level kits. This will make life easier for all you guys who step up to the bigger blower six months after fitting the base kit.

After testing, Kenne Bell has decided to offer a non-intercooled Standard Kit putting out 6 pounds of boost using the 1.7L supercharger, the big mass air, 42-lb/hr injectors, and cold-air kit (the 4-inch intake plumbing). All remaining kits will be intercooled and use the 2.4L blower. This schedule accommodates the many customers who want a simple, more affordable kit for daily driving and who won't make any additional upgrades, plus the ragged-edge, boost-crazy sorts. Incredibly, this means all of the intercooled kits will then be capable of 8-28 pounds of boost with little more than a pulley change. A good short-block will be needed after the first step up, however.

Buried under the supercharger in this view of the driver side is Kenne Bell's new intake manifold for the '05 Three-Valve engine. The bypass valve is at the upper right, with the reused stock fuel rail and the powerful, stock coil-on-plug ignition also visible. KB packages the intercooler immediately underneath the blower, where it can't be seen. Production blowers will be assembled at Kenne Bell to its intake manifold, with the intercooler, injectors, and so on already attached.

So, as shown here, the Kenne Bell arrangement begins with a large conical air filter inside the passenger-side fender, runs a 4-inch hose through the radiator support/inner fender to a 90mm mass air meter from the Lightning pickup, and then more 4-inch tubing to reach the stock '05 e-throttle body bolted to the cast-aluminum air intake that turns the air 180 degrees into the rear of the supercharger. The blower discharges the air downward through an intercooler, then the bottom of the Kenne Bell intake manifold turns the air 180 degrees-upward again-where it finds the individual intake runners, turns yet again, and finally flows into the cylinder heads. It sounds convoluted, but it makes plenty of power.

Note that the Charge Motion Runner Controls are deleted by Kenne Bell as generous torque is available at any rpm, and these auxiliary throttles are restrictive at the higher airflow levels the supercharger provides.

Supporting hardware includes larger 42-lb/hr fuel injectors (the stock injectors will just barely handle 6 pounds of boost), KB's Boost-A-Pump fuel pump voltage booster, a Superchips Custom Tuning Xcalibrator pre-set with Kenne Bell's blower tune, a six-rib blower drive with matching belt, and pending CARB certification (these kits will be street legal). The non-intercooled 6-pound kit will simply delete the intercooler core in the KB manifold. Cooled kits will add a small heat exchanger to the lower radiator area, an electric coolant pump, and a reservoir/fill tank in addition to the heat exchanger inside the intake manifold.

Kenne Bell has found no easy way to move large amounts of intake air into and through the tightly packaged '05 engine compartment. They settled on a large conical air filter just behind the bumper cap in the passenger-side front fender.

We're expecting the usual simple Kenne Bell installation. The stock intake manifold is removed and the Kenne Bell blower/intake combination (which comes from KB nicely assembled) bolts in its place. The drive belt requires minimal changes to the front of the engine, there are no oil-supply or -return lines to plumb or big brackets to fit. The air path from filter to mass air to throttle body will require cutting some metal out of the radiator support/inner fender as there is no stock opening large enough to accommodate the 4-inch hose. Furthermore, KB was seriously considering a molded plastic inlet pipe to replace the hose, but that decision had not been made at our deadline. KB prints finely detailed instructions, too, so this is a do-it-yourself install, if desired.

Options will be few. Everyone will get the larger mass air, big inlet tube (Cold Air Kit in KB-speak), leaving the eight-rib drive kit as the major option. Testing has shown the six-rib drive belt starts slipping around 9 pounds of boost with the 417 blower and a 2.875-inch pulley, while the 424 blower uses a 3.50-inch, six-rib pulley which gives better belt wrap and doesn't slip until well into the all-hanging-out boost range. You can let the 417 slip a little in occasional use with no apparent ill side effects, but high-boost dragstrip regulars will need to go through the multi-hundred dollar pain of swapping every pulley on the front of the engine (the blower drive belt is the front accessory drive belt as well). KB has the necessary parts in its eight-rib kit. Or you can swap to the larger blower, larger pulley combination-or buy the 9-pound kit to start with.

Finding a high-volume air inlet in the new Mustang is a good trick. This is the stock inlet area after the stock air filter box has been removed. The hole in the inner fender looks OK, but inspecting inside the fender shows there is practically no air opening to the outside world. This is why Kenne Bell has gone to the passenger side for its air inlet.

Kenne Bell offers a wide range of blower drive pulley sizes ($49 each), and changing the pulleys is a two-minute job as long as you have KB's $25 special wrench for holding the pulley. This makes changing between street and strip operation a snap, and even makes swapping pulleys a reasonable solution should only low-octane gasoline be available.

Kit pricing was set right at our deadline. The standard, non-intercooled 6-pound kit will be $4,399 and all the rest $5,499, which reflects the cost of the intercooler gear. These prices are about $600 higher than the comparable Two-Valve '04 and earlier GT kits because the '05 kits will include the 90mm mass air, the cold-air kit, and the larger supercharger (on the intercooled kits), all of which are optional on the Two-Valve kit.

The final point on the kit is the warranty. Kenne Bell will happily stand behind its kits as they are shipped, but any additional tuning by the installer voids the warranty.

Dyno Testing
Ken has run months worth of testing on the car shown here using many variations of the proposed Kenne Bell kit. All of the testing is done scientifically, with just one change at a time, and much of it is academic, such as investigating what ignition advance does to power, or varying the camshaft advance on purpose to see what effects it may have. The resulting notes, charts, graphs, and reports fill two large binders, so we can't even begin to publish it all here, but we'll mention the meaningful results and cover the typical Kenne Bell blower kit configurations in more detail as they are of practical value.

Thinking there might be some power in it, a spacer was tried between the throttle body and the blower inlet. No power resulted in the mid-400hp range, but that's why you test.

As usual with Kenne Bell, rule of thumb values were determined. We've already mentioned the incredible 8hp/degree of ignition advance. Another is a gain of 4hp/3degrees of camshaft retard, although this one requires more explanation. According to Ken, Ford's system retards the camshafts but does not allow advancing them. The range of retard is rather large, with something in the neighborhood of 40 degrees of retard available (Ford uses this much cam retard in conjunction with wide open throttle-even when the driver has commanded only a small throttle opening-at lower rpm to lower pumping losses and thus gain fuel economy). In terms of ultimate supercharged power production in the midrange rpm, retarding the cams gave these results:

Degrees RetardPower Change
3no difference
6inconsequential improvement
9-1212-16 hp gain

Ken says there is nothing to gain from cam retard at wide open throttle at high rpm as Ford is already retarding the cams 3-9 degrees at WOT, which is apparently optimal the way the cams are indexed to the crankshaft. Ken removed all cam retard at the top end, but this didn't help any. All of this cam control is done through the computer, by the way, so Ken was effecting his changes using the SCT Xcalibrator hardware and his own tuning skills.

For the prototype, Kenne Bell used this 4-inch intake hose and 90mm mass air meter. The Lightning-sourced meter will be in the production kit, but the hose is likely to be replaced by a molded plastic tube with a minimum of bends and a smooth interior finish. As always, the KB supercharger is responsive to helping its inlet side. Slight relocations of the computer and fuse box will be required; some trimming of the fender/radiator support is also required.

Preliminary temperature tests showed the supercharged '05 was definitely sensitive to intake air temperature because the ignition timing is so critical. Ford's computer pulls ignition timing in response to rising intake air temps, and with power dropping 8 hp per degree of timing around the power peak, that can mean an easy 15 hp drop when the temps go up. But Ken cautioned more testing was needed in this area before coming up with a hard and fast rule.

It looks like even the big 90mm mass air will be restrictive to airflow and runs out of bandwidth starting around 500 rwhp. A 5-inch meter is a distinct possibility from KB, as this is available from Ford's exotic 5.4 GT engine. In that case, KB will supply the meter and a switchchip for high/low power outputs on the bigger intercooled kits.

Ken had the clutch cry uncle at 535 rwhp, and it was replaced with a McLeod unit by the time we visited. Apparently, the stock '05 clutch is a fairly light-duty affair-and the entire engine with its aluminum block and light-duty rods/pistons does not bode well for high power outputs, either. Jim Bell foresees a real market for all-forged, $5,000 short-blocks for boosted '05 Mustangs. Thanks mainly to the knock sensors (which KB has retuned for blower operation-an important step), street operation up to 450 rwhp is deemed no problem by Kenne Bell. They get rather nervous at 475 rwhp, as in, "Don't even think about going over 475 rwhp," according to Ken in reference to the stock short-block. We're starting to see Jim Bell's point regarding upgraded short-blocks.

Testing also reaffirmed the relationship between ignition timing and octane: you can use an additional 1½ pounds of boost per 1 point of octane gain over 91-octane. West Coast enthusiasts are stuck with 91-octane pump gas, while lucky East Coasters get 93- and sometimes 94-octane fuel. So those Jersey boys can step up 2 pounds of boost when moving from 91 to 94 octane, which yields a significant power increase of about 30 hp at the wheels, assuming they have an intercooled kit. Expect KB to sell the same entry-level kits nationwide, and let individuals opt for a smaller blower pulley as their conditions warrant.

When it comes to tailoring a boost level, Kenne Bell has a blower pulley to suit. These are just some of the pulleys available for $49 each; and changing the easily accessed blower pulley is all that's necessary to tune for street driving, race gas, or what have you.

Low on dollars (who isn't?) and like to run at the strip? Get the less expensive non-intercooled kit and run a low 5-6 pounds of boost/big blower pulley on the street, but high-octane unleaded race gas at the track. A second pulley for 8-9 pounds of boost and that 2-minute pulley change will have you making the same power as the intercooled guys on test and tune night-unless they catch on and buy a smaller pulley and race gas, too. But then they'll be making 11 pounds of boost and need a short-block.

Boost, of course, is king, and here, we're presenting a short series of tests that represent the Kenne Bell kits (which mimic Cobra and '99-'04 GT practice)

All horsepower is rear-wheel as recorded on the Kenne Bell Dynojet. Torque is in lb-ft. The power peak is closer to 6,000 rpm, boost levels may be a tenth higher at that rpm. "CxB" is Crankshaft x Blower pulley diameters. Multiply engine rpm by the Pulley Ratio to obtain supercharger rpm. Ignition timing locked at 23 degrees. 109-octane fuel used.

All these tests were run using the larger 424 blower-the 417 blower will produce the same results, although it will take an eight-rib pulley kit and belt to match the peak power starting at just 9 pounds. Furthermore, these tests were run with the ignition timing locked at 23 degrees, which is best power. Ken locks the timing so it won't be a variable during testing, and says that typically he pulls a degree or two out in the production kits to provide the necessary anti-detonation insurance. This costs some horsepower, but is absolutely necessary insurance in the real world of bad gas, summertime heat, mechanical degradation, and so on. He ran all of his tests on 109-octane fuel to avoid detonation.

Changing Kenne Bell blower pulleys is simple using its $25 bar-type wrench for holding the pulley. It's so quick and easy that keeping your pulleys and the wrench in the trunk allows tuning for conditions immediately.

Now What?
Expect production '05 Mustang GT supercharger kits from Kenne Bell by early summer. With their torque-on-demand positive displacement design, these efficient Lysholm-screw blowers make boost from off-idle to redline, and make a smaller engine feel like a bigger one. If you are looking for a nice boost for your daily driver Mustang, and don't ever plan on racing or testing it at the dragstrip (you don't have the hot-rodding disease, really), then we recommend the non-intercooled 6-pound kit. It will definitely wake up your Mustang.

All the rest of you should opt for the larger blower and intercooler if at all possible. Once you've stepped up to the big-dollar hardware, simple pulley changes will deliver truly exciting boost levels, and your favorite engine supplier can give you the beefed short-block to hang on to the connecting rods. Kenne Bell says 30-40 percent of its customers who buy the entry-level non-intercooled kits come back within six months looking for the larger blower, intercooler, more boost, and all the rest. That's the expensive way to do it, so keep that in mind when considering the credit card limit.

Life Without Cable
We expected the '05 Mustang's electronic throttle to be a major change, and it's proving all of that. With no throttle cable, the driver-and tuner-no longer have direct control over letting air into the engine, the engine management computer-and by extension, Ford's powertrain engineers-control the throttle, and their goals are often not your goals.

Ah, our new friend, the hydrocarbon trap. The Kenne Bell kit accommodates the '05's trap to preserve emission legality, and considering that it looks like it could plug Niagara Falls, it costs surprisingly little power. At 425 rwhp, removing the hydrocarbon trap gained approximately 25 hp, and had no affect on the tune whatsoever. You'd be best to leave it in for street use, then pull it out for track day. The putty edge on this one was an attempt to improve airflow through it. It didn't make any difference. Caption22
As usual, Ken had the interior of his test car looking like the basement of the phone company with wires and computers everywhere. It takes this sort of engine management control and data acquisition to understand what is going on with something as complex as the '05 Mustang-and even then it's sometimes a mystery. 5.0

Ford is interested in producing a smooth, reasonably powerful car that will run a long time with few problems. That means no run-ins with the government over emissions and no warranty headaches. And above all, Ford has no interest in spending time with liability lawyers, and so the e-throttle is many times redundant on closing and not all that eager to open. In fact, there is a separate chip with its own programming inside the Spanish Oak engine management dedicated to watching the throttle position. Called the e-Quizzer, it is a policeman with the sole intent of closing the throttle should any parameters get out of line. Kenne Bell has found Spanish Oak even throws a purposefully erroneous signal occasionally just to see if the e-Quizzer is on the job. Amazing.

There are switches in the software that turn things like e-Quizzer off. Designed to aid diagnostic work by dealer techs, these switches are sure to be used by less scrupulous tuners who don't have the skills to add hot rod hardware correctly. Kenne Bell has used these switches in its development work, but won't go near them on production kits for liability reasons. This definitely takes longer to develop, but is part of a well-engineered kit these days. Our advice is to beware of quick and dirty electronics-and you'll find e-tuning will be required for everything from a cold-air kit on up with the new Mustang.

Such tuning is why Kenne Bell won't be offering a stand-alone cold-air kit for naturally-aspirated '05 Mustangs. To do so means not only the cold-air kit hardware, but relocating the mass air-so likely KB's 90mm mass air would be required-and electronic tuning to make it all work. That would mean a price tag three quarters of the way to $1,000, and few people are that needy for the handful of horsepower a cold-air kit will deliver. Plus, change anything else on the engine and the electronic tune could need reworking. You can see that a major improvement, such as a supercharger, while pricey, is the way to go.

PeakBoostIntercooledCxB Pulley DiametersPulley RatioRemarks
278306N/AN/AN/AN/AN/Ashowroom stock
4303845.56.2No6.5 x 4.00 1.636 lb91 octane
4784317.69.5Yes6.5 x 3.50 1.86 9 lb91 octane, short-block limit
50346210.211.7Yes6.5 x 3.25 2.0011lb94 octane
53249511.613.0Yes6.5 x 3.00 2.1713 lb94 octane, clutch limit

5.4 Anyone?
We were curious how the Kenne Bell might respond if the short-block was boosted to 5.4L. Seeing how 9 pounds of boost makes 478 hp, or 103 hp per liter, on a 4.6 Three-Valve, we plugged 5.4 into our trusty Casio to get: 103 hp/L x 5.4=561 hp, which is assuming the same 9-pounds boost and same efficiencies. Remember, these are best-possible power ratings, and in the real world will back up by 30 hp or so. Still, a relatively lightly-stressed 530 hp 5.4 would hold our attention. Can you say GT 500?

On The Dyno
StockKenne Bell, 6 psiKenne Bell, 9 psi
Kenne Bell, 11 psi
Kenne Bell, 13 psiOverall Gain

These dyno tests were conducted by Kenne Bell on its in-house Dynojet chassis dyno. They correspond to the kit information charted in the text, so all the same notes apply, such as the ignition timing locked at 23 degrees, and so on.

When plotted, you'll see these power curves follow the stock engine's power curve, but are taller. Furthermore, each 2-pound increase in boost is relatively the same jump up from the previous test, with no drop-off at the bottom or top of each curve. This is because the 417, and especially the 424 superchargers, are well within their efficiency ranges. Actually, the 424 is loafing at 9 or 11 pounds of boost-it is easily capable of 20-plus on the Three-Valve.