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.