Cycle News - Archive Issues - 1980's

Ferracci ran large diameter plastic ducts from holes in the f airi ng t o the airbox, supplying the engine with ample amounts of cool, dense air. Cool air, ducted f rom the front of the fairing , slightly pressurizes the airbox at high speeds. Ferracci has complained of high-speed leanness. Th ree- ri n g p istons are classic 1970s technology. Aftermarketlooking connecting rod is stock. The Ducati 851 features a much bigger dry clu tch than seen on previous Ducatis . The sharp bends around the cross in the exhaust system have been cut open and rewelded, making a less tortured path for the exhaust gases. This neat chromemoly tai lpiece replaces the much heavier stock subframe. • Ferracci also cut and rewelded each of the header pipes to give a softer rad ius to the bends. 26 accurate). Timed, rather than th e more efficient continuous injection, is used. At redline, the injectors are turning on and off over 80 times per second (as opposed to the Bosch Continuous Injection System, which would simply vary the flow rate). To make the system work , two injectors a re used per cylinder. To co m pe nsa te for the abs ence of ' an air£Iow sensor (and th e £Iexibility one provides), Bimo ta (who also uses this system ) goes to each tra ck with a computer to -reprogram the fuel injection chips to suit each tra ck 's' conditions. T hat is not an indication of how clever Bimo ta is, but rather how poor the Weber is. Simply put, th ese EPROMS (Erasable ' Program able Read O n ly Memory Chips ) control the amount of i~nition advance as well as the duration and timing of the injector's spray. There are a handfu l of different chips avai lable with slightl y different " maps," which cost less than a buck apiece to produce. Additionally, the equipment to reprogram th em is not that expe ns ive. With no airflow meter, no oxygen sensor in th e exha ust (to tell how com p le te th e combustion is), and no kn ock sensor to read detonation and tell th e system to retard th e timing, the bike has to run conservative settings to be sa fe. Most bikes run th e lea nes t mix ture and m ost adva nce possibl e without detona tion (overhea ti ng). An indication th at Ferracci is not running o n th e lean and neat edg e of detona tion is that even with th e s toc k elec tric fan rem oved , th e bike is still running 60 to 70-d egree ce n tigrade (140- 158 fahrenheit) water temperatures. This in sp ite of the fact that th e radiator ha s a hi gh-pressure cap on it, meaning th at the boys on th e drawing tabl es figured that the temperature sho uld run over 1000 C (2120 F). All of the 851s have an air density meter, so at least in theory they should all have a close-to-correct mixture. J udging by the color of the inside of the exhaust pipes o f th e various 851s on the track at the Nationals, most are ru nning about right. O n acceleration none were heard to bog heavily or sound flat. And none of the 851s complained of detonation or overheating, signs of lean running or excessive advance. Ferracci 's air scoops are probably slightly pressurizing the airbox at high speeds. He ha s co m pla ined of high speed leanness (whe n the most air is being forced in). Movin~ the air density meter into the airbox might help, but an injection system u tilizing an air£Iow sensor (like the BMW K bikes) is the rea l answer. The reali ty of the situation is that the injection system's great advan tage is that it uses injectors. With fuel being spritzed out on command rather than being sucked up as a reaction to increased air£Iow (as in a carb ), a large throttle body can be used for good top end power and still be able to atomize fuel well at small throttle openings. Given the limitations of this system, it's doubtful that a change in ch ips could account for much of an increase in horsepower unless the original injec tion /ignition maps wer e ver y inaccurate (which does not seem to be the case). Will the real Superhero please takeoff his disguise? The answer is th at th ere are many answers. Ducati designed a nice engine. Eraldo Ferracci is an excellent tuner and knows whose ad vice to follow. A lighter weight bike with 'less rotating mass to accelerate is faster than a heavy one with a lot of £Iywheel effect. Engines like large quantities of cool, dense air better than restricted a mounts of thi n air. Motorcycles with SO/50 weight distri bution handle better than ones wi th a heavy rear end. An exhaust system without sharp bends works better than one with sharp bends. And last but not least, Da le Q uarterley is a very good rider. For those who still suspect Ferracci has a secre t, here are some p ho tos to put your mind at ease. . . •

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