High-performance engine designers are masters at squeezing startling amounts of horsepower out of normally docile power plants. For example: power ratings of 130 to 140 horsepower per 1000 cc of engine displacement (normally aspirated) are not uncommon. The impressive horsepower numbers produced by these highly tuned engines are the product of high engine speeds.

Revolutions in excess of 10,000 per minute are common, working together with big carburetors and wild valve timing to stuff lots of fuel into the cylinders. However, there is a price to pay for startling high-rpm performance: power output can be uninspiring at low to medium engine speeds and idling very rough. The dynamometer chart for one of these highly tuned engines will typically show a torque curve with a big dip on its way up to maximum output. The dip is caused by unruly pressure pulses that occur in the engine's exhaust system. Thus the exhaust system is host to positive and negative pressure waves that vary with engine speed.

Nology Engineering, Inc. has tamed these pressure waves by putting a movable "throttle" in the exhaust system. The SHOTGUN T.R.EX. (Totally Regulated Exhaust) is continuously adjusting to the ever changing exhaust pressure waves. The result is: stellar high-rpm performance and much improved power at lower engine speeds. The Nology system consists of a spring loaded butterfly valve installed in the exhaust system. As engine speeds and load conditions change, so do pressure waves in the exhaust system. The T.R.EX "reads" these pressure waves and adjusts accordingly. High-performance engines are usually designed with lots of valve overlap, the period during which both valves, intake and exhaust, are open. This is when pressure waves can help or hinder performance; they typically do both. Negative pressure waves work like a vacuum cleaner during valve overlap, sucking exhaust gas from the combustion chamber and helping to draw in a fresh fuel/air mixture. The rpm range where negative pressure is present will be marked by an upturn in the torque curve. Inversely, positive pressure in the exhaust system tends to push exhaust gases back into the engine, pushing the incoming fuel mixture back into the carburetors; this rpm range will be marked by a fall-off in the torque curve. Engineers can tailor the length of the exhaust pipe so that a negative pressure wave is present at high rpm for good maximum power, but this shifts the positive pressure wave lower in the engine-speed range where it manifests itself as soggy performance. Furthermore, highly tuned engines, equipped with radical cams and free-flowing exhaust, can suffer from low-end performance caused by too little exhaust back-pressure. This situation allows some of the incoming fuel/air charge to leave the cylinder with the exhaust. Until now these limitations have forced engineers to seek the best compromise between top performance and low-end drivability. However, Nology's SHOTGUN supplies just the right amount of back-pressure to assure that the incoming air/fuel charge stays in the cylinder, assuring maximum horsepower.

Furthermore, the totally regulated exhaust constantly adjusts exhaust flow to always maintain a negative pressure wave in the exhaust system, at any rpm. A similar system has been used for years, very successfully, on Yamaha's top sportbikes, Ferrari's F50 supercar, BMW's high performance 328 and on Drew Marine's high performance off-shore boats.

Nology engineers found a substantial low to mid-range torque gain when installing T.R.EX. Idle stability is also greatly improved, and hydrocarbon emissions at idle are lowered, due to the elimination of "blow-back" of unburned fuel into the carburetors. Blow-back creates a doubly rich fuel mixture by forcing the same air to travel backward and forward through the carburetors, where it picks up fuel in both directions. Finally, engine noise at idle and low rpm is reduced dramatically, when the valve almost completely blocks the exhaust pipe.

Nology's SHOTGUN T.R.EX makes it possible for engines to produce staggering high-rpm horsepower and also be a strong low and mid-range performer. The SHOTGUN T.R.EX can be used on engines of any size and is an easy bolt-on installation. Available for motorcycles and cars.