Page created by MRHZV8 Jan 26th 2005:
By The Pink Bitch and Oinks308
Extractors are an aftermarket exhaust manifold, which provides much better flow for escaping exhaust gasses. This allows your engine to rev more freely without the power sucking resistance of pushing out exhaust gases through a restrictive, poor flowing exhaust manifold.
Good extractors, or "tuned length" extractors, also have an additional characteristic, which earn them their name. As each cylinder's exhaust gas flows through the pipes, a positive pressure in the whole exhaust system is created.
Standard Exhaust Manifolds:In standard exhaust manifolds the gas discharges from different cylinders come down Different lengths of pipe, and so interfere with each other's flow, creating an uneven pressure variation pattern in the exhaust system. Extractors have either equal lenth pipes coming from each cylinder, or "tuned length" pipes which create the same effect at a certain rev range - that is, the exhaust gas discharges overlap each other, as the enter the main exhaust pipe, in the same timing configuration as the exhaust valve timing. this leads to a smooth exhaust flow with relatively constant pressure.
Extractors and Rev Range:
Most extractors have an optimum rev range at which they assist exhaust flow more than at any other. Usually this "kicks in" at about 2000 rpm. Within this range, the flow characteristics of the Extractors, utilising the momentum or inertia of the flowing gas, actually assist in "sucking" exhaust gases OUT of the cylinders which are on the exhaust stroke at any given time.
Most Extractors manufacturers claim a performance improvement of up to 10% - 15% from the fitting of extractors. They can also mildly improve Fuel Economy (if you can resist the urge to plant the go - pedal to the metal to hear the lovely new note of your engine.)
Different types of Extractors:
V8: The Tri-Y type of extractor offers better low down torque, drivability and economy where as the 4 into 1's are more designed for all out high rpm performance.
Tri-Y Pipes will go 2 into 1, then those 2 into 1 to the collector.