Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!wuarchive!brutus.cs.uiuc.edu!apple!uokmax!occrsh!att!cbnews!military From: steve@ncsc.navy.mil (Mahan) Newsgroups: sci.military Subject: Fuel Injection Message-ID: <11268@cbnews.ATT.COM> Date: 9 Nov 89 15:29:21 GMT Sender: military@cbnews.ATT.COM Lines: 35 Approved: military@att.att.com From: steve@ncsc.navy.mil (Mahan) Subj: Fuel injection systems In issue 28 in the discussion of fuel injection it was stated that the fuel is injected directly into the engine cylinder. In general this is true only for Diesel engines. Most gasoline powered engines that use fuel injection place the injectors somewhere outside the cylinders in the intake air stream, either in the place of a conventional carburetor (throttle body injection) with the injectors feeding the cylinders through a common manifold or in the intake ports of each cylinder. Injectors in the intake ports may be set up to spray fuel constantly or to provide pulses of fuel synchronized with the operation of the intake valve. The only gasoline engine that I am aware of that used direct cylinder injection (other than racing engines) was the Mercedes-Benz 300 SL. This passenger car engine had a 3 liter displacement and produced 154 HP from 6 cylinders in 1954. The reasons for using direct cylinder injection in a gasoline engine involve better cylinder filling due to the cooling effect of the injected fuel charge on the air in the cylinder. This tends to increase the cylinder vacuum and further accelerate the air in the intake port and runner, providing better cylinder filling and consequent increased power. The main disadvantage of this system is the need to provide a high pressure (3000 psi) Diesel type injection system capable of pumping gasoline (2-3,000 1989 dollars). Most Diesel injection pumps rely on the fuel for lubrication and the modifications to deal with gasoline and its poor lubricating properties are expensive. Stephen Mahan Naval Coastal Systems Center Panama City, FL 32408-5000 ARPA: steve@ncsc.navy.mil Standard Disclaimer included free of charge with this message.