| efficiency excerpt taken from here short story - Seb's car has motor work ie: cams / head work / larger valves that will increase the VE closer to 100% than stock which will allow more RWHP at lower boost levels - as Greg has stated in previous posts
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VOLUMETRIC EFFICIENCY
Imagine that you have a 100 cubic inch single cylinder engine. On the intake stroke, the piston moves to the bottom of the cylinder and creates a volume that is 100 cubic inches. The fuel/air mixture that fills this volume is what will be used to create the power.
Now imagine that this engine has some type of restricted intake, such as a small carburetor or restrictor plate like they use in NASCAR. With this configuration, the intake manifold has a fairly good vacuum. In this case, even though the piston pulls a volume of 100 cubic inches into the cylinder, it is not atmospheric air. Here, you have the 100 cubic inches of the vacuum from the manifold. You can think of this as the opposite of super charging because the cylinder ended up with less fuel and air molecules rather than having more fuel/air packed into the same volume. Volumetric efficiency (VE) is used to describe the amount of fuel/air in the cylinder in relation to regular atmospheric air. If the cylinder is filled with fuel/air at atmospheric pressure, then the engine is said to have 100% volumetric efficiency. On the other hand, super chargers and turbo chargers increase the pressure entering the cylinder, giving the engine a volumetric efficiency greater than 100%. However, if the cylinder is pulling in a vacuum, then the engine has less than 100% volumetric efficiency. Normally aspirated engines typically run anywhere between 80% and 100% VE. So now, when you read that a certain manifold and cam combination tested out to have a 95% VE, you will know that the higher the number, the more power the engine can produce. Basically, volumetric efficiency is effected by your carb, intake manifold, headers, and cam specs. All of these items effect how much fuel/air will flow into the cylinder. But remember, the more fuel/air that gets into the cylinder, the more power the engine will produce. This is where software programs such as Engine Analyzer, and Engine Analyzer Pro can be a big advantage. All of these programs calculate volumetric efficiency for different engine configurations that you enter into the software. This allows you to do your own testing without having to buy the parts until you get the right combination. "
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" .. going back and forth with you on a stupid point is like watching a retarded kid double dribble in basketball, you get tired of calling foul all day" ... Slowninja(GT28RS Inconel Z) on October 03, 2005 at 8:43 AM "the only chips you know about are Doritos. =)" ...ZEngineer on June 11, 2005 at 4:23 PM "....These posts only serve to make you look even worse, its gotten so bad it even makes me look bad to reply to you...." maglito on January 22, 2005 at 3:11 AM "What, are you afraid that only a couple of good ones have rolled off the production lines and the rest are crap?? ... Its mechanics not the stockmarket." ... ZisLuv on May 03, 2004 at 6:12 PM Z32 Power.Com Dyno Z Post 1 Z Post 2 My Project Z View Me! |
