![]() An engine wastes increasing amounts of air past peak power, so a slightly larger carb might be a benefit in a pure race engine. However, since we now know this engine has an 85 percent VE slightly below redline, we could use it to determine carb cfm rating using the standard cfm formula:Ī 750 cfm carb would be the smallest and generally most responsive that meets the horsepower peak airflow requirements. This number isn’t helpful in the carb cfm calculator, but is a good measure of performance. Note that the engine peaked at 92 percent VE between 5,500 and 5,800 rpm-after peak torque began to fall. We know it makes 592 horsepower and we know it makes it at 6,700 rpm.įormula to estimate VE at different rpm from an engine’s dyno curve: The example in the graph below is a naturally aspirated 440 cubic-inch engine. VE is based on an engine’s horsepower dyno curve. How Volumetric Efficiency Relates to Your Engine’s Dyno Curve This table is influenced by the engine displacement, camshaft, head design, exhaust, and air filter. *Slightly Modified = performance cam, ported stock cylinder heads, performance intake manifold, headers, ignition upgrade **Highly Modified = aggressive cam, performance intake manifold, headers, ignition upgrade, aftermarket configuration racing cylinder heads, 14:1 or higher compression ratio VE or Volumetric Efficiency is a measurement in percentage of efficiency that an engine can move the air/fuel into and out of the cylinder at various rpm and throttle positions (or manifold absolute pressure, MAP). The chart below gives some general VE ratings for different types of engines: When the fuel and ignition systems are properly tuned, this can raise VE over 100 percent and make tons of power. These power adders force more air into the cylinder. Pumping more air is also the idea behind superchargers, turbos, and nitrous. This is the idea behind aftermarket intake manifolds, cold air kits, porting and polishing cylinder heads, and headers. You can improve VE by making it easier for air to flow. The same engine would operate at a higher VE at sea level than in the mountains. This means that there are more air molecules inside the cylinder. Therefore, VE can change based on the environment.Īt sea level, the air is more dense. Air density changes with temperature and altitude. Volumetric efficiency can be a tricky topic. How Does Volumetric Efficiency Affect Performance? This can be difficult to measure and requires special testing equipment. This is NOT the CFM rating of the carburetor. In this formula, CFM is the amount of air (in cubic feet-per-minute) being pumped through the engine. The Formula for Volumetric Efficiency Is: The heavier it is, the more air/fuel it contains that can be burned to make power. Inertial tuning of the intake, heads, cam, and exhaust can make the volume heavier. Volume always measures the same, but restrictions lighten the mass of air/fuel compared to what a cylinder theoretically holds. An engine operating at 100 percent VE means we’ve trapped 100 percent of the air a cylinder can theoretically hold by mass. Basically, it is a measure of how full the cylinders are. Volumetric efficiency (VE) is the actual amount of air flowing through an engine, compared to its theoretical maximum. In this post, we’ll discuss volumetric efficiency, provide the volumetric efficiency formula, and show some examples of how it applies to specific engine examples. However, surprisingly few people understand what volumetric efficiency is and how it actually affects engine performance. great piece.Volumetric efficiency is a term that’s tossed around quite a bit when talking about internal combustion engines. over 400 WTQ and IIRC like 450+ WHPĪll 3 cars also had APS FMICs but the other 2 had the 525 while I have the 725. But after meth and EWG I heard all went real well. I dont remeber what numbers he ended upwith but his boost was only slightly to the right on the graph but he had more TQ but less HP because he could not hold boost well. The car with the blouche went EWG and METH when he couldnt get his IWG to work well. I have redlined 6th w/ EGTs of only 1600 And unlike a 20G my HP is still rising at red line, there is a good bit left in this turbo, you can just feel it.Ĭar 1 tuned boost up to 22 lbs made like 420 WHP. hill agile told me that even at my boost level I have 15 wheel on the table. I get a little spike when boost hits but I am tuned to about 19.5 lbs of boost. On the stree I have logged 20 lbs at 3900 in 2nd gear and and 20 lbs in 5th and 6th. I have watched a few blouche dynos coe out with practialy identicle dyno grAPHS ON THE SAME DYNO. I can say that I have been in alot of modded STIs and I think I have as much or more area under the curv on 93 then any other car I have been in.
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