It is often wondered as to what modifications are done in order to reach the amount of power output along with engine RPM that is seen at these competitions. For instance, if you were pulling in a 3.0 class, then the turbo inlet size of your combination would be limited to 3.00”. Sled pull competitions are divided into classes that are limited to the turbo inlet size. One common place that Cummins performance can be found would be sled pull competitions. The love of the Cummins engines by consumers has opened up the opportunity for niche markets in the growing demand for more Cummins A mid-size Cummins diesel power display on a Saturday night sled pull, producing more than 1,300 reliable horsepower “at the wheels.” From there, the 5.9L and the later 6.7L, have proven reliable and dependable, giving them more favor to consumers. Cummins gained a lot of notoriety in 1989 with the introduction into the Dodge truck with a 5.9L, inline six cylinder, and turbocharged diesel engine. Even though there are other diesel engines such as the Duramax and Powerstroke (which can make power also), the Cummins has always been one of the founding forefathers of diesel power. The Cummins diesel engine has become extremely popular as the choice for performance. The engine usually reaches peak torque around 1700 RPM and maximum horsepower at 2800 RPM. The heavy internals also limit the amount of engine speed. The increased compression ratio of the diesel engine along with the longer stroke of the crankshaft calls for a heavy-duty rotating assembly made to withstand extreme cylinder pressures. A diesel engine can run on very lean air fuel ratios (referred to as stoiciometry) as high as 50:1 under cruising conditions compared to 14.7:1 of gasoline. The diesel fuel being vaporized by the heat and pressure becomes very efficient since the heat generated was used for ignition. The atomized droplets of diesel fuel are vaporized and start to burn rapidly which pushes on the piston causing the crankshaft to rotate. Then, right before Top Dead Center, fuel is injected into the cylinder. As the air is compressed it begins to heat up reaching temperatures upwards of 1400 degrees F. When the intake valve closes, the piston starts its travel up the bore compressing the air that filled the cylinder. Compression ratio is the total volume of the combustion chamber when the piston is at Bottom Dead Center to the total volume of the combustion chamber when the piston is at Top Dead Center. With the growing popularity of the mid-size diesel, specialized companies are catering to the growing demand for more power.Ħ.7L Cummins is 17.3:1. The compression ratio of the Here’s a sneak peak under the hood of a mid-sized Cummins powered sled pulling truck that is under construction. There are no restrictions to cylinder filling other than the intake valve itself. There is no throttle blade as in a gasoline engine. When the intake valve opens, air is pushed into the engine from the turbo directly into the cylinders. Longer stroke means that the pistons and connecting rods create more leverage on the crankshaft. The 6.7L Cummins has a bore of 4.21”, but has a stroke of 4.88”. There is a combination between the long stroke, boost and compression ratio. There are several factors as to why the diesel produces that low down RPM torque. Or, the low down grunt when pulling loads up steep grades at a low RPM. Torque is what you feel in the seat of your pants on the take off. With the help of the aftermarket, more performance can be gained from simple add-ons such as programmers, cold-air intake systems, exhaust systems and turbochargers, to all out hardcore engine internals. Whether the enjoyment is from the ease at which we pull our camper or the fact that we can take our work truck to the dragstrip on the weekend, diesel performance is in full swing. As diesel engines have become more technologically advanced, efficient and reliable, they are loved by members of all generations. The diesel engine, which was once considered a clanking bucket of bolts, has brought about a new era of drag racing and sled pulling. Now, it’s not uncommon to see a diesel powered dragster travel the quarter-mile in 8 seconds or an everyday work truck enter the Saturday night sled pull.
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