Sunday, April 13, 2014
How to Calculate Fiberglass Wrap Headers
Exhaust wrap, sometimes called header wrap, is lighter, more stylish and probably more efficient than heat shields. It is used mostly on motorcycles but can also be used on cars. Headers are the exhaust pipes closest to the exhaust ports on a gasoline engine. They get hot enough to ignite paper, so motorcycle riders need some protection from that heat. Fiberglass wraps insulate more efficiently than metal shields. They might even increase your horsepower. Wrap manufacturers say that keeping all that heat in the pipes improves engine efficiency.
Instructions
- 1
Measure the diameter of your header or exhaust pipes with a micrometer. In most cases the diameter of your header pipes will be 1 3/8 inches to 3 inches.
2Measure the length of all the pipes you intend to wrap. Measure with a steel measuring tape from the exhaust port to the mufflers or the point where you want to stop wrapping each pipe. In most cases, this wrap is applied to V-Twin motorcycles, which have two pipes.
3Decide the width of the exhaust wrap you want to use. Most brands of exhaust wrap come in 1- and 2-inch widths.
4Begin calculating the length of wrap you will need per linear foot of header or exhaust pipe at 70 inches for 1-inch wrap and 30 inches for 2-inch wrap. Those lengths are the amount of wrap you need for each foot of 1 3/8-inch header or exhaust pipe.
5Add 6 inches of 1-inch-wide wrap for each linear foot of pipe that exceeds the diameter of 1 3/8 inch diameter pipe by 1/8 inch. For example, you will need 76 inches of wrap for each linear foot of 1 1/2-inch pipe and 82 inches for each linear foot of 1 5/8 inch diameter pipe. You will need 112 inches of 1-inch-wide wrap for each linear foot of 2 1/4-inch diameter pipes and 136 inches of 1-inch-wide wrap for each linear foot of 3-inch diameter pipes.
6Add 3 inches of 2-inch-wide wrap for each linear foot of pipe that exceeds the diameter of 1 3/8-inch diameter pipe by 1/8 inch. For example, you will need 33 inches of 2-inch wrap for each linear foot of 1 1/2-inch diameter header pipe and 45 inches of 2-inch wrap for each linear foot of 2-inch diameter header pipe.
Thursday, March 13, 2014
How to Calculate Exhaust Pipe Length
There are two schools of though regarding optimal efficiency for an exhaust pipe. Some would argue that an exhaust pipe should be short because of its aesthetic appeal. The other school of thought argues that longer tailpipes are better because they provide greater power curves and more overall engine power. There are two pieces of information that you must obtain in order to calculate the proper length of an exhaust pipe for your vehicle.
Instructions
- 1
Determine the center RPM values for your desired power curve. In other words, what will be the RPM amount for your average speed in the car? In general, motorcycles will be between 4000 and 5000. Cars will be between 650 and 800.
2Calculate the opening point of the exhaust valve. The opening point is recorded in degrees before bottom dead center (BBDC). The default valve opening for a motorcycle is 43 degrees. The default opening for a car is 90 degrees.
3Plug the two values into the exhaust length calculator program from the resources section of this article to get your result.
Friday, October 11, 2013
How to Calculate an Injector Flow Rate
Internal combustion engines are precise machines designed to exacting specifications to maximize power and fuel efficiency. To attain this, a specific fuel injector must be used that introduces fuel into the pistons for combustion at a precise rate as determined by characteristics of the engine. So long as these properties are known with certainty, the needed injector flow rate can be found with simple arithmetic.
Instructions
- 1
Multiply the engines horsepower by its brake specific fuel consumption (BSFC). The latter is a constant that measures between 0.4 and 0.7 for gasoline-powered systems. For naturally aspirated engines, estimate BSFC to be 0.4 to 0.5. Use 0.5 to 0.6 for nitrous engines. For forced induction and rotary engines, use 0.6 to 0.7 in the equation. Use a value between 1.2 and 1.4 for methanol-fueled systems.
2Divide the result by the number of injectors in the engine.
3Divide this new number by the injectors duty cycle. This is usually approximately .80, but never more. The result is the injectors flow rate in lbs. per hour per injector. Multiply the end result by 10.5 to convert this into cubic centimeters per minute (cc/min).
