Course Topic: RV Performance (6/97)
Instructor: Eric Davis, Eric's RV Performance Center, Sequim, WA
About Air Intake: It takes 9,000 gallons of air to mix with one gallon of fuel. Air intake needs to be extended to the front to avoid pulling 300 degree air intake temperatures off of the engine block. For every 100 degrees increase of intake air temperature, 10% of power loss occurs. This is heat radiating off the engine, not what's showing on the water temperature gauge. This is true for gas or diesel. Air intake temperature can be improved by extending air intake as far forward as possible behind the grill. But avoid any installation which might allow water to get into the air intake.
Air Cleaners: Many stock air cleaners can be replaced by after market products which are taller and which improve the volume of air, and hence engine efficiency. Recommended: KNN air filter as the best available. They are wire mesh and cotton, impregnated with oil. It is far superior to paper filters. It can be cleaned with a special solvent, let air dry for a half hour, re-oiled with a spray bottle, and be like new again. Cost is $40-80 for gas engines, and $80-90 for diesel engines. The KNN air filter is a particularly good change for the Dodge 5.9 diesel engine.
Exhaust systems, stock, are often very inefficient, and cause power loss because the exhaust tubing is convoluted, crimped, and therefore inhibits the free escape of exhaust gases. Tubular exhaust manifolds (a more modern version of what was earlier called "headers"), provide a far more efficient breathing system for both gas and diesel engines. Mufflers can also be an obstacle. After market options, such as Banks mufflers, can offer larger diameter tubing. This apparently may be most true for Chevrolet. The newer Dodge and Ford stock exhaust systems may pose fewer problems. However, he notes Dodge tailpipe appears to be a 4 inch diameter pipe -- but follow the pipe up for some inches and check the diameter there...
Full improvements to the breathing (intake and exhaust) system can, as a rule of thumb provide the stock horsepower rating at roughly 1,000 rpm below factory ratings. For example if the peak horse power on a gas engine is rated at 3,300 rpm, with a completely improved exhaust system that same horsepower can be achieved at 2,300 rpm; diesel improvements are comparable.
All About Diesel...
A diesel engine simply needs to be turbocharged. At higher elevations, a non-turbocharged diesel becomes highly inefficient. Some non-turbocharged engines were really not constructed to accept the extra demands of a turbocharger. On older Dodges with the 5.9 Cummins there was a significant problem with overheating. In '92 enter the inter cooled engine. With the turbo compressing the air, the intake air became much hotter. The "inter cooler" used a heat exchanger to lower the air temperature from about 350 degrees to about 200 degrees. But the downside was the pressure boost was lowered. The waste gate turbine housing was the solution for that problem, and would improve boost from approximately 12 to 20 pounds. The '94 Dodge went to a Cummins designed waste gated system, as well as an improved injection system.
Gauges: Exhaust gages (pyrometer); boost gages, transmission temperature gages are all helpful to have. When diesel engines are upgraded to get greater power, it's especially important to have at least a pyrometer and a boost gauge. Tip: Diesel engines should not be turned off until the pyrometer shows exhaust temperature has been lowered to 300-350 degrees. There are after market devices which will auto-shutoff the engine some minutes later after the appropriate temperature has been reached. Also, for start-up, don't push the engine to high rpms for the first mile or so.
About diesel fuel additives -- with the low Selfware fuels, older diesels may benefit from them. It's not likely additives are useful on newer diesel engines.
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