Under Hood Air Filters
- By Bruce Mallinson
- Published 11/10/2005
- Technical
- Unrated
Bruce Mallinson
I started writing in 1992 for the Trucking Industry. My career in this industry started in 1969 at the young age of 19. I have been developing high performance diesel engines for the past 28 years. Please visit my web site @ http://www.dieselinjection.net
View all articles by Bruce MallinsonDid you ever stop to think about the affect an air cleaner has on the air and oxygen that is about to enter your engine? Are Conventional trucks with the big beautiful stainless air filters on the side of the truck causing you to loose fuel mileage because they are not aero dynamic?
Lets talk about this: An internal combustion engine burns oxygen just like our bodies. When air is heated the molecules of oxygen are displaced and there is less oxygen per cubic foot than with cool air. Humidity also displaces oxygen so a hot day with high humidity is not good for the engine.
Cool dry nights are what the diesel engines thrive on. Hot Air Balloons fly because the propane flame is heating the air and this displaces the oxygen making the air inside the balloon lighter.
So now lets think about the aero dynamic trucks with the air cleaner under the hood. There is only one air cleaner, which is around 1350 cfm (cubic feet of air per minute) and the high horsepower electronic engines of today require about 1300 cfm at wide open throttle. The large stainless air cleaners used on the conventionals are 1700 cfm each totaling 3400 cfm. So the conventionals have almost 3 times the air available to the engine which means the air filter elements only need to be changed once when the trucks with the under the hood air cleaners have to be changed 3 times.
Lets now think about how hot the ambient air temperature is under the hood of a truck that is pulling a hill. The engine is 210 degrees, the exhaust manifold and turbine housing is 1400 degrees and the exhaust pipe is 900 degrees. Heat rises and the air up against the hood has no place to go except against the firewall. So how hot is the air filter housing? Is it 200, 300, 400 degrees while the truck is pulling the hill? I’m not sure, but I guarantee you its much hotter than the air cleaners on the outside of the truck. Did you ever ride a motorcycle without a windshield in the northern states during the fall once the sun goes down? It’s cold! Well that same cold air is keeping the external air cleaners cold, and keeping the molecules of oxygen closer together allowing more oxygen to enter the combustion chamber. Now we still have piping under the hood of the truck, however only the molecules of oxygen that actually touches the piping will pick up some of the heat.
With the air cleaner under the hood, if the element picks up under the hood temperature it will pass it along to the oxygen molecules, they have to pass through the paper in order to leave the dirt behind. So how much hotter is the air coming out of the air cleaner that is under the hood, I’m not sure, but what I’m am sure of is the engine multiplies the temperature by 3 of what is entering the turbo. The difference between a 40-degree day and a 90-degree day is NOT 50 degrees, its 150 degrees.
I did purchase a T-600 Kenworth to pull my RV because of the longer front springs and sharper turning radius. Some RV parks have tight corners and my rig is 83 feet long. I love my T-600 however, I would love to have duel Vortox external air cleaners on the side of the cab.
Logging Trucks: Its been brought to my attention that trucks equipped with the 12.7 Detroit at times can’t pull away from the loader because of the lack of responsive horsepower and torque. So in order to get the loaded rig moving the loader or bulldozer has to give the semi a push. Its not that the engine doesn’t have enough power to move the load, the computer won’t release enough fuel until the engine produces 8 psi. of turbo boost. So how can you make boost if you can’t get the truck rolling? Simply install the Pittsburgh Power Performance Computer and the moment you let out the clutch the engine will develop enough power and torque to effortless pull away form the load loader under its own power. As your pulling up the grades in the low side of the transmission the shifts will be much smoother because of the response and elimination of the lag. Your driveline will feel much less shock load and the result of that are many more miles of service from the transmission and differentials. You, as the driver, will love the additional power and fuel mileage the performance computer will give you.
Good News for the owners of Accert Caterpillar Engines: I recently had the opportunity to check the back pressure on one of these twin turbo engines and was pleasantly surprised at what I found. Under hard acceleration the backpressure was greater than the turbo boost, however during a long pull the waste gates open and the backpressure dropped to 10 psi. lower than the turbo boost, which is great.
We have installed several FASS Fuel Systems on the Acert Cat Engines and the results have been very good. The first thing the truck owner says: My mirrors no longer shake. Then, during the first test ride, they say the truck is much smoother and more responsive. Charlie Glass of Stony Creek, VA. feels the FASS System gave his Acert about ½ mile per gallon improvement in fuel mileage.
More good news for the Acert Cats, our W900-L muffler systems will fit under to bunk to replace the 2 reverse flow mufflers that Kenworth and Internationals use. This system greatly reduces the exhaust backpressure and allows the truck to run FREE!