The Wood Shed

You never know what you're going to find in the pile.

Friday, June 23, 2006

Gas Mileage Improvement

Subtitle: Why isn't this simple upgrade standard equipment?

Driving a big SUV is decidedly not PC nor is it “green” or easy on the wallet. But when your life requires hauling and towing capacities greater than the size and weight of most hybrid vehicles, you don’t have many options. The old neighborhood adage, “Everyone is your friend when you own a truck” has never been more true. After all, why own one when you can borrow one? Well, you borrow it and it damn well better come home with at least as much fuel as it left with. These days bringing it home empty is more than just bad manners, it’s $75.

But I digress, back to my point. The standard engine for the entire line of GM trucks for the last six years has been the 5.3 liter V-8. GM engineers have fiddled and tweaked that motor to the point where the ’06 trucks get about 19-20 mpg on the highway. My 2001 Yukon XL only yielded 16 mpg highway until a few weeks ago. I installed an Air Raid high flow air filter system. The first two tanks after the install didn’t indicate any noticeable improvement and I sadly thought I had wasted $200. What I didn’t realize is that it takes a while for the computer to adjust various parameters to compensate for the increased airflow. On the third tank I was convinced I was looking at a sticking gas gauge sending unit: it was still showing over half a tank remaining while the trip odometer was at 250 miles plus. I always back up the fuel gauge by resetting the trip odometer when I fill up. Old aviator thing I guess, wanting redundant indications of fuel remaining. Normally I’m showing about an eighth of a tank remaining when the odometer reads about 350 miles. So I dropped the fuel gauge out of my scan – must be unreliable – and watched the miles per tank. I filled up at about 350 miles but it didn’t take as much fuel as usual. The gauge was correct. The ECU had recalibrated for the airflow and my highway mileage had increased to 19 mpg.

An increase of 3 mpg for an investment of $200, figure an average of $3/gal, resultant savings of $.03/mile and the payback is about 6666 miles. The Air Raid system simply replaces the restrictive plastic OEM filter box and disposable paper filter with a much more open filter shield and a reusable K&N type fabric filter. Some assembly required and you must periodically remove the filter, clean it, and re-install it but if you can work a screwdriver and socket ratchet you can install and maintain this filter. The only down side to this modification is a higher noise level in the cabin when you really put your foot in it. That wide open air box doesn’t muffle the noise as well coming back out of the intake at full throttle, gives it a deeper growl out of the hole. It’s not nearly as noticeable as the “sport exhaust” that Dodge is selling on some of their trucks, the factory version of the popular NASCAR mod: dual exhaust with high flow (reads “loud”) non-mufflers. The trucks that beg the question: “Why?” I can accept a little muffled growling from under the hood for a 19% gain in fuel efficiency.

Politicians keep calling for higher mpg ratings to be imposed on Detroit and Motown keeps countering with complaints about technical limitations and various other reasons why they can’t make it happen. I’d have to say that’s a load of BS: I just improved my highway mileage by 19% by swapping out the filter system. No changes that adversely affect emissions. Simply let the beast breathe better. The next test will involve an aftermarket throttle body spacer that is supposed to further improve airflow and increase mileage.

Hello, Detroit. Anybody listening? If I can improve gas mileage using commercially available parts why are you not incorporating such simple improvements into your designs? Get with the program.

Disclaimer: Your mileage may vary depending on vehicle type, condition of engine, driving habits, tire pressure, hair color, and any prescription meds you are currently taking (among other things – the possibilities are endless).

Second disclaimer: This is not a paid endorsement and the author’s results were unscientifically obtained during actual highway driving. No warranties or guarantees are implied or stated. Product contains materials known to be fatal to Norwegian lab rats domiciled in the state of California at elevations greater than five thousand feet and forced to survive on consumption of said material at a rate of ten times their body weight per day.

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6/24/2006 3:06 PM  

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