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Take me back to the RESULTS page...

This story is from the original manuscript which the July through October 1999 issues were based on. The detailed photos do not accompany this text for spatial considerations, however, they can be found by obtaining back issues of Four Wheeler Magazine.

Project M-P-G …Mileage Power & Gearing
by: Randall J.Thomas

About The Build Up:  We went about our build-up as anyone would in real-world applications... we started with the easiest and least expensive modifications first, and worked up from there until we reached our goals. During this project we "pre-tested" several versions of the same upgrade in order to ultimately use the "best of the best." In the course of the project only common tools were used with nothing more than general automotive knowledge required.

About The Project Vehicle:  In order to see obvious visible results from our efforts, we needed a vehicle that would be the most likely to reveal them as we went along. We ended up choosing a big, heavy and low aerodynamic vehicle with a large fuel guzzling big block. We started out with a 460 gas powered 1988 Ford F-350 4-Door, Crew-Cab 4x4 dually, converted over with a Bronco back half by Centurion in Michigan. With the bug shield, sunvisor, and wide dually fenders hanging in the wind, we couldn't ask for more of a challenge. Weighing in at over 7,000 pounds and putting out a best of 8.9 mpg, we knew this was it! At best a vehicle of this size, weight and power would typically max out at under 10 mpg in real life conditions. Therefore, getting anything better than that would be considered a feat to be reckoned with, and the means taken to achieve this goal could be beneficially applied to other similar situations. Even though this test rig may differ greatly from your own, the basic principles remain the same and the benefits can apply universally. Most of these modifications we chose can easily be performed in your back yard with exception of bending your own exhaust. We realize that major benefits could have been obtained by modifying the 460's restrictive cylinder heads and going to an efficient EFI compatible camshaft. Porting the heads will definitely be on the list whenever a need for a valve job rears it's ugly head. There also was the option of installing a supercharger, as well as throwing in a big bulging stroker motor. Even though these would all be notable improvements, they also would be major projects with much higher costs. We figured most would not go that far, and as this article proves, may not even be needed.

How We Tested: After each and every modification, we carefully tested and re-tested using identical procedures under duplicated test conditions. In order to insure the highest level of accuracy of our results, before undergoing each test we made sure that the ignition timing, tire air pressures and even the overall vehicle weight was the same. We even insured the air filter was fresh before every run. During the tests we also removed some of the items (filter, chip, etc) and subtracted the performance gain from the current number in order to cross check the results for maximum accuracy. Testing was only done when near identical environmental and weather conditions prevailed. We always tested with a full tank of fuel, on the exact same roads and locations. In doing our comprehensive tests we covered a total of 2,834 highway and city miles as well as 23 separate timed acceleration tests over a period of 7 months. On top of that we accumulated 5,871 miles of over the road miles insuring our test results were in fact accurate… they are!

About The Results: In this story, the gains in fuel mileage really shouldn't be measured by "how long will it take to pay for itself", although we did factor in those figures for the curious. Saving fuel also extends driving distances and means fewer stops on long trips.  As we proved, along with the fuel savings we increased horsepower and torque along with performance and acceleration, and those much appreciated benefits could never be judged in monetary savings as much as they could be appreciated in a "drivability value." As far as we're concerned, they paid for themselves right away! Each individual vehicle owner needs to set their own goals, and how much they feel comfortable in spending in order to reach them. But for now, at least you know where you may want to spend those hard earned dollars!

About the Build Up Shop:
When the gauntlet was thrown down and the challenge was made to try and squeeze every last ounce of performance and fuel mileage from this project truck, Performance Unlimited in Hartford WI. was ready and eager to accept. Performance Unlimited has been doing this for years for their customers, and was now ready to reveal their secrets. When it came time to select a project vehicle, they went all out and picked the biggest, heaviest and worst mileage vehicle the could find.  Once in there hands they accepted the challenge to get an astounding 50 percent increase in fuel mileage while increasing the performance and power a whopping 30 percent... Both at the same time! Their ultimate goal was to get near-diesel mileage with gasoline horsepower. No punches were pulled, and no holds were barred, but the folks at Performance Unlimited wanted to achieve this goal by using products the average automotive enthusiast could afford, therefore the exotic powerplants and internal engine mods were left aside... for now.

Other Directions Not Taken: There are many other performance products and modification available that we did not choose to take for various reasons. The popular underdrive pulley sets were not used because of the low RPM nature of our application as well as increased idling in extreme heat conditions. The small amounts of (hardly ever reached) higher RPM horsepower to be gained would not have offset the disadvantages of the potential overheating problems and low alternator charging at the lower engine speeds. We did try an aftermarket ignition and not to our surprise, did very little if anything. So for simplicity sake and to make on the road repairs easier, we retained the more than adequate stock ignition. As we add more accessories after this, a better ignition may in fact be beneficial… but later.                             

For now, the best way to describe ignition requirements, is this simple scenario. "After market ignitions can be of great help when used in the correct situation. However, most factory ignitions, especially modern versions, are not necessarily 'under-gunned' by any means. Consider this... if you have a campfire soaked with lacquer thinner representing a lower compression, stock type engine), how 'big of a match' do you really need to get that campfire going (representing your ignition)? Now, take that same campfire soaked with fuel oil (representing a high compression, supercharged, nitrous injected or otherwise high-performing engine)... 'now' how big of a match would you need to light that same campfire (meaning, a high output ignition.)? At this point, an aftermarket ignition is 'required', therefore, where visible benefits can be realized. Besides, the on-the-road repairability of the OEM ignition can outweigh any benefits, when you're stranded hundreds of miles from home.

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The Challenge is laid down

Do you think it's possible to take a 7,000 pound Dually crew cab 4x4 with a gas guzzling big block and go from 8 miles per gallon to an astounding 13 miles per gallon, AND increase the output an additional 70 available horsepower to boot? Oh yeah, the deal is that no internal engine mods can be done… just over the counter bolt on parts could be used. The crew at Performance Unlimited 4-Wheel & Off Road Center in Hartford, WI. thought so, when they took on this landmark challenge. 


Getting Started
The age old phrase of "having your cake and eating it too" must have came from an optimist dreaming of finding a way to increase performance as well as fuel economy at the same time. Those words assembled in the same sentence might be successfully argued that they fall into the same category as "inexpensive quality" or "cheap Gold." However, Performance and economy in many cases can be one in the same. Basically, the more efficient an internal combustion engine becomes, the more available power can be had when utilizing the same amount of air and fuel. This of course, is true up to a point, and fortunately for real life applications this couldn't be more true in this case. Rather than detailing standard installation procedures, we will look at the benefits and results that can be had by specific modifications, and leave the detailed installation instructions to the manufacturers installation manuals.

Wives Tales and Farmers Tricks
Stories of magical brews of gasoline additives and the mystical cow magnets tied to fuel lines has placed the average automotive enthusiast into a corner of fear and skepticism... and rightly so. Those that thought snake oil salesman died in the old west couldn't be more mistaken. However, there are many respectable products out there that can do 'magical' wonders to improve both economy and performance… at the same time. 

How it Works
The basic principle of making an automotive engine more efficient is getting the highest volume of the  freshest, cleanest and highest oxygen content air into the engine as easily and quickly as possible (volumetric efficiency), and getting the expended exhaust gases out as completely and quickly as possible. If 100% combustion efficiency can be achieved, that would be maximum power and efficiency.

When an internal combustion engine operates, after ignition has occurred and combustion has been created, not all the exhaust gasses can leave the cylinder in time, especially at higher rpm's. When the new incoming air enters the cylinder, it can not completely fill the cylinder due to the remaining burned exhaust gases still lingering around. This is called the
Residual Fraction of combustion remaining gases. On the average, about 9% of the cylinder can not be filled with fresh air/fuel mixture because of this. Furthermore, that 9% of left-over exhaust gasses can contaminate, or 'extinguish' yet another 9% of the fresh incoming mixture as well. This leaves us with around 18% of wasted energy per firing cycle. Both performance as well as economy is compromised.

The Numbers Game
Simply using a stop watch and timing a 0-60 run may not accurately, or even remotely, show up changes in a vehicle's performance. One test could show a certain time while accelerating quickly at low end and slowing up as it neared top end, and another run could show exactly the same time while accelerating slowly at first, then speeding up near the top end. Even though the times are identical, the torque (acceleration) and horsepower (top end)  figures would be totally different. In some of our tests the 10-60 times were less than others, yet showed more power. This was because the acceleration curve changed more noticeably than the overall time. So if you want to test at home, here's a great tip: Take a tape recorder, preferably a digital memo maker model, and accelerate while sounding off in 10 mph increments. Usually you'll need at least five increments to make a decent curve. Now you can see differences in every portion of the acceleration range, and detect changes at low end, midrange and higher rpm ranges. In order to maintain consistency though, you'll need to stay in one gear during the entire range, keep tires from slipping and maintain common weather conditions, wind etc. For safety, have a passenger read off the speedo clicks, and of course, only do this on a closed course for safety. Several runs for each try can result in an average that should be close to the actual time without timing errors included.