Fine-Tuning The Science of Fuel Mileage Testing

One manufacturer is blazing a new road toward more reliable big-rig fuel-economy testing standards

By John Stewart

Gale Banks Engineering is a diesel-tuning company with applications for a wide-range of light-duty pickups, motorhomes and medium-duty trucks. The company is highly visible in diesel racing, and now is working with large fleet clients to develop proven mileage-priority tuning technology in the Class 8 market.

The issue at hand is the word proven.

Mileage testing is notoriously difficult to conduct because conditions change constantly in the real world. There are dozens of variables to control, and to do it right, nothing can be taken for granted. Until recently, even the EPA’s methods of testing were subject to second-guessing.

So the quest to develop electronic tuning that guarantees significantly better Class 8 diesel mileage is an ambitious one. Assuring the tuning is appropriate for the newest, DPF-equipped trucks is another part of the challenge.

We asked Gale Banks about what he has learned thus far in the development process of their new product.

“We started developing tuning products first for the Detroit Diesel 60-series; now we’re working on a variety of engines,” Banks told us.

“The first thing we found was that some Class 8s have an on-board mileage display, and using available products it indicated an improvement in fuel economy. Yet, we found out within a few months (from a company we work with on this project) direct measurement and mileage logs show they weren’t actually getting better fuel economy.”

As it turns out, the mileage display is not accurate enough to be able to measure the small gains in mileage that can make a big difference when it comes to big rigs.

“We’re looking for hundredths-of-a-mile-per-gallon accuracy here, not half-a-mile-per-gallon accuracy,” Banks states.

Inside the box is a mechanism that allows for measuring fuel flow in a very precise scale. The dyno test replicates “real world” driving loops but eliminates such factors as wind, weather and driver inconsistency.

When one is looking through such a fine test-parameter screen, tiny variations in driving can make a big difference. This isn’t lost on Banks who is a stickler for accuracy.

“We’re looking at both the tunes and the person behind the wheel. The driver is a huge factor. The same driver can drive differently from day to day. If the guy is hot about something, he’s going to take it out on the rig. If that occurs, or if he is an erratic driver, we don’t want his inputs to kill efficiency of the truck. We want to deal with him,” Banks explains.

Along with the driver, there are many other significant variables to be controlled. Not least of which is wind.

“If you’re driving into a 20mph headwind, and you’re going 50mph, the actual aerodynamic load is 70mph,” explains Banks. “If you’re driving 50mph and you’ve got a 20-mile-an-hour tailwind, the actual aerodynamic load is 30mph.  There is a hell of a difference between the fuel consumption at 30mph, compared to 70mph.”

In order to get exact, repeatable mileage numbers, Banks has developed his own test equipment – and a procedure to replicate the procedure the federal government uses to set mileage numbers for new vehicles.

“Probably the closest thing to real world driving is the FTP, the Federal Test Procedure. It’s used on all automobiles, and I think, on half-ton trucks.” Banks explains. “It’s a pretty darn good test, and a few years ago, they made it even more accurate.

“So how do you get an accurate, repeatable test?  Run an FTP. But nobody has ever run an FTP on a semi, until now.  We’ve been running FTPs on pickup trucks, Kodiaks and medium-duty trucks for years now.

“So we took the FTP procedure we had, changed the mass or inertial weight, and made it such that it works properly for everything from a ¾-ton pickup all the way to a fully loaded Class 8 combo. Now the effects of rain, wind, driver emotion, all this stuff, is gone.

When on the dyno, the truck operator has to follow a trace on the computer screen, staying dead on that speed and load. Banks is using a total of 20 trucks, 5 of which will be control units, to gather enough data to be statistically accurate down to very fine increments.

“We have a test driver who gets in the cab and we run at least four tests of the FTP. The guy follows a trace on a computer screen, and he has to stay dead on that speed and throttle load.  And they have to repeat on a given vehicle with a certain setup, within a given statistical range. Or we find out why not, and do it again.

“Before we even run an FTP, the simulator is warmed up and heat saturated as is the truck, so all the lubricants and tire temperatures are correct.  Everything is the same every time we test. Any other form of mileage testing has emotional baggage, load baggage, windage, you name it.”

With a solid test procedure in place, Banks is optimistic that he can improve mileage on the average fleet by .4 mpg, which would be about 10 percent in most trucks, and do it without affecting reliability or creating service issues.

He does not expect to find that adding fuel to make more power is likely to lead to better mileage.

“If you want to improve fuel economy, you don’t do it with more fuel. There are other strategies for doing that, but we don’t add fuel at all. If the guy is going to accelerate faster, what’s the point, he’ll always use more fuel.  If anything, you want to take some [fuel] off the table, rather than let the guy burn it. Secondly, that excess enrichment is now producing more particulates.”

Banks is working with DPF-equipped trucks, and he worries that a truck using more fuel to achieve economy might end up generating other costs down the road.

More particulates means more emissions-system re-generation cycles on DPF-equipped trucks, and the particulate filters only have so many re-gens in them.

“Pretty soon the ash plugs up the device, and you get greatly excessive backpressure. So your fuel economy is degraded by more frequent re-gen cycles-you don’t get any power out of that, but you do burn fuel.

” A second risk is the increased frequency of re-gen cycles will end up forcing early replacement of the particulate filter,” explains banks.  “This is huge with the fleet owners; if you’re not emissions legal, you’re going to get zapped big time. “

Banks recognizes some truckers driving older trucks will want products providing them more power, or a combination of more power and the potential for better fuel mileage.

“If that’s the case,  I’m going to sell him what he wants. If that’s what he wants is both power and fuel economy depending on what he does, then I’m going to give him a device where that’s his choice. But it’s got to honestly make fuel economy in a real way.”

The biggest commercial fleets, of course, have a different priority.

“When you’re dealing with big fleets, what they talk about is fuel economy and time. They don’t want to slow the guy down too much, but they know the optimum average speed to make money. They’re paying the guy so much an hour and they’re depreciating their truck so much a mile. So there’s a complex formula that a fleet looks at.

“It’s not just mileage, not just going up hills faster. In a lot of cases they might settle for going up the hill slower, even if it adds a bit to the time, if fuel efficiency offsets the additional man/hour costs.”

At the time of this writing Banks Engineering is about eight months away from having all the data needed to confirm the tuning effects and begin production of their electronic engine-performance product. But Banks has a feeling proven and extremely well-documented fuel-economy numbers will become a strong marketing point.

“Fuel economy is the new horsepower,” says the diesel-performance guru. “There is now a whole enthusiast group centered around diesel fuel economy. As long as the truck has enough power for them, now it’s ‘give me fuel economy.’” – JS