Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Urba Centurion Update - (Kubota diesel, 100+ MPG in mixed driving

rqriley · 03-22-2014, 05:44 AM

Gentlemen, I was happy to run across your thread on Centurion. I am one of two original designers of Centurion - built at my former design firm in Phoenix AZ, Quincy-Lynn Enterprises. I was responsible for the engineering and participated in the styling and the actual build. I can confirm that the figure of 128 mpg is accurate for our vehicle. We tested for mpg on a little used highway north of Phoenix. We disconnected the fuel line from the tank and ran a hose to the fuel pump from a beaker inside the cabin. The beaker held enough fuel for about 5 to 8 miles. The roadway was on a slight grade, so we ran up the grade until the beaker was empty, filled the beaker, and then turned around and ran down the grade. It was just a slight grade. We ran five or six times in both directions and recorded the distance until fuel had been used in each direction. We then averaged fuel consumption and distance and calculate the result at slightly over 128 mpg. Each run included one acceleration to speed, and then a steady-state run at 35 mph until the beaker was empty. That's where the 35 mph fuel economy figure came from.

I don't have a clue why that other Centurion was only getting 45 mpg. In my opinion it would be virtually impossible to get fuel economy that poor with a Centurion built according to plans. Something must be costing him lots of energy with that vehicle. If you first take care of aerodynamic drag and vehicle mass, and make sure the brakes aren't dragging, then the key to high fuel economy is to be able to load the engine into its region of lowest bsfc (brake specific fuel consumption). That normally happens with a diesel engine when it's loaded to about 60 or 70 percent of full load. You do that with tall gearing, and then down-shift for acceleration.

I noticed some discussion about parasitic drag - water pump, alternator, etc. We did not do anything in that regard with the original Centurion. We left the parasitic drag alone - just as Kubota had designed it. We did use low-viscosity lubricants, however - to avoid too much churning in the transmission and final drive.

And if you can afford it, I'd recommend experimenting with turbocharging. Diesels love turbocharging, and it normally results in more power and lower fuel consumption.

I'm glad to see that you are taking it up a notch with the details. There were lots of things that we did not do with that original vehicle - we knew what they were but we just did not do everything we knew.

Good luck. And I'll try to come by again. My biggest problem is that I seem to be always overloaded with work.

03-22-2014, 05:44 AM	#60 (permalink)
rqriley EcoModding Lurker Join Date: Mar 2014 Location: Glendale AZ Posts: 3 Thanks: 0 Thanked 13 Times in 3 Posts	Great thread Gentlemen, I was happy to run across your thread on Centurion. I am one of two original designers of Centurion - built at my former design firm in Phoenix AZ, Quincy-Lynn Enterprises. I was responsible for the engineering and participated in the styling and the actual build. I can confirm that the figure of 128 mpg is accurate for our vehicle. We tested for mpg on a little used highway north of Phoenix. We disconnected the fuel line from the tank and ran a hose to the fuel pump from a beaker inside the cabin. The beaker held enough fuel for about 5 to 8 miles. The roadway was on a slight grade, so we ran up the grade until the beaker was empty, filled the beaker, and then turned around and ran down the grade. It was just a slight grade. We ran five or six times in both directions and recorded the distance until fuel had been used in each direction. We then averaged fuel consumption and distance and calculate the result at slightly over 128 mpg. Each run included one acceleration to speed, and then a steady-state run at 35 mph until the beaker was empty. That's where the 35 mph fuel economy figure came from. I don't have a clue why that other Centurion was only getting 45 mpg. In my opinion it would be virtually impossible to get fuel economy that poor with a Centurion built according to plans. Something must be costing him lots of energy with that vehicle. If you first take care of aerodynamic drag and vehicle mass, and make sure the brakes aren't dragging, then the key to high fuel economy is to be able to load the engine into its region of lowest bsfc (brake specific fuel consumption). That normally happens with a diesel engine when it's loaded to about 60 or 70 percent of full load. You do that with tall gearing, and then down-shift for acceleration. I noticed some discussion about parasitic drag - water pump, alternator, etc. We did not do anything in that regard with the original Centurion. We left the parasitic drag alone - just as Kubota had designed it. We did use low-viscosity lubricants, however - to avoid too much churning in the transmission and final drive. And if you can afford it, I'd recommend experimenting with turbocharging. Diesels love turbocharging, and it normally results in more power and lower fuel consumption. I'm glad to see that you are taking it up a notch with the details. There were lots of things that we did not do with that original vehicle - we knew what they were but we just did not do everything we knew. Good luck. And I'll try to come by again. My biggest problem is that I seem to be always overloaded with work.