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racprops · 01-08-2021, 03:38 PM

From: Phil Knox's aero-modded 1970 VW van https://ecomodder.com/forum/showthre...-van-8675.html

OK HERE is some real numbers:

The standard baseline tank - mpg over 3668 miles of testing was 23.795 mpg,at a steady 55-mph( the Federal National Speed Limit).

With addition of all-season steel radial tires and bellypan,and after 981 test miles,the tank mileage was 26.136 mpg(a 9.83% increase)

With addition of boattail and cardboard rear wheel skirts and 589.4 test miles, the tank mileage was 30.187 mpg ave..

RAC So all that work give an increase of 6.392.

I can add propane booster and see an est. 20% improvement….on that VW that would be 4.75 MPG or a total of 28.554.

I have been able to add 15% to a 2000 Mercury Grand Marques that got 30MPG pure Highway 65MPH by leaning it from 14.7 TO 16.4 at which it reached its peak MPG and started losing at higher settings.

This car on a hard run from Phoenix to CA at 85 MPH got 24/25 MPG and once in CA at 80MPH got 26MPG Stock 14.7 as I was unable to set it up to smoothly switch from 14.7 to 16.4 so did not run it changed. IF I could that could have been 28.75 MPG at 85MPH and 29.9 at 80MPH theoretically.

Add the propane booster and see an est. 20% improvement so 34.8 MPG….just two mods.

IN a full sized 4 door Ford 4.6 4 speed auto running a 3.27 rear end and could do better with a 2.73 rear end.

Back to Chevy Vans: Page two:

The Chevy should react like any other bread box on wheels.If you can find the FLOW-IMAGES thread,you'll eventually see the Cd 0.16 "van" that Klemperer came up with in 1922 which remains a "benchmark for low drag today.That body would give about a 33 % mpg increase at 55-mph,more at faster speeds.

CAR and DRIVER attempted a full-size van aero-mod in the latter 1970s.Their bellypan was of no benefit unless painstaking detail was applied.

Your fan delete is one which is well known of and proven benefit.

I would mimic the front of any modern van or pickup if you can.

Smaller mirrors have shown measurable results.

One and a half feet length of boat tail gave me 4-mpg.

A receiver-hitch cargo box might serve you as a foundation for such a mod,with quick-on/quick-off capability.

This is something "hard to park" curbside and better suited to long highway excursions.

Too much work for LITTLE gains…

Thanks for the info gentlemen.

So in conclusion I will stick with engine and drive line mods and a few other mods to the fuel system and so on as they can really add up.

01-08-2021, 03:38 PM	#13 (permalink)
racprops Master EcoModder Join Date: Oct 2009 Location: Phoenix AZ Posts: 788 Thanks: 4 Thanked 64 Times in 56 Posts	From: Phil Knox's aero-modded 1970 VW van https://ecomodder.com/forum/showthre...-van-8675.html OK HERE is some real numbers: The standard baseline tank - mpg over 3668 miles of testing was 23.795 mpg,at a steady 55-mph( the Federal National Speed Limit). With addition of all-season steel radial tires and bellypan,and after 981 test miles,the tank mileage was 26.136 mpg(a 9.83% increase) With addition of boattail and cardboard rear wheel skirts and 589.4 test miles, the tank mileage was 30.187 mpg ave.. RAC So all that work give an increase of 6.392. I can add propane booster and see an est. 20% improvement….on that VW that would be 4.75 MPG or a total of 28.554. I have been able to add 15% to a 2000 Mercury Grand Marques that got 30MPG pure Highway 65MPH by leaning it from 14.7 TO 16.4 at which it reached its peak MPG and started losing at higher settings. This car on a hard run from Phoenix to CA at 85 MPH got 24/25 MPG and once in CA at 80MPH got 26MPG Stock 14.7 as I was unable to set it up to smoothly switch from 14.7 to 16.4 so did not run it changed. IF I could that could have been 28.75 MPG at 85MPH and 29.9 at 80MPH theoretically. Add the propane booster and see an est. 20% improvement so 34.8 MPG….just two mods. IN a full sized 4 door Ford 4.6 4 speed auto running a 3.27 rear end and could do better with a 2.73 rear end. Back to Chevy Vans: Page two: The Chevy should react like any other bread box on wheels.If you can find the FLOW-IMAGES thread,you'll eventually see the Cd 0.16 "van" that Klemperer came up with in 1922 which remains a "benchmark for low drag today.That body would give about a 33 % mpg increase at 55-mph,more at faster speeds. CAR and DRIVER attempted a full-size van aero-mod in the latter 1970s.Their bellypan was of no benefit unless painstaking detail was applied. Your fan delete is one which is well known of and proven benefit. I would mimic the front of any modern van or pickup if you can. Smaller mirrors have shown measurable results. One and a half feet length of boat tail gave me 4-mpg. A receiver-hitch cargo box might serve you as a foundation for such a mod,with quick-on/quick-off capability. This is something "hard to park" curbside and better suited to long highway excursions. Too much work for LITTLE gains… Thanks for the info gentlemen. So in conclusion I will stick with engine and drive line mods and a few other mods to the fuel system and so on as they can really add up.