MAX Update No. 80: Cooling Tests and Travels

Reader Contribution by Staff
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Back in October of ’09 (MAX Update No. 35: Nose Job for Better Aerodynamics) I mentioned I believed MAX could get away with a much smaller air inlet for the radiator–about 1/3 the size of its original area (which was one square foot). And I calculated that this smaller inlet would reduce drag by about a horsepower in cruise, which is a significant bite of MAX’s modest horsepower needs. And then about a year ago (MAX Update No. 52: Cooling System Bug Report) I did some test driving with the air inlet partially blocked off, which gave me confidence in my calculations…enough confidence to make the cooling air inlet in MAX’s streamlined body about half the size of the inlet in the Escape from Berkeley body.

And my static experiments with low power fuel consumption (MAX Update No. 68: Idle Speculation and MAX Update No. 70: MAX’s Theoretical Max) made me daring enough to start last month’s trip to Ohio with a small roll of white duct tape in my tool box, so I could experiment with closing off the inlet even further.

So here’s how MAX looked when I left Cave Junction (ignore the cardboard box in the passenger’s seat, it was a shipment I had to drop off at UPS on the way) with the radiator opening taped up to 60 square inches of inlet area–about 40% of its EfB size. Purists may think me snooty because I didn’t use the traditional silver-grey duct tape, but with the pink bandana on my face and the red plaid Elmer Fudd hat on my head, I think I looked sufficiently proletariat that the white duct tape passed without notice. It’s not like I was putting on airs.

The advantage of duct tape was I could hop out and tear it off if I had an overheating problem–remember, I’m still experimenting and still learning, and at this stage I preferred expedient to classy.

Up through Oregon (including a bumper-to-bumper traffic jam in Portland) through Washington, across Idaho, climbing into Montana and across the Great Divide and into Wyoming…no overheating problems, so I added more duct tape and narrowed the 5-1/2″ tall radiator inlet to 8″ wide. That’s 44 square inches, less than a third of the Escape from Berkeley nose opening. And that’s how I drove across South Dakota and into Minnesota, and by the way, did I mention there was a record heat wave going through the Midwest in mid-July?

This is MAX, a little south of Minneapolis, and this is Bill who is making a MAX of his own. Minnesota isn’t exactly on the short cut between Cave Junction, OR, and Lexington, OH, but I wanted to visit Bill and see how he was doing (quite well, by the way) plus take advantage of the heat to test MAX’s cooling system. If you’re wondering why the photo is fuzzy, it’s because even though the temperature was in the hundreds, the dew point was 81 degrees and fogged the camera lens. It was miserably hot and humid, but MAX’s temperature gauge never got out of the high hundreds so I narrowed the air inlet even more.

And here’s MAX in Indiana, with it cooling air inlet taped down to 5″ wide and 5-1/2″ tall. That’s 28 square inches; smaller than a paperback book, smaller than 1/5 the size it was during Escape from Berkeley. It cooled fine, though it was right up at the high edge of fine (I saw 220 on the temp gauge a couple times, when I was stuck in traffic) so I left it at that. That’s the size the opening has been ever since, and the minimal cooling drag is one reason MAX gets better than 100 mpg.

What have we learned from this? That by judicious reduction of airflow through the radiator, we can practically eliminate cooling drag’s contribution to MAX’s fuel consumption. There’s not much mileage to be gained by making the air inlet any smaller than it is now, but I can sure make it prettier, and adding an electric fan for traffic jams would make MAX a better city car.

Photos by Jacky Leggitt and Jack McCornack

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