MAX Update No. 16: Charmed Looks vs. Fuel-efficient Design


| 11/5/2008 10:26:35 AM


Tags: MAX, Auto X Prize, gas mileage, 100 mpg, aerodynamics,

OK, fun's over, time to get back to work.

I am getting so spoiled. When MAX's gas mileage drops into the 50s, I get grumpy.

I wanted to put 5,000 miles on MAX before the weather got wet (next project — a convertible top), a somewhat arbitrary figure, but it's been my experience that 5,000 miles (or 100 hours) is enough to say, “Yeah, it looks like this is going to work.” So for me it's a benchmark. I made it, but it involved a lot of road trips, and those involved a lot of freeway flying.

The freeways are not my favorite environment — one reason is they tempt me to go too fast for fuel efficiency. At 70 mph, MAX is no more fuel efficient than a ... well, actually, there aren't any production cars that get better than 50 mpg at 70 mph.

MAX does (barely), so I guess I shouldn't kick myself too hard. But heck, MAX is supposed to be spectacular, not just good. With its upcoming streamlined body (currently in that gray area between the drawing board and the highway), it's going to be spectacular. But gosh, can't it be kinda spectacular and still have the look-and-feel of a classic sports car?

MAX front viewI sure hope so, because — I know, I know, I should be ashamed of myself — I'm greatly enjoying driving MAX around in its Vintage/Prisoner/Escape from Berkeley regalia. Everybody digs “Classic MAX”, and I love all the attention. Total strangers say, “Ooooh, that car is so cute, can I take a picture, can I get in it, can you take a picture with me in it?” and I know I'm going to lose some of that attention when MAX goes all streamlined and serious.

Jim_94
4/16/2010 10:22:29 AM

I have been intrigued with the Max project for quite a while. I even bought one of the books on building a cheap sports car. I love the looks of Max and have ever since I was a kid and watched The Prisoner--the opening was better than the show. As I've been doing research I've found that Max has a C factor that is worse than a Hummer and that at speed those beautiful fenders act like lifting wings. So for my project I am looking at designing a body that would make the care as wide as the outside dimensions of the fender wells, this would give more interior room and some more room for side impact protection. I don't think the weight would be all that much higher. The old TR4 had an electric overdrive-have you ever considered a similar option? That might provide zippier pick up and the low rpm cruising as well. I've seen some of the footage of 7s flipping on the race track under really extreme conditions and going end over end with the driver walking away. Amazing. I used to drive a Triumph GT 6. Not exactly a comfortable car but it wasn't a killer on long trips either. The worst thing about it was the road noise. Hard to talk or listen to the radio. Jim


Jason Phillips
7/31/2009 9:57:59 PM

Seems to me that MAX could benefit from some added turbo boost. Diesels, unlike gasoline engines, can get more power AND better fuel economy from higher boost. A single stage centrifugal compressor (like a turbo or a Paxton-type supercharger) has a hard time achieving more than about a 4:1 pressure ratio. Now, that's about 45 psig (or 60 psia). I'll wager you're not even close to that now. Pump up the turbo boost to get more power AND improve fuel economy. THEN raise the final drive gearing to get the revs down (thereby improving fuel economy even more). THEN fit MAX with taller, narrower wheels/tires to reduce rolling resistance and bring cruising revs down even MORE. After that, well I'm sorry but improving aerodynamics is gonna be your best bet. It's free horsepower and fuel economy really. Manage your airflow wisely and you'll go farther, faster, on less fuel. What about closing off the front end and putting the radiator in the "trunk" lid with an electric fan drawing air down into the radiator and exhausting that air out the rear? That might help kill the low pressure area behind the car, thus reducing aerodynamic drag and improving fuel economy....just a thought. Still want that classic car look? What about the Lotus 49 that Jimmy Clark drove back in the late sixties? Clean, simple, compact, elegant, and timeless. ORRRR go a different direction and look to the Ferrari P4 and/or the Ford GT40 and/or the Lola T70 of roughly that same era. All gorgeous, all "aerodynamically friendly", and all classic. What about a waterless cooling system? Evans NPG and NPG+ can run at atmospheric pressure and never need to be changed. No corrosion with those propylene glycol-based coolants (unlike the ethylene glycol stuff most of us are using). Also, NPG and NPG+ will happily run at around 270 deg. F all day since they don't boil until about 370 deg. F at atmospheric pressure. Higher coolant temps reduce cylinder wall friction


Donald A. Meyer
12/24/2008 4:18:34 AM

New to your 100mpg MAX project, and noted your concern about Max's front fender drag. Have you thought about a simple light weight fiberglass flap (baffle) in front of the fenders, angled back 45 degrees on each side of the nose opening (similar in looks to a large air brake)? They could be supported by aluminum tube braces off of the nose cone area. That would deflect a lot of the air gradually past the tires and fenders, and thereby significantly reducing air drag due the fenders.





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