MAX Update No. 68: Idle Speculation


| 2/21/2011 2:58:24 PM


MU68HoneybearIdleThe honey bear is back. 

One advantage of hybrids over ICE cars (that's Internal Combustion Engine, if you're new here) is they don't have to idle while waiting for the light to change. That's no small advantage with normal cars. For example, according to my ScanGauge II (about which I'll write more some day), my '96 six cylinder minivan burns 0.43 gallons per hour at idle (with an occasional bump to 0.44), or in other words, about a gallon every 2 hours and 19 minutes.

Unfortunately, I can't plug my ScanGauge into MAX, because MAX doesn't have an OBD II port. That's the little on-board diagnostic (hence OBD) socket under your steering wheel, if you have a mid-'90s or newer car. The OBD protocol is a way to get electronic information from your car's fuel injection computer to the mechanic who is wondering why it's running funny, information that includes how much fuel the engine is burning. The ScanGauge II translates that info into plain English, and puts it where you can read it, on the screen of a little box that sits on top your dash.

MAX's fuel injection is strictly mechanical. There's no computer, thus no data to read. So I plugged in the HBFCI (Honey Bear Fuel Consumption Indicator), calibrated to 4 fluid ounces (118 milliliters really, 'cause it's hard to find anything that will measure a fluid ounce precisely), and goofy as it may look, that space between the honey bear's neck (marked with yellow zip-ties) and knees (marked with blue tape) is within a percent or two of 4 oz.

So what did I learn? After I got MAX warmed up, I filled the HB to just below the lips* and let the engine idle. When the fuel level got down to the neckline I started the timer. When the fuel level got down to the kneeline, I took this photo.



Four ounces in 13 minutes and 12 seconds. That's 3.425 minutes per ounce. Times 128 (fluid ounces per gallon) is 438.4 minutes per gallon, about 7 hours and 18 minutes. 

Jack McCornack
3/8/2011 1:47:20 AM

Okay Jason, you've convinced me. I'll start scouring the wrecking yards and see if I can find a starter/alternator from a 2007 to 2009 Malibu or Vue. On those cars, the BAS didn't seem to do much good; not enough to justify the increased sticker price (they were discontinued because they didn't sell well), but for MAX, another 19 horses might make up for the extra weight and expense. I'll look into it.


Jason Hinton
3/6/2011 5:34:18 PM

It sounds like Max is perfect for your type of driving. A hybrid is much more difficult to build than MAX, no doubt. The problem is the control systems needed to make the engine and electric motor work together seamlessly. I'm not sure what types of hybrid system you have looked at but something like GM's BAS (now eAssist) might be worth a look. The BAS system (Belt / Alternator / Starter) simple removes the alternator and starter and replaces them with a single electric motor. This motor starts the car, provides power for the electric systems, provides regenerative braking, and gives an electric boost under acceleration. Mechanically this is a very simple, improves fuel economy 30%, and adds only 100 pounds for the 36V battery pack. Something like this is so easy for an automaker to do is is shocking that such a system isn't a standard feature for every car. The Prius works well for us but is a larger car than what we need. At the time it was the most fuel efficient car in the used market. While I like the Leaf it is not sold in our state nor do we need a new car. Her Prius only has 75K miles and my Jetta TDI has only 215K. Both have been trouble free and have a lot of life left in them. In 2-3 year we may look at replacing my VW and then an electric like the Leaf will be on the top of our used car shopping list.


Jack McCornack
3/6/2011 2:05:02 AM

Jason, a Prius sounds right for your family...though as far as your wife's commute goes, I think a Leaf would be even better. And if you were on a tight budget, a home built electric car would meet her commuting needs. A short (but time consuming) trip is exactly right for a low tech electric car, of the style that motivated MOTHER readers have been building for 30+ years. But I'm in a rural environment, about four miles from a town of 1500 souls. The county seat has 33,000 and it's where we go if we need anything exotic, such as trousers or fax paper. To see my doctor or a movie, I drive for as long as your wife drives to work...it takes us both 40 minutes, but her drive is 7 miles and mine is 30 miles. So an efficient cruiser works for me, better than an efficient traffic jammer would. If I had Toyota's resources, perhaps an ultralight hybrid system would be better than what I have, but on MAX's budget, and using off the shelf components, the added weight of the electric drive system would hurt MAX more than it would help. I've looked into this a lot, I've got a good support group of EV builders and suppliers, and I don't see how we could hybridize MAX without adding 250 pounds to it--which would mean I'd need more power to get over Hayes Hill and up Eight Dollar Mountain. I'm in an environment where MAX benefits greatly from light weight, and wouldn't gain much by driving slow with the engine off.




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