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MetroMPG 11-28-2007 03:15 PM

Finally: 100 mpg (US) round trip in the Blackfly - new and improved: 133 mpg
(Originally written May 24/06)

I've been scratching this itch since I realized it was possible, and after supper today I pulled out the stops and headed out to do the city loop:

(101 mpg - click to zoom)
  • ambient 70F - ish / 20 C
  • 30 min block heater
  • removed 55 lbs / 3% of vehicle weight (passenger seat, spare tire/jack, rear parcel shelf, misc.)
  • used moderate load/low RPM acceleration technique
  • alternator unbelted (I've been running that way since almost the beginning of this tank, except for approx. 30 miles of a 60 mile highway trip)
  • made 3 of 6 traffic lights
  • traffic was both light & accomodating (not as much of an issue with this acceleration technique)
Details: (click to zoom)

The tank MPG of course will change substantially between now and next fill-up (a highway trip coming up on Friday will pull it down to the mid/high 60's, I predict).

I've been recharging my battery with a combination of grid/solar. (I have a 15W panel that fits nicely on my cargo shelf, and gets 3-4 hours of good sun (when it shines) in my usual parking spot.

I was going to replace the starting battery with one of my deep cycle batts, but the one I have is too tall for the amount of space under the hood. I'm working on an alternative. It's not good for a starting battery to do a lot of discharge/recharge cycles to the depth I'm going without the alternator.

MetroMPG 11-28-2007 03:18 PM

August 27/06...

133 mpg (US)

Today I repeated the trip to the park to ride some trails (supposed to be crap weather tomorrow). Roads were pretty much deserted when I went just after supper - think I pulled onto the shoulder to let 3 or 4 cars by where the center line was solid, and signalled for maybe 6 or 8 to pass me where it was broken (and clear ahead). Managed not to hold anyone up. It was all very civil.

What's below are the results of mostly 2nd-3rd gear P&G, with some 1-2 as well. And a smaller amount of 3-4. The engine didn't quite reach normal operating temps on the first leg of the trip (8+ miles).

Interesting to see what the car is capable of. But the avg speed, as you can see is pretty low. ("RLS P&G: Really Low Speed P&G).

Then again... I just noticed that on my first 100 mpg r.t. its average speed was actually a tick lower than this effort. Interesting.

The "today" info is the entire round trip (just one trip today).

The "current" info is the return leg - slightly downhill, but barely. I think the FE is higher mostly because the car was somewhat warmed up. Though I also kept the speed a bit lower.

MetroMPG 11-28-2007 03:21 PM

6 or 8 months ago, I probably literally would not have believed this was technically possible.

For one thing, on this 133 RT I was virtually unmolested by other drivers - it was nearly all rural driving. Whereas the 100+ mpg RT's I'd been futzing around with earlier were all sub/urban driving with all the usual stuff: unpredictable lights, stop signs, pedestrians, and ... traffic (albeit small town traffic).

Another critical point: I touched the brakes once on the 133 mpg round trip, and that includes negotiating (ie. not "blasting through" approx. 14 turns at intersections, and 4 stop signs - which admittedly, I "rolled", but no more grievously than the typical driver.

MetroMPG 11-28-2007 03:23 PM

The mind set involved in doing this...

Ever seen/tried one of those motorcycle contests where the goal is to ride the course as slowly as possible without falling over? (Not trials riding, pylons in a parking lot.) Somehow it's sort of like that. :) More video-gamey than cardio-vasculary.

I suspect 133 isn't a "perfect" run. The car's absolute highest p&g FE is probably somewhere south of the blistering pace of 22 mph avg.

radioranger 10-06-2012 11:25 PM

congrats on the effort, I notice i get over 45 on back roads in my 98 Escort, , did you ever think of shutting off and coasting or are you already doing that, If you do i suggest an oil pressure accumulator tank for the motor , to pressure it and pre oil between starts, Moroso makes them .

MetroMPG 10-07-2012 08:57 AM

Wow - reviving an old thread. :)

I often kill the engine to coast to stops & turns, but I don't generally "pulse and glide" repeatedly in normal driving -- I find it tedious over long distances, and it's arguably harder on the car.

The exception was this "experiment", but it was just to see what was possible using the technique in a hard-core kind of way.

I don't worry about lubrication from starting/stopping the engine -- I don't think there's a serious wear issue there. Lots of vehicles with automatic engine start/stop systems (some battery hybrids, others conventional vehicles) have no additional measures for pressure/lubrication in between stops & starts -- aside from programming that waits for the coolant to be at operating temperature before enabling the feature. That suggests that frequent "warm" engine stops/starts aren't a problem for longevity. "Cold" starts are another issue of course.

radioranger 10-07-2012 10:09 AM

you are probably right on that , but i would think an accumulator like they use on drag race cars would ensure no damage could occur, course it adds expense, although every cold start would benefit and another benefit i forgot is you can run less oil in the crankcase which is a big deal for MPG or at least power production as crank will not be hitting as much oil in the pan,

radioranger 10-07-2012 11:02 AM

another lubrication tip I'm using is adding outboard 2 cycle motor oil to the gas, around an ounce per gallon, seems it would help with valve guide wear issues as well as upper cylinder friction. this new ethanol laced fuel is very dry to the engine.

Arragonis 10-21-2012 08:55 AM

Very impressive.

Two questions - how is your starter and battery holding up to on/off ? Mine seems noisier and it only has about 12K miles on it, or do you bump start ?

And secondly how about a video, that would be very cool :D

EDIT - just realised how old this is :D

MetroMPG 10-21-2012 11:00 PM

Old, that's OK. I don't mind bumping old threads if there's new info to add.

Starter: no change in the way it works or sounds. I mostly clutch start the engine though.

Video? Nope, I'm not posting a P&G video. Too many lawyers around! I'll gladly show you in person if you want to drop by though!

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