Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - 2000 Honda Insight: 14% better MPG @ 80 km/h (50 mph), with 5 simple aero mods (ABA)

jime57 · 10-18-2011, 09:08 PM

Darin,

I have attempted to duplicate your results with my own 2006 Insight. I don’t come anywhere close to the 14% that you measured. The list of modifications that you made do not seem to support a 14% improvement in fuel economy. I think that you must have unintentionally tripped over some sort of measurement bias, or error. I certainly do not want to be argumentative, but I think we should get this sorted out, in the interest of the science.

A logical review of what we all here have learned and measured for various modifications would also indicate that 14% is out of reach for this set of modifications. Can we review just briefly? You indicated 5 modifications:
-grill block, full upper and about ½ of lower,
-elimination of right mirror.
-replace the left side mirror with a folding mirror,
-elimination of the passenger side wiper and hatch wiper,
-elimination of the front license plate bracket.

From prior experience here, folks have reported around 3% for grill blocks, plus or minus. Full elimination of mirrors has also been reported at about 3%. Elimination of the tag bracket is probably worthless, since it sits in a stagnation area, and in any case is low enough so as not to disturb the overhood air. The passenger wiper also sits in a stagnation area and is probably worthless. Elimination of the rear wiper might provide a very small improvement, but remember that it is vertical and aligned with the air stream over the hatch.

Regarding mirrors, in this thread:

http://ecomodder.com/forum/showthrea...fied-95-2.html

you made measurements on your metro and reported results in msg #14 for a setup very similar to what you have tested on the Insight. For that experiment, you reported an improvement of 2.3%. The 2.3% is very close to the 2.4% I got by deleting both mirrors on a Toyota Echo. Best as I can recall from reading all the mirror delete tests over the last couple of years, folks have pretty much reported 2-4%. The Insight mirrors are obviously very well designed, so an improvement from deleting them both is quite likely to be 3% or less.

Grill blocks present a bit more of a estimating problem in my opinion because I think I recall some pretty widely varied reported results. In this post:

Testing grille blocking & wheel skirts: +5.7% improvement - MetroMPG.com

You reported an improvement of 2.6% for a well designed and executed test.

In this post:

http://ecomodder.com/forum/showthrea...ivic-1822.html

There was a report of about 4% improvement.

Though I installed grill blocks on my Echo, I do not recall any testing.

As I said, I have tried to duplicate the results. Not believing in short distance testing for the rather erratic and fidgety Insight, lacking a cruise control, and being complicated by Assist/Regen and lean burn, I’ve become convinced that only long range average FE at fixed average speeds hold the answers. I have been using a two way course of 48.1 miles, turn in the middle. The course is along I64 and I95 here in Richmond and is reasonably flat with no really big hills, so I can maintain lean burn about 95% of the time. I did 3 baseline runs at an average RT speed of 50MPH, per my scangauge. The baseline runs were 93, 93.7, and 93.6 MPG. There were two modification measurement runs on 10/17 resulting in FE of 98.3 & 99.4 MPG, and two modification measurement runs on 10/18 resulting in FE of 99.8 & 99.8 MPG (a slightly warmer day).

The average baseline is 93.43
The average of all modification test runs is 99.28
Improvement = 6.26%

I LOVE the improvement, but it doesn’t come close to 14%.

I did make one slight change to your setup. I retained my left side mirror since I can’t safely drive in moderate traffic without it. I’ll spot you 1% for that change. I also note that your course had little traffic, so I’ll spot you 1-2% for the added turbulence on my course.

Bottom line, I see an adjusted FE improvement of 8-9% at best on a flat, lightly traveled road.

I’d be very interest in your comments and where you think one of us may have gone wrong, if not both of us. Perhaps the real number is actually 9-10%, but I’d pretty much doubt anything over 8%

As I said, I highly respect the work you are doing and the integrity that you have given to the testing process, but I think there is something amiss here.

10-18-2011, 09:08 PM	#43 (permalink)
jime57 Master EcoModder Join Date: Oct 2008 Location: Mid-Atlantic Posts: 491 OurInsight - '06 Honda Insight Thanks: 170 Thanked 69 Times in 44 Posts	Darin, I have attempted to duplicate your results with my own 2006 Insight. I don’t come anywhere close to the 14% that you measured. The list of modifications that you made do not seem to support a 14% improvement in fuel economy. I think that you must have unintentionally tripped over some sort of measurement bias, or error. I certainly do not want to be argumentative, but I think we should get this sorted out, in the interest of the science. A logical review of what we all here have learned and measured for various modifications would also indicate that 14% is out of reach for this set of modifications. Can we review just briefly? You indicated 5 modifications: -grill block, full upper and about ½ of lower, -elimination of right mirror. -replace the left side mirror with a folding mirror, -elimination of the passenger side wiper and hatch wiper, -elimination of the front license plate bracket. From prior experience here, folks have reported around 3% for grill blocks, plus or minus. Full elimination of mirrors has also been reported at about 3%. Elimination of the tag bracket is probably worthless, since it sits in a stagnation area, and in any case is low enough so as not to disturb the overhood air. The passenger wiper also sits in a stagnation area and is probably worthless. Elimination of the rear wiper might provide a very small improvement, but remember that it is vertical and aligned with the air stream over the hatch. Regarding mirrors, in this thread: http://ecomodder.com/forum/showthrea...fied-95-2.html you made measurements on your metro and reported results in msg #14 for a setup very similar to what you have tested on the Insight. For that experiment, you reported an improvement of 2.3%. The 2.3% is very close to the 2.4% I got by deleting both mirrors on a Toyota Echo. Best as I can recall from reading all the mirror delete tests over the last couple of years, folks have pretty much reported 2-4%. The Insight mirrors are obviously very well designed, so an improvement from deleting them both is quite likely to be 3% or less. Grill blocks present a bit more of a estimating problem in my opinion because I think I recall some pretty widely varied reported results. In this post: Testing grille blocking & wheel skirts: +5.7% improvement - MetroMPG.com You reported an improvement of 2.6% for a well designed and executed test. In this post: http://ecomodder.com/forum/showthrea...ivic-1822.html There was a report of about 4% improvement. Though I installed grill blocks on my Echo, I do not recall any testing. As I said, I have tried to duplicate the results. Not believing in short distance testing for the rather erratic and fidgety Insight, lacking a cruise control, and being complicated by Assist/Regen and lean burn, I’ve become convinced that only long range average FE at fixed average speeds hold the answers. I have been using a two way course of 48.1 miles, turn in the middle. The course is along I64 and I95 here in Richmond and is reasonably flat with no really big hills, so I can maintain lean burn about 95% of the time. I did 3 baseline runs at an average RT speed of 50MPH, per my scangauge. The baseline runs were 93, 93.7, and 93.6 MPG. There were two modification measurement runs on 10/17 resulting in FE of 98.3 & 99.4 MPG, and two modification measurement runs on 10/18 resulting in FE of 99.8 & 99.8 MPG (a slightly warmer day). The average baseline is 93.43 The average of all modification test runs is 99.28 Improvement = 6.26% I LOVE the improvement, but it doesn’t come close to 14%. I did make one slight change to your setup. I retained my left side mirror since I can’t safely drive in moderate traffic without it. I’ll spot you 1% for that change. I also note that your course had little traffic, so I’ll spot you 1-2% for the added turbulence on my course. Bottom line, I see an adjusted FE improvement of 8-9% at best on a flat, lightly traveled road. I’d be very interest in your comments and where you think one of us may have gone wrong, if not both of us. Perhaps the real number is actually 9-10%, but I’d pretty much doubt anything over 8% As I said, I highly respect the work you are doing and the integrity that you have given to the testing process, but I think there is something amiss here.