2000 Honda Insight: 14% better MPG @ 80 km/h (50 mph), with 5 simple aero mods (ABA)

[3-Wheeler]

Originally Posted by jimepting

...It is said by many Insight "experts" that using the assist/regen will lower fuel economy numbers, since the process is inefficient to some degree - but I haven't seen any numbers on that. I certainly think I see that inefficency but it is a small one if the assist is only occasional.....

Hi Jim,

The above statement can be considered true for a stock Insight.

If the battery is on the weak side, then background charge can cut into fuel mileage without the owner really noticing.

There are three options that I know of to alleviate this:

1) Turn of the IMA battery as Metro has
2) Install a Calpod IMA disable switch (I used this for 1-1/2 years)
3) Install MIMA (which I have now in the form of MIMA-CL)

The last two options allow any type of fuel comparisons without having the IMA battery affect results.

Jim.

[3-Wheeler]

Originally Posted by jimepting

It is interesting that 3-wheeler has not revealed any fuel economy data taken directly for FE measurements. I met Jim last summer and talked to him at some length. Very pleasant, helpful and thoughtful gentleman. I did not bring up the measurement subject, but we had discussed it earlier on this forum. He had been a fan of roll-down testing instead, but he has found some technical GPS problems with that mode of testing.

I'm waiting anxiously for him to post some tuft testing on his beautiful boat tail. I'm not sure he considers the project finished though.

Hi Jim,

Actually, my fuel records are posted here at EM. Just look in the garage.

And you are recalling correctly about the GPS giving too erratic of readings to really be useful.

Because of this, I gave up on coast-downs for a while.

Since then, I found an old camera around the house and am recording the speedometer readings during coast-downs in video mode. I play back the video frame-by-frame to get the exact speed decrease and put the numbers into a spreadsheet.

If this turns out useful, I will post something.

Regarding the tail, I still think the upper-back portion is too steeply sloping. Tuft testing would hopefully prove my hunch.

_________________

Interesting topic and discussion!

Jim.

[3-Wheeler]

Originally Posted by jimepting

Yeah! But I sure would like to see some results from 3 Wheeler's work before I plunge into that large amount of work

Hi Jim,

The most solid evidence I have since adding the tail is this....

Last summer, my Mom and I headed out on a 150 mile (one-way) trip, on a hot 95F day.

We traveled over flat and slightly curving roads at 55 mph, with low winds.

My average fuel consumption was 95mpg when we arrived at our destination. The only time I used MIMA, was accelerating when exiting small towns along the way.

If I recall correctly, my average over this same trip the year before with the car mostly stock was 85mpg.

_________________

The largest reason for adding a tail to an Insight might be "awareness" of the general public.

I find that large pickups are definitely the most likely of following me for any distance. Small cars like the Insight, just zip right by me. Trucks on the other hand will sometimes follow for several miles even though they can easily pass.

Once they tail-gate long enough for a good look, they mostly zoom past, again at their normal speed.

So yes, let's add more tails to pick people's interest.

I'm really not sure why, and this is probably a subject for another post, but since adding the tail, I have noticed three more brand new full size pickups in our subdivision. I can't figure it out!

Jim.

[jime57]

Originally Posted by 3-Wheeler

Regarding the tail, I still think the upper-back portion is too steeply sloping. Tuft testing would hopefully prove my hunch.

_________________

Interesting topic and discussion!

Jim.

I suspect Phil would say that also. Some tuft testing would help with that mystery, as you say. Wish I were close enough to run the video camera.

Sometime next week I intend to do some testing just on the hatch window. That might provide some insight It is just possible that the angle is pretty much ok for the existing length. Honda never contemplated adding a boat tail. It has always been hard for me to rationalize a mistake on Honda's part in making the hatch too steep. After all, they had lots of resources and were highly motivated to get it right.

I was looking at the hatch the other day, and I think one could make the angle a bit lower by sculpting a spacer to raise the rear a couple of inches. Sealing would be a difficult problem, but I think it could be done.

Do you think that a better boat tail might be designed by reducing the angle just where the hatch ends and the tail begins?

Good to hear from you!

[MetroMPG]

Originally Posted by 3-Wheeler

Since then, I found an old camera around the house and am recording the speedometer readings during coast-downs in video mode. I play back the video frame-by-frame to get the exact speed decrease and put the numbers into a spreadsheet.

I've done exactly this kind of testing (to test low speed rolling resistance).

It can be very accurate, especially with a digital speed readout.

(Far more precise than a stopwatch & analog gauges, which is how some tried doing it in the olden days.)

[MetroMPG]

Originally Posted by jimepting

Sometime next week I intend to do some testing just on the hatch window. That might provide some insight

Ha.

Any plans to video or get pics of the tests? If not, I've been thinking of doing the same thing using the "webcam on a stick" method.

I know Phil has said there's separation on the back glass. That makes me really want to "see" just what's going on back there.

Otherwise I would have assumed Honda got it just right.

[jime57]

Originally Posted by MetroMPG

Ha.

Any plans to video or get pics of the tests? If not, I've been thinking of doing the same thing using the "webcam on a stick" method.

I know Phil has said there's separation on the back glass. That makes me really want to "see" just what's going on back there.

Otherwise I would have assumed Honda got it just right.

I plan to borrow my daughter's video camera and have wife shoot video from passenger compartment. I'll post the video, if I can figure out how to do that. At 73 I'm electronic gadget challenged

I'm sure you will help me get it onto the site.

[COcyclist]

Originally Posted by MetroMPG

I've been thinking of doing the same thing using the "webcam on a stick" method.

I know Phil has said there's separation on the back glass. That makes me really want to "see" just what's going on back there.

Me too. Although if you look at threewheeler's fuel log, it has been really climbing since the tail was added. He is obviously doing something right. He mentions some electronic mumbo-jumbo that a diesel owner like me, doesn't understand and that could have something to do with it too. I have to think the air really likes the shape though.

[woody]

retrorides (dot) proboards (dot) com/index.cgi?action=display&board=general&thread=7033 6
(I can't post links because I'm a noob)
3 different ideas for aero mirrors on this porsche 356 custom.

[sbdeadelf]

Originally Posted by jimepting

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 think I figured out one of the things that may help account for some of the added efficiency. If you look at InsightCentral, there's a radiator block modification that people have used to deliberately raise the operating temperature up to the 200-203F range. If memory serves, lean burn is reluctant to kick in at temps below 197 but entirely willing over 200. Memory serving is a big if though- it's been a while. But the grill block may give more than just an aerodynamic advantage in the case of the Insight. I have a very fuzzy memory of reading somewhere that the later Insights may have been programmed to be even more cautious with lean burn for some reason, so the 06 may be tough to push into the lean burn zone. Definitely check InsightCentral for the details though.