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

[MetroMPG]

I did some A-B-A testing today on the U.F.O. (2000 Honda Insight 5-speed).



With five relatively simple aerodynamic mods/deletions (not shown in the above pic) ...

• partial grille block
• deleted passenger side mirror
• flat-folded driver's outside mirror (from a Suzuki Swift)
• deleted wiper arms: passenger side & hatchback
• deleted stock front licence plate bracket (flush mounted plate)

(List is in order of estimated effect of each mod on drag reduction, from most to least effective.)

I measured a 14% gain in MPG at 80 km/h / 50 mph: 94.6 mpg (US) vs. 82.9 mpg.

I tested the mods collectively: ie. the "group" of mods was in place for the "A" runs; reverted all mods to stock setup for the "B" runs.

Note: testing was done with the car's hybrid functions completely disabled. (Since I got the car, I've been driving it with IMA switched OFF to protect the near-dead high voltage battery pack from further damage.)

All of which means: those steady state MPG numbers simply show the advantages of a small, efficient lean burn engine + tall gearing + good aerodynamics! No electric assist was involved (which possibly would have made the numbers slightly better).

It's exciting to see how "expanding" the car's lean burn "envelope" can pay big dividends! (Moreso than these same mods done to a non-lean burn vehicle, I mean.)

I will report back with the raw data & some photos later.

[MetroMPG]

Weather, Sat., Sept. 24, 2011

Overcast / damp roads (not wet - no road spray; from light mist earlier in AM)

Metric units
Time ... C ... Humidity ... Dew point ... Wind kph ... Press kPa
14:00 ... 19 ... 89 ... 17 ... SW 7 ... 101.7
13:00 ... 19 ... 94 ... 18 ... SSW 5 ... 101.7

Imperial units
Time ... F ... Humidity ... Dew point ... Wind mph ... Press in.
14:00 ... 66 ... 89 ... 63 ... SW 4 ... 30.02
13:00 ... 66 ... 94 ... 64 ... SSW 3 ... 30.03

A: 2-wiper delete (1 front, rear); grille block; passenger mirror delete, driver's folded; licence plate bracket delete
B: stock config

Speed: 80kph / ~1728 rpm

A ... w ... 86.4 ... 89.0 ... 90.9 ... 91.4 ... 91.4
A ... e ... 97.0 ... 99.1 ... 99.1 ... 101.0 ... 102.2
A Average (W & E): 94.8 MPG

B ... w ... 78.2 ... 71.7 ... 75.9 ... 74.0
B ... e ... 90.9 ... 92.1 ... 91.1 ... 89.5
B Average (W & E): 82.9 MPG

A ... w ... 90.2 ... 90.4 ... 89.3
A ... e ... 98.7 ... 98.7 ... 99.1
A Average (W & E): 94.4 MPG
Average all "A" runs: 94.6 MPG

Standard deviation of all A runs (averaged bi-directional pairs): 1.5 MPG
Standard deviation of all B runs (averaged bi-directional pairs): 1.3 MPG

Difference of A over B: 11.7 MPG / 14 %

MPG readings taken by resetting OEM segment fuel economy calculator when passing a chosen signpost after getting the vehicle up to speed & stabilized. Final reading taken at a second signpost at the end of the route. (One update of the OEM display.)

Route: 1.6 km straight and flat section of smooth road, with no other vehicles ahead in my lane; occasional vehicles in opposite direction.

No cruise control. Speed was controlled by watching RPM instead of the digital speedometer readout, because the speedo gives no indication of rising/falling speed until the next higher/lower digit is shown. RPM has higher resolution.

[Cd]

That's incredible !
If it wasn't you doing the testing, I would have my doubts, but you are always meticulous about your testing.
Did I read those numbers right ?? Over 10 MPG ?

[MetroMPG]

Yup, over 10 mpg.

It was such a big change because the mods permitted the car to operate in lean burn 100% of the time at 80 km/h, where without them it felt like it was on the edge, moving in & out of lean burn at the slightest change in throttle position to maintain that speed.

In other words, the % change might have been less impressive if I'd tested at 70 km/h or at 115 km/h (either fully in, or fully out of lean burn for both A and B runs).

I didn't plan it that way, but it was interesting to discover. I tested at that speed because it's the highest posted limit on the secondary roads I usually travel.

[Otto]

1. What's that car got for an undertray "as is?"

2. Batteries: What's the cost to replace the stock batteries? Would something as simple as Costco marine deep cycle batteries work as a suitable replacement?

3. If you just took the batteries out and ran without them, approx. how much weight savings? Fuel savings?

4. What tires, tire pressure?

[Cd]

One of the first things I plan to do if I ever buy one of these cars is to remove the mirrors and replace them with something smaller.
How bad of a blind spot do these cars have without the passenger side mirror ?
I remember sitting in the car at the dealer when these cars were new and being turned off by the blind spots the car had compared to my Civic hatch, but can't recall just how bad that it was.
I have seen others remark about the blind spots on this car and I notice despite going all out on the aerodynamics of his Insight, 3Wheeler chose to leave the stock mirrors on.
How bad were the blind spots in your case ?

[JasonG]

This matches well with Basjoos' findings.
His mods allowed lean-burn at higher speeds due to less drag.
We need more Insights on the road........alas.

Pictures of the grill ?

[Sven7]

"After" pics?

[Daox]

Great testing Darin. Gotta love lean burn!

Originally Posted by Otto

1. What's that car got for an undertray "as is?"

2. Batteries: What's the cost to replace the stock batteries? Would something as simple as Costco marine deep cycle batteries work as a suitable replacement?

3. If you just took the batteries out and ran without them, approx. how much weight savings? Fuel savings?

4. What tires, tire pressure?

1) The insight has some undertrays, its not nearly a solid/flat surface though.

2) He'll be rebalancing and replacing parts of the pack if necessary. There is a pretty good thread by RobertSmalls that tell you how to do it. You can not use deep cycle lead acid batteries.

3) The entire pack only weighs 65 lbs. Fuel savings from removing it would be nothing.

[bondo]

It would be interesting to see what you could get out of your Insight with a boattail on it like you built for your Metro.

Here is a little more insight on the Insight. (you guys have probably seen this link already, this is for those who may not have yet.)

InsightCentral.net - Encyclopedia - Honda Insight Aerodynamics

Bondo