Honda Insight Tail Extension Project

[3-Wheeler]

Originally Posted by aerohead

Daox,were they hypermiling,or just driving down the highway at a reasonable speed,say,100 km/h ?
Honda has extremely good quality control from car to car,and on coast-to coast runs with
fleets' of cars,they return virtually 'identical' performance.
It's hard for me to wrap my brain around a 30-40 + mpg variance between like vehicles.
If that's what they can do,it's great,just hard to explain and to design around.

Hi Aerohead,

Daox is correct. Although even with the under-body smoothing panels, I have not gotten over 100 mpg during "normal" driving.

The best I got with the car at 55 mph, was 87 mpg on a 95°F day with my Mom and I in the car, over a stretch of 150 miles or so, on reasonably flat roads.

When hypermiling to work, the best on a 33 mile loop was 117 mpg, again on a 95°F day.

So, will I get over 100 mpg with the extended tail? We shall see, but I would expect a gain like Metro's.

Jim.

[SVOboy]

Finally got a change to read through this thread.

Great work

Looking forward to more updates.

[aerohead]

Originally Posted by 3-Wheeler

Hi Aerohead,

Daox is correct. Although even with the under-body smoothing panels, I have not gotten over 100 mpg during "normal" driving.

The best I got with the car at 55 mph, was 87 mpg on a 95°F day with my Mom and I in the car, over a stretch of 150 miles or so, on reasonably flat roads.

When hypermiling to work, the best on a 33 mile loop was 117 mpg, again on a 95°F day.

So, will I get over 100 mpg with the extended tail? We shall see, but I would expect a gain like Metro's.

Jim.

Thanks Jim,
it will be hard to sleep until you finish and have a chance to test!
With your direct injection engine at high load,and tasty factory Cd,87 mpg sounds very realistic.
My hope is that the EFI is smart enough to maintain the great BSFC after streamlining,when the engine will be operating at lower load.
The Chrysler Airflow showed a significant gain with its 'long-tail' variant,I have to believe that you'll experience a similar gain.There's just too much data in the public domain now to suggest otherwise.
I,along with no doubt many,many others,are rooting for both you and Robert,awaiting the super slinky Insights as they strike Tropos-fear along the highways.

[jime57]

Originally Posted by Daox

People have already broken 100 mpg on a tank of gas in the insight w/o mods. Its completely doable.

In my effort to establish a repeatable FE baseline for my Insight I have made three roundtrips on my "test" course on I64 and I95 around Richmond. Those three trips netted 102.4, 99.4, and 101.6 mpg at a target speed of 55 mph. I wind up with a variation of around 8-10 mph in order to stay almost totally in lean burn. The course is 48.1 miles RT. I never shut off the engine during this tests, since that variable would be difficult to control. My only mod is a full block of lower radiator opening. Upper opening seems adequate according to ScanGauge data.

I think that though the Insight is not much lower in Cd than the CRX, it has a more efficient engine.

[jime57]

Originally Posted by aerohead

Daox,were they hypermiling,or just driving down the highway at a reasonable speed,say,100 km/h ?
Honda has extremely good quality control from car to car,and on coast-to coast runs with
fleets' of cars,they return virtually 'identical' performance.
It's hard for me to wrap my brain around a 30-40 + mpg variance between like vehicles.
If that's what they can do,it's great,just hard to explain and to design around.

Go here to see the actual mileage logs for the CleanMPG folks:

CleanMPG, - Garage An authoritative source on fuel economy and hypermiling

Scrole down the page to the hybrid section to see the long term logs for several Insights. These folks ARE hypermiling - some actually pulse and glide - and since there is little control of condition and terrain, then the results vary quite a bit. It is just their everyday commute or drive. But these are "tank" averages over a long term. Short distance controlled test runs should deliver significantly better fuel economy(FE) than any of these reported results.

FE for the Insight is highly variable and depends greatly on speed, terrain, driving conditions, and operator driving skill(particulary the skill at keeping the engine in lean burn). This is one reason I have gone to so much trouble to find and scope out a 2 way test circuit that is not too hilly and will be repeatable to a high degree. I addressed this earlier, but my baseline FE for my course, in the late spring, is very close to 100MPG at 55 MPH, constant lean burn. 100MPG in warm weather, under test condition is an achievable baseline for aero testing. It could be even better if one has a flat test circuit.

[jime57]

I may have to do a bit of backtracking on this FE issue Right after I posted, I went out and ran a test at 60 MPH target, actually achieving 58 MPH average with the turn-around, and it sure looks like the Insight really hits a wall going from 55 MPH to 60 MPH. The FE dropped from around 100 MPG to about 90 MPG, using the same test course and driving technique. It looks like beyond 55 MPH is a wall of air for the Insight. I hope to make another test drive tomorrow morning to gain more "insight" I have removed my lower grill block, for state inspection, but that wouldn't seem to explain the rather large difference in FE.

If this is indeed the case, then there is going to be a strong benefit from a good boattail.

The CleanMPG data that I referenced above is mostly by hypermilers, including mine ordinarily, though I do not pulse and glide. I simply drive fairly slow and am careful to maintain lean burn. The ordinary hybrid features like autostop and regeneration do help slightly.

More to follow

[RobertSmalls]

There's 16% more aero drag at 60mph than at 55mph, and you had an 11% increase in fuel consumption per mile. That sounds about right to me. You don't really hit a wall until lean burn fails at 75mpg, a little over 65mph.

[aerohead]

Originally Posted by RobertSmalls

There's 16% more aero drag at 60mph than at 55mph, and you had an 11% increase in fuel consumption per mile. That sounds about right to me. You don't really hit a wall until lean burn fails at 75mpg, a little over 65mph.

Robert,
dropping below 75 mpg above 65 mph sounds like a nice problem to have!
Perhaps Steven Chu will turn a glance when the new tails hit the asphalt and the meters turn backwards at the pump.

[RobertSmalls]

Originally Posted by aerohead

Robert,
dropping below 75 mpg above 65 mph sounds like a nice problem to have!
Perhaps Steven Chu will turn a glance when the new tails hit the asphalt and the meters turn backwards at the pump.

Now that is one interview I'd be happy to give. Maybe I'll write a letter to his office once I finish with the project.

[deejaaa]

3-Wheeler, any idea on the weight estimate the extension will add?
i made an aerobed for my truck and i figure it weighed 150#.