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Discussion Starter #21
How Important? Very important.

I installed the panels late last week. Driving the same route as I have been, I am experiencing an incremental increase around 4-5mpg. I am pulling down 70 mpg with a CVT. Not too bad!
 

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Body shops have a system for fixing minor damage, including holes, in plastic bumpers. According to the shop manual, the bumpers are polypropylene, marked with a PP stamped on the part. Other possible symbols are GTX, PAMXD6~G+T, ABS+PA6, E/VAC, ABS, AES, and PC. It doesn't show the underbody panel on the picture, but if you can find out the plastic type a body shop might know what sort of kit is needed to be compatible with the plastic...
 

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I can't talk about the underbody panel itself, but like the earlier poster said, everything counts.

I had lost the driver side "air dam" that sits in front of the tire, and also the inner fender. (I hit some road debris...)

I've been doing some long distance commuting (700 plus miles each way) on Interstate 80. With the damage, my mpg was hovering around the 50 mpg number. Once I replaced them I slid up to the 60 range. This all at "highway speeds"....

(I also pulled off a 70 mpg trip, but in that one I kept my eye on the display the whole time, drove in the Carter speed range, and despite teh weather, kept my a/c off. I ain't doing that again).

Oh, a picture of my mileage display on that last trip:
http://www.panix.com/~dannyb/images/mich-to-nyc.jpg

(2001 CVT)

I do not have any air dams, and no panels under the engine. Is this really possible to jump from 60 to 70MPG? This may be the reason why I can only max out my MPG on the highway in the mid 60's.

When I push the car hard at 65MPH and higher, I only get around 55MPG average.

Some people say here 1%, while he says over 10% difference. What should I expect on full highway miles. I like to drive fast in the insight, like 70MPH, so maybe it is a must for me to get those under body panels at those speeds.
 

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Having just installed the right side under body panel for the engine [ $40] the only difference I noticed was a bit higher intake air temperatures for my very simple hot air intake modification ducting added earlier once the panel was installed . The intake draws off the catalytic converter heat shield and the panel must have quietened down some turbulence and outside air circulation i guess.
Didn't notice any change to coolamt temp via the Scangauge from the addition of the previously missing panel. My mileage following installation actually went down on the first long highway trip at speed after the panel was installed, but not because of the panel.

If you're going fast, no doubt every little bit will help somewhat; but to pin down how much benefit accrued to economy as a percentage will be washed out by variables such as tires, temperature, traffic on any particular day, and wind speed, especially in winter with denser air. That's stuff it would take a wind tunnel test to figure at a guess.
My rough estimate/experience is from 100kph to 110 kph there's a real hit to economy; ten percent faster, maybe 20 percent more fuel, to use round numbers. It's a square of the velocity type of thing.
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A major reason I installed the missing underbody panel, was not only for the aerodynamics and completeness, but also because of the deep snow anticipated in coming months that can pack up under the car; melt; freeze; drop down in nasty ice chunks; throw belts; wreck seals!; and worse.
[It may be a moot point for many without deep snow, but I had real bad luck with another small low ground clearance vehicle where similar under engine panels had been removed. [Done at the urging of a good mechanic 'to keep the car running cooler' in summer and save me 'a bunch of problems']. Ya,..True, :) but: ...
Result in Winter: two new serpentine belts; replace bent crank pulley; replace crank seal damaged by a thrown fouled belt; a rebuilt alternator, due to oil-up and short-out of original; hrs of $hop Time; Loss of Use x2; Aggravation 2x+ .. all from snow packing up where it shouldn't go, forming ice and then melting and falling into pulley belt mechanism because there was no plastic panel to prevent debris from getting up there in the first place! 'nuf said. :( rant/]

There's a pulley very low down that could present similar grief in the Insight.
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[complete parts list uk/us pricing see: front fender]
If you do decide to order a set of panels #12 #17, the one clip [#36] that attaches to the front of each side of the panels to the horizontal aluminum part back of the bumper must be ordered as well; there _is_ a clip [#26] attached with the panel that a 6x16mm 1.25???pitch [best check pitch!] 10mm headed bolt passes though.
fwiw??!: The other four 10mm headed one piece washer-bolts are 6x20mm long with the same pitch cost $2.40/bolt from Honda.
The four 6x20mm 10mm washer-bolts were Insight specific and special order out of Japan = ~4 wks.
[..a metric nut and bolt supplier will have bolts and separate washers to accomplish the same task for much less with no waiting.]
 

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AbCARed00: Thanks for the detailed post. I totally agree with you about getting it for the winter snow. The way I figured was all that salt and snow kicking up into the engine can not be good for all the steal parts around the engine.

Is your car missing the Air dams in front of the tires? These I would think make the biggest difference with MPG, as I read these were specifically designed for Aerodynamics. These would probably help MPG much more than the $40 dollar panels you replaced.

I'm going to take some detailed pictures of the under body of my car so that I can find out exactly what I will need. It seems that there is a metal bracket bent at the very bottom, I think this would be a #10 Beam, Cover.

Plus I have other problems, like the bumber holes that hold in one of the underbody panels has been completly torn, so it is not a complete circle anymore and the clip will not work with it. I will have to figure out how to get all these panels back on.

I have been looking for used body panels but they seem to be almost impossible to find. I think it will cost me about $350 to get the body panels new and I just might order them then wait around for used panels.

Maybe if you or someone else could take detailed pictures of what it looks like under your car that would be helpful for me to figure out what I will need. It is hard to find Insights around that I can actually look at underneath.

I already replaced the cover around the passanger wheel with a new one.
 

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Windycity - what town do you live in, and what town do you work in? I live in the far nw burbs, Woodstock, and commute to Barrington, and can only manage low 60s with my commute in a CVT. How fast do you drive? I usually do the speed limit, not over, not under.
 

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Is your car missing the Air dams in front of the tires? These I would think make the biggest difference with MPG, as I read these were specifically designed for Aerodynamics. These would probably help MPG much more than the $40 dollar panels you replaced.
No, I've got the air deflector strakes as seen in the image linked here. The left side strake is seen from the back under the car similarly here where the thumb is pointing. Note the holes at back of the strake.
Not sure on what numbers add up or relative importance etc. Like said it works in concert. I'll bet those strakes reduce lift a tiny bit due to wheel rotation at speed.

I'm going to take some detailed pictures of the under body of my car so that I can find out exactly what I will need. It seems that there is a metal bracket bent at the very bottom, I think this would be a #10 Beam, Cover.
That would be great.
My vehicles cross brace to mount the rear part of the front underpans is bowed a bit up as well; maybe a design feature or maybe just nerfed over the years, don't know, but it's bent up evenly both sides and not pushed back.

Plus I have other problems, like the bumper holes that hold in one of the underbody panels has been completely torn, so it is not a complete circle anymore and the clip will not work with it. I will have to figure out how to get all these panels back on.
May just need a bigger washer, or maybe a strip of flat aluminum or stainless steel etc to bolt to the polypropylene underpan. If you can trap the better part of the plastic likely no worries if it's open one side but ...
Not sure if polypropylene can be patched effectively with a donor chunk from something else that is "PP" but a metal strap and a few bolts, washers and nuts would be simple.

I have been looking for used body panels but they seem to be almost impossible to find. I think it will cost me about $350 to get the body panels new and I just might order them then wait around for used panels.
Seems I got a break on the price at the big Honda dealer here; the UK site says 2x price i paid locally. It was available 2 days later in Ab Ca here.

Maybe if you or someone else could take detailed pictures of what it looks like under your car that would be helpful for me to figure out what I will need. It is hard to find Insights around that I can actually look at underneath.
Best I can do now for the back panels without a pit and just some plastic ramps is seen here from a couple images in from when I put in the front underpans.
The perspective is a bit off in the image of the two front underpans side by each, but, if you do a DIY version and get enough depth in the fabbed up pan to clear the pulley on the front right side underpan you should be ok I would hope. I'd considered it but dealer price was good here vs. importing, customs, shipping, possible delays and other hassles.
If I was doing them as copies, if not using coroplast sheets, i'd try cannibalizing some second hand plastic
snow sliders![new portrayed, i'd go for garage sales material] which may be much more durable, easy to work, and already have an indent and good reinforced edges. Just a thought.
 

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I would say the answer to the question of "how important are the under-body panels" can be answered by:

--- how often are you on the freeway?

The faster one drives, the more important the panels are.

I would estimate that the panels are good for about 5 mpg at 55 mph and up.

Jim.
 

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I took some pictures of my car. It was raining out so I could not really get great pictures, may redo them. But you can see what I am dealing with, with absolutely no under body panels and also the holes that hold the panels on are ripped.

Here is the link to my pictures.
ImageShack Album - 32 images

What I am wondering about is where do those panels #5 & #7, go? Am I missing those? The link is here for the #.
Large Image for - 2000 HONDA INSIGHT FRONT FENDERS - Honda Parts from Lings Honda

Are the holes in the bumper that hold in the air dams broke, or are they cut like that normally?

Can you determine anything else by looking at the pictures of my car? Why do you think I am missing all of my panels? Do you think they got all ripped off at the same time?

I also noticed that my front bumper is a bit loose. Do you think this is because of the lack of support of the under body panels?


EDIT: I also wanted to piont out, in this picture below, there is a bracket you can see at the bottom of the radiator (or that metal below the radiator). There are 2 of these brackets. I think mine are actually bent up. Looks like previous owner bottomed out on something. Do these brackets hold the body panels on? This would be #2 in the bumper category, based on your UK numbering or in this link. http://www.hondaoriginalparts.com/honda_car_parts_large_image_C50.php?block_01=17S3Y01&block_02=B__4600&block_03=19733

http://imageshack.us/photo/my-images/715/dscf3588t.jpg/
 

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What I am wondering about is where do those panels #5 & #7, go?
I'd be guessing but possibly behind the bumper in front of the rad apron???, I did not notice these on my car when down there. Looking at some wrecked cars in the knowledge base may show some of the part in question exposed but it's hard to tell.
My rationale for thinking it's behind the plastic bumper is as there is a large fastener at the front of 5/7, and a square hole in the lower part of the front of the 11/16 parts [that ties the plastic wheel tub to the lower engine panel at the edge].

Are the holes in the bumper that hold in the air dams broke, or are they cut like that normally?
Can't tell from pics, just an opinion here, but if there are tears in other front sections of the bumper, maybe it's broken and pulled out. If the holes there are symmetrical on both sides i'd say it's likely normal, but otherwise likely not and broken at a guess.

The bracket mentioned in the [edit] is for the rear cross brace for the underpan panels if not mistaken.

[EDIT: was mistaken, wrong end !
I see what you mean now, for the front lower bumper.
Perhaps can you straighten them in a vice or with a hammer and block?]

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I see what you mean re: quiet a lot gone there from what appears could have been an off road excursion. Since it all tacks together one part to the next that would explain a loose bumper if fasteners there have not been additionally compromised from the damage.
 

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The panels make little if any difference for mpg, I know as mine were off for about 6 months. What they are most definitely good for is protecting the engine bay from debris, water, etc. and possibly holding in heat in the winter.

Instead of replacing the lost panels with stock panels do what some other users have done including myself. Get a sheet of high impact abs or aluminum and make your own under body panel.

http://www.insightcentral.net/forums/modifications-technical-issues/20269-work-progress-diy-under-panel.html
 

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Can anyone find a good diagram of all the underbody panels? I know I am missing the main one under the engine - but can't figure out if there is just one giant one up front, or a couple side ones that I am missing as well. I'm also unsure about the rear/side panels...
 

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Interesting viewpoint @AbCaRed00;

I was planning on pulling my underbody panels off for the winter, as I've already ripped one off and repaired it going through a deep puddle at speed, I figured having them on when trudging through 6" of snow seemed like a bad idea.
 

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Porshuh: in that post just above yours, there is a link in there to a thread on this forum that has many detailed pictures of under the car. It will have what you are looking for.
 

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I was planning on pulling my underbody panels off for the winter, as I've already ripped one off and repaired it going through a deep puddle at speed, I figured having them on when trudging through 6" of snow seemed like a bad idea.
I hope it may save some grief, in addition and not initially mentioned, as the plastic panels would not have prevented it, ...but the oil pan on that vehicle was dented, because of the very uneven rutty road surface, and oil pressure light showed up on idle. What a mess.
Had to drop that car's steel oil pan and bang it away from the oil strainer pickup point.
I'd worry in similar circumstance the magnesium alloy oil pan on the Honda Insight needing replacement or tig welding due to fracture.

All the more towards Uhtrinity's comments on a strong underpan design linked in his comment. Great suggestion if you have to travel in rough road conditions by necessity.
In sport, I used to ice race small cars on frozen lakes and mounting the plowed up icy snow banks around the road course was not uncommon. We used a 2-3mm thick aluminum underpan sheet fastened and suspended with a couple large bolts up front to the rad apron and two J-shaped curled steel 1" wide straps about 6" or so long in the rear, mounted to the chassis 'frame rails'. The latter j-hook type straps were for a bit of flex so not to dent the sheets too easily if mounting the snowbanks going off-course which happened from time to time.
Underpan materials could be obtained from salvage yards or brand new thicker gauge aluminum stuff could be got from a place called 'the metal supermarket' which was a good source. [ US, Canada, UK locations]
Some guys with industry access used cut up old multi-ply rubber conveyor belt sections as air dams in front, and also under the cars. These were bolted directly to the bumper and under body using large washers.
 

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