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Well, I went out last week and got all the materials I needed to change all the fluids and consumables on the insight and figured this morning was a good time to change everything out.

First thing I noticed when I put it up on jack stands was the underbody panels are remarkably easy to remove and looks fairly easy to replace. This definitely was not the case with my STi.

Secondly, there is a fairly large gap in the middle of the engine bay in between the two panels that connect to the metal skid guard. It appears to me that this is either the hybrid motor or transmission. I didn't look to hard at it since I was noticing so many other things. I would think that placing a piece of plastic down there would help smooth things out a bit more.

Thirdly, There are two fans that are much easily seeable from underneath. Now correct me if I'm wrong but I was under the impression that the radiator did not span the whole length of the front grill. If that is the case then Its most likely a fan for the AC condenser and since I never use the AC I'm thinking that I could completely block off this area with a block to further reduce drag.

Fourthly, the Windshield fluid reservoir is HUGE. Now I know we're only talking roughly 8-9 pounds here when it's completely full (assuming its a full gallon and the weight of the container) but cutting that in half would be an almost 5 pound reduction in weight. Heck, take it out all together (although this is a commuter car not a racecar) In racing simple things like this when put all together added up to a lot of weight reduction.

On to the air intake...

I've always wondered why the intake was designed like it is on the insight. It seemed rather odd that it made a 180 degree turn and ended up with an opening in the engine bay. I could only assume this was to draw in warmer air to help with the AS function of the car.

Now heres the interesting thing. I've read all about the warm air mod and the only reason I haven't done it yet was because (coming from a sports car background mind you) all of the solutions provided seemed to look like massive restrictions in the intake track. Now I know most of you might say "this is an economy car, not a performance car"... But the same principles hold true. The ducting that is commonly used, which looks like heater ducting, looks like it not only unnecessarily increases the intake track length but imposes a large amount or turbulence with would greatly distort the laminar flow through the intake.

Another thing I noticed is what appears to be an intake silencer that runs down from the 180 degree elbow and is nicely situated right up in the front bumper. One of the first things that pretty much all STi owners did was take this out because it restricted airflow, weighed a ton, and basically served no purpose other than making the intake quiet. Now it doesn't look that big to me but it is weight non the less and its sitting there looking useless.

Here's what I'm thinking:

Remove the resonator and silly front intake and basically turn the 180 degree elbow around to pull air from behind the engine. Obviously I'd have to come up with someway to block off the connection thats in the middle of the elbow once I remove the resonator since if I turn it around the opening will now be on the top and that would not be good.

Once its turned around its more or less a straight shot to the cat for a warm air intake. The only concerns I have is increasing the intake temp too much and the only way to monitor that is with a scan gauge (does scan gauge 2 monitor intake temps?)


I don't have a camera here, but I'll get one from my parents house if anyone is confused to what I'm actually talking about. Coming from a racing background I can see tons of ways to improve aerodynamics that would be extremely cheap and some area's that can have some weight removed to further increase mileage.

You point out some interesting findings.

I look forward to hearing more about your intake modifications and seeing the pics.

Ok, since my block heater didn't come with instructions I'm going to post it here just incase someone else is looking for install directions.

http://www.cheaphondaparts.com/shop/instructions/

lists pretty much all honda accessory installation guides.

I'm almost done with maintenance and then I get to play around a bit. I'm going to drive to my parents house while road testing to make sure there are no leaks and everything is working fine and grab their camera.

I'll take some pictures of what I'm talking about.

Hi Cary:

___Forget everything and I mean everything you know about performance tuning. The Insight is a lean-burner and holding it in its sweet spot for highway travel is a must for maximizing FE. For around town, you can P&G as long as you know you SoC action and its limitations both during and afterwards.

___The Insight's air intake is behind the radiator and that was indeed planned. Adding a 2” hose back to the CAT doesn’t restrict anything in your little beauty because you are drawing so little air to begin with. Darn thing could probably run in lean-burn off a straw let alone that plastic pipe through the resonator it is currently drawing through.

___As for real world performance, it doesn’t really help in the summer but in the winter, a non-WAI equipped Insight is lucky to see Lean-burn below 32. With the WAI installed, I have seen it as low as 0 degrees F but it is not very strong and very short-lived. I will take that over none without a WAI and Radiator block.

___Good Luck

___Wayne

You know, I didn't even take that into account. Your completely right about the amount of airflow going through the intake when cruising.

I am however still curious about the second fan and the fact that the AC condenser runs the length of the front grill. I'm thinking it will be possible to completely block off that area for reduced drag and then in the winter/colder months put in the normal radiator block.

Now I just need to get a scan gauge so I can keep track of engine temps so I can play around with blocking off the lower grill and having a radiator block.


While I was underneath the car this morning I noticed a gap from the front underbody panels to the middle of the car. Basically the area where the front suspension resides, it looks like there is an unnecessarily large area left uncovered. Now, I'm sure it was to ensure the suspension had the necessary room for complete travel, but I'm wondering if it also has to do with the airflow coming out of the engine compartment into the wheel wells.

I'm going to put some tufting around that area and hook up my remote bullet camera to record that area at speed. I'm thinking I can put some small covers there, cover up the hole thats left in the center of the front cover and possibly smooth out the transition from the middle body covers to the rear bumper.

I have access to plenty of thin gauge aluminum so I might even mock something up to cover the exhaust as well, but heat might be a concern there. Not sure...

My mind is running circles :)

Heck, I've even toyed around with the idea of going sans side mirrors... although I'd have to put them back on when I got it inspected...

the flip-over warm air intake is what i did. a prestone antifreeze cap will fit in the hole in the rubber intake elbow. looks tacky, but who's to know? and my scangauge shows about a 20 degree rise over ambient once the engine is fully warmed up.

the other nice thing about moving the intake to the rear is that you can reach the oil filter from the front of the engine bay. just put a amall tupperware container under the filter to catch the oil. after you let it drain for a few minutes, remove the filter, put the top on the catch tub, and you can remove it at the 90 degree angle it requires without spilling the used oil all over the place. that and a fumoto quick-drain on the sump (with drain hose), reachable from over the top of the engine, and you have a 5 minute, no mess oil change.

Thanks for your data on intake temps. Now out of curiosity did you happen to check it while it was in the stock position? Trying to make sure I'm not making things worse by fiddling with stuff.

One thing that I was thinking about was that the end of the intake tube lies behind the air conditioner condenser and not behind the radiator. It would seem logical to me that if honda had placed it there to receive warm air they would have put it behind the radiator... Maybe just shortening up the tube (although that would be non-reversable) would provide an increase in temps. Most likely it will not be enough to sustain lean burn in cold weather.

I'm going to cut out some templates today in cardboard to start playing with my ideas of more underbody aero. I want to test fit the shapes before I start cutting on aluminum. I'm thinking some thin flashing will be sturdy enough to not deform while being not suseptable to melting/catching fire or weighing too much. I want to basically make the entire undercar flat which means covering up the rest of the engine compartment and exhaust system. Smoothing the transition from the rear of the car to the bumper looks like an area that could use some major work without being a huge pain.

I'm thinking with the removal of the mirrors, radiator blocks, smoothing up the underbody and removing the radio antenna there is some gains to be had interms of drag. Now I wish there was a quantifiable way to measure the reduction in drag that was free from other variables.

Hi Cary:

___There is a small amount of fuel to be saved with reduced air drag of course but you may be taking increased FE with HW mods in the wrong way. Dropping the Cd of an insight from .25 to .23 (Billy has the mirrors removed from his with an internal vid for side/rear views) might allow a .2 - 2 mpg increase at far faster speeds then you would receive decent FE at anyway and nothing at lower. For the big numbers, running lean-burn in 4th and 5th between 35 and 57 is where the magic happens and that is with a bone stock Insight. They are already slippery as a bar of soap in the shower so why not work on your technique and maintaining Lean-Burn first and foremost during highway cruise. The Insight is one heck of a fuel miser in its own right and other then a radiator block and WAI mod in the late fall, early spring and winter, Mobil1 0W-20 and pressing your RE92’s, the rest is doing a lot of work for a far smaller gain then you may have thought previously. Hypermiling an Insight is all about patience rather then mods … The same could be said for the any of the other vehicles we drive daily as well.

___Good Luck

___Wayne

I enjoyed driving Chucks Insight lastnight. Given some real seat time. Im sure I could get insane mpg out of one. When you hang that thing in lean burn some real magic happens!

I completely understand exactly what your saying Wayne and I whole heartedly agree that modding is extremely overkill when such good results can be attained in stock form. I guess its the modder mentality that comes from years of racing that I find it extremely difficult to not do improvements to vehicles... even if it means hours of work for minute gains.

But thats where the beauty of it comes. I could be mistaken here but I believe adding (at least up front) more aero panels underneath will have the added effect of keeping heat in the engine compartment, making it easier to stay in lean burn.

I definitely have a lot to learn about hypermiling... At my best, without using P&G, I can get around 120 sustained MPG on my commute from my house to my parents... its just the trip back home where I slide back down to 75ish. That combined with the extremely short distances that most of my trips are (where I typically average ~60mpg), I don't think its feasable for me to have a tank average over 80. I'm pushing myself really hard to try and get this tank over 70 mpg, and so far its going well.

Maybe with more practice and when I (hopefully) get a MIMA so I can FAS safely I'll get the numbers much higher.. but until I have a bit more confidence with FAS manually, I'm going to stick with not doing it when I'm around other cars.

I wasn't real impressed with MIMA. The fas mode was nice. But truth be known I can key kill faster than button kill. The hard regen would only seem useful coming down Pikes Peak.

If I only had not been put into a position to renig on my Insight purchase.... GRRRR...

I think a good mod to a Insight would be to strip all the hybrid stuff off and then lean burn the thing into the ground.

JMO

Alrighty, got bored last night and decided to start doing some math on total drag calculations trying to find ways to possibly increase fuel milage for the insight. The results were not unexpected but to the extent they were suprised me a tad.

Note... all frontal area figures are in square feet

Frontal area for side mirrors :
Conservative estimate: 0.23611 per mirror
High end Estimate: 0.31944 per mirror
Average: 0.27777 per mirror

That leaves me with a reduction of 0.555555 square feet of frontal area if I remove both side mirrors

Lowering the car (note, I could have this all wrong but I'm assuming the space from the ground to the bumper is considered included in the frontal area)

1" drop: 0.463194
1.5" drop: 0.694791
2" drop: 0.926388

So what does this mean... it means that removing the side mirrors has almost as much effect on the frontal area of the car as lowering it 1.5" inches. Now, I'm not even sure it would be feasable to lower the car much more than an inch or an inch and a half. But lets assume that were going to lower the car 2".

Cd reduction:

Lets assume that if I remove the side mirrors, radiator block, make the underside of the car completely flat, remove the radio antenna, use clear tape to seal all body gaps and fabricate some front wheel spats that actually work I can reduce the Cd of the insight to .2 (I think thats probably generous)

Total drag reduction:
From taking the above measures I could theoretically lower the total drag area some.

Stock Insight Drag area: 5.10
Theoretical modified drag area: 3.79

Now that is a decrease in drag area of 1.31


Thats pretty substantial but gains at lower speeds will be minimal. I'd figure out the gains and graph them on a chart but I'm tired as I just got off work.

I'm excited to see a motor head/car crafter on this site. I look forward to read about what you do. If you get rid of the side mirrors, consider adding rear facing cameras. I suspect that weight is the biggest place to start, but that is just a guess. The old addage that went "to gain spped, add lightness" could be modified for better MPG.

Oh certainly so. I've always believed that the most gains in lap times I ever saw in my STi were the result mostly of three items. Two of which have an impact on FE, albet one in a completely different way.

Tires, Brakes and Weight. I can remember going out on VIR's south course in my first subaru that had tons of horsepower mods but I was running on stock tires that had 15,000 miles on them and the stock brakes. All I can say is ~300ish HP with crappy tires and even crappier brakes makes for a scary day.

I learned when I got my STi that suspension, brakes, tires and weight = safer and faster than HP mods alone.... But that didn't solve the bug for high HP. I ended up with around 500ish to the wheels before I sold the car. Which was more than enough power (when you got enough HP to smoke all 4 wheels in 1st - 3rd it gets scary fast)

As for weight modding, when helping to make a friends rally prepaired subaru we ended up drilling holes in lots of stuff and removing basically everything that wasn't needed for the car as there was lots places where improvements could be made.

It doesn't look so much like thats the case with the insight. I've been searching without much success for large weight items that could be removed or replaced with lighter weight items. With a car only weighing 1,878 pounds to begin with (5-speed with AC) theres obviously only so much you can remove.

I've always been anal when it comes to weight since it affects so many things... Acceration, Braking, Handling, Fuel Mileage, Load Capacity, Ride Comfort... The list goes on and on.

Sadly, adding more underbody aero will add weight, but using thin gauge aluminum should be the best bet since that will weigh the least and still actually be feasable. I'm not going to be making carbon fiber panels just yet... (to much money for such little return on an already light weight car)

Speaking of carbon fiber and light weight cars.... I was at VIR a couple years ago and there was a guy there with a lotus elise that he had turbo-charged and replaced every single body panel with carbon fiber. He was running without a passenger seat even. Hah! I asked him what he thought the weight of the car was and he said roughly 1,600 lbs. I found that a bit hard to believe since thats around a 300 lb reduction in weight from the elise but I guess its possible.

Also speaking of reducing weight.... Could you imagine if you took out all the hybrid related stuff and just ran it as a gas powered car... I bet all that stuff easily weighs 300-400 lbs. That would be huge combined when striping everything else out.

I need to start writing all the stuff I take out of and put into the car to keep track of everything incase others want to do the same. I have access to a nice four corner scale system thats accurate to 0.1% which for my insight is 1.878 pounds. Close enough ;)

I'm going to make a list of area's where I think there could be signifigant weight savings ( > 3lbs) and try to weigh them all. It should be intresting how much the muffler weighs. I think the fact that we have a resonator and muffler is completely unnessacary to have both. I'm going to pick up a lightweight muffler and cut out the resinator and muffler for further weight savings (plus possibly an increase in HP)

I haven't forgot about this thread... I've just been really busy with work lately. I'm underneath the car right now taking measurements and I'll be cutting out some panels tommorow sometime.

The more I look at the exhaust system, the more I want to take a cutoff wheel and cut the pipe right off after the resonator.... I'm sure it would be too loud but I'm sure I can find a decent muffler thats not too loud and just truncate the exhaust right after where the resonator ends... (replace the resonator with a muffler and exhaust right under the car.

One thing I'm curious about is routing the exhaust directly under the car might disturb the underbody airflow. I might just do away entirely with the resonator and just make a exhaust thats as straight as possible to where the stock muffler is and route the exhaust out the stock location...

Decisions decisions :)

Hi Cary:

___I do not know if this will help you or not but here are a front and rear underneath pic(s) of the Euro 5-door Civic. The underbody panel(s) cover almost the entire underbody from front to rear … Sorry about the quality as they are not the best?

http://www.cleanmpg.com/photos/data/523/2007_Civic_iCDTi_Hatch_-_Front_-_Full_length_aero_underbody_panels.jpghttp://www.cleanmpg.com/photos/data/523/2007_Civic_iCDTi_Hatch_-_Rear_-_Full_length_aero_underbody_panels.jpg
From the front------------------------------------------------------------------From the rear.

___Good Luck

___Wayne

wayne,

wow... very interesting... I guess those pictures ease some fears I had about heat related issues from covering up the exhaust. If honda can cover the exhaust with those plastic panels and I can for sure cover them with aluminum flashing.

I wonder what the intake looking slot in the first picture is for...


While taking measurements in the back I noticed that the rear brake lines run very close to the center of the car with the suspension is at full extension (car was on jack stands) so that limits the panels width (at least what I feel safe doing) I don't want to chafe brake lines :)

What this does say to me now though is that i can basically make one (or two for access reasons) long panels for completely cover the midline of the car where the exhaust runs.. yay :Banane42:

Cary,
Have you done the hot air mod yet? I've ran it as you described for about 3 years and it helps a lot. I have the rubber tube flipped over and slipped in a piece of 2" flexpipe ran back to a shroud on the upper cat. I bent a cat shroud out of a piece of aluminum house flashing. It makes a 5 to 10 mpg difference in my 50 mile one way commute. I left it on most of the summer as well. I saw IA temps as high as 138. I pulled the rubber intake tube loose from the flex pipe this summer when we had a few weeks of 100 temps. If you haven't done it. It is a quick, inexpensive mod that will make great gains.

If you don't have a Scangauge, get one!! It's invaluable for instant monitoring of many engine parameters. Hot air and high tire pressures and the insight will roll on (almost) imagination.

LOL everyone keeps calling me Cary...

Cary is the town I work in :) Blake is my name. (I like to call people by their real names... but I completely understand the screenname thingy ;) )

I have done a WAI and pretty much exactly as you described. I am a little bit concerned with the way the high voltage cable gets pinched on the frame of the car when I route it over it and how it appears as the intake tube will get chafed if I route it under it...

I made a chafe guard out of the aluminum flashing I have and its working so far but I think I'm going to have to come up with something a bit more non skechy.

I don't have a scanguage yet, but thats on my list of things to get.

It rained here the other day (finally) and I was shocked to see how much rain affects the fuel milage. On routes where I can average over 100mpg easily I was struggling to average at least 70. There might have been other contributing factors but I could definitely feel the rain slowing the car down. Using ridge riding helped some.. but it was still very noticeable.

Off to work! I hope to have those panels made tonight and I can start test fitting and playing around with cutting off the exhaust.

First set of aero panels are made and waiting for the paint to dry. I have a couple more area's I'd like to clean up but I'm going to wait until I finish with the exhaust mods before I close in that area.

In total I made four panels to cover the small rectangle towards the front of the car (basically the hole in the aero panels where the oil pan is)

Left and Right side of the car after the front panels leaving the exhaust area open. These panels are basically where the wheel wells are. There is a section left open from that area until the middle of the car.

Finally there is an area from the end of the middle panels to the bottom of the trunk thats left open.

I'm trying to find a camera here at my parents, but they are out of town and it looks like they took the camera with them. I took plenty of measurements and made cardboard templates before I made the aluminum flashing final versions. As soon as I find the camera I'll post some pictures up.

Blake