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364 Posts
Discussion Starter · #1 ·
Hi All,
I've only been a member for a short while though I've had
my '00 5 spd for over three years now. I have tried
various changes to the vehicle to improve it. Some helped,
some bombed and I changed them back. I guess this will
be my first posted mod to contribute to this knowledgeable
and enlightened group that I have the good fortune to be
a member of. This mod does work. Many thanks and
acknowledgment to cakley for his original thought and
inspiration. All I've done is to glean more info and take
it a step further. All suggestions for improvements from
my fellow members are to be looked forward to. Happy
to be part of the team. Oh well, here goes:
Did a modified cakley muffler mod to the '04 inside the
muffler. Wanted to do it in a way your average driveway tech
could do it without a welder and do it on the car. If your
going to do it you probly will want to clean the muffler (I
used brillo pad and soapy water. Then sand or file the area
your going to work on(easier done before). Took a while
since I had to cut the muffler wide open so we could get pics
of everything in there. I need to find a way to post them. As
the pics are over 1 mb each I'll try to find a photo album
sight (or other) where I can post them and link to, help
appreciated. Till then I'll post another message explaining as
best I can what's actually in there. I had the good fortune to
meet Willie(Little Red Rocket) at the time I decided to do the
mod. His advice was the best. If you want improvement you
have to take a chance and initiate change. So, if it doesn't
work I'm out 180 bucks for a new exhaust. Fortunately it has
improved mpg somewhat and testing is ongoing. There
are three chambers in the muff. The mod only needs to be
done in the third or rear chamber so work is minimized.
Basically, the tail pipe goes into the muff and continues on
to the first chamber. By observing where the tail pipe
enters the muff you can cut a three sided "square"
hole on the drivers side of the muff(I used a handheld 4"
grinder w/1/16" cutting blade). Two vertical cuts. One 3/4"
in from the rear surface (Note: rear surface is indented)
of the muff and 3" long. Second like the
first but 4" in from the rear surface. Third cut to connect the
first two at the top(creates a door). Bend the door down so you
can see and get to the tail pipe inside the muff. Make two
vertical cuts in the tailpipe 2" apart and remove the cut out
pipe(I used a Keyhole saw to make these cuts, Ace Hardware).

EDIT: 7/5/4 While in the muff would also cut the small end off
the restrictor. Checked before I closed it up and you can reach it
with the keyhole saw. WHY: When I mod'd the '04 I went into
the other side of the muff(pics) so had to mod a little different.
To reproduce mod as suggested here for ease and simplicity
had to come up with approximating same relief for other side
of muff. Testing so far is showing more relief may be necessary.
If youv'e already done the mod you can get to the restrictor
thru the opening suggested for the second tail pipe which will be
installed away from the exhaust in for less effect on reverse pulses.
DETAILS for second tail pipe worked out. It will be fully adjustable
for exhaust flow and relatively simple to reproduce. Since removing
the rear bumper or dropping the exhaust may be needed, those of
you interested may want to wait before cutting as much more
testing is needed. The Good Side: It does work. The mpg #'s so far
are heartening. Honda engineering made a high quality and fairly
elaborate muf(tuned, but restrictive, thanks Cakley).
As is obvious here and is unfortunate for engineers everywhere
at times, Marketing had a hand in developing this muff.

To close it back up I bent the door closed, used a few 1/8"
pop rivets to hold it in place. At Willie's recommendation used
J.B. Weld(Ace again) to seal it shut. This stuff drips like
crazy but Willie helped me again. After mixing let it sit for about
30 or 40 minutes till it JUST Starts to get pasty. I used a hair
dryer to speed the process. Then used the dryer on the muff
to speed curing. Let the car sit for at least a day before running
motor. Run motor to final cure J.B. and check for leaks. I had
none. You can lightly sand and add more J.B. as needed.
Important, before you start the muff mod. Drill a water drain
hole in the FRONT surface of the muff at the bottom(low point).
I used a 5/64 titanium bit(Ace again). This muff gets ALOT of
H2O in it. If you don't care to leave the hole you can always
stick a screw in it afterwards. I like the hole(lots h2o comes out).
After all done ran motor to heat muff and sprayed it with black
Rustoleum barbeque paint(that Ace place again), looks OK.
Tentative results from testing. Moderate improvement in
acceleration(results appear to be a bit different than cakleys).
Improved highway mpg. Lean burn at higher speed(for me).
Cut off point seems to be between 72 & 73 actual mph (w/out tail
wind or drafting although head wind will slow you down
of course). By actual mph I mean checked against my gps. If the
speedometer says 70 my gps tells me I'm doing just over 71. I've
heard with some insights it's the other way round but the gps
seems to be working OK. I'll let you know more as I learn more.
Testing is tuff around here on turnpike. One minute your free and
clear and the next your surrounded by cars and you can throw
the test out the window. I did go ahead(since the noticeable
improvement) and do the mod to the '00 as prescribed
above for her next owner. There are 3 pics. I'll try to post as
previously stated. Please let me know what you think & if I may
have missed anything.
Thanks, Jack Lee
[email protected]
P.S. Did the cakley throttle cable mod to the '04, you can dial
in the mpg you want and rest your foot. Don't have any good
results yet on it's effect w/lean burn. Will post when I do.

364 Posts
Discussion Starter · #2 ·
Verbal Muffler Mod Pic

Hi All,
As I shared I will try to get the pics of
whats exactly inside the rear muffler posted
on another sight and link to them.
Till I can find a way to share the pics,
let me paint as best I can a picture:
The rear muffler is separated into 3 chambers
of aproximately equal size by 2 vertical steel
discs inside (no holes except for where pipes
pass through).
The exhaust pipe (from the engine) enters
the front of the muff into chamber 1 and passes
thru cham 2 and ends midway (open at end as all
pipes ending midway in chamber will) in
chamber 3. As it passes thru cham 1 it has very
small holes around it, aprox 1/16" dia and about
20 of them. As it passes thru cham 2 it has aprox
20 - 1/4" dia. holes. Ends midway in chamber 3.
An intermediate pipe starts in cham 3(following
flow of exhaust) and ends in chamber 1, open at both
ends. At the end of the pipe in cham 3 the pipe necks
down to 7/8" i.d.(restrictor) As this pipe goes thru
cham 2 it has aprox 20 - 5/16" dia. holes. Ends midway
in cham 1.
The tail pipe enters the rear of the muff into
chamber 3 and travels thru chamber 2 into cham 1
and ends midway as the others, open at end. No other
holes.The tail pipe is slightly larger in dia. inside the
muff (aprox 1 7/8" i.d.) then it is where it exits the
muff. Hope this helps till I can share the pics.

140 Posts
If you want to e-mail me the pics, I can resize them and put them on a web page. I'm curious to see what is in the muffler and any increase in mileage from removing it.

If you want, PM me for my mail address.

453 Posts
Cool. Good work. That stock muffler is one heck of design. Very Very restrictive. BTW its cakley only one "c"

If any one is interested I've got a stock non modded cat-back to sell.
I've also got the throttle control to sell.

364 Posts
Discussion Starter · #6 ·
Thank you Cakley, noise, mpg & grp buy

Yes THANK You Cakley,
My variation to your mod is different so
different results may be the rule. I've
alot of testing to do so accurate results
may take some time. especially around
here where traffic is nuts. Tentative
results are good so far.
Noise level:
After doing mod I listened (up close and
further back) to the mod'd '04 and the
still to be mod'd '00. Hardly perceptible
difference. By holding my hand close to
the exhaust on the mod'd could feel the
pulse of the cylinders slightly. Not so w/
the to be mod'd, just more of a steady
whoosh of exhaust. Noise level slightly
higher. If you didn't know it was mod'd
you might not notice the change. The mod
should hold up too. From my understanding
as shared with Willie the J.B. will probly
be there long after the muffler has rotted
out(kinda like 3M 5200).
No good definite results yet. I did log a test
run this morning to my first work sight. 17.8
mi on turnpike(I75 FL), late rush hour so some
drafting couldn't be avoided and speed variations.
77.2 mpg w/ aver spd 68. Another 8.3 mi on
local roads to destination finished 78.7 w/
aver spd aprox 42. Turnpike log had good
lean burn. Hard to get good test results when
you’ve got people cutting in front of you and
hitting the brakes to pull off. Just another
morning I wished I had a Cannon mounted
on my hood.
Just a thought:
The printing on the back hatch of our insights,
Would anyone be interested in adding screen
printing something such as "experimental
vehicle" or "Insight.Central"
"experimental" or such as
a group buy? I do have a friend who is in this
business who could do it for near cost. If we
used the same font, size and color that's
there, it would look ?? Any interest, Ideas?
Jack Lee

364 Posts
Discussion Starter · #7 ·
THANKS Otmar, Muffler Pics, Edit 7/5/4

Thanks Otmar & James too,
Help is what a teams all
about, Thank You
Jack Lee
Now let's see if I can post
this link, here goes:
Hi all,
The pic w/ the muff vertical,
rear is at the top. EDIT:7/5/4:
better discription: The other
two rear is on left with the pipe
on the top being the intermediate
pipe. Pipe in the middle is the
exhaust in. Pipe on the bottom
is exhaust out (tail). Anyway,
in one chamber you'll see
a pipe that ends necked
down(restrictor). That is the
rear of the muffler. At any
rate I'm real happy to see
these posted. Their a little
different than my memory
serves. It's important that
you see this if you want to
mod muff.
Thanks again,

Premium Member
891 Posts
Nice pictures of the stock muffler.

So, what you did was cut the tailpipe where it enters in the 3rd chamber. This way most of the flow can go directly from the middle pipe, into the 3rd chamber, and out the tail. In the stock configuration, the flow exits the middle pipe in chambers 2 and 3 and enters the 2nd pipe. Then it travels back to chamber 1, exits the 2nd pipe and enters the tailpipe.

Did I get that right?

364 Posts
Discussion Starter · #9 ·
Hi Tim, Muf flow, mpg & 2 logged trips

Basic for exhaust flow yes. From pics exhaust
pipe in lets a little into cham 1, little more in
cham 2 & dumps rest in 3. Intermediate pipe
lets a little in thru restrictor in 3, more in 2 &
what’s left in 1. Tail goes thru 3, 2 & ends open
in 1 w/ no holes so will only pick up @ 1. As
Cakley said Honda probly (if I got this right)
put the importance on silence over perform-
Two more logged trips today. I may be see-
ing a pattern.
I75 north to I275 & NO., 78 mi. Light tail/cross
wind 4-6, traffic moderate to heavy no stoppage.
Aver spd 68-70 mph. 79.6 mpg.Some drafting
couldn't be avioded.
I275 south to I 75 & SO.(over Skyway bridge
both times, real high), traffic moderate to
light, 67 mi. Head wind 13-15 mph(lightened up
5 mi after Skyway 6-8 ). Aver spd 63-65 until past
skyway, 68-69 after. Mpg for trip 76.8. Strong
headwind crossing Tampa bay would knock me
down to 63 mph but could retain mpg. Afterwards
lightened up and 68-69 & retained mpg w/wind.
Something Willie said about the vehicles torque
range. It should have been a 4 spd w/ overdrive
instead of a 5 spd. Geared too hi? Willie, if your
there have I got that right?
Anyway I could never have gotten these kind of
numbers before. Of course I could do 70 mph but
lightening up on the gas to improve mpg could
never retain the speed. Now if I keep the car above
68 until lean burn kicks in I can maintain 68-71 mph
at mpg in logs. If I let it drop to 67 the car wants
to continue to drop to 63. Think of a gear ratio(trans)
as leverage between motor & tires. Too slow in a hi
gear and car bogs down. I think this is what is
happening. Now that the car has more umph
(power) the leverage in 5th gear is enough to
maintain the spd. This is not enough to explain the
mpg. Maby allowing the engine to breath better(and
it is) is allowing lean burn at higher mph. Anyway,
It's working so far. Around here people drive nuts
w/few police on turnpike. Drive too slow and they go
over you. Now that I con do speed limit w/mpg I
can relax. Anyone that thinks I'm driving too slow
now can go to hell. I didn't care for bad/aggressive
drivers before either.
I will be logging all trips I can and reporting as I
can. Need help (always), any engineers or others
that understand concepts of the insight that can
further detail or theorize what is occurring to
cause these results. Also, why did the factory not
provide a water drain in muf w/ all that H2O, ALOT.
I see that other manufacturers do, why? Next thought
is to put a second tail pipe into the rear cham. One
that could be ajustable for exhaust flow to find
possibly just the right amount of relief for back
pressure, ideas?
Thanks, Jack Lee

364 Posts
Discussion Starter · #10 ·
Two More Logged Trips & 2nd pipe

NO. on I75 & I275 to Tampa. Fri before holiday
wk end, very lite traffic til past skyway bridge.
So stopped trip there as drafting made test
invalid at that point. Trip 64 mi. Lite to no wind.
69 - 71 mph. Mpg 75.6. Held gas peddle at
aprox 80 mpg.
SO. I75 for 63 mi. 2 - 4 head wind. Little traffic.
Speed 69 - 71 mph. Due to head wind held peddle
at aprox 75 mpg. Mpg 74.9.
Also note, going over hills or overpass less throttle
is needed to get over. If shallow hill can just
maintain throttle pressure to get over w/out bogging
down. If wish to can start hiway in mid 60's, with ea.
cycle of lean burn can let that walk car up to 70mph
(lean burn kicks, mpg bars go down, 2 or 3, leave
peddle where it is, mild boost, then 2nd half bars
go up, push peddle down to mpg where it was,
and so on).
Not a test trip. 8 mi travel east crosstown expy.
Aver speed 54 mph. 1 - 2 hed wind. 87.8 mpg.
Results so far are very consistant. Aver around
town mpg up as well. Much easier to maintain the
100 mpg @ 50 mph standard I've always expected.
Acccelleration is also improved while maintaining
high mpg.
Where does this lead? Well the results are more
than I could have hoped for. These 2 insights are
probly going to log some phenominal mileage #'s
over their remaining life time.
I will be doing further modification to muff, just
got to know how far we can take this idea( yes,
thank you Cakley). Probly will be a temporary
adjustable 2nd tail pipe attached to the rear of the
muff to find how much relief is just right.
Won't be as easy as the muff mod(car on stands,
remove RR tire and the little mud flap looking
thing behind it (4 screws)). To do a second tail
will probly have to remove rear bumper as
Cakley did.
Once we find the right amount of relief should
be able to reproduce it by slightly modifying
the existing muff mod. I'll start working out the
details for the 2nd pipe this wk end. Won't be
cutting holes in the muff rite away so if anyone
has another idea please let me know, much-
much appreciated. And if your out there Cakley.
did your throttle mod (same cable you used,
just mounted it a little to the left on dash). Made
the firewall hole a little to the right as you
suggested(just slides right thru). Tried it today,
dialed in 80 mpg, 8 miles flat road 70 - 71 mph
80.7 mpg w/lean burn & no foot interaction.
Am I seeing things. Had been raining previous,
moisture? Got it, could have been surfing and
didn't see the truck in my blind spot... Any ideas?
Let you know more when I learn more...

453 Posts
nice pics. would be great for others if you could photoshop them and label the input and exit pipes. That would really show how restictive the muffler is.

I never cut mine open, too scared!

364 Posts
Discussion Starter · #12 ·
Muff Pics & Rear Bumper

Hi Cakley,
Sorry, don't have much experience with photoshop or the like. Did
follow your prompt and gave a better description in the reply that has
the link to the pics. Hope that helps. Have the '00 back up on blocks
now (did turnpike testing this wkend) and getting ready for the 2nd tail
pipe. I remember you sharing somewhere about how to remove the
rear bumper, could you give explaination or share the link. I have the
service manual but from my experience hands on knowledge as yours
is invaluable. I guess a little improvement can lead to so many new
Thanks, Jack

Premium Member
1,631 Posts
I did the internal version of the modification with yet another modification.
Instead of cutting through the pipe taking a chunk of pipe out, I drilled two
large holes (about .75 inches) into the same area. My only fear of cutting
all of the pipe off was that there would be no internal strength supporting
the tail pipe to the end. I know it doesn't weigh too much but as time goes
by and the exhaust gets old, the tail pipe may become loose before its


364 Posts
Discussion Starter · #14 ·
Good call joecvt

I thought the same about tail pipe support. After mod completed I
observed the tail at idle for excess vibration movement. Fortunately
it just moved the same as the muff so I went ahead and posted the
mod. Noticed the weld support for the tail at the rear of muff is very
strong and the tail is short and light or I wouldn't have cut all the
way thru.
The holes you cut should be big enough to do the job. Would really
like to know what results you have observed so far. How's
accelleration and highway mpg's?
Will be working on 2nd tail soon. Did WeatherTech in chanel
window shade mod 1st (completed today). Lot's of rain here and
was tired of my left leg getting soaked if I cracked the window.
Will post the pics with the mod soon then finish the tail.
Thanks, Jack Lee

Premium Member
1,631 Posts
I did not notice any major difference in acceleration although I got to
believe that it should help a little. What I did notice is that I can get
higher MPG without trying as hard and it seems like I don't have to push
the gas pedal down as far on some hills (till they get too steep)... If I
had to do it again, I probably would drill 3 or 4 holes just to make sure
that there was better exhaust flow. I was getting a little nervous about
noise level so I only did two but they are pretty big. I used the JB Weld
that takes 4 hours to dry and I did it in two stages so I had to wait over
8 hours before I could start it up and check for leaks and noise. I could
not tell any difference in noise level before and after. I think noise level
equipment would detect some slight difference but not enough for a
before and after human ear test.

After reading your post I went to the WeatherTech site but I did not see
a WeatherFlector for the Insight (I did see ones for other Honda models).
Did you buy another model and modify it?... I did try one that others
have installed (modified Civic 2 door 92602) but it didn't bend well to fit
the contour of the Insight window frame. All I can say is that they use
good adhesive because it took a long time to get the glue from the sticky
tape off the door frame. Plus, it looked too big for the window. I'm
looking forward to seeing the pics of yours...Could you also post the
part number that you ordered?


364 Posts
Discussion Starter · #16 ·
Hi JoeCvt

Hi Joe,
The part number I ordered was for a Honda Civic '96 thru '00,
2 door dx or hatchback ( pn=70046 ). It was a devil to make
fit but after I did the first door (5 hours) the second door took
about 45 minutes. Basically cut 1" vertical off rear of Weather
Flector and cut another 1/4" further but left tab to stick and
hold flector in rear of chanel. Cut 1/2" off bottom of front.
Also, cut lenth of flector so it wouldn't hang down more than 2"
( to remove some stiffness so it would flex to fit window chanel).
When installing must still hand fit (chanels vary slightly) and it's
got to be REAL tight to cause flector to follow chanel. If you
should cut too much you can shim (use material you cut off)
under front bottom where it won't be noticed. Finished
product looks good, like it was made for the car.
Just the same I found a car today that may make a better fit.
Dodge avenger, as soon as I get a chance to match my template
(made one that is within .010") against one I'll let you know.
Though it's been my luck so far that if it's a close fit for an insight
they don't make a window shade for it.
Hope this helps,
Jack Lee

Premium Member
1,631 Posts
Thanks for the info Jack, Sounds like alot of work...I may wait a bit longer
to see if there is anything closer or maybe someday there will be one
made for the Insight...(I may be dreaming here).

By the way...My real name is John but I created the account as just any
other CVT owner (kind of like "Joe Millionaire" or "Average Joe").


364 Posts
Discussion Starter · #18 ·

Hi John,
I know we're off topic here but I wanted
to follow thru for you, and will post the
window vent mod in it's separate mod as it
should be soon. Been real busy going to dealer-
ships and parking lots with my window chanel
template checking you know what. Very
exciting. You show up at a dealer with what
looks like a giant flat banana in your hand
holding it up to various cars and sales people
and security are on you in a minute. And the
sales people will never believe you won't buy
a car, they just don't give up.
Anyway, I've found it. Best quality, WeatherTech
for a '04 Honda Accord 2 dr Coupe, pn 70321,
in chanel Weather Flector. Near plug 'n play. Will
need a heat gun to make p'np. You can use heat
gun for other projects later, Home Depo has them
for $30 to $59. You may want to wait for further
info before beginning, I'm practicing with my
existing vents now for the best way to procede
w/o destroying them but it really looks great.
Sorry you havn't heard from me in a while but
I've actually been chasing cars that look like
possible vents for the insight. I can now know a
year, make and model by looking at drivers
Found a few dead ringers, Mitsubitshi Eclipse,
Acura Integra ('01), Toyota Celica 2 dr coupe GT,
Nissan 300zx ('96), but the god of insights will not
let anybody make a vent for them under eternal
I have time to practice since the vents will not
arrive till the end of next week (end of Aug). Will
start on them as soon as I get them. Good News
and their OEM or better quality.
P.S. Will continue with second tail pipe mod as
soon as this vent mod is done. Vent mod will
keep the summer rains out.

Premium Member
1,631 Posts
Hello Jack,

Thats a great idea using a template of the insight with other vehicles.
If only the Insight had higher production numbers we would be able
to order parts like any other car. We could probably be able to order
cut-out rear wheel skirts to expose the rear wheels. It looks like it
would be possible to have a look like this: (center image). I'll be
waiting a long time before I find a cheap set of skirts to play with.

Thanks for the ventshade update and I look forward to seeing the
installation results.


364 Posts
Discussion Starter · #20 ·
Hey John, good news

Hi John,
Will post mod for the window vent shade "WeatherFlectors" this
weekend if possible. Will not post here, will post as a new mod
as should. They arrived today, found them on the front porch
after work. Took less than an hour each to install them, as
mentioned they must be hand fitted since every window chanel
varies a little. So you cut a little less than needed, file a little,
file a little... Needed to use the heat gun to change the angle of
the front leg about 10 degrees. Not bad, very little work and the
result is beauty, they compliment the vehicle besides keeping the
rain out. They will not fall out but can be removed and reinserted
for whatever reason. Will post pic's of install, finished product and
will leave email or such for anyone with questions about mod so
they don't have to worry about damaging their new buy unless
they really goofed up ( I goof up from time to time too ). They
really look good, OEM or better.
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