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Discussion Starter #1 (Edited)
After reading Cakley's muffler modification and the modified version,
I did one mod a while back by cutting a door and drilling some holes
as explained in this old thread:
http://www.insightcentral.net/forum/viewtopic.php?t=1657&highlight=
I drove with this mod for awhile but I began wondering if I could have
directed the air flow better. After studying images of the whole exposed
muffler, I thought that I could squeeze a bypass pipe in the last chamber
to direct the airflow right out the exhaust (with no back pressure) so I
decided to do it. I bought a new exhaust (since the old one had holes
drilled into it I thought I would use it as a backup). Here is the link
explaining the internal bypass pipe OEM muffler modification.

Here are a few pictures if you want a quick reference:

The internal area of modification
The internal pipes cut and ready for the bypass pipe
The bypass pipe installed and sealed with JB Weld
The muffler painted black and ready for installation

I can not detect any increased noise level but I can feel the engine
pulses. It is too early for me to comment on performance or mileage
but it has to be better than the standard restrictive muffler. :)

JoeCVT - Just your average CVT owner
 

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Discussion Starter #2
After driving with the modified muffler for 350 miles over 5 days, I'm
still at 62.7 MPG in a CVT (thats about 1.5 MPG better than my average
in the warmer weather). Still too early for any final conclusions, but so
far, it seems like it works as designed. If I put a MIMA controller in
(later on - after the 36,000 mile warranty), I may get closer to the EPA
rating of a Manual Transmission Insight :lol:

I mention the EPA rating because I know that I can't beat you guys
that typically get way beyond what the EPA achieved.

JoeCVT - Just your average CVT owner
 

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Discussion Starter #4
Thanks Mr. Trekker,

I guess I should have explained why I mentioned the 36,000 instead of
the 80,000 IMA warranty. The wires cut would be under the "Gear
selection" console for MIMA. If there was anything wrong in that
area (warranty related) I wouldn't want them to see any cut wires.

I don't think Honda would have to uncover that area to replace any
IMA component under the IMA warranty but thanks for mentionng it.

I say "Gear selection" loosely because it is a CVT. There still are
some gears in there! :lol:

JoeCVT - Just your average CVT owner
 

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Discussion Starter #6
Any shift linkage problems before 36,000 miles or anything that would
involve taking the shift cover off to expose cut / tapped wires. It may
be a stretch but it is only a little longer to wait...By that time, hopefully
MIMA_C will be available for purchase.

Update of the bypass pipe mod: I'm at 440 miles on this tank with
62.7 MPG....So far, so good...

JoeCVT - Just your average CVT owner
 

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Discussion Starter #7
I'm supprised that there are no replies within a week related to the
bypass pipe modification. I think that this is the best air flow mod
that can be made to the OEM muffler while still having an OEM look.

I'm now up to 550 miles on this tank at 63.4 MPG

JoeCVT - Just your average CVT owner
 

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OK, Here's a reply. I'm interested, but don't know if I want to go to the trouble for about a 1.5mpg increase. It might be more with the 5 speed, but I'll probably wait for some more info before I go to the trouble to do it.
I just wish I could get one of those really big exaust pipes out the back like the kids have, but don't want to cut up the back panel for the look. :lol:
Robert
 

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Well its been "done" in here in the past with mixed results. Search some of Cakley's old posts.

Glad your results are so positive.

Remember that the exhaust and intake system are "tuned" in a compromise of power / torque / RPM.

In an internal combustion engine increasing power through reducing exhaust restriction reduces low end torque. Its simply the physics of the equation.

In your specific set of circumstances and driving conditions the trade-off has apparently increased MPG. Not trying to discredit your claims but as you know there are many variables that effect MPG. It will take long term monitoring and compairson of other non modified Insights driven under similar conditions to confirm your results.

Change the pattern and the result will change.

But I think what has really caused this topic to be overlooked is that MIMA has most everbody's attention right now.

You've simply been overshadowed. Sorry ;)
 

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I have been following this topic but have not commented.

I do intend to do a muffler mod at some point. Jack MPG has a complete muffler kit that he claims got him much better mileage on his trip to Tour de Sol. I have also considered a bypass valve but I'm sure that it would tend to stick with time. If I did modify the exhaust I would braze it closed again in the interest of toxic gas emission prevention. I have considered changing the muffler for some kind of free flow design. I think I would prefer to take the original muffler off completely and save it as stock, replacing it with a custom free flow design.

Mima has been a buzz lately but if you are really interested in the full capability that it has to offer then the Insight has to be optimised as much as possible. Hot air intake and exhaust mods will help as well as anything that will increase battery life, increase efficiency, modify the characteristics of the nut behind the wheel, or reduce drag.
 

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I'm likewise interested, but haven't had a whole lot to say on the subject. Seems like you covered all the essentials in the first couple of posts (and link).

I am rather dubious about muffler mods, though not for the reasons mentioned. I just happen to like quiet cars (the main reason I'd like an EV :)), and I worry that any mod would increase the noise level.
 

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Last year I cut my muffler off. I did so after driving WIlle's little Red Rocket. I can't say that my mpg increased with certainty, at least it is not as noticeable as mods such as the hot air intake. In regards to noise it is not very loud at all. The only time I really notice the exhaust noise is in first gear accelerating with the windows down. I guess with two catalytic converters and a resonator not much noise makes it out. Have fun, RIck
 

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Discussion Starter #13
Hello All,

Thanks for the replies. It seems like most people who have done a
mod like this one claim better mileage. Cakley claimed from "53 MPG
to 65+ MPG" improvement. He also had a mod to the air intake
(a disconnect from the air intake resonator) working in conjunction
with the muffler mod. I still have the automatic warm / cold air intake
installed as I can keep it there all year round. (There are two earlier
threads about this mod). With the temps in New Hampshire still in the
40s-50s (a colder than normal month), the gate is open for warm from
the cat to come into the engine till about 70 degrees, then cold air from
the front of the car (I now have a bigger opening than what the earlier
pictures show). This cold air flow now has a better flow out the exhaust.
I'm not claiming miracle MPG increases (just about 2), but I know that
it will take some time to justify my statement. That is why I keep on
saying "so far" in my posts.

Insightful, I think you are correct that there should be a trade off
somewhere in the formula, but I don't feel any negative side effects
(at least in my driving style). As far as low end torque, some of that
torque comes from the IMA motor as shown in the link below so the
difference may be minimal as compared to conventional vehicles.

http://www.insightcentral.net/encyclopedia/enperformance.html

Rick, Since your lifetime is 90.2 MPG, I'm not sure if you would see a
noticeable increase in MPG with yours being so high already with your
driving style. However, your mention of low noise level even with the
muffler completely off should help those people concerned with noise.
I can not hear any difference in my muffler during idle or acceleration.

With MIMA installed (later on) my hopes are to get 65 MPG (summer)
and 60 MPG (winter). Not bad numbers for a CVT :lol:

JoeCVT - Just your average CVT owner
 

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Joe,
You could be correct on the mpg limit. My car is heavier than most so the loss of the mufflers weight was good but my highway miles don't have too many stops for overall weight to be a big factor. I think I cut mine off within a week or so of driving Willie's car. Have fun, Rick
 

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Discussion Starter #16
Just an update on the mod...

I finished up another tank and the display shows 675 miles @ 66 MPG
with normal driving back and forth to work plus some pleasure driving.

I have larger (and wider) than OEM tires so if you add the additional
size as 3 percent (3.4 percent reported by tirecalc) that would be 695
miles @ 68 MPG on a CVT!!!!

The tires are rated at 51 PSI and I put 48 in the front and 46 in the back.

JoeCVT - Just your average CVT owner
 
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