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So the accord had been a fantastic daily driver for the last 11 years Aside
from regular oil changes, breaks and this summer clutch job the car remained OEM
as it could get. With its age it does starting to show some wear and tear though
and some of the little miscellaneous components needs to be replaced. One of
them is the exhaust, the down J pipe flex connector braiding has flailed and
needs to be replaced along with the mufflers as they too starting to have some
small cracks. Rather then having OEM parts put in at about $260 for OEM J pipe
and another $480 for cat back part of exhaust. I had decided to build up custom
cat back part of the exhaust at half the cost of the parts. True it will take me
4-6 hours of my personal time but it should release some hp to wheels.
With $240 I have bought enough stainless parts to make up the system and it
will leave plenty
left over. The resonator most likely will be removed not sure is provision will be made to put something in place or replaced entirely with a
one piece of pipe from catalytic converter all the way back to mufflers. The
main runner from catalytic will be bumped up to 2.5" the back where it will
split into 2x 2.25" pipes going to mufflers. The true flow 2.25"
in/out mufflers hopefully will be quiet enough. Worst case I'll have to put in
resonator in to muffle some of the sound.
Part two will be the down pipe as it is the most restricting part of the system
when it came out from factory.
So the first step is to remove the old system from the car. This is the worst
part of the process, removing bolts that join the catalytic converter to the
system behind it. I think Honda got really cheep or this is just normal and used
regular mild steel bolts and nuts. The
nuts rusted to a point that
they had rounded over and I could not put a wrench on them to break them loose.
Using vise grip pliers proved to be mute point as well and I had to resort to cut
off wheel and cut the nuts off so that I can break the cat back tube off.
Secondly the bolts where welded on the back side of the catalytic converter and
again they had to be cut out so that I could punch the bolt out from the holes.
For 11 year old pipes they are not too terribly bad.
First part of the runner from
catalytic converter to first resonator is bit discolored but that's to be
expected when high heat was hitting it. The
second tube between 1st
and 2nd resonator, again bit discolored not as much but in good condition. The
last tube after the second resonator not sure why but it looks like Honda
cheeped out and put standard mild steel tube cause it started to rust fairly
badly. Both of the resonators are still in good condition and they do look like
that they are made from 409 stainless steel. Mufflers on the other hand started
to form holes on top hence it started the hole build process.
Left muffler has crack on top of
the muffler and its soft on the crack.
Right muffler on the other hand worst of them all has hole that I could put
3 fingers into it and it was the main reason for this job.
The odd thing is I don't know why there are kinks in the first 2 tubes ????
Version 1
Now the interesting part, building the system. The theory is to put a straight
through pipe all the way
 back
and split it into 2 and feed it into 2 free flow mufflers.
So, since the catalytic has non standard tri-angular flange I had a cut off
stainless flange lying around with 2.5" hole inside I had cut off from other
project and too big that I had to cut down on the corners to accommodate to the
Honda catalytic flange. Now
that I had the flange I had it bolted to the catalytic converter and provided a
place and hanging point where I could slip the pipe into so it would hang and I
wire tide it on the back and positioned in middle of the tonou. I had pre made
earlier rear split of the tubes into
mufflers which gave me a running start. Originally I was going to put in flanges
so that I could unbolt mufflers from the pipe, but after thinking for a bit I
had decided against it as the mufflers and tube are stainless they should not
rust and I don't think I'll be keeping the car for the next 11 odd years so I
decided to weld the mufflers in.
After about 6 or 7 hours the system was made and hung. So here are the
differences
The mufflers, new mufflers are fair
amount smaller then original, they are stainless 409 not sure about the welds
cause it looks like mild steel wire was used to weld it up.
Tubes, main collector tube got increased
from 1 7/8" to 2 .5" and split into mufflers got increased from 1 5/8" to 2.25"
Surprisingly with the free flow mufflers
and short tail pipe idle is very quiet. Problem comes at higher idle, sound from
the mufflers increases and fairly loud with increase of the main pipe diameter
and being stainless there is a ringing pitch in the cabin during highway speed
and whenever you step on gas or let off of it. It would not be a problem when I
was bit younger but at current age the noise is bit much so that will have to be
addressed.
Version 2
After driving for about 5 weeks I got tired of the ringing and resonating noise
inside the cabin.
I had decided that it was time to fix. Rather then swapping mufflers I had
decided to add additional resonator in the middle as this would add additional
point to muffle the sound and at the same time extend tail end of the pipe after
the muffler. So the entire cat back system came out, got my trusty 'o cutoff
and cut her up leaving the muffler part in one piece. The main collector pipe
had been straightened out as it was bugging me after taking picture of it. Added mid
mounted free flow resonator and changed the angles of the tubes so that they are
bit smoother flowing.
With this small change, much of the cabin resonating frequencies had virtually
disappeared. Final sound at idle is bit quitter as well, however there is still
that "big" pipe sound when you step on it. One thing that is gone is the rumble
that you can hear for mile that are so familiar from the race systems.
Additionally the 2 inch choke point which had been introduced by the mid
silencer looks like it produced the magic point to engine responsiveness as it
seems like it spooling u p faster then before.
To reduce some of the minute tone from the main collector pipe it could be
reduced down to 2.25 inches from 2.5.
Original J pipe is still in the car and as it has been proven it is the
most restrictive part of the system. It will be interesting to see what will the
difference be if it was to be replaced with one that has much better flow.
....... more to come
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