Dodge Challenger Forum banner

1 - 20 of 26 Posts

2013 Challenger SXT
1,221 Posts
Discussion Starter #1
I figured since there's nothing on the market for improved exhaust flow from heads
to catback I would build my own.

As you can see with pics below there was room for improvement. This will take me awhile
to complete and I will update when I can with each step of the process.

I will keep the factory exhaust from heads to Solo catback just in case this mod
doesn't pan out and I will be able to reinstall.

Stock manifolds purchased on ebay to cut up and do what I want with.

This photo shows the long side goes back in the wrong direction don't help flow

Lip at the entry of the manifold didn't care for this doesn't help flow.

This is what I think it should be.

The factory uses 2.5" exhaust pipe down to the cat back exhaust, I beleive this is the same
pipe they use for the bigger 6.1 engines, because my pipes from the manifold to catback
exhaust look just like the 6.1 engines.

Anyways I feel this is all to big for the 3.6 engine, I started with 2.5" pipe at
the head so I could get my radius and spread to fit the head flange. I will run
2.5" for about 10" and treat this as a collector and reduce my exhaust down
to 2.25" rest of the way, helpfully I can pick up some low end torque and not hurt nothing up high.

I'm also building this without cats, this is covered first O2 sensor will be installed as normal
and second O2 will be installed into dead air space so it doesn't pick up any O2 signals,
computer won't know any difference and will operate just fine, been doing this way for years
on many other cars.

This will take me some time to complete I work on it at 1 or 2 hours here and there.

After I'm done I will take it to the track and see what happens, I feel there is
something to gain here.

Premium Member
2,689 Posts
Nice job! I have an appreciation for people like you who want to experiment. I can't wait to see if it all pans out.

9,272 Posts
Seems like a lot of effort for a V6. Seems like new gears in the back would give you more off the line get up and GO.
Just curious how many cylinders would make the effort worth it? :dunno:

2013 Challenger SXT
1,221 Posts
Discussion Starter #9
I'm tinkering in the areas that I feel are the cheaper side of the mods that others could
do on the cheap per say, tackling the areas that really don't need a tuner
to change the computer because of mod.

I have tested the heck out of the cai , intake manifolds, throttle bodies and have pretty
good grasp on those areas and data to go along with it. I know by adding an
h-pipe to the exhaust just kills low end torque and slows the car way down, so I'm
going the other direction to try and speed up velocity in the exhaust to get more low end

I guess you can say this is kinda called super tuning if you will, trying to maximize
what the engine can do and keep a balance of low end torque and top end power, get
the most out of what is there.

If you look at my start of the year e.t./ mph and ending of the year e.t./ mph what do you see?
about the same e.t. yet mph is up. This is the balance keeping the low end while
trying to make more power. If I go for the high end
hp mods the bottom falls out and car becomes a slug off the line.

I have not even done a tuner yet, I think if I can get everything I can out of the motor
via cai mods, tb's, intake manifolds and exhaust, I should have huge increases in
power when it comes time to get a custom tune from hemifever.

a converter is a cheaper mod then gears,
a converter doesn't require a change in the computer for gearing and
that a converter makes up for lack of gearing.

a 3500 stall and 3.00 gears will 60 ft the same as
a stock 1800 stall and 4.56 gears.

since my car lacks gears, A nice stall converter will do 3 things, allow my car into
proper rpm range, act as if I had a gear change, plus the stock gears
will help me control wheel spin on stock style tires, since I never
intend on using slicks.

I would like to think from what I have seen on the stock exhaust the engine will
responded with positive results to my custom mod. And well if not
no harm no foul and the stock stuff can go back on and then I can
report there is nothing to be gained.

whatever the outcome is, stall converter is next then a tuner.

I'm just tinkering and enjoying messing around.

I grew up owning the mopar 225 slant six 1bbl engines, this v6 is a hot rod
compared to the old slant six, the old 225 slant six engines would run
19-22 second 1/4's depending on the car and wouldn't even break the speed limit
doing it. I had a slant six 225 that I got a ticket for doing 89 mph down a hill with
no exhaust full blast given the car everything it had.

So to me these new 6 engines are pretty damn good for power and they
are only 220ci.

I grew up where folks was putting 4 bbl carbs and headers on the ol 225
slant six engines and hot rodding them. bigger cam, I guess I never
recalled thinking it was a bad thing, It was neat to see different engines
and cars being modified.

508 Posts
I have to hand it to ya, keep up the work. You are trying things with the 3.6, that most people are scared to do. It gives us 3.6 owners something to look forward to. I always look forward to your post, good results or bad, they are very informative. Keep up the good work.

Sent from Free App

2013 Challenger SXT
1,221 Posts
Discussion Starter #12 (Edited)
Thanks for the support, thought I would give update, got one side done, pics are from
my cell phone sorry there not any better, but better then nothing.

I bought aluminized tubing from ebay and summit. pre bent mandrel. The "head tube"
was done with a 2.5" U-shape tube cut at points to get where it needs to go.

The 2.25" portion of the exhaust comes from a pre bent U-shape and 45 degree
tubing. then use 2.25" straight pipe for filler when I ran short from bend to curves.

It would be nice to had the equipment to eliminate some of the welds, but
this was all done with only a chop saw, $90.00 110 mig welder, angle grinder
black and decker hand drill with a variaty of stones.
and hand file to clean weld spatter and file fit each butt joint.

my attention was mostly on keeping the inside of tubing smooth and ridge
free to allow the exhaust gas free flow from one joint to the next.

the outside appearance was secondary.

A thought was if this mod was worth something power wise I could use
my test tubes as a guide and have new tubing bent from "manifold"
to catback and eliminate all but one or two welds and it would give
cleaner look on outside.

Anyways heres some pics.

2.5" tubing, many test fits, had to cut off 2nd o2 senser to close to steering

another pic of the same above

I ran the 2.5" tubing for 15 inches from head flange then I built using a "reducer"
an anti-reversion chamber, this is old technology, idea was to keep exhaust
from going back into the cylinders, will it help? I don't know for sure, will it
hurt? probly not, I needed to go from 2.5" to 2.25" so I figured what the hell
I'll build one since I was reducing the size of the tube anyways.

some under the car pics, pipe coming down from engine and turning towards cat back, couple
of 90 degree bends, came up a little short between 90 degree bends and had to weld
about a 1" straight pipe between the two bends that part sucked having to throw
two welds there.

I did fire up the car with just the one side done, sure can hear the "tin" sound since
the cat was removed. I'm really hoping for something positive, if not oh well, stock stuff
can go back on.

Hopefully this weekend I can get started on passenger side.

1,569 Posts
Some really good R&D. You don't like the H pipe but what bout an X of 2.25?

2013 Challenger SXT
1,221 Posts
Discussion Starter #14
Some really good R&D. You don't like the H pipe but what bout
an X of 2.25?
It's not that I don't like the h-pipe, the car doesn't, which didn't make sense at first, because
the car comes from the factory with an X pipe (almost). At the start of the catback attachment

X or H they open both sides of the exhaust basically doubling the exhaust
size each bank sees.

Of course the x pipe comes right after a screwed up exhaust exit, right into the
catback exhaust system, to me the "mid-pipes" looked to be thrown on to save
money at the factory, left overs from the 6.1 engines, 2.5" then they are necked down
to about 1 3/4" I.D. before the catback system is added which is 2.25"

So instead of the factory building a purpose built 2.25" mid-pipes with cats for the
3.6 engine they took some 6.1 mid pipes and squeezed the end down a little more
to fit the 2.25" cat back from the factory, probly to save a few bucks.

To me it felt like some of the low end went away when I bolted on the solo
catback system, I thought maybe it was because of the x over being gone.I
didn't think it was because I cut off the 1 3/4" reduced outlet off the mid pipes.

Knowing the h and x serve the same purpose I built the h pipe since it was easier
to build. after installing it, wham the bottom end fell out (torque was gone).
So my thinking was it slowed down the scavaging effect. Big 2.5 pipe then
introduce an h-pipe at the end of that and wham it must have really slowed
the pulses down, stacking them up all the way to the head,
making the engine work harder to push the exhaust gas down the tube.

Of course the h pipe could have been in wrong location, the facorty x pipe was about another
8-10" down, maybe this was far enough for gases to get lined up in the pipe and stretch out some
to create some vacuum before intering into the x pipe, which I must say is barely an x pipe
since it's only a small surface area in the middle thats open to each other ( two pipes
kissing each other really)

So I thought I would try the other way, see if I can get those pulses stretched out and get some
good scavaging going to draw out the exhaust in the cylinder, if this shows some
positive results maybe an h pipe or x pipe might improve.

I know the h pipe and x pipe can go either way, there is nothing set in stone
that either will work, the only way is to try each one on each car, some
swear by x some by h, what works for one will not work for other.

I have not ruled it out( x pipe), with the new test pipes, heck the h-pipe might work
maybe the x over would work better. I just didn't want to cut up any of the solo
kit to work in an x over before, with the tests pipes gives me a little more room
to try other things.

Long answer to short question.

2013 Challenger SXT
1,221 Posts
Discussion Starter #15
Got a little more done over the weekend. Here are some pics. Once again sorry for the
low quality pics.

This is what it looks like inside the factory cast in exhaust manifold.

New exhaust tube for the passenger side, this one didn't take me near as long to build
came out much nicer I think.

getting tubing tacked up and start the fitting process.

  • Like
Reactions: dv2012

Premium Member
427 Posts
Interesting pics of the exhaust ports in the head. Seeing that, I wonder how a set of 2 or 3 smaller diameter (maybe 1.5") pipes in tandem would perform? Probably not a lot of room to run too many pipes. Just thinking of keeping the velocity up in the head pipe. Even if there were any benefit it might get nullified by the cat and the rest of the exhaust.

3,285 Posts
Id like to see how it turns out ... good luck

2013 Challenger SXT
1,221 Posts
Discussion Starter #19
Interesting pics of the exhaust ports in the head. Seeing that, I wonder how a set of 2 or 3 smaller diameter (maybe 1.5") pipes in tandem would perform? Probably not a lot of room to run too many pipes. Just thinking of keeping the velocity up in the head pipe. Even if there were any benefit it might get nullified by the cat and the rest of the exhaust.

I thought about many different version, mostly double tubing, then I thought well then
that would cause restriction in the center, then thought keeping the middle opening then
tappering in two pipes side by side- kinda like cutting a x over in half and having
the open center and the exhaust would split nicely two both sides of the exhaust.

Many many different ways, if I had more equipment you bet I would try different designs,

I figured I would just try to improve on what the factory had, work the short turn radius
and smooth out the long side, give the exhaust the best possible path to turn the
direction it's forced to go, I treated it like a collector, as you can see in the head
there are built in path ways for the exhaust and they all merge at the opening - kinda like a
shorty header, so using the 2.5" tubing for a length 15" then bring it down to
2.25" .

2013 Challenger SXT
1,221 Posts
Discussion Starter #20
A dyno of before and after your custom mods would be sweet.

Sent from Free App
That would be. But I think I have the next or best thing depending on how you look at it,
very accurate and detailed, 1/4 mile runs. If I cough during a pass I know how much it
changes the pass. Keeping very detailed passes in my note book and all weather infor.
and the DA helps keep track of my changes. It's not huge gains but it is noticeable gains
positive or negitive and is a tool to make adjustments later on. I know for certain
what works and don't and I don't have to guess. I can give a direct positive answer to each

Like if someone asked does adding just a drop in K&N filter have any gains, most will
say no you get a lifetime air cleaner, because I feel I have done some very detailed
testing I can say for certain yes it does add power and give you a time of .05 reduction
and .5 mph gain in trap speed. It also makes your stock exhaust slightly louder.

Someone makes the statement the air box is the same as the v8 cars, if they can feed a v8
they are not a restriction to the v6, when in fact they are a restriction even to a v6
engine. So if they are a restriction to the v6 engine they are surely going to be a restriction
to the v8.

I don't want to claim I know everything, I'm learning this as I go thru this process
on this car and a lot of this information you just can't get from a dyno, because
most folks just see hp numbers and make the judgement right there wether the mod
is worth anything or not.

I like to tinker, this keeps my mind busy and it's a break from all the years
racing much faster cars, I'm slowing down and relearning new techonolgy
and I'm doing with something not many do, the v6 challenger. Yes I
could have bought a v8, like I said before I would be tearing into it and doing same stuff.
Lord knows I could have bought a v8. I spent enough on tinkering to have done that.

When I was first racing 14 second street car was pretty badass and I learned from there
Now I have a new up to date car running pretty much same kinda numbers
and I'm relearning. It's great and I'm having fun. If I can pass on what I have learned
great, it may help others make decisions if it's right for them or not.
1 - 20 of 26 Posts