- Okay. So the only remaining stock part on the Miata's exhaust is
the catalytic converter. Now the catalytic converters are great for reducing unwanted emissions and burning off the toxic pollutants that come out of your exhaust. And I can really honestly
get down with that. But in the case of the Miata, I'm looking for unbridled horsepower. And the catalytic converter is kind of a restriction, or is it? How much is it restricting
my exhaust flow? That's what we're gonna find out today. We're gonna make a straight
pipe to replace the cat. Then we're gonna go
back to the dyno to see how many ponies that
straight pipe frees up. We got a welder. (upbeat music) Thanks to Honeygain for
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in the description below. And if you use promo code 'donut' you'll get $5 added to
your honeygain account. Now let's get back to Money Pit. (gentle music) So this is what the inside of a catalytic converter looks like. It's basically a honeycomb pattern coded in some rare earth metals like Palladium, Platinum and Rhodium. So as you force hot exhaust gas through your catalytic converter it makes a lot of
chemical reactions happen and basically cleans your exhaust. A bunch of harmful pollutants that would come out of your
tailpipe are scrubbed off in the catalytic converter, and the only things that
come out in your tailpipe for the most part are harmless. So the goal today is to replace
this catalytic converter with a straight pipe or maybe you've heard it called test pipe before. Same thing. To do that, that means we're
gonna have to make that. So let's go see what we're working with and come up with a game plan. This is aluminium steel. This is gonna be really easy
to work with, easy to weld maybe rust over time, especially
these mild steel flanges. But it's gonna be relatively easy to make, and this is also the cheapest
materials that we can get. So the first thing I'm gonna do is try to figure out the
angles of these flanges on the pipe in terms of degrees. We got 86.3. So we basically
got about four degrees of angle from straight vertical. So here we've got 82.1 so that's about eight
degrees off of vertical. And now we know that we are aiming for eight degrees this way and
about four degrees this way. These are the flanges that I got. She is flat. She is mild steel and she is cheap. And she's for a two and a
half inch pipe which this is. Now you can see there's
a little bit of a gap. What that means is that
you can go like this. So I think we're gonna be able
to get enough angle out of it without really doing too much. The trick is gonna be setting
that angle before I weld it. All right. So there were plenty of ways to cut exhaust tubing. The other week when we did
Nolan's exhaust cutouts we cut exhaust pipes by hand. You could also use a
reciprocating saw like a sawzall or a cutoff wheel. But to make nice repeatable cuts a band saw really is
what the doctor ordered. Now, this is a pretty cheap
one, about as cheap as they get. Think they run from about
275 bucks these days. Basically what I'm gonna do is cut a little sliver off the end, but at an angle at about eight degrees let's get to cutting. Okay. So bandsaws like this generally have some sort tension control so that you can set the tension and then you can walk away from the cut while it's happening. So, I've got her set. (bandsaw sreeching) Okay. So we've got our little wedge about four and a half degrees this way and about seven degrees the other way. All right. So we're actually
really close to our first try. Now I just need to get the
overall length of this thing measured, cut, and then do this
again for the other flange. (bandsaw screeching) Okay. Our pipe is ready to weld. So now we need to get
our flange ready to weld. And the only thing we need to do there is clean it up. whenever you're welding anything it's really important to clean your metal. So I'm gonna clean the flange up and I'll clean the bottom of
this pipe up a little bit. But I am gonna be
careful with this because I don't wanna grind off too
much of the aluminized coating because that's what keeps it from rusting. All right. So we're ready to tack up this flange to this pipe. So welding in and of
itself is a huge money pit and a very deep rabbit hole. So we're just gonna get started today. And we're just gonna
focus on MIG welding today which again is in my opinion, the easiest version of welding
out there, anybody can do it. It is pretty simple. You just got to know a few basics. So that's what we're gonna cover today. The first thing we're gonna
do is tack weld this pipe to this flange which means, we're just gonna put a few little pieces of weld just to hold this thing together so that we can test it on the car and make sure everything's good before we fully weld all the way around. Okay. So the first thing we're gonna do is flip on the switch in
the back of the machine and then I'm gonna open my gas. So you might notice I have
two gas tanks back here. That's because this machine
does MIG and TIG welding which use different gases. So this is my MIG tank. It's a mixture of 75% argon
and 25% carbon dioxide. That's what you use generally
speaking for MIG welding. So I'm just gonna open it up. And then we've got this
pressure regulator here which meters the gas
flow into your machine. I've got to set it about 30 CFMs or cubic feet per minute of gas. That's kind of standard-ish
for MIG welding as far as I know. And this machine is super easy to set. It has an auto set feature. So you can just select the thickness of material you're working on and then it will work out how much heat and how much wire speed do you use. Now on any MIG welder those are
really the two big settings, heat and wire speed. So I've got this selected at
18 gauge thickness material. These numbers don't necessarily matter. Most welders will just have two knobs with random numbers on them. And it doesn't really matter. It's just the relationship
between the heat and the wire speed that you need to find. And it's really dictated
by what you're working on in terms of what kind of metal
it is and how thick it is. So those are the basics you with me. Okay. So now this thing's ready. We're gonna attack our pipe into place. So the only thing we need to do apart from use our torch is
ground our work piece. So you can obviously ground
to whatever you're working on, but especially if you're working on a nice welding table like this, we can just ground to the table. Then we'll get our pipe set up and then put a few tacks on it. Let me find a welding helmet. (upbeat music) (welder crackling) Okay. Well, she's tacked on. Now. We can take this to the car and make sure things are looking right. Similarly, how we had to trim the bottom of the pipe up there because it would have
stuck past the flange. We're gonna have to do
the same thing here. You can go like this. (blade buzzing) (upbeat music) Okay. So we've got our
test pipe kind of in place. We've got our flange bolted
to the rest of the exhaust and this looks like it's gonna work great. So now I gonna bring the welder down here. I'm gonna tack this flange into place. And then we're basically ready
to go welder up all the way. It's always a good idea
to disconnect the battery of a car that you're gonna be welding on. If you're gonna be
actually welding on car. Basically when you're welding you're using a lot of electricity. And if any of that
electricity finds its way into your electrical system,
it can do bad things. One of my buddies growing up actually shattered his rear window welding on a car because
he left battery connected. (welder crackling) Okay. Now we got this thing tacked up. It's time to take it off the car and go weld it up and actually
talk about how to weld. So as I go around this I'm gonna be welding
in kind of a C pattern. capital C, capital C all the way around. Now, since our flange is
a lot thicker material than the pipe itself, it's gonna be able to take a lot more heat before burning through. So what I'm gonna do is basically spend most of my time on the
flange, plowing heat into that. And then I'll kind of
walk up onto the pipe just for a minute, just for a sec. That's the method. Now, the other thing that's
important is how far away you are from the piece with your torch. So you wanna be about
three eights of an inch half of an inch away from, from the surface of what
you're welding with the torch and on something like this, where we've got this 90 degree joint I'm gonna be at about 45
degrees in this direction. And then I'll kind of be at
an angle in this direction. If this makes sense. Now there are two ways to go about it. You can lead the puddle where you're kind of welding this way and dragging your torch in front of it. Or you can push it where you're pushing
the torch from behind. It's kind of personal preference. I do both of those things. Depending on what I have to do, depending on what I'm working on. So once you understand kind
of how to hold your torch and everything like that, do kind of a dry run where
you don't actually weld but you just confirm
that you can actually do, see like I'm hitting, I
got a little issue there. So, I should have this over my shoulder. Now I should have probably
just done that from the start. But, I didn't, and I wouldn't have if I didn't make that dry pass. So we'll do like this. And then we've got a nice
clear path all the way around. I'll probably do this in like two or three different sections. So with that said, let's do it. (upbeat music) (welder crackling) All right. So the first side of the test pipe's all welded up and it doesn't look terrible
if I do say so myself. I'm gonna let that cool down for a minute just as is, and then we'll flip it over, Weld the other side. (welder crackling) Okay. So Test pipe is completed. Now, the only thing we have left to do is go to the dyno and test it and see how much horsepower we gained. Let's go. We are back at my friends
at EF1 Motorsports to get some dyno time from EF1 tuning. So the stock cat is on the car right now. So we're gonna put the car on the dyno and do some polls and see how
much power we're making as is. And then we'll pull that off and install our test pipe
for our straight pipe. And then we'll make some more polls and see how much horsepower
that straight pipe left us. (upbeat music) So that's three runs
with the cat in place. And our average power is
234 and a half horsepower and 215.6 foot pounds of torque. So now we're gonna swap
back to our test pipe do this again and see what
the numbers provide us with. (upbeat music) Okay. So we are having
some interesting results and I'm gonna try to explain
what I think is happening here. We put the test pipe on and kind of lost the
ability to control boosts getting a little bit of boost creep. Now, what we're looking at here is boost. Now the dotted blue line that's our run with the cat,
and you can see boost comes up and red stays pretty
steady at where we want it. But the magenta line
is with the test pipe. And you can see it comes up and it starts to flatten out
like we're controlling it, but as RPMs come up and our
exhaust is flowing so well with our new test pipe that
the internal waste gate on this turbo is overwhelmed basically. And isn't able to bleed
off enough pressure to keep our boost at the level we want. We're telling it to completely
dump boost at that point. It doesn't matter. It's just boosting. As we're so high in the RPMs and that tiny little internal waste gate is just overwhelmed. So we're kind of stuck with this. I mean, we're making like 260
horsepower with the test pipe because we can't keep boosts
down to where we want it. So that's kind of cool. I mean, we made like 30
horsepower, but we're also apparently at the limits
of our waste gate setup and as such our turbo setup. So we might have changed turbos in the not too distant future, if we wanna change the
way things like are going. Okay. So with our boost
creep issues explained I still wanna try to make
this test a little bit more apples to apples. So I just put the cat back on and now what we're gonna do is, try to match that boost
creep with our tune so that we try to put
the same amount of boost through the cat on purpose. So then we can at least
see how much power we make at those boost levels
with the cat in place versus those boost levels
with the test pipe. Even though the test by boost levels are on accident, make sense? I hope so. (upbeat music) All right. So we just got
done retesting with the cat. And we're looking at
our boost map here again and you can see our original boost line that we were kind of chasing, that magenta line is in there somewhere, just buried by all these other boost lines because we did a really good
job of mimicking that boost, that boost creep that we were having. So, once we did that
and we retested the cat the numbers that we got are as follows, we have 252.8 horsepower
on average with the cat and 210.1 foot pounds
of torque on average. Then with the test pipe, we managed 257.7 horsepower on average and 217.2 foot pounds
of torque on average. That means we picked up 4.9 horsepower and 7.1 foot pounds of
torque with the test pipe. Not too shabby. Its certainly
not those 30 horsepower that we were seeing in difference. But with our boost creep
issues taken into account, I think this, is a pretty valid test as far as tests go. well, we sort of did it. We made a test pipe. That was pretty cool. We put it on the Miata and we definitely made
way more power with it. Now I'm not too happy with the
way that we made the power. I think we've got some
issues like we talked about. So I'm gonna have to address
those issues in the future. But for now we are making 260 horsepowers. So I've got some more
work to do on the Miata. Now, if you also like working on stuff and like the types of videos
where we work on stuff, then you gotta go check out
yesterday's bumper to bumper where Jeremiah goes over and
insane 2000 horsepower Altima. They talk about 3D printing body panels. They talk about how the
heck it even makes sense to basically delete the whole chassis and replace it all with tubes. And they'll divulge a little secret. Which seat is the most fun
to ride in, in a drift car. Hint, it's not the front seat. So go watch that bumper to bumper. You will not regret it. You just got to click right here. Oh, and also don't forget,
we've got an underground, the Donut underground. And one of the perks which ends tomorrow is that we'll send you a free
sticker every three months, if you're a member. But you got to get signed up by tomorrow to take advantage of the free stickers. For more information
about Donut underground just click the join button below and I'll see you in the underground. And also with all that said, I'll see you guys next Wednesday. Don't forget to follow
me on Instagram @Zachjobe and I will catch you cool cats, in a week. Goodbye.
