Chevrolet Cruze Forums banner
1 - 9 of 9 Posts

·
Registered
Joined
·
39 Posts
Discussion Starter · #1 ·
Might be posting this in the wrong forum, my apologies if I did.
But, I was wondering on changing my Cat. I am running a dual Cat-back exhaust from Magnaflow with a Injen Cold air Intake. I was wondering:

1. if there would be any performance gains or change in sound?

2. Would it mess around with my O2 sensor and screw up my cars computer?

also, I was thinking on picking up Headers so I was wondering if that would also give any performance gains? They're in a 4-2-1 set-up.

Thanks for the help, any help will be appreciated.
 

·
Resident Forum Drunkard
Joined
·
9,272 Posts
You will definately have to get a tune for that set up as an Exhaust and intake ..

Good Luck shopping for Tunes !

You can let us know how IT sounds Later ...................
 

·
Premium Member
Joined
·
5,535 Posts
The only restriction point (and it isn't much) is the turbo inlet/outlet point if you are asking about the 1.4.

Flow modifications prior to or after the turbo would have little effect except at the very top of the rpm scale.....this eighty some odd cubic inch engine doesn't make a lot of 'blow' so the turbo port has to be small to avoid a endless turbo lag.

Short answer, without expensive mods, not much point in making changes to the exaust.
A tune would get more bang for the buck.

If you are asking about the 1.8.......the cat is already larger than needed for the displacement it must handle.
A tuned header, with corresponding tuning, MAY loosen up a few more HP at the top of the rev range.

Rob
 

·
Registered
Joined
·
59 Posts
what about keeping the exhaust stock but replacing the pre-cat with a high-flow cat? one of the guys at the muffler shop was showing me basically the work they would be doing on my exhaust if I wanted a cat-back exhaust and mentioned that I have my cat.. and a pre-cat.. he said that there's restrictions around the pre-cat and that i should change it to a high-flow cat... is this guy just blowing smoke up my a$$ for a few extra bucks?? Their shop came highly recommended to me..
 

·
Premium Member
Joined
·
5,535 Posts
The catalyst is not a restriction point on this small engine......a 'high flow' cat just drains your wallet unless changes have been made that create the need for more flow.....primarily being operated at a higher rpm than currently designed.

Rob
 

·
Registered
Joined
·
59 Posts
The catalyst is not a restriction point on this small engine......a 'high flow' cat just drains your wallet unless changes have been made that create the need for more flow.....primarily being operated at a higher rpm than currently designed.

Rob
Thanks Rob! It is tuned (Trifecta) so it's putting out much more power. Still a waste?
 

·
Premium Member
Joined
·
5,535 Posts
As I said earlier.....the exaust restriction point (if even measurable) is the inlet and outlet at the turbo........every component of the exaust, from the turbo outlet to the tip of the tailpipe, exceeds the flow at the turbo outlet.

Changing anything beyond the turbo outlet will likely produce no gain (unless sound is what you are looking for) and even that doesn't change much after the turbine beats the soundwaves to death.

Rob
 

·
Banned
2015 Cruze LT 6sp, RIP, modded like hell
Joined
·
379 Posts
Okay so catalytic converter and it's removal. Let's start with just the basics. What is a motor specifically? What is a motor? Do well. It makes power. But overall, what does the thing actually perform the function of doing it moves there in and it moves air out brings in cold air pumps out hot air. So if you look at it just like that, your motor is nothing more than an air pump. It does a lot more than that. But if you look at it from this angle now think of some of the benefits of removing restrictions. Let's go ahead and throw the whole back pressure thing right out. The window nowadays, especially the way motors are designed. You don't necessarily need back pressure. Ideally you want his little back pressure as possible, especially if you're all motor because you want something to happen called scavenging. Scavenging. Is this cool little effect where the exhaust flow and the gas is moving out because they're hot tend to be more dense and they're just flowing out a lot quicker. But the pressure difference between the exhaust moving and when the exhaust valves open tend to suck air in, it creates a vacuum. So it actually helps pull more fresh air in during a period called overlap, which is when both valves are open at the same time and take an exhaust are open at the same time and it helps pull bad air out and replace it with fresh air and sometimes a little bit of boost. Not much. We're talking maybe half a psi but it can happen here and there if you're flowing enough. Scavenging is awesome if you're running all motor. That being said, when it comes to boosting cars, you don't necessarily worry about scavenging because you're forcing air into the front. So you're not really worried about creating vacuum or any sort of scavenging type of effect during overlap because you're forcing air into the front. So the cam profiles are going to be radically different as is the valve timing. But at the end of the day you want to get as much air in compress it blow it up as hot as you can without causing any knock and get it out of the motor as fast as you can. Every four cycles like so every 720 ° of crankshaft rotation per cylinder. You want to get that that air fuel mixture in and out of the engine as fast as possible. The turbocharger helps you force air and it helps blow air out at the end of the day but your cat getting in the way because the cat actually has something in the middle of it is going to cost you. Not to mention the fact the catalytic converters with the friction of the air blowing past it and the actual heat of the exhaust cuz it is air coming from an explosion tends to heat up the catalytic converter and therefore hinders more performance and even more so is it starts to get clogged. Removing the cat will open up your air flow. A hell of a lot more. But you're concern is sound as well. So your muffler and your resonator will also cause a little bit of disruption but not anywhere near as much as a catalytic converter. Now your muffler is meant to cause a disruption in your exhaust cuz it's meant to well muffle the tone of the exhaust. That being said, the resonator is what captures most of the sound. The resonator is going to be what deden's a lot of the sound and keeps you reasonably quiet. If you run straight pipes all the way back, you're going to sound ridiculously loud. If you just remove the muffler but keep your resonator you will actually pick up more performance because the resonator doesn't impede airflow like a muffler does because it doesn't put things in the way. It just has baffles on the side of it that kind of disrupt the air and pulling some of the sound. It's kind of hard to explain because I'm not that type of engineer, but a resonator will absorb a good chunk of the nasty sound that comes out a muffler. Pretty much deadens the rest of it, but it deadens it by impeding airflow. So if you look at the inside of a resonator versus the inside of a muffler you'll see the difference and resonator looks kind of like honeycomb shaped tube with another chamber on the outside. A muffler is actually going to have different channels that the air is going to have to bounce around and pass through that it's going to get to The granted they're optimized for. You know performance as far as a stock car is concerned, but stock mufflers will pass through a lot of like right angles and weird things like that. Whereas if you're not worried about noise but you still wanted to sound like halfway decent having the resonator at least for the stock one, that's a way to go to. So if it were me, I would go catless and drop the muffler and then keep the resonator even on an aftermarket exhaust. But that's completely up to you if you want to run a resonator, but most aftermarket mufflers actually do a really good job without impeding airflow too. Sorry if that seems kind of not grammatically correct because I'm using Google speech to text so I apologize for any grammatical errors.
 
1 - 9 of 9 Posts
Top