Custom Exhaust

[pantyraid]

After the snow melts and i get a little bit more money i plan on bolting up a custom dual exhaust made by myself. i have a 98 LS 3.1L Monte Carlo. i need advice on several things, what is the best size of tube to use 2.5 or 3, what is the best high flow cat to use, i know its illegal but should i even use a cat and if i dont how can i trick my O2 sensor so my engine light wont come on. I want to run with just one muffler a single to a dual and i want my exhaust to sound as much like an 8 as possible, i dont want that dumb ricer sound and i certainly dont want that stupid V-6 wine. i plan on welding all of this myself with a mig or tig, i was thinking about bending but i heard that if i took mandel (or something like that) pipes i assume those are already bent pipes and cut them then welded them until i got the desired bend that would be better because it would be the same size all the way around the bend. so if you could give me some input on exhaust that would be great. AND REMEMBER I WANT TO DO ALL THIS WITHOUT THE ENGINE LIGHT TURNING ON!!!!!! Thanks

[Aaron]

AND REMEMBER THAT BIG SEARCH BUTTON AT THE TOP OF THE SCREEN. I AM SICK AND TIRED OF ANSWERING EXHAUST QUESTION AFTER EXHAUST QUESTION.

 

2.25" would be best for a 3.1L. Mandrel bends don't crush the pipe as the turn commences, therefor by using mandrel bends you will gain the maximum amount of power. I'd use a high flow cat, I am using a carsound cat made by Magnaflow. Your 02 sensor is located ont he down pipe, so unless you plan on replacing this as well, it will not be an issue. If you do, just weld a nut in there. So long as you plug your 02 sensor in somewhere on your exhaust sytem, and plug it in electricly, you won't get an SES light with the system. I'd use a single 2.25" pipe into a muffler of your choice (I use Magnaflow, but the DOHC motor is a different beast), and then run dual 2" pipes out the back. A stock 3.1L doesn't need anything bigger than 2.25".

[jeremy]

AND REMEMBER THAT BIG SEARCH BUTTON AT THE TOP OF THE SCREEN.

 

 

[EurosportZ34]

AND REMEMBER THAT BIG SEARCH BUTTON AT THE TOP OF THE SCREEN.

 

 

 

it seems as though this is the 10th non-searched question in the past week!

i think every newb should get an email explaining not to post before they use the wonderul search tool...

 

[pantyraid]

my bad on not searching for it.... but i do think i had questions that were not discussed on here in later dates.. sorry for the inconvience though

 

 

what kind of a sound will i get out of that 2.25 set up with the high flow cat????

[Aaron]

It depends on what type of muffler. A lot of people use FLowmaster, I personally hate Flowmasters. Flowmasters were amde to sound good one one thing, a OHV V8, nothing else. They sound like shit on the N*, TOTAL ass on a 3.4L TDC, terrible on a 3.8L, etc. I would use Borla or Magnaflow. Both are pretty quiet and you get a nice, deep rumble at idle. As RPM increases, they both have a small rasp point at about 2-3k rpm for the DOHC and the pushrod motors, but that is more the engine. I'd stick with Borla or Magnaflow, a high flow cat from either, and a high flow resonator. But using all of these components together, along with mandrle bent piping, isn't cheap. Expect to pay about $400-$500 if you do all the welding yourself, and up around 700 if you have a shop do it.

[Carotop]

Hey Aaron did you make those downpipes yourself? If so, how much would you want to make me a set for my 3.1?

[pantyraid]

replace the resonator with a straight pipe?? pros and cons?

[Aaron]

Pros, .723 more horsepower at the crank, probably .6 at the wheels. Cons, your V6 will have a bad mid RPM rasp, and sound like shit ont he low end. A resonator is a MUST with a 3.4L DOHC, and I would highly suggest it on any other 60 degree V6.

 

I made the headers, downpipe, and the collector for it, and looking back I should've, and could've, made the entire exhaust, but RedZMonte did that part. Each header collects into a 2.25" pipe. The front downpipe, 2.25", runs down my factory downpipe tunnel, much liek the factory setup. My rear set collects neneath the subframe, then runs below the downpipe tunnel, where it meets with the front set, where both 2.25" pipe combine into a single 2.5", that runs all the way back. There is not a piece of crush bent pipe in my entire exhaust.

 

As for a downpipe for a 3.1L, I could make one, but not yet. In the summertime I will start making custom parts like that if people would like, but I'll need either their car or a similiar car to fab it on, as I do not have access to any 3.1s. But I have some friends that have 3.1s that may let me borrow their cars.

[Carotop]

Ok, thats sweet. I'm broke now anyway so that'll be cool.

[pantyraid]

http://www.cardomain.com/id/pantyraid

 

 

this is what im thinking for the exhaust now... tell me what you think...

[Aaron]

Generaly the dual exhaust on W-bodies is done the same way. It is a single pipe all the way back until around the fuel tank and where your rear axle might be. The cat and the resonator sit right underneath the cab of the car. Then at the rear axles area, it Y's into 2 smaller pipes. These head out towards the back, with one muffler on each before the tips. So it is dual muffler. This allows you to use straight through mufflers as well. Its your coice, but this setup is a lot more common.

[Grand Moff Joseph]

I would think that you would not need an additional resonater, as most aftermarket mufflers act as resonaters anyway, right?

[Aaron]

On a 3.4L DOHC it is absolutely necessary, otherwise it rasps like you couldn't believe. On a 3.1, I'd suggest it.

[sl3196]

On a 3.4L DOHC it is absolutely necessary, otherwise it rasps like you couldn't believe. On a 3.1, I'd suggest it.

I'm starting to think a L67 needs it too, I took mine out and it is really raspy.

[pantyraid]

explain your raspyness.... when it happens... and what you car sounds like at idle

[Aaron]

Me?

 

My raspiness is a direct result of the headers, which is normal. But at idle it is deep, yet quiet. The rasp comes on about 2,000rpm and lasts till about 3.