Author Topic: 3 inch exhaust - Custom Build  (Read 4683 times)

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Offline SR20ME

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3 inch exhaust - Custom Build
« on: Mar 21, 2013, 08:13PM »
Hi guys

Well I started on my full 3 inch exhaust from the turbo back. I'm creating the exhaust from the cat back at the moment and all is going well. Time consuming as this is my first time to MIG Weld and doing this gasless means I am making good use of the angle grinder to clean it up a bit as well.

My question is about shape. I am copying the shape of the current exhaust that was on the car which I believe is the same pattern as a stock U12 / Corsair exhaust.

I have noticed there are two 90 degree bends and 1 45 degree bend. With 3 inches should I be worried about flow given these bends. I don't know how else to have the exhaust shaped given the fuel tank position and other parts underneath the car.

Appreciate any ideas  ;D

Offline SSS

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Re: 3 inch exhaust - Custom Build
« Reply #1 on: Mar 22, 2013, 06:41AM »
Any particular reason your are torturing yourself by using gasless wire? An e2 size bottle of argon is about $140 plus $10-20 per month for bottle rental.

Offline SR20ME

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Re: 3 inch exhaust - Custom Build
« Reply #2 on: Mar 22, 2013, 09:10AM »
An e2 size bottle of argon is about $140 plus $10-20 per month for bottle rental.

I'm on a budget I guess. If I can do gasless and save $140 and the welds are strong (which they are) then I'll do it that way. I have plenty of time but not as much in cash. I'll look at gasless today.

Offline SSS

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Re: 3 inch exhaust - Custom Build
« Reply #3 on: Mar 22, 2013, 09:46AM »
Smaller bottles are available that aren't as expensive. :)
Either way go on with what you are happy with.

Offline crazy2287

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Re: 3 inch exhaust - Custom Build
« Reply #4 on: Mar 22, 2013, 09:45PM »
The alternative been get everything tacked in strong and then take it somewhere and have it welded up.

as for how it's run, Think outside the box. If you have to do some fabricating under the car to run the pipe a bit straighter so be it.

Turbos LOVE flow. ideally you would just trumpet it to atmosphere. so straighter the better.
But really you probably wont notice the difference as long as the bends are clean. the bigger difference will be the weight of your wallet. 3 bends cost more then none by alot, straight pipe is half the cost of a bend.

Good luck, and enjoy welding under your car

(what am i saying, No you wont. been there and it fkn sucks.)
I drive like i screw..... illegally =D... wait O.o WHAT?? O.O

Offline SR20ME

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Re: 3 inch exhaust - Custom Build
« Reply #5 on: Mar 22, 2013, 10:34PM »
The alternative been get everything tacked in strong and then take it somewhere and have it welded up.

as for how it's run, Think outside the box. If you have to do some fabricating under the car to run the pipe a bit straighter so be it.

Turbos LOVE flow. ideally you would just trumpet it to atmosphere. so straighter the better.
But really you probably wont notice the difference as long as the bends are clean. the bigger difference will be the weight of your wallet. 3 bends cost more then none by alot, straight pipe is half the cost of a bend.

Good luck, and enjoy welding under your car

(what am i saying, No you wont. been there and it fkn sucks.)

No I'm not welding under my car. No chance in hell given it is not on a hoist  :o. I'm using my existing 2.5 inch exhaust as a template. I think it will be pretty close so I'm happy. Just have to fit it under the car to see.

Welding takes a lot of practice. I purchased gas. It is worth it but your setup can cost a bit. Say at least $200 for regulator and gas tank.

My welds are coming a long better. I realised today I wasn't welding at all but doing continuos tack welds. It still holds the exhaust solid and you can't break it and the holes are filled but it is time consuming. Its going to take me a few more days to get it right. Cutting the pipe to fit is also a bitch. I definitely respect exhaust workshops more after this experience  ;D . However didn't have much choice in the end. Either tow the car get it done and get it towed back equals the same price as what I have paid. Plus I have a few other things I want to weld and make for the U12 (little things but welding will be the best option for these).

Thanks for the input guys. Any tips keep them coming.

Offline SSS

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Re: 3 inch exhaust - Custom Build
« Reply #6 on: Mar 23, 2013, 07:45AM »
What wall thickness tube are you using?

Offline SR20ME

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Re: 3 inch exhaust - Custom Build
« Reply #7 on: Mar 23, 2013, 11:12AM »
What wall thickness tube are you using?

Its a 3 inch exhaust in Mild Steel. I don't know if there is a standard thickness. Next time I'm welding (probably tomorrow) I'll measure it and let you know.

Offline SR20ME

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Re: 3 inch exhaust - Custom Build
« Reply #8 on: Mar 25, 2013, 07:41PM »
For those who may be wondering...............

My exhaust is coming along well. I didn't do any work during the weekend but as I'm not working at the moment I'm doing a lot of work on it during weekdays.

Have welded all flanges except for dump pipe, cat converter, resonator and muffler. Just doing some trial fits and the main bend from the straight pipe to the cat is perfect but have to make sure it clears the sway bar and doesn't hit any suspension components.

Should have this finished hopefully by the end of the week. When I have it done I'll post some photo's.

Thanks guys

Offline MattJohn

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Re: 3 inch exhaust - Custom Build
« Reply #9 on: Mar 25, 2013, 09:53PM »
Out of interest, why are you making your own exhaust?

Spare pipe? Cheaper? Cause it'l be cool as fuck to say? - I'd brag..

"Dude that sounds mint!"
- yeah cheers, made it myself   ;)

Offline SR20ME

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Re: 3 inch exhaust - Custom Build
« Reply #10 on: Mar 25, 2013, 10:51PM »
Out of interest, why are you making your own exhaust?

"Dude that sounds mint!"
- yeah cheers, made it myself   ;)

Haha, of course mate  ;D

My car is not driveable at the moment and rather then get it towed to an exhaust place and back (probably around $250 - $300) I get a welder and equipment for the same cost.  I wanted to get the exhaust done before a tune and also I have changed the turbo so I had to either do a new dump pipe or at least look at other options and 3 inch exhaust is logical.

Other reason is I wanted practice welding given you need to weld stuff for cars and making stuff like brackets and other small things.

Exhaust cost me $900 in parts alone. Is a full 3 inch mandrel bend exhaust with Lukey muffler, Magnaflow Cat and Berkley Resonator. Should be good once finished but probably would get it done by someone next time!

Offline Pure_Sincerity

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Re: 3 inch exhaust - Custom Build
« Reply #11 on: Mar 26, 2013, 09:01AM »
Exhausts cost a fair bit, too much.

Mine:
Mandrel bend Headers to cat - $300
Hooker aero chamber muffler - $120
Tornado resonator - $60
Tip - $25
Exhaust shop/ 2.5" mandrel bend $360
Soon high flow cat - $250 total

Somewhere around those sums, close to 1k
U12 TRX
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COILOVERS
INDIVIDUAL THROTTLE BODIES

Offline MattJohn

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Re: 3 inch exhaust - Custom Build
« Reply #12 on: Mar 26, 2013, 09:43AM »
Sounds pretty great (Y) ahaha.

Least you can say you've done it man

Offline noss

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Re: 3 inch exhaust - Custom Build
« Reply #13 on: Mar 26, 2013, 02:06PM »
my exhaust was about $1500.

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Offline crazy2287

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Re: 3 inch exhaust - Custom Build
« Reply #14 on: Mar 27, 2013, 12:14PM »
If brand names an new items are not important you can do it for alot cheaper then that. Cost under $300 for me to build mine for the falcon inc flex coupling, extractors and muffler. Was only 2.5" dia so add $50 for difference in diamater.

but while im here, Do you experience a noticeable (non-placebo) improvement over the stock manifold?
I had a look at fabbing a manifold for my corsair when i was doing the headwork but all i ended up doing was port matching. Under inspection the stock cast manifold has collectors already in it's design so i woudlent anticipate a huge difference due to scavenging changes in after market headers since the stock manifold already provides it...

I drive like i screw..... illegally =D... wait O.o WHAT?? O.O

Offline SR20ME

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Re: 3 inch exhaust - Custom Build
« Reply #15 on: Jun 14, 2013, 01:23AM »
If brand names an new items are not important you can do it for alot cheaper then that. Cost under $300 for me to build mine for the falcon inc flex coupling, extractors and muffler. Was only 2.5" dia so add $50 for difference in diamater.

but while im here, Do you experience a noticeable (non-placebo) improvement over the stock manifold?
I had a look at fabbing a manifold for my corsair when i was doing the headwork but all i ended up doing was port matching. Under inspection the stock cast manifold has collectors already in it's design so i woudlent anticipate a huge difference due to scavenging changes in after market headers since the stock manifold already provides it...



Actually most of the cost was for just the number of bends although Cat and Reverse Muffler was the most. It does add up but if I did my exhaust again I would see what I could do. Knowing the bends and straight pipe I would need the cost would more likely be around $400 in materials then add muffler and cat.

I haven't yet ran the car but it has a stock SR20DET manifold. I definitely would think the 3inch will make a good difference over 2.5. I hope I get time and can test the back pressure once its running just to see how much I have. I don't think my exhaust will be as good as one from an exhaust shop but hopefully not too far off and much better than stock!