Author Topic: Picking an Exhaust size  (Read 5877 times)

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Offline minimikee

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Picking an Exhaust size
« on: May 28, 2008, 07:32PM »
hey all,
I called up an exhaust shop the other day as I'm looking at getting a bigger exhaust.

I ask for a 2.5" mandrel bent and the guy said that my car would not have enough back pressure to run that size exhaust, while its not a beast it has a stage 3 chip 3" CAI and r4 cam.

I thought a few people here had a 2.5" without a drama, I want performance, not just noise
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Offline Kranzy

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Re: Picking an Exhaust size
« Reply #1 on: May 28, 2008, 08:34PM »
Your looking at turbo soon yeah? Definatley 2.5inch.
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Offline chr1S

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Re: Picking an Exhaust size
« Reply #2 on: May 28, 2008, 08:40PM »
rofl @ backpressure quote.

what a tool
Don't let the opinions of the average man sway you. Dream, and he thinks you're crazy. Succeed, and he thinks you're lucky. Acquire wealth, and he thinks you're greedy. Pay no attention. He simply doesn't understand.

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Offline hrmmmm

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Re: Picking an Exhaust size
« Reply #3 on: May 28, 2008, 09:00PM »
I had a 2.25 exhaust on my corsair, then I had a 2.5 press bent exhaust that I bought of eurisko, then I put the 2.25 system back on because the 2.5 kept scraping on my driveway.

The 2.5 exhaust was fine and not loud at all, the only problem was with a cannon it sounded a bit hollow due to my engine being basically stock.

Offline minimikee

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Re: Picking an Exhaust size
« Reply #4 on: May 28, 2008, 09:07PM »
Back pressure is important though isn't it??

I don't understand that much about it but from what i do know if was to put on say a 3" on my car as is it would lose power wouldn't it??

I've got most of the things together for a turbo kranzy, just lack the money for the rebuild needed lol
lol Phantom and I at the wreckers
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Offline chr1S

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Re: Picking an Exhaust size
« Reply #5 on: May 28, 2008, 09:08PM »
Backpressure just means your exhaust will be quiet.

I ran a 3" exhaust and I found gains. You do loose abit low end, I mean idle-3.5kish but the cam won't be doing fark all for cylinder pressures at that RPM anyway, so I'd say go 3" if you plan on turbo or NA.
« Last Edit: May 28, 2008, 09:16PM by chr1S »
Don't let the opinions of the average man sway you. Dream, and he thinks you're crazy. Succeed, and he thinks you're lucky. Acquire wealth, and he thinks you're greedy. Pay no attention. He simply doesn't understand.

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to be fair, it wouldn't be ANTRX if we stayed on topic.

and if someone wasn't cranky at Chr1s for something he said...

Offline Kranzy

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Re: Picking an Exhaust size
« Reply #6 on: May 28, 2008, 09:13PM »
I've got most of the things together for a turbo kranzy, just lack the money for the rebuild needed lol

If your going turbo in the near future and dont want to do things twice. The bigger the exhaust the better as turbos benefit from as little back pressure as possible. Saves you having to get another exhaust done.

Im sure there are people on this site running 3" exhausts without any dramas on na cars. They might lose a little power but in the end it will be worth it.
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Offline SSS

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Re: Picking an Exhaust size
« Reply #7 on: May 29, 2008, 09:19AM »
Anything from the exit at the merge on a set of headers is inconsequential and only ends up becoming a restriction if the pressure rise is from the inlet at the header merge exit to the muffler tip is high (> 3 psi).

Too big will be noisy, too small will have high backpressure but will be quiet.

It's a balancing act; i've come to the conclusion that an active muffler on a large diameter exhaust (2.5-3" NA) is the best option in terms of balance between noise reduction and torque/power output. (by active muffler have a look at the Xforce Varex)

 

Offline cruizer

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Re: Picking an Exhaust size
« Reply #8 on: May 29, 2008, 11:15AM »
What he said^

You will be fine with a 2.5", especially if you are running a cam, chip and CAI you'd still be comfotable with 3". Don't take my word for it, listen to what SSS, chris and Kranzy say, they know what they're talking about.

Offline noss

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Re: Picking an Exhaust size
« Reply #9 on: May 29, 2008, 11:52AM »
You will be fine with a 2.5", especially if you are running a cam, chip and CAI you'd still be comfotable with 3". Don't take my word for it, listen to what SSS, chris and Kranzy say, they know what they're talking about.

sif they know what they're talking about.. especially sss.. lol  ::)


minimikee.. find another exhaust shop. btw 2.5" (with high flow cat and no resonators with straight through muffler) is rediculously quiet on a ka24e with a turbo stuck in the middle.

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Offline cruizer

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Re: Picking an Exhaust size
« Reply #10 on: May 29, 2008, 02:44PM »
sif they know what they're talking about.. especially sss.. lol  ::)

Jealous I didn't mention you? Jees if only dave-trx could of seen that  ;D

Offline phantom

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Re: Picking an Exhaust size
« Reply #11 on: May 29, 2008, 02:49PM »
Jees if only dave-trx could of seen that  ;D

lol i wonder what he does these days as he doesnt have you to pick on :D

Offline minimikee

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Re: Picking an Exhaust size
« Reply #12 on: May 30, 2008, 05:54PM »
So you all think i should go with the 3" and if i need to build back pressure with the ECV??
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Offline chr1S

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Re: Picking an Exhaust size
« Reply #13 on: May 30, 2008, 08:11PM »
I'd say so.

I had a magnaflow muffler on the rear of mine, 3" no resonators and it was just deep, not loud at all.

Cruising was almost silent for some reason, but when you give it a stab.... ;D
Don't let the opinions of the average man sway you. Dream, and he thinks you're crazy. Succeed, and he thinks you're lucky. Acquire wealth, and he thinks you're greedy. Pay no attention. He simply doesn't understand.

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to be fair, it wouldn't be ANTRX if we stayed on topic.

and if someone wasn't cranky at Chr1s for something he said...

Offline xxxx

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Re: Picking an Exhaust size
« Reply #14 on: May 30, 2008, 08:25PM »
i can only say what i know from personal experience, i have a 2.25 inch cat back with magna flow muffler (not a cannon) and its really quiet...like loud enough to hear easily but not that much louder then stock!

kinda wish i had got 2.5 or 3 inch  :-\
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Offline ashman01

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Re: Picking an Exhaust size
« Reply #15 on: May 30, 2008, 09:15PM »
I cant understand getting a 2.25" Its not that much bigger than the stock 2". I would go a minimum of 2.5" or 3". Tossing up between the 2.

Offline minimikee

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Re: Picking an Exhaust size
« Reply #16 on: Jun 1, 2008, 02:14PM »
It's a balancing act; i've come to the conclusion that an active muffler on a large diameter exhaust (2.5-3" NA) is the best option in terms of balance between noise reduction and torque/power output. (by active muffler have a look at the Xforce Varex)

So in your personal opinion get the 3" system with the ECV ...

Where would you guys put the ECV?? i was thinking between the headers and the cat so the cat doesn't back up
lol Phantom and I at the wreckers
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Offline chr1S

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Re: Picking an Exhaust size
« Reply #17 on: Jun 1, 2008, 04:04PM »
If you want it actually work efficiently and be quiet, put it towards the rear of the car, I know they say to put it before the cat or immediately after it, but I disagree.

I'd just go 3" and a decent muffler and resonator.
Don't let the opinions of the average man sway you. Dream, and he thinks you're crazy. Succeed, and he thinks you're lucky. Acquire wealth, and he thinks you're greedy. Pay no attention. He simply doesn't understand.

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to be fair, it wouldn't be ANTRX if we stayed on topic.

and if someone wasn't cranky at Chr1s for something he said...

Offline SSS

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Re: Picking an Exhaust size
« Reply #18 on: Jun 4, 2008, 01:29PM »
So in your personal opinion get the 3" system with the ECV ...

Where would you guys put the ECV?? i was thinking between the headers and the cat so the cat doesn't back up

I wouldn't use an ECV, but an active muffler as i mentioned. This way when the valve is closed and the system is quiet, the exhaust is just going through a sound deadening path, not just a choke point like an ECV.

Offline minimikee

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Re: Picking an Exhaust size
« Reply #19 on: Jul 18, 2008, 05:26PM »
Well I got my exhaust put in Thursday, after much talking we decided to go with 2.5" piping with a 3" step up to the cat converter then 3". The whole system is mandrel bent with a Xforce Varex muffler on the back.






Overall I am very happy with the results despite what all exhaust shops told me "You'll lose so much power you'll be going backwards mate". Being able to shut it up with the Varex is fantastic.
lol Phantom and I at the wreckers
Me - 'Oi do you have a hammer'
Phantom - 'No, here have an auto-controller' lol

Offline chr1S

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Re: Picking an Exhaust size
« Reply #20 on: Jul 18, 2008, 06:12PM »
lol @ backwards comment!

time to do headwork!
Don't let the opinions of the average man sway you. Dream, and he thinks you're crazy. Succeed, and he thinks you're lucky. Acquire wealth, and he thinks you're greedy. Pay no attention. He simply doesn't understand.

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to be fair, it wouldn't be ANTRX if we stayed on topic.

and if someone wasn't cranky at Chr1s for something he said...

Offline minimikee

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Re: Picking an Exhaust size
« Reply #21 on: Jul 18, 2008, 06:28PM »
atm I'm getting money together for a neat turbo setup. I'm hoping to pull the engine out once and get it all done at once
lol Phantom and I at the wreckers
Me - 'Oi do you have a hammer'
Phantom - 'No, here have an auto-controller' lol