3 inch vs 2.5 inch Exhaust.

[Hruke]

So i'm going to buy my exhaust next, and am debating what would be better in terms of performance. But also I want to take in to consideration the money vs performance aspect, not going cheap or anything but if i can buy a full turbo back exhaust for ~800$ vs buying a MPFab downpipe/midpipe for ~600$ and having someone make a 3 inch catback or wait for one to come out. I'm just curious if the gains i would see from a 2.5 inch to a 3 inch exhaust would be worth the extra ~200-300 dollars or more, or if I should take that money and invest it into something else. But right now i'm at the point of pretty much MPFab's exhaust vs ZZP exhaust. Which to my knowledge MPFab dosnt make the catback section quite yet. Or if you know any reason on why the 2.5 inch is better then 3 inch. Hope to hear everyone's opinion on this.

 

[rdss]

I would buy the MPFab down and mid pipe and run ZZP's 2.5" cat back. I don't think the 1.4t has enough exhaust flow that there would be a disguiseable difference between 2.5" vs 3".

 

[Insanika]

I was just weighing this myself. Wondering if there would be a big issue.

 

[Maddmatts]

I'll be very impressed if someone actually tunes a 1.4T to the point of needing a 3" exhaust. 2.5" is more than plenty for 99% (there's always that one guy...) of the builds we'll ever see here.

I can't remember the formula for gas flow vs diameter, but the relationship isn't linear. A small increase in pipe dia makes a big increase in possible flow.

 

[Hruke]

So I don't know how true this is, and if so how much we would be "losing" But I always hear the bigger the better when it comes to exhaust. From what I read this is both true and false because the bigger pipe will allow more time for the gas to cool down and cold air is dense air, and dense air is heavy air therefore slowing down the flow of the exhaust, causing restriction. The whole point of upgrading the exhaust is to eliminate the restriction, but i'm not sure how much restriction it will cause (probably not even a noticeable amount) but still something I was reading about.


And another thing I noticed when comparing the Anaconda vs the ZZP exhaust. The Anaconda gives 15WHP and with the ZZP downpipe midpipe and high flow cat you gain 13-14HP, and ZZP says after the cat you will only see minor if any gains and will only cause a change in the sound. So for $560 you can get 15WHP or you can spend $540(with high flow cat) or $490(with test pipe) to gain 13-14HP so all in all the price to performance aspect is pretty much cut out and comes down to which one you would prefer, with a $20 or $70 difference and a sound difference from the cat.

Again thanks for everyone's help i'm still very undeceive about what exhaust I want to buy.

 

[laborsmith]

Please point me to a ZZP post that indicates a cat-back will result in a little or only an incremental power gain.


Laborsmith

 

[Hruke]

Please point me to a ZZP post that indicates a cat-back will result in a little or only an incremental power gain.


Laborsmith

Okay so I read it wrong and it says is most commonly upgraded for sound.

The 4th and final piece of the exhaust is the catback. It has the resonator, muffler and tip. It is the most commonly upgraded part of the exhaust and determines the sound of your exhaust system. Upgrading this section does not require any tuning or affect emissions in any way.

My bad.

 

[NewZJ]

I have the MPFab down and mid pipe and zzp catback. I love it.

 

[SoCalRs]

I have the MPFab down and mid pipe and zzp catback. I love it.

this is lame but let me be the one to ask lol so as a few previous post explained if you changed the down and mid pipe where most of the Gain is and left the factory stuff on I dont know who would or has ? to save a penny but just in case they would since most of the HP gains are in the down and Mid section more than the Cat Back area will they see a HP gain and still be quiet as a mouse ????

 

[NewZJ]

I don't think it will be as quiet as stock, it will be a little louder, and you get the hp gains still

Edit: reduced gains

 

[sonichead94]

orrrr you could go the e-cutout rout.
have the best of both worlds

 

[laborsmith]

I don't think it will be as quiet as stock, it will be a little louder, and you get the hp gains still

But it seems any potential HP gain would be given up by maintaining the 1&7/8 inch oem exhaust the rest of the way.

There are HP gains in doing a cat back. There have been enough dyno charts posted on this and other forums that no one should now be questioning that concept.

I originally wanted to go the e-cutout route but could not and keep the resonator so I went cat back.


Laborsmith

 

[NewZJ]

The entire exhaust is restrictive, I was under the impression that the front half was more restrictive. After checking some posts it looks like the catback restricts most gains that changing the down/mid pipe would provide.

The catback will be the best bang for buck but keeping it super quiet will add extra cost.

 

[MPFab]

A couple of things... The Anaconda gives 15whp on a stock tune. It also includes a 100cell high flow cat.
The best bang for the buck is not a cat-back. From my testing with the Anaconda, I only picked up 4whp and 6wtq by completely removing the stock exhaust system. I said stock too.. There is no way ANY cat-back produced will flow better than no exhaust. This was one of the reasons I opted out of building one to sell. Bolt an Anaconda on with the stock exhaust and have 98% of the power, without all the noise.

 

[skiwrench]

I run a 3" exhaust on my firebird (5.7L, 390 RWHP.) I think the 2.5" exhaust would be more than enough for the 1.4L in our sonics...

 

[SoCalRs]

Right up my Turbo....

A couple of things... The Anaconda gives 15whp on a stock tune. It also includes a 100cell high flow cat.
The best bang for the buck is not a cat-back. From my testing with the Anaconda, I only picked up 4whp and 6wtq by completely removing the stock exhaust system. I said stock too.. There is no way ANY cat-back produced will flow better than no exhaust. This was one of the reasons I opted out of building one to sell. Bolt an Anaconda on with the stock exhaust and have 98% of the power, without all the noise.

Now thats Right Out my turbo ... I be Bringing you My piggy bank soon I want power and stealth looks Like you have it ...

 

[rs_sonic]

What if I went with an MPFab Anaconda, with an e-cutout, and the 2.5" ZZP catback (with the muffler)? Is that overkill in terms of cost? This way you get the benefits of a semi-quiet system when the cutout is closed? Just a thought...tell me if I'm crazy.

 

[EndlessSea]

2.5" has been proven effective up to 400+whp. you don't need 3" on a 138hp 1.4L engine. hell you probably "technically" don't even need 2.5". although im sure it will help spool time and such.

But to answer the question. the engine is so small and puts out such a small about of hp that the extra .5" wont make a difference. I've seen T3 powered Miata's(my buddy's) put down 253whp with a 2.5" exhaust.

 

[2014 Blue RS]

A couple of things... The Anaconda gives 15whp on a stock tune. It also includes a 100cell high flow cat.
The best bang for the buck is not a cat-back. From my testing with the Anaconda, I only picked up 4whp and 6wtq by completely removing the stock exhaust system. I said stock too.. There is no way ANY cat-back produced will flow better than no exhaust. This was one of the reasons I opted out of building one to sell. Bolt an Anaconda on with the stock exhaust and have 98% of the power, without all the noise.

Sounds perfect. Most power without the excessive noise for daily driving.
Is this what I need? The whole combo? Just ordered tune today so I'm considering my next step.

MPFab 3″ “Anaconda” Down/Mid/Catalyst pipe combo for Chevy Sonic 1.4LTurbo