Which would increase power more?

[Denji]

After much research it comes down to pretty much this question, which will make more power on my car (with a t28)

1. a 3 inch exhaust with a stock muffler
2. a 2.5 inch exhaust with a performance muffler

please give feedback for both a catback and turboback setup of the above description.

considering the ultimate objective was to run nothing faster than a 13 second 1/4 mile

strict exhaust laws have got me searching for alternatives for power gains while remaining more stock looking.(please dont suggest exhaust dump tube, as i am considering using one but would like to explore a more permanent power gain all of the time)

 

[herovueboi]

Really depends on your goals, but I think 2.5 is fine especially with a better sound than the stock tips.

 

[Denji]

for me, the quieter the better!

 

[herovueboi]

I'm sure the 3" is nice, but that muffler would be chocking it really. When I got my 3" RNR, it felt, sounded so much better than my stock muffler. Since I have a 2.5" dp, i think it would just go better going from 2.5" all the way back instead of 2.5-3.0" all the way back. If you prefer quiet, get a magna flow muffler, I have one on my 240sx and I think it's just as quiet as a stock muffler, while being a 2.5" inlet.

 

[Denji]

yeah, i was pretty sure it would choke it to an extent, i suppose i was hoping that it would be less restrictive than the 2.5 with something like a magnaflow on it.

 

[yoshimitsuspeed]

I have a 3" turbo back with an Apexi muffler. With the silencer removed it is very loud and flows awsome but I can put the silencer in and it is pretty much quite as stock. The
1 1/4" silencer restricts the flow a bit but the power loss is not extremly noticible during every day driving. One other thing I have thought about doing is making a 2" silencer which would be louder but flow better. I also don't have my cat installed yet, with a cat and silencer it would be very quiet. I also got a 3" resonator or what they call high flow cat, if I installed the cat and the resonator I think it would be pretty quiet even without the silencer. Are there any laws other than sound that worry you?

 

[90LaZeRrst]

that would be absolutely stupid to leave that stock POS on there with ANY modified exhaust. 2.5 is a waste of time unless you are FOR SURE you wont be modding too much. The worst is to pay for a 2.5 exhaust then upgrade to 3.0 later heh. Whichever you do, make sure to have a better muffler ( not huge, but a 3 inch cavity at least)

 

[90LaZeRrst]

I have a 3" turbo back with an Apexi muffler. With the silencer removed it is very loud and flows awsome but I can put the silencer in and it is pretty much quite as stock. The
1 1/4" silencer restricts the flow a bit but the power loss is not extremly noticible during every day driving. One other thing I have thought about doing is making a 2" silencer which would be louder but flow better. I also don't have my cat installed yet, with a cat and silencer it would be very quiet. I also got a 3" resonator or what they call high flow cat, if I installed the cat and the resonator I think it would be pretty quiet even without the silencer. Are there any laws other than sound that worry you?

Dude, you can look at it and tell. you go from like a 4 inch hole to a 2 inch hole. THAT IS RESTRICTING FLOW LIKE NO OTHER. Just because you cant see it doesnt mean its not there. You are just choking the circle of life. It cant exhale as fast as it can inhale ( unless its n/t then it doesnt matter really )

 

[Denji]

ugh, i think i will just go with the bosal exhaust and call it a night. The laws here permit a cop to give you a ticket for any exhaust he can see that is not stock. Maybe a resonator would do something for the sound levels.

 

[yoshimitsuspeed]

Dude, you can look at it and tell. you go from like a 4 inch hole to a 2 inch hole. THAT IS RESTRICTING FLOW LIKE NO OTHER. Just because you cant see it doesnt mean its not there. You are just choking the circle of life. It cant exhale as fast as it can inhale ( unless its n/t then it doesnt matter really )

I didn't say it doesn't restrict flow. I hate having it in there but I would rather it than one of the other options posted here because all I have to do is knock out a butt plug and have full performance. I put it in after getting a noise violation ticket but I have taken it back out because I hate it. If I do get pulled over I will just tell them the retainer bolt fell out and I will fix it when I get home.
Hope it works.

Denji I have no Idea how they are in (I forgot where you are, I think virgina) but around here cops care about how it sounds, not how it looks. If I threw on an eight port exhaust I don't think any cop would care as long as it wasn't loud.

 

[Denji]

i guess its the price i have to pay to have what i want, i'll take a risk, like i said i coudl always throw a resonator in there to help keep it quiet, thank you for your help. I simply am at the point where it is time for an exhaust to make more power and get sufficient airflow to see benefits from a larger turbo.

 

[yoshimitsuspeed]

i guess its the price i have to pay to have what i want, i'll take a risk, like i said i coudl always throw a resonator in there to help keep it quiet, thank you for your help. I simply am at the point where it is time for an exhaust to make more power and get sufficient airflow to see benefits from a larger turbo.

Deffinately go with 3" then.
A cat will quiet it down a bit, you will loose a bit of flow so if you want to race you could get or make a straight pipe too. I got a cat after I found out you can get fined over $1,000 here for not having it. I doubt a cop will look under my car but if they did I would be screwd. a resonator will add a little restriction but deffinately better than a smaller diameter system. There are also quiet mufflers out there if you want to spend the extra couple bucks, I have heard good things about the magnaflow as far as being quiet. Of course the coffy cans are nice since some of them do come with a silencer.
Good luck

 

[90LaZeRrst]

high flow cat, wont pass you in emmissions, but it sure as hell will keep a cop off your nuts if he trys tagin ya for that.

 

[yoshimitsuspeed]

high flow cat, wont pass you in emmissions, but it sure as hell will keep a cop off your nuts if he trys tagin ya for that.

I have heard of real 3" high flow cats passing emissions. Just watch out for the resonators they sell as high flow cats if your shopping on ebay. Get a magnaflow or something.
If it looks like a torpedo it's a resonator, it will also say somewhere in the add in micro print for off road use only. If there is any doubt ask the seller.

 

[90LaZeRrst]

I have heard of real 3" high flow cats passing emissions. Just watch out for the resonators they sell as high flow cats if your shopping on ebay. Get a magnaflow or something.
If it looks like a torpedo it's a resonator, it will also say somewhere in the add in micro print for off road use only. If there is any doubt ask the seller.

hook me up with one of these 3 inch cats passin emissions! I like my shit NOT so smelly and NOT so loud.. sooooo i want me one!! muhahaa.

 

[yoshimitsuspeed]

hook me up with one of these 3 inch cats passin emissions! I like my shit NOT so smelly and NOT so loud.. sooooo i want me one!! muhahaa.

I don't rember what brand it was. I haven't put my magnaflow on yet but it better work when emission time comes around. I hae seen threads on here talking about it and I have heard of them working.

 

[Denji]

haha, we dont have emissions testing here! imagine that. Strict as crap about exhausts with no emissions testing...

 

[Dieselboy]

Why not go for a straight 3" exhaust from the turbo using a 3" through stock-looking dual tip muffler and a resonator or two to lower sound output? Dre used a full 3" with a stock looking muffler (but no resonators) and has gone low 11's on that exhaust setup.

 

[Denji]

def. my plan.. the bosal exhaust tip mimics the stock exhaust. thanks for all the replies..more definitely welceome and appreciated.