Hey guys, so i have 93 single turbo.
borg warner s366 ect ect.
i am running a full 4 inch exausght at the moment. Its not super loud but i wanted to know how much flow im affecting if i reduce it to 3 inches near the muffler.

I know the flow is hudge right after turbo and downpipe. but will i be throwing my 4'' away if i reduce it a the end?

 

Why dont you just put and 4" highflow muffler on the midpipe?

 

you can run a 3" cat back with no difference or issues. You figure egts are hotter closer to the engine, molecules expand with heat so you need a bigger area to reduce pressure but as they cool going down the chassis of the car they dont require as much room to keep preswsure down. So run 4" down and mid and you will be just fine.

 

^ well put thank you. i do have 2 resonators ad a muffler now i just wanted some opinions... ITS LOUD but you cant get quiter with 4 " i guess lol

 

Power level? Goals? Use of the car?

I personally don't see a 3" exhaust restricting you much. 3" is easily good for 500whp. If you don't mind the noise now, why switch?

 

550 - 600hp. street car that spanks those retard evos when i need to. It was just a dumb decision, somebody convinced me that i would gain a reasonable amount. I guess not huh.

 

You can run a full 3" or 3" into 4". Running 4" into 3" is a bad idea. To answer your original question, at a given velocity, a 4" pipe flows approximately 3x as much as a 3" pipe does. If you don't need the flow it doesn't matter though

 

This has been covered many times over the years in both this section and the Single Turbo section.

I've been running a full 4 inch turbo back since like 2007, there are many threads/posts about it and also some sound clips on You Tube.

Sound levels are definitely going to be much louder due to less mass for the mufflers, esp in the midsection...... more pipe=less muffler, laterally speaking anyway.

Further upstream definitely matters more than down towards the rear.

At 500ish rwhp, I certainly don't need the 4 inch, at 600 rwhp I'd say definitely 3.5 inch minimum with 4 inch not required but probably helpful

 

How do you figure its a bad idea? Its been proven that by the time the exhaust reaches mid car its cool enough to condense down and not require huge exhaust.

 

I had a 4" downpipe and midpipe with magnaflow muffler made to replace the 3" pieces, and kept the same 3" catback, the noise levels sounded the same. Then I got a 4" catback pipe made with no muffler to use when I put it on the dyno and go drag racing. Obviously its loud, but on the street it feels about the same until the tires break loose. I'll have it on the dyno soon to see how much more power I can make with the 4" exhaust and large turbine housing which actually made my car faster even at lower rpms.

 

well ill actually post some pictures up tonight. I have 2 16 inch resonators and a 14 '' muffler going on today. Making it quite enough to sit in the car without a headache is possible but hard.
Which in reality is the goal, to have alot of flow but not too loud.

Plus its pretty awesome to have a 4'' polished dolphin tail shooting out fireballs half the size of my car.

 

^ tom, enzo tune your car ?

 

No I tune my car. 1st try engineering made the exhaust

 

Vid clip of this loudness?

 

bad video this is no muffler. trust me its loud. if i normal drive it there are people screaming at me. and i wil show you what its like with a muffler.

http://www.youtube.com/watch?v=dp4qi...w0PCYzLz1bzWFt

 

not to thread jack, but what do you think about having a 4inc exhaust with a butterfly, splitting one side going to my 3inch racing beat(really dont want to give this up) for city driving and to keep noise level down, and the other just a straight exhaust aiming straight down.

 

kindof like a Y pipe. 2 butterflys keeping the 4 inch closed and the 3 inch open then 4 inch open 3 inch closed? Sounds like a very cool idea. will be a alittle pricy tho.

look up how much a j bend for a stainless 4 inch exaughst is.. just so you get an idea.

but if you want it i think it would be ok. although youll have to check with your tuner if its ok because your changing exaughst back pressure.

 

Ohh that video is you lol. I forgot. Doesn't sound that loud but video doesn't do justice in terms of sound and quality of sounds for cars.

 

yea ill take a better one

 

Well I don't think it would be a problem for the tuner, let it get tuned with the 4 inch and just change it to 3 for normal driving shouldn't really do much since I'm not wot when it's 3" . I just don't want to loose my cat back but I want more flow than what the rb dual can do when I go single.

 

i went 4" to a 3.5" greddy....i will know how it sounds with a 3 rotor in a few weeks

3 rotors arent as loud as 2 rotors either way

 

what about running a apexi acv

 

but they sound much sexier.