fastrotaries

When does a 3" exhaust become too small. I know people have excellent power on that diameter, but would a 3.5" or 4" have been better? Finding 4" mufflers is a little difficult. and 3.5" piping is expensive, due to it's uncommon size. I'm running a full 3" but i'm really contemplating something larger. I have to have a new exhaust made...So i thought I would go all out.

GoodfellaFD3S

iTrader: (213)

Contact Zero R here on the forum. He just fabricated me a full 4 inch turboback exhaust, with a magnaflow muffler in the midsection and another in the rear. There's also a magnaflow s/s tip welded onto the back muffler. It's in the mail, so pics coming soon

fastrotaries

4" pipe is easy to find. SS mandrel bent. the adapters to go from 3-4" or 3.5-4" can be easily found as well. I've actually looked into diesel mufflers. I figure if they can handle the heat, why not. But when should you go beyong 3"? I'm in the mid 300WHP figures. But hell I used 3" over 130 hp ago.

GoodfellaFD3S

iTrader: (213)

At that rwhp level you're probably better off sticking with 3 inch, unless you don't mind the noise and want to try something a little different.

BoostedFd3s

iTrader: (3)

hey buddy...how much did he charge you for it? and also did you have to buy the stuff? You know we are both waiting for our 500r kit and are both in need of a 4 inch exhaust... help me out...

G's 3rd Gen

iTrader: (11)

+1 Rich has been my self claimed pick on research before I make the transition. G

vipers

iTrader: (8)

i think 3" is more than plenty for anything @ or below 450rwhp... aftet that, might wanna start thinking about 3.5 or 4"

Turblown

iTrader: (12)

Just because its not restricting power substantially doesn't mean there aren't benefits to going larger.

We don't make anything less than 3.5" on any of our systems. Customers who have switched from cast iron manifolds/smaller downpipes to our systems have noticed over a 1000rpm decrease in " turbo lag"

GoodfellaFD3S

iTrader: (213)

He bought all the materials. For pricing, just contact Sean .

FD Rey

for the power range you're in 3 inches is fine. Heck I only have 3 inches on my car.

13BT_RX3

A couple theories:

I don't think you need the big piping once you get a reasonble distance away from the turbo, due to cooling increasing the density of the exhaust gases. So, if you had a 3" exhaust system already... You could re-pipe to a 3.5" or 4" and reduce at the main muffler back to 3" and probably gain power. It might not get any louder either. I would suspect that a red hot downpipe would be a good place to enlarge.

You could also get a gain from running the wastegate to it's own mini muffler instead of connecting it to the main system.

fastrotaries

Wastegate is vented to the atmosphere. I've talked to several professors at school (ERAU) and they say for flow 3" is good for almost 450WHP. However, that's based on research for a piston motor. As far as pressure differential goes, my turbo is a .96 A/R P-trim that is 3" out. So if I increase the diameter of the exhaust pipe, thus increasing the pressure differential then, lag should decrease and the power curve should change as well. How much? Well I guess time and money will tell. Just thought that someone here had beaten this path already.

Directfreak

iTrader: (2)

Wow, nobody made a joke about the thread title? My boys are finally growing up. *sniff*

crispeed

Size does matter.
If they say it does not and it's all about the motion in the ocean then it's obviously a lie!
Now if we're speaking about 3 inches from the floor then thats a whole different story, Holmes.

Directfreak

iTrader: (2)

Ahh. I was wrong. GDHSF!!

Juiceh

iTrader: (4)

Every time I saw this thread title pop up I thought about it. I actually typed out a smartass responce twice but canceled it.

AImec Racing

well...

I dynoed 500 whp last time, then like we always do by never been satisfied I increased boost, swap the intake from REW to RE/REW TB and port-matched, hardened stationary gears, etc,,, and my target now is 600... i didn't want to expend more on the exhaust so i installed a 3.5" automatic cut-off valve to my 3" downpipe...

i'll test it closed/opened to see how it goes and let you all know...

PDViper77

iTrader: (9)

When she tells you so.......... I mean, I have a 4" full turboback exhaust. I bought 2 magnaflow mufflers and 4" SS pipe from jegs.com and got free shipping. Then I bought a exhaust stack from a semi-truck store in a truck stop (the one that curves at the top and is Chrome) and had the exhaust shop use the straight part as a tip. 4" from turbo to tip. Dont know how much it helped with lag because I did that and my half-bridge motor at the same time. They both helped with lag alot.
This XMAS break I am buying a 4" Vband clamp to have welded in at the bottom of the DP. Then I am buying a 45 degree mandrel bent SS pipe and having the curved part of my semi truck pipe on so it exits by the passenger door like Lupe's exhaust. Should sound sweet. Also I will be able to switch back and forth.

GoodfellaFD3S

iTrader: (213)

Here's a teaser shot

13BT_RX3

----------It's both the size and the motion in the ocean.--------------

fastrotaries

Well I don't plan on staying mid 300's forever. The exhaust on now, was done quickly and hastily. SO since I plan on moving up to a big shaft TO4 within the next 18 months, I might as well build the exhaust to spec now.

iceman4357

iTrader: (2)

I was waiting for someone to make a smart *** remark. I need to upgrade to a 4" i think, T78, half bridge and alcohol injection. looking for 500+ My friend had a 4" and it was sooo loud, but if it spools faster im all about it! Where is ZeroR on this issue?

13BT_RX3

Run dual 3" it's equivalent to one 4.25". Better ground clearance and it should be quieter.

iceman4357

iTrader: (2)

Hu??? Im talking about a 4" turbo out exhaust

13bmaniac

iTrader: (5)

hks has his full racing exhaust with titanium muffler completely 4"piping to mufler is expensive no doubt they have a vid on their website too.