searched through a few exhaust threads back and forth. right now i have a full 4" and its way too loud. i am looking to do 3.5" dp and mp into a 3" cat-back. want to keep the sound down and try and keep the power up enough. i also want to re route the wastegate. but is 3.5" enough or will 4" still be needed to reach 600whp with decent egt temps? i have done 591whp but the egts are very very high. that was on a 3.5dp 3 mp and 3 cat back. any imput appreciated.

 

Hey

I have been running a 4" exhaust for a while now and it's quiet. I used to run 1 coastfab muffler in the middle and a Magnaflow at the back. And ppl where saying my car was so much more quieter then others with aftermarket 3rd gen exhaust systems that was 3". And it was quiet. And i was running a full race bridge port and a big singel.

Redone it some now, so got 3 magnaflow 4" mufflers on it. And looking forward to starting it in about 2-3 weeks.

JT

 

My 4" from A-Spec (short Magnaflow resonator in middle and big Magnaflow muffler out back) is way too loud too. I am going to rework it with two Borla XR-1 mufflers and expect it to be much quieter.

I was going to move to a 3.5" system too, but it was going to cost me double what the new mufflers cost.

 

I would stick with 4", I have done a 4" system with 1 muffler in the back and it wasn't terrible. You just need a large muffler, I built a 7"x18" cased muffler for it and packed the crap out of it.

 

just for the record smg944... i have a 3 inch exhaust..... so 3 in is enough


i dont have a 3.5 in just because of the noise level


had straight pipe and it was annoying as hell


power wise between 3 & 4 in is a difference but not noticable...However spool difference between 3 & 4 in exhaust is a hell of a difference

 

Do you log your EGT's?

 

ill have to take a look on the microtech and let you know

 

rxtacy i noticed 400 f change in egt from 3" to 4" which is huge but the noise is the issue i would like to control. im looking into setting up a somewhat quiet 4" setup with 1 muffler and 3 resonators.

 

How about a sound clip of your car idling? Most FD's I've ran into with after market straight pipes are usually loud. Quiet exhaust will usually result in restriction of some sort. 4" with several resonators may just do the trick.

 

I started with 4inch setup with 2 x2stage mufflers from burns stainless but was way too loud.. ended up replacing them with 2 magnaflow oval (canister size 5.5inch) it was much quieter but still was too loud.. I am also considering the Borla xr1 but I dont know if they gonna be any more quieter than the magnaflow ones

Let me know when u try them. Thanks


As for the flow I believe it will be ok.. other cars with 4 inch are over the 700whp and it doesnt seem to be restrictive. Im only guessing based on this. I have never tried the 3.5" setup

 

I built midpipes with both a magnaflow and a borla xr-1, and the magnaflow was much quieter.

 

Wow, that is a dramatic difference. You were measuring EGT pre turbo correct? We did a 4" split to two 3" magnaflows on my buddies FC. It's actually not bad when its flowing through the exhaust. It also has open dump tubes though, so when the waste gates open it gets pretty loud. I know the FD isn't set up well to run a split like that, but food for thought.

 

I want vids!!!

 

yea pre turbo egt was where i was getting the temps from. the fc's have an advantage since the dual 3" can flow enough to cover a single 4" and still maintain some quietness

 

so smg944 whats the update

 

My old A-spec full 4 inch was retarded loud with a pair of Magnaflow circular mufflers, one mid and one rear. Once I switched to a rear Apex'i GT Spec it was about perfect, received many many compliments on the exhaust noise on the street and at the road course, this with a re-circ'ed WG. I also had an ATS which was very useful to jam in the tip late night when 1 block from home and trying NOT to **** off all the neighbors

 

Rich I think that's what I'm going to try out. 4" with 1 magnaflow oval and a apexi gt spec cat back . I recently tuned a car with one and it sounded good, and if I go on a long drive to a show I can pop in the silencer which works very well on that exhaust for some reason . Almost half the sound.