3 inch exhaust. which one. and will it cause problems?

[91canadianlaser]

I am looking to put an exhaust on my 91 plymouth laser rs. i have seen the full 3 inch exhaust and 2.5 . which is better? im not really into big name brands or anything im just looking for function. and also when installing these full exhausts that are 3 inch do you have to have something special to bolt up to the turbo? or do i need the o2 eliminater? and what is this about full cut off? and boost creep? im kinda lost. help me out please i would appreciate it.

 

[iluvmy4g63]

3'in will flow better of course. but can cause boost creep with stock wastegate if your going to get the o2 delete. you have to weld wastegate flapper shut and run external gate from exhaust mani. this set up with 3'in exhaust is pricey. or get 3'in exhaust and get a good port job on your turbo exhaust side. search up (boost creep). you will find a ton of info on what causes it. and how to stop it.

 

[nlzn]

I don't really think welding the flapper shut is a good idea and or necessary in your case.
If you can't live with the slight creep you may experience just port the waste gate, easy to do writeup located @ VFAQ.com

I wouldn't waste your time with 2.5" especially if you ever start upgrading things, you'll want the flow. The true 3" would be a "turboback" (cat back + hi flow cat or delete, down pipe and a good o2 housing would help).

 

[91canadianlaser]

so when i buy the 3 inch turbo back system do they usually bolt right up? and i noticed in some kits that they do not include the o2 housing. so is it necessary to bolt up the 3 inch system? and yeah i do not want to buy something to small for the time being. i plan on slowly modifing it when time and money allows.

 

[iluvmy4g63]

most downpipes are boltons. just shop around. i just got the extreme motorsports down pipe then had the local muffler shop take out the back. so it matched up well. no muffler. be carefull were you live at though. its a hefty fine to run it with out muffler and cat delete. i'am running my wastegate to atmos too. tell ya what though. 4g63 sounds like a beast compaired to a honda

 

[fwdmaster]

Go with a thermal exhaust, had it on both of my lasers

 

[Boosted98gsx]

Honestly, if you're baller and have the money to spend, have a custom exhaust fabbed up for you with V-bands instead of flanges. They don't vibrate loose, nor are there any gaskets to blow out and leak. Having a custom exhaust made (if planned out correctly) can adequately support all future turbo systems with just custom O2 housings made for each turbine housing variation (all mitsu turbos will use OEM flanges in OEM locations, not until you switch to the FP turbine housing, or garretts should you need a new O2 housing). Plus, at this point, you could potentially have an exhaust that you will never have to upgrade in the future.

I would again advise v-bands, and get a quality welder with quality T304 or t409 stainless and mandrel bends and have it made for you. if you check the following link, you can see how my mid-pipe and cat-back were made, so that they would remain constant for the rest of the time I would need a 3" exhaust...

Login to a private Photobucket.com album

There are also a couple vids in there of it idling, also one of my dyno run.

 

[viprez586]

Megan racing 3" turbo back.

Pros: Definite increase in hp+torque.
Stainless steel
Affordable
Hardware included
Good quality + fit
Removable Silencer


Cons: Mild steel flanges
Hangers need some slight tweaking so it doesn't fall off
Loud!
Boost creep
You need a custom made cat if you still have to emissions test, or buy the 16" long resonator, or straight though pipe.


I have run both a 3" magnaflow cat + the MR resonator. The resonator definitely adds to the loudness factor, once i get some spare cash we'll see about running straight through.