Does Size Matter? 2.5" vs. 3" Exhaust discussions. [merged]

[Boostin18]

2.5" vs. 3" exhaust discussions are merged here.

I have a 90 GSX and when i bought it the guy said it was full 3" turbo back with a EVO3 O2 housing (ported), now here is my question. When I took the exhaust down, it had a 2.5" exhaust flange at the top of the down pipe and then flares for about a half inch out to 3", if that makes any sense. This is my first 3" exhaust and I was wondering if this is right? I was thinking of porting the o2 housing because it is 2.5", making it 3". Then bringing the exhaust to a shop and having them weld a 3" flange to about a half inch long peice of 3" ehxaust pipe and then welding it on to the whole exhaust. So basically getting rid of the 2.5" flange and the half inch long flare and just welding on the 3" flange with the new piece. Would this make a diffrence if i do this or not. I don't know if this would make any diffrence or not, but when i put a boost controller on, i would try and get it to set at 15psi, but never would it would just spike and go down to like 12 or 13, but never above 15, but never at 15. I also have a ported 2G manifold (havent had it off to make sure it really is ported). Any help would be great!

 

[ricky_rockstah]

I've had a few different exhaust setups on my turbo cars and in conclusion (obviously) less is more. (for HP) As far as driving is concerned, I'd definitely consider an open downpipe problematic in a few ways: sound, safety both at the top.

You're not really limiting much by putting on a free flowing 3" exhaust on our cars unless you've got multiple resonators or cats (which you won't have) you'll be fine and most of the noise will be routed straight out of your 4" tailpipe.

 

[Derek]

If you wanted to keep running an open downpipe, I would say that you should do buy a turn-down exhaust tip, so as to redirect the flow and sound of the exhaust into the ground. That way, you won't have the exhaust gasses blowing right into your floor pan, which is ridiculously loud, since it is vibrating the heck out of your car.

It also will not sound so "detuned".

 

[my_precious]

its an open downpipe, what do you expect? I've added up all the parts and if you have the tools you can make your own custom exhaust (3 inch stainless) for about 200 varrying. i've even seen custom set ups in the classifieds. its gonna cost me 180 or so if i built one.

 

[cmptrphreak]

Ive been running open dp from the time I bought my car, I dont smell anything and the noise isnt that bad. just ### of that one guy told me ## car sounds like shit and then he felt stupid when he got smoked by 4 cars. Only issue is that I think its causing P K.

 

[RedTurboEclipse]

i ran open downpipe.. it was cool for 10 minutes.. it was annoyingly loud and i knew i would get unwanted attention.. if you care for the opposite.. or just dont care.. then just keep doing what your doing

 

[my_precious]

"it was cool for 10 minutes"

 

[impuresoul2k3]

I live in Lincoln, Nebraska too. I run straight pipes on my 1979 Dodge pickup with a 318 and I've never had any cop problems. Even going from a stop right next to them they don't mind.

 

[Dragon Talon]

Always ran a Down pipe. Choped off the exhaust right after the tranny.(Still have old dummy muffler in rear.) It's loud, and illegal for emmisions and the streets.
But it spools real nice, get a good Blow off sound too. Got pulled over once with no question about the sound...And I boosted hella high in front of this pig...
Makes the AWD stand out.But I only roll mine on weekends.

 

[my_precious]

that is strait pipes though. they go all the way to the back. that extra distance muffles it a bit, and plus you live in nebraska. though im suprized they dont get after you cause thats gotta let them know you are there from like 2 miles away when you get on it.

 

[Derek]

Always ran a Down pipe. Choped off the exhaust right after the tranny.(Still have old dummy muffler in rear.) It's loud, and illegal for emmisions and the streets.
But it spools real nice, get a good Blow off sound too. Got pulled over once with no question about the sound...And I boosted hella high in front of this pig...
Makes the AWD stand out.But I only roll mine on weekends.

How are you gettng a BOV sound through your exhaust?

 

[95_E_clipse]

Yeah I don't think you worded that how you wanted it to come out....

 

[Derek]

I think what he wanted to be a 1337 BOV sound was really his turbo spooling down.

 

[1YLOTLN]

Hi, my friend has an SRT-4 with the best exhaust made for it * a SS Dumppipe and yes authorties are really mad at it but i guess not that mad when the clock him going 160 and dont seem to chase him. but a poliece has commented to me and my brother that he will get pulled over if they herd it.

 

[napkinthief]

Hi, my friend has an SRT-4 with the best exhaust made for it * a SS Dumppipe and yes authorties are really mad at it but i guess not that mad when the clock him going 160 and dont seem to chase him. but a poliece has commented to me and my brother that he will get pulled over if they herd it.

I hope he goes to jail, hes either going to kill someone, or himself going that fast on any road, highway or w.e.

I ran without a muffler, and it was annoying as hell. I dont know if anyone would like to run an open downpipe unless its strictly a track or race car. Anything past 3.5 rpms would make my ears hurt.

 

[my_precious]

Obviously people like an open downpipe because many people in this thread have said that it sounds awesome. There are times during a day when NO ONE drives on the highways in certain areas so going 160+ is not necissarily dangerous to others. I agree, it isnt smart, but you cant tell me that you've never thought about doing something like that. I'm not agreeing with it, but don't be putting somebody down over stuff that you can not help. For all you know he is just saying that and that it never really happened. This thread is about open downpipes not an arguement, so cut it out.

 

[mckc]

I've been running open 02 housing the past few months and I think its kinda annoying for everyday driving. It sounds sweet at wot but its stressful to always be on the look out for cops. The gains are incredible when compared to stock exhaust though. 3 inch turbo back sounds alot better than open 02. And no, it hasn't melted anything in my engine bay!

 

[RiceKiller_TSi]

There are times during a day when NO ONE drives on the highways in certain areas so going 160+ is not necissarily dangerous to others.

You're kiddin right?

If you like the open pipe power without the head splitting sound all the time you may want to invest in one of these. Its the best of both worlds if you ask me.


http://www.dmhperformance.com/
http://www.quicktimeperformance.com/QTEC/

 

[Dragon Talon]

Did not word right.
But with open exhaust, for some reason you get a better BOV sound and spool sound.
With normal exhaust you cant hear the turbo, sounds like normal car runs real quiet.
But remove that exhaust or chop it and you get loud, nice sound from your turbo spool, when letting off the gas..
i love to hear that power sound when shifting through gears...

 

[Dragon Talon]

You're kiddin right?

If you like the open pipe power without the head splitting sound all the time you may want to invest in one of these. Its the best of both worlds if you ask me.


http://www.dmhperformance.com/
http://www.quicktimeperformance.com/QTEC/

How good do these work, and can it really work for DSM's?

 

[RiceKiller_TSi]

How good do these work, and can it really work for DSM's?

An open exhaust is not vehicle specific.
The best exhaust for a turboed car is no exhaust at all. Check out the vids on the links. Horsepower gains are dyno proven.

 

[my_precious]

Yeah, electric cut outs are nice for the track. I personally do not plan on running an open down pipe or an open o2 sensor housing though. I was just saying that..

I ran without a muffler, and it was annoying as hell. I dont know if anyone would like to run an open downpipe unless its strictly a track or race car. Anything past 3.5 rpms would make my ears hurt.

this wasn't so because so many people in this thread have already said they like it, or at least that some run it on their daily driver cars without problems.

But it doesn't matter, I dont want an arguement and I really dont care anymore either. Sorry for the inconveinience.

 

[highboostintsi]

i had my dp off for awhile, it got really annoying after awhile. i like it way better with an exhaust because i can auctually hear my bov and the spoolin.

 

[Marc91GSX]

I hey I have all of you beat haha j/k. But seriously I drove a built trans am with uncapped headers 100 miles one way to the nearest exhaust shop with a mandrel bender. I was yelling at people for a week because my ears were still ringing. Sounded great though and I kept getting yee haw from all the red necks I passed. A cop even pulled me over, listened to my car idle for about ten minutes, tell me about how much he missed his car, and then let me go.

 

[2G_RFF_GST]

i tryed that. i have found stock or 2.5 inch down pipes for 50 dollars or so, but for a full stock set up the cheapest ive seen is like 200-300. I have seen used performance 3in cat back set ups for that much. I could just plug up all the holes going into the cabin besides the windows, and have the windows rolled up all the time. Would that work?

i'm sure you can talk the people down on that. I snagged magnaflow exhaust for my Lancer for $80 when it was orignally over $600. It was only on the other car for 1 month. Just convince the seller that it's a POS used part that no one else would be willing to buy.

 

[DragSourceTsi]

I have 3 1/2 that is dumped at the rear axles and it's not loud. It only has one resonator.