Custom Cat Back Exhaust - 3 inch Pipe Size? - 3000GT/Stealth International Message Center

dstehle · 07-22-2007, 09:19 AM

I want to do a custom cat back exhaust on my '95 N/A 3000GT. I was thinking of picking up 2 HKS mufflers and getting all the piping custom done at a local shop. Most likely it will be a y-pipe design with the smoothest air flow as possible. I'm looking for performance as well as sound.

Can I have 3 inch piping for my exhaust? I believe stock piping on a N/A is 2.5? Is bigger necessarily better in this case? Or does there come a point with the N/A cars that it becomes overkill and actually hurts the performance?

Because of emission laws in my area, I will be keeping the stock cat. But would I notice a difference (performance & sound) if I went with a hi-flow cat like the one from Random Tech?

Stealth_E · 07-22-2007, 09:34 AM

I don't think stock piping is 2.5, probably 2.0, maybe 2.25. 3 inch might work for a okay for a catback, just using somebody's old turbo setup for your N/A, but I personally think 3.0 is toooooo big for a non-turbo car, especially dualed.

LUSTFUL · 07-22-2007, 10:22 AM

why would it be too big. The best performance exhaust is wide open, so cut it off at the downpipe. There is a thread running around about scavenging effects and blah blah blah, everyone came to the conclusion that the least restriction possible that maintains velocity is the best choice

dstehle · 07-22-2007, 10:35 AM

Quote:

Originally Posted by LUSTFUL

why would it be too big. The best performance exhaust is wide open, so cut it off at the downpipe. There is a thread running around about scavenging effects and blah blah blah, everyone came to the conclusion that the least restriction possible that maintains velocity is the best choice

So 3 inch piping would be ideal then? And would I have any problems putting a muffler on each side...the fuel tank would allow this to fit?

turbosprentice · 07-22-2007, 07:10 PM

you should be okay, i have a 3 inch downpipe straight down to a Y then exiting to two greddy exhaust, the oil pan will be a problem though you'll have to ben the pipe a bit. my sounds very nice, and haven't been pull over yet, been having it on for a good year now.

vertigospiral88 · 07-22-2007, 07:53 PM

As Lust mentioned -- you may find that you loose a little low end power (as the engine fights to maintain exhaust gas velocity with less volume of gas being produced), but after you begin to find the beginning of the powerband you will notice gains.

So, if you like performance then go with it (the 3 in exhaust will ultimately produce more power).

If you like to feel like you have power around town/don't like to shift (because it's easy for your car to maintain velocity, ie, more bottom end power with the smaller diameter exhaust) then go smaller (say, 2.5 in) and realize that you are sacrificing power when your flow rate goes down at higher rpm (where our engines make REAL power anyway).

Also, it's easy to search -- try it.

Finally, Lust, yes open exhaust makes more power, but only if it's SHORT. The length of the pipes have SO much to do with whether or not the smaller displacement engines can keep up velocity. Side-exit full 3.0 in exhaust would be ideal, IMHO....

LUSTFUL · 07-22-2007, 07:59 PM

I totally agree, that is why I said open downpipe is ideal. There is a damn good reason the outlaw cars have equal length headers that dump right after the front tires, and weight isn't the primary concern there either.

What "I" did that is a good comprimise is went with a single 3 inch piping setup, and then it has a canister at the end. The canister has a removable baffle so you get low end torque with the baffle in, or shift the powerband and open up the flow with the baffle out. It is quite incredible the difference between the two settings. Plus the baffle helps to quiet the system down a good bit if you are in an area that is patrolled alot

vertigospiral88 · 07-22-2007, 08:04 PM

Quote:

Originally Posted by LUSTFUL

I totally agree, that is why I said open downpipe is ideal. There is a damn good reason the outlaw cars have equal length headers that dump right after the front tires, and weight isn't the primary concern there either.

What "I" did that is a good comprimise is went with a single 3 inch piping setup, and then it has a canister at the end. The canister has a removable baffle so you get low end torque with the baffle in, or shift the powerband and open up the flow with the baffle out. It is quite incredible the difference between the two settings. Plus the baffle helps to quiet the system down a good bit if you are in an area that is patrolled alot

Hmmmm.... Never bothered with a baffle/silencer, before -- that's a good idea. I'll have to keep that in mind with my next exhaust fab, being able to manually adjust your powerband is always handy

.

YOGURT! · 07-22-2007, 08:07 PM

3" is too big for the NA. cant make enough power.
2.5 is perfect.

dstehle · 07-22-2007, 08:17 PM

Quote:

Originally Posted by turbosprentice

you should be okay, i have a 3 inch downpipe straight down to a Y then exiting to two greddy exhaust, the oil pan will be a problem though you'll have to ben the pipe a bit. my sounds very nice, and haven't been pull over yet, been having it on for a good year now.

What do you mean "you haven't been pulled over yet"...is it that loud? Obnoxiously loud?

I want a good deep sound, but nothing that is going to have the cops pulling over my car more than they already do now.

Do you have a sound clip of your exhaust by chance?

07-22-2007, 09:19 AM	#1 (permalink)
dstehle 3000GT Owner since Mar 05 Join Date: Mar 2005 Location: Pittsburgh, PA Drives: 95 Mitsubishi 3000GT Trader Rating: (0)	Custom Cat Back Exhaust - 3 inch Pipe Size? I want to do a custom cat back exhaust on my '95 N/A 3000GT. I was thinking of picking up 2 HKS mufflers and getting all the piping custom done at a local shop. Most likely it will be a y-pipe design with the smoothest air flow as possible. I'm looking for performance as well as sound. Can I have 3 inch piping for my exhaust? I believe stock piping on a N/A is 2.5? Is bigger necessarily better in this case? Or does there come a point with the N/A cars that it becomes overkill and actually hurts the performance? Because of emission laws in my area, I will be keeping the stock cat. But would I notice a difference (performance & sound) if I went with a hi-flow cat like the one from Random Tech? __________________ '95 Mitsubishi 3000GT (Caracus Red with Charcoal Leather) Performance Upgrades HP Racing/HP Design HPR5 hyper silver 18x9 wheels Yokohama AVS ES100 245/40 tires Intrax lowering springs (forever on backorder) Ultimate Performance short shifter cold air intake - K&N FIPK filter with DN Performance pipe custom cat back exhaust with dual HKS Hi-Power mufflers Random Technology High-Flow cat Audio System (Dynamat fully lined) Alpine CDA-9885 CD receiver with iPod & Bluetooth kits Alpine CHA-S634 6 disc CD/MP3 changer JL Audio VR 6x5 components (front speakers, tweeters & crossovers) JL Audio VR 6x9 rear speakers JL Audio W1v2 dual 10’’ subs with custom box two TMA 320.4 amps Interior & Exterior Mods 35% black window tint, painted red calipers Mitsubishi Evo VIII 5-speed shift knob, e-brake handle & pedals Mobo leather shifter & e-brake boot combo McGard black lug nuts, wheel locks & custom Mitsu center caps Last edited by dstehle : 07-22-2007 at 09:29 AM.

07-22-2007, 09:34 AM	#2 (permalink)
Stealth_E My Stealth is Confused... Join Date: Feb 2007 Location: Pickerington/OSU, OH Drives: w/o a front plate OH Trader Rating: (6)	Re: Custom Cat Back Exhaust - 3 inch Pipe Size? I don't think stock piping is 2.5, probably 2.0, maybe 2.25. 3 inch might work for a okay for a catback, just using somebody's old turbo setup for your N/A, but I personally think 3.0 is toooooo big for a non-turbo car, especially dualed. __________________ 93 Stealth/GT Hybrid http://www.3si.org/forum/showthread.php?t=393736

07-22-2007, 07:10 PM	#5 (permalink)
turbosprentice i can make your vtech cry Join Date: Jun 2007 Location: sheboygan, wisconsin Drives: '96 3000gt(base) Trader Rating: (2)	Re: Custom Cat Back Exhaust - 3 inch Pipe Size? you should be okay, i have a 3 inch downpipe straight down to a Y then exiting to two greddy exhaust, the oil pan will be a problem though you'll have to ben the pipe a bit. my sounds very nice, and haven't been pull over yet, been having it on for a good year now.

07-22-2007, 07:53 PM	#6 (permalink)
vertigospiral88 Crash diet for car geeks Join Date: Nov 2004 Location: Tahlequah, OK Drives: 1993 3000GT ATX Trader Rating: (1)	Re: Custom Cat Back Exhaust - 3 inch Pipe Size? As Lust mentioned -- you may find that you loose a little low end power (as the engine fights to maintain exhaust gas velocity with less volume of gas being produced), but after you begin to find the beginning of the powerband you will notice gains. So, if you like performance then go with it (the 3 in exhaust will ultimately produce more power). If you like to feel like you have power around town/don't like to shift (because it's easy for your car to maintain velocity, ie, more bottom end power with the smaller diameter exhaust) then go smaller (say, 2.5 in) and realize that you are sacrificing power when your flow rate goes down at higher rpm (where our engines make REAL power anyway). Also, it's easy to search -- try it. Finally, Lust, yes open exhaust makes more power, but only if it's SHORT. The length of the pipes have SO much to do with whether or not the smaller displacement engines can keep up velocity. Side-exit full 3.0 in exhaust would be ideal, IMHO.... __________________ Tom

07-22-2007, 07:59 PM	#7 (permalink)
LUSTFUL Go get bent Join Date: May 2003 Location: Canton Ohio Drives: Just a NA Trader Rating: (0)	Re: Custom Cat Back Exhaust - 3 inch Pipe Size? I totally agree, that is why I said open downpipe is ideal. There is a damn good reason the outlaw cars have equal length headers that dump right after the front tires, and weight isn't the primary concern there either. What "I" did that is a good comprimise is went with a single 3 inch piping setup, and then it has a canister at the end. The canister has a removable baffle so you get low end torque with the baffle in, or shift the powerband and open up the flow with the baffle out. It is quite incredible the difference between the two settings. Plus the baffle helps to quiet the system down a good bit if you are in an area that is patrolled alot

Sponsored Links
3000GT/Stealth International Message Center Advertisement

07-22-2007, 08:07 PM	#9 (permalink)
YOGURT! Import Chop House Join Date: Feb 2001 Location: Rochester, NY Drives: '03 350Z Track Trader Rating: (51)	Re: Custom Cat Back Exhaust - 3 inch Pipe Size? 3" is too big for the NA. cant make enough power. 2.5 is perfect. __________________ As of 1/28/08 I am 3S-less *www.nissanztrader.com* LIVE NOW. TELL YOUR Z FRIENDS! '03 Nissan 350Z Track Edition Super Black Brembos-LSD-Nav-M6 [K&N Drop in][Radiator Cooling Plate][TopSpeed Pullies] [Grounding Kit][PowerLab 3/8"][TopSpeed TP] *13.86 @ 101.3* (without pullies) Ran at NYIRP Former Cars: All Dearly Missed. 2005 Nissan Altima SE-R Black 1993 3000GT Base Red 5spd 1992 Dodge Stealth ES Black 5Spd 1994 Dodge Stealth RT/TT Pearl Yellow 473 AWHP 6spd 1994 3000GT SL Danube Blue 5spd 1993 3000GT Base Green 14.0@101 5spd Nitrous+ Take a look at Fquick, its Myspace for your car!