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*Insert Evil Laughter*
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Discussion Starter · #1 ·
How important is this? I just put on a DP and was wondering how well the cat back flowed... particularly the sport muffler in itself. I was thinking of doing an unusual upgrade... buying another stock sport muffler from someone on the board.. and having the exhaust split to dual at the first turn and having TWO of the sport mufflers... I would have to block off two of the three pipe holes in each one. Or I could go with two of the smaller ones that come on the tour side... Cheap for sure.. I really enjoy the sport mode sound and wanted something different... So:
1. how important is a cat back system?
2. what part of the stock system is the most restrictive?
3. Do these mufflers flow well enough to consider this?
4. more important to get a high flow cat first? Or do this idea? or get some aftermarket mufflers.
 

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Hellfire Master
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The stock cat back is restrictive enough that it will blow out over time when running an upgraded downpipe. It is a significant restriction.
At the bottom of the page at this link you can see how the exhaust has to change direction a few times to exit the system with the stock exhaust.
http://stealth316.com/images/stim/tim_11-04.gif

If you want a good, cheap, high flowing unit, get the ATR Single Shot exhaust. It only has one tip and one exit, but is is hella light and hella high flowing. If you wanted to be ghetto cheap you could just run and open downpipe, or have a muffler and turndown welded onto the end of it...

devilmanVISA
 

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I've read from most of the tuners that the factory cat back is not overly restrictive until you move into the larger turbos and bigger injectors and all the BPU mods. I just installed an aftermarket cat back (borla), and was using my factory catback and the stillen dp for months with no noticeable degradation in performance based on the exhaust system. I'm told that they really don't get to be a problem until you get your quarters into the low 12s or 11s. Sound with the factory system was pretty nice as well.

Most restrictive part of the factory system is the downpipe, the factory cat back is 3 inches to the mufflers, and after the active exhaust it reduces down to a smaller tube so that is where restriction sets in.

Get a high flow cat or a stillen pipe to eliminate the cat altogether, gut the precats as well. Only reason to retain these is if you have inspections in your state. The cat is a major obstruction in the exhaust pipe, much more than any muffler system out there. Ditch it first and then decide if the exhaust needs to be replaced.

Lord Warlock
 

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I agree with Warlock. The stock exhaust doesn't seem too bad . Maybe once you get into heavy mods, and are running in the 11's it could be a problem. But if you're just around BPU, I'd opt to spend the money on something other than a catback exhaust. Personally, I like ths stock quad-tip look too and sound.

The downpipe is the biggest restiction. Just look at it, easy to see why. Your Melton pipe takes care of that. Rather than spending all that money on a catback, spent $30 on a testpipe and gut your precats. You'll probably see more improvement from those 2 things over any catback setup.

Guess I'm just reitterating what Lord Warlock said, but I agree with him.

EDIT - After checking your sig, I see you already have an upgraded fuel system, gutted precats and 550s. You will probably see a bigger improvement with a catback due to those mods than I will since I don't have any of those upgrades (stock fuel and turbos here). Get a testpipe first though, you can't beat the price.
 

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I remember reading several times that the stock catback is still considered "effecient" until the 500HP mark. The market for the catback exhausts selection for the TT's sucks horribly. THe options break down something like this: (IMO of course;) )

ATR Single Shot- reasonable pricing and excellent performance gains but is still a single exit. Pretty sure its a true 3" all the way but I could be mistaken

ATR Dual Muffler- same as above except that it appears to utlilize a "dummy" muffler set up (like stock catback) instead of using a y pipe to split evenly into 2 mufflers. Basically a single shot w/ an extra muffler attached.

DN Exhaust- WAS my 1st choice. Damn good looking and reasonably priced @ $699 but they are on special order only waiting time and just having to deal w/ DN directly pretty much makes this exhaust very unnatractive. I wouldnt mind getting DN products from a reputable tuner, but dealing w/ Don directly and having him perform on ANY type of a time schedule would be a far cry from reality FOR SURE!! (if you dont believe me read the 5 million pages in the Group Buys section under "Group Buy from DN Performance") Also this is advertised as a 3" exhaust, but as one 3si member had to learn the hard way, the MAIN PIPE is 3" but it splits off into 2.5" at the Y and into the mufflers.

Pitroad M- If your able to go shake the money tree growing in your backyard to have the $ ($1399) to get this bad boy then its a good choice. By far the best looking single exit exhaust on the market. The angled muffler tip somehow balances out the rear of the car and takes away that "where the hell is your other muffler syndrome." Of course it also only weighs 10lbs and is a 90mm (~3.5") set up. Mentionable drawback is that the flange has to be rotated to fit the US spec version, but I believe GT Pro may do this before they ship it out now. (think they are currently fabricating a 100mm (4"!!) version of the Pitroad M which would make it the largest pipe diameter exhaust that is available for our cars. (probably overkill, but ya never know:cool:

Borla- reasonably priced with quality and sound having good reports and is a dual set up, but I cant get past the tips. Guess they could be cut and replaced and rewelded but then I'd be taking a chance on someone elses work which could lead to me getting burned.

JIC Twin Spartan- this is my #1 choice right now, but I'm still gathering info on it. 3" dual muffler and priced at $949 Looks incredible but I havent seen it on a 3000GT yet, so I cant complete my decision, but it definately has cosmetic potential:D Still seeing if the JIC titanium is available but its not lookin good, so the Twin Spartan may be the only choice from JIC.

Bozzspeed- I believe this is a true dual but its priced at $1700 so its completly out of the questions far as I'm concerned .

HKS, Greddy- piping diameter is too small on these for effecient large turbo applications and for the price you'd pay you can walk away with something MUCH better.

Other options are some with aluminized piping (good price but not so great for lasting in the long run), more single exits (kakimoto N1 which i cant stand the chinese writing on the side of the tip), and other local muffler shop jobs.

Lot of options, but not one that is just IMMEDIATELY appealing in all categories. Oh well, decisions, decisions:)
 

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Grandpa
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devilmanVISA said:
The stock cat back is restrictive enough that it will blow out over time when running an upgraded downpipe.

What do you mean blow out? I have been running an ATR downpipe thru the stock back end for two years now.
 

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I will comment that the borla exhaust fits very tight, performs excellent and has a very unique sound. Yes the tips stick out a little more than I like, optimally you'd need to cut them off slice off a inch to 2 inch section then reweld them on and they'd be perfect. But it has dual tips that are functional, and it does a good job replacing the factory quad tips. I'll have to post a pic of mine, Maybe on Wednesday after I lay on some more clear.

Lord Warlock
 

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*Insert Evil Laughter*
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Discussion Starter · #8 ·
Thanks guys.. if I did go with a cat back system I would have a custom thing done or do it myself (welding isn't that hard), rather than pay out all that $ for these premade systems.. but it sounds like I will stick with the stock one for now and get a high flow cat....(environmental thing), compared to a test pipe.. Thanks :)
 

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Maybe you guys should see this link somebody posted to a Tuner - who went from 243 stock Hp to something like 301 Hp on the dyno from just replacing the catback exhaust !!!


:mitsu:
 

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Maybe you guys should see this link somebody posted to a Tuner - who went from 243 stock Hp to something like 301 Hp on the dyno from just replacing the catback exhaust !!!
I'm not saying it won't increase horsepower, I'm just stating that the old exhaust will not cause excessive power loss until you are well along on the mods, and I drive a turbo where the exhaust will likely play a bigger part than a NA.
I'd say the borla probably adds about 20 hp to the mix, as the performance after the addition of the exhaust has definitely improved, but the old exhaust worked fine and did not cause a plateau of power because of restrictive exhaust. It isn't that bad. Changing to a custom system likely won't be much better than the stock one. Provided the DP has been ditched in favor of a better unit.

But I got my position based on information gleaned directly from 3SX, GT Pro and Dynamic Racing. Until you are in mid 12s to the 11s, the factory exhaust flows well enough.

LW
 

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Maybe you guys should see this link somebody posted to a Tuner - who went from 243 stock Hp to something like 301 Hp on the dyno from just replacing the catback exhaust !!!
Also, this was on a stock car and I was quotiing AWHP !!!
Err. You're saying you'll gain 60 AWHP on a completely stock car JUST by replacing the stock exhaust with an aftermarket one? I don't think you'll find one 3si Tuner that will back up that claim. If you can find a 3si Tuner to back that up, I'd like to see them post here and I'll eat my words.
 

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Granted it is a different car and turbo setup but, on the supra you gain an additional 2psi of boost if you have a DP and stock exhust vs. DP w/ aftermarket exhaust. I picked up a full 4psi from (11.5 to 15.5psi) by doing both the DP and exhaust. I would say that is a restriction and the supras stock exhaust is much straighter than the stock 3/s. Granted the turbos are larger but honestly, looking at the stock 3/s exhaust, I can't imagine it being anything but a hinderance. Maybe you won't pick up a ton of HP but it should improve flow.

who went from 243 stock Hp to something like 301 Hp on the dyno from just replacing the catback exhaust !!!
Are you sure this wasn't your car gimmy :).

Actually I have seen dynos of supras picking up 40-50 rwhp with a full DP/exhaust combo (plus the additional 4psi you gain) but 60 is ridiculous. I am curious which tuner did this. I will have to do a search and read about it. That is a lot of power and I find it hard to believe unless they cranked the boost or something.
 

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Gimmy83,
Can you post the link? I've searched for this claim and haven't found it anywhere.

I'm not trying to start a war here, heh. Nothing wrong with disagreements. I'm sure we can disagree and still keep things civil. I hate reading threads where people get at each other's throats. Lets find this post with this 3si Tuner stating 60awhp gains from a catback-only and go from there.

I have just never heard anyone on this board taking a bone-stock TT, adding only a catback and nothing else, and dyno'ing an additional 60 awhp. Granted, it would be cool if it were true, hehe.
 

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I'd believe a 60hp increase with just a Stillen DP, gutted rear precat and an aftermarket catback, but not just from the catback. The factory turbo exhaust just isn't that bad to make a 60hp increase in one jump.
In fact I would have sworn that a 30hp increase with the dp alone is realistic, got laughed at a bit when stated it before, but logically thinking, a tubular exhaust header on a v8 will give 30-60hp, and the stillen pipe offered a tremendous increase on its own, although part of it may have been the gutted precat.

A 60hp gain would be strongly evident as soon as the mod was installed. I just didn't see that much of a gain installing the borla, which is pretty much a straight thru pipe with baby resonators near the end of the pipes.

I too will be happy to relay information along if provided the link you are talking about. Just check out your old thread history and see if you can find it. I do this regularly for folks wanting answers or links that I can remember are in the frequented threads.

Lord Warlock
 

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yeah I HIGHLY doubt that this link will ever "magically appear." Any tuner that would make a claim of 60HP increase on a dyno simply by replacing the cat on a stock car would lose tons of business immediately.
I'm gonna have to give GIMMY83 a :bsflag: on this one. Either your an idiot or you simply misread something.
 
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