Anyone put on an exhaust yet???

[GTOdriver7]

this question may be a bit preemptive as the aftermarket is still quite new

i was just wondering if anyone has put an an aftermarket exhaust yet?
if so, which one, how does it sound, can you feel any gains?

also has anyone put on headers?

im leaning towards the new SLP exhaust with open shotgun setup and Speed Inc. headers when the time comes. but i wanna know how the stuff sounds.

[redneck]

My understanding has been that the factory exhaust is difficult to improve upon.

[GTOdriver7]

My understanding has been that the factory exhaust is difficult to improve upon.

yeah, thats what i was thinking as well.

[PFYC]

My understanding has been that the factory exhaust is difficult to improve upon.
Your understanding is correct. The exhaust manifolds are pretty nice, not going to see as much improvement with long tubes as you would on other cars. The cats aren't too restrictive nor are the mufflers. And the sound is very nice as we all know. We've made a cat back for the car and I think it sounds better than stock but unlike most other cars it is not a 100% improvement. There just isn't much to work with when the sound is so good to begin with. I like it a lot but I could also live with the factory sound as well. But there are those of us that just can't leave stuff alone. :)

--
Mike Lewis
PFYC

[Rocket]

I really wish I knew what the stock exhaust will sound like with the cats hollowed out? I'd just like that Additional Loudness from the stock exhaust by uncorking the cats. Anyone do it yet? It would be so easy to do because the exhaust system is just bolted together, so you could pull it and work on it on a bench! :cool:

If anyone has done it, please let us know if the tone got raspy or if it even got much louder (It Will I'm sure)! ;)

[Howie]

We picked up 22hp at the wheels with our side exit kit and 34hp at the wheels with our rear exit kit. Contact me if you're interested. Thanks!

[DANSLS1]

I'm personally not so worried about performance gains in going to headers as much as I am about the look. It just doesn't look right w/ that manifold on the big v8 (small v8 really)...
But if I'm going to do it, it's long tubes, x-pipe and high flow mufflers if somebody does one decent - all stainless. I'm hoping there are a couple to choose from by winter so I can have it done by the spring.
Dan

[CMNTMXR57]

There is always room for improvement. While the factory system is a pretty decent setup, it has to be a jack of all trades master of none, which means it has compromises. Federal law has a certain decibel limit that must be abided by (and I believe GM is right at it), warranty cost to replace, performance, resonance, etc, etc.

Most of these aftermarket units you'll find their only concern is...performance and sound. As such, they are much louder, much freer flowing which equals more power.

The stock piping into the mufflers are 2.5", exiting the mufflers they are 2.25" bottlenecking it down inside the muffers to this decreases power, running through stock cats reduces power, running through the stock resonators reduces power. Any restriction in the system will reduce power period.

With that said, I have two MagnaFlow mufflers in place of my stockers. At idle, they are only a tad bit louder, but at WOT are a world of difference in terms of audio and performance.

[READYtoROCK]

I have heard that if back pressure is reduced enough, it will also reduce torque. Does anyone know if this is really true or not? :confused:

[GTOdriver7]

I have heard that if back pressure is reduced enough, it will also reduce torque. Does anyone know if this is really true or not? :confused:


yeah i thought back pressure was a concern as well

[GTOME]

Remember, for every action trere is an equal and opposite reaction. to gian some horsepower you must give up some torque.
Or should i say , by freeing up the exhaust to gain HP, You will lose torque from less restriction

[mistermike]

To the best of my understanding, engines "needing" back pressure is a myth. Most often, using plumbing that is "too large" for a particular situation will cause a loss of velocity in the exhaust gasses, and thereby reduce the scavenging effect of the exiting exhaust. I've never heard of an instance where someone had header primaries that were too big for the intended application and fixed it by installing a restrictive muffler. The physics of engine exhaust is pretty complex stuff, far more complex than an informed lay person such as myself is going to master reading a few magazine articles. Motorcycle builders are generally more in tune with this than car guys, because less than optimum exhaust has far greater consequences on an engine with fewer cylinders, particularly if its pretty well tweaked out of the box. Two-strokes are even fussier about everything being exactly right.

[speed_demon_freak]

The way i look at it is that the exhaust is so good on the GTO that when Borla made a cat back system they only made an additional 8 HP/ 12 ft lbs Torque.

Maybe I'm wrong but we have a good set up right now.



http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?Vi ewItem&rd=1&item=2478195738&category=33630

[GTOsoon]

There is always room for improvement. While the factory system is a pretty decent setup, it has to be a jack of all trades master of none, which means it has compromises. Federal law has a certain decibel limit that must be abided by (and I believe GM is right at it), warranty cost to replace, performance, resonance, etc, etc.

Most of these aftermarket units you'll find their only concern is...performance and sound. As such, they are much louder, much freer flowing which equals more power.

The stock piping into the mufflers are 2.5", exiting the mufflers they are 2.25" bottlenecking it down inside the muffers to this decreases power, running through stock cats reduces power, running through the stock resonators reduces power. Any restriction in the system will reduce power period.

With that said, I have two MagnaFlow mufflers in place of my stockers. At idle, they are only a tad bit louder, but at WOT are a world of difference in terms of audio and performance.


Have a sound clip of those on your car?

[JBraider]

My opinon is there is little HP if any to gain with a catback or muffler change so the only real reason to change the catback is if you want to change the sound (ie make louder). I for one prefer a loud car, but I'm going to wait and spend my money on a good set of long tube headers with offroad downpipes (no cats or resonators) to see how loud the stock catback sounds this way.

I've already seen 35-50 rwhp dyno's on proto type long tube headers on this site, so this is where I'll spend my money first. Then I'll start saving for a Cam!!!! :thumbs:

-JB

[RAZRS EDGE]

How much of a gain could you see if you just took off the cats? Probably about 3-5rwhp? We can get away with that here in Oklahoma :D

[CMNTMXR57]

Yes, anytime you reduce backpressure you lose torque. But it is not a life shattering amount and well worth the offset. The LS1 is a high winding, high HP motor, as such, the HP gain from a more open system fits the bill perfectly.

Once again, the factory mufflers aren't all that bad. There is room for improvement still though. The diameter of the piping out of the mufflers and how it has to funnel down to it (inside the mufflers) is the major restriction on top of the cats and resonators.

And JB, you're wasting your money on putting on headers then not opening up behind it.

GTOsoon, I do, but it really isn't all that much different on a wav. file than the stockers. It's when you get on it that it makes a difference, but I do not have a file of that yet. I have not yet had a chance to hang out of the trunk while someone drives to get my quality sound file. :D

[Rocket]

Just looking from below i see that they CRUSHED the pipes in two places just to make extra clearance for the frame members> so the pipes are really more like TWO INCH MAX> and often more like a inch and seven eigths!

[JBraider]

CMNTMXR57,

Well see if I'm waisting money or not? To me waisting money is buying a catback for $600+ bucks to gain 3-5rwhp! I agree that at some point of higher HP the stock catback could become a bottle neck and I don't like the fact that the stock mufflers exit at 2.25" and run this way out the tail pipes. However, I doubt you gained much rwhp (if any) by replacing your stock mufflers with the Magnaflows. Now if you replace the 2.25" piping with 2.5", then there might be some gains there, but until you reach much higher HP levels, these gains will be small. IMHO......

We can all sit here and speculate all we want, but until someone gets on the dyno and gets some hard facts then all were doing is speculating. I plan on installing my headers w/o cats and w/o resonators and doing dyno pulls with the stock catback attached and detached. This will give me all the information I need to determine if i'm waisting money or not..... If the difference is worth the money, I'll gladly shell out the green backs to upgrade the stock cat-back.

-JB

[CMNTMXR57]

Who said you need to spend $600? That's SLP's price for their new setup. We'll see howm much I gained. I did 314 before, but have yet to get back over to Speed to re-dyno.

I paid about $250 for the two Magnaflow mufflers I put on.

[slick50]

How much of a gain could you see if you just took off the cats? Probably about 3-5rwhp? We can get away with that here in Oklahoma :D

I'm not familiar with catless LS1s but I can say there are no horsepower gains when removing the cats on modified LT1s.

slick50 :drink:

[RAZRS EDGE]

I'm not familiar with catless LS1s but I can say there are no horsepower gains when removing the cats on modified LT1s.

slick50 :drink:
ok thanks :drink:

[Rocket]

my dads 94 roadmaster gained 2-3 MPG by simply hollowing out the cats!
Power.....??????Feels stronger, but I have no proof! BUT they had 100,000 miles of clogging, so it was a whole different story!

back on track here!.............sorry

[speed_demon_freak]

I did 314 before, but have yet to get back over to Speed to re-dyno.

I paid about $250 for the two Magnaflow mufflers I put on.




What do you mean 314?

[CMNTMXR57]

Once again, anything from the factory can be improved upon. One only sees the magic HP number increase, but the factory cats are more designed with effective light off of the catalyst as quickly as possible to get the PCM into closed loop.

While an aftermarket cat is more performance oriented doesn't necessarily mean it won't light off as effectively, but with increased flow, it won't keep the hot gasses trapped inside of it as long as a hi-flow unit. (Which is all the more reason to leave your secondary A.I.R. system in tact if your car is so equipped.)

2-3 hp may be the gain, but remember to multiply that by 2, another few hp from resonators removed x2, plus any gains from modification to anything after the piping.

It all adds up.

[CMNTMXR57]

What do you mean 314?

314 rear wheel hp.

[speed_demon_freak]

314 rear wheel hp.




Just by changing your mufflers?

[CMNTMXR57]

No,

In the context of what I was talking to JB about, I will see what the mufflers will add onto the 314 I already have achieved.

[speed_demon_freak]

oh ok.

[JBraider]

No,

In the context of what I was talking to JB about, I will see what the mufflers will add onto the 314 I already have achieved.

CMNTMXR57,

I'm looking forward to seeing your results.....and I hope there is a significant improvement on the dyno. If there is, I'll be the first one on this board to have some Magnaflows welded in place of my stock mufflers. This was all I ever did to the stock catback on my '99 Cobra that made 347rwhp n/a with only 281 cubic inches.

As for $600, I never implied that you spent that much as I was referring to an entire catback, not just replacing the mufflers. I just think (although I hope I'm wrong) that any possible gains that are to be had over the stock exhaust involves replacing the 2.25" piping after the mufflers. Of course the stock mufflers do have some bottleneck as they have 2.5" inlets and only 2.25" outlets. But if you replace these with 2.5" in and out mufflers, the stock 2.25" piping after the mufflers becomes the bottleneck.

314rwhp is a nice strong running car and I hope to see you gain some hp with the Magnaflows as this means more bolt-on power for all of us, but I'll be very surprised if you see an average gain of more than 2-5rwhp. If you gain more, I'll be the first to congratulate you and admit I was wrong......which I hope I have to do!!!! :)

Good luck my fellow GTO enthusiast and thanks for being the pioneer!!!!

-JB

[CMNTMXR57]

2, 5, 6 is enough to push the total to 320. Keep in mind, much like your Cobra, I have not done a lot of stuff to the car yet, so with only a few bolt ons, the level of power these things make even if only a few at a time, do infact make a difference. :)

Back in the day, I had pretty much all the bolt on mods available (Intake, full cat-back exhaust, etc, etc) at the time to my Camaro and struggled to get 318rwhp out of it. Here I am with almost the same amount with only a Speed Inc CAI.

[fattdaddyGTO]

I'm not familiar with catless LS1s but I can say there are no horsepower gains when removing the cats on modified LT1s.

slick50 :drink:


Dude I had a 01 Z28 and i removed the cats and had hooker longtubes and a flowmaster muff. AND IT F**KIN ROARED!!!! If i lost a little torqe so what I diffently gained power and when (if you do) and a cam & heads it's a world of differance. :thumbs: :thumbs:

[Opticz06]

This is how are long tube headers and 2.5 inch exhaust system sounds you must have real player to hear it.
http://www.moderndaymusclecars.com/gto/exhaustsoun ds.rm

Regards
MDMC LLC

[Old Goat]

http://www.ls1gto.com/forums/showthread.php?t=2510&highlight=backpressure

[OrangeCrushM6]

And take a chance of messing up that kick ass sound now.
NO WAY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1

[CMNTMXR57]

And take a chance of messing up that kick ass sound now.
NO WAY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1

LOL!! You're joking, right! There is soooo much auditory bliss still to be unleashed!

[fattdaddyGTO]

To me I can't even hear it! Soon every one will!

[speed_demon_freak]

Mufflers? What mufflers?

[Opticz06]

Their is a bunch of power to be had in the GTO click the link for our headers, exhaust and 4 inch intake dyno sheet and a 100 shot of nitrous on top of that is on the same sheet.
http://moderndaymusclecars.com/web%20site/gto/gtod ynosheet.htm

[RAZRS EDGE]

Mufflers? What mufflers?
hehehe.......dont forget "Cats? What Cats?" :D

[DANSLS1]

I wonder how much difference it would make if there was no 'cat' material in the cat, with everything else being stock...

[fattdaddyGTO]

I wonder how much difference it would make if there was no 'cat' material in the cat, with everything else being stock...


If you clear out the cat and put a straight pipe in?? If thats is what you mean then you get alot louder tone, and maybe 5 ponys but sound alone is worth it to me!! :D