With stock exhaust, I think both sound pretty much the same. Though, it is hard to tell anymore because most of my friends who own GTOs have already replaced their exhaust with aftermarket ones.

Russ

 

I had posted a thread not too long ago about the exhuast systems being different in the way there setup on the 04 versus the 05-06. I have long tubes with cats and slp loudmouth and I had heard an 05/06 at a car show with the same setup and my car seem to be alittle bit louder and mine also crackles and pops really loud and his barely did. If you look at the exhausts systems both aftermarket and stock the mufflers on the 04s are towards the middle of the exhaust while the mufflers on the 05-06s are right before the tips. The way the piping is setup between the 04 and 05/06 could have alot to do with them sounding different, but I think they all sound great no matter what 04-06 stock or with aftermarket systems too.

 

I had posted a thread not too long agoabout the exhuast systems being different in the way there setup on the 04 versus the 05-06. I have long tubes with cats and slp loudmouth and I had heard an 05/06 at a car show with the same setup and my car seem to be alittle bit louder and mine also crackles and pops really loud and his barely did. If you look at the exhausts systems both aftermarket and stock the mufflers on the 04s are towards the middle of the exhaust while the mufflers on the 05-06s are right before the tips. The way the piping is setup between the 04 and 05/06 could have alot to do with them sounding different, but I think they all sound great no matter what 04-06 stock or with aftermarket systems too.

I think the placement of the mufflers, as you said, has much more to do with the difference in the sound than anything else.
On the 04, the resonators are pretty much in the middle of the car, and are seperate, and the mufflers are just ahead of the rear axle. On the 05/6, the resonators are in tha same place, but are enclosed in a quasi-muffler looking gizmo, and the mufflers are all the way at the back end of the system. That is what make the difference in the sound.

Russ

 

I personally think the '04s have a sleeper sound to them. you can hear the 05-06s a little more at idle. although I don't intimately know an 05-06 i know that my '04s stock exhaust doesn't get loud until after 3grand. and it does seem to crackle and pop more than 05-06s? maybe the timing and resonance factors? not like I really understand exhaust systems.

 

Not sure

I know one thing, no matter what it is, I like the sound of the flowmasters!

 

I read everything possible when the new GTO was being introduced. I know that engineering of the exhaust system held a priorty for function and to get that perfect sound. The goal was acheived however the 04 sales did not meet expectations. They figured out that we need to see duals coming out of the back so they redesigned the exhaust for 05. Don't know what that did to the sound but the above explaination sounds good to me.

 

You are right about the engineering that went into the 04 exhaust to create just the right tone. In the book, "GTO, Return of the Legend" they discuss how they built 50 mock up exhaust systems and used recordings of the original 64 GTO exhaust to create the tone that they wanted. Anachoic testing was used to narrow down the field of designs to just 5. Then they were installed on the prototype cars and specifically tuned to have the deep, throaty GTO sound. The change in the design for the 05/6 was basically a cosmetic change to quell the critics who balked at the fact that the new GTO had a euro-style dual side out exhaust. God forbid!

As far as sales expectations, the GTO never met them in any of it's three year run. GM had planned on a max of 18000 units/yr. This was the maximum that Holden's Elizabeth Australia plant could produce. The 04 was the best year for the GTO, with almost 16000 units sold, compared to just over 11000 in 05, and nearly 14000 in 06.

Russ

 

For me I really can't say which exhaust sound better because what I may think sounds great may sound like crap to someone else. Some think that just because an exhaust is loud (SLP Loudmouth 2 or certain Flowmasters) it sounds good. I don't. Some think that an exhaust that sounds raspy (mainly Corsa) it sounds good. I don't. I like exhausts that has a deep mellow tone, which is neither outrageously loud or raspy. I've replaced Flowmasters with MagnaFlow. If I would have kept my '98 Vette I would have pulled the Corsa catback off and replaced it with MagnaFlow as well. Now throw in headers, high flow cats, resonator delete, straight pipes, x pipes and h pipes in the equation and that really mix things up. When I hear an exhaust that sounds mean I always want to look under someone's hood and underneath their car to see what they have. I know some of you may asked that I get banned from the forum for what I'm about to say but I do like the stock sound of the Mustang GTs. They have a sound that is just right in my opinion.

 

First, I always have liked flowmasters which I've put on many of my vehicles. My opinion I know. But, I deleted the resonator with straight pipes and put on the new Flowmaster 44 series and it has a nice deep sound to her. Not raspy at all. When slowing down, I dont get any popping sound like some have expalined. I do however get a nice rumble. While at cruising at speeds between 60-75 the engine is pretty quiet, no drone, can't hardly hear it too much, just a smooth rumble. At idle and speeds up to 55! No that is a differnt story, then you get a nice deep rumble! I believe the sound in the interior of the car is not as loud is due to the muffler placement behind the axle on the goats!, but I could be wrong.

For the record, Mustangs have always had that unique sound to them. A friend had a, I belive late 80 or early 90 GT, and put flowmasters on it. You could still tell that it was a mustang coming.

 

The SAP exhaust has a more deeper throaty sound. I noticed it as soon as it was installed.