Do straight-thru mufflers affect back pressure on '04 GT? Are u/d pulleys worth it?

[72RAW]

I am a newbie to all this and am looking for a little advice. I have a 5 speed '04 GT and the only mod thus far is a K&N cai. I have been looking at and listening to different exhaust systems and have pretty much come to conclusion that it just depends on what sound your looking for. My question is, do straight through systems effect the back pressure the engine needs or can I just throw one on and not worry about it? At this time time I am only looking at doing cat-backs, nothing else.

Also, I was looking for some input on underdrive pulleys--worth it or not and why?? Thanks.

[Nino]

Typical straight through mufflers such as Magnaflow and Borla provide little to no back-pressure. Eliminating back pressure normally reduces low end torque and throttle response while improving top end power and torque. Some back pressure is beneficial to improve low end power.

Not sure what you mean by "can I just throw one on and not worry about it?" What is "it"? What are your concerns?

Pulleys are definitely worth it. They provide consistent gains of around 5-10 ft-lbs of torque throughout the entire rpm range.

-Nino

[72RAW]

What I meant by throwing one on, was putting on a straight through cat-back system and not worrying about having to tune it or doing something else to account for loss of back pressure. Is there a particular cat-back that is recommended or is it all personal preference? I am looking to put one on if I will see gains from it, I don't just want a louder car. Also, I am not partial to straight through or chambered--I don't know enough about either to make an informed decision.

In regards to pulleys--is there a brand that I should stay away from?

Thanks!

[Nino]

Tuning is not required after installing any cat-back. The car's computer can adapt to certain changes and installing a cat-back is well within those limits. Because the stock cat-back has small diameter tubing and stopped-up mufflers, it's pretty restrictive. You'll see significant gains (around 10-12 hp) from installing just about any brand aftermarket cat-back. Some popular brands are Flowmaster, Magnaflow, Bassani, Borla, and SLP. Those are all high quality brands that should give you years of good performance and very similar power gains. If your car is mostly street driven and you're looking for a nice bump in power, I'd listen to all the sound clips and pick the one that sounds the best to you.

As for the pulleys, instead of telling you what to stay away from, I'll say that Steeda, BBK, and ASP are top quality.

-Nino

[kngcbra21]

Go with the Borla Stingers you won't regret it.. :)

[Ghost Rider]

your not going to really notice a loss in low end if you just go with the catback...if you were to pair it up with and O/R mid though...I would say it's noticeable...from experience and yeah, no tuning required like Nino mentioned already

on a side note...straight thru's and chambered muffs sound very different...go with what sound you like not for gains with just the catback...cause your the one that has to listen to it everyday...a few extra hp isn't going to be worth it if you hate the sound :)

[72RAW]

Thanks for all the input. Couple more question about brands. I have heard Flowmaster drone real bad, are there any others that do the same. I don't want to go crazy loud either (don't want to wake my kids or everyone else's at 6 in the morning). Any suggestions from experience?

Thanks again for all the help!

[Nino]

The new Flowmaster cat-backs do not exhibit the high droning that older Flowmaster mufflers use to so I wouldn't worry about that too much. The Flowmasters (as well as the Magnaflow, some Borla kits, and Bassani) are perfectly fine for every day use. You'll notice they are louder than stock but they aren't crazy loud.

-Nino

[72RAW]

What is your opinion on the Flowmaster 50 series mufflers?

[Nino]

Flowmaster 50 series are too quiet for my taste. The 40 series are better sounding and not over the top loud.

-Nino

[72RAW]

I definitely like the sound sound of flowmaster 40's! I just have not been in a car that has them and I all I hear about them is how terrible the drone is.

Thanks again for all the input. I'm sure I will have more questions.

[sganow]

I think the Mac catbacks sound pretty good too. I have heard that the Mac mufflers flow better than the Flowmaster mufflers and drone slightly less than Flowmasters. I have no firsthand experience with them though. Anyone with any input on the Mac catback?

[Ghost Rider]

agreed with Nino...50 series is too quite...and the 40's won't be too loud either if your just changing the catback...also...the drone isn't too bad either if you stay with the stock mid...and it's only around 2200 rpm

[sganow]

My son has the regular 40 series mufflers/catback with an o/r H pipe on his 2000 Mustang GT and it's loud. I would imagine with the stock midpipe with all its cats that it would be much quieter than my son's car.

[Nino]

Yeah, the stock H-pipe make a big difference in quieting down the exhaust.

[Ghost Rider]

^^^waaaaaaaaaay quieter...the mid makes a huge difference :)

[Ghost Rider]

^^^lol damnit...Nino beat me somehow lol :cheers:

wasnt' there when I started replying lol

[sganow]

Hey, Nino is FAST!

[mrtstang]

I am a newbie to all this and am looking for a little advice. I have a 5 speed '04 GT and the only mod thus far is a K&N cai. I have been looking at and listening to different exhaust systems and have pretty much come to conclusion that it just depends on what sound your looking for. My question is, do straight through systems effect the back pressure the engine needs or can I just throw one on and not worry about it? At this time time I am only looking at doing cat-backs, nothing else.

Also, I was looking for some input on underdrive pulleys--worth it or not and why?? Thanks.

No worries with straight through mufflers and backpressure. You will be fine. All catbacks make similar power (you won't be able to tell a difference) so buy what you like based on sound.

I can personally confirm that UDP's do help a little. Even though i couldn't actually feel a difference, it evened up racing with my bros 06 gt. He would always slightly pull me (at that time) on the high end. After i did my pulley's (Steeda's BTW) we were dead even on the high end. There was no mistaking this. We did several runs to confirm.

[I3ulldog]

They effect back pressure but not where you should worry. You will loose torque when you run an O/R mid pipe and straight mufflers on the low end but you'll pick it back up on the high end in HP. But its such a small number like 2lbs torque to wheels on a dyno you would never notice driving around town. Save your money, U/D pulleys aren't going to give you any noticeable gain at all. 2 HP? They can also goof up how your accessories run since the speed changes with different pulley sizes.