Folks! I need some advice from Flowmaster people. My 2004 w/5.4 3v has a SISO Flowmaster 40 setup. The stock muffler was simply replaced. I'm thinking of replacing this with a SIDO setup. I like the sound of what I have, but could stand a little more sound, and hopefully a little better performance. I can get it done for a measly $205 without tips, $240 with tips. The muffler guy I use, widely known in my area for damned good work, tells me I might lose going with a true dual setup. He recommends the SIDO.
Will the SIDO sound better than my SISO setup? Will there be a real difference? I don't think I want to go as loud as true dual.

Please give lots of advice with lots of details. Thanks.

 

If he only replaced the muffler go with 3" pipe from the collector all the way back. The system I have is a magnaflow 5x8x18, 3" offset (p/n 12259) with 3" pipe and a 4" SS tip. Deep and throaty with very little droning in the cab. The SIDO system you spoke of may be too quiet for you. In the SISO systems the Magnaflow tends to give a little better performance over the FM. If all you want is noise go with the FM.

 

i put true duals on my truck, because the flowmaster 40 wasn't loud enough, and i cant feel any loss of anything

 

Your SI/SO will sound deeper than a SI/DO, but the SI/SO will be quieter and the SI/DO will gain a little more performance and loudness. My F250 has a Flowmaster 40 SI/DO with a 3" system & 4X22" black tips. It sounds great on a slow takeoff & the idle, but under heavy acceleration it sounds like a diesle almost.

True Duals is the best way to go, it will be deeper & louder, running 3" pipes with two SI/SO Flowmasters.

If you go with a SI/DO system and have the Flowmaster lying around could you consider selling it to me for a reasonable price? ws6_guy06@yahoo.com

 

The only thing you'll lose with the true duals is $$$ if you're not running headers. Otherwise, an SIDO w/side exit in front of the tire (Lightning style) will make for a louder sound. My set-up is 3" from the Y pipe, SIDO, side exit with no tips, just painted the pipes black to go with the truck. The sound is loud, deep, and rumbly. I really enjoy it though I do believe that I'm losing a little in performance with them. It's been well documented in this forum that Flows slightly decrease performance but put out a great sound. The Magnaflows on the other hand are proven to increase performance but the sound is a little less. So it's 6 of one, half a dozen of another, take your pick.

 

SI/DO is far better than SI/SO sertup when it comes to aftermarket exhuast if you going to leave it a SI/SO why not just leave the stock muffler on it. But true dual straight pipes are the best if you want it to sound loud.

 

I appreciate the advice, and it's want I wanted to hear, but be real. A single-out Flowmaster is better than a stock muffler any day. Sound and performance were vastly improved. I just wanted an idea of how much better those two factors would be by going SI/DO. I'm afraid true dual is out of reach for me now.

 

dixie150scab how did your setup sound? Im debating on whether or not to do that. I just wanna drop the stock muffler and put a 40 or 50 series in just havent decided yet. How loud is the 40 series on that setup?

 

Sorry. Double posted.

 

Yeah, I just originally dropped the stock muffler for a Flowmaster 40. It sounds really great. A nice low rumble. Powerful. I just want a little more. That's why I'm considering a SI/DO, although a lot of folks are telling me what I'll get probably isn't worth the money. I may just stick with the SI/SO.

In short, do it! It's worth the money for the performance increase as well as the sound. Couple that with an Airraid Jr. and a K&N drop-in filter, and you'll see throttle response increase like you never imagined.

Those three mods alone woke up my engine.
Flowmaster 40.
Airaid Jr.
K&N drop-in.
Total cost-$250

 

I was thinking about adding the same setup besides the K&N. Ive had bad luck with them maybe that setup with a AMSoil dry filter.

 

Why have you had problems with the K&N filters? I admit, I was apprehensive about using one at first, but I've maintained mine properly, and there are no problems to be seen. I've cleaned the MAF sensor shortly after installing a new one or after re-oiling to prevent issues from occurring.