Hi everyone it's my first post! I have a G35 5AT and I got a local shop to replace from the y-pipe back with a 2 1/2" pipe into a Flowmaster Series 40 1-in 2-out muffler. Now the car sounds great, except between 1700-2300rpm (about cruising speed) the sound in the cabin is deafening.

What can/should I do? Should I put the resonator back? An aftermarket resonator? Or maybe just replace the muffler? From what I understand about acoustics I must be hitting the resonant frequency of the exhaust system at that rpm range.

Any recommendations on just mufflers, if that's what I should do? I like the deep sound of the Flowmasters, as opposed to Injen, Nismo, etc but I don't want to set anyone's alarm off!

Thanks in advance! I look forward to becoming an active member on the forum as I get more money for mods. Log live www.my350z.com!

 

Add a resonator.

 

flowmasters on a Z? i usually associate those with mustangs, camaros, american muscle... dont get me wrong i love the sound of those cars, but im curious as to how it sounds on on the Z.

 

It actually sounds very good (to me at least), just waaay too loud at 1700-2300rpm.

I had a Grand Prix GTP 3.8L SC with some bolt-ons for awhile that I had two Series 40 Flowmasters on and I grew to love the deep, throaty sound. I get a nice burble when I downshift as well. I love the looks of some of the other exhaust systems, especially the NISMO, but I just don't care for the tinny raspiness after 2500rpm or so.

Plus I know the guys real well at this shop so they did all the work including the muffler for $100.

 

1700-2300 is your cruising RPM? Where on the street? lol Throw it in Manumatic mode and never shift out of 4th

 

I have a Flowmaster 80 on my Z everything else stock and it is THE BEST SOUND!
The only thing is it kinda drones is when Im doing like 45-55 in 6th gear.

 

Okay the resonator is going back on tomorrow! Thanks everyone for your help.

 

yeah, you definitely will love it after the resonator is added back in. When I did this, I only made it home from the muffler shop, then turned around and went back to get the resonator put back in. If my muffler shop y-pipe wasnt a peice of crap, I would have never gone borla. The flowmaster sounds like an audi ALMS racecar.

 

I believe that someone on this board also dynoed this mod at 5WHP. I can't really tell any difference but I LOVE the sound.

 

Put mine on with a set of test pipes. Drove home and went staight back to put the cats back on. Now all I have is the 80 series. I think it sounds great. And no worries come inspection time.

 

Anyone have pictures of their custom flowmaster exhausts?

 

It appears you guys think that garygraphite is driving a Z when he is driving a G35. That would answer the questions about cruising RPM.

EnthuZiast, Why are you driving 45-55 mph in sixth gear? Gas mileage just isn't that important. For any power at all, you would have to downshift to 4th.

 

garygraphite,

Flowmasters are known for that resonance, and the 40 series are the worst. Of course, they flow the best, too.

1) Resonator, which is something almost all systems need. Plus, it will take the rasp out of the exhaust note (although some people like that).
2) The length and diameter of the tail pipes is critical to reducing interior noise. Increasing the first and reducing the second will help. On a couple of my previous cars, I experimented with this until I managed an acceptable balance between appearance and sound level. Unfortunately, Flowmasters sound best when they have NO tailpipe.

The best-sounding car I've owned was an Alfa GTV6 with headers and a Flowmaster exhaust. It would curdle your blood.

BTW, nothing personal, but your comment about paying "only" $100 for your exhaust system, reminded me of the son of a friend of mine, who raved about the pizza he bought @ 7-11, because it only cost $2.95 AND(!) was 12" across. :-)

 

Lateapex I do not buy pizza at 7-11! Come on I bought a G35 for crying out loud!

Just as a note I think the exhaust gave me a little extra HP. SOTP registers a difference, and now I get a little bit of spin from first to second that I did not before. I would not be surprised if the G35 exhaust is more restrictive since it seemed like the muffler was the size of a 50 gallon drum. I don't have a point of reference though since I haven't seen under a Z in person. They had a muffler at the shop from an M3 and that thing was HUGE! Thing must have weighed 40 pounds on its own.