Alright, I just read a similar thread in the external engine section forum, but these guys were talking about exhausts on Trans Ams and Camaros.

I just recently switched over my exhaust from a MagnaFlow to a Flowmaster 40 series. I know, I know, why would I do that. I know that the MagnaFlows flow better. But the MagnaFlows were just way to quiet for me. Anyways, Both systems were and are dumped right after the muffler.

When driving, especially at highway speeds, when I let off the gas to coast, the Flowmaster pops, quite a few times when slowing down. The Magnaflow did this too, but not to the extent of the flowmaster and it wasn't as noticable because it wasn't as loud. I love the sound of the Flow, although I have noticed a little decreased power. But what is causing the popping sounds. On the other forum they were discussing having too much backpressure and then not enough, blah, blah, blah. I mean, it doesn't really bother me or anything, actually sounds pretty damn cool. Just am wondering what it is or whats causing it, and if its a plus or minus or just a way of life with changing exhaust. By the way, this is just a muffler, stock exhaust manifold and all other stock cats, piping, etc....

Just curious is all.

Is there any mufflers out there that sound as good as flowmaster but has better flow? I really wanted a corsa but didn't feel like spending that kind of green, plus I like the way the no exhaust(dumped) style looks. If they just sold the corsa muffler by itself, I'd get one.

 

I think your going to get that from any chambered muffler. I actually like my one chamber better then the 2 chamber on my truck. it flows better and as long as you leave on the cats it just a has a real mean low tone, also doesn't get annoying to me on the highway. but that was then and this is now. I think it's jsut soemthing you will have to live with unless you put a much more restrictive exhaust on. I also wanted the corsa but only the muffler, their making to much money off of the entire setup to jsut sell the mufflers. IMO

 

with my cutout open mine pops bigtime when deccelerating....not at all with it closed (Magnaflow muffler)

 

Has nothing to do with the muffler. Your running rich. The poping is unburnt fuel being caught on fire as it exits your exaust. Get a wideband and youll find out that your running rich.

 

My Yukon started doing this immediately after my magnaflow and volant install. So what we're saying here is that adding these bolt ons makes you run rich and requires a re-tune?

Hadnt heard that before. Have heard cars with glasspacks and other stright though mufflers popping on deceleration throughout my life and considered it normal with an open pipe. I have NEVER heard this type of popping (kind of resembles blow off between shifts on a turbo WRC car) come from a baffled exhaust like the flows.

So is the belief here that all people with a magnaflow, an intake and NO tune should be experiencing this problem?

Another quick Q - What grade fuel are you running? And would that have an affect on running rich if you do onot have a tune (for instance running 91 when you can get by with 87)

 

I have a Nelsons Tune for 93 Octane and I always run 93 Octane in it. I haven't installed a cooler temp thermostat yet, been trying to hold out for a 180 degree unit. Not that this might have anything to do with it. Like I said, doesn't really bother me, but if I am running rich, maybe I need to get it Dyno Tuned. I am planning on doing that anyways, just trying to hold out till I get all the work completed to it.