someone972

iTrader: (2)

So I've got a Magnaflow catback with the turbo style muffler. Pain in the butt to seal the connections between the pipes but is a reasonably quiet system for keeping the neighbors happy and still sounds nice. However, sometimes a bit too quiet, so I have an electric cutout under the back seat hooked up to a custom controller activated by the fog light switch. All is good below half throttle, makes a nice deep rumble and good for a bit of fun. If I kick it down or actually put a lot of throttle in it it gets a nasty rasp type sound though, which I'm not a huge fan of. Makes it so I'd rather close the cutout and stick with the Magnaflow unless I'm cruising slowly. So I'm looking for some ideas that might make it so I can bear to use the cutout a bit more.

Right now the setup is a stock 350 going into Dyno Don 1 3/4" headers, to Dyno Don 2.5" to 3" Y pipe. From there goes to a single magnaflow 3" cat, then to the cutout, and finally to the muffler. I plan to go to a 383 with a more aggressive cam in the future, I'm not sure how this will impact the sound at higher RPM. I would guess it would just make the rasp worse?

I was thinking perhaps I could install a resonator between the cat and the cutout. There should be space enough for it, at least a smaller one. Would this help with the rasp from the cutout? How much would it change the sound of the Magnaflow? Any other ideas?

Abubaca

iTrader: (3)

I have similar setup. Had a zz4 cammed L98 350, now a 383 with slightly bigger than Hotcam set up. Both went through the same SLP 1.75 headers (similar to the DD headers for sound sake), 3" Y into magnaflow cat....into DRH 3" cutout under the passenger back seat with a turndown...then into a hooker aerochamber.

Both engines sound like *** with the cutout open. ....only reason I even have it is because of the time required to remove. I just leave it closed. The idea behind the cutout is really for racing/performance, which I honestly think is kinda hokey anyway. Systems are so good nowadays. I wouldn't do it again.

Adding a restriction to aid in the sound of the device designed to reduce restrictions seams counter intuitive. The 383 with bigger cam will be a good bit louder. I bumped almost a full point of compression and 33 cubes and the sound was MUCH louder, although through the same exhaust, it sounded the same. Just louder.

someone972

iTrader: (2)

Figured as much for going to a bigger engine. Btw, the type of resonator I'm talking about would be the straight through design with the perforations, so I don't imagine it would be very restrictive. However I also don't know if it would make any difference to the sound. Maybe I'll have to get creative with the muffler to get both a nice "quiet" sound and a nice "loud" sound...

someone972

iTrader: (2)

Has anyone been able to fit a resonator between the cat and the rear seat on a 3" single pipe? I haven't looked under the car to check yet, but if someone's already done it then I'd like to see some pics. I guess the only real way to see if it would make any difference would be to try it.

Biledriver

Do you have any pipe or turn down after the cut out. Whenever I do one for a customer I always make a turn down pipe and make it a little long if possible. Sometimes they sound good, usually if they're toward the back of the car. Usually just sound like a huge exhaust leak though.

someone972

iTrader: (2)

I do have a short turn-down. There's potentially a little bit of room to make it longer, but I don't think it would help much. Seems like there's so many things that can cause rasp, from the way the two pipes merge at the Y to just the engine design. Course with the space we have under these cars for exhaust there's not much to do besides try to mitigate it. I wonder if cleaning up the cutout split would help any, it's an awefully rough cut. I think the problem is further up though.

midias

I put this dynomax bullet resonator in my friends flowmaster exhaust after the cat area.

someone972

iTrader: (2)

That's getting close to where the cutout starts, but looks like it could work. Seems like the idea is sound at least. Thanks for the pic.

midias

Any little bit helps also the length of the pipe after the resonator helps a lot. Dynomax has a wide variety of resonators. Here are their shortest two a with a 3" inlet and outlet.

http://www.dynomax.com/mufflers/race...let-round.html

http://www.dynomax.com/mufflers/race...round-596.html

This is what I am running same with my friend in that picture.

https://www.summitracing.com/parts/wlk-24222

someone972

iTrader: (2)

Did you ever run it with just the Flowmasters without the Dynomax? If so, how did the sound change after installing the Dynomax in there? It looks like it's classified as a "muffler" but there's so much overlap between muffler and resonator nowadays. I don't imagine it would quiet it down all too much being a straight through.

midias

It took a lot of rasp out of the flowmaster and took out a lot of drone as well. He is actually considering keeping the flowmaster muffler now. For my magnaflow it really just made it quieter while cruising.

The resonator is a perforated straight through device. The amount of difference they make seem directly related to the length of pipe after them

someone972

iTrader: (2)

Unfortunately there wouldn't be too much pipe left after it, but I imagine it would at least bring the rasp down a bit. I may try adding that in and see if it makes any difference. Since the Magnaflow already cuts off most of the upper frequencies I could see it mostly maintaining it's current tone.

someone972

iTrader: (2)

Another quick thought I had was about the cutout sizing. I got a 3" cutout and turndown for my 3" magnaflow reverse-y-pipe (or whatever you call those things). It turns out it widens up to a 3.5" exit. Would there be any change in sound if I had gone with a 3.5" cutout and turndown to match the final exit pipe size? The 3" cutout had slot provisions to fit a 3.5", but it is overlapping a bit more than a 3.5" would I assume.

someone972

iTrader: (2)

I also wonder if the way the y-pipe is setup with the single cat config is contributing. There's a significantly longer secondary pipe on the driver's side header before the merge compared to the passenger side, maybe the pulses are lining up weird and causing additional rasp? Maybe going to the dual cat system would mellow it out, since it seems like the secondary pipe length is much closer.

Biledriver

You could look and see if you could cut the turn down short and weld on a resonated tip to it.

someone972

iTrader: (2)

Don't think there's enough room between where the cutout ends and turndown starts for a resonated tip, but that's a good idea. I went out and measured today and I should just barely have enough room for the Dynomax, although I'll be getting right up to the bend and I'll have to cut into it. As a plus though, I'd be cutting out the weird section of pipe where it necks down for no apparent reason.

someone972

iTrader: (2)

I ended up going with one of the mini bullets and one of the 12" race bullets from Dynomax. I figure I can try the mini bullet first, and if that doesn't work then step up to the larger one. I also got a fancy microphone so I can record before and after if I don't get lazy, which I'm sure will come in handy for other things as well. I'll shelve the Y-pipe idea until I get the other engine in there; I'm not completely happy with how mine turned out (it hangs down a bit too much near the wheel, different tolerances probably).

Ron U.S.M.C.

I eliminated the vibration from my 3in Flowmaster American Thunder System using two extra solid hangers including packing fire proof material between the cat and its shield.
It got rid of what I would call "Rasp" that I was getting at WOT.

someone972

iTrader: (2)

I'll have to keep an eye out for things like that. Hopefully when the microphone comes in I can get some good sound bites of what my particular "rasp" sounds like. There's a lot of sounds which people classify under "rasp" I've learned.

someone972

iTrader: (2)

I captured some of the rasp from inside the car today while testing my microphone. It should be pretty clear what I'm talking about from listening to the clip (attached). Probably sometime next weekend I'll try the mini bullet out and see what it does.