I currently have full chambered dual exhaust on my '86. I love it. Unfortunately, I'm moving into quieter neighborhood and I don't want to be a jerk when I fire this thing up at 5:30am to go to work. I have a 2.5" catless front Y-pipe, stock main cat, and crossover piped rear Y-pipe available to me. How will Flowmasters (Corvette replacement-style) sound with this setup? I've had Dynomax Super Turbos, but they droned badly, yet were not throaty at all. Will the Flows be quiet enough for a neighborhood but with a little edge (the classic Flowmaster sound) when I get on it?

 

Flowmasters are never quiet especially at 5:30 in the morning.

 

My Flowmasters are never quiet. I dont care what time it is.

 

Bummer. I thought the three chambers might be quieter.

 

 

The C4's I have ridden in with Flowmasters are noisy at WOT and they do have lots of interior drone.

I have DynoMax Ultra-Flo's on my '87 autocross car and they are quiet at idle and in city driving. The exhaust system is Hedman headers into 2-1/2" pipe with an X-pipe where the main cat would be located and true dual exhaust into those mufflers. No interior drone at all (there is no carpeting in the car!) , but they have been measured at 100dB at a local road course (WOT in 3rd gear about 5300RPM).

The Walker p/n at Summit Racing is WLK-17218.

As far as the Flowmasters, I have heard that the 40 series will actually produce more backpressure than comparable performance mufflers.

 

I have Flowmasters on my 95, and absolutley no drone. I have never heard they produce more back pressure than comparable other aftermarkets. I would like to see that comparison. Not too loud until you stand on it. Has a great sound at idle, but I still have cats on. I like them a lot.

 

I was under the impression that the 3-chamber C4 specific Flowmasters were quieter and had less drone than the usual 40 series. My Super Turbos drone alot, yet the exhaust note has no trace of rumble, just smooth and low.

 

Consider putting additional converters in your front "Y"-pipe. Use these unless you have a modifed engine. If so, use metallic spun cats instead.

Note: There is a 2.25" version of the 53000 converter series but, just like mufflers, having larger inlet/outlets reduces restriction. Even more important is to know the addition of these converters will lower sound where you want/need it AND clean up your exhaust. Why pay MORE for new mufflers and not get the added benefit of an even cleaner, better-smelling car?

I should add that later L98's had this pre-cat/main-cat combo. Mine did. Magnaflow pre-cats and a main-cat with back-to-back resonators sounded great and would have been well into the sound level you're shooting for.

In case you think that's too many converters, ask how many converters are on a Pontiac G8...with an LS engine!

MORE CONVERTERS BUGS YOU? OK...

Adding glass-packs (aka resonators) anywhere you can find room would also work...and cost less than ANY OTHER MUFFLER SWAP. You could probably do glass-packs for $100 installed. $200 for converters.

Either option will lower your sound where you need it. If it doesn't, you're really looking for factory-quiet mufflers. Dynomax has a quiet-flow muffler line (Quiet-Flow III?) that's probably around $300-$400 installed.

I'm telling you...skip the oval muffler idea.

 

That is a correct impression. More chambers = more muffling. Not necessarily a lot more though.

 

I've read some of your post on drone-theory regarding oval mufflers. Interesting stuff. I've found in my travels that a straight-through muffler design also tends to drone less. Like you've suggested, chambered and typical reverse-flow "turbo" design mufflers tend to stack up the drumming resonant effect at the rear of the car.

In my past job at a Corvette resto shop I got to inspect ALOT of vintage Vettes. I'm convinced part of the C4 drone comes from the dual to single back to dual exhaust design. C2s as well as later C3s (when equipped with no cats and true duals) didn't drone despite have a large glass rear enclosure like a C4. A later C3 with factory routed exhaust and single cat would begin to drone like a C4.

 

Mine are 40 series.

 

I understand what you're saying. But, have you heard that setup without a center converter? When I pulled mine, the sound was somewhat louder -- but the drone when away! I don't discount the possibility that larger-body converters "pile-up" sound too. It's not as bad as a chambered muffler though.

On my current setup, I've tried a chambered belly muffler, converter, and straight-pipe. The later is the only option that didn't drone. Still, it's a Y-pipe setup that merges into a single collector for the Side Effects Side exhaust system. In a real sense, it's the same as Y-single-Y combo. If you've heard this (catless-straight-thru) setup in a car with rear exhaust, I'd be interested in the result.

For curiosity...

 

If the mufflers bother your neighbors tell them to buy you a set of Corsas. Everybody wins.

 

I have gone without a cat. My first set up was stock back to a crossover rear Y and Dynomax Super Turbos. Drone, but not deafening. No rumble. Second, replaced front Y with 2.5" catless front Y and test pipe. No cats. Louder, deafening drone and boom yet still no rumble. Third, full dual chambered exhaust. Loud, plenty of rumble, but little to no drone.

To me, Super Turbos must be drone inducing in C4 Vette exhaust configuations. On my 350 Nova, they're quiet and drone free. I know another key to the C4s drone problem is how quickly the 700R4 shifts into overdrive. The torquey TPI easily drags the car around chugging at 1200-1300 rpm but at the cost of deep low resonance.