Internal exhaust mod - Page 2 - 986 Forum - The Community for Porsche Boxster & Cayman Owners

tommy583 · 06-25-2018, 04:00 PM

I know 90% of the drone on my Circuit works exhaust is from leaks. The 2 bolt clamps up near the cats will leak if I don't tighten the hell out of them. The ones closer to the muffler leak even worse. I even bought new clamps and they still leak. I'm positive that the muffler pipe diameter is a touch less than the stock muffler due to thinner metal. No matter how far I shove the C pipe in or tighten the clamp it still leaks. So i'm just going to mod my stock muffler, buy new 2 bolt clamps and be done with it.

particlewave · 06-27-2018, 12:34 PM

I know you say you're done with it, but have you tried something like packing fiberglass cloth in the gap before tightening?

tommy583 · 06-27-2018, 01:58 PM

Well I thought of placing something in there to take up the extra space....but I actually just cut into my stock muffler at work. Right now i'm at a 1/2 inch hole all the way thru the pipe. I have to run to the store and get a bigger drill bit. I'm thinking going with 2 one inch holes all the way thru the pipe.

tommy583 · 06-27-2018, 03:14 PM

Progress so far.

Both of the holes on top are 3/4 of an inch. The holes on the bottom of the pipes are 1/2 inch on one and a little more on the other maybe 5/8. I had to make the bottom holes smaller so to not drill thru the bottom of the muffler with this bit set up.

particlewave · 06-29-2018, 12:21 PM

Looking forward to your results, Tommy!

tommy583 · 06-29-2018, 12:36 PM

I got it welded back up last night. It doesn't look pretty, but it should work ok. I think i'm going to use a chisel to make the bottom holes into one larger one before I put it back on the car. Kinda like Particlewave style

tommy583 · 07-12-2018, 12:01 PM

OK I put the modded stock muffler back on the car. I still have a wicked exhaust leak at one of the 2 bolt clamps near the cat. So how does it sound? I think it sounds like a proper sports car now. The difference from stock inside the car is subtle. It is a little louder but you can still hear the intake. It has a much raspier tone then the twin can Circuit Works muffler. When at WOT you can really hear it once it hits the 5,000 RPM Variocam crossover point.

Outside of the car is another story, under a bridge or in a tunnel it screams. I had my wife rev it up in the driveway, it sounds awesome from outside the car. It has a throaty almost metallic sound to it. It sounds a lot like the FVD sound version muffler IMHO.

Even with the exhaust leak there is no drone in the car. With less of a leak the twin can muffler was headache inducing. I've ordered 2 new OEM Porsche clamps from our sponsor. When they come in I will take it all back apart, make the holes a little bigger and button it up.

If you don't mind the weight of the stock muffler and don't want to spend $1500 for the FVD muffler, then this is the way to go. I honestly think this sounds much better than the twin can mufflers. The tone of the twin can mufflers is a little deeper than i prefer and it's always kinda loud. The modded muffler is pretty tame during normal driving and under 5,000 RPM, but when you get on the throttle it sings. It even has a little burble on over run sometimes. I'll try to post a sound clip when I get the new clamps.

All this was done on a 2000 S muffler. It has two 0.75" holes in each top of the pipe, two 0.50" holes on the bottom. I used a chisel to open the pipe between the holes on the top and bottom of each pipe. It also has a Crios mod with 0.75" holes I did before.

robdelorenzo · 07-12-2018, 12:11 PM

Question (maybe a dumb one at that) does the Crios mod or one like you are doing affect passing CA smog?

particlewave · 07-12-2018, 12:30 PM

Quote:

Originally Posted by robdelorenzo

Question (maybe a dumb one at that) does the Crios mod or one like you are doing affect passing CA smog?

The muffler only affects sound, not emissions, so I don't see why it would.

tommy583 · 07-12-2018, 12:31 PM

No I don't see how it could. It doesn't affect or alter any of the emissions equipment on the car. Plus the car will look stock, just a few hidden holes in the muffler

robdelorenzo · 07-12-2018, 12:36 PM

cool...thanks....time to bust out the punch then!

particlewave · 07-12-2018, 12:43 PM

Quote:

Originally Posted by tommy583

OK I put the modded stock muffler back on the car. I still have a wicked exhaust leak at one of the 2 bolt clamps near the cat. So how does it sound? I think it sounds like a proper sports car now. The difference from stock inside the car is subtle. It is a little louder but you can still hear the intake. It has a much raspier tone then the twin can Circuit Works muffler. When at WOT you can really hear it once it hits the 5,000 RPM Variocam crossover point.

Outside of the car is another story, under a bridge or in a tunnel it screams. I had my wife rev it up in the driveway, it sounds awesome from outside the car. It has a throaty almost metallic sound to it. It sounds a lot like the FVD sound version

Nice, right?

I took the car on a 2 hour round trip yesterday. Cruising at around 3000rpm on the highway, the sound inside the cabin was just fine...a low rumble that was not at all bothersome.

As soon as you pass under a bridge or through a tunnel, especially at higher rpms, sound is intoxicating!

tommy583 · 07-12-2018, 01:46 PM

Yeah I agree. The little 2.5 sounds raspy...kinda like a mini GT3.

lkchris · 07-17-2018, 03:39 PM

Quote:

Originally Posted by Gjohn3707

Any drone with this?

Drone is caused by fitting a muffler that weighs significantly less than the OE muffler. Unlike most cars, the Boxster muffler is suspended by the same mounts as the motor and transmission, and they are simply "tuned" to the original weight.

I'd be fairly certain a little gutting of an OE muffler won't make much difference in terms of weight.

lkchris · 07-17-2018, 03:40 PM

Another pretty easy was to improve the sound of an early 2.7 or 3.2 is to fit a 2003-4 OE muffler.

Bolts right on, sounds way better, interchangeable tips.

particlewave · 07-20-2018, 06:11 PM

No, Kent.
Drone is caused by lack of a phase chamber or crossover pipe where opposing pressure waves can cancel each other out. Weight has nothing to do with it.
Also, the '03 sitting in my driveway right now sounds an awful lot like my stock 2.5 did before the muffler bypass.

There's no comparing stock to the internal bypass.

.

itsnotanova · 07-21-2018, 07:40 AM

Quote:

Originally Posted by lkchris

Drone is caused by fitting a muffler that weighs significantly less than the OE muffler. Unlike most cars, the Boxster muffler is suspended by the same mounts as the motor and transmission, and they are simply "tuned" to the original weight.

I'd be fairly certain a little gutting of an OE muffler won't make much difference in terms of weight.

My exhaust system is 17 lighter than stock and I have no drone. My muffler does have a crossover pipe though.

Finnegan · 06-21-2019, 01:08 PM

I spoke with a guy at a local muffler shop about this yesterday. I'm going to get it done next week. Can't wait!

particlewave · 06-22-2019, 01:33 AM

Quote:

Originally Posted by Finnegan

I spoke with a guy at a local muffler shop about this yesterday. I'm going to get it done next week. Can't wait!

I'm sure you'll love it

Just make sure you get at least three, if not four 1" holes on each side (or equivalent).

jmitro · 06-27-2019, 07:25 PM

so here's my cheap chinese muffler that drones like crazy at 2500-3000rpm but otherwise sounds pure bred and high strung.
how would one add a cross over pipe to reduce drone and would it even work?

add a small pipe connecting the two exhaust tips which is downstream from said muffler? or maybe a straight pipe connecting each muffler together?