Internal exhaust mod

[particlewave]

Double post...

[particlewave]

Just a reminder for anyone interested in doing this: do your math!

You want a total cross section of at least 3" sq., probably closer to 3.5" sq.
Use the formula for the area of a circle:

[SoloPierre]

Originally Posted by jmitro

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?

I have the same cheap eBay Chinese muffler with secondary cat delete test pipes on my 2002 Boxster. No drone what so ever. Sounds really nice. I guess I got lucky. I also have a Fabspeed spec muffler exhaust with resonators. It drones like you would not believe.

[maytag]

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.

I don't know why some people keep perpetuating this fallacy.
Drone has nothing to do with weight, nor how it's mounted. "...tuned to the original weight..." c'mon man.... how gullible are you, really?

Sent from my SM-G970U using Tapatalk

[Anker]

Drone is a resonance that is caused by standing waves in the exhaust pipes. The reason why a cross pipe works is that a peak from a wave in one side is cancelled out by a trough on the other side The less muffling there is in an exhaust the more prone it is to droning.

[particlewave]

Originally Posted by Anker

Drone is a resonance that is caused by standing waves in the exhaust pipes. The reason why a cross pipe works is that a peak from a wave in one side is cancelled out by a trough on the other side The less muffling there is in an exhaust the more prone it is to droning.

AKA: phase (or phasing).
However, you can have zero muffling and no drone with a properly tuned crossover.

I don’t know where people like lkchris get that nonsense. I see it repeated a lot...wacky.

[particlewave]

Originally Posted by jmitro

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?

If you’re going to add a crossover, I would think that upstream of the mufflers would be best.

[GlockandRoll]

Can't you add J-pipes to cancel the drone?

[subieworx]

https://www.ebay.com/itm/Boxster-986-Porsche-Catback-Exhaust-System-V2-Base-S-97-04-w-C-Pipes-3-5-Tips/123446177158?fits=Make%3APorsche&hash=item1cbdf72d86:g:YMkAAOSwPM9cpP-w

This one caught my eye earlier today. Thinking about trying it out.

[pilot4fn]

Originally Posted by subieworx

https://www.ebay.com/itm/Boxster-986-Porsche-Catback-Exhaust-System-V2-Base-S-97-04-w-C-Pipes-3-5-Tips/123446177158?fits=Make%3APorsche&hash=item1cbdf72d86:g:YMkAAOSwPM9cpP-w

This one caught my eye earlier today. Thinking about trying it out.

I'd be very interested to know does this have droning at 2000-3000rpm range.

[GlockandRoll]

Originally Posted by pilot4fn

I'd be very interested to know does this have droning at 2000-3000rpm range.

shouldn't be as bad, due to the X-pipe and the fact that both primary and secondary cats will be used.. if I'm looking at this correctly?

[pilot4fn]

Originally Posted by particlewave

If you’re going to add a crossover, I would think that upstream of the mufflers would be best.

This is what I would expect to be the cure for the drone - at least it worked real well on one of my ex cars with V8 and 6-71 blower (years back) to eliminate the drone all together.

Time to find smaller size decent mufflers that allow room for a crosspipe with crossover in a same space where the original muffler is.

[10/10ths]

.....There is validity to the weight of the muffler affecting the “Drone.”

If you read the engineering description of the build of the 986, the muffler and engine and transmission were all tuned together on a “shake table” as a unit. If you look at the way the entire power train is installed, they were engineered as a complete unit and were tuned as a complete unit. The designers wanted a center outlet exhaust for a link to the original 550 Spyder.

The engineers told them it was impossible with the room they had under the car. After a lot of work, they developed that one, huge, muffler and it worked.

If you take that one huge muffler off and replace it with a double can setup, it completely throws off the harmonics of the system and you get that nasty “Drone” on the highway.

That’s why the FVD Brombacher “Sound Version” and the “Crios Mod” OEM mufflers, and the Porsche factory accessory muffler with the vacuum actuated bypass valves are the only mufflers that give good sound and don’t produce the head splitting “Drone” on the highway.

Of those three options, today, a decade plus after the last 986 was built, the most elegant solution is the FVD muffler. Unfortunately, it’s freaking expensive.

BUT, it works. It’s WORTH the money.

But people buy these cars because they are cheaper than Toyota’s today and everyone wants a cheap, badass Porsche sound.

Just buy the FVD muffler and be done with it.

Get busy driving, or get busy wrenching and cussing.

Good luck.

[tommy583]

I agree the FVD probably sounds the best, but it is very pricey. The mod Particlewave and I did will get you 90% of the FVD sound for almost free. I guess if you took it to a shop it would cost you at most $200.
My buddy sent his muffler to Fister to do the external mod. With shipping back and forth I think it was close to $1000. The internal mod sounds almost exactly the same as the Fister mod, but way cheaper and no extra pipes visible.

[Dave80GTSi]

Don't overlook the Dansk 'sausage' muffler. No drone, and considerably less expensive than the FVD. Plus it's considerably more compact and lighter.

I've had mine for a couple of years now, and I could not be more pleased (bought used, dent courtesy of the previous owner).

[B85]

I tried this. We will see ?

[tommy583]

That should sound great, it's basically the Fister mod.

[DarrenD]

I did a similar mod to the OP except I used a 1 5/8"holesaw to cut the holes in the top of the muffler and I drilled 2 x 5/8" holes straight through the internal pipes and then welded the top back up. The PO had done the Crios mod already. I can't imagine the exhaust sounding better than it does, it has exceeded my expectations. It's absolutely perfect. All it took was a bit of time, some argon and some filler wire(I'm a professional welder/machinist). I will say that welding the muffler is not easy, it's double walled and each wall is super thin.

[GD Boxster]

Originally Posted by B85

I tried this. We will see ?

How does it sound? Happy with it? Sound clip or vid?
Cheers