DIY muffler... megaphones work for bikes, why not cars?

Any particular reason that megaphones aren't used commonly in the exhaust of cars, but are very common on motorcycles, even multi-cylinder bikes? I want to develop an exhaust for the mini and the miata, replacing the resonator/midpipe with a collossal (4.5-5" outer dia, 2-2.25" inner dia, 3.5-4' long) glasspack with stainless steel/ceramic packing, and I've been thinking about integrating a mild megaphone into the inlet side (think getting a motorcycle dual-cone megaphone and using that as the front endcap, rather than just building off of a Supertrapp). Would this do anything useful, assuming it was designed to match the engine and the header?

Loud exhaust systems are less tiresome on bikes than they are on cars.

At least to the owner.

All I can say it try it and let us know. I think you are probibly going to end up with somthing raspy and drones at speed. Fun at first but wares on you after a while. Just for S&G's I put a straint through muffler on my 924s and although it was fun to set off car alarms for a while it got old really fast.

actual motorcycle mufflers sound like E36 M3 on a car. someone I know ran one on a 1.8 miata for a short while.

megaphones, well, assuming you are talking ones that are simply just an open pipe that gets larger in diameter, with no baffling, its probably going to be loud.

Plymouth Barracuda AAR had megaphone style side exhaust tips. I cant say I have ever heard them in person, but they look cool IMO

I have always thought of using one for a decibel competition at some misc car show.

I have a universal one laying around that I made, starts 2" and ends at 4" I thought about welded it on a flange with a 90 to exit out below the passenger side door. Have that bolted on to my header and that alone.

oh, its on a ported rotary as well. Probably have to drive with earplugs with ear plugs within those ear plugs

This was just putting a megaphone at the beginning of a gigantic glasspack muffler and using that as the midpipe, then putting another muffler in the stock location, no idea what though

It's been done, but I wouldn't call it a street car:

I used to run a Supertrapp without the plates on tracks I could get away with the extra volume. That's kind of like a megaphone, but with some noise absorption.

If you want cheap, go to the local farm store & buy a tractor muffler. Cheaper than a glass pack, and probably cheaper than you could build anything.

I used one on an old ABA GTI and the sound was reasonable.

Woody wrote: Loud exhaust systems are less tiresome on bikes than they are on cars. At least to the owner.

I'm really hoping you're wrong. We'll find out when I strap this onto the L24 in my datsun.

Just run all glass packed mufflers. You don't need any noise violations anyway. A good manifold with glass packs should sound pretty good.

Or go with magazine advertiser Burns Stainless! That's what I would use.

http://www.burnsstainless.com/

VW guys have been running "stingers" forever.

My boss used to have a sweet 70's Porsche GTS replica with a 3.6 and would run the megaphones for track days. Obnoxious is an understatement

jstein77 wrote: I used to run a Supertrapp without the plates on tracks I could get away with the extra volume. That's kind of like a megaphone, but with some noise absorption.

While those are megaphone-shaped, the insides are a cylindrical, perforated core like a conventional motorcycle can.

The discs do take the edge off the sharp note of the power pulses, but when you use enough discs that you're not totally strangling the engine they get really loud.

I used a pair on an R100RS BMW for years - and owe no small measure of my hearing loss to them.

I had a Kawisaki 650 muffler on the 71 Super Beetle I had in high school. It sounded like a Harley at idle and a rice rocket at "high" RPMs. I liked it then. Not something I'd want in a DD now. I only got pulled over for it once. The set screw backed out and it spit the baffle. So it was extra load and spit flames when I down shifted. Ok, it was fun...

In reply to failboat: I've driven an aar cuda before, it was loud, but nowhere near as loud as the 65 gt350 racer I drove.......that car made babies cry.

I've seen supertrap(or wtf ever they're called) on minis before....the tunable ones. Didn't sound good, but then again n/a minis don't sound good anyways

Ok, there seems to be a significant disconnect between my idea and how Im able to express it... so far nobody has even come remotely close to what's in my head. Let me draw something up: (pardon the horrible handwriting, but the pretty picture should give you the basic idea)

This piece would go in place of the midpipe (aka it bolts to the header/cat, then an axle-back exhaust system would bolt to it) and would serve the same function as replacing a midpipe with a glasspack, but with potential tuning/power benefits as well. The reverse-cone+megaphone section would be purely for power benefits, assuming what holds true for single-cylinder engines would also hold somewhat true for multi-cylinder engines running through a single exhaust. The tuning for it would follow the same ideas presented in this thread (please pardon the linking to another forum).

What I'm curious about is whether THIS idea about being able to use a reverse-cone megaphone IN-LINE on an exhaust system on a car would work at all, or whether the multiple pressure waves from the multiple cylinders would make any sort of single-cylinder tuning theories irrelevant/not work. I just figured putting it immediately upstream of/integral to the structure of a gigantic glasspack might make packaging easier

Loud exhausts suck, and they are bad for everyone involved. Out of respect for our hobby, we should all do our part to make our race and street cars as reasonably quiet as we can, and we should certainly not go out of our way to make them unnecessarily loud, and loud doesn't equal fast. While it may seem really cool and ginchy in a childish kinda way, it ruins things for everybody. When you piss off the squares with excessive and unnecessarily loud exhaust, bad things happen in a very real way, such as legislation that is harmful to the hobby, and worst of all, it gets zoning laws changed and race tracks closed. We just had this happen here in Orlando, with the closing of the CFRC drag strip.

dean1484 wrote: Just for S&G's I put a straint through muffler on my 924s and although it was fun to set off car alarms for a while it got old really fast.

that's funny. I have a supersprint cat back on my 318ti.. even though it is very quiet (still louder than stock) it also sets of car alarms

Noise level wise, the megaphone portion of my idea excluded, how is this any different to replacing an OEM-installed resonator with a glasspack or any other muffler of similar design, and retaining the mufflers downstream of that? I really don't want to be that guy with the annoyingly loud exhaust, but I do want to broaden my understanding of the tuning capabilities of various exhaust designs. I repeat: I don't want to be that guy with the annoyingly loud exhaust, but I do want to broaden my understanding of exhaust tuning.

If it offends the collective sensibilities that what I'm proposing might increase the noise level, then can we just analyze the exhaust pulse differences seen by an exhaust expansion chamber when comparing a single cylinder engine to a multi-cylinder engine?

I hate to be that guy who overuses the bold/italic coding to put extra emphasis on aspects of a post, but I feel like some parts are being ignored (either unintentionally or otherwise) and thus need the emphasis.

Without a real understanding of the physics of sound waves, you're not going to be able to come to any understanding of exhaust tuning at all.

There's just SO much more to all of this than sticking sound limiting devices up or down stream in an exhaust system, you know?

Every muffler, megaphone, baffle, resonator or otherwise is different from every other on the market and reacts differently in concert with other devices. Honestly, the exhaust system can be much better understood if you think of it as an instrument, like a trombone if you will. Pipes slid into others, cross pipes and restrictions or mutes, side pipes and end caps, sound, droning, back pressure and all of the rest.

You won't broaden any understanding of anything by shoving motorcycle megaphones onto anything, no matter how many times you do it or declare in bold type that your about to do it.

A college level physics class is what you really need.

Sorry,

T

My brother has a supetrapp on his MKI jetta coupe. It sounds fine without being overbearing. It is "tuneable" somewhat.

Sounds like you want to build a resonator/front muffler out of a megaphone welded to a glass pack. Your theory is that the megaphone going into the glasspack will "tune" the exhaust more than just the glasspack alone (correct?)

I don't see how that little difference will give any noticeable results. I think a glasspack flows better than the typical front muffler anyway, so no need for a megaphone.

Go for it. Build it, test it and report back. Worst case you know what doesn't work.