Reverse-cone megaphones for V-11 Sport?

[belfastguzzi]

That's what I guessed, but then the reverse cone musn't need to be very big? Todd E describes this design (see pic) as 'true reverse megaphone'. It seems like just a big pipe with a small part of a cone on the endcap. I can see it as a megaphone. Surely not much cone to deflect pressure back? But I don't know the science of pressure waves.

 

Due to 'computer problems' it'll take a while for me to recover photos and stuff. I have this pic on the web. It's not great.

 

Ah, here's another:

[GuzziMoto]

I have one of those from Todd on my Griso. Sweet pipe. Haven't taken it apart to see if it is indeed a "true" reverse cone design. It loks like it is. It does work well, though. Typically, "true" reverse cone megaphone designs can and do incorperate a muffler into the design with out comprimising the design. The way they do this is to have the reverse cone BEFORE the baffle tube/muffler.The cone flares out, then the reverse cone portion necks it back down a little but the body of the muffler stays the same size or even gets larger (to make room for glass packing). The baffle tube then mates up to th output of the "reverse" cone. This is probably one reason why Todds pipe has such a large baffle. The out put of the reverse cone is usually pretty large.The muffler takes the edge off the sound levels with out costing much (if any) power. There are plenty of non "true" reverse cone megaphone pipes out there like the Laverzzi's, I personally don't think it's a huge deal whether it is a "true" reverse cone design or not. But a well designed exhaust will work better then a poor designed exhaust every day of the week no matter what type of design.

[Skeeve]

No way to tell if that pipe is truly a reverse-cone meg w/o hacking it apart, but the external profile looks like an attempt to appear like a (minimally) reverse-cone meg.

 

The real deal has a hole no bigger than the header inlet at the back end of the reverse cone. Remember, the idea is to generate the power of a pure megaphone exhaust w/o letting the sound out quite as much...

 

That pic you show basically looks like a muffler that been manufactured to look like a reverse-cone meg [which, as I posted earlier, would be too loud to pass EPA noise certs.]

 

A reverse cone meg was the response to the early attempts to limit noise output at race tracks. If I'm not mistaken, one of the other names for it was a "Brooklands pipe," as they were among the earliest racetracks to have to deal w/ adverse public reaction to their events.

 

Not saying that Todd's pipe doesn't function well, just saying that the clear muffler innards visible takes it out of contention as a 'true reverse cone megaphone."

[gavo]

now this is a reverse cone megaphone but for the guzzi make mine lavizzari

[Mark909]

 

Wow, that thing actually manages to LOOK loud

[luhbo]

....

The real deal has a hole no bigger than the header inlet at the back end of the reverse cone. Remember, the idea is to generate the power of a pure megaphone exhaust w/o letting the sound out quite as much...

......

A reverse cone meg was the response to the early attempts to limit noise output at race tracks. If I'm not mistaken, one of the other names for it was a "Brooklands pipe," as they were among the earliest racetracks to have to deal w/ adverse public reaction to their events.

.......

Not saying that Todd's pipe doesn't function well, just saying that the clear muffler innards visible takes it out of contention as a 'true reverse cone megaphone."

 

I say it's only a fluid dynamics thing, nothing with "don't let out too much sound". The reverse cone should create some backpressure right when the inlet valve had closed. That's all. Opening cones suck - closing cones blow

 

I think you can see brooklands pipes typically on Velocette bikes, for instance here

 

 

Todds exhaust has a really convincing and brutal look, really great so far, but from a technical point of view this solution is suboptimal. I know, all Mistral, Titan and whatever racecans are built this way, nevertheless these holes all around greatly enlarge the flow resistance. That's the main reason that such aftermarket exhausts seldom give more punch than the OEM parts. They're just lighter and provide the sound the animal inside needs.

 

I've been searching a picture of the Laverda 1000 factory race exhaust. It was a reverse cone unit. Those who haven't heard one will die poor, believe me

 

Hubert

[pete roper]

 

Wow, that thing actually manages to LOOK loud

 

 

It is, BFG and I have the same pipes on our bikes and it is IMHO too loud by far. I do have a DB killer for it but the problem is the mapping is so absurdly rich that I'm reluctant to restrict the enine any more than it currently is. Once gain the old saw of us with the w5.9AM computer really NEED a good map modifier to get the best from the 8V engine. The 15M equipped bikes are more than adequately catered for <_ .>

 

Pete

[GuzziMoto]

No way to tell if that pipe is truly a reverse-cone meg w/o hacking it apart, but the external profile looks like an attempt to appear like a (minimally) reverse-cone meg.

 

The real deal has a hole no bigger than the header inlet at the back end of the reverse cone. Remember, the idea is to generate the power of a pure megaphone exhaust w/o letting the sound out quite as much...

 

That pic you show basically looks like a muffler that been manufactured to look like a reverse-cone meg [which, as I posted earlier, would be too loud to pass EPA noise certs.]

 

A reverse cone meg was the response to the early attempts to limit noise output at race tracks. If I'm not mistaken, one of the other names for it was a "Brooklands pipe," as they were among the earliest racetracks to have to deal w/ adverse public reaction to their events.

 

Not saying that Todd's pipe doesn't function well, just saying that the clear muffler innards visible takes it out of contention as a 'true reverse cone megaphone."

 

I have to say that this is not correct. Many old R.C. Megaphone pipes have small outlet holes. But just about every modern version, especially those built for max power, have outlet holes BIGGER then the inlet hole. Some of the fasts twins racers I have seen including Pete Johnsons Manfred Hecht tuned Raceco Guzzi fall into this catagory. The purpose of the reverse cone has NOTHING to do with not "letting the sound out quite as much". People may have started playing with the idea for that reason, but that is not what they do or why they are used in todays day and age. It has to do with creating positive and negative pressure waves headed back towards the exhaust valve. In fact, reverse cone megs often seem louder then the same meg without a reverse cone on it. I have also owned a few true reverse cone megaphones that had a muffler on the outlet of the reverse cone. It is not uncommon. Some people are confused by the reverse cone shaped outlet to the pipe thinking that that is where the reverse cone would be located. This is not always correct. If you are going to try to quiet down a R.C.M. exhaust you would put the baffle AFTER the reverse cone. I also have heard from Todd that he did not just willy-nilly choose such a large baffle, but that dyno testing the prototypes told him that larger was better. I have a catalyst from another pipe stuck in mine to take the sound down a bit. I'm sure this cost a few ponies but I can always pop it out if I need them back.

[Tom M]

I don't know who makes these slip-ons but they seem popular with the Italian vintage Guzzi racers. I assume they'd make more power than the stock restrictive cans, and I think they'd look great on a V11, but would probably be too loud on the street without the DB killer inserts.

 

 

The pic is from here: http://www.animaguzzista.com/page_builder....acorta_2008.htm Maybe there's an Anima forum member here who could find out who makes those mufflers? Antonio?

 

A number of those race bikes like the one above have what appears to be a plastic or fiberglass Guzzi tank with fuel view strip like the old Ducati's had. Very cool!

[belfastguzzi]

now this is a reverse cone megaphone but for the guzzi make mine lavizzari

Yes, that's the look I would expect to fit with the description. That's why I have been curious as to what it really means.

[big J]

BFG,if you check out the exhausts section of the Unity Equipe catalogue

http://www.unityequipe.com/CatalogueMarch2008.pdf

 

you'll see true megaphone exhausts and those with reverse cones.

The reverse part was added on mostly single cyl racers,Manx Nortons,7R's,G50's and the like to give a wider "power band".The harmonic frequencies of the exhaust gases could be altered by changing the size,angle of cone and exit hole.

 

Phil Irving describes it well in "Tuning for speed"

[gavo]

In fact, reverse cone megs often seem louder then the same meg without a reverse cone on it. I have also owned a few true reverse cone megaphones that had a muffler on the outlet of the reverse cone. It is not uncommon. Some people are confused by the reverse cone shaped outlet to the pipe thinking that that is where the reverse cone would be located. This is not always correct. If you are going to try to quiet down a R.C.M. exhaust you would put the baffle AFTER the reverse cone.

 

 

I would have to disagree, in fact the RCM I posted the picture of is incredibly loud without the reverse cone on the end but with the cone fitted I can run on the street without internal baffles or packing and its not overly offensive. The only reverse cone on that exhaust is at the end so placing the baffle after it would beeeeeeee?

[GuzziMoto]

I would have to disagree, in fact the RCM I posted the picture of is incredibly loud without the reverse cone on the end but with the cone fitted I can run on the street without internal baffles or packing and its not overly offensive. The only reverse cone on that exhaust is at the end so placing the baffle after it would beeeeeeee?

That would be because your reverse cone has a fairly small exit hole. I have seen smaller, but many RCM exhausts have larger openings. But that is why I said "often" and not "always" or "most of the time". I am refering to RCM exhaust as a whole and not yours specifically. RCM exhausts made for max power tend to have a much larger exit and as a result are much louder.

As for the baffle bein before or after the reverse cone, the baffle would obviously be in the last 10" or so of the pipe where the diameter is fairly constant. The reverse cone (if it is indeed a true reverse cone setup) would be next, right before the baffle and not easily visable to the naked eye. That is why people have said that to find out if it is a "true" reverse cone meg or not you would have to cut it open or take it apart. Not everything in life is what it seems to be.

[gavo]

That would be because your reverse cone has a fairly small exit hole. I have seen smaller, but many RCM exhausts have larger openings. But that is why I said "often" and not "always" or "most of the time". I am refering to RCM exhaust as a whole and not yours specifically. RCM exhausts made for max power tend to have a much larger exit and as a result are much louder.

As for the baffle bein before or after the reverse cone, the baffle would obviously be in the last 10" or so of the pipe where the diameter is fairly constant. The reverse cone (if it is indeed a true reverse cone setup) would be next, right before the baffle and not easily visable to the naked eye. That is why people have said that to find out if it is a "true" reverse cone meg or not you would have to cut it open or take it apart. Not everything in life is what it seems to be.

 

The exit hole is exactly the same diameter as the inlet on this pipe and I 've have had it apart.

Can u post a diagram of your "true" reverse cone meg as the twenty or so pictures I've just looked at of race bike reverse cones all have an outlet the same or slightly larger than the inlet and I still see fail to see how u can fit a baffle after the reverse cone when said cone is at the end, why would u fit a RC inside the exhaust and the a baffle after to quieten it,its like putting the horse before the cart

[Skeeve]

Phil Irving describes it well in "Tuning for speed"

 

Aha! A connoisseur... Irving's TFS is OOP and quite a hot property: I'm amazed his descendants haven't woken up to the opportunity for a reprint, as right now they're losing sales to folks photocopying what copies they can find at libraries, etc.