Exhaust cones

[Sidecar]

Does anyone use the exhaust cones to increase back pressure, in their pipes??? Everyone I know never uses these things. Just bolt on the drag pipes and fiddle with the carb jets. Do they work or are they junk ??
Should they be used in aftermarket duel exhaust systems that use free flowing mufflers ??

[Cotten]

By "exhaust cones", do you mean megaphones?
(I hope like hell that "most" of us have figured out that drag pipes are junk!)
"Back-pressure" isn't a good term. What you really get from baffles is anti-reversion.
What kind of motor, carb, cam, and riding habits are you concerned with?

[Sidecar]

Hi Cotten !

These things are inserts that are installed at the head pipe and look like cones. [ It`s kinda hard to describe. It would look/work like a capital letter Y ] I guess that it shoots the exhaust into the center of the pipe and creates a vortex around the cone to drag even more exhaust out ??? Maybe it works like a jet pump that you use on a well to pump water out at a higher pressure and faster flow ???
When I think of megaphones, I think of mufflers on the end of the exhaust pipe. [ I used to run megaphone Hooker Headers on Thumpers, in the woods, back when I was younger ]
Would this be a scavenger system to suck more exhaust out of the head at a faster rate ??

I`ve got all these exhaust thoughts floating around in my head and it`s hard to put it into words.
Maybe the term I should be using is anti-reversion exhaust cones installed at the exhaust port ??
Can you describe anti-reversion pertaining to with baffles and without baffles ???
Sorry for ramblng on !!

[dirtpandan58]

I think you're talking about power cones or exhaust "tork" valves . I think you can only us them on evos and TCs.

[Cotten]

Another name for them is "reversion dams", and the laws of physics don't know whether your motor is an evo or twinkie or not!

The best I can understand it, exhaust isn't a constant flow like water out a hose, its a pulse that likes to back up. This backwards domino effect (reversion) is reduced by any obstruction (like a baffle), but for high Rpm performance, you don't want to snot it up too tight. The dams at the header supposedly have the best effect early in the chain of pulses. But the exact spot is determined by the valve size, ports, desired optimum rpm, etc.
Ideally, the distance from the exhaust valve should be determined from flowbench and dyno testing, but who can afford that?
True Low end performance is a different set of variables altogether, but the dams don't hurt.
I'm glad you weren't thinking megaphones. They may work, but they sound like hell.

[dirtpandan58]

I know the laws of physics don't know what motor you're running!!!
What I meant was, I've only seen them manufactured for an Evo or Twinkie.
If you've seen them,or know where I can buy some for a pan, please let me know. I would like to try them on my panhead.

[Cotten]

Post by Cotten on Jan 1, 2003, 6:01am

The exhaust spigot on a pan is itself a bit of a dam!
Toss your catalogs back by the toilet and get out the hacksaw and torch: Exhaustpipe reducers can be bought at any auto supply, and a whole lot cheaper than bubblepac one-size-fits-none trinkets..

[dirtpandan58]

Thanks Cotton,
Never thought about that.
Any idea on what size to reduce to, and what length they should be?
You're talking about just welding them inside the pipes correct?
Thanks,
Dirt

[Cotten]

As I posted before, it would take at least a flowbench to be certain of an optimum length and placement, but homespun trial and error could probably take you most of the way.
Pans don't breath in a manner that would display a lot of benefit, but I made a set once by takeing worthless old 2" dragpipes and inserting about 6" of regular system inside at the header. (I still used a turbulence-inducing "baffle" close to the exits made of rolled perforated sheet with triangular cutouts bent up into the flow in a vaned manner.)
I don't know how much good it did, but it sounded tits, looked rad, and I was proud that I didn't spend any money.

[Sidecar]

Hey, whatsa Twinkie ???

Cotten, I started asking around and am getting the same response as you had written. The best benefit being in the low end performance range.
I don`t plan on running drag pipes, but I am going to run dual exhaust with fish tail mufflers.
As I see it now, the cost for the anti-reversion cones to drop in the head pipe will keep me from using them.
If the Dyno is reading true, I`ll be around 50 peak hp with the Pan. [ Without cones ] That`s good enough for me with a rigid frame and drum brakes on these lousy PA roads. I gotta get to work on Monday mornings so drag racing and high speed riding ain`t for me !!!!! Yeah, the old fart stuff is starting to catch up with me. Smile

Thanx guys !

[dirtpandan58]

Twin Cam = Twinkie

[Cotten]

Sidecar!
If you are talking straight pipes to a fishtail, they are even worse to tune than drags!
Any kind of expansion chamber helps.

[Sidecar]

Cotten,

That must be why they had to run the dyno test 31 times to tune the factory 2 into 1 pipes that run into a straight thru fishtail !!!! They ended up putting a short length of baffle in the pipe.
I read on the S&S site that fishtails are a pain to tune. It must have something to do with the tail itself ???
I`m planning on using the 3 piece, 1 3/4 inch dual exhaust pipes and 28 inch long, 2 1/2 inch dia. steel baffled fishtails from Paughco. I`m using the 3 piece so I can keep the front pipe thru the frame so I can still make right turns.
Do you think that I should forget the fishtails and go with the cigar style [ or something else] ??
My pipes are not set in stone. I`m open to suggestions !!! Lemme know what you all think....

Thanx for the help
Randy

[Cotten]

Geez, exhausts are a personal thing. I can't suggest anything but stock, but I don't practice what I preach either! ( I'm into "ugly".)
My personal favorites were the old Dixie Superior exhausts, after I turned the stick welder on "High" and burnt out the baffles..... Nah, you don't want to listen to me. I'm a dinosaur.

[Sidecar]

No problem Cotten.

I think that I`ll take a ride over to the Dyno Dude and pick his brain a little and see what he says. I may put the pipes on the back burner for a couple of months.
What I really need to do is get some saddlebags on my scoot. I hate the thought of putting those big chrome brackets on the sides of the fender. I like the bags, not the mounts.
Thanx for your help
And Thanx to DPDan for letting me know what a Twinkie is !!!!
Randy