Torque/Anti-reversion cones

[WetDuc]

Nothing came up on the forum search and this seems kind of interesting to me.
The guys riding Harleys have a ton of threads about it.
They slip on at your header pipes and narrow the radius in a small section to increase the backpressure.  Maybe would need some pipe fitment on a duc?  Won't work with the desmo?http://www.lachoppers.com/catalog/display/1178/index.html
http://www.patentstorm.us/patents/5165231/description.html

[battlecry]

The patent application is interesting in that they are indicating a one way valve on the exhaust would be beneficial.

The reverse flow they claim to eliminate seems to me to be the negative portion of a sound wave.  Can't see that happening.  It is as if you could develop a diode or a rectifier for a sound wave.

If their bikes run better with more backpressure, perhaps they needed tuning to begin with?

My two cents...

[ID_DUC_MON]

I ran them on the Sportster tuner bike I built many years ago. They come about due to the trend of HD guys using really short open pipes and thus having lack of back pressure. For performance, they do not as good of a job as two-into-one pipes do but with some jetting you can get acceptable values and safe scavenging for the valves. Essentially they work for those wanting to have the chopped custom exhaust and are willing to sacrifice a bit of the performance.

[Bill in OKC]

There have been anti reversion headers for cars for a long time - 25+ years.  Maybe it is something that can be measured on a dyno? 

[Raux]

There have been anti reversion headers for cars for a long time - 25+ years.  Maybe it is something that can be measured on a dyno? 

my same thought. this is nothing new. basically looks like this

_____
    ___\______
<exhaust       engine>
    __________
______/

and you put it at equal distance from each cylinder
the distance is the tuning part     

[rockaduc]

I ran them on the Sportster tuner bike I built many years ago. They come about due to the trend of HD guys using really short open pipes and thus having lack of back pressure. For performance, they do not as good of a job as two-into-one pipes do but with some jetting you can get acceptable values and safe scavenging for the valves. Essentially they work for those wanting to have the chopped custom exhaust and are willing to sacrifice a bit of the performance.

If you are buying a Harely, do you really care about performance?

[junior varsity]

Well, I think they care about "relative performance" - that performance of the bike in stock form, compared to short pipes, compared to full length "tuned" pipes. Relative for their bikes, not compared to the latest, greatest litre bike.

[scott_araujo]

If their bikes run better with more backpressure, perhaps they needed tuning to begin with?

My two cents...

Agreed.  I think most Harley exhausts are made more for sound than smooth running or power.

Scott

[ID_DUC_MON]

Agreed.  I think most Harley exhausts are made more for sound than smooth running or power.

Scott

Sure, but then why do we end up spending huge piles of clams for aftermarket pipes/cans, K&N kits, Power Commanders and the such. There is factory performance and tuned performance. Stock, HD's run just fine; but then stock is boring. It is the open pipes that aren't offering the needed back pressure.