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Title: Torque/Anti-reversion cones Post by: WetDuc on February 15, 2010, 03:22:46 AM 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.lachoppers.com/catalog/display/1178/index.html) http://www.patentstorm.us/patents/5165231/description.html (http://www.patentstorm.us/patents/5165231/description.html) Title: Re: Torque/Anti-reversion cones Post by: battlecry on February 15, 2010, 06:28:11 AM 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... Title: Re: Torque/Anti-reversion cones Post by: ID_DUC_MON on February 15, 2010, 08:43:41 AM 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.
Title: Re: Torque/Anti-reversion cones Post by: Bill in OKC on February 15, 2010, 09:21:56 AM 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?
Title: Re: Torque/Anti-reversion cones Post by: Raux on February 15, 2010, 10:00:25 AM 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 Title: Re: Torque/Anti-reversion cones Post by: rockaduc on February 15, 2010, 04:18:23 PM 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? [roll] Title: Re: Torque/Anti-reversion cones Post by: junior varsity on February 15, 2010, 05:24:59 PM 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.
Title: Re: Torque/Anti-reversion cones Post by: scott_araujo on February 19, 2010, 02:35:13 PM 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 Title: Re: Torque/Anti-reversion cones Post by: ID_DUC_MON on February 19, 2010, 03:33:14 PM 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. |