Stepped or not stepped is a matter of the build components. As far as who did it first I think that Cycle Shack and HD did it long before anyone else, so if your worried about who copied who, better look to those that did it first. Better yet, look to see who is building them right as that should really be at the top of your list for it to work right in your application.
I have found this to be and interesting Read. Granted it is wrtten by a vendor, RB Racing, but still and interesting read.
I think of the X-pipe as more like and eductor/extractor.
When the cyclinder fired, it pushes exhaust gas out the header, when that gas reaches the void space in the X, it changes pressure to velocity as low pressure on the other side of the path. That will/should create a vacuum in the Exhaust header of the cylinder that is about to fire, thus improving the exhaust flow/take away.
It's not a new concept, I have seen antique Hot Rods with offenhauser exhaust manifolds. The Middle 2 cylinders on each bank shared a slightly larger header.
Harley Exhaust System Designhttp://www.rbracing-rsr.com/exhausttech.htmExcerptsTo keep this simple, it just means cooler is slower. Those really long fat pipes you see are decellerating the exhaust as they head out past the rear wheel.
Keeping things simple, this is summed up as “the larger the tube, the lower the speeds”. For the expanding, hot gases a slower speed means a higher pressure and, conversely, a higher speed is a lower pressure
Generally we want a lower pressure and a higher speed in the exhaust. Having a highly negative pressure in the exhaust during the overlap period when both inlet and exhaust valves are open, is the key to making power
The primary tube size will go up in relation to engine size. The size of the tube should be slightly larger that the exhaust port area which, in itself, will most likely be “D-shaped”. The “D-shape” flattens out the floor to the port to increase the flow on the “short” side or floor of the port. Having the tube size much larger than this “slightly larger” is no benefit whatsoever.
Simply put, an increase of of 1/4” in diameter will shift the rpm band up about 600 rpm for the same size engine.
Decisions as to what tube size to choose aren’t very scientific but are based on experience. We can sum this up in Twin Cam terms: 88”, 95”, and even
103" motors should use 1 3/4” primary tubes. If the engine is a 103” TC88 you have a choice between the 1 3/4” and the 2” designs. The decision for the 103” rests with your intentions and the design of your engine. The 103" motors generally do not make much power, are limited by valve size and reside in a heavy 800 lb sled. In general, stay with the 1 3/4" design. Now there are
110", 113" engines that are focused on horsepower with inlet valves 2.100" or larger and with 200lbs of cold cranking pressure or more and big cams. In this case
a 2" primary tube design is called for.Length and diameter is an issue. To put it simply,
longer, smaller primary tubes for lower rpm, and
shorter, fatter tubes for higher rpm. In the case of engine displacement a smaller engine requires smaller primary tubes and a larger engine requires larger primary tubes. Putting too large a primary tube on an engine will shift the torque up the rpm scale. It all has to do with the length and volumes of the tubes.
Heat is power and loss of heat means a loss in velocity. People make all sorts of claims about wrapping headers in thermal wrap, applying ceramic coatings both inside and out and the heat retention properties of stainless versus mild steel tubing. Let's get real about this issue...You aren't going to measure the difference between chrome and ceramic coatings and
it really boils down to a question of aesthetics and practicalityFor Harleys you should ponder this...
Stepped headers are not for low speed or part throttle operation, which are exactly the regions you spend most of your time in. The "cone shape" will cause the scavenging wave to be stronger and narrower . This can aid peak rpm hp numbers but other numbers will suffer.
What I happen to like about the X-Pipe is that to me it looks the closest to the OEM HD Exhaust and uses the the HD OEM Heat Shields.
The Jackpot version does state that it can use HD Heat Shields, thw Vance & Hines "Power Dual" doesn't keep the HD Lines to me and the Wegner Manifol just looks Fugly to me.
So, once again back to your own personnal preferences.
Cheers
DR
Author
Topic: Anyone know anything about the new Fullsac X pipe? (Read 6643 times)