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  #11  
Old 13th August 2014
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Quote:
Originally Posted by madlim View Post
Aaron, what is your professional opinion about the performance issues with these both pipes? Undeniably there are big differences fiddling with the baffle but the torque curve are still pretty uneven. Is it a combination between a too restrictive baffle and too short or long headers?
Yes

Obviously, it's a very restrictive baffle, causing a lot of pumping losses which just murders the top end.

But pumping losses are only part of the equation. The goal of a good pipe design is to present a negative pressure wave at the chamber during overlap, i.e. that small window in time that comes along every two revolutions of the crank when both valves are open and the intake and exhaust are connected together. That's an absolutely critical time for the pipe to pull, because if it does, it gets the next intake charge moving before the piston even starts going down, which drastically helps cylinder fill, thus moving the torque up.

Conversely, the worst thing that can happen is if the pipe presents positive pressure during overlap. The intake charge that's sitting in the carb and manifold, instead of getting sucked into the motor, it gets shoved right out of the carb. You get this fog of fuel standing outside the carb. Then the piston goes down and sucks it back in again. So you end up with a charge that goes through the carb 3 times: in, out, back in again, picking up fuel each time, making the motor go rich. You have a massive hole in the torque curve accompanied by a rich afr.

The issue is that these pressure waves that are traveling up and down the pipe are moving at a pretty constant speed, the speed of sound, regardless of the rpm of the engine. So you have a situation where you may have the wave timing working perfectly, a nice negative wave arriving at the chamber during overlap, pulling hard and making big torque, and then you change the engine rpm (this changing the timing between overlap windows) and it's all screwed up and there's a positive wave arriving instead.

So it's up to the pipe designer to figure out how to present a negative wave over a wide rpm range. Diffusion of the wave, and in the case of a 2 into 1, using the pressure waves generated by the opposite cylinder in an advantageous manner, is how that's done. Pipe diameters and especially lengths are big factors. Get it right and the pipe doesn't need no stinking baffle to create back pressure and rob power. Look at the Patriot, it runs best with the baffle flap wide open.

But pipes are all about looks, sound, and packaging. So what ends up happening is the pipe gets designed for these things, and then a baffle is stuck into the end of it to try to make it run decent. A properly designed unbaffled pipe will always beat it though, because it won't have the pumping losses. And RSD didn't even get that baffle right anyway, it murders the top end.

Sorry if my bias is showing through, I generally just try to show dyno sheets and let people form their own opinions, but I'm just not impressed with anything RSD I've seen yet. Fine if you don't care about performance I suppose, but my life revolves around performance.
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  #12  
Old 13th August 2014
madlim madlim is offline
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Thanks Aaron, I appreciate your honest opinion. For me performance matter of course, but also looks. Sadly I bought my Slant before you tested it, otherwise it wouldn't be sitting on my bike... So now I'm stuck with a pipe that I like the looks of but not the performance. Ones I have my cam installed and it's time for a dyno run I'm gonna try to lengthen the headers and see if I can get better performance out of the Slant, otherwise I'm out looking for a new upswept 2-1. Again...
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  #13  
Old 14th August 2014
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Oh, and big thanks to KellyJ for letting me test his pipe!
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Old 14th August 2014
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This test is now posted on our web site, along with the other pipes we've tested: http://www.hammerperf.com/ttxlexhaust.shtml#rsdtracker
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  #15  
Old 27th August 2017
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How to make over 100hp with this pipe? Chop it hard: http://xlforum.net/forums/s....php?t=2037381
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  #16  
Old 3 Weeks Ago
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I know this is an old thread but I just stumbled across it. I recently purchased the Tracker exhaust.

I was wondering if you had more details on how you cut the baffle?

I appreciate any info if you can remember that far back. Thank you!
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