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D_adams
| | Posted on Tuesday, December 08, 2009 - 12:02 pm: | 
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Good info there, but I'm now wondering why the stock pipe goes from 1.75" primaries, into a collector and from there, it's a 2.5" pipe. If the secondary tube length is 12-17" at 2", why would they design it differently than what was just stated? Did I miss something? Why is the race exhaust from Buell a 2.5" exit pipe? I know the collector is extremely long, to the order of 10" or so. Very smooth merge for that one. Any other thoughts or comments? |
Torquaholic
| | Posted on Tuesday, December 08, 2009 - 01:40 pm: |
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The fact that this exhaust engineer/expert said to run 2" after merging dual 1.75" while Buell race exhaust runs 2.5 is worth talking about.
...could it be due to Buell's race bike being designed to run harder in the higher rpm bracket? From the pics I have seem, it seems they have larger primaries on the race exhaust. Perhaps the race exhaust is dual 1 7/8" primaries into 2.5"? Maybe the 2.5" is due to how short the muffler section is beyond the Collector. I find it reassuring that the expert mentioned some specs about the merge collector needing a narrow angle and Buell's race pipe merge collector is indeed a very narrow angle, the overall length of the collector on the race exhaust is likely due to the angle they were using.
For those of you with money to blow and a real interest in possibly designing a full exhaust... as long as you can get the specs for this engine, Dynomation seems to be a great program for engine and exhaust design.
I received an email back from a Dynomation rep. here's the text:
Thanks for your email and your interest in Dynomation-5.
Dynomation does not operate from a “database,” per se, but instead models the physics of a 4-stroke engine based on the specifications of components supplied by the user through our Direct-Click interface (more info available on our website www.motionsoftware.com).
Dynomation-5 will model up to 3 intake and exhaust valves per cylinder, and will even model up to two exhaust pipes per port (I believe this configuration was used on some Rotax engines).
I believe you would find Dynomation-5 helpful in designing a custom exhaust system for this engine family.
Thanks again.
Larry Atherton
Motion Software, Inc.
Software Development |
Torquaholic
| | Posted on Tuesday, December 08, 2009 - 02:10 pm: |
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Concerning the stock pipe's internal dimensions, that's beyond me. The engineering that went into making that pipe perform the way it does is out of my league. Why did they have a 2.5" main pipe, but have such small exit tubes? what's up with what looks like an expansion chamber integrated into the Y-pipe... why all the reversion chambers and different pipe sizes.. why did they place diffuser holes in the smaller tubes in the patterns they did? ...way beyond my level of comprehension.
After giving it a few minutes of thought... just wanted to throw this out there:
What if the Buell race pipe isn't designed for all-out max power potential, but rather Torque is the intended goal?
From my experience in some car racing classes, vehicles are usually limited by power/weight ratio; no one really mentions Torque (as far as I remember). As a result, there are plenty of engine builds that make a ton of low-end grunt, but sacrifice some power up top to keep within the racing rules.
More torque pulls you out of the corner quicker than the next guy, which would really help in a road race. As long as everyone is roughly the same power/weight ratio... straight line contests are pretty even. I can't help but think of the Daytona series with all this in mind, especially after visiting the Erikbuellracing (EBR) website and seeing the "1125R DSB spec – 135 RWHP" racebike mentioned.
135rwhp? Dris' torque hammer and mapping make more than that on a stock bike....the Other Sport Bike performance flash makes that much with a stock muffler!
I might be way off, but the idea crossed my mind about the Buell race pipe's intended goal and I thought I'd see what you all think.
Maybe that's why EBR decided to go with the FMF full exhaust on the 1125RR and not the Buell race pipe... maybe because something in the FMF design out performs the Buell pipe to allow them to hit the mark with the "1125RR American Sport Bike spec – 175 RWHP" as seen on EBR. |
Bob_thompson
| | Posted on Tuesday, December 08, 2009 - 02:56 pm: |
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Still some great questions. For the idea I used on my system, I pulled from car header design that has been around for many years and I usually saw, on each side of V8 engines, 1 1/2"-1 5/8" primaries feeding into at least a 3 1/2"-4" collector.
The "theory" I pulled from was using the original head pipes, two into one 1 3/4" for each cylinder and I then went into a 2 1/4" collector and the same size in and out of the muffler. This is MY answer to Deans question-
"Good info there, but I'm now wondering why the stock pipe goes from 1.75" primaries, into a collector and from there, it's a 2.5" pipe."
2 1/2" from Buell because they make way more H.P. then mine, for sure.
And again the theory is to keep high gas velocity all the way to the collector and then a larger collector pipe to easier scavenge the exhaust gases along with a high flow muffler of the same size. I believe this at least keeps some low end torque without significantly reducing top end H.P.
Without tooting my own whistle but it has worked fine for my use and sounds good.
I am still really enjoying this thread so keep 'em coming guys. Bob |
D_adams
| | Posted on Tuesday, December 08, 2009 - 05:06 pm: |
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I'm still planning on doing the 2.5" system just to be a guinea pig. If it works, then great, if not, I'll take a step back and maybe go the route that Bob took and try a 2.25" system. They're relatively cheap to make if you don't count your time and since it's for me, I don't mind doing it.
Bob, from what I could tell from the video, the sound of yours is the closest I've heard yet to what I want. I just want mine in stainless. |
Bob_thompson
| | Posted on Tuesday, December 08, 2009 - 05:14 pm: |
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Dean, you've been actively doing more here then most others and I for one am looking forward to what you will come up with. Keep up the good work and thanks for a vote of confidence. Back at ya on that. Bob |
Redscuell
| | Posted on Tuesday, December 08, 2009 - 10:31 pm: |
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Torque's posting from the exhaust designer is an eye-opener. I believe I DO understand the reasoning that went into every design decision of the stock muffler EXCEPT the half-sized outlets.
However, I DON'T understand several of the designer's recommendations: "no positive uphill steps", "no stepped header". Please explain, torque.
My mod will remove the first 1/3 of the muffler, and replace it with a y-pipe that receives the equal-length headers; and understanding the designer's recommendations might change features of it. Will be done Monday (your Sunday) so time's a'wastin'. |
Torquaholic
| | Posted on Wednesday, December 09, 2009 - 09:11 am: |
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Red, there's a lot more info in this one page than I can regurgitate.
This may include some info covering stepped headers.
http://www.rbracing-rsr.com/exhausttech.htm
not enough time to write; have to get back to work.
Let me know if you still need some clarification and I can try to email them again.
(Message edited by torquaholic on December 09, 2009) |
Redscuell
| | Posted on Wednesday, December 09, 2009 - 07:40 pm: |
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Fantastic; all the add'l info I needed. Will post up results, likely next week. |
Blower1
| | Posted on Sunday, December 13, 2009 - 04:11 am: |
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It would be interested to see how equal length headers work with oem muffler.
I´m going to make a new front header, which is equal length with rear header and fits to the oem muffler.
First I need to find a used front header and then time to modify it. |
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