| Author | Message | ||
     Kinder |
So as some know I am having some custom equal length headers made up. Right now I can save money and low end by staying stock size and just lengthening the front header... or Increase the dia of both pipes. I was planning 2 1/8" but have decided if I do this I gonna go with 2" to save a bit of low end. So what would you people do? (and yest track time has already been planned and this money does not take away from that. :P ) | ||
| D_adams |
What purpose is this aimed at, ie; road race or drag? What gauge tubing are you planning on using? Any other mods to the engine or will it stay stock? When you say equal length headers, have you calculated out the tuned length you really need for whatever rpm target you're aiming for or is it just guesswork at this point? Are you going 2-1, 2-2 or 2-1-2? | ||
| Ridenusa4l |
id think an X-pipe would be very beneficial in any sense, however it is very hard and indepth to do, but if you know what your doin, it can be done in a timely fashion with a good pay off FWIW Jake | ||
| Kinder |
Its going to be a 2-1 system. I have done some looking around and while solid gains can be had on 2-1-2 systems no-one seems to have had any real success with a 2-1-2-1. The can I'll be using has been mapped/designed for the rear tube length (i can't member right now but i want to say 22-26') so I should see some better performance out if it with the front being the same. harleys also always see a gain when going equal length. While equal does tend to free up some ponies it does not help torque out like unequal length does. I'l be using 16-18 gauge tubing. The trade off for velocity vs flow is what I'm stuck on. As Velocity helps with torque and flow help with HP. Now the last consideration is if I go bigger then I have to modify the stock and the slip on to acommodate. My goal is to test if there are any gains to be had with differing slip-ons by going equal. | ||
| 1_mike |
I've built and helped build a lot of car headers over the years and understand a little about how they work. Lots of experimentation on my own dime. You asked...I think (other than maybe equalizing the actual length) using a larger diameter tube in the primary OR secondary part of the system is a huge waste on a street or even track-day bike. No tuning in the world will bring back lost exhaust gas velocity...that is..low/mid rpm power Now if this is a race bike (drag or road), then yea...maybe. But be prepared to experiment even doing that. Design into the system and make some 2" secondary (the bigger tube) extensions to try to tune the system...the word here is..."EXPERIMENT". Have fun...but be fully prepared to have a very high rpm power curve..! Mike P.s. - Just to clarify...the header tube has no clue what the engine is used for...car, bike, jet ski, sno-blower... Internal cumbustion engines work pretty much the same...worldwide. Even two-cycle tricks work well on four stroke engines (see the Barker collector design!). (Message edited by 1_mike on April 13, 2011) | ||
| Kinder |
I agree that if I go bigger it will only be of use at high RPM's/ track use. Now the tricky part is I'll be using a PCV w. Autotune (the 2 w/b sensor model) If I leave it hooked up it will tune to what ever AFR/ rpm I'm after so it should take advantage of the flow. It will be at higher RPM though. So now I'm stuck. I'm leaning towards same size for 2 reasons though. 1) Keep the velocity and thus not lose as much low end since some will be lost going equal. 2) Save costs on only 1 pipe and no mods to stock/slip ons to fit a larger outlet. | ||
| Ridenusa4l |
If you're gonna do it, do it right, use the Erik Buell Racing race exhaust as an example, at least increase the primaries one size and extend them down a ways so that way that big rotax can BREATHE!! and plus it looks sexy taboot lol Jake | ||
| D_adams |
Personally, unless you're after absolute maximum power, I wouldn't go over 2" primaries. If you go larger with the engine displacement, then you might go up to 2.125" but that would be pushing it, especially if you use thin wall tubing. I normally use 16 gauge stainless myself. Mine is a semi-stepped design, although the step is pretty small before the collector. I'm not going to go into design/theory on exhaust, there's plenty of info out there to make informed decisions on how to make it work. Sometimes trial and error is the only way to prove it out, other times you get lucky. Without doing a lot of tuning, I doubt the equal length headers will really get you much for a performance gain, I'd be extremely surprised if it shows more than 2-3 hp over the Erik Buell Racing full system. They knew what they were doing when they designed the motor and exhaust to match it. Yes, you can improve over the stock design (on a race setup) because they were hampered by the EPA. I have yet to see anything match their race system for performance. I got close with mine, but it's just a slip-on setup. Even the full FMF system didn't post anything better. I think the low end performance suffered some, but I never saw a back to back comparison of it. | ||
| Albert666 |
just make them 1 7/8" | ||
| Anonymous |
Exhaust system design is a detailed and exacting science. Be prepared to get it wrong many times unless you really know what you are doing. And then someone has to write a program for the ECM for each iteration. Do you really have that much money and time to spend?! | ||
| D_adams |
1 7/8" tubing.  Other stuff. Lots of stuff needs welded here... all 304 stainless.  | ||
| Dannybuell |
Ridenusa4l - the keda rt4 has an x pipe collector. | ||
| D_adams |
Not really an X-pipe per se, just a merge and then splits again later.  | ||
| Dannybuell |
I may have exaggerated but the x in an x-pipe is just a smaller merge isn't it? | ||
| D_adams |
This is what I would call an x-pipe.  | ||
| Drawkward |
Damn it Dean, those pictures are making me want to start thinking about building an exhaust again!!! | ||
| Kinder |
Technically yours in an X pipe Dean. Maybe not an efficent one but one nonetheless. It was one of the reasons I was considering your set-up. I bet it is helping with some gains.  | ||
| D_adams |
The little pic I posted is what I'd call a true x-pipe, what I build is a lot longer in the middle, so to me it's not really a "true" crossover or x. So far, the best I've personally seen out of it is a 15 hp gain (peak) and about 21-22 at 8000 rpm. I haven't tested the RT-3 yet with the Erik Buell Racing tune, although I'm planning on doing so soon. Just comparing dyno's (yeah, they're all over the place, but they're somewhat similar in results) my local dyno showed me 122-123 stock. I've seen 137 here. Al's shootout, same thing, 122 hp, 137.8 peak. Erik Buell Racing, no baseline, but 137 there also (personally observed) BUT... when they tuned it, it made a wee bit over 140. Until I actually do my own dyno or someone else does, I can't/won't publish the actual number. It was pretty respectable though. I guess that means either I got extremely lucky, or I have a decent grasp of how to make a slip-on pipe, although I by NO means know everything there is to know about it. I give credit to Erik Buell Racing for making the tune work as well as it does though, they put some serious time into getting out of it what they did. | ||
| Ratgin |
RT-4 with a db killer and matching Erik Buell Racing tune for low end power would be just the ticket |
