| Author | Message | ||
     Aaron |
Force makes a 2 into 1 for the Blast? This I gotta see. | ||
| Sarodude |
La La Lalalala, la lala la la (Smurfs tune - don't ask) -Saro | ||
| Xgecko |
 yeah Aaron it's for the super secret twin carb/exhaust 110hp 800cc blast motor | ||
| Blake |
 Oops, M2Cyclone00 and his comments on his M2's Force pipe had me thinking this was the OTHER exhaust topic page.  | ||
| Aaron |
Damn! I had my heart set on one of them pipes for the Blast. BTW, just to be contrarian, did you happen to catch the American Thunder piece on their Night Train project bike? They tested something like 18 different pipes on it, about half and half 2 into 1's versus 2 into 2's. The difference among various pipes was dramatic, like close to 20hp. The widest torque curve was with a set of Cycle Shack 2 into 2's. It was within a couple hp of the best peak result, too. | ||
| Bill00 |
Hey, I have a question. I was thinking about making an exaust using the stainless J bend pipes that Summet Racing and Jegs sells and use a Supertrap. Would 2 inch pipe be to big for the Blast? | ||
| Spooky |
Stay away from anything bigger than inch and three quarter. | ||
| Aaron |
from Denish: Size it for 280 to 300 feet per second mean velocity. V = (piston speed in fpm / 60) x (bore^2 / inside diameter^2) Size it for the middle of your powerband. Avg. piston speed in fpm is ((stroke x 2) / 12) * rpm Say you have a Blast and you want to size it for 5000rpm. Bore is 3-1/2 & stroke is 3-1/8. 1-5/8 o.d. pipe is 1-1/2" i.d., that comes out to 236 fps, a little low. 1-3/4 o.d. pipe @ 7000rpm works out to 282fps | ||
| Blake |
I guess my statement is applicable only to straight sectioned pipes. The CS 2 into 2 undoubtedly had a step or two or a crossover right? Okay, I'll shut and learn some more. | ||
| Aaron |
Nope, no steps and no crossover. We're all still learning. I periodically have my long-held beliefs shattered by reality. Freakin' dyno anyway. | ||
| Mikej |
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| M2cyclone00 |
Aaron, any plans to dyno any pipes on the Blast? | ||
| Aaron |
I dyno pipes on the Blast all the time. Mostly my own design, though, and I'm looking for top end power  ... generally not something you'd want to run on the street. The other day, I stuck a glass pack muffler (automotive style) onto the end of one of my pipes just for the hell of it. I was astonished at how well it worked, with no tuning at all. It only cost 2 hp on top and it really filled in the powerband. The chart was a little rough but it could be filled in with a little more tinkering. I've tested the Force. It's loud. I can't share the info at the moment. Wouldn't do you any good to see it anyway, the rest of my motor is so different, how it behaved for me and how it would behave on a stock bike are two different things. Blast fans have much to look forward to in the coming months. | ||
| M2cyclone00 |
Thanks Aaron, I'm looking forward to it. If you test the Force on a more stock Blast, let us know. I'd be interested. I haven't seen a dyno of it anywhere. If we put one on Lisa's (or whatever pipe we end up with) we'll have it dyno tuned & post the results. Dave | ||
| Dust_Storm |
Aaron, I've got a question on the pipe building for your Blast. Do you need special equipment to maintain the curves in the pipe to keep your velocity constant (eg, ripples BAD), and what kind of pipe are you using? (Stainless, but what make, doubtful I'll find it down at Homedepot..) I've considered making a custom header for my Blast to get the muffler out from under the bike, but i don't know enough about it. Directions to websites and books encouraged!  Also, the glasspak trick, was that on a stock Blast or your modified? ( I 've gotta spare set of them left over from highschool!.. hehhehheh, good ol cherry's..) No dino is bad, but anythings worth a giggle around the block  [Ds] | ||
| Aaron |
DS: I make pipes by purchasing mandrel pipe bends and then cutting and welding them together. I don't try to do any bending myself. Denish's Big Twin High Performance guide has a good basic explanation of exhaust theory with various useful formulas. You can get pipe bends at Zippers. I generally use these guys though. It's fun and interesting to mess with, but a little time consuming. Exhaust systems sure have a dramatic effect on an engine, though. What works best has a lot to do with the cams you're running, too, as well as various parameters of your heads. AW | ||
| Blake |
Long pipes also smooth the torque curve right? | ||
| Jasonl |
I noticed this while riding my S3. I just replaced the stock muffler with a V&H. The difference in the power band is VERY noticeable. With the stock pipe I had a much more gradual rise in power at 3k. With the V&H it comes on like a switch. OK...maybe not a switch but it's noticeable to me. Also have a Hypercharger installed as well. The funny thing is I don't remember my M2, which had a V&H and open air filter, coming on like this. The M2 had stock cams and lightning heads tho. But I wonder if wilder cams AND a free flowing exhaust cause a more abrupt power change. | ||
| M2cyclone00 |
I just received a fax from D&D showing a dyno chart for the Blast exhaust. Very impressive. The bike they used seemed to be consistent with dyno's from other stock bikes. It produced 28.9 hp just below 6000rpm. The D&D produced 31.5 at the same rpm. At just above 4700, stock it was 20.8hp, D&D was 26.8. Peak torque on the D&D was 29.8 at just above 4700rpm. Most impressive was that the D&D performed better at all rpm's from 2500 to above 6000. Lisa likes the looks of it, so we may just go that way. The chart sold me! Dave | ||
| Aaron |
Long pipes smooth the torque curve? Well, it's kind of a simplistic way to look at it, but overall I guess I wouldn't argue with it. If you just look at a pipe alone, no baffling, on a simple system (can't get much simpler than a Blast) basically the length of the pipe determines how long it takes a wave to travel from one end to the other. Since the wave travels at a constant speed, it'll only hit the chamber during overlap at a certain rpm. That shows up on the torque curve as a peak (if it's a negative wave) or a dip (if it's a positive wave). Change the length of the pipe and you can move that dip or peak up or down the rpm scale. If you make the pipe longer and move the peak down the rpm scale then yes, the torque peak tends to broaden somewhat. Make it shorter and move it up the rpm scale and it gets real narrow. You start giving up everything below, say 5000rpm, to get another little bit on top. You reach a point of diminishing returns after awhile. Not that I would ever explore such a thing  Keep making it longer and an interesting thing happens. As the torque peak slides off the chart to the left, a new one starts shifting in on the right side of the chart. And guess what, it's stronger. Basically, these waves are traveling up and down the pipe multiple times before they hit the chamber. You've now made it long enough that you're getting one less reflection. Which is good, because less reflections = a stronger wave. Problem is, that tends to be a *really* long pipe, longer than practical. Megaphone type mufflers like these:  are one approach to broadening out the wave, basically instead of generating one big wave by the pipe outlet, the cone generates a weaker, broader wave because the exhaust gas expands more gradually. On certain systems, long ones with less reflections, I've actually seen the steps in a pipe generate small torque peaks as well. I've got charts with 3 torque peaks on them ... the outlets (big) and 2 steps (each small). | ||
| Mikej |
So that picture would be the Blast 2-into-2 exhaust system?  MikeJ (It's been a rough two weeks, just waiting to get yelled at again, so forgive my foolishness.) | ||
| Aaron |
Here's an example of what I'm trying to say ...  (ignore the choppiness, long explanation) (this is certainly not the final tuning configuration of any particular race bike) Same bike, same day, same pipes, I just cut them shorter for each of these pulls. Notice how the powerband gets narrower as the pipe gets shorter. You start giving up a whole lot of mid range to get just a little bit more on top. How far you can push this has a lot to do with the spacing in between your gears. Wind it out and shift ... if you fall off that cliff, you'll slow down. It's quite a balancing act with an old 4-speed ironhead. That was one of our huge improvements between '00 and '01, a closer ratio gearbox that let me tune the motor to be peakier. | ||
| Mikej |
The red one looks pretty good. | ||
| Aaron |
Here's a 3-peaks chart:  This is a long system, although not really long enough to put the outlet's wave on the right side of the chart. The peak on the left is caused by the outlet. The other 2 peaks are caused by steps. In a short pipe, these steps won't generally show up on the chart, I think the extra reflections attentuate them too much. But they show up on a long pipe. | ||
| Aaron |
The green one has more power | ||
| Xgecko |
Tell us how it sounds. I was looking at the D&D but it was more money than I wanted to spend (my White Bros was coverd by my excess perdiem the D&D would have meant money out of pocket) | ||
| Mikej |
Yeah, but the red one looks a little more forgiving.  | ||
| Aaron |
One of the things you can do with a long system is line up the outlet's wave with a wave that's coming from a step. You get a double whammy that way. But of course there's a packaging problem. I think I've given up enough secrets for one day There's a whole lot more to exhaust theory than this. My goal is to someday feel like I halfway understand it. Tony: none of the systems in these charts had a muffler. Sound is best described as "painful". Even got harassed by the cops once during an exhaust development session. | ||
| Blake |
Way cool stuff. Thanks for sharing Aaron! We want more. So what you are basically saying is that size definitely does matter.  | ||
| Aaron |
Well, I think you can probably see how closely all this ties into your cams. Since the wave has this power to help or hurt intake flow during overlap, when both valves are open, adding overlap to your cams is essentially turning over more control of the powerband to the exhaust system. Hence a slip-on makes a bigger difference on an X1 than an M2. The real important cam spec for rpm range is the intake valve close point, since that's closely tied to the inertia of the intake charge and therefore it's *really* rpm sensitive. So when people talk about a "good marriage" between the cams and the pipe this is what they're getting at. If the cams have enough overlap to let the pipe do it's thing, which most performance cams do, then you want a good match between the pipe's rpm range and the intake valve close point's rpm range. It also gets into head prep. Overlap is a low lift event, if you've got conditions that shroud the valves at low lift (for example, big valves in a small chamber, or sunk valves for v-v clearance) your overlap effectiveness drops. I recently saw someone who intentionally sacrificed overlap effectiveness in favor of other things, like bigger valves and more compression. He did it in a case where he knew the exhaust was going to be a constraint, so rather than fight it, he blocked it out with narrow overlap in the cams, and took advantage of that by running bigger valves and milling the heads more, since less overlap helps valve to piston clearance (it needed race gas). Actually worked pretty good. But, if you can use a good exhaust, overlap effectiveness can be very helpful and you need to design it in. All this is just my understanding of things, I'm sure you can find folks with a different view, yada-yada. |
