| Author | Message | ||
     Dhays1775 |
I was painting my muffler today and had a wild thought. I know there are dual exhaust ports that merge into a collector and then merge into the muffler. Essentially a 4-2-1 exhaust. My question is this: Why isn't the initial merge after the head more of an offset design? Like this-  I'm sorry if it's a little hard to understand. I think that merging one port right behind the other would reduce the size of the exhaust pulse and possibly increase the exhaust velocity. Would there be any feasibility to this? | ||
| D_adams |
If you look at the stock header, it already does that. Yes, it merges into a common collector right after the head, but the length is different for both of the small pipes. From there, the front header is considerably shorter than the rear, by 6 or 8 inches, which again gives you that same offset. You have a 72 degree twin, so the firing pulses are off to begin with, add that to the already unequal length headers and you have your velocity requirements met. I don't have hard data to back up the argument of unequal length headers being better than equal, but what the engine is tuned for and "sees" in the current form seems to work pretty well. I know there's been guys build equal length headers for XB's. I don't know that any of them have shown a significant improvement over the stock design unless it was for a specific section of the powerband, ie; up near the top end and with much larger (1/4" or even 3/8") primaries. The tradeoff would be a low end loss of power. Running straight pipes with no merge or crossover changes things also. You'd lose that scavenging pulse from the merge, which changes tuning requirements. I do know that 1125's breath better with larger (2") primaries, so there's some restriction there if you will. I do not recall who told me this, but the stock 1125 headers _might_ be flow limited to about 150 hp. Physically pushing X amount of gas through a 1.6" ID hole has it's limits. I'd have to find out the max cfm it can flow, I don't know what it is off the top of my head. Did I ramble enough for you tonight? www.keda-design.com | ||
| Dhays1775 |
Dean, you did a pretty good job. After I opened this thread, I saw some pictures of the 1190 Typhon on the track. It shows something similar to what I'm talking about. The twin tubes coming from the head have a much longer runner than stock. I think it's just the EBR race exhaust though. I think Erik did that on purpose... | ||
| Dhays1775 |
Oh yeah, I know that Erik didn't build the Typhon. It was built by a European race team from an 1190 full race bike. | ||
| D_adams |
There are a couple of different incarnations of the EBR race exhaust. Most are styled similar to the stock pipe, they sweep over to the right side of the motor. The new design is straight down the center for the front pipe. The other is the sidewinder drag pipe, but it looks like it's based on the original design.   I'm still thinking about doing one just to see if I can do it. (Message edited by d_adams on December 17, 2011) | ||
| C818919 |
id be more interested if you put a can on it dean |
