what is the reason that race teams over the years went from ,example 4 into 4 to4 into one. is 4 into 1 more effecient or just a pluming issue. a an example the vintage hondas, mvs all ran 4 into 4. opinions ? same with 2into 1.
Less weight + more power. The complicated bits from automotive apply equally to motorcycle engines. http://www.superstreetonline.com/how-to/engine/1309-hows-and-whys-of-headers/
The old 4 into 4 designs were popular back in the 60's/70's before the science was evolved. A lot of CBX's had 6 into 6 pipes...looked cool and sounded fantastic...probably not the solution for peak performance.
From what I recall reading....4 into 1 lends itself to maximum top end power perhaps loosing a bit of low-mid. 4-2-1 a little less top end gain with a more even power spread across the RPM range.
Rob Muzzy might argue that individual pipes made more power. I also hear reverse megaphones are good for tuning...must be why you see 'em on individual pipes.
I can tell you without any doubt, a 2-1 will always out perform a 2-2 system. At least on a Harley or twin. I know the jokes are coming, but it stands to reason that the same holds true for I-4 engines.
Its complicated. All depends on the configuration and what the engine wants. Flat crank inline fours scavenge better with a four into one system typically although a tri y type 4/2/1 will make a wider spread of power normally. There is so much that is involved in exhaust design from cam timing and overlap to port volume and runner length....
Except....uh....crank configuration. Performance is too general of a term when youre referencing "race" motors. Drag. Landspeed. Flat track. Roadrace. Lots of differences there. But I know that the people who developed exhausts for cb350s knew what they were doing and 2-2 for road racing is the way to go.
The cb350 is a 180 crank which is why 2-2. I did the a 2-1 for a few years but ditched out because of ground clearance. I didn't notice any difference I could associate with the exhaust, but the 2 builds were significantly different. Different crank phasing on twins makes a big difference.
There are lots of SAE technical papers and some texts on this subject, but the bottom line is that 'tuning' an engine is like 'tuning' a muscial insturment like a pipe organ (a real one powered by air, with bellow or a blower). In an organ, the pipes are tuned to resonate at different frequencies (notes) by altering the pipe diameter and length and thus altering the interaction of the pressure/sound waves inside of the pipe. An engine is similar, except instead of tuning it for a particular frequency (note), the goal is to tune it so that there is a local negative pressure wave at the pipe entrance, e.g. at the exhaust port, at the point of exhaust valve opening, to help draw waste gases out of the combustion chamber. Of course the tradeoff is that this tuning can be made to work well at a very specific rpm, but then may be detrimental at other rpms, so the balance is in helping at the particular rpm of interest, without hurting too much throughout the rest of the usable rev range. In real life as you add the same effects that are tuned into the intake system (except tuning is for a local high pressure at the intake port), plus multicylinder engines of different configurations which allows interactions between cylinders, e.g. using the exhaust pulses from various cylinders together, coupled with the various torque curve shapes and engine response characteristics desired, and there's no end to the amount of exhaust configurations that might be worth trying. There is no 'right' answer, it all depends. The Honda RC211 and 212 V are an easy way to see how even with the same engine the exhaust can change quite a bit depending on what parameters are a priority. Compare these 2 phots and the big difference in collector length from ports and pipe length post collector. Honda seems to play with this area ALOT, I assume the others do as well but the Honda rear pipe gets photographed alot so the changes jump out more compared to others. In summary, I HAVE NO IDEA, it all depends.
