[byl]

Was wondering if it was possible to run the exhaust of each cylinder to is own can without going through a collector?

The only reason I can think of for not doing it would be to keep the same back pressure on each cylinder!

On the other hand, no collector means less pressure drop in the exhaust line so quickest gas realease so more power, no?

byl

ps: might be a very stupid question though!!

 

[Guest]

I had this question before, someone "expert" told me the crossover pipe is to balance the pressure of cylinders.

 

[Andrew_Cornett]

Back pressure does not perform the same roll in 4strokes as it does in 2strokes. Thus the expansion chamber in the 2stroke pipe.

The only purpose of the crossover that I can see it to save on pipe routing. If you notice from the head to the point of the crossover, the pipes are the same length. It saves on money to run the little extra pipe needed from a crossover to the can than it does to produce a pipe that goes straight from the head to the can and can only be used on one head and not the other. Take most custom chopper or cruisers, they have straight pipes from the head.

 

[stevey]

the cross-over does two things. first, it allows
distribution of the muffler volume. those big
cylinders would require a huge muffler if each cylinder
fed into its own muffler. by sharing, however, (the exhaust pulse from each cylinder passes through both mufflers) the volume
of each muffler can be reduced by 1/2. 2nd, judicious placement
of the connection can provide a favorable pressure wave
to the exhaust valve over a narrow rpm range, thereby
filling in (typically) mid-range dips in the power curve. this is why you see various configurations like 4-2-1 or 4-1 or
4-2-1-2 on your typical transverse 4 .... they're trying to get
the mid-range flat spots out of a high-rpm power curve.

 

[908SSP]

MBP did back to back testing with a special header so that they could change the size of the cross over from none to very large without altering the rest of the exhaust in anyway. Their testing showed a loss in horse power at rpms above 5k in the system with no cross over.

 

[Guest]

Stevey is on the money, except for some semantics- when the exhaust valve opens, the cross over and hence the pressure waves bouncing from the exhaust valve to the exhaust exit are timed so that the pulse is moving away from the exhaust valve (when it opens), thereby sucking in more of a charge while both the intake and exhaust valves are open.

Basically, the crossover helps pulses that are exiting the exhaust from one cylinder to help scavenge/fill the other cylinder. This is done to help fill holes in the power curve made by the cam profiles.

The flip side of the coin is air box resonance, basically doing the same thing from the other end- even though the monster airboxes are kinda tiny.

Ofcourse there are other variables, the whole engine has to work as a whole.

If I made any mistakes, feel free to correct me- I'm, no expert!

 

[AlexB]

I'm with stevey and D-C.

 

[niuginisbk]

Hey Alex, you got a link to that MBP test.

I'd like to have a look at it if possible.

 

[Norm]

Exhaust fabrication for maximum HP is quite an art, but for practical purposes on our bikes, it doesn't really matter. I run individual exhausts on a couple of my bikes & power or throttle response isn't a problem.