Exhaust pulse tuning.

[nilsson]

Hello.

Have some questions of pulse tuning. Have read some tech articles, but wonder if i got it right.
If we start some time before the exhaust valve is open.
Than we have low pressure in the pipe, created by the inertia in the exhaust gas that have leaved the pipe on the previous stroke.Coz the valve is closed and when the gas leave the pipe it create some "vacuum".
Exhaust open and the gas comes out, and i high pressure pulse goes thru the pipe and reach the collector. After the collector that area of pipe is bigger and the collector acts like an open end to the header pipe. A pulse that meet an open end, change direction AND became a low pressure pulse. When we are in the "tuned" rev range, this pulse arrive to the exhaust port in the cyliduring the overlap and helps to "suck" fuel/air from the inlet.
Have i got this right?
What happen next, will the exhaust port in the head act like an open or closed end. I mean its open, but you have a valve that maybe disturbe, so maybe it act like an closed end.

1.If it act like an closed end, than it will still be an suction pulse, that will travel to the collector again and be a high pressure pulse that goes back to the head and maybe push air/fuel mixture that have escaped to the exhaust pipe, back to the cylinder?
2 If the exhaust port act like an open end, than the pulse be translated to an high pressure puls, in the exhaust port. And maybe stop the air/fuel mixture from getting out in the exhaust port.
Is some of the scenarios 1 or 2 true?

If you look at 1 cyl offroad/moto-X cycles, it seems like they not have the increase in areas that multiple cylinder engine have in the collector. Will the pulse in these engine change direction when it get out of the muffler?


What the theory between the cans that some exhaust have between the pipe in the manifold? Like Youshimura duplex?

Will be very happy if someone could help me to understand this subject. All above is questions an not statement.

Thanks for a great forum

//nilsson

[900HP]

Maybe this will help.....

http://www.exhausting101.com/

[cgarb]

What about a 1cyl engine like a briggs?

[Warpspeed]

When we are in the "tuned" rev range, this pulse arrive to the exhaust port in the cylider during the overlap and helps to "suck" fuel/air from the inlet.
Have i got this right?
What happen next........

Yes indeed, that is how it is.
What happens next is the exhaust valve closes.
And what goes on in the header pipe after the exhaust valve is closed is of no particular interest.

[groberts101]

If you look back just a few pages through the last few months around here.. there's been a lot of discussion about this. Lots of smart creative minds floating around this joint if you know how to search and where to look for clarification.

When you get more deeply into it becomes quite obvious that there are several major factors that contribute to the final result. Understanding and execution being the two primary ones, IMO.

I generally look at the art of exhaust tuning to actually be much more like the art of compromise when it comes to anything being driven on the street or within chassis/sound rule restraints. At that point.. an "optimum design" quickly becomes an exercise in damage control and we do what we must.

Here's a few links I had saved but don't sell the search function short.

viewtopic.php?f=1&t=42375

viewtopic.php?f=1&t=42469

And another one getting into induction phasing and whatnot. IMHO, you can never fully understand the exhaust side of things until you work towards fully grasping what happens at the topside of the equation.

viewtopic.php?f=1&t=35634

[jacksoni]

also: viewtopic.php?f=1&t=42487
And: viewtopic.php?t=31606

[nilsson]

Thanks