https://www.youtube.com/watch?v=Q49ZWyxjBr4
How much back pressure is in an oddy exhaust pipe ?
I did a test.
Is the there a reason ? --- Yes.
CO

I never checked pressures before but take a straight wire like a coat hanger and stick in the pipe feel around if its a all stock pipe it will have insulation inside with perforated metal holding it in place sometimes the spot welds break and the metal drops down and obstructs the flow. You still running the stock silencer? If so they can be modified internally for better flow.

What’s the reason for the test?

I don't know if I should even say --- LOL.
I want to build my own pipe this winter.

Also -- My little brain says that pipe builders are "cheating" by using back pressure to hold back the fresh intake charge.
I don't think many of these pipes have a return pulse that is not strong enough to let all of the exhaust out followed by the fresh charge which is then suppose to be shoved back into the cylinder due to that return pulse.
To me that is what is "suppose" to happen.
This can only happen IF there is NO back pressure and ALL of the exhaust is out, followed by some of that fresh intake charge.
To my little brain, if there is back pressure then that means there is back pressure in the crankcase and therefore as the piston goes up it must create that vacuum to over come the back pressure FIRST before any new charge can be sucked into the crankcase. That means you are NOT getting as much fresh charge as you could be getting and that causes power loss.
Am I making any sense ? Or am I just on smoke ?
CO

Well that’s a lot to digest..lol In my uneducated way of thinking, if you’re right, than no pipe at all would be better, but we know that isn’t true. The tune pipe is better than no pipe, and also better than a straight pipe, so the back pressure has to be serving a purpose, not that I can say what that purpose is.

Once the rings are past the exhaust port, that would relieve the back pressure from the exhaust, like you said into the crankcase, which is vented, so no real problem for the returning piston.

Or am I on the smoke too? Lol

Not so.
Yes the back pressure is in the crankcase but ---- No it's not "vented" because there is still almost 4 psi pressure in the exhaust.
Then as soon as the rings cover up the exhaust port again as the piston rises there is still that 4 psi in the crankcase.
The Engine can't "suck" fresh charge until that back pressure trapped in the crankcase is over come first.
Therefore you lose some fresh charge that you could be getting if that back pressure wasn't there in the first place.

The pipe reflective wave is suppose to do the work and shove the fresh charge that leaked out into the exhaust back into the cylinder ------- No ????

If we are relying on back pressure to "hold back" that fresh charge then the pipe ain't doing it's work.
That's my argument.
CO

Maybe we are both on smoke --- I don't drink or smoke so maybe it's just you -- Baahahaha.
CO

I don’t drink or smoke either, just a straight edge old guy.lol