MH's ideal coil and voltage question

[MileHigh]

Dear MileHigh.

For some strange reason I still cannot " quote reply " it comes back with page unavailable.

I wasn't actually referring to car engines but more to the " Stationary " engine side where the fixed RPM creates a fixed frequency. By tuning the exhaust pipe correctly the expanding gasses can actually scavenge the combustion chamber reducing the effort required on the intake side.

I have attached a couple of references to exhaust tuning and I got a surprise to read that Ferrari are employing tuned extractor manifolds on their V 10 engine.

http://www.endtuning.com/exhaustsystems/

https://en.wikipedia.org/wiki/Tuned_exhaust

Cheers Grum.

Okay I going to pull the key quote from the first link for starters.

<<<  pipes can be thought of like an Organ pipe. For each diameter and length, there is a resonant frequency, in the same way Organ pipes are different sizes and diameters to produce different notes.
Exhaust tuning uses this resonance to help evacuate the gasses from the cylinders.
This is the main point.
A finely tuned exhaust not only reduces the back pressure to minimal levels, it can actually pull the gasses out of the cylinders!
When correctly designed, the exhaust can be tuned to resonate and the pressure vibrations in the exhaust can be timed to have a low pressure wave arrive at an exhaust valve as it opens, pulling the gasses out.  >>>

I am not going to pretend that I am an expert on this stuff but let me tell you what I think.

An organ pipe is basically a big whistle.  Here is a clip explaining how a whistle or organ pipe works and how to make one:

https://www.youtube.com/watch?v=z8uwLv3s9w8

Okay for starters, exhaust pipes don't really act like whistles or organ pipes.  So the comparison being made is incredibly weak at best.

In the description they are describing an exhaust pipe that helps scavenge the cylinder of exhaust gasses.  This is done with an exhaust pipe with no chamber, just a straight pipe.  Under those circumstances you get a reflection at the open end of the pipe that travels back up the pipe to the cylinder as a negative pressure wave.  When the wave front of the negative pressure wave reaches the cylinder that will help scavenge the exhaust gasses out of the cylinder.

What you are looking at here is what I already covered with Brad, but this time it is for a negative-pressure reflected wave, and not a positive-pressure reflected wave.

That means that the exhaust pipe is not resonating at all, rather, it is acting like a time delay device to synchronize the returning negative pressure wave with the scavenging of exhaust gasses out of the cylinder.

Since it is a timing delay device, and the engine has a repetition rate for the firing and exhausting of gasses from the cylinder, there is an optimum frequency for the engine, or a near-optimal frequency range for the engine for increased performance.

Does adjusting the length of the exhaust pipe change the optimum engine RPM for the effect?  Of course it does, because you are changing the amount of time delay for the arrival of the negative pressure wave, but this is not resonance.

So, my conclusion for the first link is that they are just using non-scientific marketing/shop talk when they talk about tuning the exhaust pipe for "resonance."  There is nothing actually resonating in the pipe.  Rather, it is acting like a short sound echo chamber.

I have no issue if you refer to this as "resonance" in your vernacular when working on engine exhausts, but relative to the true scientific and engineering definition for resonance, the exhaust pipe is not acting like a resonator.  That's in contrast to a pipe organ or a whistle, where the tube is acting like a resonator and kinetic and potential energy is resonating back and forth in a standing sound wave inside the tube.

It's all about truly understanding what is happening in the exhaust pipe and not just throwing a cool-sounding word at the process.

I will now review the second link.

MileHigh

[MileHigh]

Grum:

Now for your second link.

The first sentence:

<<< A tuned exhaust system is an exhaust system for an internal combustion engine which improves its efficiency by using precise geometry to reflect the pressure waves from the exhaust valve or port back to the valve or port at a particular time in the cycle.  >>>

That seems sum it up nicely and is basically what I just said in my previous posting.  This is not resonance.

<<<  In a two-stroke engine, tuned expansion chambers are used to reduce loss of the new charge caused by late closing of the exhaust port by delivering a pulse of positive pressure after the exhaust gases have left the cylinder.

In a four-stroke engine, tuned extractor manifolds are used to promote scavenging of the exhaust gases by delivering a pulse of negative pressure just before the exhaust valve closes.  >>>

Again, we are talking about synchronizing fixed-delay timing events to a certain engine RPM.  This is not resonance and we are not going to have any resonance monkeyshines talk from the resonance fanbois.

It's quite impressive how the exhaust system designers came to the revelation in the 1950s to use geometry and reflected sound waves to their advantage when before that it was probably not even something that was considered.

In summary, both of your links do not show any evidence of true resonance being used in an ICE.  At the same time, who am I to change the common vernacular used by ICE enthusiasts when talking about engines and engine exhaust systems.  Just keep in mind that even if you may use the word, it is not true resonance and this thread and some related threads are about true resonance.

A ringing wine glass is an example of true resonance, a tuned exhaust system is not.

MileHigh

[ramset]

Obeewannabee
Your tune is not resonating with reality ,in addition to Many,  many other factors in ICE design  the speed of sound is most relevant ... to remove resonant tuning and replace it with some purely semantic word salad and declare it as fact and not relevant to resonance is

at the very least ignorance ..
and while we're on the topic of your ignorant semantic rants...
they are 99.9 percent semantic

.099 % substance
and .001% useful on Brads bench whilst he tunes for resonance

[MileHigh]

Obeewannabee
Your tune is not resonating with reality ,in addition to Many,  many other factors in ICE design  the speed of sound is most relevant ... to remove resonant tuning and replace it with some purely semantic word salad and declare it as fact and not relevant to resonance is

at the very least ignorance ..
and while we're on the topic of your ignorant semantic rants...
they are 99.9 percent semantic

.099 % substance
and .001% useful on Brads bench whilst he tunes for resonance

No technical rebuttal, just a bunch of sore loser BS.

[ramset]

Oh
the aforementioned  .001% non semantic "useful" contribution on Brads bench

purely for humor as he giggles about your  useless semantic contributions on his real world bench.

If you had posted the material that smokey had posted and its relevance to NMR , NAR and LENR
perhaps it would have been useful to an OU experimenter on his bench

Your  semantic Diatribes regarding resonance are of no use whatsoever to Brad.
they do seem to be very important to you ...

and your "Whine" glass !!