author=sm0ky2 link=topic=8341.msg479089#msg479089 date=1459410978]
while this is interesting and all, History seems to side with Milehigh on this one.
No one was arguing with MH that some !!some!! resonant factors within the ICE can give a negative value to efficiencies.
But how is it that MH can state !once again! that Quote:
But the actual engine itself, the pistons, the valves, the camshaft, the crankcase, the ignition, etc, has absolutely nothing whatsoever to do with resonance.,and then place some sort of valid argument that these resonances can cause negative effects,when he also states they are not here to begin with
one of the functions of the muffler/cat is to restrict flow to prevent resonance.
full resonance resulted in a violent 'sputtering' of the exhaust
while half-wave created a vacuum in the exhaust manifold that decreased the overall power of the engine.
or even back-firing
cars that remove these components can sometimes experience this.
This is totally incorrect.
The muffler is only designed to reduce the noise level of the exhaust-and nothing more.
Hi performance muffler's were designed so as to reduce noise level's,while providing the least restrictive exhaust flow.
The cat converter is only there to reduce harmful emissions produced by the burnt fuel-and nothing more.
I have been building high performance engines for over 30 year's,and we always design the exhaust systems to be as free flowing as possible. As soon as you add back pressure to the exaust gasses,the engine it self then has to push these gasses out,and that exerts a pressure on the pistons,and thus reduces the HP of the engine.
If you think about the frequency of the explosions,
with respect to the volume of gas exiting during the exhaust part of the cycle
and the volume of tube this gas will occupy during the amount of time before the next gush comes out.
a resonance in this volume of the pipe will do nothing good for the engine cycle,
because it is post-exhaust.
This is also absolutely incorrect.
The two stroke engine relies on resonance in the exhausts expansion chamber,to ensure a total evacuation of the burnt fuel/gas mix from the cylinder,and to draw part of the fresh charge from the crank case,into the expansion chamber,where the returning pressure wave inside the expansion chamber then pushes this new part of fresh charge back into the cylinder at the precise time the piston is about to close the exhaust port.
For the 4 stoke engine,it is as i said in my previous reply--the less the restriction,the more efficient the engine will be.
It is possible to tune the exhaust pipe length for each cylinder,so as the next exhaust cycle is sucked out by the previous exhaust gas charge that has now cooled and contracted. This creates a vacuum in the tube,and it is that vacuum that draws out the new charge of exhaust gas. This creates a situation now where the piston it self is not what pushes the exhaust gases out. These tuned lengths of exhaust pipe's -some people will know them--there called extractor's.--> If you want to increase the efficiency of your car,then you fit extractors-or header's,which are a more compact system,but not as efficient as extractors.
So any restriction on an exhaust system only results in a loss of power,as your pistons have now become compressors,and this reduces the HP of your engine,as well as overall efficiency.
It can either evacuate the chamber very quickly, or it can restrict such from occurring.
If either of these conditions exceed engine tolerances, it causes problems.
The very thing you!do! want to do,is evacuate the burnt gases from the cylinder as fast as you can in any ICE,when it is on it's exhaust stroke. There is no need at all to keep hot,burnt gases inside the engines cylinder. This would only increase the engines temperature,and that results in an efficiency decrease--a hot engine is not a happy engine.
Resonance may help push the exhaust out the end of the tailpipe, and I guess in some abstract way it can help
with propulsion (pulsejet?)
but I would hardly consider that to be an "efficiency gain", when considering the eventual replacement
of rubber mounts, and weld-points.
I have no idea as to what replacing consumable parts has to do with engine efficiencies.
Now, if we consider a resonance in the intake part of the engine,
perhaps the periodicity of pulses from the fuel pump,
with respect to the intakes of the cylinders
this could result in a decrease in restrictive flow losses from tank to engine
meaning less "load" on the fuel pump,
perhaps there is an RPM, which your fuel pump works more efficiently.
how much of the cars fuel usage is attributed to the pump? not much.....
But this does give futile credence to an ICE resonance discussion.
This also makes no sense at all,as all direct injection engine's inject there fuel into the cylinder when the compression is almost at it's highest point,and so there is no resonant state that can change the pressure the fuel system has to overcome.
If we then look at ICE's that have a gravity feed system,like most motorcycle's and stationary engine's,then there is no fuel pump load,as there is no fuel pump.
Then there is the alternator.
This operates desirably at a self resonant frequency,. the manufacturer told us so.....
can we drive at an RPM, that our alternator operates the best at?
yes, when the A/C clutch is not engaged, you can generally notice a brightening of your dash lights
within a certain RPM range.
it is usually between 2 and 3,000 or so, when the secondary coil is fully saturated, and the belt is spinning at just the right speed.
At this point smOky2,i would suggest a refresher coarse in automotive electrical system's.
Then we get to resonance in the tires/wheels....... let's not waste our time, its just Bad...
This is called wheel balancing,and has nothing to do with resonant factors until you get into large lug tires-such as mud terrain tires.
it all seems like a pointless argument, in general you don't want resonances in an ICE,
and if you did manage to achieve one that was helpful, you have to keep your vehicle at that RPM
to sustain the effect....
drive 55 Mph, and only on cold days.
you will get the best MPG 
Once again--not even close to correct.
All of todays high end performance engines rely on resonant effects that are tuned to achieve the desired result's. Those results are-high HP output,high efficiencies,and an engine that is as compact as it can be made.
It is post like this that make me angry.
We are here to present the most accurate of data,and developing system's ,in the hope of bettering our live's,and making the world a better place for our children.
The ICE is going to be here for some time yet,so the only thing we can do,is make the ICE the best we can.
So it is imperative that correct information is provided,and not some incorrect assumptions presented from some one that is not well versed in the area of the ICE.
Brad.
