New Expansion Chamber Theory

[Fabian]

That would be the ultimate in data acquisition for verification expansion chamber theory and design : pressure transducer data correlated to port timing, ignition timing and crank angle movement.

Jaguar, it looks like you are going to have to create a very special test bench with a working engine and data acquisition for your expansion chamber designs.
It would give some fabulous data to look at, and maybe some surprises too...

 

[Deleted member 12676]

Without it many people are going to remain unconvinced that my "new" system of computation is in harmony with reality. I know I need to do it.

 

[BigBlue]

I found a great program, but unfortunately it is for 4 stroke, multiple cylinder engines. Too bad couldn't have one for 2 stroke single cylinder engines. You can view the manual on-line and see the power of the program for $40.00. It's written in .NET Framework 3.5

http://driveabilityguys.com/Software.html

Chris
AKA: BigBlue

 

[mikejeffries]

TESTING EQUIPMENT - Just a stoner thought... when big blue mentioned pressure transducer... have u ever seen a home made tactile transducer?? Basically a subwoofer driver with the cone removed and u attach the voice coil / former assembly to its own frame and mount the frame to whatever u want to shake. (I made my own variation). But nonetheless, can you not mount a some sort of shield to the former assembly (cylindrical support for voice coil wire held in place by the spider (corrugated suspension)) to receive the pulses, and simply wire the speaker as usual, and use audio recording software to view the waveforms. Now you could also hook up the magneto to the speaker as these electronic waves normally only melt the tweeters, and would show up as distinct forms in the recording software..., thus essentially as Fabian said "That would be the ultimate in data acquisition for verification expansion chamber theory and design : pressure transducer data correlated to port timing, ignition timing and crank angle movement." But with free equipment.
I may be way off here, but in theory, wouldn't it work -- Like a heavy duty microphone. If i can figure out how to post this pic I took of the beginnings of a tactile transducer I made last year, its just a matter of installing the receiving shield -- the regular cone would melt, but something ingeniously conceived could be made The sub I used was a car audio sub -- they can take punishment, have formers that are heat rated as often get very hot, and a vented pole piece (could use that part for extra cooling). Just a thought.

 

[BigBlue]

O.K., may have found some information that might be useful to those that want to conduct some research on their own. Found this University project on combustion data acquisition and chamber analysis. I've also found the website where you can download the software.
http://catool.org/files/FinalProjectReport.pdf
http://www.catool.org/

Here's the stand alone version @ $2000:
http://xarin.com/

Good Luck,

Chris
AKA: BigBlue

 

[Old Bob]

TESTING EQUIPMENT - Just a stoner thought... when big blue mentioned pressure transducer... have u ever seen a home made tactile transducer?? Basically a subwoofer driver with the cone removed and u attach the voice coil / former assembly to its own frame and mount the frame to whatever u want to shake. (I made my own variation). But nonetheless, can you not mount a some sort of shield to the former assembly (cylindrical support for voice coil wire held in place by the spider (corrugated suspension)) to receive the pulses, and simply wire the speaker as usual, and use audio recording software to view the waveforms. Now you could also hook up the magneto to the speaker as these electronic waves normally only melt the tweeters, and would show up as distinct forms in the recording software..., thus essentially as Fabian said "That would be the ultimate in data acquisition for verification expansion chamber theory and design : pressure transducer data correlated to port timing, ignition timing and crank angle movement." But with free equipment.
I may be way off here, but in theory, wouldn't it work -- Like a heavy duty microphone. If i can figure out how to post this pic I took of the beginnings of a tactile transducer I made last year, its just a matter of installing the receiving shield -- the regular cone would melt, but something ingeniously conceived could be made The sub I used was a car audio sub -- they can take punishment, have formers that are heat rated as often get very hot, and a vented pole piece (could use that part for extra cooling). Just a thought.View attachment 47214

nice idea but to be effective you need to gather pressure pulse data for 360 degrees on a two stroke and 720 on a four stroke. ideally the frequency of data aquisition would equal to 1 degree of crank rotation at WOT.

 

[Deleted member 12676]

An exhaust sensor with analyzer (a kind of oscilloscope) is $1025 from TFX (tfxengine.com).
the DIY sensor recommended before was not something tried on a 2 stroke reving over 8000rpm. I doubt that anything other than this official equipment would do.

 

[Fabian]

Ok, $1025 might seem expensive, but like all good exuipment, once you have it, you have it for life. In two years time from now, you won't even think about the price tag.

Jaguar, you need to get this device and build a dyno to make a proper test bed; validating your theories with real world results from precision data acquisition equipment.

I for one would be most eager to look at the data from the results of materials and design experimentation.

 

[BigBlue]

Here's a website that provides the information to build a inertia dyno for small engines:
http://www.tdkmotorsports.com/

Here's a SAE paper from Gordon Blair on inertia dynos for 2 strokes:
http://www.not2fast.com/engine/dyno-blair.pdf

Here's a dyno data logging system for inertia dynos:
http://performancetrends.com/dtm-dyno.htm
Prices start at $499>

Good Luck,

Chris
AKA: BigBlue

 

[Deleted member 12676]

Since expansion chamber analysis is just a hobby I can't really justify such a big cost.