Chainsaw Repair
How To Basics - Carb Fixes + Mods - IPL and Service Manuals => How To Basics and Fixes => Topic started by: 1manband on March 22, 2016, 04:11:43 pm
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looking at the some of the papers, many state there is benefit to fooling with lengths, x-sect areas and volumes.
hope to get into some different ways to figure this out.
i enjoy working design numbers if y'all haven't noticed.
maybe just more of my digital garbage, don't yet know myself. number/graph phobia folks........shield your eyes! hahaha.
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ok, this is the science end of it.
screenshot shows the idea.
frequency is expressed as "Hz" and is how many waves pass by the same location point in one second.
think about it as a piston moves up and down in the cylinder. as rpms increase, piston moves more times per second, same idea as waves and Hz.
everything i do in the thread will be done with references.
before anybody says....."but there is a transfer port too." "what about that?"
in a paper on delivery ratio, by komatori and watanabe....they state that the intake is not affected by the previous cycle......page 11.
paraphrasing their words not mine. and that's how the rest of my blabber will be written whether i agree with it or not.
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above reference was from georgia state university. great site. search >sound waves>resonance>cavity resonance ......and you will find it.
plodding along, some motor books and magizines and other things use this formula to find resonance in intakes and such.
the delivery ratio paper i noted for 2 strokes uses this as well.
cool feature on the georgia state U site, it can calculate all this for you if you just plug in your motor measurements. it also has a temperature correction feature if you decide to add that in as well. just make sure you use the same units of measure.
since i am using the paper, if you plug in the values they list on page 11.......you will also find out that they made a boo boo. enough about that. <edit: will look into that again, has got to be something i missed.>
paper is great info.
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more in a bit.
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that GSU calculator is cool.
couple of things that i ran into, that may save some time.
just a note, to help if you use the online tool.
in the paper, they use the 'mean' crankcase volume. this is the BDC volume of the crankcase + 1/2 the swept volume.
if you do this by hand......
from the paper they use, c = 1100 ft/second. if you work it out by a handheld calculator, use 13200 inches/second to match the other units, or the answer will come out wrong.
next will work out a chainsaw motor to see what it is.
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jonsereds 52......this motor never stops amazing me. good stuff.<<<edit: not as good as i thought.>>
hits twice.<<<<<edit: just once>>
<edit> after warning you guys to watch the units, i did not. plugged in 118.5 cc's for case volume, it should have been in cubic inches... 7.23 in3
changed the screenshot to reflect this.
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So what do most chainsaw engines require. Are the intakes close in length and port opening to be efficient as they come stock or would adding length to an intake help with the resonate frequency or opening of the port. Also when you port a saw that is showing RPM's of 9000 in the cut, and because the larger port has now dropped the resonate frequency does this come closer to that 9000 rpm or further away from it.
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So what do most chainsaw engines require. Are the intakes close in length and port opening to be efficient as they come stock or would adding length to an intake help with the resonate frequency or opening of the port. Also when you port a saw that is showing RPM's of 9000 in the cut, and because the larger port has now dropped the resonate frequency does this come closer to that 9000 rpm or further away from it.
take another look at the screenshot roger. i fixed an error. i got a little wowed by the previous erroneous result.
what would be ideal is have the motor work like the way those two guys explain. waves have peaks and valleys. thing, or goal would be to get the peaks and valleys of the waves to do what you want at a certain rpm. both the intake and transfer ports need different things to work well. during the initial portion of the open duration of the intake port (when port just starts to open), a big valley is good. during the latter portion, of the transfer duration phase (just before it closes), a peak is good.
if the peaks and valleys happen at the wrong time, they do not help. to make things worse for tuning is that the "goal" is a moving target because it changes with rpm.
in the paper, they have some ....lots of graphs. the page that explains this better than i ever will is page 11. the graph shows what is good and bad, with changing rpm. tomorrow will put some notes on it, hope it will help. once you see it, you will see it.
****<<<EDIT......this is wrong>>> IMO......in order for any of this resonant tuning to really help, it needs to be within the actual rpm range the motor can spin at. the 'natural frequency'......the one i called RPM at Hz is really the one that needs to be within this rpm range. END of IMO.<<<<Do not listen to my drivel!!!! *****
looking at the first 'science' screenshot......as far as porting is involved with this kind of thing.....a bigger hole makes the frequency Hz value change.
then, looking at my corrected screenshot......those frequencies are really up there. for example.....300 Hz = 18,000 RPM......not sure quite yet if they will make a difference. (in my erroneous screenshot, an 118.5 cubic inch would be fine for a chainsaw motor rpm range). will have to run some numbers, have not got quite that far yet. yes indeed sir, good questions.....
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some links for reference information i am using so far:
1. georgia state university resonance and online calcs.: http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
2. delivery ratio by K&W: http://www.vintagesnow.com/SledU_Folder/delivery_ratio-1.pdf
3. delivery ratio by N&S: http://vintagesnow.com/SledU_Folder/33u5gnr3.pdf
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side note: the intake/crankcase res formula, much like exhaust formulas, are based on sound waves. through experiments, folks found that they approximate physical testing of pressure waves.
sidetrack to some pressure things. intake-crankcase tuning is interrelated to porting. since the size of the hole also affects the intake/crankcase Hz. this helps show what is ideal.
interesting thing at transfer port just close at higher rpm.
from reference #2 below.
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learning as i go.
this is from a paper called "Surge Phenomena in Engine Scavenging" by Helmuth William Engelman (thesis).
probably the best paper on this topic. 64 pages worth.
sorry, i do not have a link, too big to post, maybe i could split it up somehow and post?
self explanatory. range from about 1.95 to about 2.14.
now to plug in some numbers and see.
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one thing you need to find first is Hz from RPM,
so, just divide motor RPM by 60. done.
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there is no mention of any of this in reference #2 K&W delivery ratio paper i was using.... just leaves you hanging after they post the formula.
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tried out a few different values in the formula.
easy to make them fall within the motor's rpm range. looks like it can be of value.
this is the most basic of all resonance formulas.
will work out different formulas which look like they may give more accurate results.
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side note: the intake/crankcase res formula, much like exhaust formulas, are based on sound waves. through experiments, folks found that they approximate physical testing of pressure waves.
sidetrack to some pressure things. intake-crankcase tuning is interrelated to porting. since the size of the hole also affects the intake/crankcase Hz. this helps show what is ideal.
interesting thing at transfer port just close at higher rpm.
from reference #2 below.
......i see nobody caught my drift on the interesting comment?......will be back, have to draw something.
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The drift I am seeing is that the larger the port and the longer the intake the lower the resonant frequency and it appears to me that it tends to come more in line with what your average chainsaw is going to turn in rpm's. I am not good at all the math so I was more interested in a rule of thumb and this is what I seem to understand so far. According to your last chart that is what appears to me.
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side note: the intake/crankcase res formula, much like exhaust formulas, are based on sound waves. through experiments, folks found that they approximate physical testing of pressure waves.
sidetrack to some pressure things. intake-crankcase tuning is interrelated to porting. since the size of the hole also affects the intake/crankcase Hz. this helps show what is ideal.
interesting thing at transfer port just close at higher rpm.
from reference #2 below.
......i see nobody caught my drift on the interesting comment?......will be back, have to draw something.
Are you referring to the sound waves and pressure waves being similar to one another.
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The drift I am seeing is that the larger the port and the longer the intake the lower the resonant frequency and it appears to me that it tends to come more in line with what your average chainsaw is going to turn in rpm's. I am not good at all the math so I was more interested in a rule of thumb and this is what I seem to understand so far. According to your last chart that is what appears to me.
not sure of a rule of thumb yet, you are right on with the concept.
but to me, the interesting thing was a couple of different things.
the graphs are showing the pressures within the crankcase.
the author's stated that for maximum delivery ratio at a higher rpm:
a lower Pressure is more favorable for increasing DR at Transfer port close. @t6 rpm, on the graph this condition was met.
however, again for maximum DR, they say that a higher crankcase pressure is favorable at intake port close.
this condition was not met on the graph. it does happen though, at quite a higher rpm.
so, my head scratcher was, at what rpm is this happening at where both conditions are met?
drew some things on the graph to show some things. rpm is increasing, as you move down the page.
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side note: the intake/crankcase res formula, much like exhaust formulas, are based on sound waves. through experiments, folks found that they approximate physical testing of pressure waves.
sidetrack to some pressure things. intake-crankcase tuning is interrelated to porting. since the size of the hole also affects the intake/crankcase Hz. this helps show what is ideal.
interesting thing at transfer port just close at higher rpm.
from reference #2 below.
......i see nobody caught my drift on the interesting comment?......will be back, have to draw something.
Are you referring to the sound waves and pressure waves being similar to one another.
that too.
that was my biggest head scratcher of all. the sound waves and pressure waves, are supposed be similar.
none of these crankcase pressure graphs are showing any evidence of this at all. they should be vibrating like a guitar string. and they are not.
could not figure out why. then had to read read and read some more. then i got it.
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this is what i found.
the pressure graphs of the crankcase are not showing the vibrations waves at all.
only the ports are showing them.
so, the piston gets the wave motion going, based on rpm. moves the air in the case, the air in the case then gets the waves going in the ports.
interesting thing is the intake likes about 4x the rpm, and the transfers like around 8x the rpm Hz.
for the guitar playing folks: on the open "e" string.....after pluckng......harmonics at the 12th and 24th frets.
not exactly.....would need plenty more frets actually, but similar idea.
i like to know the "why" i guess......hahahaha.
screens are showing about 9500+ rpm
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........and when you get the resonance thing going good........
picture the graph on the bottom of this link.......doing that in the intake and transfers.......!!!
link here: http://newt.phys.unsw.edu.au/jw/Helmholtz.html
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i will post up the basic res program up in a bit. it varies a slight bit from what was presented in the K&W paper, because i not not going to spend 3 hours
working out the difference in case volume between 90 and 120 degrees for this in a program, nobody is going to use anyway.
there are no motor secrets. all this kind of thing was figured out 30 to 60 years ago.
(it is not a big difference at all, you will find this out when you plug in differing volume values).
side note: it will help to approximately determine a case size for rpm.
imagine, that it would get folks close enough, but just like exhaust, would need some cut and try....just like every exhaust formula i have tried,
there is not pressure variable within the formula, and approximated by sound waves.
think some other formulas that make corrections and such would get closer with less cut and try. will be looking into that shortly.
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just trying to unravel some things i have interest in.
hope it helps.
tiny program below. save first, then extract, then should be ok for use.
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link to 64 page scavenging/helmholtz paper by engelman. i mentioned before. long intensive read. about page 50 or so.
4. engelman http://minds.wisconsin.edu/handle/1793/396?show=full
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Just so happens I am a guitar player. I do find this all very interesting but it is more about the theory for me than the math.
When I studied electronics and we were discussing resonant frequencies and showing them on a scope, I don't remember but can there be more than
one resonant frequency or as in the case of a guitar more than one harmonic. Its been 40 years since I studied that stuff.
But hey I still find it interesting to read. I do not leisure read and only like to read tech stuff.
What I was really interested in seeing was what your finding were and what effect porting a saw had on the pressure waves for the intake. To me it looks like it may help it more than hurt it.
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Just so happens I am a guitar player. I do find this all very interesting but it is more about the theory for me than the math.
When I studied electronics and we were discussing resonant frequencies and showing them on a scope, I don't remember but can there be more than
one resonant frequency or as in the case of a guitar more than one harmonic. Its been 40 years since I studied that stuff.
But hey I still find it interesting to read. I do not leisure read and only like to read tech stuff.
What I was really interested in seeing was what your finding were and what effect porting a saw had on the pressure waves for the intake. To me it looks like it may help it more than hurt it.
same here.
imo, at this point, the potential benefit of using this concept is debatable in a saw motor. i am not saying that it does not work, but that it most likely has already been incorporated in the motor when it was designed at the factory for a particular rpm.
in example, looking at my jonsereds 52. the specs i found say that maximum HP happens at 8300 rpm.
running the numbers, came up with 8900 rpm for the resonant rpm.
the formula is an approximation, also has some generalizations, not taking in temperature, heat, pressure, pipe end corrections, etc. even with all that, is roughly 600 rpm off. maybe it is a wash? don't know. not sure if this is the rpm to shoot for anyway.
would tend to think, that in order to truly maximize the potential of this concept, the porting goal would need to be made for a specific rpm in mind.
since, the intake hole size is also affecting the "tuning" of the case.
even reducing the case volume a good bit, has a small effect on the formula results like rpm for the numbers i ran.
do believe, that everything can work together to achieve the greatest benefit, and has to be balanced to work well.
i enjoy reading the tech stuff, and wondering if it can be applied to help these tiny motors. usually my interest gets the better of me, and spend time
chasing my tail or running into dead ends. but, hope folks could at least learn from my mistakes.
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during my web finding research, there is very little out there on two stroke intake tuning. for every 25 web search findings, maybe 1 or usually none in regards to 2 stroke findings. remainder for 4ST's.
it was not my focus to look into 4ST's, but did read about quite a few. i only mention this in passing.....and will suggest that some homework on these is done and the realistic rpm of daily driving scenario is considered. there is quite a boat load of information out there, and some of these setups can get pricey, at least for me anyway.
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Thanks for the info.
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looked into the looming question of intake port cross sectional area as it relates to both porting and crankcase volume.
did this by using both the time*area program and the crankcase res program.
went like this:
in the t*a program, wrote down the intake port t*a value and port area for the stock example saw. 0.00013539 sec cm2/cm3 and 0.428 in2
then, raised the stock 5500rpm (@peak tq) value by 2000 rpm. (as rpm goes up, t*a values get smaller). 0.00009928 sec cm2/cm3
so, to raise the peak torque rpm, by 2000 rpm to 7500 rpm...... you would need:
0.00013539 (-) 0.00009928 = 0.00003611 <that much more t*a
then adding that result back into the stock number:
0.00013539 + 0.00003611 = 0.00017150 <this becomes the time*area goal, to get the 2000 more rpm.
keeping the t*a rpm, at 7500, i changed durations until the t*a for the inlet port was close to 0.00017150 sec cm2/cm3.
the area of the intake port needed to get this goal t*a was 0.496 in2.
finally, (all this took all of 5 minutes), plugged the 0.496 in2 inlet port area value into the crankcase res program.....to see just how close, the rpms would be by changing areas........
<edit> added screen shot of error or difference.
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Joe,
Are the TA number above based on your modified Blair/Jennings numbers?
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Joe,
Are the TA number above based on your modified Blair/Jennings numbers?
nope. the numbers from the program posted in other thread. if i'm understanding the question correctly?
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at this point, reasonably confident that the crankcase resonant frequency is based on using the rpm of peak hp.
i cannot however, find any sources to confirm or deny the statement above.
the errors or differences between the porting area vs. the crankcase res area i found were between 560 rpm to 900 rpm off.
i do not think this is too bad, because both of these are 'design' type programs meant to get you in the wheelhouse.
happy Easter everyone.
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.....that's as close as you will ever get to seeing me do a porting thread. hahaha. how to use the program, don't have issue w/that.
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what i used to quickly hitt the areas, may be unrealistic....... about 81 or so IO. and for the other about 1.25 W and 79? did not write it down.
could go back and record the numbers if need be?
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...back to intake tuning.
once the case resonance Hz is found, the next thing that can be looked into is Pulse Tuning.
as per the delivery ratio paper by Nagao & Shimamoto....page 7.....(link is up thread somewhere).
idea is to to use differing lengths and x-sectional areas of the of the intake tract to get " 3/4 of the period of pressure fluctuation coincident with the port opening period."
best pulse values are between 0.7 and 0.8, which in turn give the maximum delivery ratio.
goes like this:
(more to follow).
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stock jonsereds 52 intake pulse tuning across the rpm range+
will put some notes on the graph later.
0.7 to 0.8 is sweet spot, about 9500 to 11000 rpm.
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same stock motor w/notes
case resonance frequency = 297 Hz @ 8913 rpm
approx. max tq rpm = 5500
actual max. HP rpm = 8300
maximum motor rpm = 11400
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now to do the same thing, raising the power band up approximately 2000 rpm. don't know yet how it will match with the case res. and pulses.
will spend a bit more time on picking a realistic port x-sectional area.
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took some time to get some realistic numbers. thing is, there is not enough material there to widen the intake manifold out enough. the manifold is made of what looks like bakelite, has 6 panhead bolts holding it onto the cylinder, along with two carb bolts. the pulse port on the manifold feeds the carb, and is located very close to the perimeter of the stock hole.
so, the stock manifold hole can only be brought out to 0.820" diameter. this yields an maximum x-sectional area of 0.528 in2. that is the maximum area value, i will be using for my port mouth opening at the cylinder.
what all this means, is by using the porting program set to a max area value of 0.528 in2, looks like the most i can raise the power band is only 430 rpm while keeping the rest of the ports all balanced.
the following screenshot shows what the rpm ranges/case res rpm/pulse tuning sweet spots morphed into using the design programs formulas.
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So if you can get the saw to turn around 10K in the cut you would be at resonance?
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So if you can get the saw to turn around 10K in the cut you would be at resonance?
believe that is the case.
when i plugged in the value for the largest intake port area i could fit in the formula, it raised the case resonance frequency from
the stock 297 Hz @ 8913 rpm up to 329 Hz @ 9871 rpm.
the rpms where the best pressure pulses also moved up in rpm range from the stock values as well, by about a 1000 rpm.
both instances now have breaks between them, in the stock configuration this was not the case.
looks like the resonance and the porting are not a 1 for 1 in rpm thing. interesting just how much a
area change from 0.428 in2 to 0.528 in2; and 5 degrees of duration actually makes.
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eric gorr writes how this stuff can be useful. (will post the link up when i find it again).
i am not the best explainer as y'all can already see, because i look at these thing with graphs and such.
so, by varying the length and area one could raise or lower the intake tuning just about anywhere in the rpm range and nudge power band hit around a bit.
by using a spacer, lowering the tune for more of a torque hit is possible.
1/2 inch spacer, between the carb and intake port spigot, lowers the rpm hit by 700 rpm.
1" spacer....................................................................lowers the hit by 1200 rpm.
going the other way, shaving a 1/2" off, yields about an 800 rpm raise in the intake tune.
imo, a tach or the way chrispa suggests would be necessary to get rpm readings to realize the intake tuning benefit. or, if the tach won't read on the new fangled motors. how anyone ports without a tach is beyond this discussion.
as far as the case volume thing goes, for my motor, they picked a very good volume already. don't know about others. porting raises the rpm, with not much to worry about as far as intake tuning, at least from the one example i am basing this on.
for the race crowd: looked at what only decreasing the case volume, would do on my little motor.
for every in3 reduced case volume, about +700 rpm intake tuning went up. not that much.
however, when port area was increased by about 30%, with 2 in3 less volume, rpm tune went up about 4000 rpm, max rpm up to 17.5k
eric gorr and frits overmars/jan thiel do have some interesting reads.
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Makes sense to me. The larger the volume the lower the frequency and the smaller the volume the higher the frequency. Got it.
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most all of the references on this topic explain the process, the amount of measured benefit of all this to me remains unclear.
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...found a couple of references that mentioned gains. was going to put this all behind me.
eric gorr writes that..'effect will be unmistakable, engine will pull very strongly when it comes on the (sic. intake) pipe.'
engleman paper......'effect over very broad rpm range'
gorr goes on to write that mcculloch gave him some insight on how they test for this. they affix a very short exhaust stub, to take the exhaust effects out. they then cut and try differing lengths of intake pipes, to find which work the best.
this is somewhat contradictory to what nagao & shimamoto write......'finding an intake tuning alone (without considering exhaust) may or may not be optimum when an exhaust is affixed.'
another way to test intake tuning was in the engleman paper. the lauson company, spun up a motor with a compression gauge attached to it. the tuned intake gave higher compression numbers accross the board.
would be just about impossible to spin up a saw motor to its power range?.....to use this method.
the lauson test showed about 10 psi gain minimum depending on length and area of inlet pipe tested.
.........
at this point, i am just going to get the formula more accurate by putting in a temperature and open end correction, and that is it, for less cut and try hopefully.
the motor manufacturer's most likely already incorporate intake runner tuning into their designs these days anyway for the rpms they spec out.
wondered just what would happen when the rpm range was changed with porting, etc.
have never read of a thread where someone tried working numbers out for these small high rev motors, so i thought would give it a go. is what it is.
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So then can we measure the RPM of an engine and then try different lengths of intake tube and by the using the RPM's can we then determine which one is the most beneficial for the saw. In other words is the RPM's going to be at it's highest level when the intake length is at it's most beneficial.
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i believe so.
the way the test is described for a motorcycle: equipped with both a stub exhaust and a tachometer, pointed up a hill or long road, in order to load the engine heavily, to see where the intake pipe has it's effect on power, being most prominent at a certain rpm or speed.
maybe it would be similar idea? Check ct stock length, note rpm. then check with altered length, to see what rpm it hitting hardest at.
I do not know, for certain, have never tried this.
the calculations would give an idea of what to expect before testing for rpms, using different combinations of length, area and volume. And what combos to try to move rpms around where you want to.
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found a few more bits of information.
the carb area has to be close to the inake runner x-sectional area or the intake ramming effect is diminished. a ratio of 0.7 or greater is the goal.
stock sizes: carb venturi area = 0.31 in2; intake x-sect area = 0.43 in2......so 0.31 divided by 0.43 = 0.73 works.
same carb with larger port sizing: carb = 0.31, intake area = 0.53......0.31/0.53 = 0.59 .......intake ramming diminished.
also found some saw motor temperatures from blair page 391 figure 5.25 graph.
crankcase internal temp range from 140F to 248F. average about 212F. (so, most vaporization is happening in the cylinder, not the c.case).
intake runner internal from 68F to 122F. average about 104F.
have enough info to include corrections into the formula now.
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so i worked out the formulas with some different temperatures.
quite a bit of swing when the temperature goes up.
do not know which temp would best represent or mimic real world conditions.
all these formulas use the speed of sound. but speed of sound goes up as temperature goes up. this changes things quite a bit.
nagao & shimamoto/engleman did not include a temperature correction. believe it is important to represent intake tuning as they do.
they used a speed of sound value at 68F (20C). so will include that.
will also include and use the average runner temp in a separate calc.
lastly will use what blair settled on for thermo calcs and show this. 212F (100C).
somewhere, within those temp ranges is what i believe is happening?
maybe it is like these different exhaust programs, some closer to the mark than others.
will post up what it looks like.
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......then was thinking of making up some wood spacer blocks.
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......then was thinking of making up some wood spacer blocks.
Or some small aluminum ones. A man with your talent it should be a piece of cake.
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no talent on my end. just a man who is curious how things work. took things apart as a kid to see what's inside, still do.
not much room in there for a long spacer. will try to fit the longest. carb linkage may be the hardest work around?
hope it will work.
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no talent on my end. just a man who is curious how things work. took things apart as a kid to see what's inside, still do.
not much room in there for a long spacer. will try to fit the longest. carb linkage may be the hardest work around?
hope it will work.
That is right I forgot about the carb linkage. That could be a pain in the arse.
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just a couple of screens to show just what the effect of different temperatures have.
same motor. same formula. only the case air/fuel temps are different.
the temps are always changing in the crankcase, as the motor turns through one rpm, (<from blair)
....basically between the temps i have used here.
when temps go higher.....the speed of sound gets faster......and the results change, because the formula used depends on the speed of sound. it is shown as the "C" value in the screenshot.
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thinking about ways to test. have a big log here to bury the bar.
just a chainsaw hack, don't believe i can keep a steady pressure like kevin did so well in the previous chain build-off.
to keep the down pressure the same, not sure if this will work, but was thinking of attaching a dumbbell using some muffler clamps to the handle.
have 10's, 15's and 40's.
will this work? don't want to put too much weight on to make it into clutch slippage test.
have some things to do to get the saw in working order. bend up some linkage. make some solid mounts. rubber are shot. find out what is going on with the oiler.
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It should make for some interesting testing.
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derailed with some other things. original electric motor was throwing sparks. mounted a too small spare motor to turn the armature down.
also managed to break both brushes. after the third time dressing the brushes, putting the motor back together, etc.....and cleaning carbon dust off the commutator, too much thinking juice helped the blunder of not compressing the springs on the brushes, before placing the end cover on. oh well.
but, did get a handlebar mount made using the small motor.
looks like i can make an adapter block to fit a short straight pipe off my strunk saw.
oiler is a no-go.
went to two hardware stores today to find longer carb mounting bolts. the dang things are metric. m5 0.8 thread.
could not find them any longer than the stock 2" (50mm) length. need a couple of 2-1/2 inch and 3 inch long. will check another place tomorrow. if i have to, will weld a couple together. no-one so far around here sells metric threaded rod.
no hurry on my end. but curiosity has got the best of me.
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Maybe you could find some threaded rod or something long enough on line. That is what I do when I cannot find some local.
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some slow progress.
made a good template and roughed out a thing or two.
next, have to find a wiring diagram to rewire a small westinghouse fht to be able to spin in the other direction.
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finished the intake blocks. nothing fancy. 2 part mix used to fill some chips.
old 3/4" reamer, just happens to be the intake bore. lucky.
older yet? choke kit found laying around. package says something about a 1954 stromberg carby......hahahaha. hope to use it for thumb drive carb linkage, who knows if it will work.
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...some more slow progress.
linkage is just about sorted out.
it has to be able to work both with and without the blocks.
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Still Watching.
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Still Watching.
......kind of like watching paint dry. hahaha.
just ran some numbers on the wood. looking at just over a 1000 rpm drop with all three. (wood blocks are just about 1/3 inch each).
was hoping to get the numbers to hit more into the saws stock powerband. if torque peak rpm drops by a grand......? don't know .....
if by some wild crazy chance it actually does, would tend to think that it would validate the formula estimate. cut and try comes to mind.
getting way ahead of myself at this point, and not sure if any of this rpm will actually be measurable anyway. just an experiment.
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2 weeks later......just 2 bolts.
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snails pace. getting closer.
happened to get some bits together and clearance fit the linkage.
freed the ring, cleaned groove out. 2nd ring broke on removal.
last shot is hard rubber bushing made. the stock soft bushings feel like harley handle bar riser bushings. maybe some like them, not i.
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got it together a couple days ago.
10 pulls on each shoulder is all i can muster with my rotator cuffs. short rope on these.
will give it a go tomorrow to fire.