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#Post#: 59987--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: EHP Date: July 28, 2015, 9:22 pm
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alot of it is BS mainly because its impossible to reach the
amount that is claimed it can do , its all just theory but its a
dam good place to start figuring . Biggest thing is the parts
cannot stand that pressure if you can get enough fuel to it ,
bike engines are far better built to start with than a chainsaw
so the crank can stand alot more pressure . One thing that had
my mind working was at 1.20 to 1 ratio on the computer dyno in
the TSR program it showed almost double the hp compared to 1.47
to 1 but was going to burn pretty much 2 -1/4 fuel lines of
alcohol/ nitro to keep it running so way more fuel than what a
single carb could produce
#Post#: 59990--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: 1manband Date: July 29, 2015, 4:51 am
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i'm with you ehp. the bike thread was based on reed block
motors. pipe has huge effect.
my program does not account for crankcase volumes as of yet, but
it will in the future. when i worked the numbers with the
calculator, for a piston ported/box muff motors.....only saw
about a 5% increase in fuel charge entering the crankcase when
just the volume was changed, depending on rpm.
have not estimated a pipe motor with numbers. not really an
interest of mine.
#Post#: 60002--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: 1manband Date: July 29, 2015, 2:43 pm
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found it again, link here:
HTML http://www.pit-lane.biz/t117p320-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-1-locked
#Post#: 67855--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: EvilRoySlade Date: January 8, 2016, 3:07 pm
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Please help me understand the putty. Is it the volume underneath
the piston? I believe you could get accurate volume at bdc
without the putty but then there is no way to measure the
underside of the piston at tdc correct? Unless you did this
with cylinder on which is the no drilling thing, drill the
piston to let air out I assume? I have so many questions.
#Post#: 67859--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: Chris-PA Date: January 8, 2016, 6:16 pm
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Interesting thread that I had not seen and need to read more
carefully. I'm still confused as to the definition of crankcase
volume and exactly what volume this includes. Does it include
the volume under the piston? Everything under the piston at
BDC? Is transfer volume included?
Then there is the question of what volume is this being compared
to - it makes sense to me to compare it to displacement, but
ratios will of course be different if a different denominator is
used.
#Post#: 69013--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: 1manband Date: February 6, 2016, 7:09 am
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[quote author=EvilRoySlade link=topic=4974.msg67855#msg67855
date=1452287252]
Please help me understand the putty. Is it the volume underneath
the piston? I believe you could get accurate volume at bdc
without the putty but then there is no way to measure the
underside of the piston at tdc correct? Unless you did this
with cylinder on which is the no drilling thing, drill the
piston to let air out I assume? I have so many questions.
[/quote]
yes, the only reason for the putty is to help find the volume on
the underside of the piston itself, when it is at BDC.
yes.
the last one, yes, kind of the idea....but it is not really just
to let the air out. maybe the following will help to picture
it using the "drill the hole in the piston crown method."
to get BDC case volume: with cylinder removed, piston at BDC.
seal the piston skirt to the case deck with heavy grease. fill
the case and underside of piston with a measured amount of oil
via the drilled hole. done.
one could measure the oil being put in there with a syringe and
a length of tubing.......(buret or graduated cylinder would work
too).
the reason for the putty, is just to do all this without
trashing a piston. not really a big deal, but it you are using
'one off' custom stuff, this can get expensive in a hurry.
the volume of under the piston is an additional portion of the
case volume. like in the first photo shown in this thread, the
entire piston does not disappear below the case deck at BDC, so
the volume of the piston that is above the case deck has to be
measured some way is all.
hope it helps.
i will clean up the thread a bit.
reducing the case volume, can gain some rpms. hope to show just
how many as well.
#Post#: 69015--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: 1manband Date: February 6, 2016, 8:52 am
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[quote author=Chris-PA link=topic=4974.msg67859#msg67859
date=1452298572]
Interesting thread that I had not seen and need to read more
carefully. I'm still confused as to the definition of crankcase
volume and exactly what volume this includes. Does it include
the volume under the piston? Everything under the piston at
BDC? Is transfer volume included?
Then there is the question of what volume is this being compared
to - it makes sense to me to compare it to displacement, but
ratios will of course be different if a different denominator is
used.
[/quote]
just volume at TDC divided by volume at BDC. some don't include
the transfer port volumes, some do.
the volume under the piston is included at BDC. the volume
under the piston is included at TDC as well.
without transfer ports volume included:
case volume @ TDC = 200 cc
case volume @ BDC = 100 cc
so, the case volume ratio = 200/100 = 2.00
--------------
with transfer ports volume included:
say, motor has only 2 trans ports, each trans port measured out
at 5cc each. so, 10cc total trans volume.
case volume @ TDC = 200 cc + 10 cc = 210 cc
case volume @ BDC = 100 cc + 10 cc = 110 cc
then, case volume ratio becomes = 210/110 = 1.91
------------
the difference in ratios is 0.09
rounding it off = 0.10
up to you, to decide whether to include them or not.
.....the folks who got the ball rolling on this case volume
thing as referenced by the article linked in the thread,
calculated the ratio differently.
#Post#: 69203--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: EvilRoySlade Date: February 11, 2016, 2:04 pm
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Thanks for the reply. Life threw me a wild pitch that hit me, so
my saw play time has dropped huge amounts. When I get back on my
feet I'm going to check a few for fun.
Sent from my iPhone using Tapatalk
#Post#: 69262--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: 1manband Date: February 13, 2016, 4:23 am
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[quote author=EvilRoySlade link=topic=4974.msg69203#msg69203
date=1455221053]
Thanks for the reply. Life threw me a wild pitch that hit me, so
my saw play time has dropped huge amounts. When I get back on my
feet I'm going to check a few for fun.
Sent from my iPhone using Tapatalk
[/quote]
..sometimes life = dodge-ball game, with multiple hits to the
cranium and testes. eventually the swelling goes down.
vegetable oil leaves a sticky film that needs to be cleaned
using a brush. think that something like transmission fluid
would be better thing to use instead. easier to flush out, and
better for the seals.
will you be drilling?
#Post#: 69270--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: Chris-PA Date: February 13, 2016, 11:58 am
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This is a topic that interests me - I've been reading that
people believe that the case volume can be too small and that
this will hurt performance, but I do not see the logic in that.
The swept volume of the case will always be the same on both
sides of the piston, so there must always be "enough" volume.
The only thing I can think of is that a full circle crank might
block flow to the transfer entrances, but otherwise I can't see
the problem with reducing case volume. It seems like less
should always be better.
When drawing mix into the case you can have at best one
atmosphere of pressure to push it in, and any extra volume just
reduces that pressure differential and makes for less efficient
pumping. When pushing mix up the transfers you can generate
much more pressure, but initially must push against the residual
combustion pressure in the cylinder.
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