DIR Return Create A Forum - Home
---------------------------------------------------------
Chainsaw Repair
HTML https://chainsawrepair.createaforum.com
---------------------------------------------------------
*****************************************************
DIR Return to: How To Basics and Fixes
*****************************************************
#Post#: 58520--------------------------------------------------
crankcase vol. (no drilling involved)
By: 1manband Date: June 4, 2015, 8:44 pm
---------------------------------------------------------
jonsereds 52
first 1/2 of photos.....crankcase volume at BDC.
2nd 1/2 of photos........crankcase volume at TDC.
#Post#: 58521--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: 1manband Date: June 4, 2015, 8:48 pm
---------------------------------------------------------
/
#Post#: 58522--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: 1manband Date: June 4, 2015, 8:51 pm
---------------------------------------------------------
/
#Post#: 58523--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: aclarke Date: June 4, 2015, 9:57 pm
---------------------------------------------------------
Super cool. Thanks for sharing!
#Post#: 58524--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: aclarke Date: June 4, 2015, 10:12 pm
---------------------------------------------------------
1.4 to 1.50 would be a common ratio on cr125 or other modern
dirt bikes. The tz250 GP bike is around 1.4 as well. Interesting
#Post#: 58525--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: 1manband Date: June 5, 2015, 4:32 am
---------------------------------------------------------
...looking at it again this morning.......made couple of
errors.. at BDC, there is 5cc more volume of goop. another
error i found was forgetting to subtract out about an inch and a
half of connecting rod volume....possibly a few cc's.
will correct this. don't see the end result changing much at
all, even if i fix these errors.
....thought it would be a lower ratio, too.
#Post#: 58532--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: aclarke Date: June 5, 2015, 8:49 am
---------------------------------------------------------
So the 1.85 ratio represents a smaller case volume vs the bike
motors? (1.4 ratio)
I'm assuming the bigger ratio would equate to higher crankcase
pressure and result in moving more fuel/air per time unit than
the larger case bike motors.
I'm wondering how this plays into the bike T/A graphs and if
they are co pletely skewed towards the bike motors with their
different crankcase volume/ratio?
End result COULD be equal if you have a small motor moving air
faster for less duration vs. The large motor moving air a bit
slower for LONGER duration but I'm not sure the Blair Jennings
data works this way or there are losses from moving the fuel air
at higher pressures. (Perhaps more short circuiting)
#Post#: 58570--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: 1manband Date: June 5, 2015, 9:06 pm
---------------------------------------------------------
...and this would help to explain the 'time' element being off.
want to look at few other things that go along with this as
well.
#Post#: 58579--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: 1manband Date: June 6, 2015, 5:12 am
---------------------------------------------------------
the two corrections up-thread:
Total BDC volume = 94 - 40 + 18 +21 = 93 cc
Total TDC volume = 21 + 48.4 + 94 - conn rod vol 1.2cc = 164.6
cc
ratio: 164.6/93 = 1.76
1.76:1
#Post#: 58583--------------------------------------------------
Re: crankcase vol. (no drilling involved)
By: 1manband Date: June 6, 2015, 7:18 am
---------------------------------------------------------
one of the things which i was looking for by doing this, was how
much air/fuel mix volume was moving in per single rpm.
estimate (based on crankcase volume, ratio, and motor
displacement): approximately 14.6 cc total per rpm.
not much. hahaha.
previously.....cc'd the transfers they were approx. 4cc each.
........not really within the scope of this discussion but
interesting to me at least.
edit: adding reference. blair page 392. top of page.
*****************************************************
DIR Next Page