Part 1 - Introduction to Two-Stroke Software
Bimotion v 2.1 - Blair S.A.E. - Dynomation 2 - MOTA v 5.0 - TSR
Using TSR Two-Stroke Software
TSR seems to have a software program for everything -
there are many individual software programs involved here.
The idea is to design each specific engine parameter as
completely as possible, then assemble the separate
components into an engine to make an outstanding finished
product. TSR doesn't pretend to be anything it's not - and
doesn't offer anything it can't deliver. The programs I
worked with are Chek_Vol, Compress, DegreeIt, Eng_Draw,
HeadVol1, HeadVol2, HeadVol3, IntArea, Layout, Newpipe,
Port2000, ReedValve, Rotary, Squish, Scrncone, TaTarget,
Velocity, Racehead, HemiFlat, Tub-Head, Rotary-2, Mikunijt,
Keihenjt, Maxspeed, Degwheel, IntakeTm, Conevol, Boostbtl
and Gearcheck. In my earlier report I eluded to noticing
that the program names are a little hard to understand. When
broken down a little bit the programs fit into categories
very well. There are 4 programs for designing overall engine
parameters - Compress, DegreeIt, DegWheel and Eng_Draw. There are 7 programs for designing cylinder heads and
working with compression - HeadVol1, HeadVol2, HeadVol3,
HemiFlat, Tub-Head, Squish and Chek_Vol (RaceHead is a model
engine program). There are 3 programs for designing cylinder ports -
Port2000, TaTarget and IntArea. There are 5 programs for designing intake systems -
ReedValve, Rotary, Rotary-2, Boostbtl and IntakeTm. There are 5 programs for designing tuned exhaust pipes -
Newpipe, Layout, Scrncone, Velocity and ConeVol. There are 2 programs for selecting correct jetting -
Mikunijt and Keihenjt, There are 2 programs for designing final gearing -
MaxSpeed and Gearcheck. Compress is a program to use to pencil in power targets
based on the compression ratio and BMEP. The program also
has another helpful output calculation - it estimates the
required octane the engine will need. When I entered the
required data I was quickly able to determine the changes in
compression and port timing I would get by adding the base
plate spacer and additional base gasket to the Blaster
engine. It also determined what the static compression would
be as well as finding the correct trapped volume to use to
arrive at the compression ratio I wanted. DegreeIt aids in engine design by revealing important
information such as the bore to stroke ratio and the rod to
stroke ratio. The Blaster test engine has a bore/stroke
ratio of 1.17 and a rod/stroke ratio of 1.93. There is an
entry field for piston pin offset. The text explains the
reasons this is done - to reduce noise and to reduce
internal wear. The focus of this program is to calculate the
maximum and instantaneous piston acceleration at the engines
maximum operating speed. The data is output at various
degrees of crankshaft rotation and distance from TDC in both
metric and English units. I entered 9000 RPM's as a peak
speed - 1000 RPM's over the peak power target. The data
showed this engine to have a peak acceleration of 101,540
ft/sec and that it was traveling at 3,366 ft./min. The peak
instantaneous acceleration of -88.352 ft./sec was achieved
at 86 degrees ATDC. DegWheel draws a colored picture of the port timing based
upon the input data. Eng_Draw displays a cut away view of the engine once the
basic parameters have been entered. It requires some unusual
measurements such as the distance from the edge of the
piston crown to the center of the wrist pin and the distance
from there to the edge of the piston skirt. From this it
reveals data which can be useful to determine absolute
boundaries when trying to establish baseline data. The
output data is all measured from the crankshaft center -
100.8 mm to the edge of the piston crown, 134.992 mm to the
top of the exhaust port, 122.286 mm to the top of the
transfer ports and 166.5 mm to TDC. Eng_Draw also runs an
animation of the engine running through one crankshaft
stroke. It shows the relation of the piston to the crank and
ports. HeadVol_1 is for designing a hemispherical combustion
chamber shape that uses a squish area radius at its
perimeter. HeadVol_2 is for designing a hemispherical
combustion chamber shape that uses a squish angle (my
choice) instead of a radius at its perimeter. HeadVol_3 will
design a tub style combustion chamber along with a squish
angle design. HemiFlat will design hemispherical combustion
chambers that can be used with flat top pistons - the squish
area is an angle. TubHead will design a tub style combustion
chamber when its used with a flat top piston - the squish
area is an angle. Chek_Vol is for outlining and dialing in the compression
components. When modeling engine components this program can
come in handy. It is a program that's the most useful when
its data input includes the actual piston dome volume - the
text at the beginning of the program outlines one way to
determine it. The input includes the volume calculated from
the thickness and diameter of the head gasket and its deck
height. It then uses the bore and stroke and the target
final compression ratio to determine the output data. I was
able to quickly determine what trapped volume I would need
to get the compression ratio I was aiming for using the
Blaster engine data. Port2000, TaTarget and IntArea are used together to
determine the final port timing and area. IntArea is for use
with piston port engines only so it won't be used on this
engine. One of the most important design parameters to know
when trying to hit a target is the current BMEP. Earlier I
determined that number to be 85 by using the formula that's
available within the program. When I was calculating it I
wondered why Port2000 doesn't have a simple to use data
entry field for the engines real horsepower and other input
variables to quickly reveal the engines BMEP. Starting with
TaTarget helps since it gives 3 choices to use as guidelines
when trying to determine ballpark figures for the engines
targeted output and RPM. The choices are to choose the
target power from a given swept volume and desired engine
speed, or from the BMEP only, or from the BMEP and swept
volume and desired engine speed. I chose the last one. The
program predicted the final HP to be 26.83. I need a value
of 12.04 (s/m * 10000) for the exhaust blowdown time area.
The upper and lower targets for the transfer ports are 6.80
and 11.14 (s/m*10000). The inlet port will need a time area
of 10.59 (s/m * 10000). The stock Blaster engine looks something like this - 17
HP (+17% loss) = 19.89 at crank @ 7000 RPM. The crankshaft
horsepower divided by the RPM it's peak is achieved at,
multiplied by 5252 reveals the torque figure (19.89 / 7000 *
5252 = 14.92). This is pretty close to the Yamaha supplied
number which is 15. The BMEP will be the engines torque
multiplied by 1236 and divided by the engine displacement
198 cc's (14.92 * 1236 / 198 = 93 BMEP). This time I added a
horsepower loss so my final number is a bit different than
it was before. The help file explains the output as either upper, mid or
lower TA (time area). As the BMEP rises the engines ports
need to be targeted toward the upper time area. The output
values are expressed in Time Area (per unit displacement).
That is the mean port area (cm^2) / displacement (cm^3) *
the time the port is open (in seconds). The port duration
(in degrees) / time (seconds) * the mean port area (sq. mm.)
= s-sq. mm. • s-mm^2/cc*10^5 ReedValve was used to "size up" the reed cage and reeds.
When the data was calculated from the input parameters I
found that the stock reed cage has a designed flow area on
1244 mm^2. The suggested carburetor size is 36 mm. The new
reed material has a natural frequency of 183 Hz - it was
changed to .52 mm. The tip lift ratio is 0.13 and the lift
at the reed tip is 4.56 mm (on the low side). The program
estimated the crank HP for this reed to be over 41 with
torque coming in at 27 ft.lb. Estimated wheel horsepower is
36. That is to say that this reed cage is large enough to
supply adequate mixture for that kind of power - in other
words the cage is big enough. It is interesting to note that
the data output from this program is quite different than
what was received from the Blair program. The programs Rotary, Rotary-2 and IntakeTm do not apply
to engines of this type. More to come - Rick
Two-Stroke Software Review
Part 1 - Introduction to Two-Stroke Software
Bimotion v 2.1 - Blair S.A.E. - Dynomation 2 - MOTA v 5.0 - TSR
Using TSR Two-Stroke Software
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Date Last Modified: 9/5/99
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