SOFTWARE MANUAL BIMOTION 4-stroke Copyright © 2000 Billy Alvarsson. Ver 1.1. All rights reserved. The computer program is protected by Copyright laws and must not be copied except as a safety copy for the owner’s use. This manual does not explain all theory behind the calculations that is made. It is assumed that the user knows the fundamentals about four stroke engines. Licensed user will always get new versions send automatically by e-mail for free. Latest updated manual can be downloaded from http://www.knuten.liu.se/~bilal270/index.html
Questions or bug reports are sent to:
[email protected]
Table of Contents 1.
INTRODUCTION 1.1 1.2 1.3 1.4
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Valve lift Valve velocity Valve acceleration Valve time-area
2.
GENERAL
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3.
LOADING AND SAVING FILES
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3.1 3.2
4.
Load a user file Save a user file
ALTER AND DISPLAY DATA
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1. Introduction The 4 stroke program computes valve lift, valve velocity, valve acceleration and valve time-area, for a given engine specification. It also shows how these quantities vary when relevant engine dimensions are changed or when the engine speed is changed. The data required by the computer is: bore, stroke, intake and exhaust valve diameter, number of valves per cylinder, valve seat angle, valve timing, valve lift at 10-degrec intervals and engine speed range. Back
1.1 Valve lift A conventional valve lift diagram is displaced showing the phasing of the cams and the overlap period. The effect of changing the phasing can be seen instantly. Back
1.2 Valve velocity The peak velocity can be compared to the stock engine and to state of the art, competition engines. Back
1.3 Valve acceleration When the acceleration reaches a positive maximum, the contact stress between the cam and follower (and between the valve and valve lifter) will be greatest. This figure should be compared to previous figures to see how the stress will increase due to the change in acceleration. The actual stress will be F + m⋅a/A, where F is the spring force at that particular lift, m is the mass of the moving parts (half mass of the spring is regarded as moving), a is the acceleration and A is the contact area. So, an increase in 'a' can be countered by a reduction in m, or F, or an increase in A. When the acceleration is negative, the cam is dropping away from the follower and valve motion is controlled by the spring. The required spring force to avoid valve float is k⋅x, where k⋅x > m⋅a where k = spring rate [m] x = valve lift [m] m = mass of moving parts [kg] a = valve acceleration at lift x [m/s2] Note: m will be the weight divided by the gravitational constant, 9.81 m/s2, of the valve, collets, collar, and half of the spring(s). If a rocker arm is used then the moment of inertia should also be added or, to simplify things, it can be approximated to a bar to be on the safe side which will give a greater value of inertia.. The moment of inertia of an uniform bar is I = m⋅L2/12 + m⋅r2. m = rocker arm mass [kg] L = total length [m] r = distance rocker arm center of gravity – pivot axle. [m] R = distance valve, rocker arm contact point – pivot axle. [m] The force acting on the spring due to the inertia is FI = I⋅a/R2 [N]. Add this force to the previous.
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If the spring force k⋅x is less than m⋅a then the valve will lose contact with the cam at that point. If k⋅x is significantly greater than m⋅a, then the stress at the cam follower is unnecessarily high. The program displays valve velocity and acceleration against a given crank speed. The result can also be varied by changing the valve lift data. Back
1.4 Valve time-area Time-area is the quantity given by integrating the valve lift, diameter and the time it is open over each full cycle; it therefore represents the amount of air the port is able to flow. The program assumes that gas flow will not increase once the valve has exceeded a certain lift. If air flow tests, etc, indicate a particular value for this maximum effective lift, then it may be used in the program; otherwise the program will default to a value of 0.27 ⋅ valve diameter. The program displays time-area in units of s-mm2, and specific time-area, in units of smm2/cm3 (i.e. time-area per cc of piston displacement) so that the figures may be compared with engines of different sizes and so that the effect of changing the piston displacement may be seen. The time-area figures are displayed against a range of crank speeds; alternatively, the figures can be displayed for a variety of valve diameters, at a constant crank speed. The effect of a different cam profile can be seen quite clearly also in a diagram. Back
2. General To accept recommended or previous values just enter. (0 omitted if enter nothing) If errors of any kind appears (usually due to file can’t be found) the program will return to the menu with a simple error message *** Error, returns to menu *** Back
3. Loading and saving files The program does not understand lower case characters as input except from text strings as paths and names. The first dialogue: Press L to load a file or enter to continue with new specifications.
To load a user file press “L” otherwise enter. Back
3.1 Load a user file: Type file name without extension, or enter to alter path. Path: Current ? _
If you wish to load a file from another folder than current then simply enter, else type the file name without the extension. If you enter this syntax help will show up: Syntax: ? _
Enter the entire path here according to the syntax above (without ). The load process above is repeated until the file name is entered.
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The program remembers last loaded path used. IMPORTANT! This path must not contain folders longer than 8 characters/folder! Back
3.2 Save a user file: Files will be saved as in example: Kawasaki GPZ1200 Original --> kawasako.*. The first 7 letters are part of the name, the last one is T/O (Tuned/Original). Just enter (T) or (O). Delete this T/O with (D). If no option, first 8 letters will be part of the file name. File will be saved when the choice is accepted with ‘enter’. Accept present path or Enter path to folder (if different from current)? C:\TEMP\ Enter here gives: Current name: TEST Accept saving as or enter engine name, (Last file char is T/O), or (P) to alter path (T) to add 'Tuned' (O) to add 'Original' (D) to delete T/O info.? _
Back
4 Alter and display data The menu : Menu Display Time-Area ................... (0) Valve lift .................. (1) Velocity .................... (2) Acceleration ................. (3) Alter Valve Data .................. (4) Cam Data .................... (5) Present dimensions .................. (6) Restart ............................. (7) SAVE ................................ (8) LOAD ................................ (9) QUIT ................................ (10)
Choice ?
If choice 0, Display Time-Area gives:
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When valve lift reaches a certain value, the air flow no longer increases. This usually occurs when the lift is 0.27* valve diameter, in this case intake lift: exhaust lift:
10.53 mm 8.1 mm
Present lift factor is: intake = .27 exhaust= .27 Enter to accept or A to alter this factor.? A
If A is entered : Enter the max effective intake valve lift/dia. factor ? exhaust valve lift/dia. factor ? Which valve, I/E ?
If I is entered: Vary time-area against engine speed ........................ (0) valve size .......................... (1) ? _
If 0 is entered : Minimum speed, rpm ? 5000 Maximum speed, rpm ? 12000 Increment ? 1000
These values gives: 12-10-2000 TEST BIMOTION Four Stroke Intake. Crank Time-area rev/min s-sq mm 5000 4.66 6000 3.88 7000 3.33 8000 2.91 9000 2.59 10000 2.33 11000 2.12 12000 1.94 End of list.
Sp t-a s-sq mm/cc 15.6 13 11.1 9.7 8.6 7.8 7.1 6.5
x10^-3 x10^-3 x10^-3 x10^-3 x10^-3 x10^-3 x10^-3 x10^-3
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Choice 1, Display Valve lift diagram can not be shown here. Back If menu choice 2, Display Velocity gives: 12-10-2000 TEST BIMOTION Four Stroke At 11000 rev/min, valve velocities are: Crank angle 0 10 20 30 40 210 220 230 240 250 260 270 280 End of list.
Intake (m/s) 0 6.3 7.7 8.2 6.9
Exhaust (m/s) 0 7.3 7.3 8.3 5.6
-6.6 -7.8 -7.9 -6.3 -6.1 -2.6 -1 -.7
-10.4 -4.3 -7.6 -6.6 -5.9 -4.3 -2.2 -1.1
Back If menu choice 3, Display Acceleration gives: 12-10-2000 TEST BIMOTION Four Stroke At 11000 rev/min, the valve accelerations are: Crank angle
Intake (m/s^2)
Exhaust (m/s^2)
10 20 30 40 50
-41.4 -50.5 -54 -45.7 -42.7
-47.9 -47.9 -54.4 -37 -39.2
51.4 52.3 41.4 40.1 17.4 6.5 4.4
28.3 50.1 43.6 39.2 28.3 14.4 7.4
220 230 240 250 260 270 280 End of list.
Back
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If choice 4, Valve Data is entered: The values displayed is the present ones. They are accepted by simply enter. No. of intake valves/cyl. No. of exhaust valves/cyl. Intake valve dia. Exhaust valve dia.
1 ? 1
39 30
Enter 45 deg if not known. Intake valve seat angle 45 Exhaust valve seat angle 45
If choice 5, Cam Data is entered : Intake, Exhaust or both (I,E,B) ?
Enter I gives : Adjust the valve clearance to their normal settings and turn the engine until the intake valve is lifted 1.0 mm. Measure the lift at 10 deg. intervals until the valve closes. Enter the lift figures against the corresponding crank angle or enter to accept previous value. The input will stop when 99 is entered. Crank angle BTDC for intake lifted 1.0 mm.
10 ? 10
Enter 10 gives: Angle 0 10
Lift 1 ?
Current 1.95
Current value is accepted by enter. The input procedure will stop when reaching 350 degrees or entering 99. Back
5. Display Data If menu choice 6, Present dimensions gives: 12-10-2000 TEST BIMOTION Four Stroke Bore, mm .................................. Stroke, mm ................................ Displacement, cc/cyl ...................... No. of valves, intake ..................... exhaust .................... Valve dia., mm, intake .................... exhaust ................... Max valve lift, mm, intake ................ exhaust ............... Valve seat angle, deg, intake ............. exhaust ............ Valve lift/dia flow factor intake ......... exhaust ........ Crank ang. at 1.0 mm lift, intake BTDC ... exhaust BBDC ...
76 66 299.4 1 1 39 30 10.6 10.4 45 45 .27 .27 10 60
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12-10-2000 TEST BIMOTION Four Stroke Intake deg. lift deg. lift ------------------------0 1 160 10 10 1.95 170 9.45 20 2.9 180 8.77 30 4.06 190 7.9 40 5.3 200 7.05 50 6.35 210 5.9 60 7.33 220 4.9 70 8.3 230 3.72 80 8.95 240 2.52 90 9.75 250 1.57 100 10.29 260 .65 110 10.5 270 .25 120 10.6 280 .1 130 10.6 140 10.6 150 10.43
Exhaust deg. lift deg. lift ------------------------0 1 160 9.85 10 1.95 170 9.5 20 3.05 180 8.85 30 4.15 190 8.25 40 5.4 200 7.5 50 6.25 210 6.58 60 7.15 220 5 70 7.95 230 4.35 80 8.65 240 3.2 90 9.25 250 2.2 100 9.7 260 1.3 110 10.05 270 .65 120 10.25 280 .32 130 10.4 290 .15 140 10.35 150 10.2
Choice 7, Restart simply starts from the beginning. Choice 8, 9 SAVE, LOAD se above. Back
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