|
My quick usage overview video: Using ECcalc30 The heart of the program, the pipe return waves graph on sheet 3:  Look at the bottom left of sheet 1 to see the 4 sheet tabs. You go to the desired sheet by clicking on its tab. The design steps are listed on sheet 1.  Here is sheet 1 where you will enter the basic engine data. Each row corresponds to an RPM (C5-C13) with the # at C5 corresponding to the end of the pipe powerband. The sequence of calculations and #'s displayed continues for rows 6-13 at rows 19-26. The basic design steps are listed at the bottom under "Pipe Design Steps". At D6 is calculated an approximate exhaust pulse time duration based on engine specs and exhaust port area on sheet 4. This affects the return waves durations. Getting this exactly right is impossible without the expensive pressure trace equipment that race teams use but you can get close here. For example, the difference between a .8ms and .9ms exhaust pulse (a 12% change) is only a 5% time span difference in the return diffuser wave so this calculators approximation is good enough.  Step #1: It's best to get paper traces of your ports for the most accuracy but ECcalc30 can do a decent job of guesstimating the port size and resultant exhaust pulse time just by knowing the cylinder bore, how many exhaust ports there are, and their max widths. If you aren't going to measure the port widths every millimeter down then on sheet 4 just enter the # of exhaust ports at I6, enter the widths of exhaust ports at I2 (only for triple exhaust) and I4 and then just click on the CALCULATE button and the calculated values will appear at the J column (rows 10-43). Estimated values are ok for pipe designing but not so good for evaluating porting needs (listed farther down the same sheet). The exhaust port shape is graphed there but it is sideways (90* CCW) which is the easiest way for me to represent it since some seemingly simple things are hard to do on Excel.  For the most accurate results start by making an imprint of your exhaust port with paper inserted into the cylinder. Align the edge of the paper at the top edge of the cylinder and press onto the paper along the edges of the port(s).  How to get the port trace: With cylinder removed... Just cut a rectangle of paper as tall as from the cylinder top to a bit beyond the bottom of the port. Its width should be a bit more than the cylinder diameter multiplied by 3. Insert the paper into the cylinder so that its top edge is even with the top edge of the cylinder. With cylinder on bike but head removed... Just cut a rectangle of paper as tall as from the cylinder top to the piston edge with the piston as low as it will go. Its width should be a bit more than the cylinder diameter multiplied by 3. Insert the paper into the cylinder so that its bottom edge is even with the top edge of the piston. Then spread the paper apart so it is pressing against all of the cylinder and then hold it in place where the paper overlaps itself. Then reach in and press your thumb onto the paper where you think the top of the port is. Once you can feel the top edge then press hard on the edge without pushing the paper into the exhaust port. Do this all along the exhaust ports edges. Remove the paper and enhance the trace with an ink pen. Mark along both sides of the ports every 1mm and use ruler and pen to connect the marks. Then use your ruler to measure each port width for each 1mm and write them down as illustrated above. It's not necessary to go all the way to the bottom of the port. Here's pics showing what I'm describing...      Measuring from the top edge of the paper, make horizontal marks to the left and the right of the exhaust port(s) every 1mm. Then draw horozontal lines across the exhaust port that are spaced 1mm apart as you see in the graphic below. Measure the center millimeter width of each 1mm space and write it down. If there are two or three sections along one line then add their widths together. For example if the main port is 40mm and each auxiliary port is 10mm then the total is 60mm.  [In the following screenshots I often border the input cells that I'm talking about in red.] Manual Exhaust Port Measurement Entry On sheet 4 starting from the top width to the bottom width enter all the exhaust port widths (for every 1mm down that you previously wrote down) into the spaces at sheet 4 from J10 to J43. Also enter the exhaust port duration, engine compression ratio, and mm above the exhaust port from the port top to the TDC (top dead center) point on the cylinder (where the top edge of the piston is at TDC).  At the lower left of sheet 4 is a mini calculator that shows the mm above port for the exhaust and transfer ports based on the engine stroke and the conrod length. Use that or an online port duration calculator for the "mm above port" entry at K6 and K53. If you measured the cold above port distances then enter them at A50 and A52 to see what the estimated hot distances are. (They are more due to TDC raising with hot con rod extension) If you used my method for finding the hot distances then use those in the online calculator to find the durations.  Step #2: On sheet 1 enter the port durations (read how to measure to find the hot durations for highest accuracy) and end RPM of the pipe powerband (at the end of being "on the pipe" which is usually about 750 RPM above peak power RPM) at C5. The RPM you enter at C5 should not cause more than a 25meter/second piston speed displayed at D12 and a warning will display at D13 when it exceeds that. When entering RPM do not type in the comma. For example enter 9000 instead of 9,000. The port "duration" refers to how many crank degress the port is open each crank revolution. It's best to determine them by using an online calculator and the port heights (instead of using a degree wheel which is inaccurate because it's hard to see when the top edge of the piston is level with the top edge of the port). If you haven't used my method to calculate the "hot" durations then subtract 2 degreess from the exhaust duration and 4 degrees from the transfers duration. That's the typical difference between hot and cold.  The RPM you enter at C5 corresponds to the very end of the pipe powerband, a bit higher than where you would normally upshift. The graph below shows a pipe powwrband of 2250 RPM. So with the example below the end of powerband RPM is about 750 RPM more than peak power RPM. So if you know the intended peak power RPM just add 750 to it to figure the end of powerband RPM.  At D10 enter "Y" (for yes) if your engine has a reed valve intake or "N" if it doesn't. At F15 enter "Y" if your ignition system varies the ignition timing with RPM (like any normal modern CDI does), or "N" (for no) if it has fixed timing ignition (such as was on all old bikes such as the old Husqvarna and Maico motocross bikes).  Step #3: If you don't know the exhaust gas temperature then just leave these 3 values as they are. Or you can find it out by analyzing your current pipe if you know the beginning and ending pipe powerband RPM. If the power graph of your pipe/engine on sheet 3 is higher in the RPM range than what you know is true for your pipe then lower the temp at D14 till the graph matches reality. (and vice versa for the opposite) If you measure it then enter the exhaust gas temperature in Celsius at D14 (click here for a farenheit converter), distance from piston to thermocouple at D15, and RPM of test temp at F14. If you don't know what it is then just use 600 at 10,000 RPM at 150mm. The best way to know the exhaust gas temp without measuring it is to ride the bike with a speedometer on it (which can be a bicycle speedometer) and note the speed when the bike is at peak power. Then use the gear ratio calculator to figure out at what RPM that happened. Then fill in all of sheet 1, 2 + 4 and on sheet 3 click the Auto-Graph button at H185 to see the peak power RPM. Then keep adjusting the temperature at sheet 1 D14 and clicking the Auto-Graph button on sheet 3 till the graph matches reality.  How to use the Gear RPM Range Calculator: Go to sheet 3 and scroll down below the pipe power grapher to see the Gear RPM Range Calculator. A) Measure your rear wheels outer circumference: Push the bike till the valve stem is at the very bottom. Mark the ground next to the tire equal to where the stem is. Sit on the bike and roll forward till the stem is once again at the very bottom. Mark the ground there and measure the distance between the marks. If you measured in inches then put that value at J231 to know the equivalent distance in meters at K231. Enter the wheel circumference meters at G231. B) If you leave G229 blank then this calculator will use the end of pipe powerband RPM from sheet 1. Otherwise it will use whatever RPM you enter there. C) Put the bike in 1st gear. Take off your ignition cover and prop the bike up so the rear wheel is off the ground. Take the spark plug out. Spin the wheel till the valve stem is at a spot that you can easily remember (such as visually at the top edge of the swingarm.) Mark the flywheel and the cases so the two marks align. Slowly turn the rear wheel while counting the complete turns of the flywheel. Do this till the valve stem returns to its original position. A sloppier but easier way is to hold a pencil in the spark plug hole and count the times the piston hits it. Write down the crank rotations per wheel rotation and put that number for each gear from G237 to G242. D) Take note of the RPM spread in the K column of 2nd gear. Your pipes powerband should be at least that wide. To find out the RPM for a certain bike speed (KPH or MPH) just keep entering different RPM at G229 till the right speed is listed for the right gear. (the speed in a certain gear you experienced)  This is important to know to make sure your pipe powerband is longer than the longest gear RPM spread. On my 4 speed 100cc I had to resort to an odd design because the longest pipe powerband of normal expansion chamber was just barely long enough for the gear RPM spread and so I had to upshift at just the right RPM or a little higher or else it would be out of the pipe powerband which is deadly on a 100cc. Needless to say it wasn't any fun having to be so precise all the time. Click here to read about the unusual design I had to use. Step #4: On sheet 1 enter the stinger inner diameter at L32 if you don't want to use the size displayed at L31. That recommended size will be used if you keep L32 blank. Look at the comment hidden at N30 to see common available inner pipe diameters for use as stingers (from Metals Depot):  Enter the pipe inner diameters at H31 to J31. Enter the metal thicknesses at H35 and H37. All these dimensions are important to figuring out the approximate gas temperature inside the pipe which affects wave speed. The temperature decrease along the pipe is calculated by the outer area as the "dissipator" of heat. The max belly diameter at K31 is not a strict value but it's a good average max.  Designing a New Pipe Step #5: If your Excel can use macros then just click the calculate button for the right lengths to be entered into A19 to E19. When calculating for pipes with flared headers you need to first enter the distance from the piston face to the beginning of the flared section at A19. This value won't be changed when you click the Calculate for Flared Header button. If these calculated lengths are incompatible with the available space on your bike then you can change the top RPM but keep in mind that single cylinder cranks are tuned to a certain top RPM and the farther you stray from that the more vibration you will have at top RPM. But of course you can use my crank balance calculator to know how to retune it.  Step #6: The next step on sheet 4 helps determine if there is enough blowdown area/time to keep from limiting top RPM power by limiting the intake charge transfer to the cylinder. Scroll down a bit and enter the total transfers width at K51 which is the width of all the transfers (measured about 2/3 down from the top of the transfers) and half of the boosts total width added together. Typical values are 54% of the cylinders circumference (bore x 3.14) for 4 transfers and boosts, or 40% of it for 2 transfers and boosts. Those two calculated widths (useful if you don't know the width of your transfers) are at L51 and L52 which you can enter at K51 if you know the transfer arrangement but haven't measured the widths. Enter the transfers duration at K52 and then at K53 enter the distance from the top of the transfers to the "deck" (where top piston edge is at TDC) point on the cylinder. Then click the CALULATE button and note where the blue graph crosses the 1.0 line which indicates the peak power RPM of the engine porting as if it didn't have an expansion chamber. In this example it is just right if you want the highest peak engine power (at the expense of a meaty mid-range). The transfers total width, duration, and when the exhaust pressure overlaps the transfers (7000 RPM in this case) all affect the engines peak power RPM. I've analyzed race engines with 0% overlap at K47. If the overlap is more than 10% and your engines PPRPM is too low then you need to raise the exhaust port. If it is less than 10% but the PPRPM is too low then you need to raise both the exhaust and transfers.  Step #7: On sheet 2 you can let the sheet automatically create the diffuser dimensions or you can manually enter your own. Just put an x at F39 for it to automatically calculate for you a diffuser. Then select at G45 to G47 what type of diffuser you want. The beginning diameter and angle for the 1st cone are at C46 and C47. For the 2nd cone at D46 and D47, and for the 3rd cone at E46 and E47, and those are all transferred to a section to the right where they will be transferred to sheet 3 to be used in the creation of the diffuser return wave. If you want to change the total diffuser length, beginning diameter, or belly diameter then do so at sheet 1. If the desired cone length exceeds the range of 80mm to 440mm then you have to put an x at F40 and do it all manually.  For manual diffuser creation of a 3 cone diffuser outside of the range of 80mm to 440mm you can still use the values created in the mini calculator. First make sure the space at F39 is blank and then enter an "x" at F40. Then enter the three diffuser angles into C7, C17, and C27.  Then enter the two beginning cone diameters from D47 and E47 to B17 and B27. The mini calculator says the first cone is 30mm long, the second 20mm, and the third 20mm. So then enter the first 3 pressure change #s from row 12 to the M column for the first cone. Then the first two change #s from row 22 to column M. Then the first two change #s from row 32 to column M. Make sure all other cells in the M and N column have 0 in them.  Or you can use the cone calculator at B37 to B40 to design your own diffuser one cone at a time. Here's a look at what the negative diffuser waves look like with the 3 diffuser designs.  Now we can calculate the baffle cone. Usually a single cone is good enough but you can also virtually try the other two types to see how they all compare on the power graph. Sheet 1 usually gives the right cone length for a good form of powerband and good power. The automatic option allows you to choose what you want and not have to touch anything else. Just put an X at the desired section and everything will be done for you. It uses the baffle length from sheet 1 E19. You can see the single cone angle at B88 and the details for the other two types are to the right of the selection cells.  If you want to manually create a baffle then use the manual calculator for your own design (if it isn't a single cone). Or just one of the 3 cone designs presented on this sheet. Sometimes the increasing angle baffle gives an increase in average pipe power so I will show how to do that. First enter the calculated cone angles into A56, A65, and A74.  Then enter the beginning diameters from J88 and K88 into A63 and A72. That's all that is needed. The program then takes the pressure change #'s and enters them in the column that will be read by the return wave simulator on sheet 3.  Pipe Power Calculator
The whole point is to have the best pipe powerband (graphed power height and width). After entering the estimated peak horsepower at I186 just click onto the Auto-Graph button and the calculations will display the resultant pipe powerband below the return waves graph.  Power Factors: The intake is determined mostly by the average height of the diffuser wave, how much of the time it occupies between BDC and TC, and the pressure a fraction before TC. The exhaust trapping is determined by the pressure at EC and mid TC-EC. Those two graphs are multiplied together to get the power.  Trying Variations: It is good to record the results of the current pipe design and then try a couple variations and record each ones result. In this example I shortened the belly by 40mm and the power increased but it shortened the powerband a bit. (You can't create energy, just move it around). You can change the header or diffuser length on sheet 1 to move the powerband up or down on the RPM scale. And changing the belly length will change the powerband shape a bit. If you add 20mm to the belly then subtract the same amount from the diffuser. If you've selected manual diffuser design on sheet 2 then you need to re-do it there after any diffuser length changes on sheet 1. For more over-rev and less peak power increase the belly length. For a wider powerband increase the diffuser/belly/baffle and decrease the header so the same distance to the baffle remains.  With your pipe design finished you can go to sheet 4 to know how to cut out the patterns from poster paper which you can then trace onto the sheet metal (.7mm or more thickness) before cutting it with tin snips. You'll need an extra long ruler. This sample pipes data has been entered in the cone making section below for you to see how its done.  Every diameter needs the sheet metal thickness added to it which is done for you at A38 to C42. That section shows the calculated 3 cone diffuser values and the values for a 1 cone baffle. For anything else you need to manually enter the values into the light blue cells at A29 to C34. Make sure you add in the sheet metal thickness to all the pipe diameters you enter starting at A29. After entering the data in the blue cells then use the calculated data at D29 to H34 to draw the graphics pattern on poster paper. The gray area of the graphic is the pattern to be cut out, laid on sheet metal, and traced around with a felt marker so you can cut out the cone section with your tin snips. Each of the 6 rows (29-34) are for a separate cone.  You can also use the Cone Layout software from this site which has the added advantage of making the cutout patterns for more complex designs. Questions & Answers What is the most import guideline for designing a diffuser? Make it 3 cones if it's for a engine with reed valve and you want more power and don't care if the end-of-powerband is more abrupt. What if the available space for the belly is less than the recommended belly diameter? Just make do with the available space. But the wider the belly, the more power it will contribute. What if I design a pipe with a belly diameter greater than the recommended max? No problem but as you go much beyond it then you may need to use a decreasing angle baffle. What happens if my design varies from the suggested lengths on sheet 1? I encourage every one to experiment with variations from what is recommended to get the absolute best power. But usually what is recommended is very close to ideal. What if the recommended pipe section lengths on sheet 1 are impossible for the space available on my bike? Well then you'll have to change the lengths to match the bike. Bike designers have always had that problem. If the designed pipe is longer than the available space then consider changing the end of pipe powerband RPM so the design will be shorter or longer. On my bike I had to use a 2 cone diffuser design due to space limitations although I wanted a 3 cone design. Can I be lazy and just make the diffuser a single cone for my trail bike with reed valve? Yes but it won't have an ideal 'delayed' wave peak which is needed for optimal power for the trail. Maximum effort at making a great pipe is essential if you want the best power. Don't be lazy and take shortcuts. The enjoyment of the bike will far outlast these short lived difficulties. What recommendations can you give for designing a pipe for a bike for a beginning rider? For a beginner you might want a pipe that gives as little "hit" as possible. You can do that by making the belly width smaller, the belly longer, and the baffle longer. Also you can design for the end of the pipe powerband to be about 1000 RPM below the normal top RPM. It would make it more grunty like a trail bike. Also you can replace the base gasket with glue and add an extra head gasket, all to lower porting for less peak RPM. What can I do to get more pipe boost? If your pipe powerband is longer than what you want or need then you can shorten the baffle with steeper angles for a stronger but shorter return wave. Keep in mind that the wider the belly is the stronger the cone angles will be for the same cone length. Bigger angles mean stronger return waves. Is there any advantage to a 1.5 degree flaring header? Yes if you can have a belly at the maximum width recommended or even more in order to keep decent angles of the diffuser cones. Dynos have proven that doing that produces more high RPM power. So it's mostly recommended for race bikes. Below are the spreadsheets hidden comments in case your computer won't let you view them all: Sheet Cell Comment Sheet1 A4 Degrees the exhaust port is open. This has to agree with K5 on sheet 4. I prefer to use the hot duration which is around 2 degrees less. It reduces when hot due to the elongation of the conrod. Sheet1 B4 Degrees the transfer ports are open. This has to agree with K52 on sheet 4. I prefer to use the hot duration which is around 3 degrees less. It reduces when hot due to the elongation of the conrod. Sheet1 C4 Make the RPM at C5 a multiple of 250 and the very end of the desired pipe powerband. Sheet1 D7 end of negative exhaust trailing wave Sheet1 D9 enter "y" for yes, or "n" for no. Sheet1 D11 For piston port intakes you need to enter the intake port degrees of port opening. Sheet1 D13 This warning displays when the piston speed is greater than 25m/sec at the end of powerband RPM at C5. Sheet1 A14 Lowest (due to lean jetting, too early ignition timing, low exhaust port, high compression, very fast squish velocity) is 525. Highest (due to rich jetting, late ignition timing) is 675C. If you haven't measured it then you can keep trying different values until the end of the powerband on the graph on sheet 3 equals what you feel when riding. Cylinder heads without squish bands cause a hotter exhaust in the pipe due to a less rapid burn. For them a good average is 650 degrees. Sheet1 F14 Enter n if the ignition timing doesn't increasingly retard as RPM increases. Enter y if you have a normal CDI. Sheet1 A16 This is a recommended straight header length (starting from piston face) that causes the beginning of the return suction wave from the flared header to return to the cylinder halfway from exhaust opening to transfers opening. Sheet1 B16 This straight header length causes the flared headers return suction wave to return to the cylinder at transfers opening at 1500 RPM above the start of powerband RPM Sheet1 C16 If you haven't measured your EGT then use 600 for an average engine. Higher BMEP (power) creates a higher EGT and vice versa. Sheet1 E16 mid header temp at RPM @ C5 Sheet1 A17 header length that is straight (not flared) starting from piston face. You can use a length between the calculated A16 and B16 values for use with a flared header if you want to have the return wave frm the header not return right away. Make sure A19 is more than 0 before clicking the button "Calculate for Straight Header". Sheet1 B17 If any of the header is flared (expanding) then enter its length here if you are analyzing a pipe. Otherwise click the calculate button at A30 to design a new flared header section after entering the length of the straight beginning section of the header, something between the values at A16 to B16. If you want it to start flaring ASAP then just enter the mm from piston face to the part of the pipe where you can start flaring it. Sheet1 C17 Keep this as a multiple of 10 if you are entering it manually. Acceptable range is 160 to 440mm if you are having sheet 2 calculate it automatically. Otherwise the max length is 520mm. Sheet1 D17 Enter this as a multiple of 10 if entering it manually Sheet1 M28 This is the length from the end of the baffle cone to the end of the stinger if its used w/o a silencer. With a silencer you need to add the millimeters that exist between the end of the stinger and the first pulse diffusion holes in the silencer. The cell N32 shows the % of the baffle wave that is overlapped by the stinger wave. See comment at M32. Sheet1 F17 The changes in temp for each RPM comes from C37. Sheet1 A28 "This sets the beginning of the pipe powerband by having the end of baffle wave at .8 of TC to EC. " Sheet1 B28 This sets the beginning of the pipe powerband by having the end of the baffle wave at .8 of TC to EC. Sheet1 C28 This makes the diffuser wave 2.5x the time of TC to EC at C11 RPM. Sheet1 D28 This is for a healthy overlap of waves Sheet1 E28 This adjusts the baffle wave length to an average value but it may need to be longer if the gearbox has less than 5 gears. If you make it shorter then it will hit harder but may cause excess engine heat inside the pipe powerband and excess power dip before the pipe powerband. Sheet1 H28 beginning header outer diameter Sheet1 I28 ending header outer diameter Sheet1 K28 This is a multiple of the header diameter. Sheet1 M28 This is the length from the end of the baffle cone to the end of the stinger if its used w/o a silencer. With a silencer you need to add the millimeters that exist between the end of the stinger and the first pulse diffusion holes in the silencer. The cell N32 shows the % of the baffle wave that is overlapped by the stinger wave. See comment at M32. Sheet1 N28 The program simulates the return stinger wave to be combined with the baffle wave where they overlap. If a silncer with bleed holes in the inner tube is used then the strength of the return wave is 25% of what it would be w/o a silencer. Sheet1 A29 Put this value at A19. Sheet1 B29 Put this value at B19. Sheet1 C29 Put this value at C19. Sheet1 D29 Put this value at D19. Sheet1 E29 Put this value at E19. Sheet1 A30 Click this to calculate pipe lengths for a pipe without a flared header Sheet1 B30 Click to calculate pipe lengths with a flared header. First enter the straight header length (the beginning part that isnt going to be flared). Sheet1 C30 Enter # of diffuser cones. Refer to pipe design guide below. Enter 1 or 2 or 3. Sheet1 F30 cc of single cylinder (swept volume) Sheet1 G30 cc that the piston displaces from BDC to TDC. Unfortunately this is the way to calculate 4 stroke engines but for some reason it is also commonly used for 2 strokes although it is not the correct method. The correct method is used at G31 Sheet1 K30 This is calculated using the peak exhaust pulse psi calculated on sheet 4. It varies from 2.5 to 2.8 times the ideal header diameter. Sheet1 M30 Recommended diameter for the entered length. Don't use a smaller size if using a flared header. Sheet1 N30 Closest available size from Metals Depot (6.2, 7.7, 9.4, 10.1, 12.7, 15.9, 19, 22.2, 25.4, 28.6, 31.8, 34.9, 38.1, 41.3, 44.5mm) Sheet1 G31 Engine size correctly calculated as volume above exhaust port. This comes from sheet 4. Sheet1 V31 The higher this # the more temp is reduced from header to stinger. Sheet1 H32 Ideal header diameter. The Calculate button has to be clicked on sheet 4 before this will calculate correctly. Sheet1 I32 this is the half angle (which is what I always refer to when I talk about pipe angles). Best is 1.5 to 2 degrees. Sheet1 L32 Enter the desired stinger size here. You can make your own stinger with the suggested diameter from M31, buy a pre-made pipe of diameter listed at N31, or enter another diameter. If you leave this blank then L31 (the value the program will use) will be the value from N31. It's not recommended to go below the recommended size at M31 if you have a flared header. Sheet1 M32 This warning displays when the stinger length is short enough to allow the stingers return suction wave to overlap the baffle wave before the rising piston closes the exhaust port. That redices dynamic compression. How to reduce the return wave strength is to have the silencers pulse diffusion holes start as minimal # of them, gradually increasing their #s. If you run w/o a silencer then all you can do is lengthen the stinger. Otherwise the end of the baffle wave will be reduced by the stinger wave. This may affect the pipe powerband, and it may not. Try the desired stinger length and then calculate the pipe power on sheet 3. Then lengthen the stinger till the warning doesn't display and see how the pipe power graph is. If there's no difference between the two then its acceptable. Sheet1 L33 This is the cross sectional area of the diameter at L32. Sheet1 M33 This is the cross sectional area of the diameter at M31. Sheet1 N33 This is the cross sectional area of the diameter at N31. Sheet1 A35 header length Sheet1 A36 Ignore B37 and C37 if your ignition timing varies with RPM, retarding as RPM increases. Sheet1 B36 choose from RPM at C8 to C11 Sheet1 C36 Enter the change in C temp for every 1000 RPM with the engine under load. Typical is 30 for engines with CDI's with a normal timing curve, and 60 for engines with no timing curve. Sheet1 A38 mm from piston to baffle Sheet1 A40 Estimated length to baffle Sheet1 AF45 enter the end time minus the start time of the secondary wave Sheet1 AG45 return time the secondary wave needs for its peak to match the peak of the exhaust wave Sheet1 AE46 time it takes for the return wave to enter and leave the cylinder. Sheet 2 CommentsSheet2 B5 inner diameter in millimeters Sheet2 C6 Diffuser cone angle from centerline, not total angle Sheet2 C8 When manual is chosen the angle from C7 is placed here for the program to use. When automatic is selected at F39 then the angle placed here to use is created by the program at C46 but this depends on if you choose 1 or 3 cones at G45/46/47. Sheet2 N9 For manual diffuser design enter the pressure change #'s for each 10mm section. (rows 12, 16, 22, 26, 32, 36) Sheet2 B15 leave blank if designing a single coned diffuser Sheet2 C16 leave blank if designing a single coned diffuser Sheet2 B25 leave blank for a single coned diffuser Sheet2 C26 leave blank for a single coned diffuser Sheet2 D37 Enter the 3 diffuser cone lengths if you are entering them manually. Make sure each length is evenly divisible by 10. Sheet2 E39 Automatic transfer of the correct pressure change #s to column M and N after the computer designs the 3 cone diffuser. The allowable range is 80 - 440mm long for the diffuser. You don't have to enter or delete anything if this option is selected. Sheet2 E40 Use this if the diffuser length is outside of the allowable range for automatic (80-440) or if designing the diffuser manually Sheet2 I43 This must be entered in maually. Sheet2 F44 use this option if you select "automatic" above Sheet2 A46 1st cones beginning inner diameter Sheet2 F46 This gives the best power Sheet2 F47 If this causes the angle at C8 to be more than 8 degrees then use the piston port 3 cone option, and if that causes more than 8 degrees then use the 1st option Sheet2 A55 cone angle from centerline, not total angle Sheet2 A61 leave blank for single coned baffle Sheet2 A64 leave blank for single coned baffle Sheet2 F84 Enter S for a standard cone, H for a holed cone, or N if there is no cone. A "holed cone" is one with dozens of small holes drill into it and then enclosed with more metal. This reduces the return wave for less pre-powerband power dip and more over-rev. It makes the engine less pipey and is a good option for street and trail bikes. Sheet2 D85 Automatic transfer of the correct pressure change #s to column M. This is only for a single angle baffle. You don't have to enter or delete anything if this option is selected because everything is automated. Sheet2 D86 Use this if designing a multi angled baffle. Sheet2 A87 make it close to the calculated value at top right of this sheet Sheet2 D87 Use this for the increasing angle baffle calculated to the right. 60mm - 300mm is the allowable range. No manual changes are needed when this is selected. This shifts the power peak to lower RPM. Sheet2 G87 1st cones beginning inner diameter Sheet2 D88 Use this for the decreasing angle baffle calculated to the right. 60mm - 300mm is the allowable range. No manual changes are needed when this is selected. This shifts the power peak to higher RPM. Sheet2 G94 1st cones beginning inner diameter Sheet2 A98 This calculates the needed hole diameter and # of holes to reduce the baffle wave strength 100%, 50%, and 30%. Blair had good results reducing his baffle return wave by 29%. That eliminated the pre-powerband power dip and gave the engine much more over-rev and more power at high RPM. He said it was a modification common to single gear karts. This only calculates for the first 100mm but you can see the rate of hole # reduction needed to be able to guesstimate the # of holes needed for baffles longer than 100mm. Sheet2 G111 this shouldn't exceed the volume at N76 Sheet 3 CommentsSheet3 AJ1 wave sum Sheet3 AL1 starting at transfer port opening Sheet3 AS1 starting at exhaust port opening Sheet3 E2 500 to 700 degrees Celsius Sheet3 F9 .45-2.1ms is its allowable range Sheet3 AR17 5D/6D/7D start at EO, not at TO Sheet3 AE18 wave strength Sheet3 AC40 wave strength Sheet3 BA48 sum of secondary waves Sheet3 BA49 multiplier of secondary waves Sheet3 BA50 % of exhaust wave Sheet3 W87 sum of exhaust wave Sheet3 BB140 "@ transfers open " Sheet3 AU141 sync to RPM at E150 Sheet3 AU142 graph time + TO time Sheet3 A143 leave blank if unknown Sheet3 F145 this happens when the diffuser is too long for the grapher. Sheet3 L147 Entering Y means the secondary waves will be combined with the primary waves for the final graph result of the return waves. Set it as N if the engine doesn't have a reed valve. Sheet3 AU147 reduce to move crossover to left, and increase to move it to the right Sheet3 G148 Error message displays when the RPM at E150 isn't within E180 to M180. Sheet3 U150 BDC to TC wave Sheet3 E151 distance from piston to beginning of diffuser Sheet3 AA153 end-.62/500 Sheet3 E155 belly length Sheet3 AA157 end +1.1/700 Sheet3 S160 wave at TC Sheet3 E161 times below are milliseconds after exhaust port opening Sheet3 AB166 positive wave till EC Sheet3 T167 wave strength 1 segment before EC Sheet3 E178 modified diff start when the waves overlap Sheet3 L179 from sheet 1 C6 Sheet3 M181 Pipe power #'s from E187, to be entered [after every RPM change at E150] if your Excel can't use the macro button at H185 Sheet3 BS181 Pipe power #'s from E187 Sheet3 M182 Intake values Sheet3 BS182 Intake values Sheet3 M183 Trapping values Sheet3 BS183 Trapping values Sheet3 I186 Adjust this # so that the blue power graph is above the red and green graphs. Click Auto-Graph after changing it. This allows you to clearly see the intake and trapping graphs also. Yes it changes the power #s but they only exist as a point of reference to see the difference between different designs. This program doesn't try to guess the final engine power. Sheet3 F190 Average of horsepower #s that are above 1/4 of peak power Sheet3 G190 RPM range of HP #s above 1/4 of peak power Sheet3 E214 BMEP pipe power Sheet3 BC214 BMEP pipe power Sheet3 E215 HP pipe power Sheet3 BC215 HP pipe power Sheet3 N220 RPM spread of power above 1/4 the peak power Sheet3 G248 If left blank then it becomes pipe end of powerband RPM from sheet 1 C2. Sheet3 G249 circumference in meters Sheet3 V292 Powerband over 1/8 of the peak power Sheet 4 CommentsSheet4 I1 mm port width of one aux port of a 3 port exhaust. Don't bother with this unless you are going to click the Calculate button at I8. Sheet4 J1 Change this on sheet 1 C5 if you want the top RPM of the graph to be different. Sheet4 I3 mm port width on paper trace (1.12x that of straight across). For a bridged port measure the max width and subtract the width of the bridge. Don't bother with this unless you are going to click the Calculate button at I8. Sheet4 L3 milleseconds per crank rotation degree Sheet4 S3 cc the piston sucks in raising past transfers Sheet4 J4 allowable stroke range is between 27mm and 86mm Sheet4 I5 Enter 1 for single port, 2 for bridged port, or 3 for a center port with two side auxiliary ports. Don't bother with this unless you are going to click the Calculate button at I8. Sheet4 J5 Start with this the same as what you enter at sheet 1 but then you can change it to see how the output changes. But in the end this and the one at sheet 1 need to be the same. Sheet4 L5 engine compression ratio above exhaust port Sheet4 P5 The time till the exhaust pressure dissipates. Sheet4 J6 mm from top of exhaust port to cylinder top minus deck Sheet4 I7 Enter the data at I2, I4, and I6 and then click on this button if you don't want to measure each width every 1mm down. It just gives an estimate but its fairly close and is good enough for the pipe calculations. Otherwise you can ignore those and the button and measure your port widths and enter them manually from J10 to J43. Sheet4 J7 Enter Y for yes, or N for no expansion chamber. Sheet4 L7 this inludes head volume above TDC Sheet4 N7 Equivalent mm height of head if it was flat topped Sheet4 O7 Height of equivalent cylinder above port Sheet4 J8 Total port width every 1mm down port as measured from a paper trace of port Sheet4 N8 average area over the whole blowdown time Sheet4 O10 reference data for 78mm stroke. Degrees per 1mm piston travel Sheet4 A27 add thickness of sheet metal to inner cone diameter Sheet4 L45 header inner diameter in millimeters Sheet4 N45 10 to 16 psi is typical Sheet4 P45 This is 2.75 times the ideal header diameter but is not to be considered the absolute maximum. Sheet4 J47 This is the % of exhaust pulse time that overlaps the open transfers. Ideally this should be under 20% but what matters the most is the calculation at C49. Sheet4 J49 Less than 100% indicates the exhaust pressure ends after the transfers open. Example: 90% (0.90) means that only 90% of the transfer time before BDC is without limitation due to exhaust pressure. Usually the engine wont rev past the RPM that causes less than 80% (0.80) due to the delay of transfer of intake charge into the cylinder. But if the beginning of the pipe powerband kicks in at an RPM before that which causes 0.80 then it can carry the engine to higher RPM. 0.92 or less should be at peak power RPM of porting. Sheet4 J50 Width of all transfers (w/o boosts) added together in millimeters. 38% of circumference (bore x 3.14) is typical of race engines. Sheet4 L51 This is the normal total transfer width on a race engine Sheet4 A52 If the transfer heights are staggered then use the calculator at G69 to find the value to enter here. Sheet4 I52 Hot transfer port duration Sheet4 J52 Start with this the same as what you enter at sheet 1 but then you can change it to see how the output changes. But in the end this and the one at sheet 1 need to be the same. Sheet4 L52 This is typical transfer width for old style engines with two transfers and a boost port. Sheet4 M52 this row is for transfer capacity from O60 Sheet4 I53 Hot mm above transfer port Sheet4 J53 Distance from top of transfers to deck. If the transfers have staggered heights then use the mini calculator at G69. Sheet4 M53 the inverse of the row above so that 100% transfer capacity is 1.0 Sheet4 J54 Ignore this if your computer uses Macros. Just click the Calculate button. After the graph is complete you can enter any RPM within the dispayed range to see the % exhaust overlay of the transfers at K47 for that RPM. Sheet4 M54 fraction of exhaust free transfer. 1.0 is 100% Sheet4 J55 degrees before BDC Sheet4 M56 When this says "Raise exhaust port" it is because the transfer time has lost more than 90% of its time to exhaust pressure overlay due to inadequate blowdown time or the exhaust pulse hasn't been at least 90% expended by the time the transfers open. Sheet4 C60 Enter the center to center conrod length here. Most bikes have conrods between 2x and 2.1x the stroke. The above port calculations depend on this. Sheet4 O65 This doesn't have the latest update that the porting calculator has and so shouldn't be relied on. This sheet mostly exists to figure out the exhaust pulse duration. Sheet4 G70 Add the two widths together. Sheet4 H70 From top of port to "deck", the point on the cylinder where the top edge of the piston is at TDC. Sheet4 F75 Enter this value at K53 and A52. |