this is by far and away the best vid ive seen describing porting, everyone else just says make your ports larger or polish etc, but never explain why and how it affects performance, so thanks, keen for more videos :) and subbed
Holy cow, these videos are just amazing. I can't believe you have barely a few k subs. I loved this content. Found it really interesting and hope to see more in the future. Cheers, mate. You're doing something great here.
@@AuMechanic hey mate, are you making any new content. You have taught me how to modify 2 strokes and I've just built a 74 cc moby 50vl, built the pipe... Wow shes as ripper now! Thank you for sharing your knowledge!
My friend says that a lot of 2t calculators don’t take into account exhaust temperature and it makes a huge difference in the tuned length. I posted a video using your software showing the difference!
I hope for more videos from you. I am a 2stroke beginner and find your videos extremely helpful. I don’t have the software but your videos still give me a good idea on what I should be doing. I will be keeping an eye out for any new videos. Thank you here from Greensburg, Indiana 🇺🇸
man I just found out about your channel, just in time for me to start my project. this is a goldmine. been a while since you uploaded tho, hope you're well
Hey mate I just started my motorcycle mechanic apprenticeship in Melb and am finiding your vids very useful ! Thanks for uploading and looking forward to more hopefully
Hi, I am Jacques from France, Fantastics vidéos. what knowledge you have !! Very interesting . Congratulations. i will continue to follow your explanations. M any thanks
Yeah all good, I just got a bit bogged down with a new free software I'm writing. It is for the next video which is about squish bands and decided to write a squish velocity calculator for people to use for the purposes but its taken a bit longer then planned. Almost done.
Great Software. Good explanation of how it all comes together. Looking forward to more future video,s. Thanks for this video. Peter. ( Edit ) good to see NO Thumbs down for this video.
Hi Dave, just discovered your channel, very informative. I'm going to make a set of pipes. My question is, the formulas are for straight cones, I need them to be angled/offset for clearance etc. How does this affect the calculations? Cheers Andy
Excellent videos! Im trying to find technical info on how chambers change for multi-cylinder engines. I have a twin cylinder engine where weight and size requirements restrict me to a single expansion chamber.
Sorry I cant help with that as I have never built 2 into 1 pipes myself. I can only estimate you would need to upsize the diameters of the chamber and it would be less than double. Also the tuned length could also depend on the timing you run. Some suggest halving the tuned length but that would only work if you had an exhaust timing of 180 degree.
Hi! I want to thank you for your great work in making this software! I've just uploaded a video of the making of a pipe using your software in combination with using the hydroforming technique. The results are amazing and that is for the most part thanks to you! If you like you can check it out, let me know what you think or if you have any suggestions for the next pipe. Thanks a lot!
Awesome videos! I've only had a flick through them but it's really good the way you walk people through things. Is this software that you created? Looks like something that would be easy to create as a mobile app as well if that was something you were interested in.
I did write the software (in VB6), in fact it is a derivative of the original Basic code written by Professor Gordon Blair published by SAE for 3 stage expansion chambers. I was thinking about a mobile app and it is a good suggestion however there are a few things like printing the plotted cones that lends itself to desktop use at which rate I did not really see any justification for a mobile app. There is also the multiline popup help that I use on all my software that provides contextual help within the software that might be difficult to do in a mobile app and most of the inputs do require some technical help to fill in.
Hi dave! Thank you for sharing your knowledge. I just finished my first pipe, built from scratch, using your program. Bending the diffusor and printing out templates in correct scale was by far the most difficult task in this project, but it turned out great. Question 1, how far into the reflectorcone can i put the bleedpipe without messing things up? Q2, how much bigger do the ID of the silencer need to be relative to the ID of the bleedpipe if i dont want the silencer to change the pressure inside the pipe?
The method of inserting the outlet pipe inserted in to the baffle cone is Gordon Jennings book from the mid 70's with the idea that doing so can reduce the higher frequency sound a bit with no loss of power. So it does not increase performance in anyway and his original purpose of doing it was actually to make the whole exhaust shorter. He states that if done the pipe should be pushed up in to the pipe so that the tip is an inch or so forward of the beginning of the baffle cone section, so the tip of the outlet pipe inside is located some way in to the parallel mid section of pipe. However, the calculations I use in the software as from Prof Gordon Blair papers in the late 90's who makes no mention of this method, and he also has a whole study and designs on silencing that I might go into some time in a video. In short, there are other ways to silence than using Jennings method. As for the pipe diameter Blair states that the pipe Port to Outlet ratio equation accounts for the fact there will be a muffler added to the pipe so you are safe to simply add a muffler to it with it's ID the same as the outlet pipe. Also note there that in another study published in which it is proven that the ID of the pipe is what is critical to bleed of the right amount of pressure and the length of the pipe is only relevant to the effect of the length on the restriction of the pipe, even if the outlet pipe is very short so long as it restriction to gas flow out is equivalent to a longer pipe with a slightly larger IS then it is the same thing to the function of the exhaust. So that all provides some guidelines to design your muffler and pipe around to what best suits the fit to the machine.
We have been missing your videos! I was wondering if you could comment on transfer ports. My Bultaco Montadero has small transfers relative to your smaller engines. Will you comment on crank case volume and how that is a limiting factor. Can the transfers be too big? Some guys have hogged out the cases below the transfers. How does port velocity play between the cases to the transfers?
That's a bit to cover in comment section, crankcase volume or primary compression ratio is possibly a video on the topic itself. On ports and sizes Ill be doing some stuff on that at some stage, and yes ports can be too large and they all need to be sizes correctly in proportion to other ports. The flow in transfer is more critical the closer it gets to the cylinder but down low at the cases matching helps as does increasing the size at that end to aid delivery to the port entrances..
I would care to ask more questions about running motorcycle engines anything evolving motorcycle engines please and you are amazing talking about portions and tunning please make more videos not only on chainsaws yes I want about if have done any lawnmower engines porting and running
Good afternoon to you I hope you are telling well you will never forget about your best buddy beacuse you will carry him in your heart I have been watch and reading books on the measurement on the bends for the pipes you ate talking about in your videos let me say this to you have a great understanding about what you are talking about the length and the measurements of the pipes see if you can find some videos about measuring the sound from point a to point b and how ever many letters or takes to completely finished the pipe measurements thank you kindly for responding back to me today is Thursday july 2 2020
Aumechanic I hope you can show more videos on sound measurements beacuse you will give much more better understanding about what you are talking about and not only the calculations of the pipe being buildt thank you kindly for responding back to me in Canada
Hi Dave. I am interested in researching variable tuned exhaust geometry for use with Rotax 582 type aero engines. Your videos so far have been a goldmine for me thanks. Are you aware of any research or practical work going on with variable geometry? Thanks, Terry, NZ.
Good question, Far as I know there was some work on various means of varying geometry of pipes from moving internal baffle cones to water injection done many years ago but for various reasons they did not take off, one being racing regs probably ruled them out in Karting classes for one and they would likely not last long once you sent oily exhaust gasses through them for some period and moving parts in them gummed up. Variable exhaust port timing seems to have been the favored method as it doesn't just alter effective port timing but also effectively changes trapped compression ratio and blow down time too.
Dear Dave, It would be useful to include a note in the software that you need to enter values with a decimal point and not a comma. A lot of people in Europe are used to putting a comma. The results are then different! What do you think?
The basic design is the same, all that changes is the equation factors used to determine if the pipe is more for peak power or broad range power, the tuned length is not different, its just that MX pipes otherwise known as "Up pipes" or "Snake pipes" generally have longer tapers for broader power and being bent 90 degree around the centre neutral chamber can appear to be shorter.
Videos are interesting and informative. I can get my head around most of the formulas, except for the exhaust port duration. I can't understand why the conrod length affects it. Surely, if the swept length is 50mm and the exhaust port height is 25, the the duration is 180 degrees. 360 degrees, 100mm total piston stroke, 50 mm total port height. 50/100 x 360. Am I missing something?
The Piston movement in mm is not linear to the distance moved by the crank in degrees because the piston moves at varying speeds over a single stroke. So when measuring the port timing by way of using port high measurements a formula is given to provide you the exact value of degrees per piston movement in mm.
Ahh, I see what you mean, I mistakenly thought that the linear movement correlated directly with the crank rotation. Thanks for taking the time to answer.
It is the same regardless of how many cylinders the engine has so long as there is a separate exhaust pipe for each cylinder, just use the dimensions from one of the cylinders in the program to do the calculations.
Question about making an exspansion chamber. If pipe need s to be radically curved for fitment and space restrictions does that need a completely different program to calculate or can you curve a pipe to fit my needs while still using that program your using.
The calculations in the program apply regardless of the pipe having bends so long as you apply 2 rules and that is bends must not shorten the pipe length nor reduce the cross sectional area of the pipe where the bend is. There are a few methods to do this, you can use the old "pie slice" method or use a software like "Cone Layout" to plot the cone bends to paper you then trace to the metal to cut out.
I'm actually in the process of reading Gordon's text from 1995. I'm attempting to replicate his calculations in Microsoft Excel. I just recently found your channel and subscribed. Your content is top notch! Thank you for sharing. I probably missed it somewhere, what is the software/calculator you are using? Is this Gordon's SAE files or something you made? Time to binge out on your content. Thanks again!
Hey Dave. For the sake of experimentation (and entertainment) I am building a supercharged two cycle 650 twin on my TH-cam channel. I don't expect to get massive power, I'm doing this mostly because I'm curious and the opportunity came along. I haven't been able to find any information on this, even though it has been done a few times in the 80s 90s on Jet Skis. There seems to be a lot of opinions about this on forums (mostly related to turbochargers), but most opinions leave a lot to be desired, as when I start reading I quickly realize that most people talking don't understand the basics of a two cycle engine. I'm wondering if the pipe will be somewhat self compensating for the additional intake pressure. Also if there's anything that comes to mind that would be ideal, either exhaust or porting, that would be best suited for forced induction. Quite honestly, I feel like I have a decent grasp on two cycle engines, but with this I just keep going in circles.
@Black Dog I have also worked modifying and experimenting drag racing snowmobiles engines. They are a different beast though, because they use a CVT and are only used at wide open throttle. You can tune them for max power and then adjust your clutching, and other setup, around the power you are making. On most other engines you require a wider powerband. With a jet ski, they have to be able to idle in the water without stalling or idling at 20mph, haha.... and they also need to have a fairly responsive throttle from idle all the way up to the rev limiter. This makes them much harder to tun.
Hello Master, I have an question about the cones. I used your fantastic software for un new exhaust for my Suzuki RM 500 cm3 1983 (motocross). Every things are perfect but it is not straigth ! How to do if I want to pass (curve) in the meedle of the frame ? Every calculs will be false ... Thank you so muche, Jacques
Yes it does, its just that in many cases in regards to the exhaust much of the exhaust header section is cast into manifolds with one outlet so there is no way to use a single pipe formula easily and you would need to use some software that handles such manifolds to design a pipe for one. The tuned lengths of the system remains the same equations based on wave reflection timing but the section diameters of the chamber and outlet ratios are not and it requires some additional factors to account for the number of cylinders filling it.
I'm of the understanding that L1 includes the cylinder port length? If so your tuned length as per your program is always my port length short all the time
Hi sir I have goped bigfoot spindle drive I have 23cc engine without weight tyres is spinning very fast but when I try to ride on it than there is no speed after full throttle what is the reason? I means speed is killed I have checked the contact of spindle to tyre is fine but I cant ride on it please can you advise me
No not yet sorry, I got a bit bogged down writing a squish calculator software which is 99% done and planned to do a video for that as well, then somewhere along the road after a few close friends passing away I lost my motivation a bit. Ill get back to it some time in future.
@@AuMechanic lol accidental 2T pun - being bogged down. Sorry to hear about your friends passings. Just in your own time - this is supposed to be enjoyable not a chore! I look forward to any of your new vids!
Hello there, silly question : How may I shape my final exhaust design? Am I wrong or this fabulous software enable us to design only straight pipes? Thanks in advance, hope you ok!
How are you going to convert a port with a barret in the midlle ? there are 3-4 roundings in it , we call it a butterfly port ... i do not get this sorted out . thx
All my ski vids and pics are on my instagram page with other stuff. (see insta link on my main channel page) I decided to just keep this channel for the mechanics stuff to try to limit YT from reducing exposure as it tends to if content veers off the usual content type.
Hi Frank if you are referring to RHS and IGC, RHS is the "ratio of specific heats" and IGC is "individual gas constant" which in short is the composition of the gasses in the exhaust, if you hold the mouse over them it will give more help. These values are different to air than for exhaust gas and they influence the speed of sound inside the pipe and so effect the tuned length calculation. The default values represent average air fuel ratio and using petrol fuel, for other fuel types that may vary hence I left them adjustable.
Hello sir. Ive been watching your videos with extreme interest. I have a question please. My application is a small scooter. The pipe has to be compact and make one preferably two bends. There is a video online of my engine setup with a quickdraw pipe reving to 21000 rpm. I know im nowhere near that. Maybe 18000 19. Can i have your imput. Thanks
180 degree exhaust timing is pretty average. High 190s is standard for high performance. You can go up to about 210 and it'll still run but not much power at low RPM
Hi, used your fantastic chamber calculator to design a pipe for my bike. Sat down in front of the PC with the Cone Layout v 2.0.5 program which allows you to print out templates to cut from but I've hit a brick wall. My intention is to produce the pipe in segments. For example the L2 cone at 275mm long would be divided into 8 frustums with the appropriate angle at each end, thanks to Cone Layout, to enable it to curve under the engine. My math is no where good enough to work out what the diameter of the cone should be at 7 points along its' length. From you software I have the smallest diameter and largest diameter for the cone but am unable to figure out diameters at 34.4 mm intervals along its' length. I've searched the internet without any luck. Can you point me in the right direction?
Hi Rob, sorry I didn't get to this sooner I was off snow skiing for a few days. I am just working on a method to make this a bit simpler for you to do, there are cone calculators in my software to calc straight line and cone angle conversion which you would use in a round about way to get the figures you need. Ill sort something out by next week and may add some equations to the software and update it as I am sure others will need to do this too. I don't use Cone Layout software myself it was recommended by Niko at Hollaendaren YT channel to use to do bends so this issue was not apparent to me at the time I did my Pipe calc software.
@@AuMechanic No problems, everyone deserves a little time off now and again. I feel a little embarrassed writing this. After trying to nut out how to work out segment sizes and coming up with nothing, then contacting you, I had a bit of an epiphany yesterday and came up with a solution. So I hope you haven't spent too much time on this already. Basically I've created a fairly simple Excel spreadsheet that does the calculations. Enter the cone length, entry and exit diameters and number of segments you want and it calculates the two diameters of each one. I've now got a number of curved paper diffusers of varying shapes as I learn what angles I need so it fits the bike. You are more than welcome to a copy of the spreadsheet. Might be a starting point. Or not.
@@robmiller1514 Glad you sorted it out. As you know by now the equation to get the end diameters is not that complex, it's just I didn't think to add it to the cone calc page in the software but may as well do.
It may be possible although it may be simpler to modify the pipe. To work backwards you would need to accurately measure the straight line tuned length of the pipe you have and from that you could extrapolate the exhaust timing it expects based on the RPM of the engine. Likewise you would need to ensure the area of the port window matched the diameters of the header and stinger pipe diameter factors and that part could be difficult to do an even may not be possible. The height of the port will effect timing so once that is set you are only left with width changes to achieve the right area value and there wont be a lot of room to move there so you may end up not being able to get the port size to the numbers you need to satisfy the pipe diameters even if you get the tuned lengths right. Far easier to modify the pipe so at least if the diameters are close you may only need to adjust the length of the pipe.
i am trying to use a wobbly duct (reduces to 90% port area then back to 100 percent in its length of 2 x bore.) and use your 2t calc but the duct comes out at 94mm long and your calc says it cant be longer than the header. part of the duct will actually be made same construction as the header ie 1mm mild steel. any ideas?
The "wobbly duct" principle only applies to high performance race engines with a high BMEP, being based on modelling of Mach numbers in the port according the the creator of it. I'm a little cold on the idea myself in the absence if any examples of real world improvements it offers that I can find. Be aware the warnings given in the 2t calc are just that, they are advisory only and you can ignore them if you are looking to a specific design outside of standard pipe design.
thanks for reply, ive already modified my cylinder ex duct and tried this wobbly duct but borrowed the first section of the header to get the dimensions right and it seems to have given me a boost. most cylinder ex ducts diverge which is wrong. they should converge. at least that part of his theory works for simple single ex port motors. im gonna build a few pipes with and without the duct and the dyno will tell me whats what.@@AuMechanic
@@T-crisp Ok I would say no change. If you for example reduced to diameters of the pipe including stinger to suit the restrictor hole size rather than based off ex port area you may cause too much back pressure and overheat the piston.
hey dude i have known you for a long time have used your software twice to make a pipes for my 60cc enduro bike :D btw it is simson s51 its fun little machine this out of the way i have got myself a 350 two stroke its izh planeta 3 it is 350 single but has 2 exaust ports that guide to 2 separate headers. originaly it comes with 2 separate exausts but i want to make them merge so i have just a single pipe and muffler any tips on how to calculate the header length or any advice you can give ? tnx in advance btw i have not pulled apart the engine yet so i have not done any mesurements i will most likely playaround and do some cutting and porting wont go for reeds yet
Interesting one Re the header lengths, same as one pipe as the length is dictated by tuned length and that doesn't change regardless of number or ports The only difference will be the diameters, It is much the same as a single bridged exhaust port but with 2 outlets at the head flange.. Calculate the area of each exhaust port, making the header area sized to each one and then double the area of the pipe after the 2 into 1 Also ensuring both header pipes are equal lengths.
my exhaust port has a smaller width at the bottom than at the top. ie the sides are sloped and then a 8mm radius in the bottom corners. your tool is assuming my port width is uniform. how do i get around that? i suppose i could work out the are that is being overestimated and subtract that.
@aljaxon69 A shortcut method would be to simply measure the width of the port up top and the width at the bottom, add the two values together then halve them to get the average width of the whole port and then use the calculator in the software to do the rest using the averaged port width value.
@@AuMechanic the outer edges of the port are curved. but due to being on the edge and acutely angled to the flow the actual are of the curved bits is negligible. ie 5 sq mm at an angle of 50 degrees to flow is nearer 1mm actual area
@@aljaxon69 Oh curved Sorry I thought you meant they where sloping or angled. Ok for curved edges you can use another calculation that deals with "segments" where you separate the curved segment of the port with a straight line to isolate it from the rest of the port, and then calculate the area of the segment, and add that to the area of the rest of the port you have added up without the segment. Same way we do it with the curved top of a port in the software so you can use that function separately using the "Calc Segment Only >>> button" to do the segment and then add that area to the rest calculated assuming a straight edge port.
Hi The short answer is no. Long answer is that the purpose of platinum or iridium over copper is longer life, copper has good conductivity but wears quick , platinum lasts longer but conductivity not as good as copper, iridium last long and has better conductivity than platinum which makes iridium the choice of road vehicles. Racing plugs are gold palladium which has the best conductivity and able to withstand higher temps and compression for racing than copper but are quite expensive.
How does it affect engine preformance if you lower or higher your max. engine rpm chart. My eninge at max. rpm revs to 12500 with no load. My peak power of enigne is at about 8200 rpm. What should i type in RPM chart
Use the maximum RPM figure, it may only rev to 8200 under load at top speed due to the power and torque of the engine now but if you put a pipe on it raising the power then it should rev higher and if you change the gearing then it may be revving even higher again at top speed. You want it to be revving to red line at top speed full throttle.
Hi again ,my bike Yamaha rd350lc 2 (Rz) in Aus has a powervalve system ,can I ask how I should factor this into exhaust port area or any other part of the design ? Thanks again .
@@AuMechanic Thanks mate , I've done exactly that and I'm getting really odd results of the header length , I'm getting a around 65mm and my current standard Yamaha pipes have a header length of 300mm and 65mm seems far too short to me .
@@topfuelteddy Is the header straight ? Measure the header and the diffuser length of your pipe and compare that to the total of the L1, L2, L3 and L4 values to see if that is similar in length up top the mid section. In the 3 stage pipe the diffuser is very long so some of L2 part of the diffuser may constitute part of the header of your pipe.
@@AuMechanic Thanks again , I thought that might be the case of incorporating some of the header into the first diffuser cone as the angles are quite similar . The original header is tapered . Really appreciate your time again .
@@skylp8161 In most cases the flange end will be a bit larger then the port window so just stick with that. Keep in mind when comparing them that that the port window measurement is "chordal" (directly across the port, not flattened out curve shape of the bore.)
The simplest answer it just use a larger and longer muffler on it with more absorption material, so long as it is not more restrictive to the outlet pipe. The long answer is to design a three stage muffler that deals specifically with the bandwidth of sound the engine makes but how to do that will require a whole video or more that I may do in future.
I have a 2 stroke 65cc whipper snipper that I bought new in 2015. Do these use only fixed/static ignition timing?... or do they have a curve based on rpm?? Thanks.
They have some advance, the module is usually incorporated into the coil. A 2T engine has poor efficiency at lower RPM so having the ignition advance in this region improves lower end and very effectively limits peak RPM. However once a 2T engine gets to peak and efficiency rises in particular with an expansion chamber (as it comes in to "tune") you will need to retard the ignition to get it to rev any higher. However if there is no advance added at lower RPM then no need to retard it back as it comes on the peak.
Note if you replace a coil be sure to get the same part number coil, likewise for chainsaws, even though you may see one that looks the same it may not have the same timing module in it and you could end up having it not rev out or over rev.
AuMechanic it’s a crap whipper snipper... I bought a new one. So now this engine is of no use. So I was thinking of just detonating it for fun... blow it up. Can I just change the position of the flywheel... will this advance the timing equally everywhere?
@@mareksumguy1887 That be one way to do it with the flywheel keyway out or ground down. Just be aware some of them have a hard limiter in the module in which case it'll just "4 stroke" and wont rev Maybe drill a big hole in the muffler near the outlet to make it flow as they are fairly limiting to RPM. Make sure you get it on video :-)
AuMechanic whats rev limit got to do with anything? I’m gonna load up the engine with a couple of rc airplane propellers. I might even inject some N2O into it... for a bigger bang.
@@AuMechanic well, I'll try to be brief. I was raised on 2 strokes. Iteljet 50, then a ds80 In 1986. All my 2strokes had big ex-chambers. A few years ago I bought a 1981 TS185 for my wife. To me it seemed to run really weird. I was convinced it had a leaky seal. Right crank. I tried to do a full rebuild. Also carb work..Long story short, it still runs weird..... question; is it possible it is just the lack of expansion chamber.?? At WOT, under load, it loses acceleration... I notice the TS 100 has a bulbous ex-chamber but the 185 is smaller longer and starts later....?
@@justinwest9081 Re the crank seal, a leaking crank seal will be the worst at low RPM (more time for the seal to draw in air), so poor idle is the first sign. As to the TS185, (far as I recall) it is an Ag bike for farm work so it has a flat power curve, you could make an improved chamber for it but you would want to raise the port timing a bit too. But to be honest its a good learning bike and once she is comfortable with it maybe look at something more Road Trail rather than spending time and money hotting up the TS, your choice but that's what I would do. The TS100 OTH has rotary disc intake so revs more and a bit more peaky (peak HP at 7000 vs TS185 peak HP at 5600)
@@AuMechanic this is supposedly the trail version. There is a farm version as well. Regardless, I believe your point is still valid that it may be just how the bike runs. Seems odd though. Thank you for your input.
@@justinwest9081 Yep the trail version is probably more the accessories than engine difference. One thing Id do is take the pipe off and burn out the carbon build up in it, specially the silencer, a coked up pipe can really kill power and its old. Maybe just take the silencer out first and run it to see if has a bit more pep, that's a sure sign the pipe needs a burn out.
Imperial is accurate enough however you need to convert fractional values into a decimal to put the values through equations used and metric is already a decimal scale so you may as well convert to it if you are gong to have to do conversions anyway.
There is a metric converter in the input calc window of the software. I've done a video earlier on getting exhaust temp values by calculating BMEP from engine specs th-cam.com/video/cgTGWuVAasU/w-d-xo.html There is a calculator to do this in the input values cal window of the software..
GREAT VIDEO, I already subscribed to the channel. I AM ONLY HAVING A PROBLEM BECAUSE I'M BRAZILIAN AND I DON'T UNDERSTAND ENGLISH VERY WELL, AND SO LOSE A LOT OF IMPORTANT INFORMATION, PLEASE THERE ARE NO VIDEOS IN PORTUGUESE.
Hello, i changed cdi and coils on my Honda MTX 125, then every spark plug are melted after few kilometers, carburetor is ok, before changing cdi engine worked well, changed angle of ignition, and engine still overheating, what kind of problem can be? The reason why I changed cdi and coils is my old coils are burned (i do not know why) and I changed it (CDI, COILS) to another one (not ORIGINAL) i changed timing on rotor, I took out a pin on the crankshaft, and turn forward a rotor for few milimeters to get better timing The new cdi i bought are cdn-yams.schibsted.com/api/v1/adimgs/images/4009444109-cdi-racing-deslimitado-yamaha-dt-tzr-lc-rz.jpg?rule=play is it shitty china or it is good?
Was the engine over heating before you fitted the new ignition, if so then maybe something else is at fault causing that and might have some bearing on the plug melting. You mention you advanced the rotor, be aware that 2 strokes retard the ignition at higher RPM as it comes on the power peak so it may have way too much advance at peak. As for the quality of the ignition you would have to ask around forums perhaps where some may have experience of that brand of ignition.
Hello Master, I have an question about the cones. I used your fantastic software for un new exhaust for my Suzuki RM 500 cm3 1983 (motocross). Every things are perfect but it is not straigth ! How to do if I want to pass (curve) in the meedle of the frame ? Every calculs will be false ... Thank you so muche, Jacques
Hi Jacques there is a program called "Cone Layout" that can help with cutting out patterns to form a bend in the pipe. Alternatively you can use the "Pie Slice" or "Lobster" method, there are many videos on this, it is not hard to do. Basically you cut the pipe at half the angle you want to bend then rotate the 2 parts 180 degree to double that angle which will be your target angle. Doing this retains the centre line length of the pipe through the bend which is important to maintain tuned length.
this is by far and away the best vid ive seen describing porting, everyone else just says make your ports larger or polish etc, but never explain why and how it affects performance, so thanks, keen for more videos :) and subbed
Glad you like the content and I will be doing a good deal more on the how and why of porting.
@@AuMechanic Sounds great! thanks so much!
Holy cow, these videos are just amazing. I can't believe you have barely a few k subs.
I loved this content. Found it really interesting and hope to see more in the future.
Cheers, mate. You're doing something great here.
Thanks for the comment
Cheers
@@AuMechanic hey mate, are you making any new content.
You have taught me how to modify 2 strokes and I've just built a 74 cc moby 50vl, built the pipe...
Wow shes as ripper now!
Thank you for sharing your knowledge!
@@guillermo3471 Glad you found the information useful. Thanks for the comment.
@@AuMechanic that was amazing but once I have all the data how can I make the exhoust with curves because I need it for a vespa
@@bricotico6498 There is software called
"Cone Layout" that can do the layout for cone bends.
My friend says that a lot of 2t calculators don’t take into account exhaust temperature and it makes a huge difference in the tuned length. I posted a video using your software showing the difference!
I hope for more videos from you. I am a 2stroke beginner and find your videos extremely helpful.
I don’t have the software but your videos still give me a good idea on what I should be doing. I will be keeping an eye out for any new videos. Thank you here from Greensburg, Indiana 🇺🇸
man I just found out about your channel, just in time for me to start my project. this is a goldmine. been a while since you uploaded tho, hope you're well
All well
Just had other priorities with a new business over last few yrs but may get some vids up in future.
Awesome stuff , just subscribed.
Can't wait for the rest of this series 🙂
I just wanna say that you are doing awesome work and you are really unlocking a hidden world of power.
Thank you, I do appreciate the comments I get here very much and hope the information is helpful.
Great job man tanks for taking the time to explain this so nicely, looking forward to seeing the next one
Glad you found it useful.
thats a full tank
Hey mate I just started my motorcycle mechanic apprenticeship in Melb and am finiding your vids very useful ! Thanks for uploading and looking forward to more hopefully
Glad you find them interesting.
hope you are weathering the storm comfortably. hope to see you again.
Yes doing fine, hope you are well too
Cheers
Hey don't quit making videos man they are really helpful
Not quitting yet, just been taking a long break from it.
Got more planned.
With the wu flu going on i get it can't wait to see the new releases
Hi, I am Jacques from France, Fantastics vidéos. what knowledge you have !!
Very interesting . Congratulations. i will continue to follow your explanations. M
any thanks
Thank you for the comment.
Haven’t seen a new video in a while. Hope all is well down your way
Yeah all good, I just got a bit bogged down with a new free software I'm writing.
It is for the next video which is about squish bands and decided to write a squish velocity calculator for people to use for the purposes but its taken a bit longer then planned.
Almost done.
Great Software.
Good explanation of how it all comes together.
Looking forward to more future video,s.
Thanks for this video.
Peter.
( Edit ) good to see NO Thumbs down for this video.
Thank you for the comment.
@@AuMechanic
It,s late to say.
But Happy Easter, while there is a couple of hours left, lol.
Anyway good to have a break from work i am guessing ?
Looking forward to your next videos. Great work 😎
Thank's for the comment
Please come back with a new video
Hi Dave, just discovered your channel, very informative.
I'm going to make a set of pipes.
My question is, the formulas are for straight cones, I need them to be angled/offset for clearance etc. How does this affect the calculations?
Cheers
Andy
wondering this as well.
Excellent videos! Im trying to find technical info on how chambers change for multi-cylinder engines. I have a twin cylinder engine where weight and size requirements restrict me to a single expansion chamber.
Sorry I cant help with that as I have never built 2 into 1 pipes myself.
I can only estimate you would need to upsize the diameters of the chamber and it would be less than double.
Also the tuned length could also depend on the timing you run.
Some suggest halving the tuned length but that would only work if you had an exhaust timing of 180 degree.
Hi! I want to thank you for your great work in making this software! I've just uploaded a video of the making of a pipe using your software in combination with using the hydroforming technique. The results are amazing and that is for the most part thanks to you! If you like you can check it out, let me know what you think or if you have any suggestions for the next pipe. Thanks a lot!
I had a look
Turned out pretty good.
@@AuMechanic thanks!!
Awesome videos! I've only had a flick through them but it's really good the way you walk people through things. Is this software that you created? Looks like something that would be easy to create as a mobile app as well if that was something you were interested in.
I did write the software (in VB6), in fact it is a derivative of the original Basic code written by Professor Gordon Blair published by SAE for 3 stage expansion chambers.
I was thinking about a mobile app and it is a good suggestion however there are a few things like printing the plotted cones that lends itself to desktop use at which rate I did not really see any justification for a mobile app.
There is also the multiline popup help that I use on all my software that provides contextual help within the software that might be difficult to do in a mobile app and most of the inputs do require some technical help to fill in.
Hi dave! Thank you for sharing your knowledge. I just finished my first pipe, built from scratch, using your program. Bending the diffusor and printing out templates in correct scale was by far the most difficult task in this project, but it turned out great. Question 1, how far into the reflectorcone can i put the bleedpipe without messing things up? Q2, how much bigger do the ID of the silencer need to be relative to the ID of the bleedpipe if i dont want the silencer to change the pressure inside the pipe?
The method of inserting the outlet pipe inserted in to the baffle cone is Gordon Jennings book from the mid 70's with the idea that doing so can reduce the higher frequency sound a bit with no loss of power. So it does not increase performance in anyway and his original purpose of doing it was actually to make the whole exhaust shorter.
He states that if done the pipe should be pushed up in to the pipe so that the tip is an inch or so forward of the beginning of the baffle cone section, so the tip of the outlet pipe inside is located some way in to the parallel mid section of pipe.
However, the calculations I use in the software as from Prof Gordon Blair papers in the late 90's who makes no mention of this method, and he also has a whole study and designs on silencing that I might go into some time in a video. In short, there are other ways to silence than using Jennings method.
As for the pipe diameter Blair states that the pipe Port to Outlet ratio equation accounts for the fact there will be a muffler added to the pipe so you are safe to simply add a muffler to it with it's ID the same as the outlet pipe.
Also note there that in another study published in which it is proven that the ID of the pipe is what is critical to bleed of the right amount of pressure and the length of the pipe is only relevant to the effect of the length on the restriction of the pipe, even if the outlet pipe is very short so long as it restriction to gas flow out is equivalent to a longer pipe with a slightly larger IS then it is the same thing to the function of the exhaust.
So that all provides some guidelines to design your muffler and pipe around to what best suits the fit to the machine.
@@AuMechanic Ok my pipe is now finished. Its short,fits the bike very well,its suprisingly silent and makes good power. Thank you for the support.
Good Job
Excellent explanation for specific condition
cant wait for another episode !
We have been missing your videos! I was wondering if you could comment on transfer ports. My Bultaco Montadero has small transfers relative to your smaller engines. Will you comment on crank case volume and how that is a limiting factor. Can the transfers be too big? Some guys have hogged out the cases below the transfers. How does port velocity play between the cases to the transfers?
That's a bit to cover in comment section, crankcase volume or primary compression ratio is possibly a video on the topic itself.
On ports and sizes Ill be doing some stuff on that at some stage, and yes ports can be too large and they all need to be sizes correctly in proportion to other ports.
The flow in transfer is more critical the closer it gets to the cylinder but down low at the cases matching helps as does increasing the size at that end to aid delivery to the port entrances..
good videos, are you going to do more?
Yes I will be, cant say when though.
I would care to ask more questions about running motorcycle engines anything evolving motorcycle engines please and you are amazing talking about portions and tunning please make more videos not only on chainsaws yes I want about if have done any lawnmower engines porting and running
Good Thursday morning to you from Canada
Good afternoon to you I hope you are telling well you will never forget about your best buddy beacuse you will carry him in your heart I have been watch and reading books on the measurement on the bends for the pipes you ate talking about in your videos let me say this to you have a great understanding about what you are talking about the length and the measurements of the pipes see if you can find some videos about measuring the sound from point a to point b and how ever many letters or takes to completely finished the pipe measurements thank you kindly for responding back to me today is Thursday july 2 2020
Aumechanic I hope you can show more videos on sound measurements beacuse you will give much more better understanding about what you are talking about and not only the calculations of the pipe being buildt thank you kindly for responding back to me in Canada
Waiting for more!
Hi Dave. I am interested in researching variable tuned exhaust geometry for use with Rotax 582 type aero engines. Your videos so far have been a goldmine for me thanks. Are you aware of any research or practical work going on with variable geometry? Thanks, Terry, NZ.
Good question, Far as I know there was some work on various means of varying geometry of pipes from moving internal baffle cones to water injection done many years ago but for various reasons they did not take off, one being racing regs probably ruled them out in Karting classes for one and they would likely not last long once you sent oily exhaust gasses through them for some period and moving parts in them gummed up.
Variable exhaust port timing seems to have been the favored method as it doesn't just alter effective port timing but also effectively changes trapped compression ratio and blow down time too.
hi will you be continuing the videos on the 'how to' of 2 stroke porting ?
Dear Dave, It would be useful to include a note in the software that you need to enter values with a decimal point and not a comma. A lot of people in Europe are used to putting a comma. The results are then different! What do you think?
I've had a play with your software, all looks understandable. How does this correspond to shorter expansion chambers like that of motocross bikes?
The basic design is the same, all that changes is the equation factors used to determine if the pipe is more for peak power or broad range power, the tuned length is not different, its just that MX pipes otherwise known as "Up pipes" or "Snake pipes" generally have longer tapers for broader power and being bent 90 degree around the centre neutral chamber can appear to be shorter.
Videos are interesting and informative.
I can get my head around most of the formulas, except for the exhaust port duration.
I can't understand why the conrod length affects it.
Surely, if the swept length is 50mm and the exhaust port height is 25, the the duration is 180 degrees.
360 degrees, 100mm total piston stroke, 50 mm total port height. 50/100 x 360.
Am I missing something?
The Piston movement in mm is not linear to the distance moved by the crank in degrees because the piston moves at varying speeds over a single stroke.
So when measuring the port timing by way of using port high measurements a formula is given to provide you the exact value of degrees per piston movement in mm.
Ahh, I see what you mean, I mistakenly thought that the linear movement correlated directly with the crank rotation.
Thanks for taking the time to answer.
Really appreciate this, so interesting.can I ask does the calculation works ok for 2 cylinder engines ? Thanks
It is the same regardless of how many cylinders the engine has so long as there is a separate exhaust pipe for each cylinder, just use the dimensions from one of the cylinders in the program to do the calculations.
Thanks , by any chance have you ever done any calcs for a Yamaha rd350lc ypvs , was it the Rz in Aus ? Appreciate your time .
Question about making an exspansion chamber. If pipe need s to be radically curved for fitment and space restrictions does that need a completely different program to calculate or can you curve a pipe to fit my needs while still using that program your using.
The calculations in the program apply regardless of the pipe having bends so long as you apply 2 rules and that is bends must not shorten the pipe length nor reduce the cross sectional area of the pipe where the bend is. There are a few methods to do this, you can use the old "pie slice" method or use a software like "Cone Layout" to plot the cone bends to paper you then trace to the metal to cut out.
I'm actually in the process of reading Gordon's text from 1995. I'm attempting to replicate his calculations in Microsoft Excel. I just recently found your channel and subscribed. Your content is top notch! Thank you for sharing. I probably missed it somewhere, what is the software/calculator you are using? Is this Gordon's SAE files or something you made? Time to binge out on your content. Thanks again!
HiYes the software is derived from Gordon Blairs equations for 3 stage chambers as per his later publications.
No changes to it.
@@AuMechanic if publically available, can I ask where I might be able to acquire the software? Thanks for the reply.
@@Woodman_Custom_Sawing
There is a link in the description section under the video to get the software, its freeware.
@@AuMechanic thank you kindly sir. Much appreciated! I hope you are doing well in AU with all the fires.
Hey Dave.
For the sake of experimentation (and entertainment) I am building a supercharged two cycle 650 twin on my TH-cam channel. I don't expect to get massive power, I'm doing this mostly because I'm curious and the opportunity came along.
I haven't been able to find any information on this, even though it has been done a few times in the 80s 90s on Jet Skis. There seems to be a lot of opinions about this on forums (mostly related to turbochargers), but most opinions leave a lot to be desired, as when I start reading I quickly realize that most people talking don't understand the basics of a two cycle engine.
I'm wondering if the pipe will be somewhat self compensating for the additional intake pressure. Also if there's anything that comes to mind that would be ideal, either exhaust or porting, that would be best suited for forced induction. Quite honestly, I feel like I have a decent grasp on two cycle engines, but with this I just keep going in circles.
@Black Dog I have also worked modifying and experimenting drag racing snowmobiles engines. They are a different beast though, because they use a CVT and are only used at wide open throttle. You can tune them for max power and then adjust your clutching, and other setup, around the power you are making. On most other engines you require a wider powerband.
With a jet ski, they have to be able to idle in the water without stalling or idling at 20mph, haha.... and they also need to have a fairly responsive throttle from idle all the way up to the rev limiter. This makes them much harder to tun.
Hello Master,
I have an question about the cones. I used your fantastic software for un new exhaust for my Suzuki RM 500 cm3 1983 (motocross).
Every things are perfect but it is not straigth ! How to do if I want to pass (curve) in the meedle of the frame ?
Every calculs will be false ... Thank you so muche, Jacques
Very nice your video
Apologies on my ignorance, but can these principles/theories/modifications/etc. be applied to marine 2 stokes?
Yes it does, its just that in many cases in regards to the exhaust much of the exhaust header section is cast into manifolds with one outlet so there is no way to use a single pipe formula easily and you would need to use some software that handles such manifolds to design a pipe for one.
The tuned lengths of the system remains the same equations based on wave reflection timing but the section diameters of the chamber and outlet ratios are not and it requires some additional factors to account for the number of cylinders filling it.
@@AuMechanic Thanks for the reply!🙂👍🏻
I'm of the understanding that L1 includes the cylinder port length? If so your tuned length as per your program is always my port length short all the time
The software simply subtracts the port length from L1
Since port length is not know until you put it in the software.
What about exhaust boost ports? Should we include them?
Yes include all exhaust ports in area calculation.
Can I make a center bleed pipe with your software? I don’t see any option to choose from center or end or side bleed
Hi sir I have goped bigfoot spindle drive I have 23cc engine without weight tyres is spinning very fast but when I try to ride on it than there is no speed after full throttle what is the reason?
I means speed is killed I have checked the contact of spindle to tyre is fine but I cant ride on it please can you advise me
Is there a video on the mentioned time area targets & analysis?
No not yet sorry, I got a bit bogged down writing a squish calculator software which is 99% done and planned to do a video for that as well, then somewhere along the road after a few close friends passing away I lost my motivation a bit. Ill get back to it some time in future.
@@AuMechanic lol accidental 2T pun - being bogged down.
Sorry to hear about your friends passings.
Just in your own time - this is supposed to be enjoyable not a chore!
I look forward to any of your new vids!
@@joshuaharrison9331 Cheers Josh
Hello there, silly question : How may I shape my final exhaust design? Am I wrong or this fabulous software enable us to design only straight pipes? Thanks in advance, hope you ok!
You can use the software Cone Layout to make bends
How are you going to convert a port with a barret in the midlle ? there are 3-4 roundings in it , we call it a butterfly port ... i do not get this sorted out .
thx
Hi, a bit late to ask but do you plan on uploading any skiing videos this year?
All my ski vids and pics are on my instagram page with other stuff. (see insta link on my main channel page)
I decided to just keep this channel for the mechanics stuff to try to limit YT from reducing exposure as it tends to if content veers off the usual content type.
What are those other coefficient and ratio variables all about? Are the defaults the recommended values?
Hi Frank if you are referring to RHS and IGC, RHS is the "ratio of specific heats" and IGC is "individual gas constant" which in short is the composition of the gasses in the exhaust, if you hold the mouse over them it will give more help.
These values are different to air than for exhaust gas and they influence the speed of sound inside the pipe and so effect the tuned length calculation.
The default values represent average air fuel ratio and using petrol fuel, for other fuel types that may vary hence I left them adjustable.
Very interesting
Hello sir. Ive been watching your videos with extreme interest. I have a question please. My application is a small scooter. The pipe has to be compact and make one preferably two bends. There is a video online of my engine setup with a quickdraw pipe reving to 21000 rpm. I know im nowhere near that. Maybe 18000 19. Can i have your imput. Thanks
The pipe may have a shorter tuned length to stock to run at higher RPM, but the engine may also have ignition module that limits peak RPM.
Hi Dave..! Exhaust port oppening time of my own made engine is nearly 180 degrees.Can I start my engine.pls advise me.
180 degree exhaust timing is pretty average.
High 190s is standard for high performance.
You can go up to about 210 and it'll still run but not much power at low RPM
RIP, Dave
Dave who ?
Not this Dave
dope videos....
Hi, used your fantastic chamber calculator to design a pipe for my bike. Sat down in front of the PC with the Cone Layout v 2.0.5 program which allows you to print out templates to cut from but I've hit a brick wall. My intention is to produce the pipe in segments. For example the L2 cone at 275mm long would be divided into 8 frustums with the appropriate angle at each end, thanks to Cone Layout, to enable it to curve under the engine. My math is no where good enough to work out what the diameter of the cone should be at 7 points along its' length. From you software I have the smallest diameter and largest diameter for the cone but am unable to figure out diameters at 34.4 mm intervals along its' length. I've searched the internet without any luck. Can you point me in the right direction?
Hi Rob, sorry I didn't get to this sooner I was off snow skiing for a few days.
I am just working on a method to make this a bit simpler for you to do, there are cone calculators in my software to calc straight line and cone angle conversion which you would use in a round about way to get the figures you need.
Ill sort something out by next week and may add some equations to the software and update it as I am sure others will need to do this too.
I don't use Cone Layout software myself it was recommended by Niko at Hollaendaren YT channel to use to do bends so this issue was not apparent to me at the time I did my Pipe calc software.
@@AuMechanic No problems, everyone deserves a little time off now and again. I feel a little embarrassed writing this. After trying to nut out how to work out segment sizes and coming up with nothing, then contacting you, I had a bit of an epiphany yesterday and came up with a solution. So I hope you haven't spent too much time on this already.
Basically I've created a fairly simple Excel spreadsheet that does the calculations. Enter the cone length, entry and exit diameters and number of segments you want and it calculates the two diameters of each one.
I've now got a number of curved paper diffusers of varying shapes as I learn what angles I need so it fits the bike. You are more than welcome to a copy of the spreadsheet. Might be a starting point. Or not.
@@robmiller1514
Glad you sorted it out.
As you know by now the equation to get the end diameters is not that complex, it's just I didn't think to add it to the cone calc page in the software but may as well do.
Cheers
Thank's for the comment
Hey man, how do i accurately measure the exhaust temp? Thanks
Aside from using the software to calculate estimated Temp from BMEP you would need to us an EGT gauge to measure it accurately.
@@AuMechanic Thanks, ill try the software and see what will happen
when coming next video
Soon I hope.
could you edit how the compression ratio corrected on both engines and what better rate?
I am in the process of doing a video on squish band design and will cover a bit about compression ratio in it.
What if my port doesnt have that rounded area? Greetings from germany!
Doesn't matter, so long as you can calculate the area of the port then you can convert that to a diameter using the software.
How have you been its been a couple of yrs
Im good thanks.
A few life changes Ive had to stop doing videos for a while but I will get back to it someday.
Would it be possible to reverse engineer a pipe by porting the cylinder to work with the pipe.
It may be possible although it may be simpler to modify the pipe.
To work backwards you would need to accurately measure the straight line tuned length of the pipe you have and from that you could extrapolate the exhaust timing it expects based on the RPM of the engine.
Likewise you would need to ensure the area of the port window matched the diameters of the header and stinger pipe diameter factors and that part could be difficult to do an even may not be possible.
The height of the port will effect timing so once that is set you are only left with width changes to achieve the right area value and there wont be a lot of room to move there so you may end up not being able to get the port size to the numbers you need to satisfy the pipe diameters even if you get the tuned lengths right.
Far easier to modify the pipe so at least if the diameters are close you may only need to adjust the length of the pipe.
i am trying to use a wobbly duct (reduces to 90% port area then back to 100 percent in its length of 2 x bore.) and use your 2t calc but the duct comes out at 94mm long and your calc says it cant be longer than the header. part of the duct will actually be made same construction as the header ie 1mm mild steel. any ideas?
The "wobbly duct" principle only applies to high performance race engines with a high BMEP, being based on modelling of Mach numbers in the port according the the creator of it.
I'm a little cold on the idea myself in the absence if any examples of real world improvements it offers that I can find.
Be aware the warnings given in the 2t calc are just that, they are advisory only and you can ignore them if you are looking to a specific design outside of standard pipe design.
thanks for reply, ive already modified my cylinder ex duct and tried this wobbly duct but borrowed the first section of the header to get the dimensions right and it seems to have given me a boost. most cylinder ex ducts diverge which is wrong. they should converge. at least that part of his theory works for simple single ex port motors. im gonna build a few pipes with and without the duct and the dyno will tell me whats what.@@AuMechanic
Is there any way to account for a restrictor plate in the software? It's for a yamaha kt100j engine
Is the plate in the intake or exhaust ?
@@AuMechanic in the exhaust
@@T-crisp Ok
I would say no change.
If you for example reduced to diameters of the pipe including stinger to suit the restrictor hole size rather than based off ex port area you may cause too much back pressure and overheat the piston.
hey dude i have known you for a long time have used your software twice to make a pipes for my 60cc enduro bike :D btw it is simson s51 its fun little machine this out of the way i have got myself a 350 two stroke its izh planeta 3 it is 350 single but has 2 exaust ports that guide to 2 separate headers. originaly it comes with 2 separate exausts but i want to make them merge so i have just a single pipe and muffler any tips on how to calculate the header length or any advice you can give ? tnx in advance btw i have not pulled apart the engine yet so i have not done any mesurements i will most likely playaround and do some cutting and porting wont go for reeds yet
Interesting one
Re the header lengths, same as one pipe as the length is dictated by tuned length and that doesn't change regardless of number or ports
The only difference will be the diameters, It is much the same as a single bridged exhaust port but with 2 outlets at the head flange..
Calculate the area of each exhaust port, making the header area sized to each one and then double the area of the pipe after the 2 into 1
Also ensuring both header pipes are equal lengths.
@@AuMechanic much tnx. One day when engine is done I will show it to you. Very appreciated !!
Made a pipe using this program. Works perfectly. You can see it on my facebook page "Stainplicity"
Glad to hear it works well, I checked out the video
Is this the one ?facebook.com/pg/Stainplicity/posts/
@@AuMechanic Yeah, I have more videos but this is the best one. You can hear all the power band.
@@AuMechanic Gonna make some more exhausts for different engines in the future.
my exhaust port has a smaller width at the bottom than at the top. ie the sides are sloped and then a 8mm radius in the bottom corners. your tool is assuming my port width is uniform. how do i get around that? i suppose i could work out the are that is being overestimated and subtract that.
See comment reply in other video
@aljaxon69 A shortcut method would be to simply measure the width of the port up top and the width at the bottom, add the two values together then halve them to get the average width of the whole port and then use the calculator in the software to do the rest using the averaged port width value.
@@AuMechanic the outer edges of the port are curved. but due to being on the edge and acutely angled to the flow the actual are of the curved bits is negligible. ie 5 sq mm at an angle of 50 degrees to flow is nearer 1mm actual area
@@aljaxon69 Oh curved
Sorry I thought you meant they where sloping or angled.
Ok for curved edges you can use another calculation that deals with "segments" where you separate the curved segment of the port with a straight line to isolate it from the rest of the port, and then calculate the area of the segment, and add that to the area of the rest of the port you have added up without the segment. Same way we do it with the curved top of a port in the software so you can use that function separately using the "Calc Segment Only >>> button" to do the segment and then add that area to the rest calculated assuming a straight edge port.
@@AuMechanic thx ill have a look.
Tnk you for video
And thank you for the comment.
@@AuMechanic no problem :)
Does the iridium spark plug increase performance on two stroke?
Hi
The short answer is no.
Long answer is that the purpose of platinum or iridium over copper is longer life, copper has good conductivity but wears quick , platinum lasts longer but conductivity not as good as copper, iridium last long and has better conductivity than platinum which makes iridium the choice of road vehicles.
Racing plugs are gold palladium which has the best conductivity and able to withstand higher temps and compression for racing than copper but are quite expensive.
@@AuMechanic Thank you so much
How does it affect engine preformance if you lower or higher your max. engine rpm chart. My eninge at max. rpm revs to 12500 with no load. My peak power of enigne is at about 8200 rpm. What should i type in RPM chart
Use the maximum RPM figure, it may only rev to 8200 under load at top speed due to the power and torque of the engine now but if you put a pipe on it raising the power then it should rev higher and if you change the gearing then it may be revving even higher again at top speed.
You want it to be revving to red line at top speed full throttle.
@@AuMechanic thanks for explanation. 😀
Hi again ,my bike Yamaha rd350lc 2 (Rz) in Aus has a powervalve system ,can I ask how I should factor this into exhaust port area or any other part of the design ? Thanks again .
Use the fully open dimensions for area and timing.
@@AuMechanic Thanks mate , I've done exactly that and I'm getting really odd results of the header length , I'm getting a around 65mm and my current standard Yamaha pipes have a header length of 300mm and 65mm seems far too short to me .
@@topfuelteddy Is the header straight ?
Measure the header and the diffuser length of your pipe and compare that to the total of the L1, L2, L3 and L4 values to see if that is similar in length up top the mid section. In the 3 stage pipe the diffuser is very long so some of L2 part of the diffuser may constitute part of the header of your pipe.
@@AuMechanic Thanks again , I thought that might be the case of incorporating some of the header into the first diffuser cone as the angles are quite similar .
The original header is tapered . Really appreciate your time again .
Hello, does reed valve affect exhaust dimensions?
No it doesnt.
@@AuMechanic thank you! And it is better to have flange same diameter as exhaust port window, or it is better to be bigger? :)
@@skylp8161 In most cases the flange end will be a bit larger then the port window so just stick with that.
Keep in mind when comparing them that that the port window measurement is "chordal" (directly across the port, not flattened out curve shape of the bore.)
@@AuMechanic ok, thanks a lot :)
Hai sir
How can i contact you
Can you please reply to this comment 🙂
You already have
If you have a question about the video ask here.
How can reduce sound of ex chamber
The simplest answer it just use a larger and longer muffler on it with more absorption material, so long as it is not more restrictive to the outlet pipe.
The long answer is to design a three stage muffler that deals specifically with the bandwidth of sound the engine makes but how to do that will require a whole video or more that I may do in future.
I have a 2 stroke 65cc whipper snipper that I bought new in 2015. Do these use only fixed/static ignition timing?... or do they have a curve based on rpm?? Thanks.
They have some advance, the module is usually incorporated into the coil.
A 2T engine has poor efficiency at lower RPM so having the ignition advance in this region improves lower end and very effectively limits peak RPM. However once a 2T engine gets to peak and efficiency rises in particular with an expansion chamber (as it comes in to "tune") you will need to retard the ignition to get it to rev any higher.
However if there is no advance added at lower RPM then no need to retard it back as it comes on the peak.
Note if you replace a coil be sure to get the same part number coil, likewise for chainsaws, even though you may see one that looks the same it may not have the same timing module in it and you could end up having it not rev out or over rev.
AuMechanic it’s a crap whipper snipper... I bought a new one. So now this engine is of no use. So I was thinking of just detonating it for fun... blow it up. Can I just change the position of the flywheel... will this advance the timing equally everywhere?
@@mareksumguy1887
That be one way to do it with the flywheel keyway out or ground down. Just be aware some of them have a hard limiter in the module in which case it'll just "4 stroke" and wont rev
Maybe drill a big hole in the muffler near the outlet to make it flow as they are fairly limiting to RPM.
Make sure you get it on video :-)
AuMechanic whats rev limit got to do with anything? I’m gonna load up the engine with a couple of rc airplane propellers. I might even inject some N2O into it... for a bigger bang.
I have a question I cannot find an answer to. But you might have some input. How can I contact you?
See the about tab on my channel page that has the Email, or just put your questions here which I prefer as answering can be helpful to others.
@@AuMechanic well, I'll try to be brief. I was raised on 2 strokes. Iteljet 50, then a ds80 In 1986. All my 2strokes had big ex-chambers. A few years ago I bought a 1981 TS185 for my wife. To me it seemed to run really weird. I was convinced it had a leaky seal. Right crank. I tried to do a full rebuild. Also carb work..Long story short, it still runs weird..... question; is it possible it is just the lack of expansion chamber.?? At WOT, under load, it loses acceleration... I notice the TS 100 has a bulbous ex-chamber but the 185 is smaller longer and starts later....?
@@justinwest9081 Re the crank seal, a leaking crank seal will be the worst at low RPM (more time for the seal to draw in air), so poor idle is the first sign.
As to the TS185, (far as I recall) it is an Ag bike for farm work so it has a flat power curve, you could make an improved chamber for it but you would want to raise the port timing a bit too.
But to be honest its a good learning bike and once she is comfortable with it maybe look at something more Road Trail rather than spending time and money hotting up the TS, your choice but that's what I would do. The TS100 OTH has rotary disc intake so revs more and a bit more peaky (peak HP at 7000 vs TS185 peak HP at 5600)
@@AuMechanic this is supposedly the trail version. There is a farm version as well. Regardless, I believe your point is still valid that it may be just how the bike runs. Seems odd though. Thank you for your input.
@@justinwest9081 Yep the trail version is probably more the accessories than engine difference. One thing Id do is take the pipe off and burn out the carbon build up in it, specially the silencer, a coked up pipe can really kill power and its old. Maybe just take the silencer out first and run it to see if has a bit more pep, that's a sure sign the pipe needs a burn out.
Only mm/*C not imperial? How does one arrive at an exhaust temp value?
Muh imperial 😂🤣😂🤣 . Imperial is not accurate enough
I am accurate down to .0001 which is .00253937mm so you have nothing to stand on here.
Imperial is accurate enough however you need to convert fractional values into a decimal to put the values through equations used and metric is already a decimal scale so you may as well convert to it if you are gong to have to do conversions anyway.
There is a metric converter in the input calc window of the software.
I've done a video earlier on getting exhaust temp values by calculating BMEP from engine specs th-cam.com/video/cgTGWuVAasU/w-d-xo.html
There is a calculator to do this in the input values cal window of the software..
Hi, how can I get in contact with you?
If prefer you ask any questions in the comment section.
GREAT VIDEO, I already subscribed to the channel. I AM ONLY HAVING A PROBLEM BECAUSE I'M BRAZILIAN AND I DON'T UNDERSTAND ENGLISH VERY WELL, AND SO LOSE A LOT OF IMPORTANT INFORMATION, PLEASE THERE ARE NO VIDEOS IN PORTUGUESE.
You still alive?!
Yes matey, Ill get back to videos at some stage.
Hello, i changed cdi and coils on my Honda MTX 125, then every spark plug are melted after few kilometers, carburetor is ok, before changing cdi engine worked well, changed angle of ignition, and engine still overheating, what kind of problem can be?
The reason why I changed cdi and coils is my old coils are burned (i do not know why) and I changed it (CDI, COILS) to another one (not ORIGINAL)
i changed timing on rotor, I took out a pin on the crankshaft, and turn forward a rotor for few milimeters to get better timing
The new cdi i bought are cdn-yams.schibsted.com/api/v1/adimgs/images/4009444109-cdi-racing-deslimitado-yamaha-dt-tzr-lc-rz.jpg?rule=play
is it shitty china or it is good?
Was the engine over heating before you fitted the new ignition, if so then maybe something else is at fault causing that and might have some bearing on the plug melting.
You mention you advanced the rotor, be aware that 2 strokes retard the ignition at higher RPM as it comes on the power peak so it may have way too much advance at peak.
As for the quality of the ignition you would have to ask around forums perhaps where some may have experience of that brand of ignition.
i dont understand this
Watch the other videos on the series might help understand it.
Hello Master,
I have an question about the cones. I used your fantastic software for un new exhaust for my Suzuki RM 500 cm3 1983 (motocross).
Every things are perfect but it is not straigth ! How to do if I want to pass (curve) in the meedle of the frame ?
Every calculs will be false ... Thank you so muche, Jacques
Hi Jacques
there is a program called "Cone Layout" that can help with cutting out patterns to form a bend in the pipe.
Alternatively you can use the "Pie Slice" or "Lobster" method, there are many videos on this, it is not hard to do.
Basically you cut the pipe at half the angle you want to bend then rotate the 2 parts 180 degree to double that angle which will be your target angle.
Doing this retains the centre line length of the pipe through the bend which is important to maintain tuned length.
@@AuMechanic Hello Master,I understand.
Thank you for your answer. Best regards.