Seems like I’m late to the party but your videos are excellent. I’ve been building motors for many years 35+ but have always excepted the pipes available spending $$ on ones that end up hanging in the shop. Now my grandsons are riding and racing KTM 50SX & YZ65 2021’s and I’ve got the time and equipment to build and modify so this will be soooo helpful to my journey. I’m in the middle of watching ALL your up loads and now I understand how someone can binge watch something! YOUR THE BEST! Thank You for your time and willingness to share your understanding of a somewhat elusive subject for many Motörhead’s. GOD BLESS YOU!🏁💪❤️
Hi Dave, Thanks for looking further into the e^x function :) Don’t feel discouraged by the low number of views, etc. These things take time and there’s not many of us out there these days. The word will get out. Your videos are one of the best resources I’ve stumbled across for explaining the theory and process. I’ve been doing the two-stroke design at BRC Engineering on and off for the last 15 years (with input of my boss who’s been tuning for 30 years). We mostly rely on mimicking other engines, like Aprilia GP stuff for our karting applications. It’s when we branch out into new area of development that we start feeling like we need more technical know-how and to understand the math behind the problems. Your videos have come at a perfect time, as we’re just starting to tune our new engine package which appears to need its own pipe. I’m not sure how many people actually want to go through the trouble of doing the math, but I’m confident that your videos will become regarded as one of the better resources out there… given time. I think the software will be well worth it when combined with the theory you provide in the videos. I look forward to seeing what you’ll post next. Keep up the great work!
Hi Steve Thanks for that head up on the equations that was most helpfull. Thought it warranted a new upload to cover that as well as expand the equations a bit with the sub script and add a few other points on the Blair ratio values too.
I just built a 2-stroke exhaust by guess work. It improved the perfomance at the high end. With this software I expect a much better result! Thanks if you provide it!!
Hi Dave, I have been intrested in 2 stroke since i started repairing/tuning. Your video’s have really helped me understand the basics and the more in depth stuff of 2 strokes. I’ve had so much mind blown moments, i really love learning from you. Please keep up the good work! I would also really love the software and experimenting with exhausts on my bikes!!
I would like the software, but you explained it well enough through your videos that I can calculate everything without it. Thanks for sharing your knowledge with us!!
Dave, I really appreciate what your doing here you are the only one on UA-cam actually teaching me something thanks. As for the software I would like to get a copy. Keep up the good work
Im here a year late, knowing that the software is out, but I just want to say, please, make the software. Its a gods blessing to have a person with such knowledge make something usefull for us hobby tuners. Regards and congrats on almost 6k, Mark
Thank's for the comment. The software is available and free, there is a link in the description section below the video and some more recent videos on using the software.
Yes ...i am interested in a copy of a calculator. I've been watching these videos for a while and they are a wealth of knowledge and I've been looking forward to trying building a pipe myself. Thank you for the information.
Yes we want the free software. Thank you for making these videos. Very informative and I’m trying to use them to design a small pipe for a new rc project.
Hello Dave! Just downloaded your software for tuned pipes. Got a some kind of a weird project in my mind. This might help me design pipes for an old Mercury 500 outboard engine. And I absolutley love how you are expaining the science about the designs. Love the videos. Thank you. Greetings from Sweden.
Man thanks for your time and efforts, it's brilliant what you do. The topic is extremely interesting. All two strokers are great as well as your research.
Rewatching this entire series and wanted to say THANK YOU again for making this information easy to understand. One question concerning bikes with a bmep lower than 6, does the port to mid-section ratio continue to decrease or do you consider 2.125 to be the lower limit? I've used various bmep calculators including the one you supplied and the bmep for my Suzuki A100 is between 5.2-5.7.
The mid section ratio doesn't go below that limit of 2.125 so just stick with that value. Likewise for the estimated exhaust temp when calculating tuned length, 350 C is the lower limit based on BMEP
Thank you! I plan to develop a pipe for the A100 and compare to the pipe dimensions given in the Bridgestone Racing literature for their 100cc rotary valve racer. Similar engine design as my Suzuki so I'm interested to see what the differences are and what can be applied to my bike.
Honorable effort, and comprehesive. If you still comment on this I have a few questions: Given a specific bmep, wich I believe is influential, how sharp header to diffuser angle change could be used without the wave breaks? And ok I settle for that. Really good.
Good question, I would suggest about 3 degrees would be the most you could depart from the pipe area without creating a reflected expansion wave from the initial compression wave based on the fact Jennings and Blair both work in a header pipe with 1 to 2 degree taper at most.
@@AuMechanic want the free calculater where we all can use to do the math geometry beacuse port running would you be able to find a way so that the people that are following you could use the math calculator please
@@domenicomonteleone3055 Thank you for the comment If you look at the description section below the video there is a link to free pipe calculation software I wrote.
Hey Dave. I can't find episode 4,5 and 9 on pipe design? Also you mention that you had a few personal theories deviating from G, Blair's. I'd really like to hear them, is there a video? And yes, would you make a software, I'd want it. Thank you, Andreas.
Hi Andreas Those episodes covered the software for the most part that has changed a bit so are redundant and had pretty low views anyway. I might re order the episode numbers. As for deviating theories to Blair, I've covered a few things in other videos namely the outlet pipe dimensions given of which there is more to the topic such as provided in a paper written by Johannese Van Neikerk on the topic. As well as the timing of the expansion wave off the diffuser cone being separate from the compression wave reflection of the baffle cone that effectively provides 2 tuned lengths not just the one that Blair and Jennings equations dictate. The other issue is the compounding secondary wave reflection theory that rates a whole chapter in his early works circa 1990 but than is reduced to one sentence of vague reference in his later 1996 published works which I find odd.
Yes indeed, the secondary reflection I was struggeling to follow, but you say it is covered in an earlier edition. I should be looking for that. And yes a diffuser tuned length would be more straight forward. Thanks again.
Great videos on 2 smokes.. A great video would be degreeing the port on a chainsaw or small 2 smoke.... I want to "practice" on my 49cc saw before all the important pipes are built.
I've had the book for over a year, and only decided to turn it into a spreadsheet around midnight last night. you bring some good insight. L3=2*L4. L2=3*L4. The books says you can get his prog 6.2v2 expansion chamber software. Do you know if that's still available anywhere?
The software is floating around but it's in DOS I wrote a Windows version using the equations from his 1996 publication which he uses in 6.2v2 The earlier one in 1990 has the code in "basic" in the back of the book and a few programs have used that but I feel it is outdated. Some programs use Jennings equation for a single taper pipe from the 70's and Blairs 1990 equations for the 2 taper diffuser pipe and 1996 equations for the 3 stage but IMO that isn't a good idea. It would not be difficult to have 3 version all based on the 1996 equations and simply adjust the diffuser equations, as I pointed the divisor is the stages is simple enough so for example you could do a 2 stage in which the second taper is half the length of the first one because all it is doing in essence is making a trumpet shape and the divisor is not fixed to any other timing effect. Conversely you could go with that divisor sequence and make more then 3 stages but 3 stages seems adequate. In short a single taper just provides power over a more narrow RPM range than a multi taper.
Hi Dave My calculation on my pipe design has the piston a BDC (at target RPM) before the pulse gets to the 3rd stage diffuser. I was thinking that an increase in suction should occur when the piston no longer aids the movement of the gas through the transfers. The calculation you give from Blaire has the 3rd stage starting a few degrees after BDC. Is this by design of have I stuffed up my calculations ?
I just found this series and it is immensely helpful !! I have some questions regarding twin cylinder motors, do you build a pipe that serves both (or multiple cylinders), using the data gathered from a single cylinder or is it approached differently ? Thanks Steve
I don't know if you have talked about it but my question is calculations of a 2 stage baffle cone how do you go about calculating the angle ? & Is a sharp angle into a slower taper better for broader power or vice versa ? Cheers
I've covered it but it gets buried in the videos I bit. In short the more like a single cone the diffuser is the more narrow the power range of it. A gradual increase in angles from the first cone to the third cone (more trumpet shaped) has to effect of bringing the power on smoother and over a wider range. Keeping in mind the more you spread the power out the lower the peak is.
@@AuMechanic ok then I understood correctly I have one other question for you when you design a pipe do you design it based on the RPM the exhaust Port is capable of flowing? or do you design it for a maximum Target RPM ? Let me expand on this a little I'm building one for a 490 Yamaha according to my port map area & duration it's only capable flowing to 5800 RPM however according to yamaha's spec max power is made at 7000 RPM I'm sure there is more valuable's as to why but in short how would you approach this ?
@@brakhayhurst9214 The tuned length takes into account the point past the rated peak power based on the principle of the baffle cone, which is to plug or push back intake spilling out of the exhaust port and doing that up to and beyond the peak RPM and beyond peak RPM has the effect of pushing so much exhaust back effectively reducing power so acts like a rev limiter after peak as well. Hence the tuned length is set to the maximum RPM of the engine (7,000) If you set tuned length to lower it would the stop the engine form revving to maximum. Also port flow alone does not take into account scavenging effects. Where did you derive the flow over RPM figure from ?
@@AuMechanic I have a port & pipe software called bimotion it statistically calculates the port time/area for a given rpm the idea is to match the calculated statistical timed/area with the modeled timed area mathematically speaking the port window is good for 5800 RPM The 7000 RPM I just did a Google search for the spec of the yz490 that's what Yamaha rated it at
Ok, not sure how bimotion works but if that is referring to gas pressures above the piston by way of flow over time etc then the RPM would probably relate to torque.. Where 7000 RPM refers to HP
Hi Dave, Thanks so much for the time you have spent on this series!! Enjoyed the presentation. Would love the software, though I think i have a pretty good grasp on the figuring.I am setting up to build 2 pipes at first. Both motors have exhaust port on bottom of bike. (50cc class my grandson is competing in). couple questions if you would be so kind as to help.. First, (Im fairly certain i already know the answer, but just verifying). we have done a little clean up on the exhaust port, including a chamfer on the piston side. measurements for port, i assume, are taken in further from the chamfer? Second, any direction you could provide for building curved cones? Most of the pipes the kids are running, have a single diameter pipe wrapping around the motor, then a straight expansion chamber. Would function of pipe be the same if everything started at 2X tuned length, with first length, being at or above port diameter, to make the change in direction, then the second length encompassing the expansion chamber? Again, thanks so much for your time and effort on this subject!
Hi Gerry Port timing is taken form the port itself to top of piston, not including any chamfer, any initial gas flow past a small chamfer is not sufficient in volume and speed to create the compression wave until the port itself is exposed. Same for piston ring hence timing point is taken at top of piston not at top of piston ring that is a bit lower in most cases. Second question, no you cant just double the tuned length, there are losses to the wave as it travels down the pipe length. Having a straight header pipe is fine, just be sure it blends neatly into the start of the diffuser cone with no step or weld bead inside.
so, then i build a curved difuser to get everything going the right direction? that leads to another question.... are the lengths figured at center line? obviously, with the difuser curved, one side is side is shorther than the other (picturing 2 dimensionaly)
Yes all lengths are centre line of the pipe, so to effect a bend at the diffuser of pipe you would use the pie slice method removing a wedge to centre line and reversing it to the other half of the pipe also to ensure the area if the pipe remains the same throughout bends. Which is why straight pipes need to be bent using a mandrel.
G'Day Dave have been following along,Bit confusing so i have to back and look again,,what would help if "YOU TUBE" stopped putting add at import critical moment of calculations,, Yeer i know not much you can do about it but Farrk, Just on a side note picked 2 of them Chinese engine for $63 each free delivery,Came with clutches and 6 tooth drive sprockets, Have plans to build twin engine twin independent drive,spose mud cart,, and was worried not enough go,,,now watching you i can make them a little better with tune exhaust,, thanks for your time doing this,,
Hi Ian, yeah i know what you mean about the ads, always seem to be placed right at the moment of most interest in vids. BTW I have a free software that does all these pipe calculations, might make it simpler for you to use, see the latest video that also has a link in the description section. These vids explaining the calcs are more to demonstrate wha is going on in pipe calculations.
@@AuMechanic Thanks Dave,,but i don't think i will be ripping apart these 2 engines,,well not until i have to,,which is why i got excited when you said they the 49cc engines,,,thinking they may be the same as your's. But thank you,Have a Great day,
Good info the software would be nice but its a lot of work for possibly little response, I think it was A Graham Bells's book the tuned length was to the mid point of the reverse cone whats your thoughts ?
Graham Bells equation is basically the metric version of Gordon Jennings equations, a lot of his content is copied form Jennings "Two Stroke Tuners Handbook" which I started with as a reference to make pipes in the 1980s before Bell and Blair had written books on it. The mid point Jennings uses appears to be a centre point or average point of reflection over the entire baffle cone, where Blair uses the end point of the wave timing in relation to exhaust port timing being the end point of the baffle cone. Keeping in mind that both Jennings and Blair equations differ quite a bit. Blair uses lengths of cones and Jennings works with angles of cones not lengths.. Jennings equations were derived by simply measuring numerous pipes from race bikes etc in 1970s where Blair derives his by more scientific methods in 1990 with his 2 stage diffuser pipe and this 3 stage diffuser pipe in 1997.
See later vid here that shows were to get the software ua-cam.com/video/AppjfX4TdOM/v-deo.html I've got an update version I'm uploading in the next day so wait till then Ill be doing another video on the update version as well.
Dear Sir, I get confused by the figures give by you for the port to mid section ration. I have great books from A. Graham Bell and Gordon Jenning, and they state that the "magic number" for port to mid section ratio is 2,5. Bigger (2,8 to 3) could increase powerband and so to say mid range power. The ratio's you are given are the oposite. Smaller ratio for BP en larger ratio for PP. The only thing i can come up with is that u are talking about a 3 stage diffuser design which, compared to an 1 stage diffuser design has less volume, therefore bigger ratio compensates for the volume loss in the expansion chamber. Is that correct? I hope you understand my "dilemma". Thanks for this great video's!
Be aware that the book written by Gordon Jennings and used by Bell is form the 1970s and is created by Jennings basically reverse engineering his theory by measuring numerous factory racing expansion chambers, so they are a bit out dated and not particularly scientific. Where the equations I use are from Professor Gordon Blair who did numerous scientific experiments to arrive at his equations which are published by SAE as peer reviewed scientific papers and from around 1996
I'm using the new 2t calculator do you think that it might have some problems as you have stated in the beginning of the video? I have a 36cc 2t RC car and want to do a custom pipe for it to give it the best power output,I have taken all the measurements of the motor specs ect from the official site of the zenoa motor .I am enjoying the in-depth knowledge of your videos.
Only report Ive had on the latest version is that putting in RPM over integer value kills it. I didn't envisage anyone using RPM over 36,000 but will sort that out at some stage, other than that it all works. What I was talking about in the videos was doing it manually using windows calculator and there was an error I made in that video.
What are your thoughts on making a tuned exhaust for a detroit diesel two stroke engine. Most folks just run a straight 4 or 5 inch exhaust. Growing up riding two stroke dirt bikes with extreme power bands to now driving larger trucks with two stroke Detroit's that do not have that abrupt power band. Is a tuned exhaust the missing link? Two stroke Detroit's run a supercharger type blower to assist with fuel mixture movement in and out of combustion chambers. After viewing a few of you videos it seems possible to me that a tuned exhaust could over come the need for the blower while still making more power and some wicked sound. Thoughts?
No not too late, I'm getting it done just right now i ski season here and its the biggest season we have had in a decade or more so I'm getting my turns in while it last which will only be by end of September. Cheers.
The software basically includes all the equations in these videos with a few solver equations added. I'm just adding the help files to it before uploading it.
Just wondering if you have something that can calculate the reverse. e.g. I have a pipe of unknown makers, I enter values L1-L7 and D1-D7 so i can get the port timings and rpms which the pipes are suited.
In my 2T Exhaust Calc software see Tools Menu and select Cone Calculators. In there you can calculate the straight centre line lengths of cones. Once you know that you can then add the header and centre chamber length to cone lengths to find out what the tuned length is of the pipe. However even with that known you will have to enter at least 2 values of Port timing, EGT and or RPM to get the tuned length output to match your measurements. Eg if you know EGT and RPM then just adjust the port timing until tuned length output matches. Or if you know EGT and Port timing adjust RPM till tuned length output matches.
@@AuMechanic Hi AuMechanic, Are you in Australia (guess with Au you are) what state are you in. I find your videos very interesting and informative. John
Have a look at the playlist on the main channel page that this video is in, it has 7 videos which cover the steps to designing an expansion chamber to suit your engine.
Aumechanic thank you kindly for responding back to me my question to you is you ate making videos explaining about port tunning could it be possible to make some videos on small engines for gocarts that Race on the race track and more videos on motorcycle racing Engines and regular street bikes beacuse some of these street bikes have headers they have ether two pipes or four pipes I hope you understand what I have been saying about pipes to take the gases out of the engine out from the back of the bike I have forgotten the name mufflers
i see video is3 years back. But anyway on port area calculation , how to measure when there is a yamaha power valve. would you just gofor the average diameter of exaust port?
Do have another question though. Picked up a little ATV for grandkids to race flat track, and the exhaust port has been opened up to a sort of bell mouth, on both sides, giving it sort of a Venturi look. Both sides are nearly equal, with center about 15% smaller. Where do I measure port area? Additionally, unrelated, what effect does reducing crankcase volume have on operation of the engine?
Do you mean the exhaust port at the piston cylinder end of the port or at the outer flange end ? I have a video series on building a chamber with all the equations involved and 2 of the videos covering measuring the exhaust port. See here ua-cam.com/play/PLIxC_wjJqk0rYVOG6EpLU2EaAVWZ2saWA.html Step 4 and 5 videos. Re crankcase volume, decreasing it will raise the primary compression ratio that will increase power however there are some pitfalls involved and probably worthy of a video itself.
Hi Dave. I'd be very interested in getting copy but truthfully I'm not ready to do anything with it until Jan / Feb 2019. Thanks for putting in the efforts that you do. Justin - Perth Aus.
Aumechanic thank you kindly would you be able to make more videos on motorcycle bike engines how to port running and anything else that someone can gain more power on his or hers motorcycle bike thank you kindly for responding back to me from Canada
I have been told there is an error in a formula in Gordon Jennings 2 stroke tuner handbook. (WHICH IS A PHENOMINAL BOOK!) Or is it just someones opinion? Idk. Can someone help here?
I've watched and watched and I want to know how this works in relation to a single pipe twin cylinder. I work in the watercraft field and I've been to a renowned snowmobile pipe builder but those pipes do not translate to jetski's at all. If you could just comment on how 2 into 1 systems would relate that is all I'd need. BTW I love your stuff!!!!!
Good question but I have not had experienced building 2 into 1 pipes for 2 strokes. I can tell you that most of the chamber the same applies as a single such as tuned length calculation and tapers and cones The one difference will be the diameters of the header and outlet pipes. Once you establish the header size then all the rest are calculated in relation to that more or less. One approach would be the measure the stock pipe outlet size and ensure the new ones as at least that size, likewise measure the header and at least you can see what the working ratio is between header and outlet sizes used is. It is possible that the ratio of port to header is the same as a 4t collector ratio, around 1.5 is a start for a merge collector. So the header after it joins from 2 pipes is 1.5 times the area of one port.
Wow, thank you for the fast reply. For our environment a 2 to 1 is all we have room for and we either have water jacketing or water injected into the pipe at various locations. Ours is a very narrow parameter of performance, power is really made from about 5000 to 7500 rpm. I want to take a pipe that was designed for a 900cc twin and adjust it for 1200cc's. BTW I listen to your segments over and over while I work so I can re-familiarizing myself with pipe theory in my sleep. Once again, thank you.
im only a bit late, young enthusiastic welder fabricator here wanting to hit the motorsport industry and offer my services, is this software available?
Is there a simple explanation for what does making a cone longer or shorter do? What does making the diameter smaller or larger do? Stinger lengths? I'm sure it would just be ball park answers without using the math. Just something I've always wondered about.
@@AuMechanic Thanks .. i happen to have a 80's gold rim Husky WR430 .. its the wide gear ratio dualsport model.. and i believe it to be on the original topend still.. although it is old I think it has been stored way more then ridden ..and the last owner could not handle the power .. I had planned to modify a Honda CR500 FMF pipe to fit it ..and still may ..but with your program i can adjust it for the husky VS trial and error..
Hello sir, I wanna make exhaust for my two cylinder two stroke, is it possible to make 2 in 1 ex. chamber? (ex. timing 144-165, bore 73, stroke 73, target RPM 5000-6000)
@@AuMechanic But Question is how to calculate one pipe for two cylinders? For one cylinder is easy but for two is challenging. Length of sections should be same but diameter shouldn't (my guess). Is there some generalick quide because I didnt hear anything about it Thanks a lot for answer
Basically the single taper compared to the multi taper makes the effective range of the pipe more narrow and peaky. For an engine with many gears and a narrow power band a single taper cone would be suitable. I may add it to the software but at this stage there is limited interest in the software to warrant the extra work to do that.
@@AuMechanic I understand. I am thankfull for your reply. I am asking this because of the simplicity of the build. For example one stage exhaust chamber tuned pipes are in use in model rc engines. With only flat back end with muffler setup on the stinger side. I am makind something similar on 70cc engine.
Ok, there are a few applications that only need a narrow band pipe. Many calculators revert to the Gordon Jennings formula when you select a single taper pipe but that design is very old (cira 1970's) and for a 2 stage diffuser they use Blairs early equations in 1990 whereas the 3 stage diffuser uses his later published equation in 1996. My intention was the use the basis of Blairs 2 and 3 stage equations to make a single taper pipe rather than revert to Jennings equations. Jennings equation does work and I used it in the 1980s when I was making race pipes but Blairs pipe equations are derived using far more scientific methods than Jennings used
I’ve just bought a 500 Krauser and need pipes. I was thinking of making them myself but I’m starting to think I should leave it to the experts lol. It’s a little more complicated than I first thought
It is a bit complicated but the flip side of it is that having someone make a custom pipe is very expensive, off the shelf pipes suit stock engines so if your is stock standard then you may be able to get an off the shelf pipe made for it cheaper. The most difficult part of making the pipes is making the cones if you don't have a sheet metal roller to do it but you can get someone else to do that part. After that is is just a matter of welding it up. There are dozens of videos showing the process of physically making a pipe you can refer to.
I may be a tad late, and possibly couldnt use the program anyhow due to my exclusive use of Android. but i need to make two pipes for my engines, make not buy because they have to fit them to my individual aircraft. The local shop doesnt want to design them for a one off pipe. X2
One off pipes are pretty time consuming and no surprise shop is reluctant to make one.. Pipe makers all do volume pipes for stock engines. The problem is once you do any porting and change the exhaust timing and port size the stock pipe is out of tune but there are some mods you can do to a stock pipe to account for port timing changes by re-calculating the tuned length and then shortening the pipe to bring it back into tune.. When I did porting in my business and used to get them to send me the pipe too and modify that to account for the port timing change.
@@AuMechanic The thing is, I'm a bit thick and lazy. Its an RS125 thats going into a race sidecar outfit and we can get your channel on the side for the help
@@AuMechanic Thank you very much! Your video's are very helpful in a lot of ways with the exhaust pipe function. We have good pipe builders in the US but I can't afford them.
hi dave, can you give me some lessons on 2 stroke exhausts, i'm preparing a 3 cylinder car and i need some lessons but i can't find anyone willing to teach me even if i pay
Thank you Dave, hey question for you , I put a 2014 rotax 800 etec in my bushplane and the factory pipe is the wrong shape . Can I just take measurements from the factory pipe and use those values with different bends to achieve the fitment ? If the L and D values remain the same does the shape or routing matter?
The S pipe is basically a U shaped header with an vertical positioned diffuser, followed by a pie slice formed right angled neutral section to a horizontal baffle cone and tail pipe.
I wont be charging anything for it, I've written a fair bit if freeware and enjoy writing code but there has to be some good of it to more than just a few and the comments here seem to suggest it will be, so thank's for commenting.
AuMechanic 8 I've been using Jennings calculation to modify existing aftermarket pipes as close as I can but I think I'm ready to do a scratch built pipe. Currently building an eddy brake dyno for testing
Glad to hear it, eddy current brake dyno's are the most accurate in repeatability. I also used Jennings equations when I started built pipes in the 80s and it was accurate enough, the videos I'm doing now are all based on Blairs later works in 1997 which is based on more scientific methods but Id be greatly interested to see them compared on an accurate Dyno.
Seems like I’m late to the party but your videos are excellent. I’ve been building motors for many years 35+ but have always excepted the pipes available spending $$ on ones that end up hanging in the shop. Now my grandsons are riding and racing KTM 50SX & YZ65 2021’s and I’ve got the time and equipment to build and modify so this will be soooo helpful to my journey. I’m in the middle of watching ALL your up loads and now I understand how someone can binge watch something! YOUR THE BEST! Thank You for your time and willingness to share your understanding of a somewhat elusive subject for many Motörhead’s.
GOD BLESS YOU!🏁💪❤️
Thank you for the comment
Hi Dave,
Thanks for looking further into the e^x function :)
Don’t feel discouraged by the low number of views, etc. These things take time and there’s not many of us out there these days. The word will get out.
Your videos are one of the best resources I’ve stumbled across for explaining the theory and process. I’ve been doing the two-stroke design at BRC Engineering on and off for the last 15 years (with input of my boss who’s been tuning for 30 years). We mostly rely on mimicking other engines, like Aprilia GP stuff for our karting applications. It’s when we branch out into new area of development that we start feeling like we need more technical know-how and to understand the math behind the problems. Your videos have come at a perfect time, as we’re just starting to tune our new engine package which appears to need its own pipe. I’m not sure how many people actually want to go through the trouble of doing the math, but I’m confident that your videos will become regarded as one of the better resources out there… given time. I think the software will be well worth it when combined with the theory you provide in the videos.
I look forward to seeing what you’ll post next. Keep up the great work!
Hi Steve
Thanks for that head up on the equations that was most helpfull.
Thought it warranted a new upload to cover that as well as expand the equations a bit with the sub script and add a few other points on the Blair ratio values too.
I agree, it takes time to disseminate this kind of tech stuff but Dave, you could always go with quality of viewers rather than quantity!
I agree completely Gordon, unfortunately UA-cam algorithms don't see it that way..
Dave, you know you need to do this! 3 months ago I knew nothing about 2 strokes, only 4 strokes so you have been my guide! Love to see the software :)
Thank's for the comment.
At this stage by the comment count it looks likely.
I just built a 2-stroke exhaust by guess work. It improved the perfomance at the high end. With this software I expect a much better result! Thanks if you provide it!!
Did it give that better result?
@@benjaminnurmentaus4232 I just designed a higher stroked crankshaft. Busy busy
@@tinolino58 tell me when it's done maybe even post a video about it or something
Hi Dave,
I have been intrested in 2 stroke since i started repairing/tuning.
Your video’s have really helped me understand the basics and the more in depth stuff of 2 strokes.
I’ve had so much mind blown moments, i really love learning from you. Please keep up the good work!
I would also really love the software and experimenting with exhausts on my bikes!!
Thank's for the comment
Cheers
I would like the software, but you explained it well enough through your videos that I can calculate everything without it. Thanks for sharing your knowledge with us!!
Thanks for the comment Mitchell
The software is available now, if you see newer videos it shows where to download it.
Dave,
I really appreciate what your doing here you are the only one on UA-cam actually teaching me something thanks. As for the software I would like to get a copy. Keep up the good work
Thank's Alik
Im here a year late, knowing that the software is out, but I just want to say, please, make the software. Its a gods blessing to have a person with such knowledge make something usefull for us hobby tuners. Regards and congrats on almost 6k, Mark
Thank's for the comment.
The software is available and free, there is a link in the description section below the video and some more recent videos on using the software.
Sounds to good to miss out on, thanks for your time taken helping others out :)
Cheers Stuart.
Thank you for taking all the time and work to make this knowledge known, NOT an easy task and I do appreciate it.
Yes ...i am interested in a copy of a calculator. I've been watching these videos for a while and they are a wealth of knowledge and I've been looking forward to trying building a pipe myself. Thank you for the information.
Thank's for the comment Matt
The software is available now, if you see newer videos it shows where to download it.
Yes we want the free software. Thank you for making these videos. Very informative and I’m trying to use them to design a small pipe for a new rc project.
Thank's Jarebb, be interested to see the RC engine pipe.
I flew Nitro RC helis for a while.
The software is available now, if you see newer videos it shows where to download it.
I realise this is old clip. I’ve just discovered you. Thanks so much for all this info, it’s great. I want to build my own pipe now!
Hello Dave! Just downloaded your software for tuned pipes. Got a some kind of a weird project in my mind. This might help me design pipes for an old Mercury 500 outboard engine. And I absolutley love how you are expaining the science about the designs. Love the videos. Thank you. Greetings from Sweden.
Love your vids! working through all of them. 3 stage software would be great. Thank you for all your time and effort.
Thank you for the comment, it all helps.
Yes these videos are super helpful and descriptive. I really want the software to start working on a pipe for my 2 stroke opposed vintage sled!
The software is available now, if you see newer videos it shows where to download it.
I want the software! just found all of your videos a week ago, this is excellent.
Thank's Patrick
The software is available now, if you see newer videos it shows where to download it.
Man thanks for your time and efforts, it's brilliant what you do. The topic is extremely interesting. All two strokers are great as well as your research.
Dave, I would like the calculator as well. I have watched all your pipe videos and enjoy learning more and more . Thanks!
Thank's Jason
The 2 stroke pipe software is available now, if you see newer video it shows where to download it.
Thank you for all the effort you've put into this. I'm looking forward to playing with your software for a couple of my old smokers. 👍
Thanks Dave for this,, I'm late to the game but this was incredibly helpful on my build,, I used your manual calculator 👍👍
Glad you found it useful
We will love to see your creativity on the software. Please kindly make it.
I have made it, see the description section above with the link to download the software.
It is freeware.
Rewatching this entire series and wanted to say THANK YOU again for making this information easy to understand. One question concerning bikes with a bmep lower than 6, does the port to mid-section ratio continue to decrease or do you consider 2.125 to be the lower limit? I've used various bmep calculators including the one you supplied and the bmep for my Suzuki A100 is between 5.2-5.7.
The mid section ratio doesn't go below that limit of 2.125 so just stick with that value.
Likewise for the estimated exhaust temp when calculating tuned length, 350 C is the lower limit based on BMEP
Thank you! I plan to develop a pipe for the A100 and compare to the pipe dimensions given in the Bridgestone Racing literature for their 100cc rotary valve racer. Similar engine design as my Suzuki so I'm interested to see what the differences are and what can be applied to my bike.
Be interested to see the differences.
Honorable effort, and comprehesive. If you still comment on this I have a few questions: Given a specific bmep, wich I believe is influential, how sharp header to diffuser angle change could be used without the wave breaks? And ok I settle for that. Really good.
Good question, I would suggest about 3 degrees would be the most you could depart from the pipe area without creating a reflected expansion wave from the initial compression wave based on the fact Jennings and Blair both work in a header pipe with 1 to 2 degree taper at most.
Been searching for thoughts on that for some time now. Thank you.
Another great video and yes I would be very interested in the Software. Thanks for all the info!
Thanks for the comment
The 2 stroke pipe software is available now, if you see newer video it shows where to download it.
Very informative, thanks! The software would be useful for this rookie’s sprint bike project.......
Thank you for the comment Gordon.
The software is available now, if you see newer videos it shows where to download it.
@@AuMechanic want the free calculater where we all can use to do the math geometry beacuse port running would you be able to find a way so that the people that are following you could use the math calculator please
@@domenicomonteleone3055
Thank you for the comment
If you look at the description section below the video there is a link to free pipe calculation software I wrote.
Hey Dave. I can't find episode 4,5 and 9 on pipe design? Also you mention that you had a few personal theories deviating from G, Blair's. I'd really like to hear them, is there a video? And yes, would you make a software, I'd want it. Thank you, Andreas.
Hi Andreas
Those episodes covered the software for the most part that has changed a bit so are redundant and had pretty low views anyway.
I might re order the episode numbers.
As for deviating theories to Blair, I've covered a few things in other videos namely the outlet pipe dimensions given of which there is more to the topic such as provided in a paper written by Johannese Van Neikerk on the topic.
As well as the timing of the expansion wave off the diffuser cone being separate from the compression wave reflection of the baffle cone that effectively provides 2 tuned lengths not just the one that Blair and Jennings equations dictate.
The other issue is the compounding secondary wave reflection theory that rates a whole chapter in his early works circa 1990 but than is reduced to one sentence of vague reference in his later 1996 published works which I find odd.
Yes indeed, the secondary reflection I was struggeling to follow, but you say it is covered in an earlier edition. I should be looking for that. And yes a diffuser tuned length would be more straight forward. Thanks again.
Yes, I want the expansion chamber software. Thanks
Thank's Simon
The software is available now, if you see newer videos it shows where to download it.
To add to Dave's comments at 21:30... when using a Windows 7 calculator you have to push the "Inv" button to reveal the "e^x" feature.
Great videos on 2 smokes.. A great video would be degreeing the port on a chainsaw or small 2 smoke.... I want to "practice" on my 49cc saw before all the important pipes are built.
I will be doing some videos on porting.
Later on ill be getting a few engines to do some demonstrations with.
Awesome!
I've had the book for over a year, and only decided to turn it into a spreadsheet around midnight last night. you bring some good insight. L3=2*L4. L2=3*L4. The books says you can get his prog 6.2v2 expansion chamber software. Do you know if that's still available anywhere?
The software is floating around but it's in DOS
I wrote a Windows version using the equations from his 1996 publication which he uses in 6.2v2
The earlier one in 1990 has the code in "basic" in the back of the book and a few programs have used that but I feel it is outdated.
Some programs use Jennings equation for a single taper pipe from the 70's and Blairs 1990 equations for the 2 taper diffuser pipe and 1996 equations for the 3 stage but IMO that isn't a good idea.
It would not be difficult to have 3 version all based on the 1996 equations and simply adjust the diffuser equations, as I pointed the divisor is the stages is simple enough so for example you could do a 2 stage in which the second taper is half the length of the first one because all it is doing in essence is making a trumpet shape and the divisor is not fixed to any other timing effect.
Conversely you could go with that divisor sequence and make more then 3 stages but 3 stages seems adequate.
In short a single taper just provides power over a more narrow RPM range than a multi taper.
Hi Dave My calculation on my pipe design has the piston a BDC (at target RPM) before the pulse gets to the 3rd stage diffuser. I was thinking that an increase in suction should occur when the piston no longer aids the movement of the gas through the transfers. The calculation you give from Blaire has the 3rd stage starting a few degrees after BDC. Is this by design of have I stuffed up my calculations ?
No that is by design.
I would love the software. I need to design and build a pipe for my Yamaha dt175
I just found this series and it is immensely helpful !!
I have some questions regarding twin cylinder motors, do you build a pipe that serves both (or multiple cylinders), using the data gathered from a single cylinder or is it approached differently ?
Thanks
Steve
I don't know if you have talked about it but my question is calculations of a 2 stage baffle cone how do you go about calculating the angle ?
& Is a sharp angle into a slower taper better for broader power or vice versa ?
Cheers
I've covered it but it gets buried in the videos I bit.
In short the more like a single cone the diffuser is the more narrow the power range of it.
A gradual increase in angles from the first cone to the third cone (more trumpet shaped) has to effect of bringing the power on smoother and over a wider range.
Keeping in mind the more you spread the power out the lower the peak is.
@@AuMechanic ok then I understood correctly I have one other question for you when you design a pipe do you design it based on the RPM the exhaust Port is capable of flowing? or do you design it for a maximum Target RPM ? Let me expand on this a little I'm building one for a 490 Yamaha according to my port map area & duration it's only capable flowing to 5800 RPM however according to yamaha's spec max power is made at 7000 RPM I'm sure there is more valuable's as to why but in short how would you approach this ?
@@brakhayhurst9214
The tuned length takes into account the point past the rated peak power based on the principle of the baffle cone, which is to plug or push back intake spilling out of the exhaust port and doing that up to and beyond the peak RPM and beyond peak RPM has the effect of pushing so much exhaust back effectively reducing power so acts like a rev limiter after peak as well.
Hence the tuned length is set to the maximum RPM of the engine (7,000)
If you set tuned length to lower it would the stop the engine form revving to maximum.
Also port flow alone does not take into account scavenging effects.
Where did you derive the flow over RPM figure from ?
@@AuMechanic I have a port & pipe software called bimotion it statistically calculates the port time/area for a given rpm the idea is to match the calculated statistical timed/area with the modeled timed area mathematically speaking the port window is good for 5800 RPM
The 7000 RPM I just did a Google search for the spec of the yz490 that's what Yamaha rated it at
Ok, not sure how bimotion works but if that is referring to gas pressures above the piston by way of flow over time etc then the RPM would probably relate to torque..
Where 7000 RPM refers to HP
Knackers, your tubes are awesome. How do I get my hands on the calculator?
Ill be making a video about how to use it when its competed so if you're subscribed it'll come up in your YT feed.
Great job on the videos dave and thanks for sharing your knowledge, id definitely like the software mate.
Thanks for the comment Aaron
Hi Dave, Thanks so much for the time you have spent on this series!! Enjoyed the presentation. Would love the software, though I think i have a pretty good grasp on the figuring.I am setting up to build 2 pipes at first. Both motors have exhaust port on bottom of bike. (50cc class my grandson is competing in). couple questions if you would be so kind as to help..
First, (Im fairly certain i already know the answer, but just verifying). we have done a little clean up on the exhaust port, including a chamfer on the piston side. measurements for port, i assume, are taken in further from the chamfer?
Second, any direction you could provide for building curved cones? Most of the pipes the kids are running, have a single diameter pipe wrapping around the motor, then a straight expansion chamber. Would function of pipe be the same if everything started at 2X tuned length, with first length, being at or above port diameter, to make the change in direction, then the second length encompassing the expansion chamber?
Again, thanks so much for your time and effort on this subject!
Hi Gerry
Port timing is taken form the port itself to top of piston, not including any chamfer, any initial gas flow past a small chamfer is not sufficient in volume and speed to create the compression wave until the port itself is exposed.
Same for piston ring hence timing point is taken at top of piston not at top of piston ring that is a bit lower in most cases.
Second question, no you cant just double the tuned length, there are losses to the wave as it travels down the pipe length.
Having a straight header pipe is fine, just be sure it blends neatly into the start of the diffuser cone with no step or weld bead inside.
so, then i build a curved difuser to get everything going the right direction? that leads to another question.... are the lengths figured at center line? obviously, with the difuser curved, one side is side is shorther than the other (picturing 2 dimensionaly)
Yes all lengths are centre line of the pipe, so to effect a bend at the diffuser of pipe you would use the pie slice method removing a wedge to centre line and reversing it to the other half of the pipe also to ensure the area if the pipe remains the same throughout bends.
Which is why straight pipes need to be bent using a mandrel.
G'Day Dave have been following along,Bit confusing so i have to back and look again,,what would help if "YOU TUBE" stopped putting add at import critical moment of calculations,,
Yeer i know not much you can do about it but Farrk,
Just on a side note picked 2 of them Chinese engine for $63 each free delivery,Came with clutches and 6 tooth drive sprockets,
Have plans to build twin engine twin independent drive,spose mud cart,,
and was worried not enough go,,,now watching you i can make them a little better with tune exhaust,,
thanks for your time doing this,,
Hi Ian, yeah i know what you mean about the ads, always seem to be placed right at the moment of most interest in vids.
BTW I have a free software that does all these pipe calculations, might make it simpler for you to use, see the latest video that also has a link in the description section.
These vids explaining the calcs are more to demonstrate wha is going on in pipe calculations.
@@AuMechanic Thanks Dave,,but i don't think i will be ripping apart these 2 engines,,well not until i have to,,which is why i got excited when you said they the 49cc engines,,,thinking they may be the same as your's.
But thank you,Have a Great day,
Good info the software would be nice but its a lot of work for possibly little response, I think it was A Graham Bells's book the tuned length was to the mid point of the reverse cone whats your thoughts ?
Graham Bells equation is basically the metric version of Gordon Jennings equations, a lot of his content is copied form Jennings "Two Stroke Tuners Handbook" which I started with as a reference to make pipes in the 1980s before Bell and Blair had written books on it.
The mid point Jennings uses appears to be a centre point or average point of reflection over the entire baffle cone, where Blair uses the end point of the wave timing in relation to exhaust port timing being the end point of the baffle cone.
Keeping in mind that both Jennings and Blair equations differ quite a bit.
Blair uses lengths of cones and Jennings works with angles of cones not lengths..
Jennings equations were derived by simply measuring numerous pipes from race bikes etc in 1970s where Blair derives his by more scientific methods in 1990 with his 2 stage diffuser pipe and this 3 stage diffuser pipe in 1997.
Id love some software. Love the vids. Very helpful. Thank you
See later vid here that shows were to get the software ua-cam.com/video/AppjfX4TdOM/v-deo.html
I've got an update version I'm uploading in the next day so wait till then
Ill be doing another video on the update version as well.
Dear Sir,
I get confused by the figures give by you for the port to mid section ration. I have great books from A. Graham Bell and Gordon Jenning, and they state that the "magic number" for port to mid section ratio is 2,5. Bigger (2,8 to 3) could increase powerband and so to say mid range power. The ratio's you are given are the oposite. Smaller ratio for BP en larger ratio for PP. The only thing i can come up with is that u are talking about a 3 stage diffuser design which, compared to an 1 stage diffuser design has less volume, therefore bigger ratio compensates for the volume loss in the expansion chamber. Is that correct? I hope you understand my "dilemma".
Thanks for this great video's!
Be aware that the book written by Gordon Jennings and used by Bell is form the 1970s and is created by Jennings basically reverse engineering his theory by measuring numerous factory racing expansion chambers, so they are a bit out dated and not particularly scientific.
Where the equations I use are from Professor Gordon Blair who did numerous scientific experiments to arrive at his equations which are published by SAE as peer reviewed scientific papers and from around 1996
Free software! We could use it for our collegiate engine design competition here in the US.
I'm getting there, should have it done by Sept some time.
The 2 stroke pipe software is available now, if you see newer video it shows where to download it.
I'm using the new 2t calculator do you think that it might have some problems as you have stated in the beginning of the video? I have a 36cc 2t RC car and want to do a custom pipe for it to give it the best power output,I have taken all the measurements of the motor specs ect from the official site of the zenoa motor .I am enjoying the in-depth knowledge of your videos.
Only report Ive had on the latest version is that putting in RPM over integer value kills it.
I didn't envisage anyone using RPM over 36,000 but will sort that out at some stage, other than that it all works.
What I was talking about in the videos was doing it manually using windows calculator and there was an error I made in that video.
What are your thoughts on making a tuned exhaust for a detroit diesel two stroke engine. Most folks just run a straight 4 or 5 inch exhaust. Growing up riding two stroke dirt bikes with extreme power bands to now driving larger trucks with two stroke Detroit's that do not have that abrupt power band. Is a tuned exhaust the missing link? Two stroke Detroit's run a supercharger type blower to assist with fuel mixture movement in and out of combustion chambers. After viewing a few of you videos it seems possible to me that a tuned exhaust could over come the need for the blower while still making more power and some wicked sound. Thoughts?
Not aware of it being done and it probably wont have any effect due to the way 2 stroke diesel engines operate.
Hi Dave..Thank you very much for this technical information sharing. Really appreciate. All regards. Jaco Human
Would be great. Not sure if it's too late or not but if it could happen, yes I would like it. Would be quite helpful.
No not too late, I'm getting it done just right now i ski season here and its the biggest season we have had in a decade or more so I'm getting my turns in while it last which will only be by end of September.
Cheers.
AuMechanic Great! Don't waste the ski season on it though
The software is available now, if you see newer videos it shows where to download it.
Yes! I would love a freeware calculator! :)
The software is available now, if you see newer videos it shows where to download it.
Some design software would be awesome! Just bought my first 2 stroke. needs a proper exhaust
The software basically includes all the equations in these videos with a few solver equations added.
I'm just adding the help files to it before uploading it.
The software is available now, if you see newer videos it shows where to download it.
Just wondering if you have something that can calculate the reverse. e.g. I have a pipe of unknown makers, I enter values L1-L7 and D1-D7 so i can get the port timings and rpms which the pipes are suited.
In my 2T Exhaust Calc software see Tools Menu and select Cone Calculators.
In there you can calculate the straight centre line lengths of cones.
Once you know that you can then add the header and centre chamber length to cone lengths to find out what the tuned length is of the pipe.
However even with that known you will have to enter at least 2 values of Port timing, EGT and or RPM to get the tuned length output to match your measurements.
Eg if you know EGT and RPM then just adjust the port timing until tuned length output matches.
Or if you know EGT and Port timing adjust RPM till tuned length output matches.
Great work Dave. I’d like to use the software if you decide to go ahead.
Thank's Justin
I would really like some good free expansion chamber software.
Thanks for the comment Georgi
Me too!
Yes sir! I would love to be able to make pipes for my 2 smokes..
The software is available now, if you see newer videos it shows where to download it.
@@AuMechanic Hi AuMechanic, Are you in Australia (guess with Au you are) what state are you in. I find your videos very interesting and informative.
John
SoCal Motor Bicycle Racer's want your pipe software for their custom builds. Thanks.
Thank's for the comment, all helps.
The software is available now, if you see newer videos it shows where to download it.
Yes! I would like to have a free pipe calculator software! :)
The software is available now, if you see newer videos it shows where to download it.
Please add me to the list. Thanks for the video!
Ill be uploading a video for it when its is completed so if you are subbed and hit the bell option you will get notified of it.
Almost done.
I would love free expansion chamber software to tune a better exhaust for my Paramotor! :)
Thank;s for the comment.
Software is nearly done
Yes please I want to understand more on expansion chamber design
See the description section under the video.
How i desighn two stroke exhaust for lml star vespa (vintage).
Have a look at the playlist on the main channel page that this video is in, it has 7 videos which cover the steps to designing an expansion chamber to suit your engine.
I am working on a two stroke project right now and would love to have a calculator to use.
See the link in the description section below the video
Aumechanic thank you kindly for responding back to me my question to you is you ate making videos explaining about port tunning could it be possible to make some videos on small engines for gocarts that Race on the race track and more videos on motorcycle racing Engines and regular street bikes beacuse some of these street bikes have headers they have ether two pipes or four pipes I hope you understand what I have been saying about pipes to take the gases out of the engine out from the back of the bike I have forgotten the name mufflers
Watch the other videos that cover all theses topics.
@@AuMechanic Aumechanic I will do ad you say watch other videos thank you kindly for responding back to me
i see video is3 years back. But anyway on port area calculation , how to measure when there is a yamaha power valve. would you just gofor the average diameter of exaust port?
Measurement is the full port size with valve fully open.
How’s the program coming along?
Should have it done sometime this week I hope.
Not rushing, just wanted to make sure I didn’t miss it.
Do have another question though. Picked up a little ATV for grandkids to race flat track, and the exhaust port has been opened up to a sort of bell mouth, on both sides, giving it sort of a Venturi look. Both sides are nearly equal, with center about 15% smaller. Where do I measure port area?
Additionally, unrelated, what effect does reducing crankcase volume have on operation of the engine?
Do you mean the exhaust port at the piston cylinder end of the port or at the outer flange end ?
I have a video series on building a chamber with all the equations involved and 2 of the videos covering measuring the exhaust port.
See here ua-cam.com/play/PLIxC_wjJqk0rYVOG6EpLU2EaAVWZ2saWA.html
Step 4 and 5 videos.
Re crankcase volume, decreasing it will raise the primary compression ratio that will increase power however there are some pitfalls involved and probably worthy of a video itself.
The software is available now, if you see newer videos it shows where to download it.
I would really like to have your software I’ve never seen anything like it
Thank you for the comment.
Software is nearly done.
The software is available now, if you see newer videos it shows where to download it.
Hi Dave. I'd be very interested in getting copy but truthfully I'm not ready to do anything with it until Jan / Feb 2019. Thanks for putting in the efforts that you do. Justin - Perth Aus.
No worries Jason
Thx for the comment
The software is available now, if you see newer videos it shows where to download it.
Hello Dave I would like to get the software for porting and pipe calculator.
See the description section below the video for the link for free pipe calculator.
I would appreciate your efforts to do some free software.
Almost complete Hugh
Had some work to do this week so It'll be up by next week and I'll post a video on how ot use it with links where to download it.
Now ready to download, see newer video.
I am very interested in the software, please let me know.
Hi Jeff
Ill be doing a video on the software when released.
Thank you so much, sorry for the slow response I did not catch your reply until just now
The 2 stroke pipe software is available now, if you see newer video it shows where to download it.
Aumechanic thank you kindly would you be able to make more videos on motorcycle bike engines how to port running and anything else that someone can gain more power on his or hers motorcycle bike thank you kindly for responding back to me from Canada
I will be doing more.
Would like the software thanks Dave
Thank's for the comment Hank.
I have been told there is an error in a formula in Gordon Jennings 2 stroke tuner handbook. (WHICH IS A PHENOMINAL BOOK!)
Or is it just someones opinion? Idk.
Can someone help here?
There are errors in his formula, which one are you referring to.
I've watched and watched and I want to know how this works in relation to a single pipe twin cylinder. I work in the watercraft field and I've been to a renowned snowmobile pipe builder but those pipes do not translate to jetski's at all. If you could just comment on how 2 into 1 systems would relate that is all I'd need. BTW I love your stuff!!!!!
Good question but I have not had experienced building 2 into 1 pipes for 2 strokes.
I can tell you that most of the chamber the same applies as a single such as tuned length calculation and tapers and cones
The one difference will be the diameters of the header and outlet pipes.
Once you establish the header size then all the rest are calculated in relation to that more or less.
One approach would be the measure the stock pipe outlet size and ensure the new ones as at least that size, likewise measure the header and at least you can see what the working ratio is between header and outlet sizes used is.
It is possible that the ratio of port to header is the same as a 4t collector ratio, around 1.5 is a start for a merge collector.
So the header after it joins from 2 pipes is 1.5 times the area of one port.
Wow, thank you for the fast reply. For our environment a 2 to 1 is all we have room for and we either have water jacketing or water injected into the pipe at various locations. Ours is a very narrow parameter of performance, power is really made from about 5000 to 7500 rpm. I want to take a pipe that was designed for a 900cc twin and adjust it for 1200cc's. BTW I listen to your segments over and over while I work so I can re-familiarizing myself with pipe theory in my sleep. Once again, thank you.
im only a bit late, young enthusiastic welder fabricator here wanting to hit the motorsport industry and offer my services, is this software available?
Link is in the description section below the video.
Is there a simple explanation for what does making a cone longer or shorter do? What does making the diameter smaller or larger do? Stinger lengths? I'm sure it would just be ball park answers without using the math. Just something I've always wondered about.
There are more videos here that cover all of those points regarding cones and outlet pipes.
Cool
Dave how can I get a copy of this program. Al in Canada
See the description section below the video for the link to it.
Thanks for upload
I want the free calculator software please.
See the link above in the video description section.
id love to have it and im used to imperial.. but metric rules the rest of the world (and for the most part so much simpler )
Ive got a free software now that does all this, the download info is in the latest video, it also has a imp to metric converter in it.
@@AuMechanic Thanks .. i happen to have a 80's gold rim Husky WR430 .. its the wide gear ratio dualsport model.. and i believe it to be on the original topend still.. although it is old I think it has been stored way more then ridden ..and the last owner could not handle the power .. I had planned to modify a Honda CR500 FMF pipe to fit it ..and still may ..but with your program i can adjust it for the husky VS trial and error..
Just found your videos, great stuff. I would like a free software to make a pipe for my 1981 YZ125
See the "description" section under the video that has a link to the free pipe software.
Very informative would really like the software 👍
Thank's for the comment Darren
Hello sir, I wanna make exhaust for my two cylinder two stroke, is it possible to make 2 in 1 ex. chamber? (ex. timing 144-165, bore 73, stroke 73, target RPM 5000-6000)
You can use the free pipe software I wrote that uses all the same equations as in the videos.
Link to it in description section under video.
@@AuMechanic But Question is how to calculate one pipe for two cylinders? For one cylinder is easy but for two is challenging. Length of sections should be same but diameter shouldn't (my guess). Is there some generalick quide because I didnt hear anything about it
Thanks a lot for answer
Thanks for the effort🤞
Thank you for the comment
Hej. Great video series!
How abouth simple 2stage or even one stage chambers?
Basically the single taper compared to the multi taper makes the effective range of the pipe more narrow and peaky.
For an engine with many gears and a narrow power band a single taper cone would be suitable.
I may add it to the software but at this stage there is limited interest in the software to warrant the extra work to do that.
@@AuMechanic I understand. I am thankfull for your reply. I am asking this because of the simplicity of the build. For example one stage exhaust chamber tuned pipes are in use in model rc engines. With only flat back end with muffler setup on the stinger side. I am makind something similar on 70cc engine.
Ok, there are a few applications that only need a narrow band pipe.
Many calculators revert to the Gordon Jennings formula when you select a single taper pipe but that design is very old (cira 1970's) and for a 2 stage diffuser they use Blairs early equations in 1990 whereas the 3 stage diffuser uses his later published equation in 1996.
My intention was the use the basis of Blairs 2 and 3 stage equations to make a single taper pipe rather than revert to Jennings equations.
Jennings equation does work and I used it in the 1980s when I was making race pipes but Blairs pipe equations are derived using far more scientific methods than Jennings used
How can i get a copy of this program. Thanks
See link to software in description section below video
Download at birdcagesoft.com
Is the program a available? I'd be I intrested
It is
See the link in the description section below the video
Later videos cover some info on using the software.
I’ve just bought a 500 Krauser and need pipes. I was thinking of making them myself but I’m starting to think I should leave it to the experts lol. It’s a little more complicated than I first thought
It is a bit complicated but the flip side of it is that having someone make a custom pipe is very expensive, off the shelf pipes suit stock engines so if your is stock standard then you may be able to get an off the shelf pipe made for it cheaper.
The most difficult part of making the pipes is making the cones if you don't have a sheet metal roller to do it but you can get someone else to do that part. After that is is just a matter of welding it up. There are dozens of videos showing the process of physically making a pipe you can refer to.
I may be a tad late, and possibly couldnt use the program anyhow due to my exclusive use of Android. but i need to make two pipes for my engines, make not buy because they have to fit them to my individual aircraft. The local shop doesnt want to design them for a one off pipe. X2
One off pipes are pretty time consuming and no surprise shop is reluctant to make one..
Pipe makers all do volume pipes for stock engines.
The problem is once you do any porting and change the exhaust timing and port size the stock pipe is out of tune but there are some mods you can do to a stock pipe to account for port timing changes by re-calculating the tuned length and then shortening the pipe to bring it back into tune..
When I did porting in my business and used to get them to send me the pipe too and modify that to account for the port timing change.
Can you give me the measurements for a pipe for my motor if I pay?
You can use the free software to do the sums and use the videos that cover the software.
See description section for link to it.
@@AuMechanic The thing is, I'm a bit thick and lazy. Its an RS125 thats going into a race sidecar outfit and we can get your channel on the side for the help
Would be nice to have a free dependable calculator.
Just look in the description section below the video and you shall find one, there is a link to pipe calc I wrote that is freeware.
@@AuMechanic Thank you very much! Your video's are very helpful in a lot of ways with the exhaust pipe function. We have good pipe builders in the US but I can't afford them.
hi dave,
can you give me some lessons on 2 stroke exhausts, i'm preparing a 3 cylinder car and i need some lessons but i can't find anyone willing to teach me even if i pay
I can only answer questions you may have about the content of the videos sorry.
Good day
Please I can have your software I would be very helpful
The link is on the description section of videos
I need to build a custom pipe for my airplane build would love free pipe building software.
There is a link to it in the description section under the video.
Thank you Dave, hey question for you , I put a 2014 rotax 800 etec in my bushplane and the factory pipe is the wrong shape . Can I just take measurements from the factory pipe and use those values with different bends to achieve the fitment ? If the L and D values remain the same does the shape or routing matter?
Also what is your recommended material to use ? Lighter is better for my application
@@davepalmer8925 0.5 to 1 mm
The thinner it is the easier it is the bend cones but that harder it is to weld.
@@davepalmer8925 So long as the L and D dimensions are right it doesn't matter what shape or how many bends you put in it.
I want a Free pipe calculator program please Dave :-)
See the description section above for link to software.
meaning mean port area ¤, vlv closed vlv. fully open, average
I want that soft ware
Thank's for the comment
The 2 stroke pipe software is available now, if you see newer video it shows where to download it.
How to design a s bend expension chamber.
The S pipe is basically a U shaped header with an vertical positioned diffuser, followed by a pie slice formed right angled neutral section to a horizontal baffle cone and tail pipe.
two Stroke Expansion chamber for 1/5 36cc RC
Same principles apply, the difference is the fuel used that effects the calculation of sonic velocity in the pipe to some degree, but not greatly.
Yea, I'd love to have a calculator. And yes I would build from it!
I’d use it! I’d probably pay for it
No need to pay, its freeware, see the link in the description section.
@@AuMechanic Thanks!
I want it! I would willing to pay for it
I wont be charging anything for it, I've written a fair bit if freeware and enjoy writing code but there has to be some good of it to more than just a few and the comments here seem to suggest it will be, so thank's for commenting.
AuMechanic 8 I've been using Jennings calculation to modify existing aftermarket pipes as close as I can but I think I'm ready to do a scratch built pipe. Currently building an eddy brake dyno for testing
Glad to hear it, eddy current brake dyno's are the most accurate in repeatability.
I also used Jennings equations when I started built pipes in the 80s and it was accurate enough, the videos I'm doing now are all based on Blairs later works in 1997 which is based on more scientific methods but Id be greatly interested to see them compared on an accurate Dyno.
The 2 stroke pipe software is available now, if you see newer video it shows where to download it.