Dirtsurferaust Posted June 17, 2014 Report Share Posted June 17, 2014 Wouldn't the steep (relative) oem banshee piston dome have to be compensated for in the different roof angles between the main Trans and the secondaries Where as a flatter pistons of aftermarket require different angles from from the roofs just because less hlll of a dome to get around So many variables I only reverse engineer buy a well ported jug look close compare it to other good running combinations practice on wrecked barrels and grind Read and learn but deciphering who knows and who pretends that's an art Some pretty compelling arguments but some are still only guessing but that's ok Quote Link to comment Share on other sites More sharing options...
tfaith08 Posted June 18, 2014 Author Report Share Posted June 18, 2014 Well, I've decided not to buy a ported set of cylinders because I know I'll look inside them and take ideas. It's stealing work in my eyes. If I ever stop working on other people's stuff, I might do it then so that it can only be applied to my stuff. I can't bring myself to make money off of someone else's design, which is what it'd ultimately be doing. Lately, I've sort of gone through and started re-thinking all of what I know with porting. I'm not a master and I don't think I'll ever come up with a design that'll hang with what the site sponsors build unless I come across some insane amount of money and have nothing to do all day long. In that case, I'd have about 50 cylinders and a dyno to test with. In that scenario, I'd be chasing a better design much more effectively. For now, it's just one piece at a time. Recently, I've started putting a lot more thought into port shaping and it's a subject that requires a bit more thought than I've imagined before. Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted August 26, 2014 Report Share Posted August 26, 2014 What ever happened to faith? Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted August 26, 2014 Report Share Posted August 26, 2014 Havnt seen him lately Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted October 1, 2015 Report Share Posted October 1, 2015 $4.50 for a pack of cigarettes, or a SuperFlow flow bench? I think I know the answer lol. I would absolutely not call this a method of quantifying your port work by any means, but it is cool. I was referring to actually watching how the ports actually flow. Lots of guys are trying to aim stuff but throwing smoke at it with pressure let's you actually see where, how, and how much volume you're moving to a particular point. Quote Link to comment Share on other sites More sharing options...
registered user Posted October 2, 2015 Report Share Posted October 2, 2015 Someone mentioned it earlier (or maybe it was another thread), but modern designs use triple transfers on each side. This really does a lot to keep the mixture flowing in the intended path. Again, it was also mentioned that there is a lot to be gained from getting the mixture into the cylinder in a controlled manner. The triple ports do a lot to help that, I believe. not sure what snomo engines look like but you could tear into any dirtbike from the last 20yrs and not see triple transfers. there was one or two real old single cylinder engines that used them but those ideas were abandoned long ago. if i were to bet money i would say the reason calvins cylinders have 3 transfers per side is for the reason you mentioned. the mixture control into the cylinder is likely better when you have a sqaushed together inline twin design. on a single cylinder or a twin that isnt sqaushed together, its unlikely youll ever encounter the triple transfers Quote Link to comment Share on other sites More sharing options...
registered user Posted October 2, 2015 Report Share Posted October 2, 2015 tricked this is only my thoughts but for the smoke idea to have any sort of value, i think you would need to test all the transfers at once to see how they influence each other. you can look at the horizontal angles on a cub for example or any cylinder for that matter. testing a single port likely wont give a true representaion of what actually happens, since the trans angles are cast in such a way that they influence the adjacent port. not only that but slow moving air doesnt behave the same as fast moving air around turns and such. how exaclty do you plan to move the smoke through the ports ? dont say shop vac on one end and marlboro on the other Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted October 2, 2015 Report Share Posted October 2, 2015 tricked this is only my thoughts but for the smoke idea to have any sort of value, i think you would need to test all the transfers at once to see how they influence each other. you can look at the horizontal angles on a cub for example or any cylinder for that matter. testing a single port likely wont give a true representaion of what actually happens, since the trans angles are cast in such a way that they influence the adjacent port. not only that but slow moving air doesnt behave the same as fast moving air around turns and such. how exaclty do you plan to move the smoke through the ports ? dont say shop vac on one end and marlboro on the other The fella here who did a motor for us last season has a flow bench with smoke sticks. He likes to see how it all comes out of the ports and how/where the AFM actually mixes/collides. He is predominately a snowmobile guy but has been doing this since the 70's. He has messed with a lot of different set ups and has a good grasp of what works for certain types of layouts. Some stuff he jambs to the back of the cylinder and the boost port will kind of loft it up to the center of the dome. Other stuff he aims the transfers right toward the center of the dome, he even had an old GPX 670 motor with transfers set up like a whirl pool. He said he tested all the "turbo flow" ideas guys had in the 70's and 80's and it's definitely a gimmick. The turbo domes are junk, but there are some cranks on earlier motors that benefit from putting those little "turbo vanes" on them. He is always putting epoxy here and there filling little tight nooks and crannies in tight bends or angles. People always say he's killing volume, but the flow bench says otherwise and it allows you to visually see how the air flow actually improved. He likes velocity in a nice stream with low turbulence. Some people think they are adding velocity by adding turbulence, not always a winning idea. He's a pretty dominant fella in the sled game and I am grateful he has been willing to teach me some stuff. Reading books will only get you so far, after that it's up to you to put the time in. So when you find some old bastard who is willing to give ya a few short cuts, ya hang out and listen. Quote Link to comment Share on other sites More sharing options...
tfaith08 Posted October 3, 2015 Author Report Share Posted October 3, 2015 He likes velocity in a nice stream with low turbulence. Some people think they are adding velocity by adding turbulence, not always a winning idea. I think I've read about those claims before and they never made sense to me either. The 2 main types of flow (laminar and turbulent flow) with the same fluid are dictated by velocity. To make something turbulent doesn't mean that you've effectively increased flow, it's the other way around; higher velocity creates turbulent flow. Once explained like that, most think that laminar flow is possible with the pressure that the intake charge sees upon the transfers uncovering, which causes the charge to slow. I don't know the figure right away, but the velocity for atmospheric air to flow in a laminar state is far below what is going to be seen in any engine. The first part of the quoted concept, I do agree with. I got my start by watching a guy build hotsaws. That's purely a free for all because of the vast difference between stock and race condition. There'll be ports all over the place and you won't know what made any one cylinder work, only whether it did or didn't. Throw nitromethane, big ass carbs, custom heads and domes, custom pistons, etc. into the mix and shit gets wild. I was fortunate that A: I even had a guy guide my way of thinking and B: that the guy I had around that had won several national champoinships. But his ideas were different than what most people are after with Banshees. His powerband width was around 300-400rpm. Translating that to an MX or dune port concept for a Banshee is an entirely new dynamic on what I knew and is a large part of why I ovethink things with porting. Reading books will only get you so far, after that it's up to you to put the time in. So when you find some old bastard who is willing to give ya a few short cuts, ya hang out and listen. Every time I ever read a book, I felt like all my questions were answered until I started back grinding. You'll always find more questions, usually within 5 minutes of when you started. Every angle can be very close and every port to an exacting duration, but the port will be shit if the remaining geometry is off. If you call any builder, they'll tell you what durations they use for whatever you're thinking about building. Smoke, at least in the way that I described it, is a good way to visualize the ports in action. That's about it. There's simply so much going on with pressure differentials all over the place that you could never hope to see it all with just a cigarette. I'd imagine that a super-stuffed crankcase would make the ports flow more like they're intended. There's a few other ideas that I have floating around about small crankcases, but I'm working some extreme overtime and can't quantify them all now. As for what happened to me, I was robbed of a huge chunk of tools and a customer's bike, plus I was scammed by 2 customers working together. It was about a week after I started contacting blasterforum to get everything lined up to be a site sponsor. I'd planned on seeing how well I did there and then moving here, but things change. It's a big relief to let go of that challenge. Quote Link to comment Share on other sites More sharing options...
OuiBJammin Posted October 3, 2015 Report Share Posted October 3, 2015 Unless your flow bench has the capability to interrupt the flow of all transfer and inlet ports in the manner and timing a moving piston would over the range of RPM you plan to run the motor at it seems pretty pointless,Not to mention vary the pressure ratio on both sides of the equation,pipe and crankcase at the same time and RPM. Software can simulate this with a fair amount of accuracy without the need for grinding up usable cylinders and making lots of aluminum dust in hopes of outsmarting the laws of physics by chance,I tried that as a teen(1970's - 80's) with RDs and RZs along with some other older 2 stroke motocross bikes my brothers had.Rarely got any faster,almost always got less dependable. Quote Link to comment Share on other sites More sharing options...
registered user Posted October 3, 2015 Report Share Posted October 3, 2015 i think the smoke test was just to try and get a ballpark visual idea of which way it goes based on the transfer angles. but ya to get a better idea of what happens there may need to be a way to vary the pressure at several different locations like mentioned. a running engine would have varying pressure differentials at the crankcase, cylinder and pipe during each cycle, which seems like it would be difficult to simulate but maybe theres some fancy machines that could do it Quote Link to comment Share on other sites More sharing options...
tfaith08 Posted October 4, 2015 Author Report Share Posted October 4, 2015 Unless your flow bench has the capability to interrupt the flow of all transfer and inlet ports in the manner and timing a moving piston would over the range of RPM you plan to run the motor at it seems pretty pointless,Not to mention vary the pressure ratio on both sides of the equation,pipe and crankcase at the same time and RPM. It will, however, show when something is way off. If its garbage without the piston flying by at 9000rpm, it sure as hell will be garbage with it. It's more for a visual idea. It isn't a diagnostic tool or any other tool for that matter, it's only to get a visual sense of what's going on and to help tie things together. Any modern CFD program can run it. The software I had could run a model like that, but the computing time for even a basic 1 intake, 1 exhaust port model running at 6000rpm and all other conditions as accurate as I could manage had a computing time of over 100 hours. Even on a 16 core setup, you're looking at a full day of computing time on a model THAT basic. Throw 6 more ports in there and you're looking at hundreds of hours of computing time. No builder that is relevant to this community is going to dedicate the time and money into a new way of viewing an already known process that may not even pan out for them because they lack an extensive background in college level fluid mechanics and thermodynamics. With builders already pushing 80hp on trail-ported stock cylinders, there isn't much else to improve upon. On the other hand, I did have a lot to gain by learning that way, only I didn't have the resources to pursue it. What little I did get to model showed me a very similar version of blowing cigarette smoke through the transfers. With a single port and a static model, I was able to see just what a piston did to affect the flow of the transfers and how cylinder and crankcase pressures affected each other. Combining that with the smoke was how I started making things faster. All in all, the time spent funding the means to model a near perfect port far exceeds the time spent going through cylinders and tons of gaskets and solvents and finding a close enough option. Quote Link to comment Share on other sites More sharing options...
registered user Posted October 4, 2015 Report Share Posted October 4, 2015 hard to believe its the end of the road with nothing left to improve. maybe new ideas have just dried up Quote Link to comment Share on other sites More sharing options...
tfaith08 Posted October 4, 2015 Author Report Share Posted October 4, 2015 I wouldn't say the end of the road, but there's gonna have to be some new ways of thinking before significant improvements can be made. It's evolutionary at this point, not revolutionary. Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted October 4, 2015 Report Share Posted October 4, 2015 I tried that as a teen(1970's - 80's) with RDs and RZs along with some other older 2 stroke motocross bikes my brothers had.Rarely got any faster,almost always got less dependable. So, did you ever do the research to figure out what you were doing wrong? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.