Joined
·
8,623 Posts
Some people know that I was slowly, in my spare time researching and plotting a sleeper motor build based on the 3v head made infamous by SDG. I wanted to see if an import build could be made to go toe to toe with a built Honda, which we know they can now, but specifically I wanted it to be an even displacement fight. I also felt there was potential in the 3v head itself and wanted to see how far I could exploit it.
This was going to be my attempt to match a Kitaco 124SE.
Well, I've since picked up a new project that's going to suck up a great deal of my time and money, and I ran up against a couple technical issues with the 3v planning that I haven't sorted yet. I figure I might as well toss this info out for the world to see what happens with it.
Anyone that makes it work had better credit me some though!
http://www.x386.net/TTR/Sleeper/3v.html
http://www.x386.net/TTR/Sleeper/motor-worksheet.html
These were my working notes. As you can see I was shooting for a shorter stroke motor, with high hopes that I could use high revs to get me the HP I needed.
I ran into problems though, both revolving around the SDG 3V head. The first is the head itself. Out of the box it uses two 19mm intake valves, which on paper should work like a single 27mm to 29mm unit. There wasn't any room to go bigger though, and worse, they are at a pretty steep angle compared to modern heads. Not to mention HEAVILY shrouded by poor combustion chamber design. I didn't consider this a show stopper, a bit of time with a carbide burr would fix the shrouding, and I could live with the included angle and limited valve size for now.
What did stop me from going my preferred bore x stroke setup is the size of SDG's dowel pins. A good mm or 2 larger than what a Honda or Lifan/GPX uses. There is no way to safely hit a 60mm bore let alone 61 like you can with the other big import mills. I figured I could bore the cylinder out for the sleeve, fill the stud paths (now exposed) with weld, press in a sleeve, and re-drill the stud paths, but not open them up for dowel pins. Instead I would drill the cylinder and head in a couple spots to use external locating pins, and try and do the same for the base. Still may not get enough of a sleeve to go 59mm.
Plus the added fun of trying to rework a 49.5mm crank for a 41mm stroke, no idea where to start on that process. : )
As to why I did all of this research and never lifted a wrench... I haven't got a whole lot of shop access, what little I do get, I need to make the most use out of. This is why I'm a theory nut, I want to have my ducks in a row before I settle on a build path so I can do the job once. Planning this much out, researching online, chatting with many here on PM, even though I've nothing to show for it was still time well spent. I've now got a much better understanding of what makes these things go, and how to make them go faster.
One result of this research:
http://www.x386.net/TTR/tech/cgi-bin/motorsim.cgi
Slower than death because it's on a 386, and not very accurate, but still fun to play with. Red on the chart is up to 75% volumetric efficiency, yellow up to 100%, Green is up to 115% efficiency.
There, how's THAT for over-sharing. : )
This was going to be my attempt to match a Kitaco 124SE.
Well, I've since picked up a new project that's going to suck up a great deal of my time and money, and I ran up against a couple technical issues with the 3v planning that I haven't sorted yet. I figure I might as well toss this info out for the world to see what happens with it.
Anyone that makes it work had better credit me some though!
http://www.x386.net/TTR/Sleeper/3v.html
http://www.x386.net/TTR/Sleeper/motor-worksheet.html
These were my working notes. As you can see I was shooting for a shorter stroke motor, with high hopes that I could use high revs to get me the HP I needed.
I ran into problems though, both revolving around the SDG 3V head. The first is the head itself. Out of the box it uses two 19mm intake valves, which on paper should work like a single 27mm to 29mm unit. There wasn't any room to go bigger though, and worse, they are at a pretty steep angle compared to modern heads. Not to mention HEAVILY shrouded by poor combustion chamber design. I didn't consider this a show stopper, a bit of time with a carbide burr would fix the shrouding, and I could live with the included angle and limited valve size for now.
What did stop me from going my preferred bore x stroke setup is the size of SDG's dowel pins. A good mm or 2 larger than what a Honda or Lifan/GPX uses. There is no way to safely hit a 60mm bore let alone 61 like you can with the other big import mills. I figured I could bore the cylinder out for the sleeve, fill the stud paths (now exposed) with weld, press in a sleeve, and re-drill the stud paths, but not open them up for dowel pins. Instead I would drill the cylinder and head in a couple spots to use external locating pins, and try and do the same for the base. Still may not get enough of a sleeve to go 59mm.
Plus the added fun of trying to rework a 49.5mm crank for a 41mm stroke, no idea where to start on that process. : )
As to why I did all of this research and never lifted a wrench... I haven't got a whole lot of shop access, what little I do get, I need to make the most use out of. This is why I'm a theory nut, I want to have my ducks in a row before I settle on a build path so I can do the job once. Planning this much out, researching online, chatting with many here on PM, even though I've nothing to show for it was still time well spent. I've now got a much better understanding of what makes these things go, and how to make them go faster.
One result of this research:
http://www.x386.net/TTR/tech/cgi-bin/motorsim.cgi
Slower than death because it's on a 386, and not very accurate, but still fun to play with. Red on the chart is up to 75% volumetric efficiency, yellow up to 100%, Green is up to 115% efficiency.
There, how's THAT for over-sharing. : )
