Porting basics

[trickedcarbine]

The dremel does not produce the same torque that a foredom will. You have to really get it in the RPMs to produce marginal results. The foredom or equivalent will require much less RPM to function and this yields longer lasting burrs and faster cutting due to the motor having the torque to slam the cutting surface in deeper and remove a larger kirf.

[sprinklerman]

The dremel does not produce the same torque that a foredom will. You have to really get it in the RPMs to produce marginal results. The foredom or equivalent will require much less RPM to function and this yields longer lasting burrs and faster cutting due to the motor having the torque to slam the cutting surface in deeper and remove a larger kirf.

I don't know how you could even fit a Dremel with the angle head, and a burr in a banshee cyl.

Plus the higher speeds if the Dremel seem to harden off the aluminum.

 

Sent from a van down by the river

[Pasi S.]

Dremel angle head will not fit in to a 64mm cylinder. That was a reason to get that cheap Snap On 90.

[sstaton1983]

the pedal makes the RPM control much easier. high RPM not so good when working with the aluminum, figured that out quickly with the air operated pencil grinders.....

[camatv]

ok i stopped on the 2nd page..

 

here is my recommendations to anyone that want to build a 2 stroke..

 

go to google OR ebay  type in 2 stroke tuning.  buy at LEAST 2-4 books on the subject and read.  some of the best things i have learned about the subject is from these books.  you will NEVER see these theories  be able to decide for yourself what kind of porting, pipe, AND head/dome combo engine balancing pulse charge, lowerend compression, velocity porting port angles and aiming, port size and size limits can be. and i know i'll get it for this  but the best on the subject i feel is not just gordon's book  you have to know them they were amazed at that time to release a cyl, pipe, engine combo that made  5 hp over stock on that particular motor.. 

 

then start with a known motor and attempt to recreate all the types of power capacity's specific to that motor..   

 

to do that will require a lot of tooling and a lot of practice..   

 

and yea  your going to get a lot of crap on this site..

[sstaton1983]

I think Gordon Jennings is a good start for people like me to brush up on the basics...you can't be successful at it unless you learn to crunch the numbers, the more I learn the more shit I have to add to the equation..... I'm fixin to start on my daughters lt 80, thinking about trying to hydro form her a pipe..not sure what expansion chamber program to use..

[sstaton1983]

http://www.amrca.com/tech/tuners.pdf

[trickedcarbine]

If Jennings were alive, how fast would his banshee be?

[registered user]

I'd thought about where you could add the extra volume as well.

well theres several ways you could do it. im gonna test a longer rod and spacer plate hopefully soon

 

 

 

 

However, around the crank wouldn't be too bad because the piston's downward travel would force the charge out of the way, potentially creating a bit of momentum in the direction of the transfers.  Again, I haven't put much thought into this.

heres my thoughts on that. when the piston goes down the mixture has no choice but to go down also. where the mixture ends up will depend on available space. it stands to reason in my mind that the mixture will go to the area that has the most open space. so if we leave the case area (between the red lines) as small as possible, wouldnt that meen more mixtre will remain higher up (between the green lines), where it has only a short distance to travel to reach the cylinder ? this is mostly why i think creating any extra volume down low in the case area between red lines) is a bad idea. just my uneducated opinion

 

 

[camatv]

if you were going to increase the volume it seems like it would be best to do it up high. perhaps in the tunnels themselves or near by. in 1 transfer cycle not all the case mixture will make it to the cylinder. the tunels can only pass X amount in a very brief time. so to me it doesnt make sense to put extra volume far away, like down in the case bottom, where it has basically no chance of reaching the cylinder on that particular cycle.

 

 

things like this are not necessarly true. and is really evedent in the larger single dirtbike motors.   the pipes action on the cylinder also makes this kinda void.   and in stroker motor where the case material is removed to allow the extra stroke your also adding cc to the motor.  so case compression also changes.  this is on thing in most of the older books that is not nearly an issue these days.  back then cranks were all open and had no real sides to them now  the cases had a shit ton more volume than what most all modern motors ( after say 1975?) have now.  you can still do a crank stuff or a case stuff if you really think its necessary.  the best thing to do is create volume AND velocity.  there are ways to do this  and its pretty interesting how..  also thinking the charge just hangs out under the piston  maybe not so much.  i have recently figured out a way to get the charge into the transfers much much quicker and nearly avoid being under the piston much at all...   its really intersting what that does to the motor.  there is a way to figure the fuel charges speed  and its a lot faster than you think.. 

 

these types of things are what you will read about in most good books.  not every one has the same conclusions in them so its best to read a lot and then think about the motor in an overall running condidtion  not just a pipe  or just the dome  or just the angle of the transfers.  for example  i dont angle the transfers at the very back wall on all motors  certain rpm's really like them almost pointed right at each other..  and without a dyno i dont think the absolute optimal can be just figured out in mathmatics..  

[registered user]

If Jennings were alive, how fast would his banshee be?

its hard to say but some things he wrote about are alittle outdated. he said 4000 ft/min piston speed was near the absolute limit. any modern engine of good design shouldnt have a problem well above 4000

[camatv]

The dremel does not produce the same torque that a foredom will. You have to really get it in the RPMs to produce marginal results. The foredom or equivalent will require much less RPM to function and this yields longer lasting burrs and faster cutting due to the motor having the torque to slam the cutting surface in deeper and remove a larger kirf.

 

 

on this  using faster speeds will overheat the carbide burr.  the extra tq unless your using an alluminum carbide will result in usually an overheated burr also.   i personally HATE the alluminum burrs unless i am doing top case matching  and then i have to be really really carefull. i personally prefer the double cut " flame" shapes and then in the smaller sizes.  also i use a lot of lube when doing work to keep the burr cooler and lubricated..  on led's site there is a bunch of pictures of a jigg they use to aid in porting time using a mill.  im going to look into doing this and doing some experiments.  i have also thought of milling the transfers completely off and then just filling in the outsides with weld.  no jb weld but actual tig welded.   dremel makes an adjustable speed motor in its higher end class  for a beginner and an older cable extension ( good luck finding one) they are fine for begginer work.    i have the foredom set up now and i dont necessarily think its a million times better..  sometimes the cable starts to twist and it results in some really wacko fluctuations in the tooling.  the dremel being underpowerd never really did that.  i prefer sanding drums on the dremel still.    the 90 d tool that snappy makes is a great way to start on transfer work BUT its super picky and i'm sure your going to trash a lot of mini carbides getting it figured out.  i have a 90 for the dremel also but sometimes its a bitch to conrol.  the last set of cyls i did i figured out a way to cut the transfers up a lot with minimal time and not nearly as much stress on the tooling..

[registered user]

things like this are not necessarly true. and is really evedent in the larger single dirtbike motors.   the pipes action on the cylinder also makes this kinda void.   and in stroker motor where the case material is removed to allow the extra stroke your also adding cc to the motor.  so case compression also changes.  this is on thing in most of the older books that is not nearly an issue these days.  back then cranks were all open and had no real sides to them now  the cases had a shit ton more volume than what most all modern motors ( after say 1975?) have now.  you can still do a crank stuff or a case stuff if you really think its necessary.

 

i dont understand what your saying. maybe you misunderstood what i was saying. lets leave the pipe out if it because i dont think it has any relevance at this moment

 

when the piston is heading down wouldnt you want to give as much of your case volume as possible, the shortest route possible to reach the cylinder ? this is what i was saying in the post above which has the picture

 

this isnt a argument about whether a particular engine runs best with X amount of case volume. but rather where the volume should be located

[camatv]

if you looked at how most "hot saw's motors are built  you would make actual transfers in them also.  its an atrocity in there.  back in the 70's people were trying all kinds of wacko crazy motor designs  and calling them the top shit..   

 

google 60's racing karts.  check out those pipe designs!

[camatv]

i dont understand what your saying. maybe you misunderstood what i was saying. lets leave the pipe out if it because i dont think it has any relevance at this moment

 

when the piston is heading down wouldnt you want to give as much of your case volume as possible, the shortest route possible to reach the cylinder ? this is what i was saying in the post above which has the picture

 

this isnt a argument about whether a particular engine runs best with X amount of case volume. but rather where the volume should be located

 

 

yea i must have misunderstood you. i wa thining your wanting to creat a much bigger transfer tunnel and port thinking that alone is going to increase velocity.  in one of the books i read they talk about the actual opening, tunnel, and transfer opeing size and what all that actually does.  its pretty interesting,   BUT with a spacer and a longer rod your lowering the cranking compression.  its going to make the motor more lazy but if thats what you want then thats what you want.  its an easy way to lessen a pipe hit.  so is adding a reed spacer.  adding a spacer AND more stroke can cause a cancelation of the added cc in the lower end.  also adding more bore can increase the compressionin the lower end also.  to me its one of the reasons some motor just work  and others really struggle ( along with overall rotation weight and piston speed, stopping stresses, acceleration stresses)

 

also the PIPE HAS to be a consideration.   think about this.  maybe you never had.  the piston is at bdc. the pipe is still pulling an ever increasing vacuum on the insides of the motor   whats happening???  to not consider this is just again thinking as each individual item at the same time.  thinking about this effect after looking at pipe design and understanding exactilly what its actually doing made me come to the realization to move the charge from under the piston..   believe me  nobody else or anywhere else have i read about these idears..  and noone has ever posted up pics of what i did to accomplish these therories  ( ITS in my 350cc wife's bike motor..)