Exhaust port roof shape vs power characteristics

[sleeper06]

i have tried squared off top side of the port,I prefer a trapeziod style now gotta get the kids ready for school ill get back later

[jbooker82]

This guy acts a lot like sloryder.

[SlowMoe]

it's not about trying to hide info conspiracy theories, etc, but the way you just jump out of an asshole to piss on everyone and get mad that someone came within pissing distance.

I'm not mad buddy. I like you. But, aside from it being extremely confusing, I have a problem with this statement; when we first became acquainted (back when we got along) I would ask technical quiesions on here and you would send me PM's with tips, and ask me not to share the information you gave me, like it was some kind of big secret. And I actually respected that and never shared anything you asked me not to. But now you come out and say I am wrongly accusing people of doing the same exact thing that you do, probably on a regular basis. Bad memory?

 

no, we do not want any fucking info you are willing to share, since it is most likely as distorted and fucked up as what you do/did on this site. if anyone took what you said as fact, and put it to work, and spread it around, the high likelihood that it is somehow incorrect could cost this site's members tens, of thousands of dollars in fuck-up recovery expenses.

 

And what's with this "we" stuff? Are you the official BansheeHQ spokesperson/ guardian or something? You must think that everyone is stupid and will just blindly follow the recommendations of someone on this website without getting second opinions. To be honest, I have made my share of bad decisions in the past, and I have paid for them, but you know what? I learned from every one of them. You think the top builders out there got where they are by staying inside the limits of what was taught to them? No they got where they are by pushing the boundaries and learning from their mistakes. No guts no glory right.

Do I believe others should modify their engine based on speculation on my part? No. But if it IS speculation, I will do my best to let that be known.

i will give an honest answer to your question...... no, i have not done it, nor will i ever square off the top of the ports, for reasons already mentioned. can you? of course you can, and it will run, just make sure there is a nice chamfer on it, and don't expect it to make more than a pass or day, whatever, and keep throwing rings at it. don't get butt-hurt when the whole rotating assembly gets transplanted to the trash. you may just find that .002% or more hidden power...... good day sir

Since you have never done it, how can you know all this? It appears that there may be a little speculation involved...? Strange I thought it was only Slo who did that. And .002% hidden power? Really? I would be willing to bet my paycheck against yours that there is much more than .002% to gain from going from an oval port to a port with a 12mm radius on the corners and a flat roof.

Offer stands.

Edited March 17, 2011 by SlowMoe

[Snopczynski]

Sloryder, I dont want any of the info you share!

[SlowMoe]

Sloryder, I dont want any of the info you share!

 

[AKheathen]

SHHHHHHHHH you sound like you got some grease on your purse......fuckn cunt

 

it's called a "man-bag" or "sachel", and you don't want to see what happens when i get grease on it...... worse than a menopause break-down

 

I'm not mad buddy. I like you. But, aside from it being extremely confusing, I have a problem with this statement; when we first became acquainted (back when we got along) I would ask technical quiesions on here and you would send me PM's with tips, and ask me not to share the information you gave me, like it was some kind of big secret. And I actually respected that and never shared anything you asked me not to. But now you come out and say I am wrongly accusing people of doing the same exact thing that you do, probably on a regular basis. Bad memory?

 

well, some things can be shared to help out an individual in good faith as an elected solid, but said personal tricks of the trade don't need to be spread around like butter on bread, since that is what makes the "bread and butter" to the person who put the foot-work in to get such marketable edge on things...... and it was just a small one. no need to aide in taking food out of a kid's tummy. the normal "how-to's" and "do-not's" are perfectly fine.... which is where you used to go crazy, accusing us of hiding everything.

 

And what's with this "we" stuff? Are you the official BansheeHQ spokesperson/ guardian or something? You must think that everyone is stupid and will just blindly follow the recommendations of someone on this website without getting second opinions. To be honest, I have made my share of bad decisions in the past, and I have paid for them, but you know what? I learned from every one of them. You think the top builders out there got where they are by staying inside the limits of what was taught to them? No they got where they are by pushing the boundaries and learning from their mistakes. No guts no glory right.

Do I believe others should modify their engine based on speculation on my part? No. But if it IS speculation, I will do my best to let that be known.

 

no, i don't think i am an official spokesperson....... i don't think...... would probably have to pay royalties, haha...... anyways, as you should have picked up on, this site is not only run by tyler and mods, but also, it is more of a community, where the members also step up to look out for the well-being of the site, and it's offerings/content. other sites, you have to nag on a mod to wipe your ass when you discover a stinky, but we (the highly active members) pretty much know what is going on, what the site is about, what is kosher, and what is not, and pick-up on obvious issues. i knew there are several members who would agree with that statement, so i said "we" i would not be so pretentious as to replace "we" with "i" because that would be saying that i hold my personal opinion to be of more worth than the mass of the members who know what is going on with the site. the statement you made highlighted in red, is one that sounds like a definate improovement, and good idea. be warned, that i may be compelled to hold you to it. if you have indeed improved your ways, i will be delighted to witness it..... please don't go back to pushing your ideas and opinions on every unwilling guy looking for help from the site, or "we" may be compelled to once again take term of literary rectification (more e-flogging) one member at a time, or all at once....however it may play out

 

Since you have never done it, how can you know all this? It appears that there may be a little speculation involved...? Strange I thought it was only Slo who did that. And .002% hidden power? Really? I would be willing to bet my paycheck against yours that there is much more than .002% to gain from going from an oval port to a port with a 12mm radius on the corners and a flat roof.

Offer stands.

complete retorical exaggeration....... i wouldn't even bet my little 1100 take-home check for working a few days early....

[camatv]

WOW WEEE

 

here is my experience.

 

you need to have the exhaust as wide as possible ( as stated in those books from the 60s')

 

you should cut an extra tranfer port, window in there also ( as stated from the 60's as most motors from that era didnt have more than one trasfer port up each side)

 

the "tuned length " pipe has specs but to get it really right you need to build a FEW and play with the chamber to piston length cause thats not really know what works ( as stated in that book also)

 

i'd love to see an engeniering book from KTM about their 2 strokes and how they developed them also theroory's from HRC from the days of 500cc superbikes would be phenominal..

 

 

its interesting to see how the serval, and cub and other similar aftermarket cylinders are able to take things from those more modern 2 stroke desingns and push the limits through the roof of what was the norm even 10 years ago.

 

those 2 stroke books are intersting but again they have a lot of outdated therior's in them BUT are an EXCELLENT read if you are into this stuff. are they going to teach you how to port the holy hell out of your stockers MAYBE BUT its still going to be up to you to get it all to work.

 

i personally HATE a flat roof lately i have liked about a 30* dome on the top. at least i think thats what the spec was for the last template i custom made>??

 

i HAVE been imagineing in my head a completely differnt shape but i'm not sure how it will work SO i'm going to template a few and see how it fits hope they dont eat pistons i'm shooting for 80-85% width with NO triple ports.. ( im not thinking its going to work but hey>)

 

when i first started i trashed a few cylinders JUST to know what the limits were. knowing where the coolant passages are is important.

Edited March 18, 2011 by camatv

[SlowMoe]

WOW WEEE

 

here is my experience.

 

you need to have the exhaust as wide as possible ( as stated in those books from the 60s')

 

you should cut an extra tranfer port, window in there also ( as stated from the 60's as most motors from that era didnt have more than one trasfer port up each side)

 

the "tuned length " pipe has specs but to get it really right you need to build a FEW and play with the chamber to piston length cause thats not really know what works ( as stated in that book also)

 

i'd love to see an engeniering book from KTM about their 2 strokes and how they developed them also theroory's from HRC from the days of 500cc superbikes would be phenominal..

 

 

its interesting to see how the serval, and cub and other similar aftermarket cylinders are able to take things from those more modern 2 stroke desingns and push the limits through the roof of what was the norm even 10 years ago.

 

those 2 stroke books are intersting but again they have a lot of outdated therior's in them BUT are an EXCELLENT read if you are into this stuff. are they going to teach you how to port the holy hell out of your stockers MAYBE BUT its still going to be up to you to get it all to work.

 

i personally HATE a flat roof lately i have liked about a 30* dome on the top. at least i think thats what the spec was for the last template i custom made>??

 

i HAVE been imagineing in my head a completely differnt shape but i'm not sure how it will work SO i'm going to template a few and see how it fits hope they dont eat pistons i'm shooting for 80-85% width with NO triple ports.. ( im not thinking its going to work but hey>)

 

when i first started i trashed a few cylinders JUST to know what the limits were. knowing where the coolant passages are is important.

 

Ok, what I am trying t get at here is the theory I have been kicking around in my head; here's what you do..

 

1. Transfer the profile of your NON-flat port roof to a sheet of paper.

2. Transfer the profile to your piston in a way that the center is even with the piston crown.

3. Pie cut your piston, following the profile, going aproximately 2mm deep at the extremeties.

 

Seems to me like this would be worthwhile especially in a drag engine but I am just a little concernad with weakening of the piston and causing my powerband to narrow.

 

Oh, BTW cam on the other forum in the thread about the welded transfers I commented on your post about the c compared to the [ transfers . It involves epoxy....

Edited March 18, 2011 by SlowMoe

[SlowMoe]

.................................................................................................

[shanYE west]

WOW WEEE

 

here is my experience.

 

you need to have the exhaust as wide as possible ( as stated in those books from the 60s')

 

you should cut an extra tranfer port, window in there also ( as stated from the 60's as most motors from that era didnt have more than one trasfer port up each side)

 

the "tuned length " pipe has specs but to get it really right you need to build a FEW and play with the chamber to piston length cause thats not really know what works ( as stated in that book also)

 

i'd love to see an engeniering book from KTM about their 2 strokes and how they developed them also theroory's from HRC from the days of 500cc superbikes would be phenominal..

 

 

its interesting to see how the serval, and cub and other similar aftermarket cylinders are able to take things from those more modern 2 stroke desingns and push the limits through the roof of what was the norm even 10 years ago.

 

those 2 stroke books are intersting but again they have a lot of outdated therior's in them BUT are an EXCELLENT read if you are into this stuff. are they going to teach you how to port the holy hell out of your stockers MAYBE BUT its still going to be up to you to get it all to work.

 

i personally HATE a flat roof lately i have liked about a 30* dome on the top. at least i think thats what the spec was for the last template i custom made>??

 

i HAVE been imagineing in my head a completely differnt shape but i'm not sure how it will work SO i'm going to template a few and see how it fits hope they dont eat pistons i'm shooting for 80-85% width with NO triple ports.. ( im not thinking its going to work but hey>)

 

when i first started i trashed a few cylinders JUST to know what the limits were. knowing where the coolant passages are is important.

 

Cam, just a idea.. 80-85% width is attainable with a bridged exhaust..

[SlowMoe]

This is what I have in mind. Thoughts?

[BigRed350x]

Why weaken your piston when you could just raise the roof of the exhaust port?

[SlowMoe]

Why weaken your piston when you could just raise the roof of the exhaust port?

 

The idea is not to raise the port, but to make the port open all at once. look at the sketch the center of the cutout is even with the piston crown. This will not cause the port to open earlier just make the port open more abruptly once it cracks open.

I have been told that 1mm is safe to shave off the piston crown if doing so to increase port duration. I have gone as deep as 3mm with no ill effects, however the cuts were at the transfers so they were not as long.

In my experience as an API 510 inspector and by knowledge of the ASME pressure vessel codes, in a situation where the strength of a component in a pressure application is in question due to low thickness, the thickness along the critical plane may be averaged along a line in that plane. In other words if a pressure vessel, lets say a propane bottle for instance were subjected to a pressure of say 1000 psi it would take (hypothedically) .100" of thickness for that vessel not to rupture.

 

Now you can have local areas within that vessel that are below .100" as long as the average thickness along theaxial plane (a straight line drawn from head to head) no longer than 1/2 the vessel diameter is .100" or more.

 

I know that this is a different application but im my mind if milling .040" in a general area is safe, and 3mm in a (fairly) localized area is safe then it would be safe to cut the piston crown as shown in my diagram to 2mm or so deep at the extremeties, as long as you don't leave any stress risers (sharp corners).

 

Again, this is my theory but I feel as though the piston would have more than enough strength after cutting it as I described...

Edited March 22, 2011 by SlowMoe

[Burt Reynolds]

Here ya go.

1.Triple extra boost ports on banshees do just about nothing.Some people may have triple port cylinders that run great,but it not because of the triples.

2.You do not want to have the exhaust as wide as possible,its a give and take thing,the wider you have it the faster you will eat rings,same with the transfers.You need a happy medium for your riding style and mods,and piston style and shape.

3.You want to have space between your exhaust port and transfers,i was told at least 2mm.

4.From what i was told by several builders,and from mcdizzy,you want the transfers that are closer to the exhaust port aimed where they blow mixture straight across the top of the piston,and the other transfers to blow more upward.As well as running good it helps cool the rings. The transfer tunnels need to have a nice radius to them.

5.In most cases the transfers need to open/close up at the same time,so the the port roofs need to be even. I have seen some builders stager the primary and secondarys though.

6.You dont want the transfers and intake polished,the rough surface will aid in breaking up the fuel air more.

7.Making all the holes big is not what makes hp.

8.A good way for a novice like me to check someones work,is to measure from the deck to the port roofs,to see how even or uneven they are. A mm off here or there may not seem like a lot,but with porting it is a lot.

 

These are about all the porting standards,guidlines that i know

[BigRed350x]

I wouldn't chop my piston up like that.