SlowMoe Posted March 16, 2011 Report Share Posted March 16, 2011 I've read the 2 stroke books enough to know that a flat exhaust port roof vs an arched one for a fixed port duration will, theoredically give you: A. Higher peak hp due to increase in blowdown area B. Higher peak hp due to a stronger pulse wave C. A narrower powerband due to the strong but relatively short duration pulse D. Shorter ring life due to the abrupt return to the ring lands My question is, from real world testing/ experience, has anyone noticed a MEASURABLE increase in hp from the flat roof and Is there a perceivable narrowing of the powerband? In theory and most certainly in real life both of these would hold true but to what extent is the question. Any feedback is appreciated Slow Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted March 16, 2011 Report Share Posted March 16, 2011 Your digging into some builders' stash of secrets with this question. My guess is that you will get some pretty limited answers. Why don't you try and pick up a few sets of stock cylinders and try some different exhaust port shapes and do some testing. I prefer my exhaust ports to be triangle shaped. Quote Link to comment Share on other sites More sharing options...
SlowMoe Posted March 16, 2011 Author Report Share Posted March 16, 2011 Quote Link to comment Share on other sites More sharing options...
sheefreak Posted March 16, 2011 Report Share Posted March 16, 2011 There are a bunch of jackasses here who believe porting should only be left to the "experts". That is actually a fairly basic question that will gladly be answered on atvdragracers if you ask nicely. I do not know enough about porting personally to answer your question in depth. Quote Link to comment Share on other sites More sharing options...
Snopczynski Posted March 16, 2011 Report Share Posted March 16, 2011 This guy acts a lot like sloryder. Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted March 16, 2011 Report Share Posted March 16, 2011 That's what I've been thinking the whole time since I seen his 1st post. Quote Link to comment Share on other sites More sharing options...
SlowMoe Posted March 16, 2011 Author Report Share Posted March 16, 2011 Well I will tell you one thing this forum never changes. One helpful person out of every four is about par for this course. I am about to stop posting technical questions on here because there are apparently much better sites out there for that type of thing. To be honest I really didn't expect my question to be answered on here, I was just hoping perhaps everyone could maybe learn something here, as I planned on sharing information I gained from other sites with the members on here, but once again my gut instinct proves right and even though this IS a fairly basic question whose answer is likely known to 90% of the builders people out there, everyone acts like it should be super hush hush. I am willing to bet money that half of the builders out there would be happy to divulge this type of information, because as said earlier it probably is common knowledge amongst the pros out there, and to not divulge this type of information in fear of losing their compedetive edge would be something only a person, in my opinion, not intelligent enough to be doing this sort of thing in the first place would consider. 1 Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted March 16, 2011 Report Share Posted March 16, 2011 Well I will tell you one thing this forum never changes. One helpful person out of every four is about par for this course. I am about to stop posting technical questions on here because there are apparently much better sites out there for that type of thing. To be honest I really didn't expect my question to be answered on here, I was just hoping perhaps everyone could maybe learn something here, as I planned on sharing information I gained from other sites with the members on here, but once again my gut instinct proves right and even though this IS a fairly basic question whose answer is likely known to 90% of the builders people out there, everyone acts like it should be super hush hush. I am willing to bet money that half of the builders out there would be happy to divulge this type of information, because as said earlier it probably is common knowledge amongst the pros out there, and to not divulge this type of information in fear of losing their compedetive edge would be something only a person, in my opinion, not intelligent enough to be doing this sort of thing in the first place would consider. Well its a good thing I'm not a pro and don't do porting. lol Quote Link to comment Share on other sites More sharing options...
SlowMoe Posted March 16, 2011 Author Report Share Posted March 16, 2011 Well its a good thing I'm not a pro and don't do porting. lol So you're either stupid or just plain arrogant Just saying BTW how's Seminoe been lately? The last time I was in that area i believe it was flooded badly. Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted March 16, 2011 Report Share Posted March 16, 2011 (edited) It's been to many years and to many beers since I read that section in G. Jennings' book. The one thing I do recall is advice against to flat of a port roof, for exactly the reasons you already stated. Obviosly there is an advantage to opening a port completely quickly. It would probably make it a little more peaky but actually work better. JMHO, your results may and will vary. Might want to check this out http://www.lakesmotorsports.com/eshopprod_cat_508-9507-9481_product_99611.Banshee_Viper_Sleeves.htm. Many are unwilling to educate themselves themselves, invest some time and materials , pull their big boy pants up and do it themselves. Could you or I achieve the same power as someone with more experience? Of course not. Could I (you, us) work on an engine and make more power? Yes. Could I eff up a set of cylinders? Yes, if I were trying to get to close to the edge, or didn't do my calculations correctly. No guts, no glory. The only one thing that puzzles me is that if a pipe calculation is made off of exhaust timing (among other primary factors) , how does an engine builder measure the tuned length of any given pipe to get the best port timing for the best performance? I actually posed this question some time ago. Personally I would be interested in this "knowledge" you're willing to share. Be sure you indicate where you obtained it. Edited March 16, 2011 by Larry's Shee Quote Link to comment Share on other sites More sharing options...
WINDYCITYJOHN400 Posted March 16, 2011 Report Share Posted March 16, 2011 It's been to many years and to many beers since I read that section in G. Jennings' book. The one thing I do recall is advice against to flat of a port roof, for exactly the reasons you already stated. Obviosly there is an advantage to opening a port completely quickly. It would probably make it a little more peaky but actually work better. JMHO, your results may and will vary. Might want to check this out http://www.lakesmotorsports.com/eshopprod_cat_508-9507-9481_product_99611.Banshee_Viper_Sleeves.htm. Many are unwilling to educate themselves themselves, invest some time and materials , pull their big boy pants up and do it themselves. Could you or I achieve the same power as someone with more experience? Of course not. Could I (you, us) work on an engine and make more power? Yes. Could I eff up a set of cylinders? Yes, if I were trying to get to close to the edge, or didn't do my calculations correctly. No guts, no glory. The only one thing that puzzles me is that if a pipe calculation is made off of exhaust timing (among other primary factors) , how does an engine builder measure the tuned length of any given pipe to get the best port timing for the best performance? I actually posed this question some time ago. Personally I would be interested in this "knowledge" you're willing to share. Be sure you indicate where you obtained it. With the "Off the shelf" pipes (standard CPI SB-BB or Shearer SB-BB styles...even FMF) you can call and they will tell you what port timing ranges the pipes were designed to work with. Once you get into hand coned stuff, the pipe builder ususally builds the pipe to the motor specs based on Engine size and port timings. Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted March 17, 2011 Report Share Posted March 17, 2011 So you're either stupid or just plain arrogant Just saying BTW how's Seminoe been lately? The last time I was in that area i believe it was flooded badly. Or maybe both! ha! Its been closed to riding for the last two years. Just due to the height of the lake. If it ever dries up a little they open some more of the trails up. The last time I stopped by to check things out all the trails leading to the big hill were under water. You could only get to it from the north west. - Jared Quote Link to comment Share on other sites More sharing options...
AKheathen Posted March 17, 2011 Report Share Posted March 17, 2011 omfg...... didn't you get banned? i know you should have....for good reason, too. the problem with you and this site.....is you..... 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. 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. 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 Quote Link to comment Share on other sites More sharing options...
mikechief Posted March 17, 2011 Report Share Posted March 17, 2011 omfg...... didn't you get banned? i know you should have....for good reason, too. the problem with you and this site.....is you..... 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. 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. 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 SHHHHHHHHH you sound like you got some grease on your purse......fuckn cunt Quote Link to comment Share on other sites More sharing options...
mikechief Posted March 17, 2011 Report Share Posted March 17, 2011 pipes are designed for specific rpm port duration and area determine rpm 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.