RK Tek

Your compression ratio is too high....causing your top end to stagnate.. You could back off the timing or get some lower compression domes. Kelsey

There seems to be many misconceptions regarding what higher octane fuel will do and NOT do..... 1st major myth is that higher octane fuels burn at a slower rate.. This is entirely false!! 89 octane and 110 octane will burn at the same rate once ignited.. What the 110 octane will do that the 89 octane will not ...is resist combustion longer given the same internal engine conditions. In other words... the 110 will be able to withstand rising cylinder/head pressures longer before combusting than the 89 octane. Once combusted... ALL is equal between the 2 (well ... anything measureable). Running a higher octane fuel than needed in an engine will not add power. Will it lose power??? Yes, sometimes... but only because the engine will have been running in an "un-tuned" state and that is what is causing the performance loss. The un-tuned staed could be remedied by different jetting or timing or both but it is not the fuel causing the performance loss.. it is the fact that you have place the engine in an un-tuned state because of feeding it an octane that is not needed. Once you tune the engine for the new fuel's octane.. it will run as it did before. not any better and not any less. YEARS ago I aided Martin Saint and Dan Wade in writing an article that addresses these very issues. It is located here: RACE FUEL MYTHS. It may be a good read for some of you. Kelsey

Patriot.. EXACTLY!!!!... custom tailored ANYTHING will perform better and add reliability whether it be porting or combustion chambers. The fact remains... if you have the engine custom built .. it WILL make morepower and be MORE reliable!! It does seem strange that people will call around asking for a "trail", "dune" race", "mild race" port job but then they "Skimp" on the power making process ..COMBUSTION!! They are probably MORE custom chamber configurations then there are port layouts! Kelsey

Duece... If you think that the BSpolice know what he is talking about.. you are sadly mistaken.. If you are using standard off the shelf domes on your 4mm stroker engine.. I can GAURANTEE you more power with a proper dome. Did I mention I would gaurantee it?? I would be very interested in knowing which engine builders you spoke with that informed you you did not need custom domes, FOR BETTER POWER, for a custom stroker engine. You mentioned it.. so please let's hear the builders that stated such. Let me know Kelsey

Boonman and . , I guess we are in agreement (somewhat anyway). Funny.. My 1st guess on who BSpolice really was was ole' boonman Oh well.... Duece.. I would be happy to explain the reason for why what I am stating is true but I obviously have failed at that with you , at least through writing. If you want to call me maybe I could do a better job. Kelsey

.... Well.. it appears that we will have to agree to disagree on this one. 1st of all.. there is not an explosion in combustion.. there is combustion which is quite different than an explosion. You did some math and increase psi in the engine with the "5x" method.. BUT.. what you did not seem to understand was that if you have a head that combusts 60% of the F/A mix and you have another head that combusts say 75% f the mix... what does that do to the resultant forces acting on the piston?? Ya see.. this is the whole point.. it is about efficiency ... in otherwords.. how well the head does at combusting what is given to it.. if you have a head that combusts a higher percentage.. you WILL have more power than one that combusts a lower %...Make sense?? So when you are talking psi vs psi the lower psi chamber may have a higher effciency and therefore create more push on the crank train. F/A that is trapped in the head and not combusted does NOTHING to aid the push on the piston.. So. if the head is such.. the energy created is not as great as a head that does not have a lot of trapped F/A mix that is not combusted Kelsey

..... I missed this earlier so I thought you may want an answer. Here is a HUGE misconception among people... The 150,160,190 PSI...etc. etc. cranking compression is NOT, I repeat NOT the internal pressure in your engine!! There is not an exact formula (that I know of) to determine the actual cylinder pressures during engine operation...BUT I can tell you that the internal cylinder pressures will be in the magnitude of 4-6 times (if not more) of the cylinder cranking compression. So.. equating the cranking PSI with the "push" on the piston is not relevant because once combustion occurs... the cylinder pressures sky-rocket! So, the 40PSI difference in cranking compression is miniscule(sp) in terms of the pressures your engine is actually experiencing. Ya see... cranking compresion means very little in terms of what is really going on inside your engine! Your engine's function is to take heat and transform it into mechanical work. The amount of work that will be performed is largely based on the efficiency of this heat conversion. In otherwords... the more effectively your engine (through combustion) can convert the heat to work.. the more work you will perform and hence the more power you can realize. This is why having a combustion process that is efficient can make your engine realize its full potential. Having a combustion process that is inefficient WILL make less power!!!So, even if you have an engine that has 60PSI more cranking compression than another engine ... If the engine with the lesser cranking compression is more efficient and can create more energy and push on the piston.. it WILL make more power! Heat losses due to imperfect or incomplete combustion have a serious effect on the power that can be developed in the cylinder. Because of the short interval of time necessary for the cycle in modern engines, complete combustion is not possible; but heat losses can be kept to a minimum if the engine is kept in proper adjustment Another common misconception is that the radial tension of the piston rings is what keeps the ring sealed against the cylinder wall.. But that is a whole other subject. Hope this answered your question. Kelsey

YES!.. I am not sureon the 135 thing but more like 140-150. LIke I said, I don't give a damn about the cranking compression... it means nothing to me but a health check of the engine.. you know a snapshot of the engine's "health". What your PSI comes in at depends on many factors like Air density of the day. how fasy your kicking it, porting, elevation and a few others. When you state you are going from 18cc to 20cc domes and loosing power.. I can believe that because you are switching to a 20cc dome of the same poor design rather than a 20cc dome that is tailer made for your engine. So, yes, switching from a wrong dome to another wrong.. you could gain or lose power.. but switching from a 18cc wrong domes to a 20cc correct dome could certainly add power and engine reliability. Kelsey

dlnoss... This is the problem with forums.. people cannot hear the tone that is in the typing. Everybody hears a different tone and you hear a snotting tone when, I can assure, you that is not the intended tone. Inotherwords... I in NO MEANS stating that I am the only on on here that knows anything about combustion. What I am saying is that I DO know something about it. The BHQ people may want to ask themselves why there are not many (if any) full fledged performance shops posting on this site. If you go down the posters in this forum you will not find many (if any). IMHO.. it is because anytime somebody posts something they get these type of responses. It seems ironic because the ones that know and FREELY post informative threads can only help improve the knowledge of those who did not know. BUT they get "flamed" because they do so. For example... The last fiasco with me on here.. You realized that your compression PSI chart was incorrect and changed it. You also realized that the porting of an engine effects the PSI of an engine and, consequently; you added this info in your webite.. Ya see.. information was exchanged and mis information was fixed. Now you seem to ask about the porting state of the engine before you recommend a dome size where before you did not. So, that whole fiasco became a positive for you. If it had not happend.. your PSI chart would read as it did before. My point??? It is NOT to talk down to you.. It IS to point out that if people would listen without predjudice... then there could be a good information exchange(on ANY subject) between people. But instead it seems to always turn into a bashing session. Kelsey

oilsmoke.. 1st you need to decide what octane you want to run. Then you can decide on a compression ratio that will accomodate that ocatane requirement. 19cc?? who knows... Think of this... say you engine has a negative deck height of .015". That can ad between 1.225 and 1.3 cc's to your overall trapped volume..So.. now, your 19cc dome just became a 20.225 or a 20.3cc dome depending on your bore size. You just lowered your compression ratio quite a bit(over 2.3 points) and , more importantly, you just upset the squish effects of the engine to a point where you MAY have detonation issues. OK.. take that the other direction.. you have a positive deck ht of .015" now your 19cc domes just became 17.8 (roughly)cc's and you raised lowered your trapped volume and raised compression ratio up at least 2.3 points on the compression ratio scale, possible more depending on the bore size. NOW, you may have serious reliability issues or it could run like a scalded dog.. ya see.... it is NOT about the flat plate volume of the domes.. it IS about what is added or taken away due to the engine specs and how these engine specs effect the combustion process in terms of squish action, heat, and flame propagation . Make sense? Kelsey

Oilsmoke.... I don't quite understand your question or statement: Or maybe I do.... The head design does not increase octane.. It may increase the octane requirement of the engine (is that what you are trying to say?) The Cranking PSI does not tell you octane requirement. I have several engines that crank over at 140-150 PSI than will not live on anything less then 110 ocatane BSPOLICE.. Nice!!! you joined today, or should I say... came up with another alias from your everyday BHQ name, just so you could post a thread and not have people know who you really are!!! GEEEZ.. I wonder who you could be? WOW... that is one smooth operation... Nice job!! By the way.. about my website.. Glad you hated it.. It is like I have been saying all along... if you want you want something that is the best you call on an expert in that field!! I am definitely no expert in the field of website design.. but I still can make one and it works! But there are better sites out there. Kelsey

Bense, I am in Idaho Feel free to phone me if you wish to discuss combustion Kelsey

Duece, First off... my head is not $340.00 it is $310.00. If you buy another aftermarket head and have custom domes made you are at the same price. As for PSI.. All I can say is that explained in this thread and HERE you can read more on why what I say is true. Or you can go to the SAE website and download, at a cost, 1000's of papers on internal combustion (like I do) and read it for yourself I am not State drag champion because I run high compression and advanced timing. I run lower compression and retarded timing. Go figure... In any case. If you really wanted to be convinced you would allow some of this info to sink in and not be dismissed because you do not completely understand it. If you have poor combustion chambers to begin with and then you up compression a bit and still have a poor combustion chamber then you may see some power increase but usually this increase only appears in the lower rpm range not in the upper band. In any case... if you are happy with the way your bike runs.. then that is cool. If you do not wish to improve it even further.. that is your call. Kelsey

Duece, Like I said,, some only hear what they want to hear and the rest goes out the other ear. I explained why a lower PSI engine can make more power. I also gave out other pertinent info regarding combustion and the internal workings of a 2 cycle engine. I also did not make reference to selling ANYBODY a dome in ANY of my posts. Please check for yourself.. There are no "selling" phrases. Screaming Banshee asked for some explainations of some aspects of combustion and I provided just that. Like I said.. no selling, NONE! just some information that, apparantly, most choose to ignore because they do not want to hear. I can show you a lower PSI engine making much more power then one with tons of cranking PSI but you probably would not want to hear that either. I'll tell you what...Ask Forcefed his cranking PSI and then ask how many races he loses. I mention him because he is one you know. Believe me, there are many others. Once again, Duece. THERE WAS NO SELLING GOING ON IN ANY OF MY POSTS!! I came to the conclusion ,,LONG AGO, that the BHQ people much prefer "Shiney" over "Powerful, Reliable, and Shiney" so, believe me, coming on BHQ with the idea of make a sale or two is FAR, FAR from my mind. And once again, Duece.. I thank you for keeping it civil this time. I do appreciate it Kelsey

Remember also...that the trapped volume can be accomplished in MANY ways. What dome you need will be dependent on deck height. Kelsey

norton, 13cc's trapped volume with your bore will yield a 15:1 untrapped compression ratio. This of course is considering that the dome is on Size, which it surely will not be at 65.5mm.. so there is another varible to throw in the mix. Hope this helps Kelsey

Jason, I do not think we can agree on that. For several reasons. Let's look a few points 1) The Banshee engine is .. What? 20 or so years old with the same cylinders. So.. say a guy picks ups a screaming deal on a 1988 Banshee . He was told that the engine is stock. Does this new owner know for sure that it is, indeed ,stock? Now, if it is still on it stock bore. .then that would be a miracle for 15 year old engine. SO... if the engine is overbored at all.. then the jugs have been off to SOMEBODY and who knows if they had to deck a few thou off the base or top? 2) Installing the aftermarket domes , I've seen, on a stock engine will probably cause a power loss.. not a power gain. Depending on the compression ratio selected. Installing a set of domes designed for a stock engine can yeild some performance gains.. but most of the combustion chamber designs (based on flat plate volume) that I have seen are not going to add much in the power arena IMHO. 3) Let's look, very briefly, at the internal combustion 2 cycle engine.... Every other stroke is a power stroke. thatis why it can make great power.. But there are many factors working against this process which robs power. For example... pumping losses, frictional losses, volumetric losses etc etc... Correct exhaust systems can aid in reducing these losses... Now.. think about it.. Where is the power being made in the engine?? What causes the "work" on the piston and its attached components??? Is it the pipes? NOPE! is it the Carbs?? NOPE! is it the reeds? NOPE! Hmmmm what actually causes the push on the piston? COMBUSTION!! While the carbs, pipes, and reeds all work together to help supply the required elements for combustion to take place... they are not doing anything that directly creates work on the crank train! All this is done in the Combustion Chamber Hmmm.. so it stands to reason that anything we can do to optimize the combustion process will add performance. Can we agree on that? It also stands to reason that anything we do to upset the combustion process will reduce performance. Now... combustion is not all about compression. There are countless things going on inside this process. It is KAOS! Some if this kaos is somewhat controllable. Other parts are not! The "key" is knowing enough about the controllable portions to be able to optimize it. This is not about compression!!! It is about squish action, cooling action, active radicals, flame front propagation, heat disappation etc... So.. the point being...proper compression ratio with improper squish action, flame propagation etc. will result in less than optimum combustion and can cause MAJOR stress on the entire crank train. So, IMHO.. changing flat plate volume is not the way to improve the combustion process.. The chamber's design is what will improve the process. Most of my chambers come in WAY under in terms of compression ratio compared to what people are/were running before. What makes the power is the design of the chamber and trying to controll as much KAOS as possible. Like I said in an above post.. Many of the crank failures people are experiencing are due to the head design. Bottom line... In the head is where the work is being performed. This is the area that needs MAJOR attention.. not MINOR. Just because the part raises compression numbers does not mean there will be added power. And if there is added power.. there could be unfavorable results down the road. Other bottom line.. on ANY engine that has been disassembled at ANY time in its life.. there exists the possibility of internal or external modifications being performed.. So, just because you have been told that your engine is not modified in any way.. does not mean it is true. Again.. those of you running those low cc domes.. are losing huge power!! If you want to read a snipit on cranking compression.. you are more than welcome. It is located on my webite under the "Tech Articles" section Kelsey

Screaming Banshee.... I have to respectfully disagree. The method is not proven because most do not know what changed when they added a new domes size. In fact..many on here state that they felt no power difference but it aided in cooling and looked good. Consider this... I just did a Banshee head for a customer and his engine builder ordered the head. I asked for application , fuel req, and deck ht. On the deck ht he told me standard deck ht. So, head went out.. customer put it on and the piston was smacking the head on the first run. So, he called me and asked me what was going on. I called the engine builder and asked him what he did to the cylinders. He told me what he did and all seemed fine. Then I asked the builder "did you deck any off the cylinders?" Response..... "Oh yah, I took .020" off the base of each jug" BINGO!! we have a winner!! So, point being... "proven over and over?" yes, maybe with some engines but not all. Would this problem have surfaced with some of the "off the shelf " domes/heads?.. I think so, if the piston would not have been smacking the head... the performance woud have been in the toilet FOR SURE!! So you state Well so were piston port engines for decades.. but they have been replaced by reeds and are condsidered obsolete in the industry. So, just because something has been around for years does not make it best option (By the Way.. I had the 1st Banshee head that utilizes the stock stud). Hell, if people did not improve on existing technology.. we would still be running steam engines. How fast would that be in 300ft? AHHH... didn't we already try that a few months back? I do not remember if your were part of that or not.. In any case... it seems that people on this forum only hear and believe what they want to believe and will not open up to new information. Which only hurts themselves and their engine's performance. So, while I would like to help.. you can not help those who do not really want to be helped.. make sense? A small example... I notice in some of the signatures on here people using 15cc , 16cc and 17cc domes. OH MY GOD! I can gaurantee you HUGE power gains from throwing those domes in the toilet!!! Especailly those with the 15 and 16cc domes!! You guys are killing your crank train and robbing your engine of some serious power!!!! DESPITE what the seat of the pants tells you. But I suspect I will get "flamed" for stating such WHY... SEE ABOVE PARAGRAPH!! Long story short... IMHO... purchasing heads based on flat plate volume (ie 18cc, 19cc etc.) is not a good way to add performance. Also... IMHO having a poor combustion process in your engine WILL lower engine reliability and CAN (normally will) cause severe engine failure to the bottom end (eventually) , as well as, the top end. What some do not realize is that their bottom end bearing is constantly getting hammered from improper combustion. Most think that when they lose a crank it is related to something other than the top end and combustion.. when IN FACT.. it is usually related totally to the head... So, think about that next time you lose a crank and can not figure out why! Anyway. Screaming Banshee.. I appreciate your civil responses and only wished more would follow your lead. Kelsey

Screaming Banshee... Thank you for not turning my "honest opinion" (note the word opinion) response into something it is not. 94 Banshee asked a question and I felt he got a incorrect answer. Nothing more!! This forum is directed at Performance shops. Performance shops are just that... performance shops.. meaning .. they know about engines and 2 stroke internal combustion and such. Just because a machine shop can make some performance parts does not make them experts at 2 stroke engines and internal combustion theory. NOTE: I am not directing this at ANYBODY.. just stating FACTS!! For example..If I was to go out and machine me up some wings for an airplane that will actually create lift and allow the plane to fly.. this does not make me an expert in aerodynamics and flight. It just means that I can machine out a part that will work for some applications. So what is the point of my ramblings... Well... if you frequent this site.. there are always questions being asked and the are always getting answered by one person or another. BUT a lot of the times the answers are incorrect .. BUT people take them as gospel. When somebody like, myself, sainty, or a few others contradicts the "gospel" they get "flamed" for having an" other than 'normal' answer" and then the thread growa with a bunch of name calling and nothing gets resolved. So, I guess my point is.. if you want just an answer, whether it be correct or not, then you will get one. BUT if you want a possibly more correct and pointed response to a specific question. then I suggest you aske an EXPERT in that field. whether that field be plumbing, heating, food, combustion etc. etc.. But the best answer will come from an expert in the field. You would not call a carpenter to plumb your new house. You would not order a hamburger in a Chinese resturant... would you? So, please do not take this post out of context.. You guys have been very successful at running me and others off this forum (for the most part).. but wrong information is just that.. wrong information. If you want wrong information.. then fine... get it. But I would suspect that most are looking for correct information and just because an outsider disagrees with a insider's view.. does not mean it is time to start a war against the outsider. Just take in the 2 views and decide for yourself what you want to believe.. Fair enough??? On another note.. my products are not designed at , how did you put it? "squeezing the most HP out of an engine" my products ARE designed at allowing for SAFE and reliable engine operation and adding some performance in there too. I still do not get why most on BHQ think that having a custom anything makes for MAX POWER! and loss in reliabiliy. When in fact.. it is quite the contrary.. a custom ANYTHING will be more tailered to the application and therfore; ADD (that's right ADD) reliability not remove it. Nuff said... I can't wait for the "flaming" Kelsey

This, IMHO, is so NOT TRUE! Basing dome selection on trapped compression ratio can get you into trouble very quickly. IMHO , of course! Kelsey

Norton, The safe compression ratio for your engine will be based on its application. For example.. are you racing 300ft? Hill shooting 1000ft? etc.. etc... The application will determine what you can safely get away with and still have reliability. It will also be dependant on the cylinder bore size. If you think you need 13cc TRAPPED volume .. then you need to determine your crown height. Are you using standard Banshee pistons? What is your piston deck height? There is NO standard deck height. They vary greatly. These things all need to be considered when determining chamber size. I compliment you on asking the questions.. Most do not and just buy a dome based on the flat plate volume of the dome. This is not the best way to build a high performance engine. Hope this answers a few of your ?'s. Feel free to ask more. Kelsey