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