Brendans cbr250 project... still.

ok, now before you go flying off the handle i am not attacking you........

what kind of fuckin 2nd rate cylinder head engineering joint did you go to?

number 1, volumetric efficiency is supposed to be measured with the valves in place and the valves opened to max lift. a measurement of VE with nothing in there is a waste of fuckin time, of course its gonna be at or near 100%, there is nothing in the bloody way.

number 2, i strongly believe that by porting off the lumps around the valve stem [and all of the protruding valve stem mind you] you have detrimentally effected the VE by increasing the cross sectional volume in the middle of the port while not concentrating on making it a gradual neat taper. if you suggest that you did, i call lies. i dont see any material build up inside your ports [high temp epoxy usually] for that to be true. honestly, did you do that porting job yourself? if not, please name them, i would love to give them a call and ask a few questions about their methods. i mean if they are going to butcher your ports like that and then do a valve out VE measurement and tell you "hey guy, we are fuckin awesome, look at this 100% figure!!" and keep a straight face, they are either deadshits or dumbshits...

i suggest you get it all taken back and get it re-measured if you want a reading that you can actually stand behind and say is accurate...

/constructive criticism

mootavic said:

ok, now before you go flying off the handle i am not attacking you........

what kind of fuckin 2nd rate cylinder head engineering joint did you go to?

number 1, volumetric efficiency is supposed to be measured with the valves in place and the valves opened to max lift. a measurement of VE with nothing in there is a waste of fuckin time, of course its gonna be at or near 100%, there is nothing in the bloody way.

Click to expand...

ok lol... when you asked valves in or valves out... I presumed you ment open... (mind you its pretty hard to flow them if the valves are shut obviously enough) but generally speaking, you don't flowtest heads without the valves in place... thats just silly... i wasn't sure what you were askin to tell the truth... so i took a stab. I admit I fail at english... it was totally the wrong word used... I even said off :/

Regardless, the VE was not obtained via a direct measurement, that is impossible... its actually a calculation. RPM engine displacement and mass flowrate/velocity is all known... so it can be then calculated... That is why it is expressed as a ratio or a percentage. in otherwords... the ports have been opened right up via the removal of some of the valve stem... thats pretty standard practice when it comes to porting. but i will elaborate more on that in a sec...

number 2, i strongly believe that by porting off the lumps around the valve stem [and all of the protruding valve stem mind you] you have detrimentally effected the VE by increasing the cross sectional volume in the middle of the port while not concentrating on making it a gradual neat taper. if you suggest that you did, i call lies. i dont see any material build up inside your ports [high temp epoxy usually] for that to be true. honestly, did you do that porting job yourself? if not, please name them, i would love to give them a call and ask a few questions about their methods. i mean if they are going to butcher your ports like that and then do a valve out VE measurement and tell you "hey guy, we are fuckin awesome, look at this 100% figure!!" and keep a straight face, they are either deadshits or dumbshits...

Click to expand...

lol, ok. Now, what I think what you were trying to say is that removing the valve stems detrimentally effected velocity by increasing cross sectional area, in turn decreasing VE as it is no longer sucking the gasses due to vacuum pressure after valve closure~opening... this couldn't be much further from the truth... allow me to explain...

Actually by removing the stems (in this case, please keep that in mind), the velocity was almost kept constant. (actually increased marginally due to increased mass flow rate from porting of the intake ports.) this is not because the stem has a neat taper, but infact, because the stem is quite an obstruction. a neat taper on the exhaust port isn`t as important (in this case as the goal of head performance is different to that of stock, please also keep this in mind) as say on the intake side... this is because increasing mass flow and decreasing resistance was more effective then trying to keep a laminar flow, however velocity is still important factor regardless, so it wasn`t completely disregarded... It didn`t effect the vacuum effect so much on valve closure as the ID of the exhaust is still the same and the exhaust port length is very short. Increasing the volume of the exhaust port dramatically increases low lift flow figures. It behaves completely different now.

So this epoxy you speak of, is called zedspa... Lucky enough I didn`t need it in this situation. (if I bored the sleeves thus increasing displacement I would have needed it to change the overall profile... but I would still have a larger internal cross sectional area. there is enough material on the roof of the port. Don`t worry, too much wasn`t removed.

The company that benched it is called "Ghea Race Engines". The bloke who worked on it, his name is Anthony (founder of the company)... and he knows his shit. Actually he has retired now (last time I checked)... he was getting abit old and the labouring work is hard on old people .

I'm not sure if the business is still continuing... but let us know if you found out anything interesting.

In regards to your C/head, as far as I know... you didn`t even bench smokeys head...so it would of taken a miracle to balance them... and all that polishing was a complete waste of time. that would have got you about 1% of 45ps or maybe even less... which is absolute FA. I'm trying not to be so sensitive... but it does seem kinda like you are trying to take a dig at me... swearing and all. but I will overlook that for now.

*edit* just added some bold to highlight something worth lolling about... there is no such thing as cross sectional volume.

*edit*edit* just thought I would point out that tapers in fluid mechanics are designed to decrease turbulence which effects head loss. dont forget that air is compressable, and when it is at a lower density, a volume flowrate increases when the mass flow rate stays constant. I expected you to know that.

*edit*edit*edit* just also thought that I would point out that the floor of the port wasnt touched so that a uniform cross sectional area could be maintained. if i cut that short turn radius... it would have caused problems.

banana.logic said:

Hessian said:

Hows the karate going?

Click to expand...

Click to expand...

funnyly enough, I had Kendo last night.

banana.logic said:

Hessian said:

Hows the karate going?

Click to expand...

Click to expand...

no need to be a dick

of course you had the valves in. otherwise your engineer is a fuckin retard. good to see you know oh-so-much about the maths behind it but dont even know how to read or comprehend basic english. its not like i've got such an awfully illiterate writing style...

that being said, i didnt mean volume i meant area [so i made a typo, sorry...] and i certainly didnt mean velocity i did actually mean the overall VE of the ports.

what i am trying to tell you is that if you took as much meat out of that area as has obviously been removed you have created a larger cross sectional area ALL along that part of the port. this would mean that according to bernoulli's principle, that since the OEM ports were designed to have a steady and gradually decreasing cross sectional area [to steadily increase velocity to peak at the valve seat] that your now larger centre section of your port will have a sudden decrease in velocity [due to less pressure] followed by a dramatic and abrupt [rather than gradual] increase in velocity as the port suddenly chokes off before the seat. whilst i understand that air is compressible, do you understand the ramifications of this? this WILL cause a large turbulent low pressure area in the centre of the port which will mean that you will almost certainly not get as much air into the cylinder as you would if the cross sectional area had remained at a gradual taper. if you do not believe this, then you fail to grasp the most basic part of the function of the ports. fair enough, the stock ports look ugly, but they are damn efficient and are more than likely at or near 100% to start with on this motor especially considering the high power:capacity it churns out. out of curiosity did you get a baseline VE figure to work off before your changes?

regarding my porting job, unlike you i didnt have daddy's money to throw at an engineer to use a flow bench and to do all my work for me but i did do a shiteload of reading up on port geometry and and regarding the "balancing" problem you suggested. im not completely fuckin retarded to just randomly port out material without ensuring all the ports are as close to identical as possible. i did a volume check on each port and they were all within .25ccs of the baseline port i did. that was a bastard. i also did not significantly change the port geometry [especially the short turn radius] because having sectioned a head, i know exactly how little meat there is to the water jackets. the exhaust ports were almost completely unchaged apart from the mirror finish and the port matching to the header flange, which had its own step which would have helped prevent reversion on overlap.

i do realise that even if your head makes the bike perform worse you will still come back and say "OMG its awesome" because you are completely unable to admit when you have ever done anything wrong, ie, every single time you have been banned. let alone this, when you have paid for someone to do your work for you so trying to tell you that anything even remotely detrimental has been done is an exercise in futility. all you wanted was to come on here and say "i is the greatest, bask in my fat wallet glory and feed at the teat which is my mechanical prowess"

though in all honesty, i would love to be proven wrong and know that everything ive read and been taught is wrong and that you can just ignore large parts of fluid dynamics that don't suit you and just take the bits that work for you. i didnt know engineering was like religion...

in any case, how many cc's have you increased the squish volume by? have you calculated how low you have dropped your compression ratio to? have you thought about how much that will affect your overall horsepower gains? looks like at least 1cc at a minimum. thats an increase of 20% which is going to be a metric shitload less compression, moreso since you have definitely taken more than 1cc off each piston face fly cutting your pistons.

actualy... mommy paid for it all. every cent! she always does that for me... and I dont even say thanks! hahaha!!!! its great having a rich family

and yeah... I actualy had no idea what I was talking about... i actualy made it all up. you caught me out. hahaha good one moot! nudge nudge

now its time for you to bask in the glory as the people of cbr forums blindly chant "moot" "moot" "moot".

I am sure there will be a party and a fund raiser waiting for you...

god bless all backyard engineers!!!!

after maybe 30 minutes of fuming... I now get it... you were trolling me... I almost took the bait... ALMOST!!! hahaha

that is pretty funny

its been fun playing with you moot. I really hope you have a great day! I love you moot! more than myself!

trying to help me? are you out of your mind? it couldnt be any more negative/insulting. it is obvious his objective is to put me down/feel embarrest about whatever work I have done to my bike, so in tern he can feel good about his own accomplishments. that arse has NEVER... I repeat; NEVER helped or try to help me. its always been about his selfish prerogatives.

perhaps you have a problem with empathy... you can not detect any negative energy.

100% unprovoked.

This web community is seriously taking its toll on my mental health. I do not need every post nit picked to the very last detail. I explained my post (before last) in a very respectful manner... but ofcourse it makes no difference... its just always attack attack attack.

there was alot of things I wanted to say to moot, but unfortunatly i find his disrespectful attitude too distracting... and I cant talk about the things I wanted to in the first place.

I really really wish you guys would tone down the swearing and general aggressiveness... but unfortunatly, you blokes feel its gay to censor your posts because you guys dont give a flying f who you are talking to.

because of this flack I have been recieving... especialy from you, Rich, you have been nothing but offensive, insulting and obscene to me. And this is resulting in a breakdown in my social confidence now to a daily extent.

please quote me where i am having a go at moot, and I can quote you 10x more where he is having a go at me. if you are not interested or what to be more male/testosterone or whatever you want to call it, then go and pumps some wieghts and drink some protien shakes... just for the love of god, stop acting like a child.