Highspeed Valve Springs

[Barnesd09]

On the lookout for information about valve springs and everything else that goes with it that would be stable up to the range of about 17000 rpm, or if its even possible with a modified horizontal engine......

 

[rumble]

What a great teaser thread. Have you started the build or just in planning stages.

 

[sean01]

akunar uses high speed products.. email them your valves installed height and the cam valve lift..

is this for a china engine or a crf150?

but all i can say is for 17k rpm your going to need 1 piece stainless valves, custom retainers and cnc valve locks.. just the seat pressure alone will be pretty big then you have the full valve lift spring pressure.. enough to wipe a lobe of a cam in no time lol..
talking short cuts for this type of build will result in mass destruction lol..

just 1 question tho.. why so much rpm.. rpm builds hand grenades lol..
a better engine would be a low rpm HIGH compression engine..Mmmmm methanol..
10-13k rpm is heaps.. but i spose at the end of the day if its a china engine then it will end bad anyways lolz.. but i want pics

oh and just out of curiosity, what is the cam profile your using. it sounds like it would have 8mm+ lift and mass duration..

 

[The_GDFP]

You might take a look at the modern street sport bikes for an idea of valve mass vs spring rate, breathing area/cc and such. Might even end up swiping some components. You'll have cam chain hysteresis, ring flutter, brutal friction, component flex among others to overcome. Then you need a cam designed to run at these speeds. I've looked in to such a project, but haven't the time or resources to do it right, right now. I'll be watching

 

[Barnesd09]

Thanks for the heads up on what needs to be looked at. I'll be taking the idea to an engineer to so he can have his thoughts on the idea and if he knows the people to build these kinds on things.
The idea came from looking at motogp and moto2 & 3 engine design rules and how they achive high rpm. As we all know more rpm for a given volume = more air and fuel which = more power, well basic theory.
It is for a china engine. The older suzuki 250 across has a redline up at 16500 so I can't see why this can't be achive with one of our engines.

 

[MiniFighter]

The older suzuki 250 across has a redline up at 16500 so I can't see why this can't be achive with one of our engines.

The CBR250RR had a 81K + redline, Tacho went to 20K lol

Thats all i can input to this thread as im not smart enough to comment on anything else :lol_hitting:

 

[sean01]

ok well the across 250 is a 4cyl right?
thus meaning it has very small bore diameter and strokes which alloy it rev to the moon.. very low rotating mass per cyl.. and im guessing a rod ratio of around 2:1
and 12.8:1 compression.

also a twin cam head and 12.8:1 comp which you will need maybe even as high as 13:1 would suit..

china engines are considered pretty big in the bore and stroke..

i think you will need a short stroke, long rod and matching sized piston. a rod ratio of about 1.9:1 - 2:1 would be good..

cam choice is the next problem, 1 the perfect cam doesn't exist nor do manufactures give out true specs.. compression has a lot to do with it as well..
cam choice doesn't need to be thought about till you work out your rod ratio and displacement..

personally i think you've chosen the wrong engine for this build. not saying its going to be impossible but your pocket will have holes in it by the time your done lol..

you have a big journey ahead of you.. have fun lol..

 

[Barnesd09]

I was looking at a 70mm piston and 41.5mm stroke. but then I don't think that fits inside the studs of YX/HO/daytona engine. Looks like its another one of those ideas that is just to labour and money intensive for the net result.

 

[The_GDFP]

70mm will fit

 

[Barnesd09]

So further to my search for rpm I started looking at bore/stroke ratio's
MotoGP rules allow 4 cylinders and a max bore of 81mm.
If using the maximum bore that gives us a stroke of 48.4mm
a ratio of 1.67
The new moto3 engine is a single cylinder so probably more in line with a china engine and a more achievable goal. The moto3 engine is 78mm bore with a 52.2mm stroke, a ratio of 1.49, but peak power is at 13k rpm. So in seeing this the 17k target is probably way to far beyond the capable limits of a single cylinder engine.

now if I put a 67mm bore and a 45mm storke I achieve a ratio of 1.49, same as a moto3 engine.
So that is where i will start, It will be a ground up build and will no doubt need a custom crank and rod built.:deadhorse:

 

[sean01]

concentrate on rod ratio...
you want the least amount of rod angle. that will allow nice high RPM's it will also reduce piston and bore wear..

 

[sean01]

lol i being think about this a bit, and to better explain the importance of rod ratio and what effects it can have i'll use the ford V8 351C engine.. better known as a clevo

in standard form they wont play nice when applying massive cams to where the rpm range exceeds 6500.
now just buy using ford 302C rods (which are longer than 351C rods) and a piston with the piston pin higher up (closer to top) it allows them to rev much higher.. this also allows a shorter piston to be used which also reduces bore friction.. so its a win win in all accounts.

knife edging the crank and lightening everything where possible helps too.. but it could sacrifice a little torque in a smaller engine.. but then again rpm doesn't build torque so you have to chose what you want lol

 

[Barnesd09]

lol i being think about this a bit, and to better explain the importance of rod ratio and what effects it can have i'll use the ford V8 351C engine.. better known as a clevo

in standard form they wont play nice when applying massive cams to where the rpm range exceeds 6500.
now just buy using ford 302C rods (which are longer than 351C rods) and a piston with the piston pin higher up (closer to top) it allows them to rev much higher.. this also allows a shorter piston to be used which also reduces bore friction.. so its a win win in all accounts.

knife edging the crank and lightening everything where possible helps too.. but it could sacrifice a little torque in a smaller engine.. but then again rpm doesn't build torque so you have to chose what you want lol

So in taking this, if I was to say keep a stock yx160 barrel length, deck height and crank position, then have a crank, rod and piston with the pin high up custom made, say something like a crf450r piston design, this would go a long way to help with higher rpm.

 

[The_GDFP]

There's a ton of additional variables in "optimizing" r/s ratios. Ports, cam, timing, desired torque curve, etc all play in to it. B/S ratios also have similar issues. Volume/surface ratios alter thermodynamic efficiency. If the sole goal is maximum revs the big bore allows more breathing area. Modern cam and port design, along with improved ring packages, allow more stroke at a given RPM than in decades past.
Just a few more pickles in the pudding

 

[dafunk]

my 2 cents worth

we know how the longer rod reduce frictional losses using better angles
but does the extra wieght of the reciprocating mass hinder high revs ?

big bore short stroke , biggest\LIGHTEST valves ti and valve train alloy roller rockers ti spring caps and ti collets then use lightest springs possible
the weight of all things moving in a open\closed , up \down , in\out , start stop motion
is important for high revs imho

 

[sean01]

you can use wat ever bore/stroke you want as long as you try to retain a high rod ratio..

displacement builds power and the rod ratio will build rpm.. the 2 together has the potential of a killer engine.. also the potential of a hand grenade lol..

unfortunately you will need heavy valve springs as light ones will float early in the power curve.. you might also want to consider 1 piece stainless or Ti valves.. than many rev's will soon see a normal valve pull in 2 peices
the taky 4v superhead may end up being your friend but you might end up having to custom grind a cam..

 

[dafunk]

im afraid if a large bore short stroke is not used then the size of the valves will be comprimised
also ti being so much lighter at those rpm every gram counts and stainless is a lot heavier
imho

 

[grnman]

Just a thought. could you look at what materials are used, what weight they are and what cam profile is in a R6? i guess its got 4x 150cc piston's so there could be some light in there.

does it get to a point where there is only so long you can go with the rod length as it will come close at full angle to the bottom of the barrel. is this the rod length limitation or are there also side effects of having the pin so close to the top of the piston?

 

[sean01]

yeah obviously there is a limit to rod length, the longer it gets the higher up the piston the pin is.. but it is not uncommon for pins to be under ring grooves but firstly you need a piston available.

and yeah Ti is heaps light and can be used but they will need to be check all the time..
just like honda's, rule number 1. if you want reliability then toss the Ti valves and go stainless..

anyways theres more than 1 way to skin a cat so do lots of home work and dont give up if you think its worth it