Bore/CC mesurment ques

[MTS]

ok so my question is this, my friend has a 200m he thinks borin it 2nd oversized will increas the bottem end of the bike majorly and that it will pull much better, i said no it will hardly be a diffrence not enough to feel, and then my other friend thinks borin it 50 thous over will make it a 250 ! so what i need is how to figure out the ccs of the bike
thanks for the help in fixin this confzzzelment :wondering

[greenhuman]

Bore x bore x .7854 x stroke.
65.5 x 65.5 x .7854 x 57.8 = 194.7cc 191.7cc is standard

[Studytime]

CC's of the bike,

You're figuring the volume of ONE cylinder.

V = Pi x radius^2 x height

or an engine cylinder would be;

Volume is Pi x (bore^2)/4 x stroke. A "50 thousands" over bore is actually an increase of .050" in bore diameter.

Use these very simple formulas to solve for volume. Work them out and spend 15 minutes doing these calcutions and this will stick with you.

Also, for more calculations,

What 8-cylinder engine has a bore of 4.00" and a stroke of 3.48"? You should round up to the next full cubic inch, that's what GM did.

Studytime

[MTS]

thanks guys, i have it all hear in one of my mechnics books but couldent really make ends meat of it lol green human bout naild it for me :) plain and simple lol

[Dan Tenn]

something is wrong here. You have V = Pi x radius^2 x height, then go to Pi x (bore/4)^2 x stroke. Where radius = bore/4. This is wrong.

This is correct:
bore = diameter = 2 X radius or radius = bore/2

[TimSr]

Bore x bore x .7854 x stroke.
65.5 x 65.5 x .7854 x 57.8 = 194.7cc 191.7cc is standard

This is the simple formula used by AMA and CRA, but in order for it to work, you have to convert the .050" into 1.25mm. Your calculations are for .50mm which is .020" overbore.

66.5 x 66.5 x .7854 x 57.8 = 200.75

Either way, boring is not a performance modification, it is a wear and tear fix, but if someone likes throwing money away for no noticeable gain, its good for the economy, anyways!

[Studytime]

something is wrong here. You have V = Pi x radius^2 x height, then go to Pi x (bore/4)^2 x stroke. Where radius = bore/4. This is wrong.

This is correct:
bore = diameter = 2 X radius or radius = bore/2

Yes sir, you would be right. I had (B/4)^2 instead of (Bsquared/4). I'll go back and fix it.

I think it's important to understand the formula and not just know a generic sequence of numbers to multiply.

Good catch Dan.

Studytime

[greenhuman]

2nd oversize is half a mm. The standard bore is 65mm so 2nd oversize is 65.5mm. That's what he originally asked. If you want to spend 5 seconds working out your cc's, do it my way. If you want to get a headache do it their way. The standard bore is 65mm + 1.25mm =66.25 which = 199.24cc

[Studytime]

2nd oversize is half a mm. The standard bore is 65mm so 2nd oversize is 65.5mm. That's what he originally asked. If you want to spend 5 seconds working out your cc's, do it my way. If you want to get a headache do it their way. The standard bore is 65mm + 1.25mm =66.25 which = 199.24cc

If simple algebra give you a "headace", you have no business building a motor at all in my opinion. I'm directing that to anyone, not just you Greenhuman.


Studytime

[Studytime]

OH, does anybody want to take a stab at where .7854 came from?

Studytime

[greenhuman]

If you can't spell headache you have no business telling everyone how to do algebra in my opinion. My people could not care less where it comes from as long as it works.

[OldSchoolin86]

If you want really simple just get the free virtual engine calculator from http://www.virtualengine2000.com/index.htm
It's kind of nice when you figure it out, easier then doing the math.
Now if your extreamly lazy just look up the .pdf files at www.wiseco.com
They got almost everything worked out for you already.

[Studytime]

Greenhuman, you win. Your method is way better. Nice and mindless. I guess I wasn't smart enough to see the exact word in your post.

On a serious note, typoes happen when you use two hands. :) :) Hahaha... Yeah, there are a lot of words I do not know how to spell and simple ones that I just forget. I'm sure everyone knows of www.dictionary.com- an invaluabe resource to not look like an idiot.

Gave a good Thanksgiving.


Studtyime

[4cylinders]

hey, the wiseco catalog lists the cc with the bore size

[Studytime]

That's even simpler to use and really clears up the confusion.

Couldn't be any easier!

Studytime

[Dan Tenn]

Listen up. The reason for understanding the formula for finding cc's are as follows:

1. Just remembering simple formula for area of a cylinder.

2. This formula can be used to find the volume of any cylinder.

3. Part of the formula can be used to find the area of a circle.

4. The hardest part of trouble-shooting is understanding how things are supposed to work, ie: If you dont understand the formula, how do you know its correct?

Volume of cylinder (V) = Area of base X Height = (Pi) X r^2 X H

Area of base = Area of Circle = (Pi) X r^2

Pi = 3.14

r = radius = 1/2 diameter = 1/2 engine bore.

H = height = Stroke

Be sure to convert to centimeters for CC's.

CC's = (3.14) X (1/2 bore)^2 X Stroke

[Studytime]

:) :) :) :) Hey, that's a very clear way to lay it all out.

Like you said, if you're just plugging numbers intoa formula how do you even know if you're right.

Studytime

[greenhuman]

Where is the problem with the nice simple method of working out CC's? It does work, no question. The guy is not troubleshooting, he just wanted to know the CC's of his friends trike, not get brain damaged and try and work out the world's problems.
K.I.S.S keep it simple stupid.

[MTS]

yes greenhuman i like that K.I.S.S if it sounds right it must be right lol

[Studytime]

Embrace learning. You'll go places!

Studytime

[MTS]

yes i know, i understand your point of view and greenhumans too, i have learnd alot from this post and i thank you ppl for helping me :p

[greenhuman]

I've already been places. If your version of going places means tossing around gobblydock confusing poor blokes when all they need is simple straight answers to simple straight questions, I don't want to go there anyway.

[Studytime]

I've already been places. If your version of going places means tossing around gobblydock confusing poor blokes when all they need is simple straight answers to simple straight questions, I don't want to go there anyway.

Well, I didn't mean to confuse you there "greenhuman". The "poor bloke" you spoke of caught right on (see below).


... i have learnd alot from this post and i thank you ppl for helping me :p

Also, a defining moment in an engine builder's life is when he realizes that it takes more than just being a gearhead to design/build good motors. It requires more learning than a set of wrenches and an engine will give. Again, the operative word there is learning .

On another note, glad to see you've already been places. When I say that atleast I'll understand what the tour guide is saying. I came up with this analogy, you go on tour of the Holy lands only to stand with your mouth open wondering just what the heck your hebrew tour guide is telling you.

I go and get an english speaking tour guide.

The goodnews is that it's not too late greenhuman. Not too late.

Studytime

[mwill15]

I'm kinda new here, but I've been reading this thread and decided to put in my 2 cents.

Sometimes its nice to keep it simple, but if we all did that where would we be. Lord knows we don't want to confuse anyone with this 5th grade level math; grow up! It is extremely important to know where numbers come from and not just the easiest way to get them. "keeping it simple" also makes it easy to have eroneous answers (or 'wrong answers' for those I don't want to give a headache).

There it is, like it or not. Just keep in mind this is my opinion, and everyone has one. The only differnce is that mine is right!

[mwill15]

I've already been places. If your version of going places means tossing around gobblydock confusing poor blokes when all they need is simple straight answers to simple straight questions, I don't want to go there anyway.


"gobblydock;" WTF!?

[mwill15]

Thanks; Now I completely understand what he was saying.

[greenhuman]

Nerd Alert !!!

[mwill15]

WOW! That was mature.

I guess I have to drop out of college now so that I am not labeled a nerd.

P.S. (just for greenhuman): College is where people go to further their education. Can you believe that, there are actually people who want to learn, and go out of their way in order to do it!