Lolmathparty

[MF DOOM]

Ive googled and googled and googled and even tried bing for the first time and i still cant get it. Im assuming im screwing up the math somewhere but cant find out where.

So who can show me how to properly calculate the displacement of an engine?

[bmwman91]

(Number of Cylinders) x (Stroke Length mm) x 3.1415926535 x (Bore Diameter mm) x (Bore Diameter mm) / (4 x 1000000) = (Displacement in Liters)

[unevolved]

Yep. It's pretty simple. Stroke times your piston area (1/2 diameter squared, times Pi), multiplied by the number of cylinders.

[MF DOOM]

Thank you. I did it and must have done it right. Got 1.83. The guy I bought the motor from said it was a 2.0l and I was skeptical but couldnt figure it out.

[dnguyen1963]

(Number of Cylinders) x (Stroke Length mm) x 3.1415926535 x (Bore Diameter mm) x (Bore Diameter mm) / (4 x 1000000) = (Displacement in Liters)

Why not just Pi? You had to type all that out?

[MF DOOM]

he simplified it so i could get it.

<--- bad@math

[bmwman91]

Why not just Pi? You had to type all that out?

he simplified it so i could get it.

<--- bad@math

Most people approximate PI as 3.14. More decimalzzz = more horsepowerzzz.

And for the record I didn't type it all out. Windows Calc + "P" + "Ctrl+C" + "Ctrl+V".

[MF DOOM]

well whatever you did i figured it out. I had been getting numbers like 235783.2338

[bmwman91]

Conceptually, all you need to keep in mind is that you are calculating the volume of a cylinder. Height x area of the circle.

Compression...THAT'S a whole different animal. Then there's effective compression on top of that!

[dnguyen1963]

Most people approximate PI as 3.14. More decimalzzz = more horsepowerzzz.

And for the record I didn't type it all out. Windows Calc + "P" + "Ctrl+C" + "Ctrl+V".

You are missing a few digits...


3.141592653589793238462643383279502884197169399375 10
58209749445923078164062862089986280348253421170679
82148086513282306647093844609550582231725359408128
48111745028410270193852110555964462294895493038196
44288109756659334461284756482337867831652712019091
45648566923460348610454326648213393607260249141273
72458700660631558817488152092096282925409171536436
78925903600113305305488204665213841469519415116094
33057270365759591953092186117381932611793105118548
07446237996274956735188575272489122793818301194912
98336733624406566430860213949463952247371907021798
60943702770539217176293176752384674818467669405132
00056812714526356082778577134275778960917363717872
14684409012249534301465495853710507922796892589235
42019956112129021960864034418159813629774771309960
51870721134999999837297804995105973173281609631859
50244594553469083026425223082533446850352619311881
71010003137838752886587533208381420617177669147303
59825349042875546873115956286388235378759375195778
18577805321712268066130019278766111959092164201989 ...
:D:D:D:D

[MF DOOM]

Well do you know the equation for figuring out compression? and effective compression?

MATH PARTY THREAD

[bmwman91]

You are missing a few digits...


3.141592653589793238462643383279502884197169399375 10
58209749445923078164062862089986280348253421170679
82148086513282306647093844609550582231725359408128
48111745028410270193852110555964462294895493038196
44288109756659334461284756482337867831652712019091
45648566923460348610454326648213393607260249141273
72458700660631558817488152092096282925409171536436
78925903600113305305488204665213841469519415116094
33057270365759591953092186117381932611793105118548
07446237996274956735188575272489122793818301194912
98336733624406566430860213949463952247371907021798
60943702770539217176293176752384674818467669405132
00056812714526356082778577134275778960917363717872
14684409012249534301465495853710507922796892589235
42019956112129021960864034418159813629774771309960
51870721134999999837297804995105973173281609631859
50244594553469083026425223082533446850352619311881
71010003137838752886587533208381420617177669147303
59825349042875546873115956286388235378759375195778
18577805321712268066130019278766111959092164201989 ...
:D:D:D:D

Shit man, dem digitzzzzzzzzzzz.

Well do you know the equation for figuring out compression? and effective compression?

MATH PARTY THREAD

Eventually you do math to figure it out. First you need to know specifics about the geometry of the piston crown and head (combustion chamber volume when piston is at TDC) to get static compression, and then a map of volumetric efficiency to figure out effective compression at different RPMs. Generally speaking, effective compression is less than static compression for NA engines.

Static compression is just:
(Combustion chamber volume at BDC) / (Combustion chamber volume at TDC).
OR
(Combustion chamber volume at TDC + displacement of single cylinder) / (Combustion chamber volume at TDC).

Easy...just set cylinder 1 to TDC, pull the spark plug and see how much water goes in.*** :stupid:

***(for the love of god and all that is holy don't do this)

[sweet6e30]

if you have an iphone.... "gear toolkit" app.
pretty cool