need help with a definition

[Homemade WRX]

out of interest was reading tomei's comparison on the 4g63 and 4b11 and they used the term "slope ratio" in reference to the piston and connecting rod. Said it has a ratio of 3.34:1 and I can't figure out what they are referring to. Books, google and wikipedia searches later I can't find anyone who uses this term and seeing no math don't know what I might know the term as.

Anyone have a clue what they mean as "slope ratio"?
I do know the review was originally Japanese, so I'm wondering if something was lost in translation...?
Thanks.

[Homemade WRX]

out of interest was reading tomei's comparison on the 4g63 and 4b11 and they used the term "slope ratio" in reference to the piston and connecting rod. Said it has a ratio of 3.34:1 and I can't figure out what they are referring to. Books, google and wikipedia searches later I can't find anyone who uses this term and seeing no math don't know what I might know the term as.

Anyone have a clue what they mean as "slope ratio"?
I do know the review was originally Japanese, so I'm wondering if something was lost in translation...?
Thanks.

[BrendonD]

Could it mean the distance from the center of the crank to the center of the con-rod journal bearing over the distance from the center of the crank to the center of the wrist pin, when they make a right triangle with each other? That's the only thing I can think of, and the first place I could visualize that number

[Homemade WRX]

so your saying actual slope (rise/run).

with the 4b11 = 149.25mm rod and 86mm stroke
rise = (149.25^2-43^2)^.5 = 142.92mm
slope = 142.92/43 = 3.324

I get a different number regardless of how many places I carry in my calcs...but that is the ballpark.

Same calcs put my long rod at 3.445.
Thanks.

[BrendonD]

No problem, that was sort of a wild guess, but the only place I could find a number that was close.

Cheers,

[Homemade WRX]

got a little help from a friend on this one...
tan^-1(149.25/43) = 73.9*

sin (73.9) = .96078 = (149.25/Hyp)

.96078 (86/2) = 41.314

(149.25^2 - 41.314^2)^.5 = 143.418

143.418 / (86/2) = 3.3353 = 3.34

so, yeah it actually is a slope ratio...

[BrendonD]

It's kind of a weird number, but could be useful in determining comparative engine geometry, like if you want a shorter stroke compared to the amount of displacement or something for higher revs. I've busted out the pen and paper trying to visualize the calculations you just did... to no luck. Guess I'll have to take your word for it.

[Homemade WRX]

it is to help realize crank angle relations with thoughts towards cylinder pressure. the 41.314 is just the crank raduis reflected to the x-axis. If that is what was hanging you up. Also a quick comparison of force on piston skirt/cylinder wall.

[BrendonD]

Gotcha, glad we could figure this out!

[Homemade WRX]

well, it isn't figured out...I should say this is a best guess that could be figured...
it is slope ratio and does round to the desired outcome...so...?

I still can't get over all the views and no one else has any input.
lol