RE: Ugh

Longer connecting rods DO increase compression, but they
reduce displacement.  Maybe some ascii art will help:
                       ___         ___
Combustion chamber ___|   |___ ___|   |___
                      |   |       |___|  Piston up
                      |   |       | | |
                      |   |       | | |
                      |   |       | | |
                      |___|       | | |
         Piston down  | | |       | | |

(Assume that the diameter of everything is constant)
Swept area of piston = 4
Compbustion Chamber with piston up = 2
Compression ratio = 4:2 or 2:1
Displacement (Piston Sweep + Combustion Chamber) = 6

Longer conrod moves "stroke" of piston higher (as you
noted):
                       ___         ___
Combustion chamber ___|   |___ ___|___|___
                      |   |       | | |  Piston up
                      |   |       | | |
                      |   |       | | |
                      |___|       | | |
                      | | |       | | |
         Piston down  | | |       | | |

Swept area of piston (still) = 4
Compbustion Chamber with piston up = 1
Compression ratio = 4:1
Displacement (Piston Sweep + Combustion Chamber) = 5

Now, nobody increases the conrod length by 1/4 of the
stroke, but you get the idea...

A longer crank journal (with the same conrod) increases both
compression AND displacement (sweep of the piston goes lower
down AND comes higher up).  That is why "stroker"
crankshafts are usually supplied with matching conrods (a
touch shorter than stock to keep the compression from
becoming insane).

>
> I don't think longer rods will give you more compression
> -- they'll just move your exact same compression stroke
> higher in the cylinder.  For higher compression, you need
> to change the crank to get the pistons to travel farther.
> Right?
> --
> Chris Eck
> 59 Bugeye

///  unsubscribe/change address requests to majordomo@autox.team.net  or try
///  http://www.team.net/mailman/listinfo
///  Archives at http://www.team.net/archive/spridgets