Re: stroker cranks

[Dan Bubb <jdbubb@ix.netcom.com>]

There is no doubt that stroking a VW engine without changing rod length
or piston pin height will NOT work. The piston comes within .040" of the
head on an 8V engine. Accounting for rod and piston stretch at 6500 RPM
will take  this down to about ZERO. Having a minimal piston to head
clearance is generally a good idea if your combustion chamber has squish
bands (and both 8V and 16V do) or the squish bands will not work to
promote turbulence.
So, you will have to get shorter rods (standard length is 146 I believe,
so length would need to be 144.65) and make sure the bottom of the
piston clears the counterweights at BDC, or raise the pin height in the
piston by 1.35mm. With no changes in deck clearance or piston crown
shape and assuming the CR is 10.8 stock, the CR strictly due to change
in displacement will be 11.1.
Dan

"Fry, Larry" wrote:
> 
> Jonathon's method is the most correct.  Potterman's doesn't factor in number
> of cylinders, so you couldn't use it universally.
> And, yes, Scott, stroking an other-wise-unchanged engine will most
> definately increase the compression ratio, probably to right up there with
> the diesels IF, IF, IF the pistons don't hit the head.
> 
> Larry  sandiego16V
> 
> -----Original Message-----
> From: Jonathan Pack [mailto:pack.39@osu.edu]
> Sent: Wednesday, November 07, 2001 9:36 PM
> To: Randy B; Scott F. Williams
> Cc: scirocco-l@scirocco.org
> Subject: Re: stroker cranks
> 
> First, I would be afraid of piston-to-head interference.  The stock pistons
> come all the way to the top of the cylinders with 92.8 stroke.  Once they go
> 1.15mm farther...I don't know.
> 
> Second, this would substantially increase CR.  If you know chamber size and
> the volume of the cutouts for the valves on the pistons, you can calculate
> how much defference it will make.
> 
> Third, the formula for volume of a cylinder is pi*h*r^2.  In engine terms,
> this means pi*stroke*(bore/2)^2 is displacement of each cylinder in mm^3.
> Divide that by 1000 to get displacement in cm^3.  Multiply by number of
> cylinders and you've got it.  Somebody else posted a formula that squared
> bore (diameter) instead of (bore/2), which is the radius, and what you
> square to find area of a circle.
> 
> Fourth, TDI cranks are pretty spendy.  Kudos to you if you have the money to
> buy one.
> 
> Jonathan
>

--
Email LIST problems to: scirocco-l-probs@scirocco.org.
To unsubscibe send "unsubscribe scirocco-l" in the message to majordomo@scirocco.org