Re: To bore, stroke, and breathe

[Hulda Jowett <hjowett@nasc.mass.edu>]

> 	I was talking to my cousin earlier who was talking to his friend who
> was talking...  Anyways, my cuz told me that VW made one head for the
> 1.8 and 2.0L blocks.  The 2.0 head can be modified for a healthy
> increase in hp.  However, the 1.8 cannot be ported because it is already
> factory ported to make up for the weak low-end.  Basically, because the
> 2.0 has the extra grunt over the 1.8, there was no need to port it out. 
> Is this true?  

I'm not quite sure I follow your statment? The 1.8l head flows 
significantly better than the 2.0l head  (the port is 11cc larger on the 
1.8). The 2.0l head (due to its smaller port) will have more velocity at 
low engine speeds, hence more torque on the low end). The 2.0l head can 
be ported out exactly the same as the 1.8, it just takes longer to do it, 
as there's more material to remove. Tell your cousins friend to stop 
talking out his butt, the 1.8l head responds to porting)

> 	I'm not sure I follow you.  Will the size of the piston affect the revs
> (i.e. higher redline?)  What's the original spec for the pistons?  

Generally, the shorter the stroke, the faster and higher the engine can 
rev. This is due to lower piston speeds. So yes, the size of the piston 
can affect the ability to rev higher, larger piston shorter stroke, more 
highend. Smaller piston, longer stroke, more low end.

> 
> 	You lost me again.  Is 50mm large?  I am still trying to figger out
> what's what with the engine components.  Thanks.

The stock 16V intake is 40mm in diameter, it was produced to help bolster 
low end performance on US cars.

So basicly, long stroke, small port small intake (high velocity at low 
speed) engines produce more lowend power, and have a lower rev range. 
Short stroke, large port (good velocity at high speeds) will make top end 
power, and rev higher.

Later,

Brian
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