Intake Runner Length

[Van Setten, Tim (AZ75)]

> Subject: Intake Runner Length
> 
> 
> 
> What for ecm?.
> 
	We ended up conjuring our own.  (Mainly by swiping circuits out of
every known ecm in the free world).  We wanted a box with knobs on it that
controls the basic fuel curve.  It's not a good idea to take a lap top out
into the sand dunes to change the fuel curve.
>  We want to try
> >different intake manifold combinations.
> 
> 
> For plenum, start at engine displacement, and going as high as 2x
> displacement wouldn't be a worry, as long as it worked.
> When I can I build the plenum, so I can add layers of spacers.
> I'd also, do that for runner lengths if I were you.
> Now, the runner diameters is a real nasty issue, ie lots of possibles.
> Stock Car Racing Mag several years ago had an article about them
> as I recall.
>   With a VW head aren't you rather limited in port diameter?.
> Bruce
> 
	Actually not, the after-market heads can get quite large.  I have
actually seen some valves that looked as big a Coke can.

	I made a trip to our local pick-n-pull junk yard here in Phx, and I
haven't done the numbers yet, but the average runner length is about  17
inches, and the plenums are about the same as engine displacement.  Here is
where it gets interesting:  The average daily driver car has round runners
about 1 1/4 or so in dia.  The go-fast cars (Ford Mustang 5.0, Honda V-tek,
etc.) usually have square or rectangle runners.  And the drag racers say the
"trick" runner shape should be like the letter "D".  I didn't expect so many
variations!
	Thanks for all the inputs.....Tim.