Intake Runner Length

[Greg Hermann]

>-----Original Message-----
>From: Van Setten, Tim (AZ75) <Tim.Van.Setten at CAS.honeywell.com>
>To: 'DIY-EFI' <diy_efi at efi332.eng.ohio-state.edu>
>Date: Wednesday, January 27, 1999 4:30 PM
>Subject: Intake Runner Length
>
>
> We are using a speed density
>>system and also a dual-fuel setup.  We turbo charge our little girlie
>2300cc
>>VW's in a 900 lb car and head to the sand dunes.  The dual fuel is
>>accomplished by adding a second set of injectors and injecting methanol
>only
>>under boost.  This makes these air-cooled engines very happy and stops all
>>of the pinging problems etc. associated with 15 lbs of boost.
>
>What for ecm?.
>
> 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 lenghts 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

IIRC, at least for a hemi head and a round port, David Vizard used to say
0.9 times the diameter of the intake valve head was about right for the
port , throttle, stack, & everything. For a somewhat shrouded valve, and
less efficient port, my guess would be that something less than that would
work best---

Just my $.02

Regards, Greg