Intake Runner Length

Jemison Richard JemisonR at tce.com
Wed Jan 27 21:57:01 GMT 1999


Tim,

Runner dia affects flow dynamics.  The larger the dia, the more air totally
will flow but the slower it will move and the slower the column of air in
the intake tube will react to changes in throttle position (causing lags in
response).  There is a formula for determining these runners but it escapes
me right now.  Check out Smith and Morrison's "Scientific Design of Intake
and Exhaust Systems).  This is in print and available through Amazon among
others.

rick

> -----Original Message-----
> From:	Van Setten, Tim (AZ75) [SMTP:Tim.Van.Setten at CAS.honeywell.com]
> Sent:	Wednesday, January 27, 1999 4:14 PM
> To:	'DIY-EFI'
> Subject:	Intake Runner Length
> 
> Hi All.  
> I've been reading your posts here for awhile and learned alot, but now
> it's
> time to ask for help.  We have been fuel injecting our sand rails here in
> the southwest now for about 10 years or so.  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.  
> Now we are playing around with the drive-ability issues.  We want to try
> different intake manifold combinations.  
> The question is: What size and length should the intake runners be and
> also
> what size should the intake plenum be?  Bruce Bowling's program addresses
> the length, but he left out the "diameter" of the runner and I have to
> believe that it will make a difference on how big it is.  Also, the
> relationship of the plenum, is it sized to the max rpm, or to engine
> displacement, or what?  Any comments would be very helpful.
> Tim 



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