Custom MAF system: help w/ calculations

[Shirley, Mark R]

VE is a percentage.  It's calculated on the cylinder volume as the divisor.
So,   amount of air inducted into cylinder / cylinder volume = VE%
Typical NA engines run 85-90% at peak torque/load.  Less than that at
lower loads and different rpms.  Also, highest VE conforms to the lowest
BSFC
values.
Most MAF cars I have seen the tables for, they still had VE tables to
compare to,
in case the MAF sensor readings go wonky.  Newer systems are starting to
model the
engine in software, calculating on the fly what the airflow is from sensor
data.
I saw a demonstration of this on a new controller from Econtrols in San
Antonio, 
just before I left my former employer.  The difference between the two
engines
running characteristics was night and day.

-----Original Message-----
From: Pat Ford [mailto:pford at qnx.com]
Sent: Wednesday, January 24, 2001 10:45 AM
To: diy_efi at diy-efi.org
Subject: Re: Custom MAF system: help w/ calculations


?? isn't VE the measure of actual airflow ( which is also what the maf
does)?  

Previously, you (John Dammeyer) wrote:
{ Hi,
{ 
{ My guess is the MAF systems still use some sort of Volumetric Efficiency
{ table or else you could use a percentage of intake valve open time since
you
{ already have the flow rate.  If you work it backwards you can see that
{ sampling the MAF rapidly over the period of time that the intake is open
{ will give you a series of mass air readings that summed probably come
close
{ to the mass of air in the cylinder.

 I think that the mafs are slow reading so they tend to average the airflow
over  time. 

{ 
{ Cheers,
{ 
{ John
{ 
{ ----- Original Message -----
{ From: <james.drysdale at utoronto.ca>
{ To: <diy_efi at diy-efi.org>
{ Sent: Tuesday, January 23, 2001 5:14 PM
{ Subject: Re: Custom MAF system: help w/ calculations
{ 
{ 
{ >
{ > > Good luck with your endeavor.  Welcome here.  I won't say much about
{ > > UofT, other than to say I hail from Queen's, 'nuff said :)......
{ >
{ > Queens...was my second choice. Really. :)

 bad choice Queens rules!!



--
Pat Ford                           email: pford at qnx.com
QNX Software Systems, Ltd.           WWW: http://www.qnx.com
(613) 591-0931      (voice)         mail: 175 Terence Matthews          
(613) 591-3579      (fax)                 Kanata, Ontario, Canada K2M 1W8

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