[Diy_efi] Re: Diy_efi Digest, Vol 4, Issue 30

[Bill Washington]

Gents, By my understanding the VAF opening angle should be proportional 
to the pressure differential across the vane, and the pressure 
differential should be proportional the the Mass Flow - which is the 
information required - yes the VAF is a bit crude, and the resistive 
film wears away so they are far from ideal with a limited lifetime but 
when they are working I believe they do measure the mass flow. Then the 
O2 sensor can correct for the inaccuracies.... The Hot wire Mass flow 
meter (LH Jet) is a refinement which overcomes most of these issues. 
Does this sound fair comment? Bill Message: 3 Date: Thu, 16 Jun 2005 
20:03:16 -0700 (PDT) From: Adam Wade <espresso_doppio at yahoo.com> 
Subject: Re: [Diy_efi] Air/Fuel meter now working! And L-jetronic To: 
diy_efi at diy-efi.org Message-ID: 
<20050617030316.37128.qmail at web32201.mail.mud.yahoo.com> Content-Type: 
text/plain; charset=iso-8859-1 --- Astrona <amdcpu at hot.ee> wrote:

>> If something is pushed back, it restricts also the
>> flow.
>  
>

But it is not subtracted from what was measured
flowing through, and therefore the mixture will be
over-rich on subsequent injector events under the same
or similar conditions.


>> Most of todays systems doesn't measure these things.
>  
>

That's because most of today's systems already have
the engine's behavior due to intake, cam, and exhaust
design considerations knitted into the maps.  This is
why you need to change maps if you change cam profile
or timing, or modify the intake or exhaust so as to
have a signficantly different behavior from stock. 
I'd have to argue that replacing the entire exhaust
and intake systems with a turbo setup would qualify.


>>>> How could you determine how much air was entering
>>>> the cylinder if you're measuring air entering the
>>>> plenum?  If air pressure in the plenum never
>>>> changed, this MIGHT work, but if pressure in the
>>>> plenum changes (especially if it changes quickly,
>>>> which is common on turbo apps), it CAN'T work
>>>> properly (unless you add a plenum air pressure
>>>> reading somewhere, in which case why bother with a
>>>> VAF?)
>>    
>>

>> I agree, should just use MAP.
>  
>

So you've circled around.  You said the L-Jet system
should be fine for this application, and now you're
saying that it is insufficient, as I've been
suggesting all along.


>  
>
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