[Diy_efi] MAF calibration

[Mike]

no, I think you are going up the wrong path to recal the MAF... :(

Why, because a 'properly' cal'd MAF tells you how much air the engine
is using, its up to the ECU mapping to handle the larger injectors,

Think of it this way, the less variables you need to handle/tamper
with in any control system then the greater chance the human mind
has to arrive at a viable and practical outcome (erazmus;)

I also have a turbo engine, its a 3L nissan straight 6 running
a garett T3 at around 10 to 10.5psi boost and the facttory MAF
can just handle the flow - which is above factory settings,

I have a remapped ROM in the ECU supplied by an Australian
company which is a short term measure but is much easier then
fiddling with the MAF curves,

I did however (in the early days) make a staged gain amp,
which for the 70% or so of normal (log) output the gain is
unity (1.0) but for the more flow the greater the gain
which effectively richens the mixture more then any ECU
mapping because the ECU is fooled into thinking the engine
is using more air then it really is and consequently the
pulse to the injectors is longer. However tests over some
2 years showed this used far more fuel then it should of
and needed frequent adjustment as the staged gain amp
was a simple analog amp with no secondary or tertiary
compensation factors,

If I wanted to turbo a factory engine, I'd get an
ECU that could be straightforwardly mapped for larger
injectors and handle a MAF with a larger throat *but*
I would definitely not adjust the MAF output, just change
*one* set of mapping in the ECU for the injectors,

Rgds

Mike



At 01:48 PM 16/8/2002 -0600, you wrote:
>Forgive me if this has been discussed before.  I'm a newbe here, but I have
>been searching for several days now with no success.  
>
>Here is what I'm doing:
>94 Ford 2.0L, EEC-IV ecm, with a MAF.  I'm going to turbo this engine.  
>I believe the trick to compensate for larger injectors is to recalibrate the
>MAF sensor.  Now, I'm a mechanical engineer, so changes to the ecm program
>are beyond me at this time.
>I calculate that I need 300cc/min injectors, this is 36% larger than the
>original 220cc.
>
>Question 1) Has there been any work done on a DIY MAF recalibration?
>
>Question 2) Is a change to the basic MAF size a viable alternative (see
>below) or is my logic flawed?
>	By doing some quick air flow calculations  CFM=(CID x RPM x .5 x
>Ev)/1728
>    Alternative 1, maximum air flow
>	I find that a MAF from a 3.8L (Taurus) should flow the required
>maximum 230cfm I need with a pressure ratio of 1.54 on the 2.0L.  However,
>at idle the cfm is 89% different (46.8cfm for the 3.8, and 24.7 for the
>2.0).
>    Alternative 2, idle CFM plus 36%
>	Solve for CID at idle plus 36% CFM (to compensate for increased
>injector size) is 	approximately 166CID (or 2.7L).
>
>Thanks for your help.
>
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>

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