[Diy_efi] Air/Fuel meter now working! And L-jetronic

[Adam Wade]

--- 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.

> But in theory, if plenum pressure changes, it must
> pump in air if plenum dimensions are not changing.

But all that air does not necessarily enter the
combustion chamber during the same cycle that it
enters the plenum, does it?  If it did, plenum
pressure would never change...  But it does, and
often, in a turbo app.

> Yeah, with turbos it is complicated, since they have
> "blow-off" too.

Why would that complicate anything, unless you were
not measuring pressure in the plenum?

> We need cylinder pressure sensor and direct
> injection.

Cylinder pressure sensing is done easily enough with
piezoelectric washers under the spark plugs.  Works
well enough for ignition timing that at least one
company is developing an ignition controller using
that as the only "timing" sensor.

DI has some advantages, but is not terribly cheap to
implement.  For best power use, I don't see much
advantage unless you're worrying about fuel economy at
the same time.

> Havn't you looked inside l-jetronic, they have many
> arrays of resistors.

I've never seen an array of resistors inside any
L-Jet.  Perhaps you can show me which ones correspond
to particular load/speed points?

I see some isolation resistors at the connectors here.
 Where are the arrays of resistors that constitute a
"map"?

<http://www.jagweb.com/jagworld/42efi/ecu_large.jpg>
<http://www.jagweb.com/jagworld/42efi/us_ecu_large.jpg>

There's a great shot of an ECU interior in "Gasoline
Fuel Injection System: L-Jetronic", from Bosch GmbH,
which also shows no "arrays of resistors".  I can scan
and host it if you'd like.

> We can call map inside the EPROM also a "rough
> approximation of a fueling curve". :)

No, we can't, since the main 2D maps correspond
directly to injector open times (although they may be
scaled by other sensors).

> OK, lets stop this :D

Yay.  I was starting to think it might never end...

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