[Diy_efi] New project

[Dennis Noordsij]

> I kind of though the SD using MAP+RPM would mostly eliminate the need for
> VE tables, might as well go with Alpha-N then?

Ok .. thought some more about this, and I didn't make sense :-) Full load=20
would have MAP =3D=3D ambient pressure, with lots of air flowing, but I wou=
ldn't=20
be able to detect any of it with the method I described.=20

But, given the following:

> Boat only has one forward gear, is always propped to reach max RPM and no
> more at WOT, never goes uphill, never goes downhill, and is always under
> load (though, because of the different curves of engine power and power
> needed to rotate the prop, cruise RPM allows the engine to run at 50-60% =
of
> throttle only).

How about, a control box with several dials, one for idle, then one for eve=
ry=20
500RPM increment, up to 4000 RPM, with one final one for WOT (about 4200 RP=
M,=20
depending on prop pitch).

Every dial would control the VE factor for that RPM, with linear interpolat=
ion=20
between different "bins". Say between 75 and 100% (assuming the real value=
=20
will always lie somewhere inbetween).

The ECU will take this VE setting, and aim for a 14.7:1 A/F ratio, using an=
=20
Alpha-N setup. Weather conditions will be compensated for so you never need=
=20
to re-tune when it's suddenly cold or warm outside.

Say you are are at 3000 RPM, if you set the dial to the actual real VE valu=
e=20
you'd have a 14.7:1 ratio, if you set it higher it'll be leaner, if you set=
=20
it lower it'll be richer.

So you are not able to directly adjust the mixture (say a dial from 11:1 to=
=20
15:1) but are indirectly able to do so by adjusting the VE.=20

Then, you set all VE's to 100% (very rich :), and start tuning the individu=
al=20
bins. While cruising, lean out until it starts to miss, under load, lean ou=
t=20
until it starts to explode :P

Possibly with a borrowed exhaust analyzer or other means of verifying you'r=
e=20
in the right ballpark.

Once it's tuned you can leave it at that. PE, cold start enrichment, cranki=
ng=20
enrichtment, etc, are also set until satisfactory. It also means I don't ha=
ve=20
to come out with a laptop every time someone wants to fiddle with it :) Jus=
t=20
turn the knobs at your own risk :P

On a car this would probably not work so well because you'd need to tune fo=
r=20
every gear, but on a boat this might be enough.

It anyway sounds like this would be straightforward enough for a first=20
attempt, with possibly ventures into the MAP sensor readings later. It'd be=
=20
nice to get SOMETHING to work first :)


Can it get simpler and more straightforward than this?

and

Should ease of tuning be on par with SD/MAF based setups

and

Should the results be similar? :)

Many many thanks,=20
Cheers,
Dennis

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